JPS58168264A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To increase the integration of a semiconductor device by selectively oxidizing the exposed part of a semiconductor substrate to form an oxidized film, then etching part of the film to remain in a thin laminar state, then forming an anti-oxidative film on the surface of the exposed substrate, thereafter again oxidizng to form an oxidized film of the prescribed pattern and thickness, thereby reducing the width of a bird beak. CONSTITUTION:A nitrided silicon film 14 is formed on a silicon substrate 12, which is selecteively oxidized to form an oxidized silicon film 16a, the film 16a is etched under control, thereby allowing a thin oxidized silicon film 16c to remain on the bottom of a groove. Accordingly, when it is treated in an ammonia atmosphere, a nitrided silicon film 18 is formed only the part which is contacted with the original bird beak. Subsequently, when it is oxidized to form an oxidized silicon film 16d, the lateral starting point of the oxidation is beforehand by approx. 0.5(mum) from that in the conventional technique. In this manner, the width of the eventual bird beak is reduced by approx. 0.5(mum) than that of the conventional technique.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, particularly a method for selectively oxidizing a semiconductor substrate or layer.

(2) Prior art and selective oxidation Selective oxidation utilizes the property that silicon nitride and other films do not allow oxygen to pass through, and selectively oxidizes only the necessary portions of the surface of the semiconductor substrate or layer on the silicon cape. It's a method. 1
FIG. 111 is a diagram for explaining a conventional selective oxidation method. Usually, a silicon nitride film 4 is formed on a silicon substrate 2 and then buttered to selectively oxidize the surface of the substrate to form an oxide film 6. In this case, oxidation not only occurs in the depth direction but also penetrates into the lateral direction to some extent, so-called bird's peak
'sb@ak) produces 6m. The width of such bird's peak 6a is generally about half the thickness of the oxide film, and 1
When an oxide film with a thickness of [ayx] is formed, the width is about 0.5 (
A bird's peak of μ is created.

However, since oxidation of silicon is accompanied by volumetric expansion, in order to prevent the selectively oxidized portion from forming a level difference with the silicon substrate, the oxide film that has been formed is usually removed completely. ), the exposed silicon is then reoxidized to form an oxide film 6'. However, in this case, the progress of oxidation in the lateral direction further increases, and the bird's peak 6' in an oxide film with a thickness of 1 μm due to this double oxidation becomes approximately 0.5 to 1 (#IIL). also reach.

The presence of such bird's peaks is one of the reasons why it is difficult to achieve high integration of semiconductor devices.

(3) Purpose of the Invention The present invention builds on the above-mentioned conventional techniques and provides a method that reduces the width of the bird's peak in selective oxidation and is useful for manufacturing highly integrated semiconductor devices.

(4) Structure of the invention In order to achieve the above object, the present invention selectively forms an oxidation-resistant film on a semiconductor substrate, and then selectively oxidizes the exposed portion of the semiconductor substrate. forming a film, then etching the oxide film so that a part of the oxide film remains in a thin layer on the semiconductor substrate, and then forming an oxidation-resistant film on the surface of the semiconductor substrate exposed by the etching, A method of manufacturing a semiconductor device is provided, which includes forming an oxide film with a predetermined pattern and thickness by subsequently performing oxidation treatment again.

The present invention will be explained in detail below using examples.

FIG. 2 is a diagram for explaining the present invention in detail. A silicon nitride film 14 is deposited on the silicon substrate 12 at a thickness of about 1500 (A
), and after patterning, approximately 1000 ~
The silicon substrate 2 is selectively oxidized in an oxidizing atmosphere of 1100C (see FIG. 2(a)). Silicon oxide film 16
The thickness of the silicon oxide film 16a is approximately 1 (μ corner), and the width of the bird peak on one side is approximately 0.5 μ.Next, the silicon oxide film 16a is subjected to controlled etching using a hydrofluoric acid-based etching solution. Then, a thin silicon oxide film 16c of about 1000 Å (see FIG. 2 (b)) is left at the bottom of the groove formed by etching. Of the parts that had previously been covered, only the shoulder part of the groove that was in contact with Bird's Peak is exposed to the outside, and the flat bottom part of the groove remains covered with an oxide film (see Figure 2). ) 0 Therefore, if the treatment is performed in an ammonia atmosphere of approximately 1100 (C), nitride sludge will be produced only on the shoulders of the grooves exposed to the outside of the silicon substrate 2, that is, the portions that were in contact with the original bird's peaks. A silicon nitride film 18 is formed (see FIG. 2).The silicon nitride film 1B of i needs to be thin enough as long as it can block oxygen, so it is set to be about 50 (A) thick. In this way, the silicon nitride film 18 is formed in the part that was in contact with the original bird's peak, that is, the part with a width of about 0', 5 (a+m), which makes it difficult to maintain the lateral direction of the reoxidation that will be performed later. This means that the starting point was pulled back to its original position by about 0.5 [μm] compared to the case of reoxidation in the prior art. □ After this, the silicon oxide film 16g remaining at the bottom of the groove was arbitrarily removed. again about 1000 to 11 with or without removal.
It is oxidized in an oxidizing atmosphere at 00 [℃] to about 1 [μ expletive].
A silicon oxide film 16d having a thickness of . The bird's peak of the silicon oxide film 16d thus obtained has a width of about 0.5 Cμ on one side, but as mentioned above, the lateral starting point of oxidation is about 0.5
(gm), the width of the final bird's peak is about 0.5 (slB) smaller than that of the prior art (see FIG. 2)).

Thereafter, the silicon nitride film 4.8 is removed and elements are formed using a conventional method.

It should be noted that before forming the silicon oxide film 16d, whether or not the silicon oxide film 16''c remaining in the groove is removed is determined.
Although this has nothing to do with the main aspect of the present invention, it can be removed in order to prepare the conditions for forming the silicon oxide film 16d.

(6) Effects of the Invention As is clear from the above explanation, as long as the present invention is carried out under the same nitride film and oxidation conditions as in the prior art, the width of the bird's peak in selective oxidation can be reduced according to the present invention. It is possible to make the device much smaller, and therefore the integration of the semiconductor device can be increased.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a semiconductor device in process order for explaining the selective oxidation process of the prior art, and FIG. 2 is a partial cross-sectional view of a conductor device in process order for explaining the present invention in detail. . 2,12...Semiconductor substrate (silicon), patent applicant: Fujitsu Limited Patent agent: Akira Aomi, patent attorney: Kazuyuki Nishidate, patent attorney: 1) Office: Male patent attorney: Akira Yamaguchi, Figure 1 (a) Figure 2 (a)

Claims (1)

[Claims] 1. Selectively form an oxidation-resistant film on a semiconductor substrate, then selectively oxidize the exposed portion of the semiconductor substrate to form an oxide film, and then a part of the oxide film is formed on the semiconductor substrate. The oxide film is etched in a thin layer, and then an oxidation-resistant film is formed on the surface of the semiconductor substrate exposed by the etching, and then oxidation treatment is performed again. Method for manufacturing a semiconductor device including forming a thick oxide film