JP7601371B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

The present invention relates to a manufacturing device and method for a resin product in which a metal layer is formed on the surface of the resin.

Low-dielectric resins are beginning to be used in various circuit boards, such as those with low transmission loss that are compatible with millimeter waves or microwaves. Examples of low-dielectric resins include liquid crystal polymer (LCP) and fluororesins such as polytetrafluoroethylene (PTFE). However, resin materials such as LCP and PTFE have problems with poor adhesion between themselves and with copper, which is used as wiring material. For this reason, techniques are known that chemically roughen the surface of the circuit board substrate or form irregularities on the surface of the copper foil that is to be adhered to the substrate, thereby improving the physical adhesion between the resin substrate and the copper.

However, when the surface of a resin substrate is chemically roughened and a metal such as copper is formed on the surface of the substrate, the roughness of the substrate surface increases the transmission loss of the circuit board. On the other hand, when copper is attached to the surface of the substrate using an adhesive, the adhesive layer itself becomes a cause of the transmission loss of the circuit board. When copper is formed on the surface of the substrate by plating, the adhesion between the substrate and the copper is insufficient. Another possible method is to irradiate the PTFE substrate with atmospheric plasma to activate the surface, replace the fluorine in the PTFE substrate with hydroxyl groups derived from moisture in the air, and adhere the copper to the surface of the PTFE substrate to obtain a laminate of the PTFE substrate and copper.

However, even when the PTFE substrate is irradiated with atmospheric plasma, the contact angle of the PTFE substrate with water is at most about 50°. When copper is adhered to the surface of the PTFE substrate, the degree of adhesion between the PTFE substrate and the copper is about 0.2 to 0.4 N/mm. Therefore, there is a risk that the copper may peel off from the PTFE substrate during the process of creating a copper circuit pattern on the PTFE substrate. Furthermore, if heat is applied to the PTFE substrate during the process of creating the circuit pattern, the degree of adhesion between the PTFE substrate and the copper will further decrease. Furthermore, since the surface of the PTFE substrate is modified for about 24 hours, it is necessary to quickly adhere the copper to the surface of the PTFE substrate, which is a constraint on the production of circuit boards.

A technique is known in which the surface of a substrate is cleaned with a high-energy beam in a vacuum and then ionized water vapor is irradiated onto the surface of the substrate to cause hydroxyl groups to be adsorbed onto the surface of the substrate (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 9-3220

However, because the energy of ionized water vapor is strong, once adsorbed hydroxyl groups are detached from the surface of the substrate when other water vapor ions are irradiated onto the surface of the substrate. For this reason, in the invention described in Patent Document 1, the contact angle between the surface of the substrate and water is about 40°. And, in the invention described in Patent Document 1, there is a problem in that it is difficult to firmly adhere metal to the surface of a resin member.

The present application has been made in light of these circumstances, and aims to provide a plasma processing apparatus and a plasma processing method that impart high hydrophilicity to the hydrophobic surface of a resin for a long period of time, and provide high adhesion between a resin member and a metal layer on the member surface, firmly bonding them together.

In order to solve such problems, the invention described in claim 1 is a plasma processing apparatus that irradiates a surface of a resin present in a chamber with plasma to improve the wettability of the surface of the resin, and has a holding section that holds the resin to be irradiated with the plasma, and a holding side circuit that applies a holding side voltage as a DC voltage to the held resin, a gas introduction section that introduces gas into the chamber, and a plasma irradiation device that converts the gas into plasma. The plasma side circuit is configured to apply a plasma side voltage as a DC voltage to the plasma irradiation device, and the holding side circuit is set so that the time for which the holding side voltage is applied and the time for which the plasma side circuit applies the plasma side voltage to the plasma irradiation device are separate, and the plasma side circuit is characterized in that it has an application time adjustment section for setting the time for which the plasma side circuit applies the plasma side voltage to be shorter than the time for which the holding side voltage is applied to the holding side circuit .

The invention described in claim 2 is characterized in that, in addition to the configuration described in claim 1, the plasma side circuit is configured so that the time for applying the holding side voltage and the time for applying the plasma side voltage are separate for the process of imparting hydroxyl groups to the resin in a state in which at least some of the atoms constituting the resin have been released by irradiating the resin with plasma through the plasma side circuit.

The invention described in claim 3 is characterized in that, in addition to the configuration described in claim 1 or 2 , the application time adjustment unit of the plasma side circuit is a switch for controlling on and off the application of the plasma side voltage to the plasma irradiation device.

The invention described in claim 4 is characterized in that, in addition to the configuration described in any one of claims 1 to 3 , the holding side circuit applies the holding side voltage independently of the plasma side circuit in the process of introducing the gas into the chamber, converting the gas into plasma, and irradiating the gas onto the surface of the resin.

The invention described in claim 5 is characterized in that, in addition to the configuration described in any one of claims 1 to 4 , the plasma side circuit applies a positive voltage as the plasma side voltage to the plasma irradiation device, and the holding side circuit applies a positive voltage as the holding side voltage to the resin.

The invention described in claim 6 is characterized in that, in addition to the configuration described in any one of claims 1 to 5 , the holding side circuit applies the holding side voltage to at least a portion of the holding section depending on the position where the resin is present.

The invention described in claim 7 is a plasma processing method comprising: a chamber in which a resin to be irradiated with plasma is accommodated; a holding section for holding the resin to be irradiated with the plasma; a holding circuit for applying a holding voltage as a DC voltage to the held resin; a gas inlet section for introducing a gas into the chamber; and a plasma irradiation device for plasmatizing the gas; and a plasma side circuit configured to apply a plasma side voltage as a DC voltage to the plasma irradiation device. The method irradiates plasma to the surface of the resin present in the chamber and improves the wettability of the surface of the resin. The holding circuit is set so that the time for which the holding voltage is applied to the resin and the time for which the plasma side circuit applies the plasma side voltage to the plasma irradiation device are separate in order to impart hydroxyl groups to the resin, and the plasma side circuit is provided with an application time adjustment section for setting the time for which the plasma side circuit applies the plasma side voltage to be shorter than the time for which the holding side voltage is applied to the holding circuit .

According to the inventions described in claims 1 and 7 , the time for applying the holding side voltage to the resin held in the holding part of the holding side circuit that applies the holding side voltage as a DC voltage to the resin to be irradiated with plasma in order to give hydroxyl groups to the resin, and the time for applying the plasma side voltage to the plasma irradiation device of the plasma side circuit that is configured to apply the plasma side voltage as a DC voltage to the plasma irradiation device that turns the gas introduced by the gas introduction part into plasma, are set to be separate, so that the timing at which the plasma irradiation device generates ions and radicals to irradiate the resin held in the holding part with ions and radicals, and the state of the potential around the holding part and the resin held in the holding part can be freely adjusted, and the timing and state at which the ions and radicals act on the resin while the resin is contained in the chamber can be freely adjusted. This allows the radicals to be applied to the surface of the resin in a suitable state, providing high adhesion between the resin member and the metal layer on the member surface, and firmly bonding them.
According to the inventions described in claims 1 and 7, the application time adjustment unit of the plasma side circuit is set so that the time during which the plasma side circuit applies the plasma side voltage is shorter than the time during which the holding side circuit applies the holding side voltage to the holding unit. Therefore, even before the plasma irradiation process by the plasma irradiation device, a potential difference is generated between the periphery of the resin held in the holding unit and the part other than the periphery of the resin in the chamber, and the distribution state of ions and radicals in the chamber can be easily controlled so that the environment is favorable for plasma generation by the plasma irradiation device. Even after the plasma irradiation process, radicals due to discharge generated by applying the holding side voltage are present in the holding unit, and the addition of hydroxyl groups can be steadily performed. This allows various radicals to be added to the surface of the resin in a suitable state, providing high adhesion between the resin member and the metal layer on the surface of the member, and firmly bonding them.

According to the invention described in claim 2, in the process of imparting hydroxyl groups to resin in a state in which at least some of the atoms constituting the resin have been removed by irradiating the resin with plasma from the plasma side circuit, the timing and state in which ions and radicals act on the resin can be freely adjusted. This allows radicals to be imparted to the surface of the resin in an optimal state, providing high adhesion between the resin member and the metal layer on the member surface, and firmly bonding them together.

According to the invention described in claim 3 , the application time and application timing of the voltage can be appropriately adjusted by a switch for controlling the application of the plasma side voltage on and off, making it possible to appropriately treat the resin surface with simple operations.

According to the invention described in claim 4 , the holding side voltage is applied independently of the plasma side voltage in the process of introducing water vapor gas into the chamber, turning the gas into plasma, and irradiating it onto the surface of the resin. Therefore, when the plasma irradiation device irradiates the plasma onto the surface of the resin, the holding side voltage is used to adjust the potential state of the resin, and the state of approach and separation of ions and radicals from the surface of the resin can be controlled, thereby appropriately controlling the action of ions and radicals on the surface of the resin for each process.

According to the invention described in claim 5 , the plasma generated by applying a positive voltage as a plasma side voltage to the plasma irradiation device can irradiate the surface of the resin with positive ions, and the surface of the resin can be detached by the collision of the ions. In addition, by applying a positive voltage as a holding side voltage to the resin, the potential difference between the plasma irradiation device and the resin can be reduced and the potential difference between the plasma irradiation device and the part other than the resin can be relatively increased, so that the positive ions are attracted to the part other than the resin, and the collision of the ions with the surface of the resin can be prevented from continuing. This makes it possible to appropriately control the processing and surface modification of the resin surface by plasma.

According to the invention described in claim 6 , by applying a holding side voltage to at least a part of the holding section depending on the position where the resin is present, the potential difference between the plasma irradiation device and the resin at the position where the resin is present can be reduced, making it possible to impart radicals to the surface of the resin under more optimal conditions.

1A and 1B are diagrams showing a schematic view of a substrate manufacturing system in which a plasma processing apparatus according to this embodiment is used, in which FIG. 1A is a schematic view seen from a side, and FIG. FIG. 2 is a diagram showing a schematic diagram of the plasma processing apparatus. 4 is a flowchart of processing steps in the above substrate manufacturing system. 4 is a diagram showing a schematic diagram of a state during plasma generation in a second process in the plasma processing apparatus of FIG. 4 is a diagram showing a schematic state after plasma generation in a second process in the plasma processing apparatus shown in FIG.

This embodiment is shown in Figures 1 to 5.

[Configuration of the circuit board manufacturing system]
FIG. 1 is a schematic diagram showing a substrate manufacturing system in which a plasma processing apparatus according to this embodiment is used, where (a) is a schematic diagram seen from a side, and (b) is a schematic diagram seen from above.

This board manufacturing system 100 is a manufacturing system consisting of multiple devices for performing multiple manufacturing processes to manufacture circuit boards with low transmission loss that are compatible with, for example, millimeter waves or microwaves. The board 21 manufactured in the board manufacturing system 100 has a metal layer such as a metal film 23 formed on the front and back surfaces of a resin board body 22, which is the member to be processed.

1, in the substrate manufacturing system 100, the processed member is a substrate body 22 made of a sheet-shaped resin. A metal layer such as a metal film 23 is formed on the surface of this substrate body 22 in the manufacturing process in the substrate manufacturing system 100 to form a substrate 21. The substrate manufacturing system 100 includes vacuum reserve chambers 101 and 102, a first processing chamber 103 for performing a first step S1 and a second step S2 (both described below), a second processing chamber 104 for performing a third step S3 (described below), and gate valves 24, 24, 25, 26, 27, and 28. The first processing chamber 103 includes a pair of vacuum chambers 2 and 2. The vacuum chamber 2 on one side (left side of FIG. 1) constitutes a processing chamber for performing processing on the front side of the substrate body 22, and the vacuum chamber 2 on the other side (right side of FIG. 1) constitutes a processing chamber for performing processing on the back side of the substrate body 22. In this embodiment, the processing performed on the front side and back side of the substrate body 22 and the process for performing the processing are the same. Therefore, the vacuum chamber 2 on one side and the vacuum chamber 2 on the other side have the same configuration and are installed symmetrically from top to bottom.

In addition, in the second processing chamber 104, the front surface processing chamber 105 on one side (left side in FIG. 1) and the back surface processing chamber 106 on the other side (right side in FIG. 1) are for performing the same processing on the front surface side and the back surface side of the substrate body 22, and the same configuration is provided symmetrically from top to bottom. FIG. 1 shows a state in which heaters 29 for the CVD method are provided symmetrically from top to bottom in each of the front surface processing chamber 105 and the back surface processing chamber 106. In addition, instead of the heater 29, a sputtering device (not shown) used for the PVD method (sputtering method) may be provided.

As shown in Fig. 1, the vacuum reserve chamber 101 is provided with a movable part 31 that holds the substrate body 22 at its end and a track part 32a on which the movable part 31 is attached and transported. Similarly, the first processing chamber 103, the second processing chamber 104, and the vacuum reserve chamber 102 are provided with track parts 32b, 32c, 32d, 32e, and 32f that transport the movable part 31 that holds the substrate body 22. The transport method of the substrate body 22 by the movable part 31 and the track parts 32a, 32b, 32c, 32d, 32e, and 32f shown in Fig. 1 is, for example, a linear guide method or a rack and pinion method.
In the fourth step S4 (described later), the substrate body 22 is removed from the substrate manufacturing system 100, and the surface of the substrate body 22 is plated with metal offline (not shown) or a metal foil having a thickness equivalent to the plating is laminated to form a metal layer such as a metal film 23 required for the circuit board.

[Configuration of Plasma Processing Apparatus]
2 is a schematic diagram of the plasma processing apparatus according to this embodiment, showing a first step S1, which will be described later.

The plasma processing apparatus 1 shown in FIG. 2 constitutes the first processing chamber 103 shown in FIG. 1. This plasma processing apparatus 1 irradiates the surface of the resin with plasma to remove at least a portion of the atoms that make up the resin, and then imparts hydroxyl groups to the resin, thereby improving the wettability of the resin surface. The improved wettability makes it possible to strengthen the bond when bonding a metal layer such as a metal film 23 to the surface of the resin.

In addition, in FIG. 2, for the sake of simplicity, only the configuration of the vacuum chamber 2 on one side (the left side in FIG. 1) of the first processing chamber 103 shown in FIG. 1 will be described. In the following description, for the sake of simplicity, except where a particular distinction is required, only the vacuum chamber 2 on one side shown in FIG. 2 will be described, and the description of the vacuum chamber 2 on the other side (the right side in FIG. 1) that processes the back side of the substrate body 22 will be omitted.

The plasma processing apparatus 1 of this embodiment shown in FIG. 2 includes a vacuum chamber 2 and a fine plasma gun.
The plasma gun (hereinafter referred to as “FPG”) 3 includes a holding table 4 as a “holding unit”, a cover 5 , a holding power supply 8 , a plasma power supply 9 , a holding switch 11 , and a plasma switch 12 .

The holding side power supply 8, the holding table 4, and the vacuum chamber 2 form a holding side circuit 13. The plasma side power supply 9, the plasma side switch 12, the FPG 3, and the vacuum chamber 2 form a plasma side circuit 14. The plasma processing device 1 also includes a gas introduction section 15 and an exhaust section 17 having an exhaust pump 16.

Note that FIG. 2 shows a schematic diagram of the scattering directions of ions 7 and radicals 6 inside the vacuum chamber 2. The same is true for FIG. 4, which will be described later. As will be described later, the radicals 6 in this embodiment are hydroxyl radicals. However, the radicals 6 may be any radicals other than hydroxyl radicals.

The vacuum chamber 2 is made of a highly rigid metal such as an aluminum alloy or stainless steel. The vacuum chamber 2 is strong enough not to break even if a pressure difference occurs between the inside and outside of the vacuum chamber when the exhaust pump 16 draws a vacuum, and a box-shaped processing space is formed inside. The processing space of the vacuum chamber 2 is designed so that the gas inside is forcibly exhausted to the outside by the exhaust pump 16, creating a vacuum state. The vacuum chamber 2 is also connected to the ground 10. This ground 10 sets the reference potential for the holding side circuit 13 and the plasma side circuit 14.

The FPG 3 is disposed at the top of the vacuum chamber 2. The FPG 3 converts the process gas introduced into the vacuum chamber 2 from the gas introduction section 15 into plasma. For example, the FPG 3 may be one described in International Publication No. WO 2014/175702.

As shown in FIG. 1, FPGA 3 has a first FPGA 3a and a second FPGA 3b.

The first FPG 3a is configured to rotate about a rotation axis (not shown) so as to change the plasma irradiation direction along the transport direction (left-right direction in FIG. 1) of the substrate body 22. The first FPG 3a is used in the first step S1 described below.

The second FPG3b does not have a rotation axis and irradiates plasma in only one direction. The second FPG3b is used in the second step S2 described below.

The second FPG 3b may be configured to have a rotation axis (not shown) and change the direction of plasma irradiation to the transport direction of the substrate body 22, or the first FPG 3a may be configured not to have a rotation axis (not shown) and to irradiate plasma in only one direction.

The holding table 4 is installed below the FPG 3 so as to face the FPG 3. The holding table 4 is made of metal or an electrode, and holds the substrate body 22.

In this embodiment, the holding table 4 receives a holding-side voltage (described below) from the holding-side power supply 8 in the second step S2 described below.

In the first step S1 and the second step S2, the holding table 4 receives a holding-side voltage (described later) from the holding-side power source 8 at least in a portion depending on the position where the substrate body 22 is present. For example, in the second step S2, the holding table 4 may be configured so that the holding-side voltage is applied to the side of the holding table 4 near the second FPGA 3b (the right side in FIG. 1). In order to apply the holding-side voltage in this manner, the holding table 4 may be configured to apply the holding-side voltage only to a portion of the holding table 4, for example, to form a first conductive range (not shown) near the first FPGA 3a and a second conductive range (not shown) near the second FPGA 3b, and to be provided with a switch (not shown) that selectively switches the current from the holding-side power source 8 between the first conductive range (not shown) and the second conductive range (not shown). However, the position or range of the holding table 4 to which the holding-side voltage is applied may be switched or changed by any other configuration.

The application position and range of the holding side voltage to the holding table 4 in the first step S1 and the second step S2 may be any, and the holding side voltage may be applied to the entire holding table 4 in both the first step S1 and the second step S2.

The cover 5 covers the top surface of the holding table 4. The cover 5 is made of the same material as the substrate body 22. It is configured so that plasma is uniformly irradiated from the FPG 3 to the substrate body 22. Without the cover 5, the plasma from the FPG 3 would also be irradiated to the metallic holding table 4, processing the metal parts, and the particles removed would adhere to the substrate body 22, causing contamination. The cover 5 is necessary to prevent this contamination. Note that when the effect of the particles is small, omitting the cover 5 will not affect the present invention.

The holding side power supply 8 is a DC power supply. The positive electrode of the holding side power supply 8 is connected to the holding table 4 side, and the negative electrode is connected to the vacuum chamber 2 side, and applies a holding side voltage, which is a DC voltage, to the holding side circuit 13.

The plasma side power supply 9 is a DC power supply. The plasma side power supply 9 has a positive electrode connected to the holding table 4 side and a negative electrode connected to the vacuum chamber 2 side, and applies a plasma side voltage, which is a DC voltage, to the plasma side circuit 14. In order to emit plasma from the FPG 3, it is desirable that the plasma side power supply 9 has a larger output than the holding side power supply 8 and can apply a higher voltage to the plasma side circuit 14 than the holding side power supply 8.

The holding side switch 11 and the plasma side switch 12 are switches that switch the current flowing through the circuits between ON and OFF. The holding side switch 11 switches the current flowing through the holding side circuit 13 between ON and OFF, and the plasma side switch 12 switches the current flowing through the plasma side circuit 14 between ON and OFF.

The holding side switch 11 is selectively connected to the conducting side conductor 18 and the non-conducting side conductor 19. The conducting side conductor 18 is electrically connected to the holding side power supply 8, and the holding side circuit 13 is turned ON when the holding side switch 11 is connected, and the voltage of the holding side power supply 8 is applied to the holding base 4. The non-conducting side conductor 19 is electrically connected to the holding base 4 without passing through the holding side power supply 8, and the holding side circuit 13 is turned OFF when the holding side switch 11 is connected, and the potential of the holding base 4 becomes equal to the potential of the ground 10.

The holding side switch 11 and the plasma side switch 12 may be adapted to adjust the flow rate of the current through the circuit from 0 to a maximum in a stepwise or stepless manner. The holding side switch 11 and the plasma side switch 12 may be adapted to be switched ON/OFF by a control device such as a microcomputer (not shown), or may be adapted to be switched ON/OFF manually by an operator.

The gas inlet 15 is a metal pipe that introduces the gases used in the first step S1 and second step S2 described below into the vacuum chamber 2.

The exhaust section 17 is a metal pipe with an exhaust pump 16 installed midway. When the exhaust pump 16 is operated, the exhaust section 17 exhausts various gases, particles, dust, etc. present in the vacuum chamber 2 to the outside.

[Board body]
In this embodiment, the resin constituting the substrate body 22 is not particularly limited as long as it has a hydrophobic surface, and examples thereof include fluororesins such as PTFE, PFA, and PCTFE, polyimide, and LCP. Specifically, in the case of fluororesins, the resin as the material of the substrate body 22 contains fluorine and carbon, and the atoms that are removed from the hydrophobic surface of the resin are mainly fluorine and carbon. By providing hydroxyl groups to the activated surface after the molecular bonds are broken, the hydrophobic surface of the fluororesin can be made highly hydrophilic. In addition, this phenomenon occurs only on the resin surface, and the base material of the resin containing fluorine underneath has high insulation, low relative dielectric constant and dielectric loss tangent, and low signal transmission loss, making it excellent as an electric substrate.

In addition to the above materials, the resin used as the material for the substrate body 22 may also contain fully aromatic polyester, and the atom that is released from the hydrophobic surface of the resin may be oxygen.

[plasma]
In this embodiment, the plasma generated from the FPG 3 preferably contains at least one of nitrogen and argon. It may be a mixed gas of nitrogen and argon. This is because atoms constituting the resin used as the material of the substrate body 22 are easily desorbed from the surface of the resin by ions of nitrogen or argon.

[Processing steps]
3 is a flowchart of the processing steps in substrate manufacturing system 100 according to this embodiment. The substrate manufacturing steps according to this embodiment will be described below with reference to this flowchart.

[First step]
In the substrate manufacturing system 100, first, in the first step (step S1, hereinafter referred to as "first step S1"), ions are irradiated onto the surface of the substrate body 22, which is the member to be processed, to break the molecular bonds on the substrate surface and cause at least a portion of the resin atoms that make up the substrate to be detached.

Prior to the first step S1, the gate valve 24 shown in FIG. 1 is opened, and the movable part 31 holding the end of the substrate body 22 is attached to the track part 32a in the vacuum reserve chamber 101. The gate valve 24 is closed, and the pressure inside the vacuum reserve chamber 101 is reduced. When the pressure inside the vacuum reserve chamber 101 becomes 10 Pa or less, the gate valve 25 is opened.

After opening the gate valve 25, the movable part 31 is moved into the vacuum chamber 2 of the first processing chamber 103, and the gate valve 25 is closed. At this time, the holding side switch 11 and the plasma side switch 12 are both OFF, and neither the holding side circuit 13 nor the plasma side circuit 14 is energized. As described above, when the holding side switch 11 is OFF, the holding side switch 11 is connected to the non-energized side conductor 19, and the potential of the holding table 4 is equal to the potential of the ground 10.

In the first step S1, the hydrophobic surface of the substrate body 22 (the upper surface side in FIG. 1a) is irradiated with plasma from the first FPGA 3a to remove at least some of the atoms of the resin that constitutes the substrate body 22 from the surface of the substrate body 22. That is, in the first step S1, the hydrophobic surface of the substrate body 22 is activated by using plasma, particularly ions in the plasma, to activate the surface of the resin that constitutes the substrate body 22.

Specifically, while the pressure inside the vacuum chamber 2 is reduced by the exhaust pump 16, nitrogen and argon process gases are introduced into the vacuum chamber 2 from the gas inlet 15, and the pressure inside the vacuum chamber 2 is adjusted to a predetermined pressure, for example, 0.3 Pa in the range of 0.1 Pa to 0.4 Pa.

In this state, as shown in FIG. 2, when the plasma side switch 12 is turned on and the plasma side circuit 14 is energized, a second DC voltage is applied from the plasma side power supply 9 to the first FPG 3a, and plasma of the processing gas is generated in the first FPG 3a. The second FPG 3b is used in the second step S2 described below, so it is not energized in this step and no plasma is generated.

At this time, if the pressure inside the vacuum chamber 2 is too high (for example, if it exceeds 0.4 Pa), the processing gas will enter a glow discharge state, and the direction of travel of the ions 7 and radicals 6 in the plasma cannot be controlled. In contrast, if the pressure inside the vacuum chamber 2 is within an appropriate range, the processing gas will be maintained in a dark discharge state, and the direction of travel of the ions 7 and radicals 6 can be controlled. Therefore, the pressure inside the vacuum chamber 2 is adjusted to, for example, 0.1 Pa or more and 0.4 Pa or less. It should be noted that a pressure of about 0.3 Pa is preferable for the pressure inside the vacuum chamber 2.

The first FPG 3a generates plasma of the processing gas filled in the vacuum chamber 2, and as shown in FIG. 2, these become directional ions and radicals that are irradiated onto the substrate body 22. At this time, the ions generated have positive polarity, and the radicals are non-polar.

2, the generated ions 7 and radicals 6 collide with the substrate body 22, and the atoms of the resin constituting the substrate body 22 are detached from the surface of the substrate body 22 mainly due to the impact of the collision of the ions 7. Most of the detached atoms are exhausted from the exhaust section 17 to the outside of the vacuum chamber 2 by the exhaust of the exhaust pump 16. Some of the detached atoms float in the vacuum chamber 2, or after floating, adhere to the inner wall of the vacuum chamber 2 or to components in the vacuum chamber 2. However, in this embodiment, since the pressure in the vacuum chamber 2 is lower than the general glow discharge conditions, there are almost no impurities (such as particles) floating in the chamber 2. Therefore, it is possible to prevent impurities from adhering to the surface of the substrate body 22 and contaminating it.

[End of first process]
When the first step S1 is to be ended, the plasma-side switch 12 is turned OFF to release the current flowing to the plasma-side circuit 14. This ends the generation of plasma of the process gas by the first FPGA 3a.

[Electrical state after completion of the first process]
During the period from the end of the first step S1 to the start of the second step S2 described below, the holding-side switch 11 is connected to the current-carrying conductor 18 and turned ON to energize the holding-side circuit 13. This causes a holding-side voltage from the holding-side power supply 8 to be applied to the holding table 4 and the substrate body 22 on the holding table 4. The holding-side voltage is applied to a first conductive range (not shown) near the first FPGA 3a. At this time, it is desirable for the holding-side power supply 8 to apply a voltage to the holding-side circuit 13 that is 40% or more of the voltage of the plasma-side power supply 9 but smaller than the voltage of the plasma-side power supply 9.

A positive voltage is applied as a holding side voltage to the holding table 4 and the substrate body 22 on the holding table 4 which constitute the holding side circuit 13. On the other hand, the wall surface of the vacuum chamber 2 which constitutes the holding side circuit 13 is at a lower potential than the holding table 4 and the substrate body 22. The first FPG 3a is on the positive side, and the opposing holding table 4 is also on the positive side, and since the voltages of the two are close, plasma generation in the first FPG 3a is unlikely to occur. By applying a holding side voltage from the holding side power supply 8 between the end of the first step S1 and the start of the second step S2 described below, it is possible to create an environment in which plasma generation in the first FPG 3a is likely to occur.

[Second step]
When a second step (step S2, hereinafter referred to as "second step S2") is performed in the vacuum chamber 2 after the first step S1, the following procedure is followed.

In this embodiment, the first step S1 and the second step S2 are performed in the same vacuum chamber 2, thereby simplifying the processing steps and miniaturizing the apparatus. However, the vacuum chamber 2 in which the first step S1 is performed and the vacuum chamber (not shown) in which the second step S2 is performed may be provided separately. By providing the vacuum chamber 2 in which the first step S1 is performed and the vacuum chamber (not shown) in which the second step S2 is performed separately, it is possible to easily prevent a situation in which the desorbed components adhere to the surface of the substrate body 22 in the second step S2, even if the desorbed components are floating in the vacuum chamber 2, which have desorbed from the surface of the substrate body 22 in the first step S1.

In this embodiment, after the first step S1, the exhaust pump 16 properly removes the desorbed components from within the vacuum chamber 2, thereby preventing floating matter from the first step S1 from affecting the second step S2.

After the first step S1 is completed, the substrate body 22 is maintained in a state held on the holding table 4 within the vacuum chamber 2.

Next, the exhaust pump 16 continues to operate to maintain the reduced pressure state in the vacuum chamber 2. If the supply of nitrogen and/or argon used in the first step S1, which is present in the vacuum chamber 2, is stopped, the exhaust pump 16 immediately discharges it out of the vacuum chamber 2. Then, while introducing water vapor, which is the processing gas, into the vacuum chamber 2 from the gas inlet 15, the exhaust pump 16 is controlled to adjust the pressure in the vacuum chamber 2 in the second step S2 so that the pressure in the vacuum chamber 2 is 30% to 50% of the pressure in the first step S1. This is because by performing the processing in the second step S2 described later at a pressure of 30% to 50% of the pressure in the first step S1, radicals 6 (hydroxyl radicals) can be optimally attached to the surface in the plasma of the processing gas.

After the processing gas is introduced into the vacuum chamber 2, as shown in FIG. 4, the holding side switch 11 is switched from a state connected to the non-conductive side conductor 19 to a state connected to the conductive side conductor 18 to turn on the holding side circuit 13, and the voltage of the holding side power supply 8 is applied to the holding table 4. The holding side voltage is applied to a second conductive range (not shown) near the second FPG 3b. Note that the processing gas may be introduced into the vacuum chamber 2 after the holding side circuit 13 is turned on, or at the same time as the holding side circuit 13 is turned on. Next, the plasma side circuit 14 is turned on, and electricity is applied from the plasma side power supply 9 to the FPG 3. As shown in FIG. 1, the second FPG 3b is activated by applying the plasma side voltage to the second FPG 3b, and plasma of the processing gas filled in the vacuum chamber 2 is generated.

At this time, it is preferable that the first DC voltage applied from the holding side power supply 8 to the holding table 4 is smaller than the second DC voltage applied from the plasma side power supply 9 to the second FPG 3b. Specifically, it is more preferable that the first DC voltage from the holding side power supply 8 is 40% or more of the second DC voltage applied from the plasma side power supply 9 to the second FPG 3b, and is smaller than the second DC voltage.

The holding side power supply 8 applies a positive voltage to the holding table 4 and the substrate body 22, and the plasma side power supply 9 applies a positive voltage to the second FPG 3b. The potentials of the second FPG 3b and the holding table 4 are each formed in the positive direction, while the potential of the vacuum chamber 2 (forming the plasma side circuit 14 and the holding side circuit 13) relative to the second FPG 3b and the holding table 4 is formed in the negative direction. Also, while the potential difference between the second FPG 3b and the holding table 4 is decreasing, the potential differences between the FPG 3 and the vacuum chamber 2 and between the holding table 4 and the vacuum chamber 2 are increasing.

In this state, when plasma is generated in the process gas in the vacuum chamber 2 by the second FPG 3b, most of the positive ions 7 in the plasma move in the direction of the vacuum chamber 2, where the potential difference is greater, as shown in FIG. 5. Meanwhile, the non-polar radicals 6 (hydroxyl radicals) in the plasma are irradiated to the substrate body 22.

By irradiating the substrate body 22 with radicals 6 (hydroxyl radicals), hydroxyl groups are introduced to the surface of the substrate body 22. Moreover, since the ions 7 move toward the wall surface of the vacuum chamber 2 and the substrate body 22 is hardly irradiated with ions 7, the hydroxyl groups introduced to the surface of the substrate body 22 by the impact of the ions are prevented from being detached again. In this way, stable hydrophilicity is imparted to the surface of the substrate body 22. The introduction of hydroxyl groups causes the hydroxyl groups to chemically bond stably with the surface of the substrate body 22. The amount of bonding increases with the irradiation time until there are no more reactive groups. As the number of hydroxyl groups increases, the contact angle decreases.

The surface of the substrate body 22 on which hydroxyl groups have been introduced by the second step S2 should preferably have a contact angle with water of 10° or less, more preferably 6° or less, and an appropriate irradiation time is set. In this way, the surface of the substrate body 22 and the metal film 23 will be firmly attached to each other in the third step S3 and fourth step S4 described below.

[Pressure and temperature in the first and second steps]
It is preferable that both the first step and the second step are performed in a state where the inside of the vacuum chamber 2 is depressurized. It is also preferable that the second step is performed after the first step while maintaining the depressurized state. This is because hydroxyl groups can be introduced into the surface of the resin constituting the substrate body 22 while maintaining the activated state of the surface of the resin constituting the substrate body 30 in the first step. It is also preferable that the surface of the resin that has undergone the second step is maintained hydrophilic for a long period of time, for example, for one month or more. Therefore, the substrate body 22 may be released to atmospheric pressure immediately after the second step.

It is preferable that the first step S1 is performed at a first pressure of 0.1 Pa or more and 0.4 Pa or less, and the second step S2 is performed at a second pressure of 30% or more and 50% or less of the first pressure. This is because in the first step S1, it is easy to control the way in which the ions and radicals in the plasma move, and in the second step, the surface of the substrate body 22 is hardly irradiated with ions, and hydroxyl radicals are easily irradiated with the surface of the substrate body 22.

The second step S2 is preferably performed with the temperature of the substrate body 22 set to 150°C or higher and 300°C or lower. This is because the chemical reaction between the hydroxyl groups and the surface of the resin that constitutes the substrate body 22 is promoted, and the hydroxyl groups are firmly introduced into the surface that constitutes the substrate body 22.

[Electrical state after second process]
In the second step S2, even after the plasma-side power supply 9 is turned OFF and the application of the second DC voltage to the second FPG 3b is stopped, it is desirable to keep the holding-side switch 11 connected to the energized-side conductor 18 and the holding-side circuit 13 ON, as shown in Fig. 5. When the holding-side circuit 13 is turned ON, a positive voltage is applied from the holding-side power supply 8 to the holding table 4 and the substrate body 22, and the holding-side circuit 13 has a positive potential on the holding table 4 side and a negative potential on the vacuum chamber 2 side, so that the positive ions in the vacuum chamber 2 are attracted to the wall side of the vacuum chamber 2, which has a large potential difference. As a result, even after the plasma-side power supply 9 is turned OFF, the hydroxyl groups introduced to the surface of the substrate body 22 by the impact of the ions are prevented from being detached again. In addition, the application of a positive voltage from the holding-side power supply 8 to the holding table 4 and the substrate body 22 can also attach the remaining hydroxyl groups by a slight glow discharge generated on the holding table 4.

In the second step S2, the length of time for which the holding-side circuit 13 is kept ON after the plasma-side power supply 9 is turned OFF may be any length. Specifically, it may be any length of time that the holding-side power supply 8 applies the holding-side voltage to the holding table 4 and the substrate body 22 longer than the time for which the plasma-side power supply 9 applies the plasma-side voltage to the right-side FPG 3, and that is sufficient to prevent the detachment of the surface of the substrate body 22 caused by ions from progressing.
In this description, for ease of understanding, the first FPG 3a is used for the first step S1, and the right-side FPG 3 is used for the second step S2. However, the second FPG 3b may be used for the first step S1. In this case, it is preferable that the plasmas generated from the first FPG 3a and the second FPG 3b are parallel to each other so as not to interfere with each other. In addition, in the holding table 4 facing the second FPG 3b for the second step S2, it is better to apply a positive voltage to the range facing the second FPG 3b rather than to the entire surface of the holding table 4 (i.e., it is preferable to form the above-mentioned second conductive range (not shown) in a range approximately equal to the range facing the second FPG 3b). By configuring in this way, it is possible to prevent a change in the process environment due to discharge by the holding table 4 in the part not facing the second FPG 3b. When the second FPGA 3b is swung depending on the position of the substrate main body 22, the position of the corresponding holder 4 changes, so it is desirable to change the range applied to the holder 4 (the above-mentioned second conductive range (not shown)) depending on the irradiation position of the second FPGA 3b. Similarly, when the first FPGA 3a is swung, it is desirable to change the range applied to the holder 4 (the above-mentioned first conductive range (not shown)) depending on the irradiation position of the first FPGA 3a.

[Third step, fourth step]
After the second step S2, the gate valve 26 is opened, and the substrate body 22 is accommodated in the second processing chamber 104 where the third step is performed. The switch 11 is connected to the non-conductive side conductor 19, and the holding side circuit 13 is turned OFF.

In the second processing chamber 104, the substrate body 22 is subjected to processing in a third step (step S3, hereinafter referred to as "third step S3").

In the third step S3, a metal film 23 is deposited on the surface of the substrate body 22 that has been subjected to the first step S1 and the second step S2. The deposition of the metal film 23 is performed by, for example, a CVD method (chemical vapor deposition method) or a PVD method (sputtering method). Examples of the metal film 23 include a copper film, a silver film, and a gold film. Fig. 1 shows a state in which a heater 29 for the CVD method is provided in the second processing chamber 104.
After the third step S3 is completed, the gate valve 27 is opened, the movable part 31 is moved into the vacuum reserve chamber 102, and the gate valve 27 is closed. After the pressure inside the vacuum reserve chamber 102 is returned to atmospheric pressure, the gate valve 38 is opened and the completed substrate 21 is removed.

In the fourth step (step S4, hereafter referred to as "fourth step S4"), the substrate is removed from the substrate manufacturing system 100, and metal plating and thermocompression bonding are performed offline on the surface of the substrate body 22. The metals used for plating and thermocompression bonding in the fourth step S4 are the same as those used in the third step S3, such as copper, silver, or gold.

Although the fourth step S4 may be performed independently without performing the third step S3, it is preferable to perform it after forming the metal film 23 on the surface of the substrate body 22 in the third step S3. If the metal film is vapor-deposited in the third step S3, in the fourth step S4, the same metal is further bonded by plating or thermocompression bonding to form a metal layer such as the metal film 23 on the surface of the substrate body 22.

In addition, in the second processing chamber 104, after the third step S3, the fourth step S4 may be performed in a vacuum without removing the substrate from the substrate manufacturing system 100. In this case, a metal foil is formed on the metal film 23 formed on the substrate body 22 in the third step S3. Since the entire process is performed in a vacuum, the Cu film can be adhered to the metal foil without being affected by oxidation due to the atmosphere. This makes it possible to obtain a high degree of adhesion.

[Modification of the substrate body and hydroxyl groups]
In this embodiment, the resin constituting the substrate body 22 may be polytetrafluoroethylene, and the atom substituted with the hydroxyl group in the second step S2 may be fluorine. Also, the resin constituting the substrate body 22 may be a liquid crystal polymer containing a wholly aromatic polyester.

[Action and Effect]
As described above, in this embodiment, the time for which the holding circuit 13, which applies a holding voltage as a DC voltage to the substrate body 22, which is the resin to be irradiated with plasma, applies the holding voltage to the resin held on the holding table 4, and the time for which the plasma circuit 14, which is configured to apply a plasma voltage as a DC voltage to the FPG 3, which turns the gas introduced by the gas introduction section 15 into plasma, applies the plasma voltage to the FPG 3 are set to be separate, so that the timing at which the FPG 3 generates ions and radicals to irradiate the resin held on the holding table 4 with the ions and radicals, and the state of the potential around the holding table 4 and the substrate body 22 held by the holding table 4 can be freely adjusted, and the timing and state at which the ions and radicals act on the substrate body 22 while the substrate body 22 is accommodated in the vacuum chamber 2 can be freely adjusted. This allows radicals to be applied to the surface of the substrate body 22 in a suitable state, and a high adhesive force is imparted between the substrate body 22 and a metal layer such as the metal film 23 on the surface of the substrate body 22, thereby firmly bonding them together.

In this embodiment, in the process of imparting hydroxyl groups to the substrate body 22 in a state in which at least some of the atoms constituting the substrate body 22 have been removed by irradiating the substrate body 22 with plasma from the plasma side circuit 14, the timing and state in which ions and radicals act on the substrate body 22 can be freely adjusted. This allows the radicals to be imparted to the surface of the substrate body 22 in an optimal state, providing high adhesion between the resin substrate body 22 and a metal layer such as the metal film 23 on the surface of the substrate body 22, and firmly bonding them together.

In this embodiment, the plasma side switch 12, which serves as the application time adjustment unit of the plasma side circuit 14, is turned on and off to set the time during which the plasma side circuit 14 applies the plasma side voltage to the holding table 4 shorter than the time during which the holding circuit 13 applies the holding side voltage to the holding table 4. This generates a potential difference between the periphery of the substrate body 22 held on the holding table 4 and the portion of the vacuum chamber 2 other than the periphery of the substrate body 22, even before and after the plasma irradiation process by the FPG 3, and makes it possible to easily control the distribution state of ions and radicals in the vacuum chamber 2 for a long period of time. This allows various types of radicals to be applied to the surface of the substrate body 22 in an appropriate state, providing a high adhesion force between the substrate body 22 and a metal layer such as the metal film 23 on the surface of the substrate body 22, and allowing them to be firmly bonded.

In this embodiment, the plasma side switch 12, which controls the application of the plasma side voltage on and off, appropriately adjusts the voltage application time and application timing, making it possible to appropriately process the surface of the substrate body 22 with simple operations.

In this embodiment, the holding side voltage is applied during the process of introducing gas into the vacuum chamber 2, turning the gas into plasma, and irradiating the surface of the substrate body 22. When the FPG 3 irradiates the surface of the substrate body 22 with plasma, the holding side voltage adjusts the potential state of the substrate body 22, controlling the approach and separation state of ions and radicals to and from the surface of the substrate body 22, thereby appropriately controlling the action of ions and radicals on the surface of the substrate body 22 for each process.

In this embodiment, a positive voltage is applied to the FPG3 as a plasma-side voltage to generate plasma, which irradiates the surface of the resin with positive ions, and the surface of the resin can be detached by ion collision. In addition, by applying a positive voltage to the resin as a retention-side voltage, the potential difference between the FPG3 and the resin is reduced and the potential difference between the FPG3 and parts other than the substrate body 22 is relatively increased, so that the positive ions are attracted to parts other than the substrate body 22, and the continued collision of ions with the surface of the substrate body 22 can be prevented. This makes it possible to appropriately control the processing and surface modification of the surface of the substrate body 22 by plasma.

In this embodiment, by applying a holding side voltage to at least a portion of the holding table 4 that depends on the position where the substrate body 22 is present, the potential difference between the FPG 3 and the substrate body 22 at the position where the substrate body 22 is present can be reduced, making it possible to impart radicals to the surface of the substrate body 22 under more optimal conditions.

It goes without saying that the above embodiment is an example of the present invention, and does not mean that the present invention is limited to only the above embodiment. In other words, various modifications and applications of the present embodiment are possible as long as they are suitable for solving the problems of the present invention.

The plasma processing apparatus and plasma processing method of this embodiment are used, for example, in the manufacture of circuit boards for use in mobile phones that communicate large volumes of information at high speed. Since fluororesin has the second lowest dielectric constant after air, fluororesin boards are particularly suitable as materials for high-frequency boards. Compared to circuit boards made of other common materials, circuit boards made of fluororesin have a low dielectric constant and dielectric tangent, and low dielectric loss, even when high-frequency current is passed through them.

When the plasma processing apparatus and plasma processing method of this embodiment are applied to the manufacture of fluororesin substrates, the hydrophilicity of the manufactured substrate is improved, and adhesion to copper wiring is improved, providing a circuit substrate that can withstand use in high frequency bands. This technology that can be applied to use in high frequency bands can be applied not only to mobile phone bodies, but also to substrates used in mobile phone base stations, substrates for communication in the home, factory, or for a specific region, or substrates for millimeter wave radars used in autonomous driving of automobiles or drones. The plasma processing apparatus and plasma processing method of this embodiment can also be used to manufacture substrates in a variety of fields other than those mentioned above.

1: Plasma processing apparatus 2: Vacuum chamber (chamber)
3...FPG (plasma irradiation device)
3a...First FPG (plasma irradiation device)
3b: Second FPG (plasma irradiation device)
4... Holding stand (holding part)
13: Holding side circuit 14: Plasma side circuit 15: Gas inlet 22: Substrate body (resin)

Claims (7)

A plasma processing apparatus for irradiating a surface of a resin present in a chamber with plasma to improve wettability of the surface of the resin, comprising:
a holding circuit having a holding portion for holding the resin to be irradiated with the plasma, the holding circuit applying a holding voltage to the held resin;
a gas inlet for introducing a gas into the chamber;
A plasma irradiation device is provided for converting the gas into plasma, and a plasma side circuit is provided for applying a plasma side voltage as a DC voltage to the plasma irradiation device,
The holding-side circuit is set so that a time for applying the holding-side voltage to the resin and a time for applying the plasma-side voltage to the plasma irradiation device by the plasma-side circuit are separate ,
The plasma processing apparatus is characterized in that the plasma side circuit is provided with an application time adjustment unit for setting the time during which the plasma side circuit applies the plasma side voltage to be shorter than the time during which the holding side voltage is applied to the holding side circuit . The plasma processing apparatus according to claim 1, characterized in that the plasma side circuit is set so that the time for applying the holding side voltage and the time for applying the plasma side voltage are separate for the process of imparting hydroxyl groups to the resin in a state in which at least some of the atoms constituting the resin have been released by irradiating the resin with plasma by the plasma side circuit. 3. The plasma processing apparatus according to claim 1, wherein the application time adjustment unit of the plasma side circuit is a switch for controlling on/off application of the plasma side voltage to the plasma irradiation device. 4. The plasma processing apparatus according to claim 1, wherein the holding side circuit applies the holding side voltage independently of the plasma side circuit during the process of introducing the gas into the chamber, converting the gas into plasma, and irradiating the gas onto the surface of the resin . 5. The plasma processing apparatus according to claim 1, wherein the plasma side circuit applies a positive voltage of the plasma side voltage to the plasma irradiation device, and the holding side circuit applies a positive voltage of the holding side voltage to the resin . 6. The plasma processing apparatus according to claim 1 , wherein the holding circuit applies the holding voltage to at least a part of the holding portion depending on a position where the resin is present. a chamber for accommodating a resin to be irradiated with plasma;
a holding circuit having a holding portion for holding the resin to be irradiated with the plasma, the holding circuit applying a holding voltage to the held resin;
a gas inlet for introducing a gas into the chamber;
A plasma irradiation device is provided for converting the gas into plasma, and a plasma side circuit is provided for applying a plasma side voltage as a DC voltage to the plasma irradiation device,
A plasma processing method for improving wettability of a surface of a resin present in the chamber by irradiating the surface of the resin with plasma, the method comprising:
The holding-side circuit is set so that a time for applying the holding-side voltage to the resin and a time for applying the plasma-side voltage to the plasma irradiation device by the plasma-side circuit are separate ,
The plasma processing method is characterized in that the plasma side circuit is provided with an application time adjustment unit for setting the time during which the plasma side circuit applies the plasma side voltage to be shorter than the time during which the holding side voltage is applied to the holding side circuit .

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