JPH0712036B2 - Wafer etching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention manufactures, for example, a diaphragm of a pressure sensor by etching a surface of a semiconductor wafer with a chemical to selectively form a desired recess. The present invention relates to a wafer etching device.

[Prior art]

Conventionally, for example, in order to manufacture a pressure sensor, when a recess 1a is formed on the surface of a wafer 1 made of a semiconductor as shown in FIG. 5 by etching, as shown in FIG. 6 and FIG. After the mask 2 having a predetermined pattern for exposing the recess forming portion is deposited on the etching surface 1b and the resist film 3 is deposited on the circuit surface 1c on the back surface, the etching liquid 5 filled in the etching liquid tank 4 is placed. Etching surface of wafer 1 exposed from mask 2 by immersion
1b is selectively etched from the etching liquid 5 to form the concave portion 1a, and the pressure sensor having the diaphragm having the predetermined pattern is manufactured. At this time, as shown in FIG. 7, a large amount of reaction gas 6 generated during etching.
The wafer 1 is immersed in the etching liquid 5 with the etching surface 1b facing upward so that the water does not collect in the recess 1a.
It is necessary to perform operations such as swinging the wafer 1 up and down in the etching liquid 5. However, as the etching progresses, the concave portion 1a expands, and a pocket is formed on the back side of the mask 2.
1d (Fig. 6b) occurs, the escape of the reaction gas 6 becomes worse,
Etching does not proceed uniformly. Therefore, in the above method, the larger the etching amount, the greater the variation in the shape of the recess 1a and the longer etching time. Therefore, a product that can be used practically when the etching depth (that is, the depth of the recess 1a) is 300 μm or more is produced. There was a problem that I could not do it.

Therefore, in order to solve the problem of the above immersion method,
A jet type device shown in the figure has been proposed. In this apparatus, the circuit surface 1c of the wafer 1 is held by a vacuum chuck 7, and the motor 8 rotates the vacuum chuck 7 so that the wafer 1 is rotated on the etching liquid tank 4 with the etching surface 1b facing downward. On the other hand, the etching liquid 5 pumped by the circulation pump 10 is provided in the etching liquid tank 4 so that the nozzle 9 which is close to and faces the wafer 1 is projected from the bottom surface thereof.
Is sprayed from the nozzle 9 onto the etched surface 1b of the wafer 1. At this time, the upper surface of the nozzle 9 in which the nozzle hole 9a is opened has a diameter slightly larger than that of 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 size. The etching liquid 5 ejected from the nozzle holes 9a radially circulates in the gap 11 between the wafer 1 and the nozzle 9 as shown in FIG.

In this apparatus, the reaction gas 6 generated at the time of etching is removed by the etching liquid 5 to quickly replace the etching liquid 5 in the recess 1a of the etching target surface 1b.
By reducing the variation of the gap 11 caused by the warp of the wafer 1 and the problem of mechanical working accuracy by rotating the wafer 1, it is possible to shorten the etching time and improve the accuracy when the etching depth is large. It is connected.

[Problems to be Solved by the Invention]

In the above-mentioned conventional example, when the gap 11 is set to about 3 mm, the etching time becomes 1/2 as compared with the immersion method of FIG. 7, and the variation is practical if the etching depth is about 100 to 200 μm. It becomes a range. However, when the etching depth is 300 μm or more, as shown in FIG.
In the concave portion 1a on the edge of the wafer 1 as compared with the concave portion 1a immediately before the nozzle hole 9a, a strong place where the etching liquid 5 hits is largely etched under the influence of the flow of the etching liquid 5 as shown by A. The shape of the concave portion 1a is deformed, or the reaction gas 6 does not escape as shown by B and the reaction gas stops in the concave portion 1a and the reaction often stops, resulting in a large variation in the etching depth. It was difficult to manufacture the product.

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

[Means for Solving the Problems]

The present invention relates to a means for holding a wafer, a nozzle arranged so that the nozzle surface faces the wafer, a pump for ejecting an etching liquid from the nozzle toward the wafer, and either the wafer or the nozzle. And a means for rotating one of the nozzles, wherein the nozzle forms a part of the nozzle surface, and a floating nozzle having a nozzle hole penetratingly formed is movably provided in a direction 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.

[Action]

In the above configuration, in the present invention, when the etching liquid is pressure-fed to the nozzle by the pump that discharges the etching liquid in a pulsed manner, the floating nozzle is pushed by the hydraulic pressure and protrudes from the nozzle surface to approach the wafer, When the etching liquid is sprayed from the multiple nozzle holes of the floating nozzle toward the wafer to replace the etching liquid in the concave portion of the wafer facing the nozzle holes and when the pumping of the etching liquid is interrupted, the floating The nozzle sinks due to its own weight, becomes apart from the wafer and becomes a part of the nozzle surface, and the etching liquid is held in the gap between the nozzle surface and the wafer by utilizing surface tension, and etching progresses. These operations are performed while rotating the nozzle and the wafer relative to each other and changing the portion where the jet of the etching liquid hits the wafer.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and those having the same functions as those in FIG. 8 are designated by the same reference numerals. In FIG. 1, the wafer 1 has a mask 2 on the etched surface 1b as in FIG.
And the center of the circuit surface 1c on the back side is held by a vacuum chuck 7 suspended from above the case 12. The vacuum chuck 7 is connected to a motor 8 arranged on the upper surface of the case 12, and the wafer 1 is rotated by the motor 8 with the etched surface 1b facing downward. An etching liquid tank 4 is arranged above the case 12. The bottom of the etching liquid tank 4 has a cylindrical nozzle base with a diameter larger than that of the wafer 1.
A nozzle 13 is formed integrally with the center of rotation of the wafer 1 so as to be coaxial with the nozzle base 13 so that the upper surface of the nozzle base 13 faces the etched surface 1b of the wafer 1 held by the vacuum chuck 7 with a predetermined gap. The height of the base 13 and the positioning of the etching liquid tank 4 are determined. An oblong groove 14 having a major axis slightly longer than the diameter of the wafer 1 is bored on the upper surface of the nozzle base 13 so as to cross the center of the upper surface, and an oval floating nozzle 15 is formed in the groove 14. It is fitted loosely. In addition, the inside of the nozzle base 13 has an oval opening slightly smaller than the floating nozzle 15 except for a bottom wall portion 14a having a slight width at the periphery of the bottom surface of the groove 14, and the etching liquid tank 4
A pressure chamber 17 is formed so as to be continuous with the inlet 16 formed at the center of the bottom surface of the sloped surface. The floating nozzle 15
When it is mounted on the nozzle base 13, it constitutes a part of the nozzle surface, and as shown in FIG. 2, a plurality of nozzle holes 18 are formed in a row on the major axis thereof. The plurality of nozzle holes 18 is the wafer 1
All the nozzle holes 18 are eccentrically arranged so as to be located at different radial positions with respect to the rotation center O of. Each nozzle hole 18 has a shape in which holes having different diameters are coaxially connected, and the diameter on the upper surface side facing the wafer 1 is small and the diameter on the lower surface side is large. And at the bottom of the case 12, the pump 19
Is arranged, and the suction side is connected to the etching liquid tank 4 and the discharge side is connected to the inlet 16 of the nozzle base 13 by piping. The 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 structure, the etching liquid 5 is pumped out of the etching liquid tank 4 by the pump 19, supplied to the etching target surface 1b of the wafer 1 through the nozzle base 13 and the floating nozzle 15, and then recovered in the etching liquid tank 4. Be circulated. When the pump 19 having a pulse-like discharge characteristic is discharged, the etching liquid 5 is pumped from the pump 19 to the nozzle base 13 to increase the liquid pressure in the pressure chamber 17, and this liquid pressure acts on the lower surface of the floating nozzle 15. Instantly, the floating nozzle 15 moves upward to approach the wafer 1 as shown in FIG. 4, and the etching liquid 5 is sprayed from the nozzle holes 18 to the etching surface 1b of the wafer 1.
At this time, since the etching liquid 5 is interposed 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. . When the pump 19 is sucking, the 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 discharged on the discharge side of the pump 19. To stop, the floating nozzle 15 sinks into the groove 14 filled with the etching liquid 5 by its own weight as shown by the one-dot chain line in FIG. 4, and the upper surface of the floating nozzle 15 becomes almost equal to the upper surface of the nozzle base 13. , Etching liquid 5
Is held in a preset gap between the wafer 1 and the nozzle surface (reference numeral 21 in FIG. 4) by its own surface tension. In this way, when discharging the pump 19, the floating nozzle
Recesses 1a in which 15 approaches the wafer 1 and the nozzle holes 18 face each other
The etching liquid 5 is injected into the inside, and the reaction gas 6 accumulated in the recess 1a is pushed out by the progress of the etching, and the pump is also used.
At the time of suction of 19, the floating nozzle 15 sinks to form a nozzle surface together with the nozzle base 13, and the etching liquid 5 is held and etching progresses. Further, since the suction and discharge of the pump as described above are repeated while the wafer 1 is rotated by the motor 8, each nozzle hole 18
The concave portion 1a of the wafer 1 which receives the liquid flow from is sequentially moved.
Since the nozzle holes 18 arranged in a line are positioned eccentrically with respect to the center of rotation of the wafer 1, while the arbitrary recessed portion 1a passes near the specific nozzle hole 18 twice during one rotation of the wafer 1. Since the direction of the liquid flow received by the concave portion 1a is reversed, the liquid flow can be spread inside each concave portion 1a of the wafer 1. Therefore, the arbitrary recess 1a in which the etching liquid 5 has been once replaced by the liquid flow advances the etching reaction without being affected by the strong liquid flow until it next faces the nozzle hole 18, and As described above, since each concave portion 1a does not receive a biased liquid flow, uniform etching is performed in all directions, and the concave portion 1a having a good shape is formed. The influence of the liquid flow of the etching liquid 5 ejected from the nozzle hole 18 on the wafer 1 is 0.5
The reaction rate is, for example, 0.2 μs / second
m, which is not a problem because the injection time for one injection is sufficiently small with respect to the reaction speed. Further, since the floating nozzle 15 approaches the wafer 1 and jets the etching liquid 5, the wafer 1 may be warped or mechanically distorted.
Even if the gap between the nozzle surface and the nozzle surface is not uniform, the etching liquid 5 can be sprayed uniformly over the entire surface of the wafer 1, and uniform etching is possible.

Next, the result of producing the diaphragm for the pressure sensor using this embodiment as described above will be described. The etching surface 1b of the wafer 1 is covered with a mask 2 made of Cr.
Etching aperture diameters of φ1.5 mm, φ1.7 mm and φ1.9 mm were formed. The wafer 1 is arranged so that the circuit surface 1c is held by the vacuum chuck 7 as described above and the gap between the etched surface 1b and the nozzle surface of the nozzle base 13 is 0.5 mm to 0.8 mm. The rotation speed of the motor 8 was 50 to 100 rpm, and the wafer 1 was rotated at the same rotation speed. As the pump 10, a diaphragm pump that discharges 150 cc at 120 pulses per minute was used, and as the etching liquid 5, a mixed acid mainly containing hydrofluoric acid was used.

As a result of etching at 400 μm under the above conditions, etching was completed in 16 minutes. This is an etching rate of 25
μm / min, which is about 2.5 times that of the conventional immersion method and 1.25 times that of the jet method, thus improving the processing speed. Regarding the quality, the conventional method had a depth variation of about 80 μm (20%) or more due to etching of 400 μm.
It was significantly reduced to 20 μm (5%) or less, and it is clear that the etching progressed uniformly, and the quality was improved four times or more. Moreover, as a result of injecting the etching liquid 5 in a pulsed manner with the diaphragm pump, the etching liquid 5 is 1/10 of the conventional one.
It was a very small amount of about 0. Furthermore, the nozzle surface and the wafer 1
Since the high quality etching as described above can be performed despite the relative variation of 0.5 to 0.8 mm with respect to the wafer 1, it is not affected by the warp or mechanical strain of the wafer 1. .

From these results, not only the processing speed and quality have been improved, but also the circulation pump has been greatly downsized due to the adoption of the diaphragm pump, and the circulation amount of the etching liquid has been greatly reduced to the periphery of the nozzle. Since it is possible to greatly reduce the size of the device, it is possible to reduce the size and cost of the device, and further improve the maintainability and safety.

〔effect〕

As described 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, etching can be performed with high accuracy and in a short time, and the etching can be performed with the nozzle surface. Highly accurate gap between wafer and
It is not necessary to maintain it, the amount of etching liquid used is extremely small, and it is possible to reduce the size and cost of the device by downsizing the nozzle and the pump. It is also possible to improve the maintainability and safety. Produce the effect of.

[Brief description of drawings]

1 to 4 are views showing an embodiment of the present invention. FIG. 1 is a sectional view thereof, FIG. 2 is a plan view of a nozzle thereof, and FIG.
FIG. 4 is a diagram showing the discharge characteristics of the pump, FIG. 4 is an enlarged view of the main part of FIG. 1, FIGS. 5 to 10 are diagrams showing a conventional wafer etching apparatus, and FIGS. FIG. 7 is a plan view and a cross-sectional view of a wafer, FIG. 7 is a cross-sectional view of a conventional immersion type device, FIG. 8 is a cross-sectional view of a conventional jet type device, and FIG. 9 is a plan view of the nozzle of FIG. , FIG. 10 is an enlarged view of an essential part of FIG. 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. A means for holding a wafer, a nozzle arranged so that the nozzle surface faces the wafer, a pump for ejecting an etching liquid from the nozzle toward the wafer, and the wafer or the nozzle. And a means for rotating one of the nozzles, the nozzle forming a part of the nozzle surface, and a floating nozzle having a nozzle hole penetratingly formed on the nozzle base in a direction toward or away from the wafer. A wafer etching apparatus characterized in that it is provided so as to be movable relative to it. 2. The wafer etching apparatus according to claim 1, wherein the floating nozzle has a plurality of nozzle holes. 3. A nozzle hole of the floating nozzle is eccentrically arranged with respect to a rotation center of the wafer or the nozzle, according to claim 1 or 2.
The wafer etching apparatus as described in the paragraph. 4. The wafer etching apparatus according to claim 1, 2, or 3, wherein the pump has a pulsed discharge characteristic.