JPH01244636A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To generate the lateral extension of a trench only at the time of isotropic etching, and to obtain a semiconductor device having the small lateral extension of an inter-element isolation oxide film by conducting anisotropic etching in addition to isotropic etching in a forming process for the trench. CONSTITUTION:The main surface of an silicon substrate 1 exposed by an opening section 4 is removed through an isotropic etching method, using an silicon nitride film 3 and an silicon oxide film 2 as masks, and a trench 5 is formed. The surface of the trench 5 is oxidized, an silicon oxide film 6 is grown, and an silicon nitride film 7 is deposited onto the film 6. The silicon nitride film 7 and an silicon oxide film 8 deposited on the base of the trench 5 are removed through an anisotropic etching method while employing an 'eave' projected to the top face of the trench 5 as a mask, and the opening section 8 is shaped. The silicon substrate 1 exposed to the opening section 8 is taken off using the silicon nitride film 7 and the silicon oxide film 8 as masks, and a trench 9 is formed and an inter-element isolation oxide film 10 is shaped through oxidation treatment while employing the silicon nitride films 3 and 7 as masks. Accordingly, the lateral extension of an inter-element isolation region diminishes, thus reducing an isolation region.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a method for manufacturing a semiconductor device including a step of electrically isolating elements using oxide.

[Conventional technology]

As a method for separating oxide films between elements in semiconductor devices,
A first oxidation-resistant film is provided on a silicon semiconductor substrate, and the first oxidation-resistant film in a region corresponding to the isolation region is removed, and at least a portion of the first oxidation-resistant film is provided below the first oxidation-resistant film on the silicon semiconductor substrate. There is a method in which a trench having an extending sidewall is formed, a second oxidation-resistant film adjacent to the first oxidation-resistant film is provided on the trench, and then the silicon semiconductor substrate is subjected to oxidation treatment. .

FIGS. 2(a) to 2(e) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an example of a conventional method for separating elements of a semiconductor device.

First, as shown in FIG. 2 (a), a silicon oxide film 2 is grown on the main surface of a silicon substrate 1 to a thickness of 10 to 1100 nm, and a silicon nitride film 3 is grown on the silicon oxide film 2 to a thickness of 10 to 300 nm. The silicon nitride film 3 and silicon oxide film 2 are selectively etched using photolithography technology to form openings 4, and the main surface of the silicon substrate 1 in the region corresponding to the isolation region is etched. selectively exposed.

Next, as shown in FIG. 2(b), the main surface of the silicon substrate 1 exposed through the opening 4 is removed by isotropic etching using the silicon nitride film 3 and the silicon oxide film 2 as masks. Then, spring 5 is formed.

Next, as shown in FIG. 2(c), the surface of the eraser 5 is oxidized to grow a silicon oxide film 6 to a thickness of 10 to 1100 nm, and a silicon nitride film 7 is further formed thereon to a thickness of 10 to 300 nm.
Deposited to a thickness of . At this time, the silicon nitride film 7 is deposited on the silicon oxide film 6 on the bottom and side surfaces of the trench 5, and is also formed around the "eaves" protruding from the top surface of the trench 5.

Next, as shown in FIG. 2(d), the silicon nitride film 7 deposited on the bottom surface of the groove 5 is removed by anisotropic etching using the eaves J protruding from the top surface of the groove 5 as a mask. An opening 8 is formed. Therefore, the silicon nitride film 7
remains.

Next, as shown in FIG. 2(e), silicon nitride 3 and 7
The element isolation oxide film 10 is formed by performing oxidation treatment using the mask as a mask.
form.

[Problem to be solved by the invention]

The device isolation oxide film formed by the method described above is
The structure of the oxide film becomes smaller than when the silicon nitride film 7 is not deposited on the side surfaces of the trench. However, when a particularly thick element isolation oxide film is used, the structure has a disadvantage that the isolation region cannot be reduced because the structure becomes larger in proportion to the thickness.

[Means to solve the problem]

The method for manufacturing a semiconductor device of the present invention includes the steps of: forming a first oxidation-resistant film having a first opening in an element isolation region to be formed in a semiconductor substrate; isotropically etching the semiconductor substrate using a mask as a mask to form a first groove wider than the opening;
forming a second oxidation-resistant film covering the surface of the groove;
forming a second opening corresponding to the first opening in the second oxidation-resistant film on the bottom surface of the first hole to expose the surface of the semiconductor substrate; forming a second groove by anisotropically etching the bottom surface of the first groove using first and second oxidation-resistant films as masks; and using first and second acid-resistant films as masks to form a second groove. and a step of performing oxidation.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(f) are cross-sectional views of a semiconductor chip shown in order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1(a), a silicon oxide film 2 is grown to a thickness of 10 to 1100 nm on the main surface of a silicon substrate 1, and a silicon nitride film 3 is grown on the silicon oxide film 2.
is deposited to a thickness of 10 to 300 nm, and the silicon nitride film 3 and the silicon oxide film 2 are selectively etched using photolithography technology to form openings 4, and the silicon substrate in the region corresponding to the isolation region is etched. The main surface of 1 is selectively exposed.

Next, as shown in FIG. 1(b), the main surface of the silicon substrate 1 exposed through the opening 4 is removed by isotropic etching using the silicon nitride film 3 and the silicon oxide film 2 as masks. Form 5.

Next, as shown in FIG. 1(c), the surface of the groove 5 is oxidized to grow silicon oxide M6 to a thickness of 10 to 300 nm, and a silicon nitride film 7 is grown thereon to a thickness of 10 to 300 nm. Deposits in thickness. At this time, the silicon nitride film 7 fills up to 50%
It is deposited on the silicon oxide film 6 on the top and side surfaces, and also around the "eaves" projecting above the groove 5.

Next, as shown in FIG. 1(d), the silicon nitride film 7 and the silicon oxide film 8 deposited on the bottom surface of the wafer 5 are anisotropically etched using the eaves J protruding from the top surface of the wafer 5 as a mask. The aperture 8 is formed by removing the aperture 8 by a method. Therefore, the silicon nitride film 7 remains on the side surfaces of the groove 5.

Next, as shown in FIG. 1(e), the silicon substrate 1 exposed in the opening 8 is removed by anisotropic etching using the silicon nitride film 7 and the silicon oxide film 8 as a mask to form the groove 9. Form.

Next, as shown in FIG. 1(f), an oxidation process is performed using the silicon nitride films 3 and 7 as masks to form an element isolation oxide film 10.

When an element isolation oxide film is not formed using the conventional technique, the construction thickness l of the element isolation region by oxidation treatment increases in proportion to the thickness of the element isolation oxide film formed. On the other hand, in the present invention, where L is the construction method of the element isolation region by oxidation treatment, L is determined only by the depth of the hole formed by the isotropic etching method. Therefore, when forming an element isolation region with the same thickness in the prior art and the present invention, the ratio of the isotropic etching amount to the anisotropic etching amount in the present invention is 1; x
Then, compared to the conventional technology, the construction method L of the isolation region of the present invention is smaller, and L=e−kx (k is a constant).
becomes. Therefore, according to the present invention, the structure size is reduced by k x compared to the construction method of the prior art, and the separation area is reduced.

In the above embodiment, the groove 5 was formed by removing the silicon substrate by isotropic etching, but instead, the opening 4 was oxidized and the silicon oxide film was removed by isotropic etching. Grooves 5 can also be formed. The subsequent steps are the same as in the above embodiment. Even in this case, as in the above embodiment, the structure of the isolation region becomes small, and
This results in a reduction in area.

〔Effect of the invention〕

As explained above, in the present invention, by performing anisotropic etching in addition to isotropic etching in the groove forming process, the structural gap in the structure occurs only during isotropic etching, so that separation between elements is achieved. This has the effect that it is possible to obtain a semiconductor device in which the structure of the oxide film is small.

[Brief explanation of the drawing]

1(a) to 1(f) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining one embodiment of the present invention, and FIG. 2(a)
) to (e) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an example of a conventional method for separating elements of a semiconductor device. ■...Silicon substrate, 2...Silicon oxide film, 3.
...Silicon nitride film, 4...Opening part, 5...Groove, 6
... silicon oxide film, 7... silicon nitride film, 8.
. . . Opening portion, 9 . . . Groove, 10 . . . Inter-element isolation oxide film.

Claims (1)

[Claims] a step of forming a first oxidation-resistant film having a first opening in an element isolation region to be formed on a semiconductor substrate; forming a second oxidation-resistant film covering the surface of the first groove; and forming a second oxidation-resistant film on the bottom surface of the first groove. Said second
forming a second opening corresponding to the first opening in the oxidation-resistant film to expose the surface of the semiconductor substrate; and masking the first and second oxidation-resistant films. the step of anisotropically etching the bottom surface of the first groove to form a second groove; and the step of performing oxidation using the first and second acid-resistant films as masks. A method for manufacturing a semiconductor device.