Plating apparatus for reduced pressure plating and reduced pressure plating method

Abstract

Provided is a technology with which the effects of air bubbles and the like can be minimized in the plating of minute vias and trenches, and with which a plurality of plating treatments can be handled with a single plating device. This plating device for a reduced-pressure plating treatment comprises: a plating tank comprising an opening part provided with a seal that prevents leaks of a plating liquid, and a liquid supply part and a liquid discharge part for the plating liquid; a plating tank rotation means; a tank inner pressure reduction means for reducing the pressure of a tank inner space; and an object-to-be-plated back surface pressing cover comprising a back surface pressure reduction means that presses the periphery of an object to be plated placed on the opening part and reduces the pressure of a back surface space formed on the side of a back surface of the object to be plated. The plating device is characterized in that: the tank inner pressure reduction means comprises a pressure-reducing pocket provided on a plating tank inner wall that, when the plating tank is rotated so that the object to be plated is oriented in an inclined posture, is positioned at a top side of the inclined posture, a pressure-reducing pipe connected to a discharge port of the pressure-reducing pocket, and a liquid discharge pipe for discharging the plating liquid remaining in the pressure-reducing pipe; and the pressure-reducing pipe extends from the pressure-reducing pocket toward a plating tank center direction.

Description

[Technical Field]

[0001] The present invention relates to a plating apparatus for plating objects such as semiconductor wafers and printed wiring boards, and more particularly to a plating apparatus capable of reducing pressure during plating and a reduced-pressure plating method using the same. [Background technology]

[0002] In recent years, various plating processes have been performed on substrates such as semiconductor wafers and printed wiring boards. Recently, electronic substrates have become lighter, thinner, shorter, and smaller, creating a strong demand for fine plating processes. For example, in substrates such as semiconductor wafers, there is a demand for filling minute vias with plating. Furthermore, the aspect ratio of these vias is steadily increasing.

[0003] It is generally known that air bubbles in the plating solution or on the surface to be plated can cause plating defects. When performing plating processes such as filling minute vias, the presence of air bubbles in or around the vias can easily cause plating defects, making it impossible to perform the desired plating process.

[0004] The following prior art has been proposed as a countermeasure against bubbles in such plating solutions. One of these methods involves degassing the dissolved oxygen in a plating pretreatment solution using a degassing device that uses a degassing membrane module and a vacuum pump, pretreating the object to be plated with the degassed pretreatment solution, and then performing electrolytic or electroless plating (see, for example, Patent Document 1). Patent Document 1 also proposes immersing the object to be plated in the degassed plating solution to perform electrolytic or electroless plating.

[0005] In addition, in a jet-type plating apparatus in which plating is performed with the plating surface of the object to be plated facing downward, a pretreatment process has been proposed in which the object to be plated is placed on top of a pretreatment tank, the object to be plated is heated, the pressure in the pretreatment tank is reduced to 9 hPa to 40 hPa, and water at 10°C to 30°C is supplied into the pretreatment tank to replace the gas in the pretreatment tank with vaporized water, the pretreatment tank is filled with water, the water is brought into contact with the surface to be plated, and then air is introduced into the pretreatment tank to restore atmospheric pressure, causing the water to adhere to the surface to be plated (for example, Patent Document 2).Furthermore, as a method for infusing various liquids such as plating solution into fine depressions, a plating apparatus has been proposed that includes a pressure control means for reducing the pressure in a liquid storage unit consisting of a semiconductor wafer and a cap, and a vacuum chuck for reducing the pressure on the backside of the wafer (Patent Document 3).

[0006] In addition, in a jet-type plating apparatus, a plating tank having an opening with a liquid seal to prevent leakage of plating solution when an object to be plated is placed thereon, a liquid supply section for supplying plating solution and a liquid discharge section for discharging plating solution, and an anode configured to face the object to be plated, has also been proposed in which the plating tank is provided with a rotation means for rotating the plating tank itself (for example, Patent Document 4).

[0007] The plating techniques in the above-mentioned prior arts are capable of performing satisfactory plating for filling small vias to a certain extent, trenches between fine wiring, etc. However, with the recent trend toward lighter, thinner, shorter, and smaller electronic substrates, for example, vias are becoming increasingly smaller, and the current situation is that there is a demand for plating techniques that can reliably perform satisfactory plating for fine vias with high aspect ratios, such as vias with a diameter of 5 μm and a depth of 100 μm.

[0008] Furthermore, it is known that, for example, in addition to copper via-hole filling plating, multiple plating processes using nickel, palladium, gold, etc. are performed on substrates such as semiconductor wafers and printed wiring boards. Various plating methods, such as electrolytic plating and electroless plating, are used for these multiple plating processes. Therefore, when multiple plating processes are performed on a substrate, the current practice is to prepare plating apparatuses corresponding to each type of plating process, transport the substrate to each plating apparatus, and perform each plating process.

[0009] In this way, when multiple plating processes are performed on a plated object, plating equipment corresponding to each type of plating process is prepared, but this approach results in an increase in the size of the manufacturing equipment, increases manufacturing costs, and is insufficient for efficient manufacturing. Therefore, if multiple plating processes could be performed with a single plating equipment, space savings in the manufacturing equipment could be achieved and efficient manufacturing could be realized, and it is hoped that such a general-purpose plating equipment will be realized. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 4043192 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-47391 [Patent Document 3] JP 11-87273 [Patent Document 4] Patent No. 3513130 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in light of the above circumstances, and provides a plating technology that can reliably plate minute vias and trenches formed on the plating surface of a workpiece while minimizing the effects of bubbles, etc., and also provides a plating technology that can handle multiple plating processes using a single plating device. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a plating apparatus for reduced-pressure plating treatment, which comprises: a plating tank having an opening with a seal to prevent leakage of plating solution when an object to be plated is placed therein; a liquid supply section for supplying plating solution and a liquid discharge section for discharging plating solution; a rotation means for rotating the plating tank itself; an internal tank decompression means for decompressing the space within the tank formed by the plating surface of the object to be plated placed in the opening and the plating tank; and a plated object back surface pressing cover equipped with a back surface decompression means for pressing the periphery of the object to be plated placed in the opening and decompressing the space formed on the back surface of the object to be plated, which is the back surface of the object to be plated. The internal tank decompression means comprises a decompression pocket provided in the inner wall of the plating tank located above the inclined position when the plating tank is rotated to place the object in an inclined position; a decompression pipe connected to the exhaust port of the decompression pocket; and a liquid discharge pipe for discharging plating solution remaining in the decompression pipe, the decompression pipe extending from the decompression pocket toward the center of the plating tank. According to the present invention, air bubbles in the plating solution and air bubbles adhering to the surface of the object to be plated can be reliably removed by reducing the pressure inside the plating tank. This allows the desired plating process to be performed on minute areas on the surface of the object to be plated, such as vias and trenches with a high acceptance ratio of 20 or more, without causing plating defects such as chipped plating.

[0013] The plating apparatus of the present invention reduces the pressure inside the plating tank to -95 to -100 kPa (atmospheric pressure 0, gauge pressure). However, simply reducing the pressure creates a force that draws liquids supplied to the plating tank, such as plating solution, cleaning water, and pretreatment liquid, toward the pressure reduction pipe. If liquids are drawn into the pressure reduction pipe, it becomes difficult to reliably reduce the pressure inside the plating tank. Therefore, to ensure reliable control of the pressure reduction inside the plating tank, the plating apparatus of the present invention rotates the plating tank and tilts the object to be plated, placed in the opening of the plating tank. The object to be plated is initially placed horizontally in the opening of the plating tank with the surface to be plated facing downward. During pressure reduction, the plating tank is rotated by an angle of 100° to 170° so that the surface to be plated faces upward. When the plating tank is rotated in this manner, the plating tank (as well as the object to be plated and the surface to be plated) becomes tilted. In the plating apparatus of the present invention, a pressure reduction pocket is provided on the inner wall of the plating tank that is located above this tilted position. The pressure reduction pipe extends from the pressure reduction pocket toward the center of the plating tank. In other words, when the plating tank is tilted, the pressure reduction pipe is positioned downward from the exhaust port of the pressure reduction pocket, with the pressure reduction pocket on the upper side.

[0014] In the plating apparatus of the present invention, the depressurization operation is performed as follows. First, the object to be plated is placed in the opening, and the plating tank is rotated to a predetermined rotation angle. Then, before supplying liquid such as a plating solution to the plating tank, the tank interior space is depressurized to a predetermined pressure (-95 to -100 kPa). At this time, the rear space formed on the rear side of the object to be plated by the object rear pressure cover is also depressurized (-95 to -100 kPa). Then, liquid is supplied into the plating tank under the depressurized state. This liquid supply continues until it is sucked into the depressurization pipe. After the supply is stopped, the pressure inside the depressurization pipe is returned to atmospheric pressure, and any liquid remaining in the depressurization pipe is discharged through a liquid discharge pipe connected to the depressurization pipe. In the plating apparatus of the present invention, when the plating tank is rotated to an inclined position, the depressurization pipe extends from the exhaust port of the depressurization pocket toward the center of the plating tank, so the depressurization pipe is positioned downward from the exhaust port. Therefore, the liquid supplied to the plating tank remains in the plating tank up to the exhaust port of the pressure reduction pocket, preventing the liquid from being sucked into the pressure reduction pipe due to pressure reduction, and making it possible to reliably reduce the pressure inside the plating tank to a specified level (-95 to -100 kPa).

[0015] In the plating apparatus of the present invention, the internal volume of the plating tank is preferably adjusted so that the plating tank supplies a liquid at a thickness of 2.0 mm to 10.0 mm from the surface of the workpiece to be plated. In the plating apparatus of the present invention, the internal volume of the plating tank is preferably adjusted to ensure depressurization of the internal space of the plating tank. If the internal volume of the tank is too large, it will take a long time to depressurize the pressure to the specified level, resulting in poor work efficiency. If the internal volume of the tank is too small, satisfactory plating processing will likely not be achieved. In the plating apparatus of the present invention, the internal volume of the plating tank is determined by the liquid thickness from the surface of the workpiece to be plated. Specifically, the appropriate internal volume is approximately 32 mL to 153 mL for 6-inch silicon wafers, approximately 57 mL to 284 mL for 8-inch wafers, and approximately 132 mL to 660 mL for 12-inch wafers.

[0016] When implementing the plating apparatus of the present invention, the opening of the plating tank is preferably formed by adhering a sealing member that forms a seal to plating tank components that form the plating tank. The plating apparatus of the present invention reduces the pressure inside the tank, which is formed by the plating tank and the surface of the workpiece placed in the opening. Therefore, it is necessary to prevent liquid leakage at the contact point between the workpiece placed in the opening and the seal of the opening. To reduce the pressure inside the tank to -95 to -100 kPa, it is important to reliably prevent liquid leakage from the seal provided at the opening. Therefore, the opening requires that the sealing member that forms the seal and the plating tank components that form the plating tank are adhered to each other. Adhesion refers to a state in which the sealing member and the plating tank components are liquid-tightly bonded. A plating tank opening in which the sealing member that forms the seal and the plating tank components that form the plating tank are adhered to each other can be achieved by simultaneous casting. This simultaneous casting refers to a casting method in which the plating tank components and the sealing member are placed in a mold for forming the opening and the mold is pressurized to form the opening. Specifically, an adhesive (primer) is applied to the area corresponding to the sealing portion of the opening of a plating tank member previously placed in a mold (the periphery of the opening). A sealing member is then placed in the adhesive-coated sealing portion, and the mold is then compressed. After the sealing member hardens, the mold is removed, and the opening is molded, resulting in a bond between the sealing member and the plating tank member forming the plating tank. An opening formed in such a bonded state can reliably prevent leakage of plating solution from the seal due to reduced pressure within the plating tank. While there are no particular restrictions on the materials used for the plating tank member and the sealing member, considering processability and plating solution resistance, it is preferable to use polyvinyl chloride (PVC) for the plating tank member and silicone for the sealing member. A cathode, which will come into contact with the object to be plated, can be simultaneously molded in the area corresponding to the sealing portion (the periphery of the opening).

[0017] The plating apparatus according to the present invention preferably includes a degassing means for removing dissolved oxygen from the liquid supplied to the plating tank. Liquids supplied to the plating tank, such as plating solutions, cleaning water, and pretreatment solutions, contain a certain amount of dissolved oxygen when in the atmosphere. Therefore, to prevent the generation of bubbles, it is desirable to remove the dissolved oxygen from the liquid in advance. While there are no particular limitations on the degassing means, it is desirable to use a degassing module using hollow fibers.

[0018] The plating apparatus of the present invention preferably includes multiple plating solution storage tanks capable of individually storing two or more types of plating solution, and a plating solution switching device for switching the plating solution supplied to the plating tank. While the plating apparatus of the present invention is capable of plating under reduced pressure, it can also be used under atmospheric pressure. Furthermore, electrolytic plating can be performed by embedding an electrode in the seal of the opening and placing an anode in the plating tank. Therefore, multiple plating processes can be performed by changing the type of plating solution supplied to the plating tank. In this case, providing a plating solution switching device for switching the type of plating solution allows multiple consecutive plating processes. For example, when plating a substrate such as a semiconductor wafer, nickel, palladium, and gold are sometimes plated in this order. This can be achieved by providing three plating solution storage tanks capable of individually storing nickel plating solution, palladium plating solution, and gold plating solution, and switching the plating solution supplied to the plating tank using the plating solution switching device. This is effective for plating a wide variety of products in small quantities, and reduces the installation space required for the plating apparatus.

[0019] The present invention relates to a reduced-pressure plating method in which an object to be plated is placed in an opening of a plating tank, the opening is liquid-tightly sealed with the object to be plated, the peripheral edge of the object to be plated is pressed from the back side of the object to be plated placed in the opening to fix it, the plating tank is rotated to change the position of the object to be plated placed in the opening, plating solution is supplied to fill the plating tank with the plating solution, and the plating solution comes into contact with the object to be plated, the space within the plating tank is depressurized using a depressurization pipe of an internal tank depressurization means, and a back space formed on the back side of the object to be plated that is not to be plated is depressurized, and after the space within the plating tank has been depressurized to a predetermined pressure, the plating solution remaining in the depressurization pipe is discharged through a liquid discharge pipe, and plating is performed.

[0020] In the reduced pressure plating method according to the present invention, it is preferable to degas the liquid to be supplied to the plating tank in advance.

[0021] In the reduced-pressure plating method according to the present invention, it is preferable to perform a plurality of plating processes by replacing the plating solution supplied to the plating tank.

[0022] In the present invention, the plating process can be carried out at atmospheric pressure without reducing the pressure. Therefore, depending on the type of plating solution, the plating process can be carried out at atmospheric pressure or at a low pressure. When multiple plating processes are carried out on an object to be plated, it is preferable to replace the plating solution supplied to the plating tank before carrying out the plating processes.

[0023] The plating apparatus and reduced pressure plating method according to the present invention can be applied to both electrolytic plating and electroless plating. [Effects of the Invention]

[0024] According to the present invention, the effects of air bubbles and the like can be minimized as much as possible on tiny vias and trenches formed on the plating surface of the object to be plated, thereby enabling reliable plating processes, and making it possible to handle multiple plating processes using a single plating device. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a perspective view of a plating apparatus according to an embodiment of the present invention. [Figure 1A] FIG. 2 is a right side view of the plating apparatus according to the present embodiment. [Figure 1B] FIG. 2 is a left side view of the plating apparatus according to the present embodiment. [Figure 1C] FIG. 2 is a front view of the plating apparatus according to the present embodiment. [Figure 1D] FIG. 2 is a plan view of the plating apparatus according to the present embodiment. [Figure 2] FIG. 2 is a perspective view of a plating cell body of the plating device. [Figure 2A] FIG. [Figure 2B] FIG. 2 is a bottom view of the plating cell body of the plating device. [Figure 3] FIG. [Figure 3A] FIG. [Figure 3B] FIG. [Figure 4] FIG. [Figure 5] FIG. 10 is a perspective view of the plating apparatus when draining the liquid. [Figure 6] Schematic diagram of the piping of the plating apparatus of this embodiment [Figure 7] Observation photo of plated via cross section (decompressed) [Figure 8] Observation photo of plated via cross section (atmospheric pressure) DETAILED DESCRIPTION OF THE INVENTION

[0026] An embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a perspective view of a plating apparatus according to this embodiment. Fig. 1A shows a right side view of the plating apparatus, Fig. 1B shows a left side view, Fig. 1C shows a front view, and Fig. 1D shows a plan view.

[0027] The plating apparatus in this embodiment has a plating cell 1 and a pressure lid 2, and the plating cell 1 is provided with an inversion drive mechanism 3. The pressure lid 2 is also provided with a pressure arm 4 for placing the pressure lid 2 on the plating cell 1 and removing it.

[0028] Fig. 2 shows a perspective view of the plating cell body. Fig. 2A shows a plan view of the plating cell body of the plating device, and Fig. 2B shows a bottom view of the plating cell body. Fig. 3 shows a perspective view of the presser lid 2 body. Note that the presser lid 2 shown in Fig. 1 is illustrated in a state where an acrylic cover is attached to the presser lid body of Fig. 3. Fig. 3A shows a plan view of the presser lid body of Fig. 3, and Fig. 3B shows a bottom view of the presser lid body.

[0029] The plating cell body 10 shown in FIG. 2 has an opening 11 and a pressure-reducing pocket 13 having an exhaust port 12 for reducing the pressure inside the cell, which is formed by the plating cell body 10, and the opening 11. The plating cell body 10 also has a liquid supply port 14 for supplying the plating solution into the plating cell and an exhaust port 15 for discharging the solution outside the cell. An anode (not shown) is also installed inside the plating cell. As shown in FIG. 2B, a pressure-reducing pipe 16 connected to the exhaust port 12 is provided on the bottom side of the plating cell body 10. The pressure-reducing pipe 16 extends from the exhaust port 12 toward the center of the plating cell body 10 and is connected to a vacuum pump (not shown) via a trap tank (not shown). A liquid discharge pipe 17 is also connected to the exhaust port 12, to which the pressure-reducing pipe 16 is connected.

[0030] The plating cell body 10 with this opening 11 was formed by a simultaneous casting method. Specifically, an adhesive (primer) was applied to a mold for forming the opening, and vinyl chloride, the constituent material of the plating cell body, was poured in. After the vinyl chloride solidified, silicone was poured into the adhesive-applied sealing portion at the position corresponding to the sealing portion of the opening (the periphery of the opening), and the mold was then pressurized. After the sealing material hardened, the mold was removed, and the vinyl chloride of the opening and the silicone forming the seal were fixed together. During this simultaneous casting method, a cathode was installed in the sealing portion so that a plating current could be supplied to the object to be plated placed in the opening.

[0031] Next, the pressure lid body of Fig. 3 will be described. As shown in Fig. 3A, the pressure lid body 20 is provided with a back pressure reduction mechanism 21 made of silicon. This back pressure reduction mechanism 21 is composed of a pressure reduction groove 23 to which a pressure reduction means 22 is connected. When the pressure lid 2 is placed on the back side of the object to be plated placed in the opening 11 of the plating cell 10 and the object is pressed, the back pressure reduction mechanism 21 of the pressure lid body 10 comes into close contact with the back side of the object to be plated. In this state, the air in the pressure reduction groove 21 shown in Fig. 3B is evacuated to reduce the pressure, thereby reducing the pressure in the space behind the object to be plated.

[0032] Next, the procedure for plating processing using the plating apparatus of this embodiment will be described. First, in the plating apparatus in the state shown in Fig. 1, the pressure lid 2 of the plating apparatus is detached from the plating cell 1 by the pressure arm 4. With the opening 11 of the plating cell 1 open, an object to be plated (e.g., a semiconductor wafer) is placed in the opening 11. With the object to be plated placed in the opening 11, the pressure arm 4 is driven to press the pressure lid 2 against the back side of the object to be plated.

[0033] The plating cell 1 and the pressure cover 2 are then rotated together by the inversion drive mechanism 3 to the position shown in Figure 4, with the surface of the object to be plated facing upward. The rotation angle at this time is 100° to 170° from the horizontal position in which the object to be plated was initially placed in the opening, i.e., with the surface of the object to be plated facing downward. In this state shown in Figure 4, before supplying liquid such as plating solution into the plating cell 1, the pressure inside the plating cell is reduced through the exhaust port 12 of the plating cell main body 10. The pressure is reduced to -95 to -100 kPa. At the same time, the rear pressure reduction mechanism 21 of the pressure cover main body 20 reduces the pressure in the back space on the back side of the object to -95 to -100 kPa.

[0034] After the pressure reduction of the plating cell 1 is complete, liquids that have been degassed in advance are supplied to the plating cell 1, including pre-degassed liquids, such as a plating solution, a pre-treatment liquid such as pure water or a dilute sulfuric acid solution to improve the wettability of the surface to be plated, and a catalyst solution for electroless plating. Here, we will explain the case where a pre-degassed dilute sulfuric acid pre-treatment liquid is supplied as an example. The pre-treatment liquid is supplied until it is sucked into the pressure-reducing pipe 16. After the predetermined amount has been supplied, the pressure-reducing valve (not shown) installed between the trap tank and the vacuum pump is closed, the air release valve (not shown) connected to the trap tank is opened, the pressure inside the pressure-reducing pipe 16 is returned to atmospheric pressure, and any pre-treatment liquid remaining in the pressure-reducing pipe 16 is discharged through the liquid discharge pipe 17.

[0035] After the pretreatment solution in the pressure-reducing pipe is drained, the air release valve connected to the trap tank is closed, and the pressure reducing valve between the trap tank and the vacuum pump is opened to reduce the pressure again to -95 to -100 kPa. After the pressure reduction is complete, the plating surface of the workpiece is pretreated for a predetermined time. After pretreatment, the plating cell 1 and the pressure lid 2 are rotated together by the inversion drive mechanism 3, changing their position to a vertical position as shown in Figure 5. Then, the plating cell is opened to the atmosphere, and the pretreatment solution is drained from the drain outlet 15 located below the plating cell. This completes the pretreatment of the dilute sulfuric acid solution.

[0036] After the pretreatment is complete, the plating apparatus is returned to the position shown in Figure 4, and the specified plating solution is supplied. The depressurization and supply of the plating solution are performed in the same manner as for the pretreatment solution described above. Plating is performed while maintaining a reduced pressure of -95 to -100 kPa. For electrolytic plating, a specified electrolytic current is supplied. For electroless plating, the plating is left for a specified period of time. During this plating process, the rotation angle of the plating apparatus can be adjusted as needed, allowing air bubbles generated during plating to be efficiently removed from the surface to be plated. After plating, the plating solution is drained in the same manner as for the pretreatment solution described above. If necessary, a cleaning solution is supplied to clean the surface to be plated. When depressurizing the plating cell, a trap tank (not shown) is installed between the depressurization device (e.g., a vacuum pump) and the plating cell to prevent the plating solution or pretreatment solution from being directly sucked into the depressurization device.

[0037] FIG. 6 shows a schematic piping diagram of the plating apparatus of this embodiment. In FIG. 6, the plating cell 1, the cover 2, and other components are simply depicted. The liquid discharged from the discharge port 14 of the plating cell 1 and the liquid in the decompression pipe discharged from the liquid discharge pipe 17 are discharged into the drain receiver 50 and then poured into the wastewater tank 51. Liquids such as plating solutions and pretreatment solutions are supplied to the plating cell 1 by a liquid supply unit 60. The liquid supply unit 60 is composed of a liquid storage tank 61, a degassing tank 62, and a degassing module 63. Liquids to be subjected to the intended treatment, such as plating solutions, pretreatment solutions, and cleaning water, are supplied to the liquid storage tank 61. Dissolved oxygen is removed from the liquid in the liquid storage tank 61 in the degassing tank 62. The liquid degassed in the degassing tank 62 passes through a degassing module 63 using hollow fibers, where dissolved oxygen is further removed, before being supplied to the plating cell 1. A plurality of such liquid supply units are provided, such as liquid supply units 60, 60', and 61'', for each type of plating solution, and by changing the plating solution to be supplied using a plating solution switching means (not shown), a plurality of plating processes can be performed using a single plating apparatus of this embodiment.

[0038] The plating apparatus of this embodiment is a type that plated semiconductor wafers as the object to be plated. The material of the semiconductor wafer can be any material, including Si, SiC, GaAs, GaN, and InP. Furthermore, by changing the shape of the opening of the plating cell, the apparatus can also be used for rectangular plate-shaped objects such as electronic substrates.

[0039] The plating apparatus of this embodiment can be applied to both electrolytic plating and electroless plating. In the case of electrolytic plating, an electrode is placed at the seal of the opening of the plating cell, and a plating current is supplied to the surface of the object to be plated. It is preferable to use a degassed plating solution. Various pretreatment solutions, such as pure water and dilute sulfuric acid solution, can be used as the pretreatment solution. A pretreatment solution suited to the plating solution to be used is preferably a degassed pretreatment solution.

[0040] In the plating apparatus of this embodiment, the pressure inside the plating cell and the pressure in the space behind the object to be plated are preferably reduced to -95 kPa to -100 kPa. Note that the plating apparatus of this embodiment can also perform plating at atmospheric pressure or a low pressure depending on the type of plating solution.

[0041] The results of copper embedding plating performed using a copper sulfate plating solution by the plating apparatus of this embodiment will be described below.

[0042] An 8-inch silicon wafer was used as the workpiece. The surface of this wafer to be plated had multiple vias, each 20 μm in diameter and 200 μm deep. The copper sulfate plating solution used was commercially available Microfab Cu525 (manufactured by EEJA Co., Ltd.). Degassed pure water was used as the pretreatment solution.

[0043] This copper embedding plating process uses a current density of 0.5A / dm 2The target thickness of copper plating was 8 μm, and copper plating was performed inside the vias under atmospheric pressure with the pressure reduced during the pure water pretreatment. For comparison, copper plating was also performed under atmospheric pressure without reducing the pressure during the pure water pretreatment. When reducing the pressure during pretreatment, the pressure inside the plating cell and the back space of the object to be plated was reduced to -95 kPa.

[0044] Copper embedding plating was performed with and without reduced pressure during pretreatment, and the cross-sections of the vias after plating were observed. Figures 7 and 8 show photographs of the cross-sections of the vias after plating. Figure 7 shows the case where reduced pressure was applied during pretreatment, and Figure 8 shows the case where plating pretreatment was performed without reduced pressure (atmospheric pressure). Note that in Figures 7 and 8, enlarged photographs of 100x and 200x magnifications are shown below the 50x magnification photograph. As can be seen from these photographs, when plating pretreatment was performed under reduced pressure, copper plating was confirmed to have been achieved all the way to the bottom of the via (the white areas within the via). In contrast, when pretreatment was not performed under reduced pressure (atmospheric pressure), an unplated area was confirmed at the bottom of the via (the black areas within the via). [Explanation of symbols]

[0045] 1. Plating Cell 10 Plating cell body 11 Opening 12 Exhaust port 13 Decompression pocket 14 Supply port 15 Drain 16 Pressure reducing pipe 17 Liquid discharge pipe 2 Presser cover 20 Presser cover body 21 Rear pressure reduction mechanism 22 Pressure reduction means 23 Decompression groove 3. Reverse drive mechanism 4 Presser arm 50 Drain receiving part 51 Drainage tank 60 Liquid supply unit 61 Liquid storage tank 62 Degassing tank 63 Degassing Module

Claims

1. a plating tank having an opening with a seal to prevent leakage of plating solution when an object to be plated is placed therein, a liquid supply unit for supplying plating solution, and a liquid discharge unit for discharging plating solution; a rotating means for rotating the plating tank itself; a tank internal decompression means for decompressing a tank internal space formed by the plating tank and a plating target surface of the object to be plated placed in the opening; A plating apparatus for reduced pressure plating treatment, comprising: a back pressure cover for pressing the peripheral edge of the object to be plated placed in the opening, and a back pressure reducing means for reducing the pressure of a back space formed on the back side of the object to be plated, which is the back side of the surface to be plated; The tank internal pressure reduction means comprises a pressure reduction pocket provided on the inner wall of the plating tank located above the inclined position when the plating tank is rotated to place the object to be plated in the inclined position, a pressure reduction pipe connected to the exhaust port of the pressure reduction pocket, and a liquid discharge pipe for discharging the plating solution remaining in the pressure reduction pipe, A plating apparatus for vacuum plating treatment, characterized in that the vacuum pipe extends from the vacuum pocket toward the center of the plating tank.

2. 2. The plating apparatus according to claim 1, wherein the volume of the space within the plating tank is adjusted so that the amount of solution supplied to the plating tank is 2.0 mm to 10.0 mm thick from the surface of the object to be plated.

3. 3. The plating apparatus according to claim 1, further comprising a degassing means for removing dissolved oxygen contained in the liquid supplied to the plating tank.

4. 3. The plating apparatus according to claim 1, further comprising a plurality of plating solution storage tanks each capable of storing two or more types of plating solution, and a plating solution switching means for switching the plating solution supplied to the plating tanks.

5. A reduced pressure plating method using the plating apparatus according to claim 1, The object to be plated is placed on the opening of the plating tank, the opening is liquid-tightly sealed with the object to be plated, and the peripheral edge of the object to be plated is pressed from the back side of the object to be plated placed on the opening to fix it; The plating tank is rotated to change the position of the object to be plated placed in the opening, and plating solution is supplied to fill the plating tank with plating solution, thereby bringing the plating solution into contact with the object to be plated; The tank interior space of the plating tank is depressurized using a depressurization pipe of the tank interior depressurization means, and a back space formed on the back side of the object to be plated that is not to be plated is depressurized; A reduced pressure plating method characterized by reducing the pressure inside the plating tank to a predetermined level, then discharging the plating solution remaining in the reduced pressure pipe through a liquid discharge pipe, and then performing plating.

6. 6. The reduced pressure plating method according to claim 5, wherein the liquid to be supplied to the plating tank is deaerated in advance.

7. 7. The reduced-pressure plating method according to claim 5, wherein the plating solution supplied to the plating tank is replaced with another plating solution to perform a plurality of plating processes.

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