JPH01198017A - Formation of external electrode of wafer - Google Patents

Abstract

PURPOSE:To reduce the nonuniformity of difference in height of an external electrode in the center and the periphery of a wafer, by a method wherein the wafer having a plated resist layer of a prescribed thickness or more wherein an external electrode forming part is opened is set in a plating apparatus and a plating liquid of a specified flow rate is jetted thereto to form the electrode electrode. CONSTITUTION:A plated resist layer 37 is formed 10mum or more thick on a gold evaporated layer 36 on the upper most surface of a wafer 30, exposure and development are conducted with a mask provided thereon, and openings 37a... are made to correspond to pad parts 34.... Next, the wafer is set, with the plated resist layer 37 side down, on a plating-liquid blocking wall 27a of a head ring 27 in a plating apparatus 20. Then a part of the gold evaporated layer 36 formed in the peripheral edge part of the wafer 30 is brought into contact with the fore end of a cathode pin 28. A plating liquid 21 is sent into a cup 24 through a channel 25 by a jetting pump 26 and jetted onto the plated surface of the wafer 30 at a flow rate of 300cc/cm<2> or above per minute, and current is made to flow to plate the cathode pin 28 and an anode electrode plate 29. Then plating is made in the openings 37a... and an external electrode is formed uniformly.

Description

[Detailed description of the invention] [Industrial application field] The invention relates to a method for forming external electrodes on a wafer.

[Prior Art] Conventionally, a plating apparatus for forming external electrodes on a wafer is
It is configured as shown in the figure. That is, in this plating device fil, a cup 4 through which plating solution 3 flows is provided in a plating tank 2, an upper M5 is attached to the top of the plating tank 2 so that it can be opened and closed, and the plating tank 2 and cup 4 are Road 6
A jet pump 7 installed in this liquid path 6 communicates with the
As a result, the plating solution 3 in the plating tank 2 is sent into the cup 4 and flows into a jet. In this case, the upper part of the cup 4 is provided with a hem VIJ' ring 9 for holding the wafer 8 a21, and a pair of opposing cathode pins 1O are provided on both sides thereof.
110 is attached, and 7 is attached to the bottom side of the cup 4.
A node electrode plate 11 is arranged. The top cover 5 also includes cathode terminals 12 and 12 connected to a power supply device (not shown).
and an anode terminal 13 are provided, and each terminal 12
．． 13, the cathode terminal 12 and 12 are connected to the cathode bin 1.
0°10 is directly connected, and the lead wire 1 is connected to the anode terminal 13.
Seven node electrode plates 11 are connected via 3a.

When forming the external electrodes 8a on the surface of the wafer 8 using such a plating equipment 211, a plating resist layer 8b having a thickness of agm is formed on the surface of the wafer 8 shown in FIG. The resist layer 8b is etched to form an opening, and the pad portion 8C is exposed within the opening. Then, the wafer 8 formed in this way is set upside down, that is, with the plating resist layer 8b formed on the surface of the wafer 8 facing down, on the head ring 9 in the plating apparatus l, and the peripheral edge of the wafer 8 is placed on the head ring 9. The formed plating electrode (not shown) is connected to a power pin 10 provided on the top of the cup 4.
Touch the tip of the to.

Thereafter, the jet pump 7 is operated to send the plating liquid 3 in the plating bath 2 into the cup 4 and make it jet, so that the plating liquid 3 is sprayed onto the plating surface of the wafer 8. In this state, when a plating current is applied to the cathode pins 10.10 and the 7-node electrode plate 11, an external electrode 8a is formed on the surface of the wafer 8, that is, within the opening of the plating resist layer 8b, as shown in FIG. be done. Note that the plating solution 3 sprayed onto the wafer 8
flows down from the upper end of cup 4 to the outside and returns to plating tank 2.
will be collected within.

[Problems to be Solved by the Invention] In the method for forming external electrodes as described above, since the plating resist (fi8b) formed in advance on the surface of the wafer 8 is as thin as a few meters, the external electrode 8a is formed on the outside of the plating resist layer 8b. (
It rises like a mushroom (upper side in Figure 9). especially,
The plating solution 3 has an appropriate flow rate, for example, about 1.0 liters per minute for a 6-inch wafer, or 10 liters per minute for the wafer.
If cc/c is less than 2, the external electrode 8a will expand and it will be difficult to achieve fine pitch.

For this reason, recently, a method of increasing the thickness of the plating resist layer 8b to form a straight outer circumferential surface of the external electrode 8a has been considered.
When plating is carried out, since the amount of Ft in the plating solution 3 is small, the concentration of the plating solution 3 (gold (Au) concentration) in the cup 4 becomes uneven, and the height distribution of the external electrode 8a formed on the wafer 8 becomes uneven. As shown in FIG. 10, the center of the wafer 8 is high and the periphery is low in the shape of a mountain, and the height difference of the external electrode 8a is 10#.
There is a problem in that the external electrode 8a completely loses its uniformity when the external electrode 8a reaches about Lm.

An object of the present invention is to provide a method for forming external electrodes on a wafer, in which there is little variation in the height difference of external electrodes between the center and the periphery of the wafer, and the external electrodes can be formed almost uniformly even on a large wafer.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention installs a wafer having a plating resist layer with a thickness of lOILm or more in which external electrode forming portions are opened in a plating apparatus, and The purpose is to form external electrodes by jetting a plating solution at a rate of 30 cc/c12 or more per minute.

[Function 1] According to the present invention, by forming a plating resist layer with a thickness of 10 gm or more in which an external electrode forming part is opened on the surface of the wafer, the external electrode formed in the external electrode forming part becomes a "mushroom". The wafer is then placed in a plating machine and the plating solution is jetted onto the wafer at a flow rate of 30cc/cm2 or more. By jetting the plating solution with a uniform concentration, it is possible to reduce the variation in height between the center and the periphery of the wafer, and to form external electrodes of almost uniform height. Since it does not form a shape, it is possible to achieve a finer pitch.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 7.

FIG. 1 shows a plating apparatus suitable for the external electrode forming method of the present invention.This plating apparatus 20 has an upper lid 23 attached to the top of a plating tank 22 that stores a plating solution 21 so as to be openable and closable, and a plating apparatus 20 in which a plating solution 21 is stored. Cup 2 from which liquid 21 flows
4 is provided, and this cup 24 and the plating tank 22 are connected to a liquid path 25.
A jet pump 26 is installed in this liquid path 25, and the jet pump 26 sends the plating liquid 21 from the plating tank 22 into the cup 24, and the plating liquid 21 is jetted as shown by the arrow. There is. In this case, a circular fitting part 24a formed on the lower surface of the cup 24 is attached by press-fitting to a ring-shaped mounting convex part 22a formed at the center of the bottom of the plating tank 22, and the upper part has a circular fitting part 24a formed on the bottom surface thereof. A head ring 27 is provided for holding the wafer 30, and a pair of opposing cathode pins 28.2B are attached to both sides of the head ring 27.
A seven-node electrode plate 29 is arranged on the bottom side. As shown in FIG. 2, the head ring 27 has a pair of plating liquid blocking walls 27a, 27a formed on the upper surface thereof to protrude upward, and a lower end thereof is fitted into a stepped portion 24a formed at the upper part of the cup 24 by press fitting or the like. It is worn. This plating solution blocking wall 27
a.

27a blocks the plating solution 21 from adhering to the cathode pins 28, 28, and corresponds to the cathode pin 28.2B and is positioned closer to the center of the cup 24 than the tip of the cathode pin 28. A wafer 30 is placed on the upper end. The cathode pin 28.28 has a "hook" shape with the tip facing upward, and normally the tip protrudes slightly above the plating solution blocking wall 27a; Note that the upper lid 23 is provided with cathode terminals 23a, 23a and an anode terminal 23b connected to a power supply device (not shown).

Among the cathode terminals 23b, cathode pins 28, 28 are directly connected to the cathode terminals 23a, and a 7-node electrode plate 29 is connected to the anode terminal 23b via a lead l129a.

Next, the wafer 30 is plated using the plating apparatus 20 as described above.
A case where an external electrode is formed at the same time will be explained. In this case, a wafer 30 is formed in advance as shown in FIGS. 4 and 5. That is, first, the silicon substrate 31
A silicon oxide layer 32 is formed on the upper surface, and a silicon nitride fi 33 is formed on the upper surface of this silicon oxide layer 32.

Pad portions 34 (only two are shown in FIG. 5) made of aluminum alloy are formed at predetermined locations on the silicon nitride layer 33 to be connected to internal electrodes (not shown) such as gates. A barrier metal layer 35 and a gold vapor deposition layer 36 are laminated on the entire surface of the silicon nitride layer 33 to cover the pad portions 34 . Thereafter, a plating resist layer 37 is formed with a thickness of 1101L or more on the gold vapor deposited layer 36 on the uppermost surface, and a mask is placed on this plating resist layer 37, and by exposing and developing, the plating resist layer 37 is
7, openings 037&-. are formed in correspondence with pads 1s34.... This brings the wafer 30 into a state in which external electrodes can be formed. Note that in this case, the wafer 30
A plating electrode, that is, a part of the gold vapor deposited layer 36 is exposed at the peripheral edge of the plating electrode.

Next, the wafer 30 formed in this way is placed in a plating machine W1.
Set within 20. In this case, first of all, plating!
Open the upper M23 of the i20, turn the wafer 30 upside down, and place it on the head ring 27 on the cup 24 in the plating tank 22. That is, the wafer 30 is placed on the plating liquid blocking walls 27a, 27a of the head ring 27 with the side of the plating resist layer 37 to be plated facing downward. Then, the tips of the cathode pins 28, 28 provided outside the plating solution blocking walls 27a', 27a come into contact with a plating electrode formed on the peripheral edge of the wafer 30, that is, a part of the gold vapor deposited layer 36. This makes it possible to perform plating processing for the external electrodes of the wafer 30.

After the wafer 30 is set in this way, the upper M
23 is closed and the jet pump 26 is activated. Then,
The plating solution 21 in the plating bath 22 is sent into the cup 24 through the channel 25, and is jetted as shown by the arrow in FIG. It flows radially from the center to the periphery while soaking the plating surface as shown in FIG. At this time, the plating liquid 21 is applied to the head ring 27.
The flow of the plating solution is blocked by the plating solution blocking walls 27a, 27a, avoiding the cathode pins 28, 28, and plating the wafer 30.
flows toward the periphery.

In this state, when a plating current is applied to the cathode pins 28, 28 and the 7-node electrode plate 29, plating (for example, gold (Au) plating) to form external electrodes. In this way, when the plating solution 21 is sprayed onto the plating surface of the wafer 30 at a flow rate of 30 cc/c+s2 or more per minute, the center and peripheral parts of the wafer 30 are plated, as shown in FIG. There is no variation in the height difference of the external electrode, and it is formed uniformly. This will be explained below.

That is, as shown in FIG. 7, the variation in height of the external electrodes formed on the wafer 30 rapidly decreases as the flow rate of the plating solution 21 increases, and when the flow rate reaches a certain amount S, , after which it hardly changes. This variation at the bending point (point of flow Is) is not a problem unless exceptionally high accuracy is required, therefore,
It can be seen that it is efficient to set the flow rate S to about this bending point. Of course, I L B (Inner Lead
The flow rate may be set to S or less as long as a flow rate smaller than the bending point can satisfy the variation during bonding.

As a result of considering these matters, we found that when the thickness of the plating resist layer 37 of the wafer 30 is 10 μm or more, the flow rate is 30 cc/c or more per minute (for example, 5.5 cc/min for a 6-inch wafer). 1 liter per minute for 8-inch wafers, and 2 liters per minute for 4-inch wafers).

The variation of the external electrodes was found to be satisfactory. By the way, the thickness of the plating resist layer 37 is 30μ.
m, the flow rate of the plating solution 21 with respect to the bending point (point of flow 1 s) is 9 to 13 per minute for a 6-inch wafer.
Using plating equipment with a flow rate of 50 to 7
It was 0cc/cm2. For this reason, the capacity of the jet pump 26 can be increased, the flow rate of the plating solution 21 can be increased, and the concentration of the plating solution (for example, gold (Au) concentration) can be made uniform. As described above, the external electrodes can be formed uniformly with almost no difference in height between the central part and the peripheral part of the wafer 30.

[Effects of the Invention] As described above in detail, according to the present invention, by forming a plating resist layer with a thickness of 1 Gμm or more in which the external electrode forming portion is opened on the surface of the wafer, the external electrode forming portion can be formed. The formed external electrode does not have a "mushroom" shape, and its outer peripheral surface can be formed into a straight shape.
By mounting the wafer in a plating device and jetting the plating solution onto the wafer at a flow rate of 30 cc/cm2 or more per minute, the plating solution can be jetted with a uniform concentration, and the plating solution can be jetted at a uniform concentration between the center and the periphery of the wafer. There is little variation in height difference,
The external electrodes can be formed with a nearly uniform height, and since the external electrodes do not have a "mushroom" shape, it is possible to achieve fine pitch.

[Brief explanation of the drawing]

1 to 7 show one embodiment of the present invention, FIG. 1 is a sectional view of a plating apparatus suitable for the method of the present invention, and FIG. 2 is a perspective view showing a head ring thereof. FIG. 3 is a diagram showing the flow state of the plating solution in the head ring portion, FIG. 4 is an external side view of the wafer, FIG. 5 is an enlarged cross-sectional view of the main part, and FIG. 7 is a diagram showing the relationship between the variation in the height difference of the external electrodes and the flow rate of the plating solution. FIGS. 8 to 10 show conventional examples. The figure is a cross-sectional view showing a conventional plating apparatus, and FIG. 9 is an enlarged cross-sectional view of the main part of a wafer showing external electrodes formed by the conventional method.
FIG. 10 is a diagram showing the height difference of the external electrodes. 20...Plating device, 21...Plating solution, 30...Wafer, 37...Plating resist layer, 37a...Opening. Patent applicant: Casio Computer Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 wA Yang Center
IN insurance @ II meeting 4til Fig. 6 Fig. 7 ffl + luster position Fig. 1O

Claims (1)

[Claims] A wafer having a plating resist layer with a thickness of 10 μm or more with an opening for the external electrode forming part is mounted on a plating device, and a plating solution is jetted onto the wafer at a rate of 30 cc/cm^2 or more per minute to form an external electrode. A method for forming external electrodes on a wafer, characterized by: