JPH03201432A - Wafer etching device - Google Patents

Abstract

PURPOSE:To manufacture the title wafer etching device capable of etching wafer with high precision within a short time regardless of the etching depth by a method wherein a floating nozzle eccentrically arranged to the turning center of wafer or nozzles free-shiftingly provided in the approaching or separating directions to or from the wafers while a pump is provided with a discharging characteristics setting pulses. CONSTITUTION:A floating nozzle 15 sinks into a groove 14 filled up with an etchant 5 by the deadweight thereof; the surface of the floating nozzle 15 is made flush with the surface of a nozzle base 13; while the etchant 5 is held in the gap previously made between wafer 1 and the surfaces of nozzles by the surface tention of the etchant 5 itself. At this time, since the nozzles 18 arrayed in line are eccentrically arranged to the turning center of the wafer, the direction of the running solution along an arbitrary recession 1a is reversed while the recession 1a passes by the near part of a specific nozzle 18 two times during one turn of the wafer 1 thereby enabling the running solution to extend to the insides of respective recessions 1a of the wafer 1. Furthermore, the etchant 5 can be jetted setting the pulses by a diaphragm pump thereby enabling the consumption of the etchant 5 to be cut down.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to manufacturing, for example, a diaphragm of a pressure sensor, etc. by etching the surface of a semiconductor wafer with chemicals to selectively form desired recesses. This invention relates to wafer etching equipment.

[Prior art]

Conventionally, when forming a recess 1a on the surface of a semiconductor wafer 1 as shown in FIG. 5 in order to manufacture a pressure sensor, for example, the surface of the wafer 1 is etched as shown in FIGS. 6 and 7. After covering the etching surface 1b with a mask 2 having a predetermined pattern that exposes the concave portion forming part and also depositing a resist film 3 on the circuit surface IC on the back surface, the etching solution 5 filled in the etching solution tank 4 is poured. By dipping, the etching surface 1b of the wafer 1 exposed through the mask 2 is selectively etched by the etching solution 5, forming a recess 1a, and a pressure sensor equipped with a diaphragm having the predetermined pattern is manufactured. Ru. At this time,
As shown in FIG. 7, the wafer 1 is immersed in the etching solution 5 with the surface 1b to be etched facing upward so that a large amount of reaction gas 6 generated during etching does not accumulate in the recess 1a. It is necessary to perform an operation such as shaking the holder 1 up and down in the etching solution 5. however,
As the etching progresses, the recess 1a expands and the mask 2
A pocket ld (Fig. 6b) is formed on the back side of the reactant gas 6.
Etching becomes difficult and the etching does not proceed uniformly. For this reason, in the above method, the larger the etching amount, the greater the variation in the shape of the recess 1a, and the longer the etching time, so if the etching depth (i.e., the depth of the four parts 1a) is 300 μm or more, a product that can be used for practical purposes cannot be produced. The problem was that I couldn't do it.

Therefore, conventionally, in order to solve the problem of the above-mentioned immersion method,
A jet flow type device shown in the figure has been proposed. This device holds a circuit surface IC of a wafer 1 with a vacuum chuck 7, rotates the vacuum chuck 7 with a motor 8, and rotates the wafer 1 on an etching liquid tank 4 with the surface to be etched 1b facing downward. , Meanwhile, the wafer l is placed in the etching liquid bath 4.
Nozzles 9 are disposed protruding from the bottom surface of the wafer 1, and the etching liquid 5 pumped by the circulation pump 10 is injected from the nozzles 9 onto the surface 1b of the wafer 1 to be etched. At this time, the upper surface of the nozzle 9 where the nozzle hole 9a opens has a slightly larger diameter than the wafer 1, and the gap 11 between the etched surface 1b of the wafer 1 and the upper surface of the nozzle 9 is set to a predetermined dimension. The etching liquid 5 injected from the nozzle hole 9a fills the gap 11 between the wafer 1 and the nozzle 9.
flows radially and circulates as shown in FIG.

In this device, the reaction gas 6 generated during etching is flushed away with the etching liquid 5, and the recess 1 of the surface 1b to be etched is etched.
The etching time can be shortened by quickly replacing the etching liquid 5 in a, and by rotating the wafer 1 to alleviate variations in the gap 11 caused by warpage of the wafer 1 or problems with mechanical machining accuracy. The aim is to improve accuracy when shortening and etching depth is large.

[Problems to be Solved by the Invention] In the conventional example, when the gap 11 is set to about 3nuy, the etching time is reduced to about 1/1 compared to the dipping method shown in FIG.
2, and if the etching depth is about 100 to 200 μm, the variation will be within a practical range. However, when the etching depth becomes 300 μm or more, as shown in FIG. Under the influence of the flow of 5, the places where the etching liquid 5 is strongly hit are greatly etched and the shape of the recess 1a is deformed, or the reaction gas 6 does not escape and accumulates in the recess 1a as shown by B, causing the reaction to fail. The etching process frequently stopped and the etching depth varied greatly, making it difficult to manufacture practical products.

Therefore, the present invention aims to provide a wafer etching apparatus that can perform etching with high precision and in a short time regardless of the etching depth.

[Means to solve the problem]

The present invention provides means for holding a wafer, a nozzle disposed with a nozzle surface facing the wafer, a pump for injecting etching liquid from the nozzle toward the wafer, and either the wafer or the nozzle. the nozzle is provided with a floating nozzle forming a part of the nozzle surface and having a nozzle hole formed therethrough so as to be movable toward or away from the wafer. , the floating nozzle has a plurality of nozzle holes, the nozzle holes are arranged eccentrically with respect to the rotation center of the wafer or the nozzle, and the pump has a pulsed discharge characteristic.

[Operation] In the above configuration, in the present invention, when the etching liquid is pumped to the nozzle by the pump that discharges the etching liquid in pulses, the floating nozzle is pushed by the liquid pressure and protrudes from the nozzle surface to approach the wafer. At the same time, the etching liquid is sprayed toward the wafer from the plurality of nozzle holes of the floating nozzle, and the etching liquid in the recess of the wafer facing the nozzle hole is replaced, and when the pressure feeding of the etching liquid from the pump is interrupted, The floating nozzle sinks under its own weight, separates from the wafer, and becomes part of the nozzle surface, and the etching liquid is retained in the gap between the nozzle surface and the wafer using surface tension, and etching progresses. These operations are performed by rotating the nozzle and the wafer relative to each other to change the portion of the etching liquid that hits the wafer.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and parts with the same functions as those in FIG. 8 are given the same reference numerals.

In FIG. 1, the wafer 1 has a mask 2 attached to the surface to be etched 1b as in FIG. . The vacuum chuck 7 is connected to a motor 8 disposed on the upper surface of the case 12, and the wafer 1 is rotated by the motor 8 with the surface lb to be etched facing downward. An etching liquid tank 4 is disposed above the case 12. A cylindrical nozzle base 13 having a diameter larger than the wafer 1 is integrally formed coaxially with the rotation center of the wafer 1 on the bottom surface of the etching liquid tank 4.
The height of the nozzle base 13 and the position of the etching liquid tank 4 are determined such that the upper surface of the etching liquid tank 3 faces the etched surface 1b of the wafer l held by the vacuum chuck 7 at a predetermined distance. On the upper surface of the nozzle base 13, there is an oval groove 14 having a major axis slightly longer than the diameter of the wafer 1.
is bored across the center of the upper surface, and this groove 14
An oblong floating nozzle (■5) is loosely fitted in the. Furthermore, inside the nozzle base 13, there is an oval opening that is slightly smaller than the floating nozzle 15, leaving a slightly wider bottom wall portion 14a at the periphery of the bottom surface of the groove 14, and is bored in the center of the bottom surface of the etching liquid tank 4. A pressure chamber 17 is formed by the inlet port 16 and the slope. The floating nozzle 15 constitutes a part of the nozzle surface when mounted on the nozzle base 13, and as shown in FIG. 2, a plurality of nozzle holes 18 are bored in a line along its long axis. The plurality of nozzle holes 18 are arranged eccentrically with respect to the rotation center O of the wafer 1 so that all the nozzle holes 18 are located at different radial positions. Each nozzle hole 18 has a shape in which holes with different diameters are coaxially arranged, with a smaller diameter on the upper surface side facing the wafer 1 and a larger diameter on the lower surface side. A pump 19 is disposed at the bottom of the case 12, and its suction side is connected to the etching liquid tank 4, and its discharge side is connected to the inlet 16 of the nozzle base 13 by piping. pump 19
has a pulse-like discharge characteristic as shown in FIG. 3, and for example, a solenoid-driven diaphragm pump is used.

In the above configuration, the etching liquid 5 is pumped out from the etching liquid tank 4 by the pump 19, and the etching liquid 5 is pumped out from the etching liquid tank 4 by the pump 19.
After being supplied to the surface to be etched 1b of the wafer 1 via the floating nozzle 15, it is collected in the etching liquid tank 4 and circulated.

At the time of discharge from the pump 19 having pulsed discharge characteristics,
The etching liquid 5 is pumped to the nozzle base 13 by the pump 19, increasing the hydraulic pressure in the pressure chamber 17. This hydraulic pressure acts on the lower surface of the floating nozzle 15, and the floating nozzle 15 instantly moves upward to form the fourth As shown in the figure, as the wafer 1 is approached, the etching liquid 5 is sprayed from each nozzle hole 18 onto the surface 1b of the wafer 1 to be etched.

At this time, since the etching liquid 5 is present between the wafer 1 and the floating nozzle 15 (reference numeral 20 in FIG. 4), the floating nozzle 15 does not collide with the wafer 1 and damage the wafer 1. Furthermore, when the pump 19 is suctioning, the pressure feeding of the etching liquid 5 to the nozzle base 13 is interrupted, and the etching liquid 5 is sucked into the pump 19 from the etching liquid tank 4. At this time, the flow of the etching liquid 5 is stopped on the discharge side of the pump 19. To stop the etching, the floating nozzle 15 sinks under its own weight into the groove 14 filled with the etching liquid 5, as shown by the dashed line in FIG. The liquid 5 has a preset gap between the wafer 1 and the nozzle surface due to its own surface tension (Fig.
1). In this way, when the pump 19 discharges, the floating nozzle 15 approaches the wafer 1, and the etching liquid 5 is injected into the recess 1a where each nozzle hole 18 faces, and as the etching progresses, the reaction gas 6 accumulated in the recess 1a is removed. When the pump 19 is suctioned, the floating nozzle I5 sinks to form a nozzle surface together with the nozzle base 13, retaining the etching liquid 5 and proceeding with etching.

Furthermore, since the above-described pump suction and discharge are repeated while the wafer 1 is being rotated by the motor 8, the recesses 1a of the wafer 1 that receive the liquid flow from each nozzle hole 18 move sequentially. - Since the nozzle holes 18 arranged in a row are located eccentrically with respect to the rotation center of the wafer 1, any concave portion 1a passes near a specific nozzle hole 18 twice during one rotation of the wafer 1. In between, the direction of the liquid flow received by the recesses 1a is reversed, so that the liquid flow can be spread inside each recess 1a of the wafer l. Therefore, the etching reaction proceeds in any concave portion 1a in which the etching liquid 5 has been replaced by the liquid flow without being affected by the strong liquid flow until it next faces the nozzle hole 18. Since the concave portion 1a is not subjected to uneven liquid flow, uniform etching is performed in all directions, and the concave portion 1a is formed in a good shape. In addition,
The effect of the flow of etching liquid 5 injected from the nozzle hole 18 on the wafer 1 is that one injection is instantaneous, for example, 0.5 seconds, whereas the reaction speed is, for example, 0.2 μm per second. This does not pose a problem because the injection time is sufficiently small compared to the reaction speed.

In addition, since the floating nozzle 15 approaches the wafer 1 and sprays the etching liquid 5, even if the gap between the wafer 1 and the nozzle surface is not uniform due to warpage of the wafer 1 or mechanical strain, the wafer 1 The etching liquid 5 can be sprayed uniformly over the entire surface of the etching surface, and uniform etching is possible.

Next, the results of manufacturing a diaphragm for a pressure sensor using this example as described above will be described.

The etched surface 1b of the wafer l is covered with a mask 2 made of Cr.
The etching opening diameter of mask 2 is φ1.5 mm.
, φ1.71TIJ11 and φ1.9mm. The circuit surface 1c of the wafer 1 was held by the vacuum chuck 7 as described above, and the wafer 1 was arranged so that the gap between the surface to be etched 1b and the nozzle surface of the nozzle base 13 was 0.5 mm to 0.8 mm. Also, the rotation speed of the motor 8 is 50 to ioo
rpm, and the wafer 1 was rotated at the same rotation speed. The pump 10 was a diaphragm pump that discharged 150 cc at 120 pulses per minute, and the etching liquid 5 was a mixed acid mainly consisting of boiling acid.

As a result of etching of 400 μm under the above conditions, the etching was completed in 16 minutes. This is an etching rate of 25 μm/min, which is approximately 2.5 times that of the conventional immersion method.
Furthermore, the processing speed is 1.25 times that of the jet method, and the processing speed is improved. Regarding quality, with the conventional method, the depth variation is about 80 μm (20 μm) due to 400 μm etching.
%) was significantly reduced to 20 μm, (5%) or less, and it is clear that etching progressed uniformly, and the quality was improved by more than 4 times. Furthermore, as a result of injecting the etching liquid 5 in a pulsed manner using a diaphragm pump, the amount of etching liquid 5 was reduced to about 1/100 of the conventional amount. Furthermore, the gap between the nozzle surface and the wafer l is 0.5
Although there was a relatively large variation of ~0.8nvn, high-quality etching as described above is possible.
It is not affected by warpage of the wafer l or mechanical strain.

These results not only improved processing speed and quality, but also enabled the use of a diaphragm pump to significantly downsize the circulation pump, as well as greatly reduce the amount of etching solution circulated through the nozzle. Since it is possible to significantly reduce the size of the surrounding area, it has become possible to reduce the size and cost of the device, and it has also become possible to improve maintainability and safety.

[Effects] As explained above, according to the present invention, even if the etching depth is relatively deep, there is no variation over the entire surface of the wafer, and etching can be performed with high precision and in a short time. The gap between the nozzle surface and the wafer is set with high precision.
There is no need to maintain it, and the amount of etching liquid used is extremely small, making it possible to downsize the nozzle area and pump, thereby reducing the size and cost of the device, and improving maintainability and safety. It has the effect of

[Brief explanation of drawings]

1 to 4 are views showing one embodiment of the present invention, in which FIG. 1 is a sectional view thereof, FIG. 2 is a plan view of the nozzle, and FIG.
The figure shows the discharge characteristics of the pump, Figure 4 is an enlarged view of the main part of Figure 1, Figures 5 to 10 are diagrams showing conventional wafer etching equipment, and Figures 5 and 6 are 7 is a sectional view of a conventional immersion type device, FIG. 8 is a sectional view of a conventional jet type device, and FIG. 9 is a plan view of the nozzle in FIG. 8. Figure 10 is the 8th
It is an enlarged view of the main part of the figure. 1...Wafer, 2...Mask, 4...Etching liquid tank, 5...
...Etching liquid, 7...Vacuum chuck,
8...Motor, 13...Nozzle base, 15...Floating nozzle, 18...
...Nozzle hole.

Claims (4)

[Claims] (1) means for holding a wafer; a nozzle disposed with a nozzle surface facing the wafer; and a pump for injecting an etching solution from the nozzle toward the wafer;
means for rotating either the wafer or the nozzle, the nozzle forming a part of the nozzle surface, and a floating nozzle having a nozzle hole formed therethrough;
A wafer etching apparatus characterized in that it is provided movably relative to a nozzle base in a direction toward or away from the wafer. (2) The wafer etching apparatus according to claim 1, wherein the floating nozzle has a plurality of nozzle holes. (3) The wafer etching apparatus according to claim 1 or 2, wherein the nozzle hole of the floating nozzle is arranged eccentrically with respect to the rotation center of the wafer or the nozzle. (4) The wafer etching apparatus according to claim 1, 2, or 3, wherein the pump has a pulsed discharge characteristic.