JP7707057B2 - SUBSTRATE PROCESSING METHOD AND SUBSTRATE PROCESSING APPARATUS - Google Patents

Description

This application relates to a substrate processing method and a substrate processing apparatus.

In the manufacturing process of semiconductor devices, resist is sometimes used as a mask to selectively etch or implant ions on the main surface of the substrate. After etching or ion implantation is completed, the resist is no longer needed, so a process is carried out to peel it off (remove it).

Various methods for stripping resist provided on a substrate have been proposed. For example, Patent Document 1 discloses a method for stripping resist provided on a substrate by supplying a mixed liquid (SPM liquid) of sulfuric acid and hydrogen peroxide solution to the substrate and utilizing the oxidizing power of Caro's acid (peroxomonosulfuric acid: H ₂ SO ₅ ) generated by the reaction between the sulfuric acid and the hydrogen peroxide solution.

In this method, it is necessary to continue to supply new SPM liquid to the substrate in order to progress the resist peeling. Specifically, as described in Patent Document 1, for example, the substrate is rotated to shake off the old SPM liquid used in resist peeling from the substrate, while new SPM liquid is continuously supplied onto the substrate, thereby progressing the resist peeling. For this reason, it has been difficult to reduce the amount of sulfuric acid used in the method of resist peeling using SPM liquid.

JP 2019-176125 A

In recent years, as environmental awareness has increased, there is a strong demand to reduce the amount of sulfuric acid used, which is a chemical that places a large burden on the environment. As a result, as an alternative to the method using SPM liquid, a method has been considered in which a liquid film of an acidic processing liquid such as sulfuric acid is formed on a substrate, and the liquid film is irradiated with plasma. In this method, the resist is peeled off by oxidizing the resist with active species in the plasma, Caro's acid generated by the reaction of the active species with the liquid film, and the like. In this method, there is no need to continue to supply new sulfuric acid to the substrate to progress the peeling of the resist. Therefore, it is possible to reduce the amount of processing liquid such as sulfuric acid used compared to the method using SPM liquid.

However, while the above method has the advantage of reducing the amount of processing liquid used, it has been found to have a problem in that particles are easily generated on the substrate after processing.

The reason for this is believed to be as follows. In other words, in the above method, after a liquid film of, for example, sulfuric acid is formed on the substrate, the substrate is irradiated with plasma while the liquid film is maintained in a puddle state on the substrate, and the resist peeling proceeds. As a result, the peeled resist dissolves one after another into the liquid film held on the substrate. Therefore, at the stage where the resist peeling process is completed after a predetermined period of plasma irradiation, almost the entire amount of the peeled resist has dissolved in the liquid film on the substrate.

After the resist stripping process is completed, the liquid film on the substrate is washed away with a rinsing liquid. In this process, for example, if pure water as a rinsing liquid is supplied to the sulfuric acid liquid film, the pH value of the liquid film rises suddenly, and the solubility of the liquid film in which the resist is dissolved (i.e., the liquid film as a resist dissolving liquid) decreases. As a result, the resist that cannot be completely dissolved precipitates (re-precipitates) (the so-called pH shock). It is thought that particles are generated when the precipitated resist adheres to the substrate.

This phenomenon is unlikely to occur when the resist is stripped using SPM liquid. That is, when SPM liquid is used, as described above, the old SPM liquid is shaken off from the substrate while new SPM liquid is continuously supplied onto the substrate, thereby progressing the stripping of the resist. Therefore, the stripped resist is shaken off one after another together with the old SPM liquid and discharged from the substrate, and at the end of the stripping process, the SPM liquid shaken off from the substrate contains almost no contaminants such as the stripped resist. Therefore, it is considered that there is almost no stripped resist remaining on the substrate at the stage when the stripping process is completed. For this reason, even if pure water is supplied to the substrate as a rinse liquid after the stripping process is completed, the possibility of the resist being precipitated is low. Therefore, the phenomenon of the precipitated resist adhering to the substrate is unlikely to occur.

In this way, when resist is stripped using a method of irradiating a liquid film with plasma, it is necessary to solve a problem that does not occur when using an SPM liquid, namely, the tendency for particles to be generated on the processed substrate.

This application was made in consideration of these problems, and its purpose is to provide a technology that can suppress the generation of particles when removing resist using a method of irradiating a liquid film with plasma.

A first aspect is a substrate processing method comprising: a liquid film formation step of supplying an acidic processing liquid to a substrate having a resist thereon to form a liquid film of the processing liquid; a plasma processing step of irradiating plasma onto the substrate holding the liquid film to proceed with a resist stripping process; and a rinsing step of bringing a rinsing liquid into contact with the substrate after the stripping process is completed, the rinsing liquid being adapted to keep a change in solubility of the resist dissolved in the liquid film within an allowable range that does not cause precipitation of the resist . The rinsing liquid is an acidic liquid whose pH difference with the liquid film is equal to or less than a maximum allowable pH difference, thereby keeping the change in solubility within the allowable range.

A second aspect is the substrate processing method according to the first aspect, wherein the rinse liquid has a pH difference of 2 or less between the rinse liquid and the liquid film.

A third aspect is the substrate processing method according to the first or second aspect, wherein the rinsing liquid and the processing liquid are both sulfuric acid.

A fourth aspect is the substrate processing method according to the third aspect, wherein the rinsing liquid and the processing liquid are sulfuric acid having the same concentration.

A fifth aspect is the substrate processing method according to any one of the first to fourth aspects, in which the rinsing liquid is heated before being brought into contact with the substrate.

A sixth aspect is a substrate processing method according to any one of the first to fifth aspects, wherein in the rinsing step, the rinsing liquid is ejected from a nozzle toward the substrate while the substrate is rotated at a rotation speed which is increased stepwise.

A seventh aspect is the substrate processing method according to any one of the first to fifth aspects, wherein in the rinsing step, the substrate is immersed in a storage tank that stores the rinsing liquid.

An eighth aspect is a substrate processing apparatus comprising: a holding section for holding a substrate; a liquid supply section for supplying a liquid to the substrate held by the holding section; a plasma irradiation section for irradiating the substrate held by the holding section with plasma; and a control section for controlling the holding section, the liquid supply section, and the plasma irradiation section, wherein the control section causes the holding section to hold a substrate having a resist provided thereon; causes the liquid supply section to supply an acidic processing liquid to the substrate to form a liquid film of the processing liquid; causes the plasma irradiation section to irradiate plasma to the substrate holding the liquid film to proceed with a resist stripping process; causes the liquid supply section to supply a rinsing liquid to the substrate after the stripping process is completed, the rinsing liquid being such that a change in solubility of the resist dissolved in the liquid film falls within an allowable range in which the resist is not precipitated ; and uses an acidic liquid as the rinsing liquid whose pH value difference with the liquid film is equal to or less than a maximum allowable pH difference, thereby causing the change in solubility to fall within the allowable range.

According to the substrate processing method of the first aspect, a rinse liquid is brought into contact with the substrate after the resist stripping process is completed, and the liquid film in which the stripped resist is dissolved is washed off from the substrate. Here, the rinse liquid limits the change in solubility of the resist dissolved in the liquid film to an allowable range that does not cause resist to precipitate. In other words, even when the rinse liquid comes into contact with the substrate, the solubility changes only within an allowable range that does not cause resist to precipitate. Therefore, the precipitation of the resist is not induced by the rinse liquid coming into contact with the substrate. This suppresses the generation of particles on the substrate after processing.

Furthermore, according to the substrate processing method of the first aspect, a rinse liquid is selected using the pH value as an index, so that a rinse liquid that can keep the change in solubility when the rinse liquid comes into contact with the substrate within an acceptable range can be easily and appropriately selected.

According to the substrate processing method of the second aspect, it is possible to make the change in solubility when the rinse liquid comes into contact with the substrate sufficiently small, and thus it is possible to sufficiently suppress the generation of particles.

According to the substrate processing method of the third aspect, since the rinsing liquid and the processing liquid are both sulfuric acid, the piping system required for supplying the liquids is simplified compared to the case where different types of liquids are used for each liquid.

According to the substrate processing method of the fourth aspect, since the rinsing liquid and the processing liquid are sulfuric acid having the same concentration, there is almost no change in pH value when the rinsing liquid comes into contact with the liquid film, and therefore it is possible to make the change in solubility when the rinsing liquid comes into contact with the liquid film particularly small, and it is possible to sufficiently suppress the generation of particles.

According to the substrate processing method of the fifth aspect, the rinse liquid is heated before it is brought into contact with the substrate, so that even when the rinse liquid is brought into contact with a liquid film heated by plasma irradiation, the temperature change range is kept sufficiently small. That is, both the pH change range and the temperature change range are kept small. Therefore, it is possible to make the solubility change range when the rinse liquid is brought into contact with the substrate particularly small, and the generation of particles can be particularly sufficiently suppressed.

According to the substrate processing method of the sixth aspect, in the rinsing step, the substrate is rotated while the rotation speed is increased stepwise while the rinsing liquid is discharged from the nozzle toward the substrate. If the rotation speed is increased all at once instead of stepwise, the speed at which the liquid is supplied to the substrate cannot keep up with the speed at which the liquid is discharged from the substrate, and an air-liquid interface may appear on the substrate, resulting in an exposed portion that is not covered by the liquid. Particles and the like are likely to adhere to such portions, and the cleanliness of the substrate is likely to decrease. According to the above configuration in which the rotation speed is increased stepwise, such an air-liquid interface is unlikely to appear on the substrate, and therefore the cleanliness of the substrate is unlikely to decrease. In other words, the liquid film in which the peeled resist is dissolved can be replaced with the rinsing liquid without decreasing the cleanliness of the substrate.

According to the substrate processing method of the seventh aspect, in the rinsing step, the substrate is immersed in a storage tank that stores a rinsing liquid, so that the liquid film in which the peeled resist is dissolved can be quickly drained from the substrate and replaced with the rinsing liquid.

According to the substrate processing apparatus of the eighth aspect, a rinse liquid is supplied to the substrate after the resist stripping process is completed, and the rinse liquid is brought into contact with the substrate, thereby washing away the liquid film in which the stripped resist is dissolved from the substrate. Here, the rinse liquid is adapted to keep the change in solubility of the resist dissolved in the liquid film within an allowable range in which the resist is not precipitated. In other words, even when the rinse liquid is brought into contact with the substrate, the solubility changes only within an allowable range in which the resist is not precipitated. Therefore, the precipitation of the resist is not induced by the contact of the rinse liquid with the substrate. Therefore, the generation of particles on the substrate after the process is suppressed.

1 is a plan view illustrating a schematic configuration of a substrate processing system. FIG. 2 is a block diagram showing a configuration of a control unit. FIG. 2 is a side view illustrating a schematic configuration of a processing unit according to the first embodiment. 1A and 1B are a side cross-sectional view and a plan view showing a schematic configuration of a plasma reactor. FIG. 2 is a diagram showing a flow of processing executed in a processing unit. FIG. 13 is a diagram for explaining a holding step. FIG. 13 is a diagram for explaining a liquid film forming process. FIG. 1 is a diagram for explaining a plasma treatment. FIG. 11 is a diagram for explaining a first rinsing step. FIG. 11 is a diagram for explaining a second rinsing step. FIG. 1 is a diagram showing a schematic diagram of the relationship between the maximum allowable pH difference and the temperature difference. FIG. 13 is a diagram for explaining a process flow relating to a rinsing step. 11 is a photomicrograph showing the state of a substrate after processing when the same sulfuric acid as the processing liquid is used as the first rinsing liquid. FIG. 10 is a diagram illustrating a relationship between a maximum allowable temperature difference and a difference in pH value. FIG. 11 is a side view illustrating a schematic configuration of a processing unit according to a second embodiment. FIG. 13 is a side view showing a schematic configuration of an immersion unit according to a third embodiment. FIG. 13 is a diagram showing a process flow relating to a rinsing step. 11 is a micrograph showing the state of a substrate after processing when the same sulfuric acid as the processing liquid is used as the rinsing liquid. FIG. 13 is a side view illustrating a schematic configuration of a processing unit according to a modified example. 1 is a micrograph showing the state of a substrate after processing when pure water is used as a rinsing liquid. 11 is a micrograph showing the state of a substrate after processing when IPA is used as a rinsing liquid.

The following describes the embodiments with reference to the attached drawings. Note that the components described in the embodiments are merely examples and are not intended to limit the scope of the present disclosure. In addition, in the drawings, the dimensions or numbers of each part may be exaggerated or simplified as necessary for ease of understanding.

Unless otherwise specified, expressions showing relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) not only strictly express the positional relationship, but also express a state in which the two are displaced relatively in terms of angle or distance within a range in which a tolerance or similar function is obtained. Furthermore, expressions showing an equal state (e.g., "same," "equal," "homogeneous," etc.) not only strictly express a quantitatively equal state, but also express a state in which there is a difference in which a tolerance or similar function is obtained, unless otherwise specified. Furthermore, expressions showing a shape (e.g., "circular," "square," "cylindrical," etc.) not only strictly express the shape geometrically, but also express a shape within a range in which a similar effect is obtained, and may have, for example, irregularities or chamfers. Furthermore, each expression such as "comprises," "has," "equips," "includes," and "has" is not an exclusive expression that excludes the existence of other components. Additionally, the expression "at least one of A, B, and C" includes "only A," "only B," "only C," "any two of A, B, and C," and "all of A, B, and C."

1. First embodiment
<1-1. Overall configuration of substrate processing system>
The configuration of the substrate processing system 100 will be described with reference to Fig. 1. Fig. 1 is a plan view showing a schematic configuration of the substrate processing system 100.

The substrate processing system 100 is a processing system that performs a predetermined process on a substrate W to be processed, and includes an interface section 110, an indexer section 120, a main body section 130, and a control section 140. The substrate W to be processed in the substrate processing system 100 is, for example, a semiconductor substrate. The shape of the substrate W to be processed is, for example, a disk shape, and its size (diameter) is, for example, approximately 300 (mm).

The interface unit 110 is an interface for connecting a carrier C, which is a substrate container that stores multiple substrates W, to the substrate processing system 100, and specifically includes, for example, a configuration in which multiple load ports 111 (three in the illustrated example) on which the carriers C are placed are arranged in a horizontal row. The carrier C may be of a type that stores the substrates W in an enclosed space (e.g., a FOUP (Front Opening Unified Pod), a SMIF (Standard Mechanical Interface) pod, etc.), or of a type that exposes the substrates W to the outside air (e.g., an OC (Open Cassette), etc.).

The indexer unit 120 is a part located between the interface unit 110 and the main body unit 130, and is equipped with an indexer robot 121.

The indexer robot 121 is a transport robot that transports substrates W between a carrier C placed on each load port 111 and a main transport robot 131 (described later), and is configured to include a hand 121a that holds the substrate W, an arm 121b connected to the hand 121a, and a drive unit for extending, revolving, and raising and lowering the arm 121b. The indexer robot 121 accesses the carrier C placed on each load port 111 to perform an unloading operation (i.e., an operation of removing an unprocessed substrate W contained in the carrier C with the hand 121a) and a loading operation (i.e., an operation of loading a processed substrate W held by the hand 121a into the carrier C). The indexer robot 121 also accesses a transfer position T with the main transport robot 131 to transfer substrates W between the indexer robot 121 and the main transport robot 131.

The main body 130 includes a main transport robot 131 and multiple (e.g., 12) processing units 132. Here, for example, multiple (e.g., three) processing units 132 stacked vertically form one tower, and multiple (e.g., four) towers are provided surrounding the main transport robot 131.

The main transport robot 131 is a transport robot that transports substrates W between the indexer robot 121 and each processing unit 132, and is configured to include a hand 131a that holds the substrate W, an arm 131b connected to the hand 131a, and a drive unit for extending, revolving, and raising and lowering the arm 131b. The main transport robot 131 accesses each processing unit 132 to perform a loading operation (i.e., an operation of loading the substrate W to be processed that is held by the hand 131a into the processing unit 132) and a unloading operation (i.e., an operation of removing the processed substrate W that is accommodated in the processing unit 132 with the hand 131a). The main transport robot 131 also accesses a transfer position T with the indexer robot 121 to transfer the substrate W to and from the indexer robot 121.

The processing unit 132 is a device that performs a predetermined process on the substrate W. The specific configuration of the processing unit 132 will be described later.

The control unit 140 is an element that controls the operation of each part of the substrate processing system 100, and is configured, for example, by a general computer having an electric circuit. Specifically, for example, as shown in FIG. 2, the control unit 140 includes a CPU (Central Processor Unit) 141 as a central processing unit that handles data processing, a ROM (Read Only Memory) 142 in which basic programs and the like are stored, a RAM (Random Access Memory) 143 used as a working area when the CPU 141 performs a predetermined process (data processing), a storage device 144 configured of a non-volatile storage device such as a flash memory or a hard disk device, and a bus line 145 that connects these together. A program P that defines the process to be executed by the control unit 140 is stored in the storage device 144, and the control unit 140 can execute the process defined by the program P by the CPU 141 executing this program P. However, part or all of the process executed by the control unit 140 may be executed by hardware such as a dedicated logic circuit.

The control unit 140 may be configured such that a main control unit that controls the overall operation of the substrate processing system 100 is communicatively connected to a plurality of local control units. In this case, at least one local control unit may be associated with each of the plurality of processing units 132, and the local control unit may control the operation of the corresponding processing unit 132 based on instructions from the main control unit. Furthermore, when such a configuration is adopted, each of the main control unit and each of the local control units may be individually equipped with some or all of the above-mentioned units 141 to 145.

<1-2. Processing unit>
Next, the configuration of the processing unit 132 will be described with reference to Fig. 3. Fig. 3 is a side view showing a schematic configuration of the processing unit 132. As described above, the main body 130 is provided with a plurality of processing units 132, and it is sufficient that at least one of the plurality of processing units 132 has the configuration described below. In other words, the plurality of processing units 132 may include one having a configuration different from that described below.

The processing unit 132 is, for example, a processing device that performs a process to strip (remove) resist provided on the substrate W, and corresponds to a substrate processing device. The processing unit 132 is a so-called single-wafer processing device that processes the substrates W to be processed one by one.

The processing unit 132 comprises a holding section 1, a liquid supply section 2, a plasma generating section 3, and a guard section 4. The processing unit 132 also comprises a chamber 5 that houses at least some of the elements comprised by each of these sections 1 to 4 (e.g., the base section 11, the nozzles 21a and 21b, the plasma reactor 31, the guard 41, etc.). In the internal space of the chamber 5, a downflow of clean air is formed by a fan filter unit 51, etc.

(Holding part 1)
The holder 1 is an element that holds a substrate W to be processed, and includes, for example, a base portion 11 , a plurality of chuck pins 12 , and a rotation mechanism 13 .

The base portion 11 is a disk-shaped member with a diameter slightly larger than the substrate W, and is arranged in a position such that the thickness direction is aligned along the vertical direction. A plurality of chuck pins 12 are provided on the upper surface of the base portion 11, and are arranged at intervals along the periphery of the upper surface. Each chuck pin 12 is configured to displace between a chuck position in contact with the periphery of the substrate W and a release position away from the periphery of the substrate W in response to instructions from the control unit 140, and by arranging each chuck pin 12 in the chuck position, the substrate W is held above the base portion 11 in a horizontal position (a position in which the thickness direction of the substrate W is aligned along the vertical direction).

The rotation mechanism 13 is a mechanism for rotating the base part 11. Specifically, the rotation mechanism 13 includes, for example, a shaft 13a connected at its upper end to the lower surface of the base part 11, and a motor 13b connected to the lower end of the shaft 13a. Here, for example, an axis that is perpendicular to the main surface of the substrate W held on the base part 11 and passes through the center of the main surface is defined as the rotation axis Q, and the shaft 13a is provided coaxially with this rotation axis Q. Then, in response to an instruction from the control part 140, the motor 13b rotates the shaft 13a around the rotation axis Q at the number of rotations instructed by the control part 140. The shaft 13a is rotated by being driven by the motor 13b, so that the base part 11, and therefore the substrate W held on the base part 11, rotate around this rotation axis Q. In this way, the holding part 1 including the rotation mechanism 13 (i.e., the holding part 1 that can rotate the substrate W while holding it) is also called a spin chuck or the like. The base portion 11 of the spin chuck is also called the spin base.

(Liquid supply section 2)
The liquid supply unit 2 is an element that supplies liquid to the substrate W held on the holder 1, and includes, for example, two nozzles (a sulfuric acid nozzle 21a and a pure water nozzle 21b) and a nozzle moving mechanism 22.

The sulfuric acid nozzle 21a is a nozzle that ejects sulfuric acid toward the substrate W held by the holder 1, and is specifically, for example, a straight nozzle with an ejection port 210a formed on one end surface. The sulfuric acid nozzle 21a is connected to a sulfuric acid supply unit 20a that supplies sulfuric acid to the sulfuric acid nozzle 21a. Specifically, the sulfuric acid supply unit 20a includes, for example, a supply pipe 201a whose one end is connected to the sulfuric acid nozzle 21a, and a sulfuric acid supply source 202a connected to the other end of the supply pipe 201a. The sulfuric acid supply source 202a includes a sulfuric acid tank that stores sulfuric acid. In addition, a valve 203a and a flow rate adjustment unit 204a are interposed in the supply pipe 201a. The valve 203a is a valve that switches between supplying and stopping sulfuric acid through the supply pipe 201a, and is controlled by the control unit 140. The flow rate adjustment unit 204a is, for example, a mass flow controller, and adjusts the flow rate of sulfuric acid flowing through the supply pipe 201a under the control of the control unit 140. In this configuration, when the valve 203a is opened, sulfuric acid at a predetermined flow rate adjusted by the flow rate adjustment unit 204a is supplied from the sulfuric acid supply source 202a through the supply pipe 201a to the sulfuric acid nozzle 21a and discharged from the discharge port 210a.

The pure water nozzle 21b is a nozzle that ejects pure water toward the substrate W held by the holder 1, and is, for example, a straight nozzle with an ejection port 210b formed on one end surface. The pure water nozzle 21b is connected to a pure water supply unit 20b that supplies pure water to the pure water nozzle 21b. The pure water supply unit 20b is, for example, a supply pipe 201b whose one end is connected to the pure water nozzle 21b, and a pure water supply source 202b connected to the other end of the supply pipe 201b. The pure water supply source 202b is configured to include a pure water tank that stores pure water (for example, DIW (de-ionized water)). In addition, a valve 203b and a flow rate adjustment unit 204b are inserted in the supply pipe 201b. The valve 203b is a valve that switches between supplying and stopping the pure water through the supply pipe 201b, and is controlled by the control unit 140. The flow rate adjustment unit 204b is configured, for example, by a mass flow controller, and adjusts the flow rate of the pure water flowing through the supply pipe 201b under the control of the control unit 140. In this configuration, when the valve 203b is opened, pure water at a predetermined flow rate adjusted by the flow rate adjustment unit 204b is supplied from the pure water supply source 202b through the supply pipe 201b to the pure water nozzle 21b and discharged from the discharge port 210b.

The nozzle movement mechanism 22 is a mechanism for moving the sulfuric acid nozzle 21a and the pure water nozzle 21b between the nozzle processing position and the nozzle standby position. Here, the "nozzle processing position" of each nozzle 21a, 21b is a position where the liquid discharged from the discharge port 210a, 210b of the nozzle 21a, 21b is supplied to the upper main surface (upper surface) of the substrate W held by the holder 1, specifically, for example, a position above the main surface and facing the center of the main surface in the vertical direction (FIGS. 7, 9, 10). On the other hand, the "nozzle standby position" is a position where both nozzles 21a, 21b do not interfere with other members (such as the plasma reactor 31 at the plasma processing position and the hand 131a of the main transport robot 131 that transfers the substrate W to and from the base 11), specifically, for example, a position outside (outside in the radial direction) the periphery of the substrate W held by the holder 1 when viewed from above (for example, FIG. 6).

Here, the sulfuric acid nozzle 21a and the pure water nozzle 21b are connected via a connecting member or the like to form the nozzle unit U. Specifically, the nozzle movement mechanism 22 includes, for example, an arm that is connected to the nozzle unit U at its tip and extends substantially horizontally, a support that supports the base end of the arm, and a motor that rotates the support around its axis. In response to an instruction from the control unit 140, the motor rotates the support around its axis at a rotation angle instructed by the control unit 140. When the support rotates by being driven by the motor, the arm turns and the nozzle unit U connected to its tip moves along an arc-shaped trajectory. The position of the support and the length of the arm are specified so that the nozzle processing position and the nozzle standby position of each nozzle 21a, 21b are located on this trajectory. In other words, the nozzle unit U moves along the arc-shaped trajectory, and each nozzle 21a, 21b moves between its nozzle processing position and nozzle standby position.

(Plasma generating unit 3)
The plasma generating unit 3 is an element that generates plasma and irradiates the generated plasma onto the substrate W held by the holder 1, and includes, for example, a plasma reactor 31, a power source 32, and a plasma reactor moving mechanism 33. The plasma generating unit 3 is capable of generating plasma under atmospheric pressure. However, the "atmospheric pressure" here means, for example, 80% or more of standard atmospheric pressure and 120% or less of standard atmospheric pressure.

The plasma reactor 31 is an irradiation section (plasma irradiation section) that irradiates a target object (here, a substrate W held by the holder 1) with plasma. Specifically, for example, the plasma reactor 31 has a flat, planar shape and is positioned above the substrate W held by the holder 1 with its thickness direction (the Z direction described below) aligned vertically, facing the main surface of the substrate W in the vertical direction. The plasma reactor 31 has, for example, a circular shape in a plan view and is approximately the same size as the substrate W to be processed (or larger than the substrate W).

The configuration of the plasma reactor 31 will be described in more detail with reference to FIG. 4 in addition to FIG. 3. FIG. 4 is a side cross-sectional view and a plan view that show the schematic configuration of the plasma reactor 31. Note that in FIG. 4, the holding member 315 is shown by a dashed line to make the drawing easier to understand.

The plasma reactor 31 includes a pair of electrode sections (a first electrode section 311 and a second electrode section 312). The pair of electrode sections 311, 312 are stacked in the thickness direction with a partition plate 313 made of a dielectric material (e.g., quartz, ceramics, etc.) sandwiched therebetween. Specifically, the first electrode section 311 is provided on one side of the thickness direction of the disk-shaped partition plate 313, and the second electrode section 312 is provided on the other side. In the following, for convenience of explanation, the direction in which the first electrode section 311, the partition plate 313, and the second electrode section 312 are stacked is referred to as the "Z direction". In addition, in a plane perpendicular to the Z direction, the extension direction of the linear electrodes 311a and 312a described later is referred to as the "X direction", and the direction perpendicular to the Z direction and the X direction is referred to as the "Y direction".

The first electrode portion 311 has a configuration in which a plurality of linear electrodes (first linear electrodes) 311a formed of an appropriate conductive material (e.g., tungsten) are connected via a collective electrode (first collective electrode) 311b formed of an appropriate conductive material (e.g., aluminum), and has an overall comb shape. Specifically, for example, each first linear electrode 311a is a linear (rod-shaped) electrode and is arranged in a position such that the long length direction is aligned with the X direction. In addition, the multiple first linear electrodes 311a are arranged at regular intervals along an arrangement direction (Y direction, which is a direction perpendicular to the X direction in the example of the figure) that intersects with the extension direction (X direction) of each first linear electrode 311a. Each first linear electrode 311a is preferably housed in a dielectric tube 314, which is a tubular member formed of a dielectric material (e.g., quartz, ceramics, etc.). On the other hand, the first assembly electrode 311b is a long, flat electrode that extends in an arc shape in a plan view. The first assembly electrode 311b is arranged so that its bulge faces one side of the extension direction of each of the first linear electrodes 311a (the -X side in the example shown in the figure), and the -X side end of each of the first linear electrodes 311a is connected to its inner periphery.

The second electrode section 312, like the first electrode section 311, has a configuration in which a plurality of linear electrodes (second linear electrodes) 312a formed of an appropriate conductive material (e.g., tungsten) are connected via a collective electrode (second collective electrode) 312b formed of an appropriate conductive material (e.g., aluminum), and has an overall comb shape. Specifically, for example, each second linear electrode 312a is a linear electrode and is arranged in a position such that the longitudinal direction is aligned with the X direction. In addition, the multiple second linear electrodes 312a are arranged at regular intervals along an arrangement direction (Y direction, which is a direction perpendicular to the X direction in the example shown in the figure) that intersects with the extension direction (X direction) of each second linear electrode 312a. Each second linear electrode 312a is preferably housed in a dielectric tube 314, which is a tubular member formed of a dielectric material (e.g., quartz, ceramics, etc.). On the other hand, the second assembly electrode 312b is a long, flat electrode that extends in an arc shape in a plan view. The second assembly electrode 312b is arranged so that its bulge faces the opposite side (the +X side in the illustrated example) to the bulge direction of the first assembly electrode 311b, and the +X side ends of each of the second linear electrodes 312a are connected to its inner periphery.

The first electrode section 311 is disposed on the +Z side of the partition plate 313, with the first assembly electrode 311b positioned to extend close to the outside of the periphery of the partition plate 313 when viewed from the Z direction. On the other hand, the second electrode section 312 is disposed on the -Z side of the partition plate 313, with the second assembly electrode 312b positioned to extend close to the outside of the periphery of the partition plate 313 when viewed from the Z direction. At this time, the second linear electrode 312a is disposed between adjacent first linear electrodes 311a when viewed from the Z direction. That is, the first linear electrodes 311a and the second linear electrodes 312a are disposed alternately along the Y direction within the main surface of the partition plate 313 without overlapping each other when viewed from the Z direction.

The first electrode section 311 and the second electrode section 312 (hereinafter also referred to as the "electrode assembly"), which are stacked with the partition plate 313 in between, are integrally held by a holding member 315 formed of an insulating material (e.g., fluororesin, etc.). Specifically, the holding member 315 is composed of a pair of holding rings 315a, 315b that are ring-shaped in a plan view. One holding ring 315a is provided in contact with one side of the electrode assembly (e.g., the side of the first electrode section 311), and the other holding ring 315b is provided in contact with the other side of the electrode assembly (e.g., the side of the second electrode section 312). Both holding rings 315a, 315b are connected to each other, so that the electrode assembly is sandwiched between the pair of holding rings 315a, 315b and held therein.

The power source 32 is a plasma power source for generating plasma, and is connected to the plasma reactor 31. Specifically, one of a pair of wires extending from the power source 32 is connected to the first electrode portion 311 (specifically, the first assembly electrode 311b), and the other is connected to the second electrode portion 312 (specifically, the second assembly electrode 312b).

The power supply 32 is controlled by the control unit 140, and applies a predetermined voltage (plasma voltage) between the first electrode unit 311 and the second electrode unit 312 in response to an instruction from the control unit 140. Then, an electric field is generated between the first linear electrode 311a and the second linear electrode 312a, and a discharge occurs between the first linear electrode 311a and the second linear electrode 312a. Since the partition plate 313, which is a dielectric, exists between the two linear electrodes 311a and 312a, this discharge becomes a so-called dielectric barrier discharge. When the discharge occurs, the gas around the first linear electrode 311a and the second linear electrode 312a becomes plasma. In other words, plasma is generated (lighted). In other words, the power supply 32 applies a voltage that is strong enough to turn the surrounding gas into plasma between the two electrodes 311 and 312 as a plasma voltage.

The power supply 32 may be, for example, an AC power supply, and may apply an AC voltage between the electrodes 311 and 312 as a plasma voltage. The power supply 32 may be, for example, a switching power supply circuit such as an inverter circuit, and may function as a high-frequency power supply, and may apply, for example, a high-frequency voltage between the electrodes 311 and 312 as a plasma voltage. The power supply 32 may be, for example, a pulse generator, and may function as a pulse power supply, and may apply a high-frequency voltage between the electrodes 311 and 312 during the on-period of a pulse signal generated by the pulse generator at a predetermined cycle. In this case, the plasma is lit mainly during the on-period of the pulse signal. As an example, the voltage value of the plasma voltage (amplitude value of the high-frequency voltage) is about 10 kV or more. When the plasma voltage is applied during the on-period of each cycle defined by a pulse wave, the frequency of the pulse wave is about several tens of kHz.

The plasma reactor moving mechanism 33 is a mechanism for moving (raising and lowering) the plasma reactor 31 between the plasma processing position and the standby position. Here, the "plasma processing position" is a position where the plasma reactor 31 irradiates plasma to the substrate W held in the holder 1, and as described below, is a position where the distance between the plasma reactor 31 and the substrate W is sufficiently small (for example, a position where the distance is about several millimeters) so that at least the amount of active species required for plasma processing can act on the substrate W (FIG. 8). On the other hand, the "standby position" is a position where the plasma reactor 31 does not irradiate plasma to the substrate W held in the holder 1, and is a position where the distance between the two is sufficiently large at least so that the plasma generated in the plasma reactor 31 does not act on the substrate W (for example, FIG. 6).

Specifically, the plasma reactor moving mechanism 33 includes, for example, a lift plate that is connected to the plasma reactor 31 at its tip and extends substantially horizontally, and a motor. Between the motor and the lift plate, a cam is provided that converts the rotational motion of the motor into the lifting motion of the lift plate. Therefore, when the motor rotates by the rotation angle instructed by the control unit 140 in response to an instruction from the control unit 140, the lift plate (and thus the plasma reactor 31 connected thereto) rises (or falls) by a distance corresponding to the rotation angle. However, the configuration of the plasma reactor moving mechanism 33 is not limited to this, and can be realized by various driving mechanisms that realize the lifting and lowering movement. For example, the plasma reactor moving mechanism 33 may be configured to include a ball screw mechanism and a motor that provides driving force to the ball screw mechanism, or may be configured to include an air cylinder.

(Guard part 4)
The guard part 4 is an element that receives processing liquid and the like that splashes from the substrate W held by the holder 1, and includes, for example, a guard 41 and a guard moving mechanism 42.

The guard 41 is composed of a tube portion 41a, an inclined portion 41b, and an extending portion 41c. The tube portion 41a is a cylindrical portion that is provided so as to surround the holding portion 1. The inclined portion 41b is provided so as to be continuous with the upper end edge of the tube portion 41a, and inclines inward as it moves vertically upward. The extending portion 41c is a flat ring-shaped portion that is provided so as to extend inward from the upper end edge of the inclined portion 41b in a substantially horizontal plane.

The guard movement mechanism 42 is a mechanism for moving (raising and lowering) the guard 41 between the guard processing position and the guard standby position. Here, the "guard processing position" is a position where the guard 41 receives processing liquid and the like that splashes from the substrate W held in the holder 1, and specifically, for example, a position where the extension portion 41c is positioned above the substrate W (e.g., FIG. 7). On the other hand, the "guard standby position" is a position where the guard 41 does not interfere with other members (such as the hand 131a of the main transport robot 131 that transfers the substrate W to and from the base 11), and specifically, for example, a position where the extension portion 41c is positioned below the substrate W held in the holder 1 (e.g., FIG. 6).

The guard movement mechanism 42 can be realized by various drive mechanisms that realize the lifting and lowering movement. Specifically, for example, the guard movement mechanism 42 may be configured to include a ball screw mechanism, a motor that provides a driving force to the ball screw mechanism, etc., or may be configured to include an air cylinder, etc.

A drainage section 43 is provided below the guard 41 to drain the processing liquid received on the inner peripheral surface of the guard 41. Specifically, the drainage section 43 includes, for example, a cup 431 provided below the guard 41 and a drainage pipe 432 connected to the cup 431, and is configured so that the processing liquid received on the inner peripheral surface of the guard 41 arranged at the guard processing position and flowing down along the inner peripheral surface is received by the cup 431 and drained from the drainage pipe 432.

In addition, an exhaust section 44 is provided on the outer side of the guard 41 to exhaust gas, mist, etc. that flows along the inner peripheral surface of the guard 41. Specifically, the exhaust section 44 includes, for example, a peripheral wall section 441 that is provided so as to surround the guard 41 from the outside, and an exhaust pipe 442 connected to the peripheral wall section 441, and is configured so that gas, mist, etc. that is received by the inner peripheral surface of the guard 41 arranged at the guard processing position and flows down along the inner peripheral surface is received by the peripheral wall section 441 and exhausted from the exhaust pipe 442.

<1-3. Processing flow>
Next, the flow of processing performed in the processing unit 132 will be described with reference to Fig. 5 and Fig. 6 to Fig. 10 in addition to Fig. 3. Fig. 5 is a diagram showing the flow of processing. Each of Fig. 6 to Fig. 10 is a diagram for explaining each processing step, and the state of each part in the processing step is shown typically.

In the following description, the substrate W to be processed is, for example, a substrate W that has been provided with a resist as a mask on at least one of its main surfaces and has been etched or ion implanted, and a series of processes are carried out in the processing unit 132 to remove (peel off) the unnecessary resist. The series of processes described below are carried out by the control unit 140 controlling each part of the processing unit 132. Furthermore, the series of processes described below are usually carried out repeatedly. In other words, when a series of processes for one substrate W is completed, the same series of processes are subsequently carried out on another new substrate W.

Step S1: Holding Step First, the substrate W to be treated is held by the holder 1. That is, the main transport robot 131 inserts the hand 131a holding the substrate W to be treated into the chamber 5 and carries the substrate W into the treatment unit 132, and the holder 1 holds the carried-in substrate W in a horizontal position with the main surface on which the resist is provided facing upward (FIG. 6). During this step, the nozzles 21a, 21b, the plasma reactor 31, and the guard 41 are each placed at their respective standby positions so as not to interfere with the hand 131a.

Step S2: Liquid Film Forming Process Successively, sulfuric acid as a processing liquid is supplied to the substrate W held by the holder 1 to form a liquid film F of sulfuric acid on the upper surface of the substrate W (FIG. 7). Specifically, for example, the nozzle moving mechanism 22 moves the sulfuric acid nozzle 21a from the nozzle standby position to the nozzle processing position. When the sulfuric acid nozzle 21a is disposed at the nozzle processing position, the valve 203a provided on the supply pipe 201a is opened. Then, the sulfuric acid stored in the sulfuric acid supply source 202a is supplied to the sulfuric acid nozzle 21a through the supply pipe 201a at a predetermined flow rate (e.g., 300 (ml/min)) adjusted by the flow rate adjustment unit 204a, and is discharged from the discharge port 210a. The sulfuric acid discharged from the sulfuric acid nozzle 21a disposed at the processing position lands on a predetermined position (e.g., the center of the main surface) on the upper main surface of the substrate W held by the holder 1. The sulfuric acid that has landed on the main surface of the substrate W spreads toward the periphery of the substrate W, forming a liquid film F of sulfuric acid that covers substantially the entire main surface.

It is preferable that the rotation mechanism 13 rotates the holder 1 (and thus the substrate W held therein) at a predetermined rotation speed at least while sulfuric acid is being ejected from the sulfuric acid nozzle 21a. This causes the sulfuric acid that has landed on the upper main surface of the substrate W to spread quickly toward the periphery of the substrate W due to centrifugal force, and a liquid film F of sulfuric acid is quickly formed that covers almost the entire main surface.

It is also preferable that the guard moving mechanism 42 positions the guard 41 at the guard processing position at least while the substrate W is being rotated. This allows sulfuric acid scattered from the periphery of the substrate W to be received by the inner peripheral surface of the guard 41, flow down along the inner peripheral surface, and then be received by the cup 431 and drained from the drain pipe 432. The same applies to the rinsing step (step S7) and drying step (step S8) described below.

When a predetermined time (e.g., about 5 to 10 seconds) has elapsed since the sulfuric acid nozzle 21a started to discharge sulfuric acid as a processing liquid, the valve 203a is closed and the discharge of sulfuric acid is stopped. Thereafter, the rotation mechanism 13 reduces the rotation speed of the substrate W to a sufficiently low rotation speed (preferably 50 rpm or less) or stops the rotation. The substrate W on which the liquid film F has been formed is rotated at a sufficiently low rotation speed (or the rotation is maintained in a stopped state) for a predetermined time, so that the liquid film F is stably held on the substrate W (so-called puddle processing).

Step S3: Voltage Application Start Process Next, the power supply 32 starts applying a predetermined voltage (voltage for generating plasma) to the plasma reactor 31. By applying a predetermined voltage to the plasma reactor 31, the gas (here, air) around the plasma reactor 31 is converted into plasma, and plasma is generated. This plasma contains various active species (when the gas around the plasma is air, for example, active species such as oxygen radicals, hydroxyl radicals, ozone gas, etc.), but the type and amount of the active species change depending on the type of gas present around the plasma reactor 31, etc.

Step S4: Lowering Step Next, the plasma reactor moving mechanism 33 moves (lowers) the plasma reactor 31 from the standby position to the plasma processing position. Since the active species in the plasma generated around the plasma reactor 31 are deactivated in a relatively short time, even if a sufficient amount of active species is present in a position close to the plasma reactor 31, most of the active species are deactivated in a position away from the plasma reactor 31. Therefore, in this step, the plasma reactor 31 is brought close to the substrate W, and the distance between them is made sufficiently small so that at least the amount of active species required for plasma processing can act on the substrate W.

The voltage application start step (step S3) and the lowering step (step S4) may be performed in either order, or may be performed in parallel. That is, the application of voltage to the plasma reactor 31 may be started before, during, or after the plasma reactor 31 is lowered. As described below, plasma processing of the substrate W proceeds when the plasma reactor 31 to which a voltage is being applied is positioned at the plasma processing position, and plasma processing of the substrate W is initiated by performing both the voltage application start step and the lowering step.

When the plasma reactor 31 to which a voltage is applied is disposed at the plasma processing position (FIG. 8), plasma is irradiated from the plasma reactor 31 disposed opposite to the main surface of the substrate W held by the holder 1, and plasma processing of the substrate W proceeds. In this plasma processing, the plasma generated around the plasma reactor 31 acts on the sulfuric acid liquid film F formed on the main surface of the substrate W, thereby improving the processing performance of the sulfuric acid. Specifically, active species in the plasma react with the sulfuric acid to generate Caro's acid (peroxomonosulfuric acid: H ₂ SO ₅ ) having high processing performance (here, oxidizing power). The generated Caro's acid and active species in the plasma act on the resist provided on the main surface of the substrate W, and the resist is oxidized and peeled off (removed). That is, here, the resist is stripped off by the plasma processing.

While the plasma processing is being performed on the substrate W, it is preferable for the rotation mechanism 13 to rotate the substrate W at a predetermined rotation speed. This allows the plasma to be uniformly irradiated over the entire upper main surface of the substrate W, improving the uniformity of processing within the main surface. However, the rotation speed is set to be sufficiently slow (e.g., about 30 to 50 rpm) so as not to disturb the liquid film F on the substrate W.

Step S5: Voltage Application Stopping Step When the plasma process (i.e., the resist stripping process) has been carried out for a predetermined processing time, at an appropriate timing thereafter, the application of voltage from the power source 32 to the plasma reactor 31 is stopped, thereby stopping the generation of plasma (i.e., the plasma is turned off).

Step S6: Raising Step After the plasma processing has been carried out for a predetermined processing time, the plasma reactor moving mechanism 33 moves (raises) the plasma reactor 31 from the plasma processing position to the standby position at an appropriate timing thereafter.

The voltage application stopping step (step S5) and the raising step (step S6) may be performed in either order, or may be performed in parallel. That is, the application of voltage to the plasma reactor 31 may be stopped before, during, or after the plasma reactor 31 is raised. As described above, the plasma processing of the substrate W proceeds when the plasma reactor 31 to which a voltage is being applied is positioned at the plasma processing position, and the plasma processing of the substrate W is terminated by, for example, performing at least one of the voltage application stopping step and the raising step.

Step S7: Rinse Process After the plasma process on the substrate W (i.e., the resist stripping process) is completed, a rinse liquid is supplied to the substrate W after the plasma process to bring the rinse liquid into contact with the substrate W, thereby washing away the liquid film F on the substrate W (rinse process) (FIGS. 9 and 10). This process will be described in detail later.

Step S8: Drying Process After the rinsing process is completed, the rotation mechanism 13 rotates the substrate W held by the holder 1 at a sufficiently high rotation speed (e.g., about 1000 to 2000 rpm) for a predetermined time (e.g., about 30 seconds). By rotating at a sufficiently high rotation speed, a large centrifugal force acts on the liquid on the substrate W, and the liquid is thrown off around the substrate W. This dries the substrate W (so-called spin drying).

When the substrate W is dried, the nozzles 21a, 21b and the guard 41 are placed in their respective standby positions, and the main transport robot 131 removes the substrate W held by the holder 1. This completes the series of processes for the substrate W.

<1-4. Rinse process>
<1-4-1. Rinse solution>
As described above, when the plasma processing on the substrate W is completed, a rinsing process is performed in which a rinsing liquid is supplied to the substrate W to bring the rinsing liquid into contact with the substrate W and wash away the liquid film F. Here, at the stage when the plasma processing (i.e., the resist stripping process) is completed, the stripped resist is dissolved in the sulfuric acid liquid film F held on the substrate W. The solubility (saturation solubility) of the resist dissolved in the liquid film F varies depending on the physical quantity (specifically, for example, pH value, temperature) of the liquid film F. Therefore, when the rinsing liquid comes into contact with the liquid film F in the rinsing process, the physical quantity changes significantly, and as a result, the solubility changes (decreases), and there is a possibility that the resist that is not completely dissolved will precipitate. There is a risk that the precipitated resist will adhere to the substrate W and become particles.

Here, the change in solubility caused by the rinsing liquid coming into contact with the substrate increases as the difference in physical quantity (physical quantity that affects solubility) between the liquid film F and the rinsing liquid that comes into contact with the liquid film F increases. Conversely, the smaller the difference in physical quantity, the smaller the change in solubility caused by the rinsing liquid coming into contact with the substrate. Therefore, here, by using a rinsing liquid whose physical quantity difference with the liquid film F is sufficiently small, the change in the solubility of the resist caused by the rinsing liquid coming into contact with the substrate is kept within a range (tolerable range) that does not cause the resist to precipitate. In other words, in the rinsing process, a rinsing liquid that keeps the change in solubility of the resist dissolved in the liquid film F within a tolerable range that does not cause the resist to precipitate is brought into contact with the substrate W after the stripping process is completed.

However, "not depositing resist" here does not necessarily mean reducing the amount of resist deposition to zero, but rather means not depositing resist in excess of the allowable amount of deposition. Furthermore, the "allowable amount of deposition" is specifically an amount of resist that, even if that amount of resist deposits, still has the effect of suppressing particle generation on the processed substrate W. In other words, as long as the effect of suppressing particle generation on the processed substrate W is still observed, the amount of resist deposition can be considered to be within the allowable amount of deposition.

In this rinsing step, specifically, the pH value, which is one of the physical quantities that affect the solubility, is used as an index, and an acidic liquid with a sufficiently small difference in pH value from the liquid film F is used as the rinsing liquid to keep the change in solubility caused by the contact of the rinsing liquid within an allowable range. In other words, when the maximum value of the difference in pH value between the rinsing liquid and the liquid film F that can keep the change in solubility within an allowable range is called the "maximum allowable pH difference," an acidic liquid with a difference in pH value between the liquid film F and the rinsing liquid that is equal to or less than this maximum allowable pH difference is used as the rinsing liquid (first rinsing liquid). If this type of rinsing liquid is brought into contact with the liquid film F after the resist stripping process is completed, the solubility will only change within an allowable range. Therefore, the resist dissolved in the liquid film F will not precipitate. In other words, if this type of rinsing liquid is used, the liquid film F on the substrate W can be washed away without causing the resist to precipitate.

The allowable range of the change in solubility is determined by various processing conditions (e.g., the type of resist, the amount of resist to be stripped (i.e., dissolved in the liquid film F), the allowable amount of precipitation, etc.). Therefore, for example, the allowable range of the change in solubility under given processing conditions can be identified by experiment, theoretical calculation, etc., and the maximum allowable pH difference can be derived based on this. Then, a liquid whose pH value difference with the liquid film F is equal to or less than the derived maximum allowable pH difference can be selected as the rinse liquid.

However, as described above, the change in solubility caused by the contact of the rinse liquid is also affected by the temperature difference between the liquid film F and the rinse liquid, and the smaller the temperature difference, the smaller the change in solubility. Therefore, as shown in FIG. 11, the maximum value of the difference in pH value between the rinse liquid and the liquid film F (maximum allowable pH difference) that can keep the change in solubility within the allowable range becomes smaller as the temperature difference between the rinse liquid and the liquid film F becomes larger. For example, the liquid film F after plasma processing is heated to, for example, about 250°C by receiving heat from the plasma, etc., and when the rinse liquid is supplied to the heated liquid film F without heating and at room temperature (about 23°C) (i.e., with a relatively large temperature difference) and brought into contact with the liquid film F, the maximum allowable pH difference is approximately "2". In other words, if a liquid whose pH difference with the liquid film F is 2 or less (for example, if the treatment liquid used to form the liquid film F is sulfuric acid with a pH value of 1, then a liquid whose pH value is 3 or less) is used as the rinse liquid, even if this liquid is supplied to the heated liquid film F without being heated and brought into contact with the liquid, the change in solubility caused by the rinse liquid coming into contact with the liquid can be kept within an acceptable range.

<1-4-2. Processing flow related to the rinsing process>
The process flow of the rinsing step based on the above concept will be described with reference to Fig. 12 in addition to Fig. 5, Fig. 9, Fig. 10. Fig. 12 is a diagram for explaining the process flow of the rinsing step.

Step S71: First rinsing step (acid rinsing step)
First, sulfuric acid as a first rinse liquid is supplied to the substrate W after the plasma processing (i.e., resist stripping processing) is completed, thereby bringing the first rinse liquid into contact with the substrate W (FIG. 9). Specifically, for example, the nozzle moving mechanism 22 moves the sulfuric acid nozzle 21a from the nozzle standby position to the nozzle processing position. When the sulfuric acid nozzle 21a is disposed at the nozzle processing position, the valve 203a provided on the supply pipe 201a is opened. Then, as described above, the sulfuric acid stored in the sulfuric acid supply source 202a is supplied to the sulfuric acid nozzle 21a through the supply pipe 201a at a predetermined flow rate (for example, 200 to 500 (ml/min), for example, 300 (ml/min)) adjusted by the flow rate adjustment unit 204a, and is discharged from the discharge port 210a. The sulfuric acid discharged from the sulfuric acid nozzle 21a disposed at the processing position lands at a predetermined position (for example, the center of the main surface) on the upper main surface of the substrate W held by the holder 1. As a result, sulfuric acid as the first rinsing liquid is supplied to (comes into contact with) the substrate W.

In this way, in the first rinsing step, the sulfuric acid stored in the sulfuric acid supply source 202a is used as the first rinsing liquid. In other words, the liquid supplied to the substrate W as the processing liquid when forming the liquid film F in the liquid film forming step (step S2) and the liquid supplied to the substrate W as the first rinsing liquid in the first rinsing step are both sulfuric acid and have the same concentration. Needless to say, in this case, the difference in pH value between the first rinsing liquid and the liquid film F is sufficiently smaller than the maximum allowable pH difference of "2" when the first rinsing liquid is supplied to the heated liquid film F without heating and brought into contact with the liquid film F, and is almost zero. Therefore, when the first rinsing liquid comes into contact with the liquid film F, there is almost no change in the pH value. Therefore, the change in solubility caused by the first rinsing liquid coming into contact with the liquid is sufficiently small, and precipitation of the resist is sufficiently avoided.

As shown in FIG. 12, when sulfuric acid as the first rinse liquid starts to be discharged from the sulfuric acid nozzle 21a, the rotation mechanism 13 rotates the substrate W held in the holder 1 while gradually increasing the rotation speed. That is, while sulfuric acid is discharged from the sulfuric acid nozzle 21a toward the substrate W, the substrate W is rotated while gradually increasing the rotation speed. Specifically, for example, the rotation mechanism 13 gradually increases the rotation speed of the substrate W from a sufficiently small (low) first rotation speed R1 (e.g., 30 to 50 rpm) to a second rotation speed R2 (e.g., 100 to 1500 rpm, for example, about 500 rpm) over a predetermined time (first time) T1 (e.g., about 3 to 5 seconds). Then, when the rotation speed reaches the second rotation speed R2, the rotation mechanism 13 continues to rotate the substrate W at this second rotation speed R2. Note that any manner of gradually increasing the rotation speed may be used. For example, the increase may be linear (at a constant rate of increase) as shown in the figure, or it may be stepped.

As the substrate W is rotated, the sulfuric acid as the first rinse liquid, which is discharged from the sulfuric acid nozzle 21a and lands on the upper main surface of the substrate W, spreads rapidly toward the periphery of the substrate W due to centrifugal force. Meanwhile, the sulfuric acid liquid film F that covered almost the entire main surface of the substrate W (i.e., the sulfuric acid liquid film F in which the peeled resist has been dissolved) is swept outward by the newly supplied sulfuric acid as the first rinse liquid (i.e., clean sulfuric acid in which the resist does not dissolve), and is rapidly discharged around the substrate W. That is, the sulfuric acid liquid film F that covered the substrate W at the time the plasma processing is completed is replaced by sulfuric acid as the first rinse liquid.

If the rotation speed of the substrate W is increased from the first rotation speed R1 to the second rotation speed R2 all at once (without intentionally taking time) instead of stepwise, the speed at which the liquid is discharged from the peripheral side of the substrate W cannot keep up with the speed at which the liquid is supplied from the center side of the substrate W, and an air-liquid interface appears near the peripheral edge of the substrate W. That is, exposed parts (i.e., dry parts) that are not covered by liquid are generated near the peripheral edge of the substrate W. Particles and the like are likely to adhere to such parts, and the cleanliness of the substrate W is likely to decrease. According to the above configuration in which the rotation speed is increased stepwise, such an air-liquid interface is unlikely to appear on the substrate W, and the cleanliness of the substrate W is unlikely to decrease. That is, the liquid film F on the substrate W can be replaced with sulfuric acid as the first rinse liquid without decreasing the cleanliness of the substrate W.

When a predetermined time (second time) T2 (e.g., about 10 seconds) has elapsed since the sulfuric acid nozzle 21a started to discharge sulfuric acid as the first rinsing liquid, the valve 203a is closed and the discharge of sulfuric acid is stopped. This ends the first rinsing process, and the sulfuric acid liquid film F that covered the substrate W at the time the plasma processing was completed is sufficiently replaced by sulfuric acid as the first rinsing liquid.

Step S72: Second Rinse Process Next, pure water as a second rinse liquid is supplied to the substrate W after the first rinse process is completed, thereby bringing the second rinse liquid into contact with the substrate W (FIG. 10). Specifically, for example, the nozzle moving mechanism 22 moves the pure water nozzle 21b from the nozzle standby position to the nozzle processing position. When the pure water nozzle 21b is placed at the nozzle processing position, the valve 203b provided on the supply pipe 201b is opened. Then, the pure water stored in the pure water supply source 202b is supplied to the pure water nozzle 21b through the supply pipe 201b at a predetermined flow rate adjusted by the flow rate adjustment unit 204b, and is discharged from the discharge port 210b. The pure water discharged from the pure water nozzle 21b placed at the processing position lands on a predetermined position (for example, the center of the main surface) on the upper main surface of the substrate W held by the holder 1. As a result, the pure water as the second rinse liquid is supplied (contacted) to the substrate W.

In this way, in the second rinsing step, the pure water stored in the pure water supply source 202b is used as the second rinsing liquid. In other words, the pH value of the second rinsing liquid is significantly different from the pH value of the sulfuric acid supplied to the substrate W as the first rinsing liquid. Therefore, by supplying pure water as the second rinsing liquid, the sulfuric acid remaining on the substrate W as the first rinsing liquid is diluted, and the pH value changes (increases) significantly. However, since the first rinsing liquid remaining on the substrate W at this time is clean sulfuric acid in which the resist does not dissolve, the resist does not precipitate even if the pH value changes significantly.

12, the discharge of sulfuric acid as the first rinse liquid from the sulfuric acid nozzle 21a is stopped, and instead, the discharge of pure water from the pure water nozzle 21b as the second rinse liquid is started. Furthermore, while the discharge is continued, the rotation mechanism 13 continues to rotate the substrate W held in the holder 1 at the second rotation speed R2. That is, after the rotation speed of the substrate W reaches the second rotation speed R2 in the first rinse step, the rotation mechanism 13 continues to rotate the substrate W at the second rotation speed R2 until the second rinse step is completed (i.e., until the drying step (step S8) is started). As a result, the pure water as the second rinse liquid discharged from the pure water nozzle 21b and landed on the upper main surface of the substrate W spreads quickly toward the periphery of the substrate W due to centrifugal force, and the sulfuric acid as the first rinse liquid remaining on the main surface of the substrate W is replaced by the pure water as the second rinse liquid.

When a predetermined time has elapsed since the discharge of pure water as the second rinsing liquid from the pure water nozzle 21b has begun, the valve 203b is closed and the discharge of the pure water is stopped. This ends the second rinsing process, and the sulfuric acid as the first rinsing liquid remaining on the substrate W at the time the first rinsing process is completed is thoroughly washed away by the pure water as the second rinsing liquid.

This completes the rinsing process, after which the drying process (step S8) described above is carried out.

<1-5. State of the substrate after processing>
20 shows a microscope image of the upper surface of the processed substrate W when DIW is used as the rinse liquid that is first brought into contact with the substrate W after the resist stripping process is completed, and the same process as the above series of processes (steps S1 to S8) is performed except for this (first comparative example). Also, FIG. 21 shows a microscope image of the upper surface of the processed substrate W when IPA (isopropyl alcohol) is used as the rinse liquid that is first brought into contact with the substrate W after the resist stripping process is completed, and the same process as the above series of processes is performed except for this (second comparative example). As is clear from these microscope images, it can be seen that particles are generated on the processed substrate W in both cases where DIW or IPA is used as the rinse liquid that is first brought into contact with the substrate W after the resist stripping process is completed.

On the other hand, FIG. 13 shows a microscope image of the top surface of the substrate W after processing (after the above series of processes (steps S1 to S8) have been performed) when sulfuric acid of the same concentration as the processing liquid that forms the liquid film F is used as the rinsing liquid (first rinsing liquid) that is first brought into contact with the substrate W after the resist stripping process is completed. As is clear from this microscope image, when sulfuric acid of the same concentration as the processing liquid is used as the rinsing liquid that is first brought into contact with the substrate W after the resist stripping process is completed, no particles are present on the substrate W after the process.

Both DIW and IPA are neutral liquids, and the difference in pH value between them and the liquid film F is large. When such a neutral liquid is used as the rinse liquid that is first brought into contact with the substrate W after the resist stripping process is completed, the reason why particles are generated on the substrate W after the process is considered to be that when the rinse liquid is supplied and brought into contact with the substrate W, the pH value rises suddenly, and the solubility of the resist dissolved in the liquid film F decreases accordingly, and as a result, the resist that cannot be dissolved precipitates (so-called pH shock). In contrast, when sulfuric acid with the same concentration as the processing liquid that forms the liquid film F is used as the rinse liquid that is first brought into contact with the substrate W after the resist stripping process is completed, the reason why particles are not generated on the substrate W after the process is considered to be that when the rinse liquid is brought into contact with the liquid film F, there is almost no change in the pH value, so there is no decrease in the solubility due to the change in pH value, and therefore the precipitation of the resist is not induced.

<1-6. Effects>
The substrate processing method according to the above embodiment includes a liquid film formation process (step S2) of supplying an acidic processing liquid to a substrate W having a resist thereon to form a liquid film F of the processing liquid, a plasma processing process of irradiating plasma onto the substrate W holding the liquid film F to proceed with a resist stripping process, and a rinsing process (step S7) of bringing the substrate W after the stripping process into contact with a rinsing liquid (first rinsing liquid) that brings the change range of the solubility of the resist dissolved in the liquid film F into an allowable range that does not cause precipitation of the resist.

According to this configuration, the first rinse liquid is brought into contact (supplied) with the substrate W after the resist stripping process is completed, and the liquid film F in which the stripped resist is dissolved is washed away from the substrate W. Here, the first rinse liquid limits the change in solubility of the resist dissolved in the liquid film F to an allowable range that does not cause resist to precipitate. In other words, even when the first rinse liquid comes into contact with the substrate W, the solubility changes only within an allowable range that does not cause resist to precipitate. Therefore, the contact of the first rinse liquid with the substrate W does not induce resist to precipitate. This suppresses the generation of particles on the substrate W after processing.

More specifically, in the above embodiment, the change in solubility is kept within an acceptable range by using an acidic liquid as the first rinse liquid, the difference in pH value between the first rinse liquid and the liquid film F being equal to or less than the maximum allowable pH difference. With this configuration, the first rinse liquid is selected using the pH value as an index, so that a first rinse liquid that can keep the change in solubility when the first rinse liquid comes into contact with the liquid within an acceptable range can be easily and appropriately selected.

More specifically, in the above embodiment, the first rinse liquid is a liquid whose pH difference with the liquid film F is 2 or less. With this configuration, it is possible to make the range of change in solubility when the first rinse liquid comes into contact with the liquid sufficiently small, and the generation of particles can be sufficiently suppressed.

In the above embodiment, the first rinse liquid and the processing liquid are both sulfuric acid. This configuration simplifies the piping system and other components required to supply the liquids compared to when different types of liquids are used for the first rinse liquid and the processing liquid.

In particular, in the above embodiment, the first rinse liquid and the processing liquid are sulfuric acid of equal concentration. With this configuration, when the first rinse liquid comes into contact with the liquid film F, there is almost no change in pH value. Therefore, it is possible to make the range of change in solubility when the rinse liquid comes into contact with the liquid particularly small, and the generation of particles can be sufficiently suppressed.

In the above embodiment, in the rinsing step, the first rinse liquid is discharged from the nozzle (sulfuric acid nozzle) 21a toward the substrate W (i.e., the first rinse liquid is poured onto the substrate W), while the rotation speed of the substrate W is increased in stages. As described above, if the rotation speed is increased all at once rather than in stages, the speed at which the liquid is supplied to the substrate W cannot keep up with the speed at which the liquid is discharged from the substrate W, and an air-liquid interface may appear on the substrate W, resulting in exposed portions that are not covered by the liquid. Particles and the like are likely to adhere to such portions, and the cleanliness of the substrate W is likely to decrease. According to the above configuration in which the rotation speed is increased in stages, such an air-liquid interface is unlikely to appear on the substrate W, and the cleanliness of the substrate W is unlikely to decrease. In other words, the liquid film F in which the peeled resist is dissolved can be replaced with the first rinse liquid without decreasing the cleanliness of the substrate W.

<2. Second embodiment>
<2-1. Rinse solution>
In the first embodiment, the pH value, which is one of the physical quantities that affect the solubility, is used as an index, and an acidic liquid whose pH difference from the liquid film F is sufficiently small (i.e., equal to or less than the maximum allowable pH difference) is used as the rinsing liquid, so that the range of change in solubility caused by the rinsing liquid coming into contact with the liquid is kept within the allowable range.

In contrast, in this embodiment, temperature, which is another physical quantity that affects the solubility, is used as an index, and a liquid with a sufficiently small difference in temperature from the liquid film F is used as the rinse liquid, so that the change in solubility caused by the contact of the rinse liquid is within an allowable range. In other words, when the maximum value of the temperature difference between the rinse liquid and the liquid film F that can keep the change in solubility within an allowable range is called the "maximum allowable temperature difference," a liquid whose temperature difference with the liquid film F is equal to or less than this maximum allowable temperature difference is used as the rinse liquid. With such a rinse liquid, even if it comes into contact with the liquid film F after the resist stripping process is completed, the solubility will only change within an allowable range. Therefore, the resist dissolved in the liquid film F will not precipitate. In other words, with such a rinse liquid, the liquid film F on the substrate W can be washed away without causing the resist to precipitate.

As described above, the allowable range of the solubility change is determined by various processing conditions. Therefore, for example, the allowable range of the solubility change under given processing conditions can be determined by experiment, theoretical calculation, etc., and the maximum allowable temperature difference can be derived based on this. Then, a liquid whose temperature has been adjusted so that the temperature difference between the liquid film F is equal to or less than the derived maximum allowable temperature difference can be used as the rinse liquid.

However, as mentioned above, the change in solubility caused by contact with the rinse liquid is also affected by the difference in pH between the liquid film F and the rinse liquid, and the smaller the difference in pH, the smaller the change in solubility. Therefore, as shown diagrammatically in FIG. 14, the maximum value of the temperature difference between the rinse liquid and the liquid film F (maximum allowable temperature difference) that allows the change in solubility to fall within the allowable range becomes smaller as the difference in pH between the rinse liquid and the liquid film F becomes larger. For example, when sulfuric acid with a pH value of approximately "1" is used as the treatment liquid and carbonated water, which is a weak acid with a pH value of approximately "5", is used as the rinse liquid, the maximum allowable temperature difference is approximately "200". In other words, when using carbonated water as the rinse liquid, by heating it so that the temperature difference between it and the liquid film F is 200 or less (for example, if the liquid film F after plasma processing has been heated to about 250°C, by heating it to 50°C or more, preferably 80°C or more), the change in solubility caused by the rinse liquid coming into contact with the liquid can be kept within an acceptable range.

<2-2. Processing unit>
The configuration of a processing unit 132a capable of performing a rinsing process based on the above concept will be described with reference to Fig. 15. Fig. 15 is a side view showing a schematic configuration of the processing unit 132a. This processing unit 132a is provided in, for example, the substrate processing system 100, similar to the processing unit 132 according to the first embodiment.

Processing unit 132a differs from processing unit 132 in the configuration of the liquid supply unit, but the other configurations (holding unit 1, plasma generating unit 3, guard unit 4, and chamber 5) are similar to those of processing unit 132. In the following, elements that do not differ from processing unit 132 are indicated with the same reference numerals and their explanations are omitted.

The liquid supply unit 2a of the processing unit 132a according to this embodiment is an element that supplies liquid to the substrate W held in the holder 1, similar to the liquid supply unit 2 of the processing unit 132 according to the first embodiment. The liquid supply unit 2a includes, for example, three nozzles (a sulfuric acid nozzle 21a, a pure water nozzle 21b, and a carbonated water nozzle 21c) and a nozzle movement mechanism 22.

As described in the first embodiment, the sulfuric acid nozzle 21a is a nozzle that ejects sulfuric acid toward the substrate W held in the holder 1, and the pure water nozzle 21b is a nozzle that ejects pure water toward the substrate W held in the holder 1. As described in the first embodiment, the sulfuric acid nozzle 21a is connected to a sulfuric acid supply unit 20a that supplies sulfuric acid thereto, and the pure water nozzle 21b is connected to a pure water supply unit 20b that supplies pure water thereto.

The carbonated water nozzle 21c is a nozzle that ejects heated carbonated water ( _CO2 water) toward the substrate W held by the holder 1, and is specifically, for example, a straight nozzle with an ejection port 210c formed on one end surface. The carbonated water nozzle 21c is connected to a carbonated water supply unit 20c that supplies carbonated water to the carbonated water nozzle 21c. Specifically, the carbonated water supply unit 20c includes, for example, a supply pipe 201c having one end connected to the carbonated water nozzle 21c, and a carbonated water supply source 202c connected to the other end of the supply pipe 201c. The carbonated water supply source 202c includes, for example, a pure water tank that stores pure water (for example, DIW), a dissolution processing unit that dissolves carbon dioxide in the pure water stored therein to generate carbonated water, and the like. In addition, a valve 203c, a flow rate adjustment unit 204c, and a heating unit 205c are inserted into the supply pipe 201c. The valve 203c is a valve that switches between supplying and stopping the carbonated water through the supply pipe 201c, and is controlled by the control unit 140. The flow rate adjustment unit 204c is, for example, a mass flow controller, and adjusts the flow rate of the carbonated water flowing through the supply pipe 201c under the control of the control unit 140. The heating unit 205c is, for example, a heater, and heats the carbonated water flowing through the supply pipe 201c to a temperature specified by the control unit 140 under the control of the control unit 140. In this configuration, when the valve 203c is opened, carbonated water at a predetermined flow rate adjusted by the flow rate adjustment unit 204c flows from the carbonated water supply source 202c through the supply pipe 201c, is heated to a predetermined temperature by the heating unit 205c, is supplied to the carbonated water nozzle 21c, and is discharged from the discharge port 210c. That is, heated carbonated water (hereinafter referred to as "heated carbonated water") is discharged from the carbonated water nozzle 21c.

The configuration of the nozzle movement mechanism 22 is as described in the first embodiment. However, in this embodiment, the sulfuric acid nozzle 21a, the pure water nozzle 21b, and the carbonated water nozzle 21c are connected via a connecting member or the like to form a nozzle unit U, and the nozzle movement mechanism 22 moves the nozzle unit U along an arc-shaped trajectory to move each of the nozzles 21a, 21b, and 21c between each nozzle processing position and the nozzle standby position. Needless to say, the "nozzle processing position" of the carbonated water nozzle 21c, like the nozzle processing positions of the other nozzles 21a and 21b, is a position where the liquid discharged from the discharge port 210c of the nozzle 21c is supplied to the upper main surface (upper surface) of the substrate W held by the holder 1, and specifically, for example, a position above the main surface and facing the center of the main surface in the vertical direction.

<2-3. Processing flow>
Next, the process flow of the rinsing process performed in the processing unit 132a will be described with continued reference to Fig. 15. The overall process flow of the series of processes performed on the substrate W is similar to that in the first embodiment (see Fig. 5).

First, heated carbonated water is supplied as a rinsing liquid to the substrate W after the plasma processing (i.e., resist stripping processing) is completed, thereby bringing the rinsing liquid into contact with the substrate W. Specifically, for example, the nozzle moving mechanism 22 moves the carbonated water nozzle 21c from the nozzle standby position to the nozzle processing position. When the carbonated water nozzle 21c is placed at the nozzle processing position, the valve 203c provided on the supply pipe 201c is opened. Then, as described above, the carbonated water stored in the carbonated water supply source 202c flows through the supply pipe 201c at a predetermined flow rate adjusted by the flow rate adjustment unit 204c, is heated to a predetermined temperature (here, a temperature of 80°C or more and 100°C or less) by the heating unit 205c, is supplied to the carbonated water nozzle 21c, and is discharged from the discharge port 210c. The heated carbonated water discharged from the carbonated water nozzle 21c arranged at the processing position lands on a predetermined position (for example, the center of the main surface) on the upper main surface of the substrate W held by the holder 1. This allows heated carbonated water to be supplied (contacted) to the substrate W as a rinsing liquid.

As described above, when sulfuric acid with a pH value of about "1" is used as the processing liquid and carbonated water, which is a weak acid with a pH value of about "5", is used as the rinsing liquid, the change in solubility caused by the rinsing liquid coming into contact with the liquid can be kept within an acceptable range by heating the processing liquid so that the temperature difference between the processing liquid and the liquid film F is "200" or less. In this rinsing process, the carbonated water stored in the carbonated water supply source 202c is heated to a temperature of 80°C or more and 100°C or less and used as the rinsing liquid. Therefore, even if the liquid film F after plasma processing has been heated to about 250°C, for example, the change in solubility caused by the rinsing liquid coming into contact with the liquid can be kept within an acceptable range that does not cause resist precipitation.

In this embodiment, as in the first embodiment, when the carbonated water nozzle 21c starts to eject heated carbonated water as a rinsing liquid, the rotation mechanism 13 rotates the substrate W held in the holder 1 while gradually increasing the rotation speed. Specifically, for example, the rotation mechanism 13 gradually increases the rotation speed of the substrate W from a sufficiently small first rotation speed R1 to a higher second rotation speed R2 over a first time T1 (see FIG. 12). Then, when the rotation speed reaches the second rotation speed R2, the rotation mechanism 13 continues to rotate the substrate W at this second rotation speed R2.

As the substrate W is rotated, the heated carbonated water as the rinsing liquid, which is discharged from the carbonated water nozzle 21c and lands on the upper main surface of the substrate W, spreads rapidly toward the periphery of the substrate W due to centrifugal force. Meanwhile, the sulfuric acid liquid film F that covered almost the entire main surface of the substrate W (i.e., the sulfuric acid liquid film F in which the peeled resist has been dissolved) is swept outward by the newly supplied heated carbonated water as the rinsing liquid and is rapidly discharged around the substrate W. That is, the sulfuric acid liquid film F that covered the substrate W at the time the plasma processing is completed is replaced by the heated carbonated water as the rinsing liquid. In addition, by gradually increasing the rotation speed, the liquid film F on the substrate W can be replaced by the heated carbonated water as the rinsing liquid without reducing the cleanliness of the substrate W.

When a predetermined time has elapsed since the heated carbonated water nozzle 21c started to eject the heated carbonated water as a rinsing liquid, the valve 203c is closed and the ejection of the heated carbonated water is stopped. This ends the rinsing process, and the sulfuric acid liquid film F that covered the substrate W at the time the plasma processing was completed is washed away by the heated carbonated water as a rinsing liquid.

After the above rinsing process is completed, the substrate W may be subjected to a second rinsing process similar to that of the first embodiment. That is, the above rinsing process may be the first rinsing process (i.e., heated carbonated water may be used as the first rinsing liquid), and then a second rinsing process may be performed in which pure water is supplied as the second rinsing liquid.

<2-4. Effects>
In the above embodiment, the change in solubility is kept within an allowable range by using as the rinse liquid a liquid whose temperature difference with respect to the liquid film F is equal to or less than the maximum allowable temperature difference. With this configuration, various liquids can be used as the rinse liquid by adjusting the temperature, thereby widening the range of rinse liquid options.

More specifically, in the above embodiment, the rinse liquid is carbonated water heated to a temperature of 80°C or more and 100°C or less. With such a rinse liquid, even when the rinse liquid comes into contact with (is supplied to) the liquid film F whose temperature has been increased by plasma irradiation, the range of change in temperature is kept sufficiently small. Therefore, it is possible to make the range of change in solubility when the rinse liquid comes into contact with the liquid sufficiently small, and the generation of particles can be sufficiently suppressed.

<3. Third embodiment>
For example, in the first embodiment, sulfuric acid is discharged from the sulfuric acid nozzle 21a as a rinsing liquid (first rinsing liquid) onto the substrate W held by the holder 1 to supply the rinsing liquid to the substrate W, thereby bringing the rinsing liquid into contact with the substrate W. However, the manner in which the rinsing liquid is brought into contact with the substrate W is not limited to this. For example, the substrate W may be brought into contact with the rinsing liquid by immersing the substrate W in a storage tank in which the rinsing liquid is stored.

<3-1. Immersion unit>
The configuration of the immersion unit 7 for realizing such a processing mode will be described with reference to Fig. 16. Fig. 16 is a side view showing a schematic configuration of the immersion unit 7. The immersion unit 7 is a processing unit that performs a rinsing process on one or more substrates W at once, and is provided, for example, in association with the processing unit 132 according to the first embodiment, and performs a series of processes on the substrates W in cooperation with the processing unit 132. Specifically, for example, when the processing unit 132 (Fig. 3) described in the first embodiment is provided as at least one of the multiple processing units included in the main body 130 of the substrate processing system 100, the immersion unit 7 is provided as at least one of the remaining processing units.

The immersion unit 7 includes a storage tank 71, a liquid supply section 72, and a holding section 73.

The storage tank 71 is a tank for storing liquid. Specifically, the storage tank 71 has an internal volume capable of accommodating one or more substrates W in an upright position, and is open at the top. The bottom side of the storage tank 71 is closed, and a drain pipe 712 with a valve 711 inserted therein is connected to the bottom side. The valve 711 is a valve that switches between draining liquid through the drain pipe 712 and stopping the liquid, and is controlled by the control unit 140. That is, when the valve 711 is opened under the control of the control unit 140, the liquid stored in the storage tank 71 is drained through the drain pipe 712. In addition, an outer tank 713 is provided near the upper end of the outer peripheral wall of the storage tank 71. The upper edge of the outer tank 713 is disposed above the upper edge of the storage tank 71, and the liquid overflowing from the upper edge of the storage tank 71 is received by the outer tank 713 and drained through a drain pipe (not shown).

The liquid supply unit 72 is an element that supplies liquid to the storage tank 71 (and thus to the substrate W placed inside the storage tank 71), and includes, for example, two nozzles (a sulfuric acid nozzle 721a and a pure water nozzle 721b).

The sulfuric acid nozzle 721a is a nozzle that ejects sulfuric acid. The sulfuric acid nozzle 721a is connected to a sulfuric acid supply unit 70a that supplies sulfuric acid thereto. The configuration of the sulfuric acid supply unit 70a is the same as that of the sulfuric acid supply unit 20a described above. That is, the sulfuric acid supply unit 70a specifically includes, for example, a supply pipe 701a connected to one end of the sulfuric acid nozzle 721a, a sulfuric acid supply source 702a connected to the other end of the supply pipe 701a, a valve 703a inserted in the supply pipe 701a, and a flow rate adjustment unit 704a. The sulfuric acid supply source 702a stores, for example, sulfuric acid of the same concentration as that stored in the sulfuric acid supply source 202a (i.e., the sulfuric acid supply source 202a provided in the processing unit 132 used in cooperation with the immersion unit 7). In this configuration, when the valve 703a is opened under the control of the control unit 140, sulfuric acid at a predetermined flow rate adjusted by the flow rate adjustment unit 704a is supplied from the sulfuric acid supply source 702a through the supply pipe 701a to the sulfuric acid nozzle 721a, from which it is discharged and supplied into the storage tank 71.

The pure water nozzle 721b is a nozzle that ejects pure water. The pure water supply unit 70b that supplies pure water to the pure water nozzle 721b is connected to the pure water nozzle 721b. The configuration of the pure water supply unit 70b is the same as that of the pure water supply unit 20b described above. That is, the pure water supply unit 70b specifically includes, for example, a supply pipe 701b whose one end is connected to the pure water nozzle 721b, a pure water supply source 702b connected to the other end of the supply pipe 701b, a valve 703b inserted into the supply pipe 701b, and a flow rate adjustment unit 704b. In this configuration, when the valve 703b is opened under the control of the control unit 140, pure water at a predetermined flow rate adjusted by the flow rate adjustment unit 704b is supplied from the pure water supply source 702b through the supply pipe 701b to the pure water nozzle 721b, ejected from there, and supplied into the storage tank 71.

The holding unit 73 holds one or more substrates W in an upright position with their main surfaces disposed in a substantially vertical plane. Specifically, the holding unit 73 has a configuration in which multiple holding rods 732 protrude from the main surface of a main body plate 731 that is disposed in an upright position with its main surface disposed in a vertical plane, and the multiple holding rods 732 abut against the peripheral portion of the substrate W from below, thereby holding the substrate W in an upright position. When multiple substrates W are held, the multiple substrates W are arranged at intervals along the extension direction of the holding rods 732.

A holder movement mechanism 733 is connected to the holder 73. The holder movement mechanism 733 is a mechanism that raises and lowers the holder 73 between a position (immersion position) where the substrate W held therein is disposed inside the storage tank 71, and a position (transfer position) where the substrate W held therein is disposed outside the storage tank 71 (e.g., above the storage tank 71).

<3-2. Processing flow>
The process flow of the rinsing step performed in the immersion unit 7 will be described with reference to Fig. 17 in addition to Fig. 16. Fig. 17 is a diagram showing the process flow.

Step S101: Storage Step First, sulfuric acid as a first rinsing liquid is stored in the storage tank 71. Specifically, for example, the valve 703a provided in the supply pipe 701a is opened. Then, the sulfuric acid stored in the sulfuric acid supply source 702a is supplied to the sulfuric acid nozzle 721a through the supply pipe 701a at a predetermined flow rate adjusted by the flow rate adjustment unit 704a, and is discharged from there. The discharged sulfuric acid is supplied to the storage tank 71 and stored therein.

Step S102: Loading Step Meanwhile, the substrate W to be subjected to rinsing processing is loaded into the immersion unit 7. That is, at the stage where a series of processing steps from step S1 to step S6 is completed in the processing unit 132, the main transport robot 131 unloads the substrate W held in the holder 1 (i.e., the substrate W after the plasma processing is completed) and loads it into the immersion unit 7. At this time, the main transport robot 131 transports the substrate W in a horizontal position so that the liquid film F held on the substrate W is maintained, and loads it into the immersion unit 7.

Step S103: First Rinse Process Next, the substrate W is immersed in the storage tank 71 in which sulfuric acid as the first rinse liquid is stored. Specifically, for example, the substrate W carried into the immersion unit 7 is first changed in position from a horizontal position to an upright position, and then held by the holder 73 arranged at a transfer position above the storage tank 71. The holder 73 may hold a plurality of substrates W. When one or more substrates W are held by the holder 73, the holder moving mechanism 733 moves (lowers) the holder 73 from the transfer position to the immersion position. With sulfuric acid stored in the storage tank 71 as the first rinse liquid, the holder 73 is arranged at the immersion position, whereby the substrate W held therein is immersed in sulfuric acid as the first rinse liquid, and the first rinse liquid comes into contact with the substrate W.

When the substrate W is brought into an upright position, part of the liquid film F held therein falls along the main surface of the substrate W and is discharged, but the remaining part still remains on the main surface of the substrate W. The substrate W in this state is immersed in a storage tank 71 in which sulfuric acid as a first rinsing liquid is stored, so that the sulfuric acid as the first rinsing liquid comes into contact with (is supplied to) the substrate W, and the liquid film F of sulfuric acid remaining on the main surface of the substrate W (i.e., the liquid film F of sulfuric acid in which the peeled resist has been dissolved) is replaced by the sulfuric acid as the first rinsing liquid (i.e., clean sulfuric acid in which the resist does not dissolve).

In the first rinsing step, the sulfuric acid stored in the sulfuric acid supply source 702a is used as the first rinsing liquid, and sulfuric acid of the same concentration as that of the sulfuric acid supply source 202a provided in the liquid supply unit 2 of the processing unit 132 is stored here. In other words, in the liquid film forming step (step S2), the liquid supplied to the substrate W as the processing liquid when forming the liquid film F and the liquid supplied to the substrate W as the first rinsing liquid in the first rinsing step are both sulfuric acid and have the same concentration. Needless to say, in this case, the difference in pH value between the first rinsing liquid and the liquid film F is sufficiently smaller than the maximum allowable pH difference of "2" when the first rinsing liquid is supplied to the heated liquid film F without heating and brought into contact with the liquid film F, and is almost zero. Therefore, when the first rinsing liquid comes into contact with the liquid film F, there is almost no change in the pH value. Therefore, the change in solubility caused by the first rinsing liquid coming into contact with the liquid film F becomes sufficiently small, and precipitation of the resist is sufficiently avoided.

Step S104: Second Rinse Process When a predetermined time has elapsed since the substrate W was immersed in sulfuric acid as the first rinse liquid, the liquid in the storage tank 71 is replaced from sulfuric acid as the first rinse liquid to pure water as the second rinse liquid. Specifically, for example, the valve 711 provided on the drain pipe 712 is opened. As a result, the sulfuric acid as the first rinse liquid stored in the storage tank 71 is drained. Meanwhile, the valve 703b provided on the supply pipe 701b is opened. Then, the pure water stored in the pure water supply source 702b is supplied to the pure water nozzle 721b through the supply pipe 701b at a predetermined flow rate adjusted by the flow rate adjustment unit 704b, and is discharged from there. The discharged pure water is supplied to the storage tank 71 and stored therein. By replacing the liquid in the storage tank 71 from sulfuric acid as the first rinsing liquid to pure water as the second rinsing liquid, the substrate W held by the holder 73 arranged at the immersion position is immersed in the pure water as the second rinsing liquid, and the second rinsing liquid comes into contact with the substrate W. That is, the pure water as the second rinsing liquid comes into contact with the substrate W, and the sulfuric acid as the first rinsing liquid remaining on the main surface of the substrate W is replaced by the pure water as the second rinsing liquid.

In this way, in the second rinsing step, the pure water stored in the pure water supply source 702b is used as the second rinsing liquid. In other words, the pH value of the second rinsing liquid is significantly different from the pH value of the sulfuric acid supplied to the substrate W as the first rinsing liquid. For this reason, when the pure water as the second rinsing liquid comes into contact with (is supplied to) the substrate W, the sulfuric acid as the first rinsing liquid remaining on the substrate W is diluted, causing a significant change (increase) in the pH value. However, since the first rinsing liquid remaining on the substrate W at this time is clean sulfuric acid in which the resist does not dissolve, the resist does not precipitate even if the pH value changes significantly.

When a predetermined time has elapsed since the substrate W was immersed in the pure water as the second rinsing liquid, the holder movement mechanism 733 moves (raises) the holder 73 from the immersion position to the transfer position.

This completes the rinsing process. After that, the substrate W held in the holder 73 is removed from the immersion unit 7, for example, by the main transport robot 131.

<3-3. State of the substrate after processing>
FIG. 18 shows a microscope image of the upper surface of the substrate W after the above-mentioned rinse process (after the above-mentioned series of processes (steps S1 to S8)) is performed using sulfuric acid of the same concentration as the process liquid forming the liquid film F as the rinse liquid (first rinse liquid) that is first brought into contact with the substrate W after the resist stripping process is completed. As is clear from this microscope image, even when sulfuric acid of the same concentration as the process liquid is used as the rinse liquid that is first brought into contact with the substrate W after the resist stripping process is completed, and this rinse liquid is brought into contact (supplied) with the substrate W by immersing the substrate W in the storage tank 71 that stores the rinse liquid, no particles are present on the substrate W after the process. Needless to say, the reason why no particles are generated on the substrate W after the process is considered to be that when the rinse liquid comes into contact with the liquid film F, there is almost no change in pH value, so that there is no decrease in solubility due to the change in pH value, and thus no precipitation of resist is induced.

<3-4. Effects>
According to the above embodiment, in the rinsing step, the substrate W is immersed in the storage tank 71 that stores the rinsing liquid (first rinsing liquid). With this configuration, the liquid film F in which the peeled resist is dissolved can be quickly drained from the substrate W and replaced with the rinsing liquid.

4. Other embodiments
In the first rinsing step according to the first embodiment, the first rinsing liquid (specifically, for example, sulfuric acid having the same concentration as the processing liquid) may be heated and then brought into contact with the substrate W. For this purpose, for example, as in the processing unit 132b shown in FIG. 19, the liquid supply unit 2b may include a heated sulfuric acid nozzle 21d for discharging heated sulfuric acid in addition to the same configuration as the liquid supply unit 2 of the processing unit 132 according to the first embodiment. One end of a supply pipe 201d connected to a sulfuric acid supply source 202a is connected to this heated sulfuric acid nozzle 21d. In addition, a valve 203d, a flow rate adjustment unit 204d, and a heating unit 205d are interposed in this supply pipe 201d. In this configuration, when the valve 203d is opened under the control of the control unit 140, sulfuric acid at a predetermined flow rate adjusted by the flow rate adjustment unit 204d flows from the sulfuric acid supply source 202a through the supply pipe 201d, is heated to a predetermined temperature by the heating unit 205d, and is supplied to the heated sulfuric acid nozzle 21d and discharged from there. That is, in the first rinsing step (step S71), sulfuric acid as the first rinsing liquid (i.e., sulfuric acid having the same concentration as the processing liquid) can be heated and then brought into contact with the substrate W.

According to this modified example, the rinsing liquid (first rinsing liquid) is heated before it is brought into contact with the substrate W, so that even when the first rinsing liquid comes into contact with (is supplied to) the liquid film F whose temperature has been raised by irradiating it with plasma, the range of change in temperature is kept sufficiently small. In other words, both the range of change in pH and the range of change in temperature are kept small. Therefore, it is possible to make the range of change in solubility when the first rinsing liquid comes into contact with the liquid particularly small, and the generation of particles can be particularly sufficiently suppressed.

In the first embodiment, the rinse liquid (first rinse liquid) may be of any type, and is not limited to the sulfuric acid exemplified above, so long as the difference in pH value between the rinse liquid and the liquid film F is equal to or less than the maximum allowable pH difference. For example, the rinse liquid may be hydrochloric acid (e.g., dilute hydrochloric acid with a pH value of "3"). Needless to say, no matter what type of liquid is used, the concentration can be adjusted as necessary so that the difference in pH value between the rinse liquid and the liquid film F is equal to or less than the maximum allowable pH difference defined by the given processing conditions.

In the first embodiment, the rinsing liquid is sulfuric acid having the same concentration as the processing liquid used on the substrate W as the processing liquid when forming the liquid film F, but the rinsing liquid may be sulfuric acid having a different concentration from the processing liquid. Needless to say, even in this case, the rinsing liquid is of a concentration such that the difference in pH value between the rinsing liquid and the liquid film F is equal to or less than the maximum allowable pH difference defined by the given processing conditions.

In the second embodiment, the rinse liquid may be any type of liquid as long as the temperature difference between the rinse liquid and the liquid film F is equal to or less than the maximum allowable temperature difference, and is not limited to the carbonated water exemplified above. For example, heated pure water, sulfuric acid, hydrochloric acid, etc. may be used as the rinse liquid. Needless to say, no matter what type of liquid is used, the heating temperature may be set as necessary so that the temperature difference between the rinse liquid and the liquid film F is equal to or less than the maximum allowable temperature difference specified by the given processing conditions. For example, when a liquid with a smaller pH value than carbonated water (i.e., a liquid with a smaller pH value difference between the rinse liquid and the liquid film F) is used as the rinse liquid, the maximum allowable temperature difference may be greater than "200". That is, the heating temperature may be lower than 80°C. Conversely, when a liquid with a higher pH value than carbonated water (e.g., pure water) is used as the rinse liquid, the maximum allowable temperature difference may be smaller than "200". That is, it may be necessary to increase the heating temperature to greater than 80°C.

In the third embodiment, the first rinse liquid stored in the storage tank 71 may be the rinse liquid in the second embodiment (i.e., heated carbonated water). Also, in the third embodiment, a process (second rinse process) is performed in which the substrate W is immersed in the storage tank 71 in which pure water is stored as the second rinse liquid, but this process does not necessarily have to be performed in the immersion unit 7. For example, after the first rinse process is completed, the substrate W may be transferred out of the immersion unit 7 and transferred back into the processing unit 132, where the second rinse process (i.e., the second rinse process (step S72) in the first embodiment) is performed.

The configuration of the processing unit 132 and the processing flow performed therein are not limited to those exemplified in the above embodiment.

For example, in the above embodiment, nozzles 21a, 21b, and 21c (or nozzles 721a and 721b) that eject different types of liquid are provided separately, but multiple types of liquid may be selectively ejected from one nozzle. In this case, multiple supply pipes 201a, 201b, and 201c (or multiple supply pipes 701a and 701b) may be connected to the single nozzle.

In addition, in the above embodiment, the nozzle movement mechanism 22 moves the multiple nozzles 21a, 21b, and 21c as a unit, but each nozzle 21a, 21b, and 21c may be provided with a separate nozzle movement mechanism to move each nozzle 21a, 21b, and 21c separately and independently. Needless to say, in this case, it is not necessary to connect the multiple nozzles 21a, 21b, and 21c. Also, at least one of the multiple nozzles 21a, 21b, and 21c may be fixed. In other words, the nozzle movement mechanism may be omitted for at least one nozzle.

In addition, in the above embodiment, the holder 1 holds the substrate W in a horizontal position by gripping the periphery of the substrate W with the chuck pins 12, but the method of holding the substrate W is not limited to this and any method may be used. For example, the holder may hold the substrate W in a horizontal position by adsorbing the back surface of the substrate W with a suction mechanism provided on the upper surface of the base portion 11.

In the above embodiment, a plurality of guards 41 may be provided. In this case, the plurality of guards 41 may have basically the same configuration but may be different sizes, and the plurality of guards 41 of different sizes may be arranged in a nested manner. That is, the cylindrical portions 41a may be arranged concentrically, and the inclined portions 41b and the extending portions 41c may be arranged in a nested manner so that they are stacked vertically. In addition, when a plurality of guards 41 are provided, the guard moving mechanism 42 may move each guard 41 independently, and may switch the position of each guard 41 depending on the type of liquid discharged onto the substrate W, thereby switching the guard 41 that receives the splashed liquid.

In addition, in each of the above embodiments, the plasma generating unit 3 generates plasma under atmospheric pressure, but plasma may be generated under low pressure. That is, a pump may be provided to reduce the pressure in the internal space of the chamber 5, and a voltage may be applied to the plasma reactor 31 to generate plasma after the internal space of the chamber 5 is reduced to a predetermined pressure by the pump.

In addition, in the above embodiment, the processing unit 132 performs a process to remove resist formed on the substrate W, but the process performed in the processing unit 132 is not limited to this. For example, the processing unit 132 may perform a process to remove organic matter (e.g., organic particles, an organic layer, an organic film) present on the substrate W.

In the above embodiment, sulfuric acid is used as the treatment liquid, but the treatment liquid is not limited to this. For example, a chemical solution containing at least one of sulfuric acid, sulfate, peroxosulfuric acid, and peroxosulfate may be used as the treatment liquid. A chemical solution containing hydrogen peroxide may be used as the treatment liquid, and for example, a mixture of sulfuric acid and hydrogen peroxide may be used as the treatment liquid. Furthermore, depending on the purpose of the plasma treatment, the type of the object to be removed, etc., chemical solutions such as SC1 (a mixture of hydrogen peroxide and ammonia) and SC2 (a mixture of hydrogen peroxide and hydrochloric acid) (so-called cleaning chemicals) may be used as the treatment liquid, or chemical solutions such as hydrofluoric acid, hydrochloric acid, and phosphoric acid (so-called etching chemicals) may be used as the treatment liquid.

The configuration of the substrate processing system 100 and the processing flow performed therein are not limited to those exemplified in the above embodiment.

For example, the number of processing units 132 provided in the substrate processing system 100 does not have to be 12. Also, for example, the number of load ports 111 provided in the substrate processing system 100 does not have to be 3.

In addition, the program P may be stored in a recording medium, and the program P may be installed in the control unit 140 using this recording medium.

In addition, the substrate W to be processed in the substrate processing system 100 does not necessarily have to be a semiconductor substrate. For example, the substrate W to be processed may be a glass substrate for a photomask, a glass substrate for a liquid crystal display, a glass substrate for a plasma display, a substrate for an FED (Field Emission Display), a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, etc. In addition, the shape and size of the substrate W to be processed are not limited to those exemplified above. For example, the shape of the substrate W to be processed may be a rectangular plate.

Although the substrate processing apparatus and substrate processing method have been described in detail above, the above description is merely illustrative in all respects, and the substrate processing apparatus and substrate processing method are not limited thereto. It is understood that countless variations not illustrated can be envisioned without departing from the scope of this disclosure. The configurations described in the above embodiments and the above variations can be combined or omitted as appropriate, as long as they are not mutually inconsistent.

REFERENCE SIGNS LIST 1 Holding section 2 Liquid supply section 21a Sulfuric acid nozzle 21b Pure water nozzle 21c Carbonated water nozzle 20a Sulfuric acid supply section 20b Pure water supply section 20c Carbonated water supply section 205c Heating section 3 Plasma generating section 4 Guard section 5 Chamber 7 Immersion unit 132 Substrate processing apparatus (processing unit)
100 Substrate processing system

Claims (8)

a liquid film forming step of supplying an acidic processing liquid to a substrate on which a resist is provided, to form a liquid film of the processing liquid;
a plasma treatment step of irradiating plasma onto the substrate holding the liquid film to proceed with a resist stripping process;
a rinsing step of contacting the substrate after the stripping process with a rinse liquid that brings the change in solubility of the resist dissolved in the liquid film into an allowable range that does not cause precipitation of the resist;
Equipped with
an acidic liquid having a pH difference between the rinse liquid and the liquid film equal to or less than a maximum allowable pH difference is used as the rinse liquid, thereby keeping the change in solubility within the allowable range;
A method for processing a substrate. 2. The substrate processing method according to claim 1 ,
The rinse liquid is a liquid having a pH difference of 2 or less between the rinse liquid and the liquid film.
A method for processing a substrate. 3. The substrate processing method according to claim 1 , further comprising the steps of:
The rinse liquid and the treatment liquid are both sulfuric acid.
A method for processing a substrate. 4. The substrate processing method according to claim 3 ,
The rinse solution and the treatment solution are sulfuric acid having the same concentration.
A method for processing a substrate. 5. A substrate processing method according to claim 1 , further comprising the steps of:
The rinse liquid is heated and then brought into contact with the substrate.
A method for processing a substrate. 6. A substrate processing method according to claim 1 , further comprising the steps of:
In the rinsing step,
While the rinsing liquid is being discharged from a nozzle toward the substrate, the substrate is rotated while the rotation speed is increased stepwise.
A method for processing a substrate. 6. A substrate processing method according to claim 1 , further comprising the steps of:
In the rinsing step,
Immersing the substrate in a storage tank containing the rinsing liquid;
A method for processing a substrate. A holder for holding the substrate;
a liquid supply unit that supplies a liquid to the substrate held by the holder;
a plasma irradiation unit that irradiates plasma onto the substrate held by the holding unit;
A control unit that controls the holding unit, the liquid supply unit, and the plasma irradiation unit;
Equipped with
The control unit:
The substrate on which the resist is provided is held by the holding part,
causing the liquid supply unit to supply an acidic processing liquid onto the substrate to form a liquid film of the processing liquid;
The plasma irradiation unit irradiates plasma onto the substrate holding the liquid film to proceed with a resist stripping process;
The liquid supply unit supplies a rinse liquid to the substrate after the stripping process is completed, the rinse liquid being such that a change in solubility of the resist dissolved in the liquid film falls within an allowable range in which the resist is not precipitated ;
an acidic liquid having a pH difference between the rinse liquid and the liquid film equal to or less than a maximum allowable pH difference is used as the rinse liquid, thereby keeping the change in solubility within the allowable range;
Substrate processing equipment.

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