JP2004083961A - Jet type wafer plating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a jet type wafer plating apparatus capable of reducing the variation of plating thickness on the surface of a wafer. <P>SOLUTION: A current restriction resist 19 is applied to wiring 28 connecting cathode pins 15 and a plating source 18. The voltage (absolute value) applied to the cathode pin 15 low in contact resistance is automatically made low, and the voltage (absolute value) applied to the cathode pin 15 high in contact resistance is automatically made high. Even if there is a variation in the contact resistance between a wafer 12 and the cathode pins 15, the electric current of each cathode pin 15 can be uniformized, and the variation in the thickness of plating can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor wafer plating apparatus, and particularly to a jet-type wafer plating apparatus.
[0002]
[Prior art]
FIG. 3 is a partial sectional view of a conventional jet-type wafer plating apparatus 30. A semiconductor wafer 32 is placed above the jet cup 31 with a gap of several mm. The wafer 32 is fixed between the ring base 33 and the spring 34 with the plating surface facing down. The ring base 33 is made of an insulating material. Three cathode electrode pins 35 are embedded in the ring base 33. Cathode electrode pins 35 are electrically connected to the edge of wafer 32. In the middle of the jet cup 31 is a mesh anode 36. A plating current flows between the anode 36 and the wafer 32 through the plating solution 37. The cathode electrode pin 35 and the anode 36 are connected to a plating power supply 38, respectively. The jet cup 31 is provided in a plating tank 39. The bottom of the jet cup 31 is connected to a flow meter 41, a filter 42, and a plating solution circulation pump 43 outside the plating tank 39 by a pipe 40, and is again connected to the bottom of the plating tank 39 through them. A heater 44 is provided at the bottom of the plating tank 39 to keep the plating solution 37 at a constant temperature. The heater 44 is connected to a heater power supply 45.
[0003]
Next, a wafer plating method using the conventional jet-type wafer plating apparatus 30 will be described. First, the wafer 32 is placed on the ring base 33, and is pressed and fixed by a spring 34 from above. Next, the plating solution circulation pump 43 is turned on to circulate the plating solution 37. The plating solution 37 is heated to a set temperature (about 60 ° C. to 70 ° C.) by a heater 44 below the plating tank 39, passes through a plating solution circulation pump 43, a filter 42, and a flow meter 41 and enters the jet cup 31 from the bottom. The plating solution 37 rises through the gap of the anode 36 in the jet cup 31. When the plating solution 37 reaches the top of the jet cup 31, it strikes the wafer 32 with the force of the flow, overflows from the gap between the jet cup 31 and the ring base 33, flows down the side surface of the jet cup 31, and returns to the plating tank 39.
[0004]
Thus, the plating solution 37 circulates. In the meantime, a plating current flows through a circuit of plating power supply 38 → anode 36 → plating solution 37 → wafer 32 → cathode electrode pin 35 → plating power supply 38, and the metal in plating solution 37 is deposited on wafer 32. That is, the wafer 32 is plated.
[0005]
4 and 5 are a detailed perspective view and a partial cross-sectional view of the vicinity of a wafer 32, a ring base 33, and a cathode electrode pin 35 of a conventional jet-type wafer plating apparatus 30. The entire periphery of the wafer 32 is supported by a ring base 33. Three cathode electrode pins 35 are embedded in the ring base 33. The tip of the cathode electrode pin 35 is in contact with the wafer 32, and a plating current flows. The cathode electrode pin 35 is connected to a plating power supply 38 by a copper wiring 46 having a low resistance.
[0006]
The cathode electrode pin 35 is separated from the plating solution 37 by a ring base 33 (insulating material). This is because if the cathode electrode pins 35 are in direct contact with the plating solution 37, the cathode electrode pins 35 are plated, which is inconvenient.
[0007]
[Problems to be solved by the invention]
In the conventional jet-type wafer plating apparatus 30, the resistance of the wiring 46 connecting the cathode electrode pin 35 and the plating power supply 38 is minimized. This is to prevent a voltage drop in the wiring 46. Naturally, this is the case with a plating apparatus for ordinary metal parts. However, the situation is different in the case of a wafer plating apparatus.
[0008]
In the case of plating a metal component, the power supply wiring can be firmly attached, so that the contact resistance between the metal component and the wiring is low and does not vary. Therefore, although there is an advantage in reducing the resistance of the wiring, there is no disadvantage.
[0009]
However, in the case of the wafer 32, only the tip of the cathode electrode pin 35 is pressed against a plating base metal film (not shown) having a thickness of only 1 μm or less on the wafer 32. Since the metal film is thin and the wafer 32 is brittle, the cathode electrode pins 35 cannot be pressed strongly. In addition, in the case of the jet-type wafer plating, the plating solution 37 dynamically pushes up the wafer 32 and always tries to separate the wafer 32 and the cathode electrode pins 35. For this reason, the contact resistance between the wafer 32 and the cathode electrode pins 35 has an extremely large variation, and changes every moment. The measured value of the contact resistance is 0.5Ω to 20Ω, which is as large as 40 times.
[0010]
Although the resistance of the wiring 46 is 1Ω or less, the contact resistance varies between 0.5Ω and 20Ω by the cathode electrode pins 35. Therefore, even if the same plating voltage is applied to the three cathode electrode pins 35, each of the cathode electrode pins 35 The current flowing through the device differs greatly. Therefore, the plating becomes thick near the cathode electrode pin 35 having a low contact resistance, and the plating becomes thin near the cathode electrode pin 35 having a high contact resistance. As a result, the distribution of the plating thickness on the wafer surface 32 is not uniform. According to actual measurements, the plating thickness varies by about ± 20%.
[0011]
Furthermore, since the contact resistance cannot be controlled, it is very difficult to determine the standard plating time.
[0012]
SUMMARY OF THE INVENTION An object of the present invention is to realize a jet-type wafer plating apparatus capable of reducing the variation in plating thickness on the wafer surface even if the contact resistance between the wafer and the cathode electrode pins is unavoidable.
[0013]
[Means for Solving the Problems]
In the jet-type wafer plating apparatus of the present invention, a current limiting resistor is provided in the middle of the branch portion of the wiring connecting the cathode electrode pin and the plating power supply. In this way, when a large current flows through a certain cathode electrode pin by chance because the contact resistance of the certain cathode electrode pin is lower than that of the other cathode electrode, the voltage (absolute value) of the cathode electrode pin drops due to the function of the current limiting resistor. . As a result, the current flowing through the cathode electrode pin is reduced. Thus, the currents of the three cathode electrode pins are equalized. The effect of equalizing the current of the cathode electrode pin as described above is the same regardless of the number of cathode electrode pins.
[0014]
Of course, if a plating power supply (constant current power supply) is connected to each cathode electrode pin one by one, the currents of all the cathode electrode pins can be made exactly equal. However, doing so increases the cost of the plating power supply in proportion to the number of cathode electrode pins. When the wafer is 5 inches, three cathode electrode pins are sufficient, but when the wafer is 8 inches to 10 inches, 6 to 12 cathode electrode pins are required. On the other hand, it is impossible to use 6 to 12 plating power supplies in terms of cost.
[0015]
If the current limiting resistor is inserted in the middle of the branch portion of the wiring as in the present invention, only one plating power source is required no matter how many cathode electrode pins are provided, and the current limiting resistor is inexpensive, so that there is a problem of cost. Will not happen. Therefore, it is practical.
[0016]
The invention according to claim 1 is a jet-type wafer plating apparatus for applying a plating current by pressing a cathode electrode pin against a wafer while continuously applying a flow of a plating solution to a plating surface of the wafer to perform electroplating on the wafer. , Wherein a current limiting resistor is provided in the middle of a branch portion of a wiring connecting a cathode electrode pin and a plating power source.
[0017]
According to a second aspect of the present invention, there is provided the jet-type wafer plating apparatus according to the first aspect, wherein the value of the current limiting resistance is 10Ω to 100Ω.
[0018]
According to a third aspect of the present invention, in the jet type wafer plating apparatus according to the first aspect, the value of the current limiting resistance is made different depending on the statistical manner of the contact resistance of the cathode electrode pin. It is a type wafer plating apparatus.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a partial sectional view of a jet type wafer plating apparatus 10 of the present invention. A semiconductor wafer 12 is placed above the jet cup 11 with a gap of several mm. The wafer 12 is fixed between the ring base 13 and the spring 14 with the plating surface facing down. The ring base 13 is made of an insulating material. Three cathode electrode pins 15 are embedded in the ring base 13. The cathode electrode pins 15 are electrically connected to the edge of the wafer 12. In the middle of the jet cup 11 is a net-like anode 16. A plating current flows between the anode 16 and the wafer 12 through the plating solution 17. The cathode electrode pin 15 and the anode 16 are connected to a plating power source 18, respectively. A current limiting resistor 19 is provided between the cathode electrode pin 15 and the plating power supply 18. The feature of the present invention is that the current limiting resistor 19 is inserted. This will be described in detail later.
[0020]
The jet cup 11 is provided in a plating tank 20. The bottom of the jet cup 11 is connected by a pipe 21 to a flowmeter 22, a filter 23, and a plating solution circulation pump 24 outside the plating tank 20, through which they are again connected to the bottom of the plating tank 20. A heater 25 is provided at the bottom of the plating tank 20 to keep the plating solution 17 at a constant temperature. The heater 25 is connected to a heater power supply 26.
[0021]
Next, a method for plating a wafer 12 using the jet-type wafer plating apparatus 10 of the present invention will be described. First, the wafer 12 is placed on the ring base 13, and is pressed and fixed by a spring 14 from above. Next, the plating solution circulation pump 24 is turned on to circulate the plating solution 17. The plating solution 17 is heated to a set temperature (about 60 ° C. to 70 ° C.) by a heater 25 below the plating tank 20, passes through the plating solution circulation pump 24, the filter 23, and the flow meter 22 and enters the jet cup 11 from the bottom. The plating solution 17 rises through the gap of the anode 16 in the jet cup 11. When the plating solution 17 reaches the top of the jet cup 11, it strikes the wafer 12 with the force of the flow, overflows from the gap between the jet cup 11 and the ring base 13, flows down the side surface of the jet cup 11, and returns to the plating tank 20.
[0022]
Thus, the plating solution 17 circulates. In the meantime, a plating current flows through a circuit of plating power supply 18 → anode 16 → plating solution 17 → wafer 12 → cathode electrode pin 15 → plating power supply 18, and the metal in plating solution 17 is deposited on wafer 12. That is, the wafer 12 is plated.
[0023]
FIG. 2 is a detailed perspective view of the vicinity of the wafer 12, the ring base 13, and the cathode electrode pins 15 of the jet type wafer plating apparatus 10 of the present invention. The wafer 12 is supported by a ring base 13 all around. Three cathode electrode pins 15 are embedded in the ring base 13. The tip of the cathode electrode pin 15 is in contact with the wafer 12, and a plating current flows. The cathode electrode pin 15 is connected to the plating power supply 18 by a copper wire 27 having a low resistance. The wiring 27 is one near the plating power supply 18, but is branched into three near the cathode electrode pin 15, and a current limiting resistor 19 is inserted in series at the branch. It is a feature of the present invention that the current limiting resistor 19 is inserted. The value of the current limiting resistor 19 is suitably from 10Ω to 100Ω. Basically, the value of each current limiting resistor 19 may be the same, but if the value of the contact resistance is statistically biased by the cathode electrode pin 15, the value of the current limiting resistor 19 is made different accordingly. Is better.
[0024]
The operation and effect of the current limiting resistor 19 are as follows. Since a contact resistance of a certain cathode electrode pin 15 is lower than that of another, when a large current flows through the branch wiring 28, a voltage drop due to the current limiting resistor 19 of the branch wiring 28 becomes larger than the other. Therefore, the voltage (absolute value) of the cathode electrode pin 15 drops from the others. As a result, the current flowing through the cathode electrode pin 15 decreases. That is, the voltage (absolute value) applied to the cathode electrode pin 15 having a low contact resistance automatically decreases, and the voltage (absolute value) applied to the cathode electrode pin 15 having a high contact resistance automatically increases. Thus, the currents of the three cathode electrode pins 15 are equalized. This reduces the variation in plating thickness on the surface of the wafer 12.
[0025]
According to the present invention, the variation of the plating thickness is reduced to about 1/3 of the conventional one. Further, since the variation in plating thickness was reduced, it became easier to determine the standard plating time.
[0026]
【The invention's effect】
By inserting the current limiting resistor 19 in the wiring 28 connecting the cathode electrode pin 15 and the plating power supply 18, the voltage (absolute value) applied to the cathode electrode pin 15 having a low contact resistance is automatically reduced, and the cathode electrode having a high contact resistance. The voltage (absolute value) applied to pin 15 automatically increases. Thus, even if the contact resistance between the wafer 12 and the cathode electrode pins 15 varies, the current of each cathode electrode pin 15 can be equalized, and the variation in the plating thickness on the surface of the wafer 12 can be reduced. This method requires only one plating power source 18 even if the number of cathode electrode pins 15 increases, and the current limiting resistor 19 is inexpensive, so that the cost is low and practical.
[Brief description of the drawings]
1 is a partial sectional view of a jet-type wafer plating apparatus 10 of the present invention. FIG. 2 is a perspective view of a part of the jet-type wafer plating apparatus 10 of the present invention. FIG. 3 is a part of a conventional jet-type wafer plating apparatus 30. FIG. 4 is a perspective view of a part of a conventional jet-type wafer plating apparatus 30. FIG. 5 is a cross-sectional view of a part of a conventional jet-type wafer plating apparatus 30.
Reference Signs List 10 Jet-type wafer plating apparatus 11 of the present invention 11 Jet cup 12 Wafer 13 Ring base 14 Spring 15 Cathode electrode pin 16 Anode 17 Plating solution 18 Plating power supply 19 Current limiting resistor 20 Plating tank 21 Piping 22 Flow meter 23 Filter 24 Plating solution circulation pump Reference Signs List 25 heater 26 heater power supply 27 wiring 28 branch wiring 30 conventional jet-type wafer plating apparatus 31 jet cup 32 wafer 33 ring base 34 spring 35 cathode electrode pin 36 anode 37 plating solution 38 plating power supply 39 plating tank 40 piping 41 flow meter 42 filter 43 Plating solution circulation pump 44 Heater 45 Heater power supply 46 Wiring

Claims (3)

While continuously applying a flow of a plating solution to the plating surface of the wafer, a cathode current pin is pressed against the wafer to supply a plating current, and a jet-type wafer plating apparatus for performing electroplating on the wafer is provided. A jet-type wafer plating apparatus characterized in that a current limiting resistor is provided in the middle of a branch portion of a wiring connecting a plating power supply. The jet-type wafer plating apparatus according to claim 1, wherein the value of the current limiting resistance is 10Ω to 100Ω. 2. A jet-type wafer plating apparatus according to claim 1, wherein the value of said current limiting resistance is made different according to a statistical manner of a contact resistance of said cathode electrode pin.

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