JPH07115083A - Etching method for silicon oxide film - Google Patents

Abstract

PURPOSE:To prevent chipped-off portions of the resist film on wafer edges from becoming particles by removing portions positioned on wafer edges of a silicon oxide film and also removing the silicon oxide film of a semiconductor wafer by etching with a resist film as a mask. CONSTITUTION:A silicon oxide film 2 is formed on the surface of a semiconductor wafer 1. A resist film 3 is formed on the silicon oxide film 2, a portion of the resist film 3 on a wafer edge is removed by exposure and developing treatment, and thereafter a portion of the silicon oxide film 2 on the wafer edge is removed by etching the silicon oxide film 2 with the resist film 3 as a mask. A resist film 4 is newly coated to the whole surface so as to cover the wafer edge. Since the silicon oxide film 2 has been removed on the wafer edge, chipping-off of resist hardly occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method for a silicon oxide film, and more particularly to an etching method for a silicon oxide film on a semiconductor wafer by selectively wet etching the silicon oxide film with a resist film as a mask.

[0002]

2. Description of the Related Art Selective etching of a silicon oxide film formed on a surface portion of a semiconductor wafer by thermal oxidation, impurity diffusion, CVD or the like is performed by coating a resist film on the silicon oxide film and then etching the silicon oxide film. exposure,
The development process is performed, and as shown in FIG. 6B, wet etching is performed using the remaining resist film as a mask and hydrofluoric acid (HF or B.HF) as an etching solution. When the silicon oxide film is selectively etched in the related art,
As shown in (A), it was in a state of being entirely formed on the surface of the semiconductor wafer. In the figure, 1 is a semiconductor wafer, 2 is a silicon oxide film, and 3 is a resist film.

[0003]

However, the conventional etching method for a silicon oxide film has a problem that the contamination by particles is not small, and the cause of the contamination was investigated, and the contamination during the wet etching of the silicon oxide film was investigated. It was found that this was caused by the lack of the portion of the resist film on the edge of the semiconductor wafer. The details will be described below.

First, in order to measure the contamination of the silicon oxide film by the particles during the wet etching, as shown in FIG. 7, the particle measuring wafer 1a is faced to the sample semiconductor wafer 1 on which the silicon oxide film is wet-etched. When the orientation flat is set in the etching bath (6 is an etching liquid) 5 downward, the silicon oxide film 2 is etched, and then the particle measurement wafer 1a is tried to be observed. An example of the particle distribution as shown in was obtained. Then, when the cause of contamination by particles was further investigated, as shown in FIG.
Resist chipping is likely to occur on the wafer edge, and particles caused by the resist generated on the lower wafer edge of the vertically standing semiconductor wafer adhere to the surface of the semiconductor wafer while flowing from bottom to top according to the flow of the etching solution 9. There was found.

Further, when the cause of the occurrence of resist chipping was investigated, as shown in FIG. 6B, the semiconductor wafer 1 had a chamfered shape at the edge portion and the edge portion became thin, resulting in silicon oxide. It was found that the surface of the film 2 becomes lower at the edge portion, the resist film 3 covering the silicon oxide film 2 becomes thinner on the wafer edge, and the thinner the resist film 3 becomes, the easier it becomes to chip, and the resist chip becomes a particle. .

The present invention has been made to solve the above problems, and in a method for etching a silicon oxide film on a semiconductor wafer using a resist film as a mask, the wafer edge of the resist film is used. The purpose is to prevent the upper portion from becoming chipped and becoming a particle.

[0007]

According to a first aspect of the present invention, there is provided a method for etching a silicon oxide film, wherein a portion of the silicon oxide film located on a wafer edge is removed, and then the resist film is used as a mask to remove the silicon oxide film on the semiconductor wafer. It is characterized by being removed by etching. The method for etching a silicon oxide film according to claim 2, wherein a resist film is formed on the surface of the silicon oxide film on the semiconductor wafer so as not to cover at least the wafer edge, and then the silicon oxide film on the semiconductor wafer is used as a mask. It is characterized in that the film is removed by etching.

[0008]

According to the method for etching a silicon oxide film of claim 1, the silicon oxide film is etched using the resist film as a mask after removing the portion of the silicon oxide film located on the wafer edge. As shown, there is no thinning on the wafer edge. Therefore, it is possible to avoid the conventional problem that the resist film becomes thin on the wafer edge and the resist chipping occurs, and eventually particle contamination can be eliminated.

According to the method for etching a silicon oxide film of claim 2, a resist film for selective etching is formed on the silicon oxide film of the semiconductor wafer so as not to cover the wafer edge, and the outer resist film is used as a mask for etching. Therefore, it is possible to avoid the conventional problem that the resist film is thinned on the wafer edge to cause resist chipping, and it is possible to eliminate particle contamination. Since no special step of removing only the portion of the silicon oxide film located on the wafer edge is required, the number of steps can be reduced as compared with the etching method according to the first aspect.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An etching method for a silicon oxide film according to the present invention will be described in detail below with reference to illustrated embodiments. Figure 1
(A) thru | or (E) is sectional drawing which shows one Example of the etching method with respect to the silicon oxide film of this invention in order of process. (A) As shown in FIG. 1A, a silicon oxide film (SiO ₂ ) 2 is formed on the surface of a semiconductor wafer 1. When the silicon oxide film 2 is formed by CVD, the silicon oxide film 2 is not formed on the back surface, but when it is formed by thermal oxidation, the silicon oxide film 2 is also formed on the back surface as shown by the chain double-dashed line. To be done.

(B) Next, a resist film 3 is formed on the silicon oxide film 2, and the resist film 3 is exposed and developed to remove the portion of the resist film 3 on the wafer edge. As shown in (B), the silicon oxide film 2 is etched using the resist film 3 as a mask to remove the portion of the silicon oxide film 2 on the wafer edge. In addition, 1a is an orientation flat. Then, the resist film 3 is removed. FIG. 2 shows the resist film 3
It is a top view showing the state after removal.

(C) Next, as shown in FIG. 1C, the resist film 4 is again formed on the silicon oxide film 2 of the semiconductor wafer 1.
It is applied over the entire surface where the mark is formed. Of course, it is formed so as to cover the wafer edge as well. Then, FIG. 1 (C)
As shown in FIG. 5, the resist film 4 is thicker on the wafer edge than the conventional one because the silicon oxide film 2 is removed on the wafer edge. Therefore, the thinner the resist film 4 is, the less likely the resist chipping is to occur.

(D) After that, the resist film 4 is exposed to light,
By development, patterning is performed as shown in FIG. (E) After that, as shown in FIG. 1E, the silicon oxide film 2 is wet-etched using the resist film 4 as a mask. FIG. 3 is a sectional view showing the state during the wet etching.

As described above, since the silicon oxide film 2 is removed on the wafer edge, the resist film 4 is thicker on the wafer edge than before, so that resist chipping is unlikely to occur. Therefore, the problem that it becomes particles and contaminates the surface of the semiconductor wafer 1 can be significantly reduced. FIG. 4 shows various samples of the number of particles (the number of particles per wafer) attached on the semiconductor wafer by etching using the resist film of the silicon oxide film as a mask (the cross section is shown in the right part of FIG. 4). The particle size is divided into three types. The white part of this bar graph shows particles with a diameter of 0.3 to 0.5 μm, and the hatched part shows particles with a diameter of 0.5 to 1.0 μm.
The blackened portions indicate particles larger than 1 μm.

The sample shown in FIG. 4 is a conventional example. The sample is a silicon oxide film formed entirely on a semiconductor wafer (on one main surface), and a resist film is formed on a portion other than the wafer edge on the semiconductor wafer. The formed film and the sample are shown in this embodiment, and the sample is formed so that neither the silicon oxide film nor the resist film covers the wafer edge. As is clear from FIG. 4, according to this embodiment (sample), the number of particles is reduced to about 1/4 to 1/5 of that of the conventional case (ampoule).
In addition, when the resist film is patterned (sample,) is not patterned (sample,)
It can be seen from Fig. 4 that the number of particles is larger than that of the above.

FIGS. 5A to 5D are sectional views showing another embodiment of the etching method for the silicon oxide film of the present invention in the order of steps. (A) As shown in FIG. 5A, a silicon oxide film (SiO ₂ ) 2 is formed on the surface of the semiconductor wafer 1. When the silicon oxide film 2 is formed by CVD, the silicon oxide film 2 is not formed on the back surface, but when it is formed by thermal oxidation, the silicon oxide film 2 is formed on the back surface as shown by a chain double-dashed line.
Is formed.

(B) Next, as shown in FIG. 5B, a resist film 3 is applied and formed on the silicon oxide film 2 so as not to cover the portion corresponding to the wafer edge. (C) After that, the resist film 3 is exposed and developed to be patterned as shown in FIG. 5 (C). (D) Thereafter, as shown in FIG. 5D, the silicon oxide film 2 is etched using the resist film 3 as a mask.

According to the present embodiment, the resist film 3 for selective etching is formed on the silicon oxide film 2 of the semiconductor wafer 1 so as not to cover the wafer edge, and the resist film is used as a mask for etching. It is possible to avoid the conventional problem that 3 is thinned on the wafer edge to cause resist chipping, and eventually particle contamination can be eliminated. Since a series of etching steps is not particularly required to remove only the portion of the silicon oxide film 2 located on the wafer edge,
The number of steps can be reduced as compared with the etching method according to the first aspect, and the manufacturing cost of the semiconductor device can be further reduced.

[0019]

According to the method of etching a silicon oxide film of the present invention, the portion of the silicon oxide film located on the wafer edge is removed, and then the silicon oxide film on the semiconductor wafer is removed by etching using the resist film as a mask. It is characterized by that. Therefore, claim 1
According to the method for etching a silicon oxide film, since the portion of the silicon oxide film located on the wafer edge is removed and the silicon oxide film is etched using the resist film as a mask, the resist film does not become thin on the wafer edge. . Therefore, it is possible to avoid the conventional problem that the resist film becomes thin on the wafer edge and the resist is chipped, and it is possible to eliminate particle contamination.

In the method for etching a silicon oxide film according to a second aspect of the present invention, a resist film is formed on the surface of the silicon oxide film on the semiconductor wafer so as not to cover at least the wafer edge, and then the resist film is used as a mask on the semiconductor wafer. The silicon oxide film is removed by etching. Therefore, according to the method for etching a silicon oxide film of claim 2, a resist film for selective etching is formed on the silicon oxide film of a semiconductor wafer so as not to cover the wafer edge, and the resist film is used as a mask for etching. It is possible to avoid the conventional problem that the resist film is thinned on the wafer edge to cause a resist chip, and eventually particle contamination can be eliminated. Since no special step of removing only the portion of the silicon oxide film located on the wafer edge is required, the number of steps can be reduced as compared with the etching method according to the first aspect.

[Brief description of drawings]

1A to 1E are cross-sectional views showing, in the order of steps, one embodiment of an etching method for a silicon oxide film according to the present invention.

FIG. 2 is a plan view showing a state after removing a portion of a silicon oxide film on a wafer edge in the embodiment shown in FIG.

FIG. 3 is a sectional view showing a state during selective etching in the embodiment shown in FIG.

FIG. 4 is a bar graph showing the number of particles for various samples.

5A to 5D are cross-sectional views showing another embodiment of the etching method for the silicon oxide film of the present invention in the order of steps.

6A and 6B are for explaining a conventional example, FIG. 6A is a plan view showing a semiconductor wafer before forming a resist film, and FIG. 6B shows a semiconductor wafer at the time of wet etching. FIG.

FIG. 7 is a cross-sectional view showing selective etching for particle measurement.

FIG. 8 is a plan view showing another example of a conventional particle distribution.

FIG. 9 is a cross-sectional view for explaining a conventional cause of particle contamination.

[Explanation of symbols]

 1 wafer 2 silicon oxide film 3 resist film

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 22, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Further, when the cause of the occurrence of resist chipping was investigated, as shown in FIG. 6B, the semiconductor wafer 1 had a chamfered shape at the edge portion and the edge portion became thin, resulting in silicon oxide. The surface of the film 2 is lowered at the edge portion, the resist film 3 covering the silicon oxide film 2 is thinned on the wafer edge, and when the resist film 3 is thinned, the silicon oxide film 2 is exposed and the exposed portion is etched.
On the etched portion of the resist film 3
The part existing in
Is easily chipped more, the resist chipping was found that the actual particle.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

According to the method for etching a silicon oxide film of claim 1, the silicon oxide film is etched using the resist film as a mask after removing the portion of the silicon oxide film located on the wafer edge. As shown, there is no thinning on the wafer edge. Therefore, the resist film becomes thin on the wafer edge and the silicon oxide film is exposed.
Etching progresses and the etching of the resist film
It is possible to avoid the conventional problem that the part where the base has been lost is chipped off, and it is possible to eliminate particle contamination.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

According to the etching method for the silicon oxide film according to claim 2, the selective etching resist film on a silicon oxide film of a semiconductor wafer formed so as not to cover the upper wafer edge etching the resist film as a mask Therefore, it is possible to avoid the conventional problem that the resist film is thinned on the wafer edge to cause resist chipping, and it is possible to eliminate particle contamination. Since no special step of removing only the portion of the silicon oxide film located on the wafer edge is required, the number of steps can be reduced as compared with the etching method according to the first aspect.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

(C) Next, as shown in FIG. 1C, the resist film 4 is again formed on the silicon oxide film 2 of the semiconductor wafer 1.
It is applied over the entire surface where the mark is formed. Of course, it is formed so as to cover the wafer edge as well. Then, FIG. 1 (C)
As shown in , since the silicon oxide film 2 is removed on the wafer edge , the resist film 4 becomes thin.
The silicon oxide film 2 is exposed and etched to form a resist film
The phenomenon that the underlayer 4 is lost cannot occur. Therefore, resist chipping is less likely to occur.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

As described above, since the silicon oxide film 2 is removed on the wafer edge , the resist film 4 is removed.
It becomes thinner and the silicon oxide film 2 is exposed and etched
The phenomenon that the underlayer of the resist film 4 is lost cannot occur.
Become. Therefore, resist chipping is unlikely to occur. Therefore, the problem that it becomes particles and contaminates the surface of the semiconductor wafer 1 can be significantly reduced. FIG. 4 shows the number of particles adhered on the semiconductor wafer by etching using the resist film of the silicon oxide film as a mask (wafer 1
The number of particles per sheet) is shown as a sample , and the particle size (in the right part of FIG. 4, a cross-sectional view is shown) is divided into three types. The white part of this bar graph shows particles with a diameter of 0.3 to 0.5 μm, the hatched part shows particles with a diameter of 0.5 to 1.0 μm, and the black part shows particles larger than 1 μm. .

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The sample in FIG. 4 is a conventional example,
The pull indicates that of this embodiment. Also clear from this Figure 4
This example (Sample ), The conventional (ServiceThe
The number of particles is about 1/4 to 1/5 that of pull)
To be reduced.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

[0017] (B) Next, a resist film 3 on the silicon oxide film 2, as shown in FIG. 5 (B), it is formed by coating as will covering a portion corresponding on the wafer edge. (C) After that, the resist film 3 is exposed and developed to be patterned as shown in FIG. 5 (C). (D) Thereafter, as shown in FIG. 5D, the silicon oxide film 2 is etched using the resist film 3 as a mask.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019]

According to the method of etching a silicon oxide film of the present invention, the portion of the silicon oxide film located on the wafer edge is removed, and then the silicon oxide film on the semiconductor wafer is removed by etching using the resist film as a mask. It is characterized by that. Therefore, claim 1
According to the method for etching a silicon oxide film, since the portion of the silicon oxide film located on the wafer edge is removed and the silicon oxide film is etched using the resist film as a mask, the resist film does not become thin on the wafer edge. . Therefore, the resist film becomes thin on the wafer edge and the silicon oxide film is exposed.
Then, etching progresses from the exposed portion, and the resist film
It is said that the part where the base is lost due to the etching of the
It is possible to avoid the cormorant conventional problems, and by extension it is possible to eliminate the mass-point pollution.

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Correction target item name] Figure 9

[Correction method] Change

[Correction content]

[Figure 9]

Claims (2)

[Claims] 1. A method of etching a silicon oxide film on a semiconductor wafer, wherein a resist film is used as a mask to perform a wet etching, a portion of the silicon oxide film located on a wafer edge is removed, and then the resist film is masked. Method for etching a silicon oxide film, characterized by removing the silicon oxide film on a semiconductor wafer by etching 2. A method for etching a silicon oxide film on a semiconductor wafer by wet etching using a resist film as a mask, wherein the surface of the silicon oxide film on the semiconductor wafer does not cover at least the wafer edge. And then removing the silicon oxide film on the semiconductor wafer by etching using the resist film as a mask, and an etching method for the silicon oxide film.