JP2004250723A - Plating electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating electrode capable of preventing contamination by the diffusion of precious metals and dust etc., and forming a uniform plating film. <P>SOLUTION: The plating electrode is formed by using Au 10 as a base layer, disposing a surface layer containing Ni 30 on the surface which comes in contact with an object 40 to be plated, such as a semiconductor wafer, and further disposing an NiAu 20 for improving an adhesivity between the base layer and the surface layer. The electric resistance can be reduced by the Au 10, and the electrical contact with the object 40 to be plated can be well maintained by the malleability/ductility of the Au 10. Also, the contamination by the diffusion of the Au 10 can be prevented by disposing the Ni 30 on the surface, and the resistance to chemicals can be enhanced by the passive film formed on a Ni surface. Since the Ni 30 and the Au 10 form an alloy at a relatively low temperature, the adhesiveness between the Ni 30 and the Au 10 is well maintained and the high wear resistance can be obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a structure of a cathode electrode used in an electrolytic plating step in a semiconductor element manufacturing process, and more particularly to a structure of a cathode electrode used in an electrolytic plating step in forming a barrier metal between a solder and a pad.
[0002]
[Prior art]
In manufacturing a semiconductor element, an electrolytic plating method is used as a method for forming a barrier metal layer or a wiring layer between solder and a pad. In the electroplating method, an object to be plated such as a semiconductor wafer is brought into contact with a chemical solution, and a plating electrode (cathode electrode) is connected to the object to be plated and energized to deposit metal dissolved in the chemical solution on the surface of the object to be plated. The cathode layer is made of a material that satisfies requirements such as excellent corrosion resistance to chemicals, low electrical resistance, and good electrical contact with the object to be plated. There is a need.
[0003]
Materials satisfying such requirements include noble metals such as Au and Au alloys, Pt and Pt alloys, alloys with noble metals, and carbon-based materials. For example, as shown in FIG. A cathode having a structure, a cathode having an Au thin film 100 formed on a wafer contact surface of a base material 90 as shown in FIG. 3B, and the like have been used.
[0004]
When a noble metal such as Au or Pt is used as the cathode electrode, there is a problem that the noble metal is contact-transferred from the cathode electrode to the semiconductor element to cause noble metal contamination. These noble metals are diffused into the inside of the semiconductor element by a heat treatment step or the like in the semiconductor element manufacturing process, and form an electrically deep impurity level to deteriorate the electric characteristics of the semiconductor element. For this reason, it is necessary to remove the transferred noble metal before diffusing into the inside of the semiconductor element.However, the noble metal has excellent corrosion resistance and a low vapor pressure of the reactant, so that the liquid or gas phase used in the manufacture of the semiconductor element is not used. It is difficult to remove in the washing step. Therefore, when Au or Pt is used, there arises a problem that the electrical characteristics of the semiconductor element particularly near the contact portion are deteriorated and the yield is reduced.
[0005]
On the other hand, when a carbon-based electrode is used as a cathode electrode to prevent diffusion of a noble metal into the inside of a semiconductor element, the above-described metal contamination does not occur, but the carbon-based material is easily worn and dust is generated. There is a disadvantage that it is easy. In a manufacturing process of a semiconductor device, the generation of dust causes a reduction in yield. Therefore, when a carbon-based material is used for a cathode electrode, there is a problem that the manufacturing yield of semiconductor elements is reduced.
[0006]
Therefore, a cathode electrode having a structure in which the surface of a noble metal material is coated with various materials has been studied. For example, in JP-A-2000-150558, JP-A-2001-115298, and the like, as shown in FIG. 3C, the bonding property with Au is formed on a base layer made of Au10 having excellent electric conductivity. A cathode electrode having a laminated structure in which an intermediate layer made of Ti110 excellent in the above is formed, and further, a wafer contact layer made of any of TiN, WN, TaN, W, and Ta is formed in order to suppress oxidation of Ti. By making the contact portion with the plating object any of TiN, WN, TaN, W, and Ta, contamination of the plating object due to the diffusion of Au10 is prevented.
[0007]
Although not shown, JP-A-2002-69698 discloses that the cathode material is formed of one or more substances selected from the group consisting of spring steel, Ni, Ti, Inconel, Cu and stainless steel. A cathode electrode structure using an elastic body is disclosed. In this structure, the electrode itself is made of a material different from a noble metal such as Au to prevent noble metal contamination.
[0008]
[Patent Document 1]
JP-A-2000-150558 (pages 2-3, FIG. 1)
[Patent Document 2]
JP 2001-115298 A (pages 2-3, FIG. 1)
[Patent Document 3]
JP-A-2002-69698 (pages 4 to 10, FIG. 8)
[0009]
[Problems to be solved by the invention]
However, in the structures described in JP-A-2000-150558 and JP-A-2001-115298, TiN, WN, TaN, W, and Ta have high hardness and are hardly deformed with respect to the object to be plated. There is a problem in that electrical contact with the object is deteriorated, and the uniformity of the potential distribution in the region to be plated is deteriorated. Further, these materials have a high electric specific resistance of 10 μΩcm or more except for W, and this high electric specific resistance also causes deterioration of the uniformity of the potential distribution in the region to be plated. Since the physical properties and deposition rate of the plating film strongly depend on the potential distribution, when TiN, WN, TaN, W, and Ta are used, good in-plane properties such as crystallinity of the plating film and film thickness are obtained. Uniformity cannot be obtained. In addition, TiN, WN, TaN, W, and Ta of the wafer contact layer, except for TiN, are difficult to form an alloy or a compound with the base Ti, so that they have poor adhesion to the base Ti, and thus peeling of the wafer contact layer occurs. As a result, there is a problem that dust and scratches are generated, and the electrode from which the wafer contact layer has peeled must be frequently replaced.
[0010]
The same applies to the structure described in JP-A-2002-69698. When the cathode electrode is made of spring steel, Ni, or the like, the contact resistance increases due to the high hardness of the electrode material. Therefore, the above-mentioned publication discloses a method in which the cathode electrode is made to have an elastic structure to improve the contact resistance, and the cathode electrode is deformed according to the shape of the object to be plated. Is macroscopic, and in order to reduce the contact resistance, it is necessary to increase the contact area at the atomic level by causing microscopic deformation. Since the cathode electrode material described in the above publication has a high hardness, in order to increase the contact area at the atomic level, it is necessary to press the electrode to such an extent that the electrode scrapes the object to be plated. This causes a problem that the yield of the semiconductor element is deteriorated and the maintainability is deteriorated. Further, if the pressing is performed to such an extent that abrasion does not occur, good contact between the cathode electrode and the object to be plated cannot be ensured, so that there is a problem that the variation in electric characteristics between chips is increased.
[0011]
The present invention has been made in view of the above problems, and a main object of the present invention is to provide a plating electrode capable of preventing contamination of a noble metal by diffusion or dust, and forming a uniform plating film. Is to do.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a plated electrode of the present invention is a plated electrode that contacts a part of a plated object and supplies a plating current to the plated object, wherein the plated electrode is at least the plated object. And a base layer made of a material containing Au or Pt from the side of the object to be plated.
[0013]
In the present invention, a configuration may be adopted in which an adhesion layer for improving the adhesion between the base layer and the surface layer is provided between the base layer and the surface layer.
[0014]
In the present invention, the base layer may be made of Au and the adhesion layer may be made of an alloy of Ni and Au, or the base layer may be made of Pt and the adhesion layer may be made of Ti. it can.
[0015]
As described above, according to the present invention, with the above-described configuration, there is no contamination of the object to be plated with a noble metal, good electrical connection between the object to be plated and the plating electrode, high corrosion resistance to the plating solution, and low abrasion. An electrode can be realized.
[0016]
The reason why such an effect is obtained is that the use of a material containing Ni in a portion in contact with the object to be plated can prevent contamination of the object to be plated with a noble metal. In addition, in order to maintain the electrical connectivity between the plating object and the plating electrode, it is desirable to slightly deform the plating electrode when it comes into contact with the plating object to increase the contact area. When a material containing Au, which is rich in malleability and ductility, is used, if the material combined therewith is sufficiently thin, it can be deformed in accordance with the shape of the object to be plated, so that good electrical connectivity can be ensured. Further, Ni forms a passivation film on the surface, so that the resistance to chemicals can be increased. In addition, since the combination of Ni and Au or Pt is a combination that forms an alloy at a relatively low temperature, the adhesion between the two can be enhanced and high wear resistance can be obtained. In addition, by inserting those alloys at the interface between Ni and Au or Pt, it is possible to further improve the wear resistance by securing higher adhesion.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
As described in the related art, various materials and structures have been proposed for the cathode electrode used in the electrolytic plating step. However, in the cathode electrode described in JP-A-2000-150558 and JP-A-2001-115298, The hardness of the wafer contact layer is high and it is difficult to deform, so the electrical contact with the plating object is poor, the in-plane uniformity of the plating film is poor, and the adhesion between the wafer contact layer and the underlying metal is poor, and the wafer contact There is a problem that the layer is easily peeled off, and in the cathode electrode described in JP-A-2002-69698, the electrical contact with the object to be plated is similarly poor. There is a problem that dust is generated and the yield of semiconductor elements is deteriorated.
[0018]
As described above, the characteristics and in-plane uniformity of the plated film to be formed depend on the material and structure used to form the cathode electrode. Various factors such as the effect of the material, hardness of the material, adhesion to the base, chemical resistance, and electrical resistance of the material must be considered, and it is not easy to select a material or structure that satisfies all of these factors. Therefore, the inventor of the present application uses a noble metal having a small electric resistance as a material of the base layer in order to uniformly supply a plating current, and has an adhesive property with the base layer as a surface layer for preventing contamination due to diffusion of the noble metal. Materials were selected under the basic structure of using a metal that forms a passivation film that is good and has excellent chemical resistance.
[0019]
As a result, the plating electrode has a structure in which Au or Pt is used as a base layer, and a surface layer containing Ni is provided on the contact surface side with a plating object such as a semiconductor wafer, or between the base layer and the surface layer. By adopting a structure in which an adhesion layer such as NiAu or Ti is provided to improve adhesion, contamination by precious metals can be prevented, contact resistance can be reduced, and wear resistance can be improved. confirmed. In addition, Ni itself is a known material, but by forming the Ni layer thinly on the base layer of the noble metal, the electrical contact with the object to be plated can be improved without impairing the malleability and ductility of the base layer. The effect that the noble metal can be stably prevented by the passivation film by the passivation film is a novel effect found by the knowledge of the present inventors.
[0020]
【Example】
In order to describe the above-described embodiment of the present invention in more detail, an embodiment of the present invention will be described with reference to the drawings.
[0021]
[Example 1]
First, a plating electrode according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the structure of a plated electrode according to the first embodiment.
[0022]
As shown in FIG. 1, when subjecting an object to be plated 40 such as a semiconductor wafer to electrolytic plating, a plating electrode is arranged on a region separated by a plating seal 50, and a portion of the object to be plated 40 to which plating is applied is placed. It is immersed in the plating solution 60, and the plating current is supplied by bringing the end of the plating object 40 into contact with the plating electrode. As this plating electrode, Ni30 or a surface layer containing Ni30, on which a passivation film is formed, is directly formed on a base layer made of Au or Pt (Au10 in the figure), or an adhesion layer made of NiAu20 is formed. It has a laminated structure (a three-layer structure of Au10, NiAu20, and Ni30 in the figure) which is disposed through the interposition.
[0023]
The film thickness of Ni30 and NiAu20 may be any thickness that can cover Au10 as a base layer and does not hinder the malleability and ductility of Au10. About 0.0 μm, and Ni 30 is preferably about 0.5 to 10 μm. NiAu20 may be deposited on Au10, or Ni30 may be deposited on Au10 and then alloyed by heat treatment.
[0024]
With such a structure, the electrical resistance can be reduced by Au10, and the electrical contact with the object to be plated 40 can be kept good by its malleability and ductility. Further, by arranging Ni30 on the surface, contamination due to diffusion of Au10 can be prevented, and resistance to a chemical solution can be increased by a passivation film. Further, since Ni30 and Au10 or Pt are alloyed at a relatively low temperature, the adhesion between Ni30 and Au10 or Pt can be kept good, and high wear resistance can be obtained.
[0025]
The base layer is not limited to Au or Pt, but may be a metal having a small electric resistance and easily forming an alloy with Ni30. FIG. 1 shows a part of the plating electrode, and it is not necessary that all of the plating electrode have the above-described two-layer or three-layer structure. Alternatively, the other portion may be made only of Au10, or may have a structure in which a protective film is formed on Ni30.
[0026]
[Example 2]
Next, a plating electrode according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically illustrating a structure of a plated electrode according to the second embodiment.
[0027]
As shown in FIG. 2, the plated electrode of the present embodiment includes a base layer made of Au or Pt (Pt70 in the figure) and a Ni30 or a surface layer containing Ni30 on which a passivation film is formed. It has a laminated structure (three-layer structure of Pt70, Ti80, and Ni30 in the figure) provided directly or via an adhesion layer made of Ti80. The thickness of this Ti80 may be a thickness capable of covering the base layer Pt70 as in the first embodiment, and is preferably about 0.1 to 1.0 μm.
[0028]
With such a structure, the electric resistance can be reduced by the Pt 70, and the electric contact with the plating object 40 can be kept good. Further, by arranging Ni30 on the surface, it is possible to prevent contamination due to diffusion of Pt70 and to enhance resistance to a chemical solution. Further, by interposing Ti80 between Ni30 and Pt70, good adhesion between Ni30 and Pt70 can be maintained, and high wear resistance can be secured.
[0029]
As in the first embodiment, it is not necessary that all of the plating electrodes have the above-described two-layer or three-layer structure. A structure in which only Pt 70 is used or a protective film is formed on Ni 30 may be used.
[0030]
【The invention's effect】
As described above, according to the structure of the plated electrode of the present invention, the following effects can be obtained.
[0031]
A first effect of the present invention is that contamination of a semiconductor element by a noble metal can be prevented and resistance to a chemical solution such as a plating solution can be increased.
[0032]
The reason is that a surface layer containing Ni that forms a passivation film on the surface is formed at least on a portion of the base layer made of a noble metal that is in contact with the object to be plated.
[0033]
A second effect of the present invention is that it is possible to maintain good electrical contact with the object to be plated.
[0034]
The reason is that the electrical resistance is reduced by using Au or Pt as the base layer, and the adhesion layer of Ni, NiAu, Ti or the like formed on the base layer is formed with a predetermined film thickness, thereby expanding the base layer. This is because the plating electrode can be deformed according to the shape of the object to be plated without impairing the ductility and ductility.
[0035]
A third effect of the present invention is that high wear resistance can be obtained.
[0036]
The reason is that the combination of Ni and Au or Pt is a combination that forms an alloy at a relatively low temperature, and the adhesion can be improved by forming an alloy of Ni and Au or Pt. Further, by interposing an adhesion layer such as NiAu or Ti at the interface between Ni and Au or Pt, higher adhesion can be ensured.
[0037]
By performing electroplating using the plating electrode having such a material and structure, in-plane uniformity such as physical properties and film thickness of the plating film can be increased, and variation in electric characteristics between chips can be suppressed. The production yield of semiconductor elements can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view schematically showing a part of a structure of a plated electrode according to a first embodiment of the present invention.
FIG. 2 is a sectional view schematically showing a part of the structure of a plated electrode according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the structure of a conventional plated electrode.
[Explanation of symbols]
10 Au
20 NiAu
30 Ni
40 Plating object 50 Plating seal 60 Plating solution 70 Pt
80 Ti
90 Base material 100 Au thin film 110 Any of TiN, Ta, TaN, W, WN

Claims (4)

A plating electrode that contacts a part of the object to be plated and supplies a plating current to the object to be plated,
The plating electrode includes a surface layer made of a material containing Ni and a base layer made of a material containing Au or Pt from at least a region in contact with the object to be plated, from the side of the object to be plated. Plating electrode. The plating electrode according to claim 1, wherein an adhesion layer for improving adhesion between the base layer and the surface layer is provided between the base layer and the surface layer. The plating electrode according to claim 2, wherein the base layer is made of Au, and the adhesion layer is made of an alloy of Ni and Au. The plating electrode according to claim 2, wherein the base layer is made of Pt, and the adhesion layer is made of Ti.

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