JPS63181330A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To shorten the process by cleaning the inner surface of a groove formed in a silicon substrate using a cleaning liquid which is faster in the etch rate of the etching mask of the silicon substrate than in the etch rate of the substrate, thereby beveling the opening part of the groove. CONSTITUTION:With a silicon dioxide film 22 on a silicon substrate 21 as a mask, the silicon substrate 21 is etched to form a groove 25 in the substrate 21, and thereafter the inner surface of the groove 25 is cleaned using a cleaning liquid which is faster in the etch rate of the etching mask 22 than in the etch rate of the silicon substrate 21, e.g., a mixed liquid of hydrofluoric acid, acetic acid and pure water. As a result, in a groove opening part 24, the silicon substrate 21 surface surrounding the opening part 24 is exposed. And, when the substrate 21 surface surrounding the groove opening part 24 is exposed in this way, the substrate silicon of the corner section of the groove opening part 24 is etched from the lateral and vertical directions, so the corner section becomes a taper 28, whereby a groove with a taper 28 in the opening part 24 is formed. With this, the etching of the substrate can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a semiconductor device, and particularly to a groove forming technique.

(Conventional technology) A conventional groove forming technique will be explained with reference to FIG.

First, silicon oxide @12 having a thickness of 7000λ is formed on a silicon substrate 11 (FIG. 3(a)). Next, a resist 13 is applied onto the silicon oxide film 12 and patterned (FIG. 3(b)). Next, using the fcV cyst 13 as a mask, the silicon oxide film 12 is etched as an etching mask layer by the RIE method, an opening 14 for forming a groove is formed in the silicon oxide film 12, and then the resist 13 is removed (third Figure (C)). After that, silicon oxide M1
2 as a mask, the silicon substrate 11 is etched by the RIE method to form a groove 5 in the substrate 11 (see FIG.
d)). Next, the deposited film and damaged layer 16 generated on the inner wall surface of the formed groove 15 are removed by a wet method, and then the inner wall of the groove 15 is oxidized to form an oxide film 17 (see FIG. 3). e)).

However, in the above method, when the inner wall of the groove 15 is oxidized, stress is generated at the opening of the groove 15, leading to deterioration of the withstand voltage.

Therefore, in order to alleviate the stress generated during oxidation, a third
After the completion of the process shown in FIG. 4(C), the silicon substrate 11 is etched as an etching mask layer as shown in FIG. By using the silicon substrate 11 as an etching mask layer using a method, nine inclined grooves 15a are formed at the openings as shown in FIG. 4(b). FIG. 4(c) shows the next state in which an oxide film 171L is formed in the groove 15a after cleaning.

(Problems to be Solved by the Invention) However, 1. In the above method, it is necessary to divide the silicon substrate 11 into two parts to form an etching mask layer in order to form the inclined groove 15a, which lengthens the process. Nine points.

The present invention has been made in view of the above points, and an object thereof is to provide a method for manufacturing a semiconductor device that can form a groove with an inclined opening in a reduced number of steps.

(Means for Solving the Problems) In the present invention, grooves are formed in the silicon substrate by using an etching mask layer on the surface of the silicon substrate as a mask. Etching the silicon substrate and the etching mask layer, and cleaning the inner wall of the groove using a cleaning solution faster than the etching speed of the etching mask layer of the silicon substrate. .

(Function) When the inner wall of the groove is cleaned using the cleaning liquid, the silicon substrate and the etching mask layer become the same as the etching mask layer, but at this time, the etching mask layer is removed from the silicon substrate. In the unlikely event that the etching mask layer is etched at a high speed, at the groove opening, the
As shown in , the silicon substrate surface around the trench opening is exposed. When the bottom surface of the substrate around the trench opening is exposed in this way, the substrate silicon at the corner of the trench opening is covered with an etching mask layer from both the horizontal and vertical directions, so that this area is exposed as shown in FIG. 2(c). As shown, the groove becomes tapered (slanted) at the opening.

(Example) An embodiment of the present invention will be described below with reference to FIG.

First, as shown in FIG. 1 (+L), the silicon substrate 21
A silicon oxide film 22 with a thickness of 1000^ is grown thereon by a thermal oxidation method.

Next, a V cyst 23 is applied onto the silicon oxide film 22, exposed and developed, and the resist 23 is patterned (FIG. 1(b)).

Next, using the patterned resist 23 as a mask, the silicon oxide film 22 is etched by RIE to form an opening 24 for forming a groove in the silicon oxide film 22, and then the resist 23 is removed (first Diagram (C)
).

Thereafter, using the silicon oxide film 22 as an etching mask layer as a mask, the silicon substrate 21 is etched using a chlorine-based gas by the RIE method to form a $25 layer on the substrate 21 (
Figure 1(d)].

Next, groove 2 was prepared using a mixture of hepturic acid, nitric acid, and pure water.
5. Clean the inner wall, as shown in Figure 2 (a).
Deposited film 26 and damaged layer 27 occurring on the inner wall surface of
remove. At this time, using the above mixed solution as a cleaning solution,
Moreover, if the etching mask layer is continued even after the deposited film 26 and the damaged layer 27 are removed, the silicon oxide film 22 and the silicon substrate 21 will be used as the etching mask layer, and in this case, the silicon oxide film 22 will be larger than the silicon substrate 21. Since the etching mask layer is etched at a high speed, the surface of the silicon substrate 21 around the opening of the groove 25 is exposed at the opening of the groove 25, as shown in FIG. 2(b). When the surface of the substrate 21 around the opening of the groove 25 is exposed in this way, the substrate silicon at the corner of the opening of the groove 25 is covered with an etching mask layer from both the horizontal and vertical directions, so that this area is removed as shown in FIG.
As shown in a), it becomes a taper 28, and the opening has a taper (
A groove 25 with a slope 28 is formed as shown in FIG. 1(e).

After cleaning and forming the slope are performed simultaneously in this way, the inner wall of the groove 25 is finally oxidized to form an oxide film 2.
9 (FIG. 1(f)).

In the above embodiment, the silicon oxide film 2 is formed by thermal oxidation using the silicon substrate etching mask layer as a mask material.
2 was used, but it is also possible to use a sub-silicon oxide film deposited by the CVD method or a phosphoric oxide film added with impurities (P, B, As, etc.).

A resist or a silicon nitride film can be used as the mask material for the silicon substrate etching mask layer. In that case, a solution or mixed solution (sulfuric acid) that can form the etching mask layer by adding one mask material to hydrofluoric acid or nitric acid.

The same method as in the above embodiment can be achieved by mixing hot phosphoric acid, etc.).

In addition, if the etching mask layer or the deposited film 26 generated after the etching mask layer cannot be formed into an etching mask layer with hydrofluoric acid or nitric acid, the deposited film 26 can be mixed with a liquid or mixed solution that can be formed into an etching mask layer. It can be similar to the above-example.

Furthermore, the etching mask layer of the silicon oxide film and the silicon substrate was added to monofluoric acid and nitric acid to control the speed.
Other liquids or mixed liquids may be mixed.

In addition, when the silicon substrate etching mask layer has a multilayer mask structure (silicon oxide film - silicon nitride film - silicon oxide film, etc.), the film in contact with the silicon substrate can be coated with a solution or mixed solution that forms the etching mask layer. By mixing it with hydrofluoric acid and nitric acid, it can be done in the same way as in the above embodiment (if the film in contact with the silicon substrate can be etched as an etching mask layer with hydrofluoric acid and nitric acid, only hydrofluoric acid and nitric acid are sufficient) .

(Effect of the invention) As explained in detail above, according to the method of this invention,
Since the groove opening can be sloped using the cleaning process, only one step is required to remove the etching mask layer of the substrate, and the process is performed using the same reduced number of steps as the non-slanted groove forming method shown in Figure 3. A sloped groove can be formed. According to this method, the inclination angle of the groove opening can be arbitrarily controlled by changing the composition of the cleaning liquid.

[Brief explanation of the drawing]

FIG. 1 is a process sectional view showing an embodiment of the semiconductor device manufacturing method of the present invention, FIG. 2 is a detailed sectional view showing a partial process of the above-mentioned embodiment, and FIG. 3 is a conventional groove forming method. FIG. 4 is a process cross-sectional view showing the conventional improved groove forming technique. 21... Silicon substrate, 22... Silicon oxide film,
24... Opening, 25... Groove, 26... Deposited film,
27... Damage layer, 28... Taper (slope). Figure 2

Claims (1)

[Claims] (a) A step of etching the silicon substrate using an etching mask layer on the surface of the silicon substrate as a mask to form a groove in the substrate; (b) After that, using a cleaning solution, particularly the silicon substrate and the etching mask; etching the layer, and cleaning the inner wall of the groove using a cleaning solution in which the etching rate of the etching mask layer is faster than the etching rate of the silicon substrate, and at the same time slopes the opening of the groove. A method for manufacturing a semiconductor device.