JPS6386525A - Device for etching semiconductor silicon wafer - Google Patents

Abstract

PURPOSE:To prevent the generation of clouding, irregularity of etching and irregularity of flatness by a method wherein microscopic bubbles are generated in a mixed acid solution, and the mixed acid solution is stirred up. CONSTITUTION:Mixed acid solution, which is an etchant, is filled up a reaction bath 1, the flow rate of air is set at 2.0 kg/cm<2> (50l/min.) or thereabout, and microscopic bubbles 8 are generated by an air nozzle 3. Also, a silicon wafer A is supported by a wafer supporting tool 7, they are dipped into a mixed acid solution, a reciprocatory movement is performed in the reaction bath 1 while the wafer A is being rotated. The average value of occupation rate of 0.18 mu which is very approximate to zero is obtained, and the standard deviation can be made small to 0.46. Also, when treated silicon wafer is visually inspected, a cloud and a non-uniformity of etching are not observed at all.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an etching apparatus for surface-treating a semiconductor silicon wafer after lap cleaning.

(Prior art) In the production of conductive silicon wafers, a silicon single crystal ingot is cut with a diamond saw, wrapped and washed, and then etched to make the surface clean and uniform in shape. The material is then sent to the next process to be coated with an oxide film, nitride film, coating, etc.

By the way, the above-mentioned etching has conventionally been carried out by holding the silicon wafer as a carrier and immersing it in the mixed acid solution, and by rotating the silicon wafer and moving it linearly back and forth through the mixed acid solution.

(Problem to be solved by the invention) However, according to the above conventional method, there is a difference in reaction between the center position and the outer peripheral position of the silicon wafer, resulting in cloudiness and uneven etching on the surface of the silicon wafer after processing. In addition, flatness accuracy deteriorated, contributing to a decrease in manufacturing yield.

In other words, in the conventional method, the contact between the silicon wafer and the mixed acid solution is dependent only on the relative movement of the two (linear reciprocating motion and rotational motion). Phenomenon in which it is difficult to reach the center ■■ Regarding rotational movement, there is a fact that the circumferential speed of the outer periphery of the silicon wafer is higher than that of the inner periphery. It is thought that a difference in response occurs between the position and the outer circumferential position.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a silicon wafer etching apparatus in which a silicon wafer is immersed in a mixed acid solution and the silicon wafer is rotated or linearly moved. It is an object of the present invention to provide an etching device that releases fine air bubbles into a mixed acid solution and stirs the mixed acid solution.

(Function) According to the means described, the mixed acid solution is stirred by minute bubbles, and the resulting stirred flow collides with the silicon wafer, regardless of whether it is in the center or the outer periphery, causing a reaction or a uniform reaction throughout the silicon wafer. As a result, cloudiness, uneven etching, and uneven flatness that conventionally occur due to reaction differences are eliminated.

(Example) The present invention will be explained below based on one embodiment.

FIG. 1 shows an apparatus for carrying out the present invention, in which 1 is a reaction bath filled with a mixed acid solution 2, 3 is an air nozzle disposed on the bottom of the reaction bath 1, and 4 is an air nozzle 3.
The piping for feeding air from the Hetsurowa 5 is shown. Reference numeral 6 denotes a holder equipped with a rotationally driveable wafer holder 7, and the holder 6 is configured to be movable in the longitudinal direction of the reaction bath 1.

The inventor used the above-mentioned apparatus to fill the above-mentioned reaction bath 1, which is a mixed acid as an etching liquid, and adjusted the air flow rate to 2.0 Kg/
crn' (50 sentences/m1n) to generate fine air bubbles 8 from the air nozzle 3 as shown by the arrow in FIG. The wafer A was immersed in the liquid 2, and while rotating, the wafer A was reciprocated in the reaction bath 1.

The reason why the air flow rate was set to 2.0 Kg/cm' is based on the graph in Figure 3 (a graph showing the correlation between the air flow rate and the variation in flatness accuracy).
Even if it exceeds crrf, no significant effect can be obtained in each case, and 1
．． This is because if it is less than 8 Kg/crn', the effect will be reduced.

The results of the above implementation are shown in a graph as FIG. In the figure, the horizontal axis indicates accuracy (reference value is set to 0), and the vertical axis indicates the occupancy rate (distribution) of silicon wafers having the above-mentioned accuracy.

That is, in the case of the present invention (results are indicated by broken lines), an average value of 0.18 g was obtained, which was extremely close to 0, and the standard deviation was also small, 0.46.

In addition, the results of the conventional method shown by the solid line have an average value of 0.51g.
The standard deviation is 0.64, and the effect of the present invention is clear.

Further, when the silicon wafer was visually inspected after the above-described process, no clouding or uneven etching was observed at all.

(Effect of the invention) As explained above, the present invention can be easily implemented by simply attaching a bubble generator to the conventional apparatus, and the bubbles generated when the silicon wafer is immersed generate an agitating flow. The stirring flow acts to uniformly bring the mixed acid solution to the surface of the silicon wafer, and as a result, the reaction progresses uniformly on the surface of the silicon wafer, resulting in cloudiness.
The occurrence of etching unevenness can be prevented, the surface shape is excellent, and the yield is significantly increased.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the device according to the present invention, FIG. A...Silicon wafer 2...Mixed acid solution 8...Bubble patent applicant Kyushu Denshi Metals Co., Ltd. Agent Patent attorney Masazumi Mori Figure 1 A...Silicon wafer 2...Mixed acid solution 8...・Bubble figure 2 Kusunoki slimming

Claims (1)

[Claims] A silicon wafer etching apparatus that immerses a silicon wafer in a mixed acid solution and etches the silicon wafer therein, characterized in that the mixed acid solution is stirred by emitting fine air bubbles into the mixed acid solution. Etching equipment for semiconductor silicon wafers.