JP3639105B2 - Wafer plating method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wafer plating method capable of uniformly forming plating on a wafer surface.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as shown in FIG. 4, a wafer plating apparatus for performing electrolytic plating on a wafer surface includes a wafer 100 and a flat plate-like anode that is installed so as to face the wafer 100 surface in parallel. The surface of the wafer 100 is plated by immersing the electrode 110 and energizing between the wafer 100 and the anode electrode 110.
[0003]
[Problems to be solved by the invention]
However, in this plating apparatus, when an electric field is applied to perform plating on the wafer 100, there is a difference between the potential gradient around the outer peripheral portion of the wafer 100 and the potential gradient around the central portion. There was a possibility that the film thickness of the plating in each part would become non-uniform.
[0004]
In order to avoid this and to uniformly plate the surface of the wafer 100, it is necessary to adjust the potential of each part near the surface of the wafer 100 so as to be as uniform as possible. Methods such as adjusting the size of the electrode or inserting a dielectric shielding plate between the anode electrode 110 and the wafer 100 have been used.
[0005]
However, the range of the electric field that can be adjusted by these methods is narrow, and the electric field cannot be freely adjusted on the surface of the wafer 100. In particular, as the diameter of the wafer 100 increases, the difference in potential between the central portion and the outer peripheral portion increases, so that it is difficult to uniformly form a plating with a uniform potential distribution over a wide range of the entire surface of the wafer 100. .
[0006]
The present invention has been made in view of the above-described points, and an object of the present invention is to adjust the electric field of each part over a wide range on the wafer surface, thereby forming a wafer having a uniform film thickness on the wafer surface. It is to provide a plating method.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention immerses a wafer in an electrolytic plating solution and disposes an anode electrode in parallel with the wafer at a predetermined distance from the wafer. The plating on the wafer surface is completed while the anode electrode is gradually moved away from the wafer from the position closest to the wafer to the position farthest away from the wafer while maintaining the current value of the current flowing between the anode electrodes constant ; did.
In the present invention, the anode electrode has a shape substantially similar to that of the wafer.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an overall schematic view showing a plating apparatus used in the present invention. As shown in the figure, this plating apparatus is configured by immersing a wafer 100 and an anode electrode 30 in an electrolytic plating solution 20 of a plating tank 10 at a predetermined distance from each other so that their opposing surfaces are parallel to each other. ing. Each component will be described below.
[0009]
The plating tank 10 is provided with an overflow tank 13 on its outer periphery, and the plating tank 10 and the overflow tank 13 are connected by a pipe 21 to which a pump 15, a constant temperature unit 17 and a filter 19 are attached.
[0010]
The wafer 100 is substantially disk-shaped, and is configured such that one surface thereof is exposed in the electrolytic plating solution 20 by holding the outer periphery thereof with a wafer holding member 101.
[0011]
On the other hand, the anode electrode 30 has an outer shape similar to the outer shape of the wafer 100, that is, a disk shape having substantially the same size as the wafer 100 (in this embodiment, the outer dimension of the anode electrode 30 is slightly smaller). Small).
[0012]
The anode electrode 30 is configured to be movable in a direction perpendicular to the surface of the wafer 100 in the electrolytic plating solution 20 by a predetermined driving means 40. At this time, the central axis of the wafer 100 and the central axis of the anode electrode 30 coincide with each other.
[0013]
Next, the operation of this plating apparatus will be described. First, the anode electrode 30 is set at a position closest to the wafer 100 (indicated by a dotted line), and the electroplating solution 20 that has passed through the constant temperature unit 17 and the filter 19 is driven into the plating tank 10 by driving the pump 15. Supplied from the bottom, overflows into the overflow tank 13 and circulates.
[0014]
Then, energization is performed between the wafer 100 and the anode electrode 30 to start plating on the surface of the wafer 100.
[0015]
FIG. 2 is an equipotential diagram showing the state of the electric field around the wafer 100 and the anode electrode 30 when the anode electrode 30 is approaching the wafer 100 at the beginning of plating. As shown in the figure, when the anode electrode 30 is approaching the wafer 100, the potential gradient is higher in the central portion than in the outer peripheral portion of the wafer 100. Therefore, in this state, the central portion of the wafer 100 is formed thicker than the outer peripheral portion.
[0016]
Then, the plating is continued while the anode electrode 30 is gradually separated from the wafer 100 by the driving means 40. When the anode electrode 30 reaches the position farthest from the wafer 100 (the position indicated by the solid line in FIG. 1), the plating is performed. Make it complete.
[0017]
FIG. 3 is an equipotential diagram showing the state of the electric field around the wafer 100 and the anode electrode 30 when the anode electrode 30 is at a predetermined position away from the wafer 100. As shown in the figure, when the anode electrode 30 is separated from the wafer 100, the potential gradient gradually increases at the outer peripheral portion as compared with the central portion of the wafer 100. If the anode electrode 30 is further moved away from the wafer 100 from the position shown in FIG. 3 to the position shown by the solid line in FIG. 1, the potential gradient is higher at the outer peripheral portion than at the center portion of the wafer 100. Therefore, as the anode electrode 30 moves away from the wafer 100, the outer peripheral portion of the wafer 100 is formed with a thicker plating than the central portion.
[0018]
In this manner, the plating at the center of the wafer 100 is first formed thicker and the anode electrode 30 is moved so that the outer peripheral plating is gradually thickened. The film thickness is made uniform.
[0019]
In this embodiment, the voltage is controlled to decrease as the anode electrode 30 is separated from the wafer 100, that is, as the plating time elapses. This is because when the plating is formed on the wafer 100, the resistance value at the time of energization gradually decreases from the beginning of the plating because the plating film thickness increases. For this reason, when the voltage value is kept constant, the value of the flowing current gradually increases.
[0020]
On the other hand, since the plating film thickness can be easily obtained by the product of the flowing current value and time, the current value should be kept constant (because the plating film thickness can be controlled only by managing the time). Further, when the current density is changed by changing the current value, the characteristics of the formed plating itself (film surface state, density, etc.) change. Therefore, in this embodiment, the voltage value is controlled to change as described above in order to keep the current value constant.
[0021]
The reason why the anode electrode 30 is moved away from the position approaching the wafer 100 in the above embodiment is as follows.
[0022]
That is, normally, when the wafer 100 is held by the wafer holding member 101, the wafer 100 is energized by bringing an energizing pin (not shown) provided on the wafer holding member 101 into contact with the outer periphery of the wafer 100. For this reason, the outer peripheral portion of the wafer 100 close to the energizing pins has a smaller electric resistance than the central portion of the wafer 100, and therefore, even if the potential gradient of both portions is the same, the outer peripheral portion is thicker. There is a tendency to go. Therefore, at the beginning of plating, the anode electrode 30 is first brought close to the wafer 100, so that the plating film thickness in the central part of the wafer 100 is made thicker than the plating film thickness in the outer peripheral part as described above. This is because the resistance value up to the energizing pins is made uniform by making the electrical resistance of the outer periphery smaller than the electrical resistance of the outer peripheral portion, and the plating film thickness on the entire surface of the wafer 100 is more effectively made uniform.
[0023]
【The invention's effect】
As described in detail above, the present invention has the following excellent effects. (1) Since the surface of the wafer is plated by energizing between the wafer and the anode electrode while changing the distance between the wafer and the anode electrode in the electrolytic plating solution, a wide range on the wafer surface during plating. Thus, the electric field of each part can be adjusted, and plating with a uniform film thickness can be formed on the wafer surface.
[0024]
(2) Since the shape of the anode electrode is substantially similar to the shape of the wafer, the state of the electric field is substantially symmetric with respect to the line connecting the central portions of the wafer and the anode electrode, and a more uniform plating film is obtained. Can do.
[0025]
(3) Since the current value when plating on the wafer is made constant and the anode electrode is gradually moved away from the wafer, the plating film thickness can be more easily and effectively made uniform over the entire wafer surface. I can plan.
[Brief description of the drawings]
FIG. 1 is an overall schematic view showing a plating apparatus used in the present invention.
FIG. 2 is an equipotential diagram showing a state of an electric field around the wafer 100 and the anode electrode 30 when the anode electrode 30 approaches the wafer 100. FIG.
3 is an equipotential diagram showing the state of the electric field around the wafer 100 and the anode electrode 30 when the anode electrode 30 is at a predetermined position away from the wafer 100. FIG.
FIG. 4 is an overall schematic view showing a conventional plating apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Plating tank 20 Electrolytic plating solution 30 Anode electrode 40 Driving means 100 Wafer

Claims (2)

Immerse the wafer in the electrolytic plating solution and place the anode electrode in parallel with the wafer at a predetermined distance from the wafer, and set the current value of the current that flows between the wafer and the anode electrode in the electrolytic plating solution. A method for plating a wafer, characterized in that plating on the wafer surface is completed while the anode electrode is gradually moved away from the wafer from a position closest to the wafer to a position farthest away from the wafer while maintaining constant .   2. The wafer plating method according to claim 1, wherein the shape of the anode electrode is substantially similar to the shape of the wafer.

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