JP7659910B2 - Plasma processing method and bonding system - Google Patents

Description

The present invention relates to a plasma processing method and a bonding system.

It has been widely known that plasma treatment is performed to give a target object a specific function. For example, in the method described in Patent Document 1, a laminate of a polymer film and an inorganic substrate is subjected to an inactivation treatment selected from a group including vacuum plasma treatment and atmospheric pressure plasma treatment using a specific atmospheric pressure plasma, thereby realizing a laminate with a narrow transition region width between good adhesion parts with high adhesive strength between the film and substrate and easy peeling parts with low adhesive strength.

JP 2017-149040 A

However, in the semiconductor manufacturing process, when the object of the plasma processing is something that is easily affected by plasma irradiation, such as a wafer, there is a risk that the wafer may be damaged depending on the type of plasma processing.

Note that these issues generally occur even when the plasma processing targets something other than wafers.

The present disclosure therefore aims to provide a plasma processing method and bonding system that can accurately achieve the purpose of the plasma processing while minimizing damage to the target of the plasma processing.

The plasma processing method disclosed herein includes the steps of preparing a first joining member and a second joining member that have been subjected to a first plasma treatment in a vacuum atmosphere, performing a second plasma treatment on the first joining member or the second joining member in an atmosphere with a lower degree of vacuum than the first plasma treatment, and joining the first joining member and the second joining member.

Even if the surface of the first joining member or the second joining member is once modified by the first plasma treatment, the degree of modification of the surface deteriorates over time. However, by performing the second plasma treatment on the first joining member or the second joining member in this manner, the degree of modification of the surface can be restored. The second plasma treatment used in this case is a plasma treatment with a lower degree of vacuum than the first plasma treatment, so that the surface modification of the member, which is the purpose of the plasma treatment, can be achieved while minimizing damage to the first joining member or the second joining member.

In the plasma processing method disclosed herein, the second plasma processing may be a plasma processing performed in an atmospheric pressure environment.

In this way, by using the second plasma treatment performed in an atmospheric pressure environment when restoring the degree of surface modification of the first or second joining member, damage to the first or second joining member due to the plasma treatment can be further prevented.

In the plasma processing method of the present disclosure, the second plasma processing may be a processing to reduce the contact angle of water at the joint between the first bonding member and the second bonding member.

In this way, the affinity of the first and second bonding members for water is improved by the plasma treatment, so hydrophilic bonding, which is a type of direct bonding, can be performed accurately.

In the plasma processing method of the present disclosure, the second plasma treatment may be a treatment that increases the ratio of hydrophilic functional groups at the joints between the first and second bonding members.

In this way, the ratio of hydrophilic functional groups at the joints of the first and second bonding members is increased by plasma treatment, improving their affinity for water and enabling hydrophilic bonding, which is a type of direct bonding, to be performed accurately.

In the plasma processing method of the present disclosure, the bonded portions of the first bonding member and the second bonding member may be directly bonded to each other by hydrophilic bonding using a hydrophilic functional group.

In this way, the first and second bonding members can be bonded by hydrophilic bonding, which is a type of direct bonding, using hydrophilic functional groups whose ratio is increased by the plasma treatment.

In the plasma processing method of the present disclosure, the hydrophilic bonding may be performed in a state where water is held at the bonded portions of the first and second bonding members.

In this way, hydrophilic bonding, which is a type of direct bonding, can be performed more accurately while retaining water at the joint between the first and second bonding members.

In the plasma processing method disclosed herein, the first bonding member is a wafer, the second bonding member is a substrate, the first plasma processing is performed in a pre-process of a semiconductor manufacturing process including a process of forming a predetermined pattern on the wafer, and the second plasma processing may be performed in a post-process of the semiconductor manufacturing process including a process of mounting a semiconductor chip cut from the wafer on the substrate.

In this way, even if a predetermined time elapses between the pre-process and the post-process of the semiconductor manufacturing process after the first plasma treatment is performed in the pre-process of the semiconductor manufacturing process and the degree of modification of the surface of the joint between the first joining member or the second joining member deteriorates, the degree of modification of the surface of the first joining member or the second joining member can be suitably restored by performing the second plasma treatment in the post-process of the semiconductor manufacturing process.

The bonding system disclosed herein is a bonding system that bonds a first bonding member and a second bonding member that have been subjected to a first plasma treatment in a vacuum atmosphere, and includes a plasma processing unit that performs a second plasma treatment on the first bonding member or the second bonding member in an atmosphere with a lower degree of vacuum than the first plasma treatment, and a bonding unit that bonds the first bonding member and the second bonding member.

Even if the surface of the first joining member or the second joining member is once modified by the first plasma treatment, the degree of modification of the surface deteriorates over time. However, by performing the second plasma treatment on the first joining member or the second joining member in this manner, the degree of modification of the surface can be restored. The second plasma treatment used in this case is a plasma treatment with a lower degree of vacuum than the first plasma treatment, so that the surface modification of the member, which is the purpose of the plasma treatment, can be achieved while minimizing damage to the first joining member or the second joining member.

The present disclosure allows the first and second joining members to be joined accurately while minimizing damage to the first and second joining members.

FIG. 1 is a diagram for explaining an example of an outline of a vacuum plasma process. FIG. 1 is a diagram for explaining an example of an outline of a vacuum plasma process. FIG. 1 is a diagram for explaining an example of an outline of atmospheric pressure plasma processing. FIG. 1 is a diagram for explaining an example of an outline of a plasma processing method. 1 is a flowchart showing an example of the contents of a plasma processing method. 10 is a flowchart showing an example of the contents of a joining process. 1A to 1C are diagrams for explaining the operation of a plasma processing method.

One embodiment of the plasma processing method will be described below with reference to the drawings.

In summary, the plasma processing method of the present invention is applied to semiconductor manufacturing processing, and includes performing a second plasma processing in a post-process with a lower vacuum than the first plasma processing on the first and second joining members that have been subjected to a first plasma processing in a vacuum atmosphere in a pre-process. Here, the pre-process and the post-process can be performed close to each other in time, for example, consecutively, but in this embodiment, it is assumed that the pre-process is performed in a different environment and the post-process is performed after a certain time. In this specification, the term "preparation" refers to applying the members that have been processed in the pre-process so that the post-process can be performed, that is, to carrying them in and carrying out the processing required before the second plasma processing. Therefore, this embodiment also covers a mode in which the post-process is started by carrying in the members that are the result of carrying out the pre-process without carrying out the pre-process, and carrying out the processing required before the second plasma processing.

Next, the plasma processing method of this embodiment will be described with reference to the drawings. First, as a pre-process, vacuum plasma processing is performed on a wafer. The wafer includes a first wafer to be diced and a second wafer on which semiconductor chips are mounted.

As shown in FIG. 1, the vacuum plasma processing is performed, for example, by placing a wafer 13 on opposing electrodes 10, 11 provided in a chamber. An RF power supply 12 is connected to the opposing electrodes 10, 11 to generate plasma between the opposing electrodes 10, 11. The wafers 13 may be plasma-processed one by one, or multiple wafers may be plasma-processed simultaneously. As shown in FIG. 2, the vacuum plasma processing may be performed by connecting RF power supplies 12A, 12B to the opposing electrodes 10, 11, respectively, and applying AC power of different voltage values and frequencies to the opposing electrodes 10, 11, thereby irradiating plasma between the opposing electrodes 10, 11. The plasma-processed wafer 13 is removed from the chamber by a hand (not shown) and transported by a magazine or the like.

Here, the vacuum plasma process is an example of the first plasma process, and is a plasma process carried out in a vacuum atmosphere. For example, the vacuum plasma process applies a direct plasma irradiation method in which a substrate is directly placed between electrodes (plasma space) and irradiated with plasma, with the aim of supporting high-speed processing.

Then, the wafer that has gone through the pre-processing is carried into a bonding system that is used in the post-processing. The bonding system performs a dicing process on the carried-in wafer (first wafer) to produce semiconductor chips, and performs a cleaning process on the bonded portions of the produced semiconductor chips and the wafer (second wafer). Next, atmospheric pressure plasma processing is performed on the bonded portions of the semiconductor chips and wafer that have been subjected to the cleaning process.

As shown in FIG. 3, atmospheric pressure plasma processing is performed by a plasma irradiation unit 14 provided above the drive stage 20. The plasma irradiation unit 14 is composed of a pair of opposing electrodes 15, 16, and irradiates plasma from below the opposing electrodes 15, 16 to the wafer 13 placed on the drive stage 20. An RF power supply 17 is connected to the opposing electrode 15, and is configured to be able to perform continuous plasma processing on the wafer 13 placed on the drive stage 20.

Here, atmospheric pressure plasma processing is an example of the second plasma processing, and is a plasma processing performed in an atmospheric pressure atmosphere with a lower degree of vacuum than the vacuum plasma processing. For example, the atmospheric pressure plasma processing applies a remote plasma irradiation method in which plasma is ejected from a slit for the purpose of suppressing damage to the wafer. Note that the second plasma processing is not limited to an atmospheric pressure atmosphere, and may be a plasma processing performed in an atmosphere in which gas has been replaced with nitrogen or the like, a pressurized atmosphere, or a low vacuum atmosphere with a lower degree of vacuum than the first plasma processing.

Then, the wafer that has been subjected to the atmospheric plasma treatment is subjected to a surface hydrophilization treatment, etc., and a mounting substrate is produced in which a semiconductor chip is mounted on the wafer. The steps up to the atmospheric plasma treatment, which corresponds to the second plasma treatment, correspond to the "preparation" of the present invention. A specific example of a plasma treatment method in the bonding system will be described later with reference to Figures 5 and 6. Note that in the following explanation, the second substrate is described as a wafer, but the second substrate is not limited to a wafer, and may be, for example, a substrate other than a wafer, such as a printed circuit board, or a substrate on which an individual semiconductor chip has already been mounted.

As shown in FIG. 4, the bonding system 100 includes, for example, a dicing device 110, a cleaning device 120, a plasma processing device 130, and a surface hydrophilization device 140 as components for carrying out the above-mentioned plasma processing. Each device may be arranged enclosed in the same housing, or may be arranged in a so-called line, with items processed in each device being handed over to the next process by a transport device or by hand. Furthermore, the system is not limited to these devices, and may also include devices for other processing processes.

The dicing device 110 is a device that cuts a disk-shaped wafer into a grid pattern and separates the ICs (integrated circuits) formed on the wafer into individual semiconductor chips.

The cleaning device 120 is a device that uses a sponge or the like to scrub and gently wash the surface of the semiconductor chips diced by the dicing device 110, thereby cleaning the wafer cutting debris, adhesives, and other organic matter generated by the dicing device 110.

The plasma processing apparatus 130 is an apparatus that performs the second plasma processing. Specifically, the plasma processing apparatus 130 performs atmospheric pressure plasma processing on the bonding portion between the semiconductor chip cleaned by the cleaning apparatus 120 and the wafer on which the semiconductor chip is mounted. For example, the plasma processing apparatus 130 uses atmospheric pressure plasma processing to remove a coating layer such as an oxide film that has formed on the surface over time at the bonding portion between the semiconductor chip and the wafer, the surface of which has been modified by vacuum plasma processing in the pre-process of the semiconductor manufacturing process, thereby modifying the surface. At this time, atmospheric pressure plasma processing causes less damage to the bonding portion of the wafer than vacuum plasma processing, and therefore has the advantage of being able to modify the surface while suppressing damage to the target of the plasma processing.

The surface hydrophilization device 140 hydrophilizes the junction between the semiconductor chip and the substrate that have been subjected to atmospheric plasma processing by the plasma processing device 130. The surface hydrophilization device 140, for example, supplies pure water to the semiconductor chip or substrate while rotating the semiconductor chip or substrate held by the spin chuck, and diffuses the pure water into the junction between the semiconductor chip and the substrate to hydrophilize it. Here, "hydrophilization" refers to a process that increases the ratio of hydrophilic functional groups on the surfaces of the semiconductor chip and the substrate, thereby reducing the contact angle with water on the surfaces of the semiconductor chip and the substrate and increasing the affinity for water. In hydrophilization, the distance between the hydrophilic functional groups is appropriately maintained by holding water in the hydrophilic functional groups formed at the junction between the semiconductor chip and the substrate, and hydrophilization is performed smoothly.

(Specific example of plasma treatment method)
Next, an example of the plasma processing method according to this embodiment will be described with reference to the flow charts shown in FIGS.

As shown in FIG. 5, first, wafers that have been subjected to vacuum plasma processing in the pre-processing of semiconductor manufacturing are carried in (step S100). The carried in wafers include a first wafer to be diced and a second wafer on which semiconductor chips produced by dicing the first wafer are mounted. This carrying in may include, for example, storing wafers that have been plasma processed in another location or device, and transporting them for carrying into the bonding system 100.

Next, the wafer (first wafer) carried in the previous step S100 is diced to produce semiconductor chips (step S200). Specifically, the disk-shaped wafer (first wafer) prepared in the previous step S100 is cut into a lattice pattern, and the ICs (integrated circuits) formed on the wafer are separated into individual semiconductor chips to produce the semiconductor chips.

Next, a bonding process is performed between the wafer (second wafer) that was loaded in the previous step S100 and the semiconductor chip that was fabricated in the previous step S200 (step S300).

Figure 6 shows the detailed steps of the bonding process. As shown in Figure 6, in the bonding process, first, the semiconductor chip produced in the previous step S300 is washed (step S310). Specifically, the bond between the substrate and the semiconductor chip produced in the previous step S300 is scrubbed or gently washed using, for example, a sponge to clean off the wafer cutting debris generated during dicing, organic matter such as adhesives, etc.

Next, the semiconductor chip cleaned in the previous step S310 is subjected to atmospheric pressure plasma treatment to modify the surface of the semiconductor chip (step S320). Specifically, the surface of the semiconductor chip cleaned in the previous step S310 is modified by removing a coating layer such as an oxide film that has formed on the surface over time at the bonded portion between the semiconductor chip and the substrate by the atmospheric pressure plasma treatment.

Next, the surface of the semiconductor chip whose surface has been modified in the previous step S320 is made hydrophilic (step S330). Specifically, while rotating the semiconductor chip whose surface has been modified in the previous step S320 while held by the spin chuck, pure water is supplied to the semiconductor chip, and the pure water is diffused into the joint between the semiconductor chip and the substrate, thereby making the semiconductor chip hydrophilic.

Next, the substrate (second wafer) that was brought in at the previous step S100 is cleaned (step S340). Specifically, the surface of the substrate is cleaned by, for example, scrubbing and rubbing with a sponge or the like at the bonding portion between the substrate and the semiconductor chip that was prepared at the previous step S100.

Next, the substrate cleaned in the previous step S340 is subjected to atmospheric pressure plasma treatment to modify the surface of the substrate (step S350). Specifically, the substrate cleaned in the previous step S340 is subjected to atmospheric pressure plasma treatment to remove a coating layer such as an oxide film that has formed on the surface over time at the joint between the substrate and the semiconductor chip, thereby modifying the surface.

Next, the surface of the substrate whose surface has been modified in the previous step S350 is made hydrophilic (step S360). Specifically, while the substrate whose surface has been modified in the previous step S350 is rotated while being held by a spin chuck, pure water is supplied to the substrate, and the pure water is diffused into the joint between the substrate and the semiconductor chip, thereby making the substrate hydrophilic.

Next, the surface of the semiconductor chip that was made hydrophilic in the previous step S330 and the surface of the substrate that was made hydrophilic in the previous step S360 are pressed against each other while overlapping each other to bond the semiconductor chip and the substrate (step S370), and the flow chart shown in FIG. 5 is terminated. In the above plasma treatment, the atmospheric pressure plasma treatment is performed on both the semiconductor chip and the substrate, but the atmospheric pressure plasma treatment may be performed on only either the semiconductor chip or the substrate.

Next, the operation of the plasma processing method of this embodiment will be described.

As shown in FIG. 7, in this embodiment, the initial contact angle of the wafer with respect to water is relatively high (corresponding to (1)). Then, when vacuum plasma processing is performed on the wafer in the front-end process of the semiconductor manufacturing process, the contact angle of the wafer with respect to water is significantly reduced (corresponding to (2)). After the vacuum plasma processing is performed, the contact angle of the wafer with respect to water, which was reduced by the vacuum plasma processing, gradually increases after a certain period of time, including the process of moving from the front-end process to the back-end process of the semiconductor manufacturing process (corresponding to (3)). In other words, the hydrophilicity of the wafer is gradually lost immediately after the vacuum plasma processing. Therefore, by performing atmospheric pressure plasma processing on such a wafer, the contact angle of the wafer with respect to water is reset (corresponding to (4)). By performing atmospheric pressure plasma processing, the hydrophilicity of the wafer surface can be restored while suppressing damage to the wafer.

That is, even if a coating layer such as an oxide film forms on the wafer surface over time after the wafer surface has been modified by vacuum plasma processing, causing the modification of the wafer surface to deteriorate, performing atmospheric pressure plasma processing on such a wafer removes the coating layer formed on the wafer surface and resets the contact angle of the wafer with water. In this case, atmospheric pressure plasma processing causes less damage to the wafer than vacuum plasma processing, so that the wafer bonding process can be performed smoothly while minimizing damage to the wafer.

The above embodiment can also be implemented in the following ways:

In the above embodiment, an example was described in which a semiconductor chip and a substrate are bonded. However, the combination of objects to be bonded is not limited to a semiconductor chip and a substrate, and any combination that allows bonding may be used. Furthermore, the manner of bonding between the semiconductor chip and the substrate is not limited to direct bonding, in which the two are bonded directly, but may be indirect bonding, in which the semiconductor chip and the substrate are indirectly bonded by interposing an adhesive such as resin between them.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The elements of the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified, and may be modified as appropriate. Furthermore, configurations shown in different embodiments may be replaced or combined in terms of area.

10, 11... opposing electrodes, 12, 12A, 12B... RF power supply, 13... wafer, 14... plasma irradiation section, 15, 16... opposing electrodes, 17... RF power supply, 20... drive stage, 100... bonding system, 110... dicing device, 120... cleaning device, 130... plasma processing device, 140... surface hydrophilization device.

Claims (4)

a first plasma treatment process performed on bonding surfaces of a first wafer which is cut into individual pieces to become a first bonding member and a second wafer to which the first bonding member cut from the first wafer is bonded , the first plasma treatment process being performed in a vacuum atmosphere and reducing contact angles of the first and second wafers with water;
a dicing step of cutting the first wafer processed by the first plasma processing step into individual pieces to form the first bonding members;
a second plasma treatment process performed on the first wafer cut by the dicing process and subjected to a cleaning process and the second wafer subjected to the first plasma treatment process , the second plasma treatment process being performed in an atmosphere with a lower degree of vacuum than the first plasma treatment process and reducing the contact angles of the first and second wafers with respect to water;
a step of bonding the first bonding member obtained from the first wafer that has been subjected to the second plasma treatment step to a second bonding member obtained from the second wafer that has been subjected to the second plasma treatment step ,
Plasma treatment method. The second plasma treatment step is a plasma treatment performed in an atmospheric pressure atmosphere.
The plasma processing method according to claim 1 . the first bonding member is a semiconductor chip cut from a wafer and separated into individual pieces,
the second bonding member is a substrate,
the first plasma processing step is performed in a pre-process of a semiconductor manufacturing process including a step of forming a predetermined pattern on the wafer,
The second plasma treatment step is performed in a later step of a semiconductor manufacturing process including a step of mounting the semiconductor chip on a substrate.
The plasma processing method according to claim 1 . A joining system for joining a first joining member and a second joining member,
a first plasma processing unit that performs a first plasma treatment on bonding surfaces of a first wafer that is cut into pieces to become the first bonding members and a second wafer to which the first bonding members cut from the first wafer are bonded , the first plasma treatment being performed in a vacuum atmosphere and reducing contact angles of the first and second wafers with water;
a dicing processing section for cutting the first wafer that has been plasma-processed by the first plasma processing section into individual pieces to form the first bonding members;
a second plasma processing unit that performs a second plasma processing on the first wafer cut by the dicing processing unit and cleaned, and the second wafer that has been subjected to the first plasma processing , the second plasma processing being performed in an atmosphere with a lower degree of vacuum than the first plasma processing , and reducing the contact angles of the first and second wafers with respect to water;
a bonding section that bonds the first bonding member obtained from the first wafer that has been subjected to the second plasma treatment by the second plasma processing section and the second bonding member obtained from the second wafer that has been subjected to the second plasma treatment ,
Joining system.

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