Plating Device for Reduced-Pressure Plating Treatment And Reduced-Pressure Plating Treatment Method

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a plating equipment that performs plating treatment on an object to be plated, such as a semiconductor wafer or a printed circuit board, and particularly relates to a plating equipment that can perform plating treatment under reduced pressure during plating treatment and to a method of vacuum plating treatment using the plating equipment.

Description of the Related Art

In recent years, various plating treatments have been performed on objects to be plated, including semiconductor wafers or electronic substrates, such as printed circuit boards. Recently, a reduction in weight, thickness, and length of electronic substrates has been in progress, so that there is a strong tendency for fine plating treatment to be demanded. For example, for an object to be plated, such as a semiconductor wafer, micro vias are required to be filled by performing plating treatment. The via aspect ratios are steadily moving towards larger values.

In general, in plating treatment, it is known that air bubbles in the plating solution or air bubbles adhering to the plating treatment surface may be a cause of plating defects. In performing plating treatment, such as filling the micro vias, for example, when air bubbles are present in or around the vias, plating defects are liable to occur, so that a desired plating treatment cannot be performed.

As a countermeasure against such air bubbles in the plating solution, the following techniques have been proposed in the related art. One of the techniques proposed is a method for performing electroplating treatment or electroless plating treatment by deaerating dissolved oxygen in a pretreatment solution for plating by a deaerator, which uses a deaeration membrane module and a vacuum pump, and by performing a pretreatment on an object to be plated with the deaerated pretreatment solution (Patent Literature 1, for example). Patent Literature 1 also proposes performing electroplating treatment or electroless plating treatment by immersing an object to be plated into a deaerated plating solution.

For a jet plating equipment that performs plating treatment with the surface to be plated of an object to be plated caused to face downward, there is the following proposal. For pretreatment, the object to be plated is placed at the upper portion of a pretreatment tank, the object to be plated is heated, gas in the pretreatment tank is replaced with evaporated water by reducing the pressure in the pretreatment tank to 9 hPa to 40 hPa and by supplying water at 10° C. to 30° C. into the pretreatment tank, and the pretreatment tank is filled with water, thus causing the water to come into contact with the surface to be plated and, thereafter, atmospheric air is introduced into the pretreatment tank to cause the pretreatment tank to have an atmospheric pressure, thus causing the water to adhere to the surface to be plated (Patent Literature 2, for example). Further, as a method for causing various solutions, such as a plating solution, to enter fine recesses, there is proposed a plating equipment that includes a pressure control unit and a vacuum chuck, the pressure control unit being provided for reducing the pressure in a solution storage section formed by a semiconductor wafer and a cap, the vacuum chuck reducing the pressure on the back surface of a wafer (Patent Literature 3).

Then, for the jet plating equipment, which includes a plating tank provided with an opening portion, a solution supply section, a solution discharge section, and an anode, the opening portion including a solution seal configured to prevent leakage of the plating solution when an object to be plated is placed, the plating solution being supplied from the solution supply section, the plating solution being discharged from the solution discharge section, thenode facing the placed object to be plated, a plating equipment is also proposed in which the plating tank is provided with a rotating unit configured to rotate the plating tank itself (Patent Literature 4, for example).

Then, In the jet plating equipment which has a plating tank provided with an opening having a solution seal to prevent leakage of the plating solution when the object to be plated is placed therein, a solution supply section for the supplying plating solution and a solution discharge section for the discharging plating solution, and an anode configured to face the object to be plated, it has also been proposed that the plating tank is provided with a rotating means for rotating the plating tank itself (Patent Literature 4, for example).

With each plating treatment technique of the above-mentioned related art, it is possible to preferably perform filling of vias having a somewhat minute size and plating treatment performed on trenches between fine wirings. However, a further reduiction in weight, thickness, and length is in progress in recent electronic substrates. For example, micronization of vias has remarkably progressed and, at present, there is a demand for a plating treatment technique that can surely perform suitable plating treatment on fine vias having a high aspect ratio with a via diameter of 5 μm and a via depth of 100 μm, for example.

It is known that, on an object to be plated, including a semiconductor wafer or an electronic substrate, such as a printed circuit board, a plurality of plating treatments are performed with nickel, palladium, or gold, etc. in addition to the plating treatment performed for filling vias with copper, for example. For such a plurality of plating treatments, various plating treatment methods, such as electroplating and electroless plating, are adopted. Therefore, it is a current situation with the case of performing a plurality of plating treatments on an object to be plated that generally plating equipment corresponding to various plating treatments are prepared, and an object to be plated is carried to each plating equipment to perform each plating treatment.

In performing the plurality of plating treatments on the object to be plated as described above, the plating equipment that correspond to various plating treatments are prepared. However, such an approach increases the size of manufacturing equipment, thus increasing manufacturing costs. That is, such an approach is insufficient for efficient manufacturing. If the plurality of plating treatments can be handled by one plating equipment, it is possible to save space for manufacturing equipment, thus achieving efficient manufacturing and hence, achievement of such a universal plating equipment is also expected.

CITATION LIST

Patent Literature

[Patent Literature 1] Japanese U.S. Pat. No. 4,043,192

[Patent Literature 2] Japanese Patent Application Laid-Open No. 2014-47391

[Patent Literature 3] Japanese Patent Application Laid-Open No. 11-87273

[Patent Literature 4] Japanese U.S. Pat. No. 3,513,130

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The present invention has been made in view of the above-mentioned circumstances, and provides a plating treatment technique that can surely perform plating treatment on micro vias or grooves formed in the surface to be plated of the object to be plated while influence of air bubbles and the like is suppressed as much as possible. The present invention provides a plating treatment technique with which a plurality of plating treatments can be handled by one plating equipment.

Means for Solving the Problems

To solve the above-mentioned problem, the present invention relates to a plating equipment for vacuum plating treatment, the plating equipment including: a plating tank including an opening portion, a solution supply section, and a solution discharge section, the opening portion including a seal configured to prevent leakage of a plating solution when an object to be plated is placed, the plating solution being supplied from the solution supply section, the plating solution being discharged from the solution discharge section; a rotating unit configured to rotate the plating tank itself; an in-tank pressure reducing unit configured to decompress in an in-tank space formed by a surface to be plated of the object to be plated placed at the opening portion and the plating tank; and an object-to-be-plated back surface press cover including a back surface pressure reducing unit configured to press a peripheral edge of the object to be plated placed at the opening portion to decompress in a back space formed on a back surface side of the object to be plated, being a rear surface of the surface to be plated, wherein the in-tank decompression unit includes a decompression pocket, a decompression pipe, and a solution discharge pipe, the decompression pocket being, when the object to be plated is brought into an inclined posture by rotating the plating tank, provided on an inner wall of the plating tank at a position located at an upper portion in the inclined posture, the decompression pipe being connected to an exhaust port of the decompression pocket, the solution discharge pipe being provided for discharging the plating solution remaining in the decompression pipe, and the decompression pipe extends from the decompression pocket in a direction toward a center of the plating tank. The present invention makes it possible to surely remove air bubbles in the plating solution and air bubbles adhering to the plating treatment surface of the object to be plated by reducing the pressure in the in-tank space formed in the plating tank. Accordingly, it is possible to perform a desired plating treatment on minute regions on the surface to be plated of the object to be plated, for example, on twenty or more vias having a high accept ratio and trenches without causing plating defects, such as breakage of plating.

In the plating equipment of the present invention, the pressure in the in-tank space of the plating tank is reduced to −95 to −100 kPa (atmospheric pressure 0, gauge pressure). However, merely reducing the pressure generates a force with which a solution that is supplied to the plating tank, for example, a solution such as a plating solution, washing water, or a pretreatment solution, is suctioned toward the decompression pipe when pressure is reduced When the solution is in a state of being suctioned into the pressure reducing pipe, it is difficult to surely reduce the pressure in the in-tank space of the plating tank. In view of the above, to surely control a decompression in the in-tank space of the plating tank, in the plating equipment of the present invention, such a pressure reducing operation is performed in a state in which the object to be plated placed at the opening portion of the plating tank is brought into an inclined state by rotating the plating tank. At first, the object to be plated is horizontally placed at the opening pion of the plating tank with the surface to be plated caused to face downward. However, at the time of decompression the plating tank is rotated such that the surface to be plated of the object to be plated is caused to face upward, and a rotation angle is 100° to 170°. When the plating tank is rotated as described above, the plating tank (as well as the object to be plated and the surface to be plated) is brought into an inclined state. In the plating equipment of the present invention, the decompression pocket is provided on the inner wall of the plating tank at a position located at an upper portion in the inclined posture. Then, the decompression pipe extends from the decompression pocket in the direction toward the center of the plating tank. That is, when the plating tank is brought into an inclined posture, a state is brought about in which the decompression pocket is located at the upper portion, and the decompression pipe is disposed to extend downward from the exhaust port of the decompression pocket.

In the plating equipment of the present invention, an operation of reducing the pressure is performed as follows. First, an object to be plated is placed at the opening portion, and the plating tank is rotated up to a predetermined rotation angle. The pressure in the in-tank space is reduced to a predetermined pressure (−95 to −100 kPa) before a solution, such as a plating solution, is supplied to the plating tank. [At this point of operation, the pressure in the back space is also reduced (−95 to −100 kPa) by the object-to-be-plated back surface press cover, the back space being formed on the back surface side of the object to be plated. Thereafter, a solution is supplied into the plating tank in a decompressed state. Such supply of the solution is continued until the solution is suctioned into the decompression pipe. After the supply is stopped, the pressure in the decompression pipe is returned to the atmospheric pressure and, then, the solution remaining in the decompression pipe is discharged by the solution discharge pipe connected to the decompression pipe. In the plating equipment of the present invention, when the plating tank is rotated, thus being brought into an inclined posture, the decompression pipe extends from the exhaust port of the decompression pocket in the direction toward the center of the plating tank and hence, the decompression pipe is disposed to extend downward from the exhaust port. Therefore, the solution supplied to the plating tank is brought into a state of being supplied into the plating tank up to a portion before the exhaust port of the decompression pocket, so that it is possible to prevent the solution from being suctioned into the decompression pipe due to a decompressed and hence, the pressure in the in-tank space of the plating tank can be surely reduced to a predetermined pressure (−95 to −100 kPa).

In the plating equipment of the present invention, it is preferable that an in-tank space capacity be adjusted such that a supply amount for the plating tank causes a solution thickness of 2.0 mm to 10.0 mm from the surface to be plated of the object to be plated. In the plating equipment of the present invention, to surely achieve a decompression in the in-tank space of the plating tank, it is preferable to adjust the in-tank space capacity of the plating tank. When the in-tank space capacity is excessively large, a long time is required for an operation of decompression to a predetermined pressure, thus lowering work efficiency. When the in-tank space capacity is excessively small, there is a tendency for suitable plating treatment not to be performed. In the plating equipment of the present invention, the in-tank space capacity of the plating tank is specified by a solution thickness from the surface to be plated of the object to be plated. It is safe to say that a specific capacity is as follows. When the object to be plated is a 6-inch wafer made of silicon, a suitable in-tank space capacity is approximately 32 mL to 153 mL, when the object to be plated is a 8-inch wafer, a suitable in-tank space capacity is approximately 57 mL to 284 mL, and when the object to be plated is a 12-inch wafer, a suitable in-tank space capacity is approximately 132 mL to 660 mL.

In achieving the plating equipment of the present invention, it is preferable that the opening portion of the plating tank be molded by adhesively fixing a sealing member forming a seal to a plating tank member forming the plating tank. In the plating equipment of the present invention, the pressure in the in-tank space, which is formed by the surface to be plated of the object to be plated placed at the opening portion and the plating tank, is reduced-and hence, it is necessary to prevent leakage of the solution at a contact portion between the object to be plated placed at the opening portion and the seal of the opening portion. To reduce the pressure in the in-tank space to −95 to −100 kPa, it is important to surely prevent leakage of the solution from the seal provided at the opening portion. To achieve the above, it is necessary to form the opening portion such that the sealing member forming the seal is adhesively fixed to the plating tank member forming the plating tank. The term “adhesively fixed” refers to a state in which the sealing member is the solution-tightly adhered to the plating tank member. In the case of forming the opening portion of the plating tank in which the sealing member forming the seal is adhesively fixed to the plating tank member forming the plating tank, such an opening portion of the plating tank can be achieved by molding the opening portion by simultaneous casting. This simultaneous casting refers to a casting method in which a plating tank member and a sealing member are placed into a formwork for forming the opening portion, and the formwork is pressurized to mold the opening portion. Specifically, an adhesive agent (primer) is applied to a position corresponding to the sealing portion of the opening portion of the plating tank member placed into the formwork in advance (the peripheral edge portion of the opening portion) and, after the sealing member is placed into the sealing portion to which the adhesive agent is applied, the formwork is pressurized. After the sealing member is cured, when the formwork is detached to mold the opening portion, a state is brought about in which the sealing member forming the seal is adhesively fixed to the plating tank member forming the plating tank. Such an opening portion formed in an adhesively fixed state can surely prevent leakage of the plating solution at the seal caused by a decompression in the plating tank. Although the material of the plating tank member and the material of the sealing member are not particularly limited, by taking into account processability and the plating solution resistance, it is preferable to use vinyl chloride (PVC) for the plating tank member, and silicon for the sealing member. It is possible to mold a cathode to be caused to come into contact with the object to be plated at a position corresponding to the sealing portion (the peripheral edge portion of the opening portion) at the same time.

It is preferable that the plating equipment of the present invention include a deaerating unit configured to remove dissolved oxygen included in a solution to be supplied to the plating tank. In atmospheric air, a certain amount of oxygen is dissolved in the solution to be supplied to the plating tank, for example, in a plating solution, washing water, or a pretreatment solution, etc. and hence, it is desirable to remove the dissolved oxygen in the solution in advance to prevent the generation of air bubbles. Although the deaerating unit is not particularly limited, it is desirable to use a deaeration module that uses hollow fibers.

It is preferable that the plating equipment of the present invention be provided with a plurality of the plating solution storage tanks capable of individually storing two or more the plating solutions, and include a plating solution switching unit configured to switch the plating solutions to be supplied to the plating tank. Although the plating equipment of the present invention can perform plating treatment in a decompressed state, as a matter of course, the plating equipment of the present invention can perform plating treatment at the atmospheric pressure state. Further, when an electrode is embedded in the seal of the opening portion and an anode is disposed in the plating tank, electroplating treatment can be performed. Therefore, by changing the kind of the plating solution to be supplied to the plating tank, it is possible to perform a plurality of plating treatments. In this case, when the plating solution switching unit is provided to change the kind of the plating solution, a plurality of plating treatments can be performed continuously. For example, in the case of performing plating treatment on an object to be plated, such as a semiconductor wafer, there may be a case in which plating treatment is performed in the order of nickel, palladium, and gold. [Such plating treatment can be achieved by preparing three plating solutions storage tanks capable of individually storing a nickel plating solution, a palladium plating solution, and a gold plating solution, and switching plating solutions to be supplied to the plating tank by the plating solution switching unit. Such a configuration is effectively applicable to plating treatment for products of many models in small quantities, and can save space in which the plating equipment is disposed.

The present invention relates to a method of vacuum plating treatment, the method including: placing an object to be plated at an opening portion of a plating tank, the solution-tightly sealing the opening portion by the object to be plated, and pressing and fixing a peripheral edge of the object to be plated from a back surface side of the object to be plated placed at the opening portion; changing a posture of the object to be plated placed at the opening portion by rotating the plating tank, and filling the plating tank with a plating solution by supplying the plating solution to contact the plating solution with the object to be plated; reducing a pressure in an in-tank space of the plating tank by using a decompression pipe, being an in-tank decompressing unit, and reducing a pressure in a back space formed on a back surface side of the object to be plated on which no plating treatment is performed; and reducing the pressure in the in-tank space of the plating tank to a predetermined pressure and, thereafter, discharging the plating solution remaining in the decompression pipe from a solution discharge pipe, and performing plating treatment.

In the method of vacuum plating treatment of the present invention, it is preferable that deaeration treatment be performed in advance on a solution to be supplied to the plating tank.

In the method of vacuum plating treatment of the present invention, it is preferable that a plurality of plating treatments be performed by switching plating solutions to be supplied to the plating tank.

In the present invention, as a matter of course, the plating treatment can be performed at an atmospheric pressure without a decompression. Therefore, it is possible to perform plating treatment at an atmospheric pressure or in a low-pressure state according to the kind of the plating solution. In the case of performing a plurality of plating treatments on an object to be plated, it is preferable that the plating treatments be performed by switching plating solutions to be supplied to the plating tank.

The plating equipment and the method of vacuum plating treatment of the present invention are applicable to both electroplating treatment and electroless plating treatment.

Advantageous Effect of Invention

By the present invention, plating treatment can be surely performed on micro vias or trenches formed in the surface to be plated of the object to be plated while influence of air bubbles or the like is suppressed as much as possible, and a plurality of plating treatments can be handled by one plating equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Perspective view of the plating equipment of the present embodiment

FIG. 1A Right side view of the plating equipment of the present embodiment

FIG. 1B Left side view of the plating equipment of the present embodiment

FIG. 1C Front view of the plating equipment of the present embodiment

FIG. 1D Plan view of the plating equipment of the present embodiment

FIG. 2 Perspective view of the plating cell main unit of the plating equipment

FIG. 2A Plan view of the plating cell main unit of the plating equipment

FIG. 2B Bottom view of the plating cell main unit of the plating equipment

FIG. 3 Perspective view of the press lid main unit of the plating equipment

FIG. 3A Plan view of the press lid main unit of the plating equipment

FIG. 3B Bottom view of the press lid main unit of the plating equipment

FIG. 4 Perspective view of the plating equipment during plating treatment

FIG. 5 Perspective view of the plating equipment at drain

FIG. 6 Schematic view of piping of the plating equipment of the present embodiment

FIG. 7 Observation photograph of plating state in cross section of vias (Decompression)

FIG. 8 Observation photograph of plating state in cross section of vias (atmospheric pressure)

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described with reference to drawings. FIG. 1 shows a perspective view of a plating equipment of the present embodiment. FIG. 1A shows a right side view, FIG. 1B shows a left side view, FIG. 1C shows a front view, and FIG. 1D shows a plan view of the plating equipment.

The plating equipment of the present embodiment includes a plating cell 1 and a press lid 2, and the plating cell 1 is provided with a reverse driving mechanism 3. Further, the press lid 2 is provided with a press arm 4 for mounting and dismounting the press lid 2 on and from the plating cell 1.

FIG. 2 shows a perspective view of a plating cell main unit. FIG. 2A shows a plan view of the plating cell main unit of the plating equipment, and FIG. 2B shows a bottom view of the plating cell main unit. FIG. 3 shows a perspective view of the main unit of the press lid 2. The press lid 2 shown in FIG. 1 is in a state in which an acrylic cover is attached to the press lid main unit shown in FIG. 3. FIG. 3A shows a plan view of the press lid main unit shown in FIG. 3, and FIG. 3B shows a bottom view of the press lid main unit.

A plating cell main unit 10 shown in FIG. 2 has an opening portion 11, and has a decompression pocket 13 having an exhaust port 12 for decompression in the space in the cell formed by the surface to be plated of an object to be plated placed at the opening portion 11 and the plating cell main unit 10. The plating cell main unit 10 is also provided with a solution supply port 14 and a discharge port 15, the plating solution being supplied into the plating cell through the solution supply port 14, the plating solution being discharged to the outside of the cell through the discharge port 15. An anode (not shown in the drawing) is installed in the plating cell. As shown in FIG. 2B, the bottom portion side of the plating cell main unit 10 is provided with a decompression pipe 16 connected to the exhaust port 12. This decompression pipe 16 extends from the exhaust port 12 in the direction toward the center of the plating cell main unit 10, and is coupled to a vacuum pump (not shown in the drawing) via a trap tank (not shown in the drawing). A solution discharge pipe 17 is also connected to the exhaust port 12 to which the decompression pipe 16 is connected.

The plating cell main unit 10 having the opening portion 11 was formed by a simultaneous casting method. Specifically, an adhesive agent (primer) was applied in advance to a formwork for forming the opening portion, and vinyl chloride, being a constituent material of the plating cell main unit, was added. After the vinyl chloride was solidified, silicon was added at a position that corresponds to the sealing portion of the opening portion (the peripheral edge portion of the opening portion), that is, was placed into the sealing portion to which the adhesive agent was applied and, thereafter, the formwork was pressurized. After the sealing member was cured, the formwork was detached, thus bringing about a state in which the vinyl chloride of the opening portion and the silicon forming the seal were adhesively fixed to each other. In this simultaneous casting method, a cathode was installed at the sealing portion so as to allow a plating current to be supplied to an object to be plated placed at the opening portion.

Next, the press lid main unit shown in FIG. 3 will be described. As shown in FIG. 3A, a press lid main unit 20 is provided with a back surface decompression mechanism 21 made of silicon. The back surface decompression mechanism 21 is formed of decompression grooves 23 to which a decompression unit 22 is connected. When the press lid 2 is disposed, from the back surface side of an object to be plated, on the object to be plated placed at the opening portion 11 of the plating cell main unit 10, and the object to be plated is pressed, the back surface decompression mechanism 21 of the press lid main unit 10 contacts closely with the back surface side of the object to be plated. By reducing the pressure by exhausting air in the decompression grooves 21 shown in FIG. 3B in such a state, the pressure in the back space of the object to be plated is reduced.

Subsequently, the procedure of plating treatment by the plating equipment of the present embodiment will be described. First, in the plating equipment in a state shown in FIG. 1, the press lid 2 of the plating equipment is dismounted from the plating cell 1 by the press arm 4. An object to be plated (a semiconductor wafer, for example) is placed at the opening portion 11 with the opening portion 11 of the plating cell 1 in an open state. [The press arm 4 is driven with the object to be plated being placed at the opening portion 11 to press the object to be plated by the press lid 2 from the back surface side of the object to be plated.

Thereafter, the plating cell 1 and the press lid 2 are integrally rotated by the reverse driving mechanism 3 to change the posture to the posture as shown in FIG. 4, thus causing the surface to be plated of the object to be plated to face upward. A rotation angle at this point of operation is 100° to 170° from a state in which the object to be plated is first placed at the opening portion, that is, from a horizontal position at which the surface to be plated of the object to be plated is caused to face downward. In such a state shown in FIG. 4, the pressure in the plating cell is reduced by the exhaust port 12 of the plating cell main unit 10 before a solution, such as the plating solution, is supplied into the plating cell 1. At this point of operation, the pressure is reduced to −95 to −100 kPa. At the same time, the pressure in the back space on the back surface side of the object to be plated is reduced to −95 to −100 kPa by the back surface pressure reducing mechanism 21 of the press lid main unit 20.

After a decompression in the plating cell 1 is completed, a solution is supplied to the plating cell 1, such as a solution on which deaeration treatment is performed in advance, that is, a plating solution, a pretreatment solution, such as pure water or diluted the sulfuric acid solution for improving wettability of the surface to be plated, or a catalyzing solution for electroless plating treatment. In the present embodiment, the description will be made by taking, as an example, a case in which a pretreatment solution, being diluted sulfuric acid on which deaeration treatment is performed in advance, is supplied. The supply of the pretreatment solution is supplied until the pretreatment solution is suctioned into the decompression pipe 16. After a predetermined amount of the pretreatment solution is supplied, a decompressing valve (not shown in the drawing) provided between the trap tank and the vacuum pump is closed and an atmosphere release valve (not shown in the drawing) connected to the trap tank is opened to return the pressure in the decompression pipe 16 to the atmospheric pressure, and the pretreatment solution remaining in the decompression pipe 16 is discharged by the solution discharge pipe 17.

After the pretreatment solution in the decompression pipe is discharged, the atmosphere release valve connected to the trap tank is closed and the decompression valve disposed between the trap tank and the vacuum pump is opened to reduce the pressure to −95 to −100 kPa again. After a decompression is completed, a pretreatment is performed on the surface to be plated of the object to be plated for a predetermined time. After the pretreatment is performed, the plating cell 1 and the press lid 2 are integrally rotated by the reverse driving mechanism 3 to change the posture to a vertical state as shown in FIG. 5. Then, the inside of the plating cell is opened to the atmosphere to discharge the pretreatment solution from the drain port 15, which is located on the lower side of the plating cell. With such an operation, the pretreatment that uses diluted the sulfuric acid solution is completed.

After the pretreatment is completed, the plating equipment is returned to the posture shown in FIG. 4, and a predetermined plating solution is supplied. A decompression treatment and a supply of the plating solution are performed in the same manner as in the case of the above-mentioned pretreatment solution. A plating treatment is performed in a state in which a decompressed state, that is, −95 to −100 kPa, is held. In the case of electroplating, a predetermined electrolytic current is supplied. In the case of electroless plating treatment, the plating equipment is left for a predetermined time. In performing such plating treatment, the plating treatment can be performed by adjusting the rotation angle of the plating equipment when necessary and hence, the plating treatment can be performed while air bubbles generated during plating are efficiently removed from a surface to be plated. After the plating treatment is performed, the plating solution is discharged in the same manner as in the above-mentioned pretreatment solution. A cleaning solution is supplied to perform washing treatment on the surface to be plated when necessary. In the case of reducing the pressure in the plating cell, the trap tank (not shown in the drawing) is provided between a pressure reducing device (a vacuum pump, for example) and the plating cell so as to prevent the plating solution and the pretreatment solution from being directly suctioned into the pressure reducing device.

FIG. 6 shows a schematic view of piping of the plating equipment of the present embodiment. In FIG. 6, the plating cell 1, the press lid 2, and the like are illustrated in a simplified manner. The solution discharged from a discharge port 14 of the plating cell 1 and the solution in the decompression pipe that is discharged from the solution discharge pipe 17 are released to a drain receiving section 50 [and are then placed into a drainage tank 51.] and is connected to a drain tank 51 for drainage. The solutions, such as the plating solution and the pretreatment solution, are supplied to the plating cell 1 by a solution supply unit 60. The solution supply unit 60 is formed of a solution storage tank 61, a deaeration treatment tank 62, and a deaeration module 63. A solution for performing a target treatment, that is, the plating solution, the pretreatment solution, washing water, or the like, is supplied to the solution storage tank 61. Dissolved oxygen in the solution in the solution storage tank 61 is removed in advance in the deaeration treatment tank 62. The solution that is deaerated in the deaeration treatment tank 62 passes through the deaeration module 63, which uses hollow fibers, so that dissolved oxygen is further removed, and the solution is then supplied to the plating cell 1. By providing a plurality of the solution supply units for various plating solutions, that is, by providing the solution supply units—60, 60′, 61″, for example, and by changing a plating solution to be supplied by using a plating solution switching unit (not shown in the drawing), it is possible to perform a plurality of plating treatments by using one plating equipment of the present embodiment.

The plating equipment of the present embodiment is of a type that performs plating treatment on a semiconductor wafer that is an object to be plated. Si, SiC, GaAs, GaN, InP, or the like may be used as the material of this semiconductor wafer without any particular limitation. Further, by changing the shape of the opening portion of the plating cell, the plating equipment of the present embodiment is also applicable to an object to be plated having a rectangular plate shape, such as an electronic substrate.

The plating equipment of the present embodiment is applicable to both electroplating treatment and electroless plating treatment. In the case of electroplating treatment, an electrode is disposed at the seal of the opening portion of the plating cell, and a plating current is supplied to the surface to be plated of the object to be plated to perform the electroplating treatment. It is preferable to use a plating solution on which deaeration treatment is performed. For a pretreatment solution, various pretreatment solutions may be used, such as pure water or diluted the sulfuric acid solution. The pretreatment solution that is used depends on the plating solution to be used, and it is preferable to use the pretreatment solution on which deaeration treatment is performed.

In the plating equipment of the present embodiment, it is preferable that the pressure in the plating cell and the pressure in the back space of the object to be plated be reduced to −95 kPa to −100 kPa. In the plating equipment of the present embodiment, it is also possible to perform plating treatment at an atmospheric pressure or in a low-pressure state according to the kind of the plating solution.

Hereinafter, the description will be made for the results of copper via filling plating treatment performed by the plating equipment of the present embodiment by using a copper sulfate plating solution.

An 8-inch wafer made of silicon was used for an object to be plated.

The surface of this wafer to be plated has multiple vias with a diameter of 20 μm and a depth of 200 μm formed in it. Commercially available MICROFAB Cu525 (manufactured by EEJA Ltd.) was used for the copper sulfate plating solution. Pure water on which deaeration treatment has been performed was used for the pretreatment solution.

In this copper via filling plating treatment, current density was set to 0.5 A/dm² to form copper plating having a target thickness of 8 μm in each via, the pressure was reduced during pretreatment with pure water, and copper plating was performed at an atmospheric pressure. For the purpose of comparison, the copper via filling plating treatment was also performed such that the pressure was not reduced (atmospheric pressure) during pretreatment with pure water, and copper plating was performed at an atmospheric pressure. In the case in which the pressure is reduced during pretreatment, the pressure in the plating cell and the pressure in the back space of an object to be plated were reduced to −95 kPa.

A copper via filling plating treatment under reduced pressure during pretreatment and a copper via filling plating treatment without a decompression during pretreatment were performed, and the cross sections of vias after plating were observed. FIG. 7 and FIG. 8 show photographs of cross sections of vias after plating. FIG. 7 shows a case in which the pressure was reduced during pretreatment, and FIG. 8 shows a case in which the plating pretreatment was performed without a decompression (atmospheric pressure). Each of FIGS. 7 and 8 shows enlarged photographs, with an observation photograph with ×100 magnification and an observation photograph with ×200 magnification disposed below an observation photograph with ×50 magnification. As can be seen from these observation photographs, in the case in which the plating pretreatment was performed under reduced pressure, it was confirmed that copper plating (portions in the vias that appear white) occurs down to the bottom portions of the vias. In contrast, in the case in which the pressure was not reduced (atmospheric pressure) during pretreatment, portions (portions in the vias that appear black) were confirmed at which plating treatment does not occur at the bottom portions of the vias.

REFERENCE SIGNS LIST

• • 1 plating cell
  • 10 plating cell main unit
  • 11 opening portion
  • 12 exhaust port
  • 13 decompression pocket
  • 14 supply port
  • 15 drain port
  • 16 decompression pipe
  • 17 solution discharge pipe
  • 2 pressing lid
  • 20 pressing lid main unit
  • 21 back surface decompress mechanism
  • 22 decompression unit
  • 23 decompression groove
  • 3 reverse driving mechanism
  • 4 press arm
  • 50 drain receiving section
  • 51 drainage tank
  • 60 solution supply unit
  • 61 solution storage tank
  • 62 deaeration treatment tank
  • 63 deaeration module