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

Abstract

A plating treatment technique with which influence of air bubbles or the like can be suppressed as much as possible in plating treatment on micro vias or trenches, and a plurality of plating treatments can be handled by one plating equipment. Plating equipment for vacuum plating treatment including: a plating tank including an opening portion having a seal that prevents leakage of a plating solution, and a solution supply section and a solution discharge section for the plating solution; a rotating unit for the plating tank; an in-tank decompression unit that reduces a pressure in an in-tank space; and an object-to-be-plated back surface press cover including a back surface decompression unit that presses a peripheral edge of an 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.

Claims

1. A plating equipment for vacuum plating treatment, the plating equipment comprising: 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 decompression 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 decompression 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.

2. The plating equipment according to claim 1, wherein an in-tank space capacity is 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.

3. The plating equipment according to claim 1, comprising a deaerating unit configured to remove dissolved oxygen included in a solution to be supplied to the plating tank.

4. The plating equipment according to claim 1, wherein the plating equipment is provided with a plurality of the plating solution storage tanks capable of individually storing two kinds or more the plating solutions, and includes a plating solution switching unit configured to switch the plating solutions to be supplied to the plating tank.

5. A method of vacuum plating treatment using the plating equipment according to claim 1, the method comprising: placing an object to be plated at an opening portion of a plating tank, 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->decompression in an in-tank space of the plating tank by using a decompression pipe, being an in-tank decompression unit, and reducing a pressure->decompress 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->decompression 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 a plating equipment for vacuum plating treatment characterized by: performing plating treatment.

6. The method of vacuum plating treatment according to claim 5, wherein deaeration treatment is performed in advance on a solution to be supplied to the plating tank.

7. The method of vacuum plating treatment according to claim 5, wherein a plurality of plating treatments are performed by switching the plating solutions to be supplied to the plating tank.

8. The plating equipment according to claim 2 comprising a deaerating unit configured to remove dissolved oxygen included in a solution to be supplied to the plating tank.

9. The plating equipment according to claim 2 wherein the plating equipment is provided with a plurality of the plating solution storage tanks capable of individually storing two kinds or more the plating solutions, and includes a plating solution switching unit configured to switch the plating solutions to be supplied to the plating tank.

10. The method of vacuum plating treatment according to claim 6 wherein a plurality of plating treatments are performed by switching the plating solutions to be supplied to the plating tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 Perspective view of the plating equipment of the present embodiment

[0030] FIG. 1A Right side view of the plating equipment of the present embodiment

[0031] FIG. 1B Left side view of the plating equipment of the present embodiment

[0032] FIG. 1C Front view of the plating equipment of the present embodiment

[0033] FIG. 1D Plan view of the plating equipment of the present embodiment

[0034] FIG. 2 Perspective view of the plating cell main unit of the plating equipment

[0035] FIG. 2A Plan view of the plating cell main unit of the plating equipment

[0036] FIG. 2B Bottom view of the plating cell main unit of the plating equipment

[0037] FIG. 3 Perspective view of the press lid main unit of the plating equipment

[0038] FIG. 3A Plan view of the press lid main unit of the plating equipment

[0039] FIG. 3B Bottom view of the press lid main unit of the plating equipment

[0040] FIG. 4 Perspective view of the plating equipment during plating treatment

[0041] FIG. 5 Perspective view of the plating equipment at drain

[0042] FIG. 6 Schematic view of piping of the plating equipment of the present embodiment

[0043] FIG. 7 Observation photograph of plating state in cross section of vias (Decompression)

[0044] FIG. 8 Observation photograph of plating state in cross section of vias (atmospheric pressure)

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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 units60, 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] An 8-inch wafer made of silicon was used for an object to be plated.

[0062] The surface of this wafer to be plated has multiple vias with a diameter of 20 m and a depth of 200 m 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.

[0063] In this copper via filling plating treatment, current density was set to 0.5 A/dm.sup.2 to form copper plating having a target thickness of 8 m 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.

[0064] 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

[0065] 1 plating cell [0066] 10 plating cell main unit [0067] 11 opening portion [0068] 12 exhaust port [0069] 13 decompression pocket [0070] 14 supply port [0071] 15 drain port [0072] 16 decompression pipe [0073] 17 solution discharge pipe [0074] 2 pressing lid [0075] 20 pressing lid main unit [0076] 21 back surface decompress mechanism [0077] 22 decompression unit [0078] 23 decompression groove [0079] 3 reverse driving mechanism [0080] 4 press arm [0081] 50 drain receiving section [0082] 51 drainage tank [0083] 60 solution supply unit [0084] 61 solution storage tank [0085] 62 deaeration treatment tank [0086] 63 deaeration module