JPS61201444A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve a rate of integration of a CMOS integrated circuit without causing a latch-up phenomenon by separating elements securely. CONSTITUTION:A silicon oxide film 2 as a buffer is formed by oxidizing a surface of a silicon substrate 1 and an SiN film 3 is formed on it. After the surface of the SiN film 3 is patterned by a photoresist 4 or the like, grooves 5 are formed in the substrate 1 by isotropic etching. A silicon oxide film 6 as a buffer is formed by oxidizing the inside surface of the groove 5. After a thin SiN film 7 is formed on the substrate, grooves 8 are further formed in the substrate 1 by etching the bottoms of the grooves 5. By oxidizing the exposed substrate 1, an oxide domain 9 is formed to separate an element forming domain 1'. The SiN films 3 and 7 are removed and the grooves 8 are filled with oxide films 10. With this constitution, the element forming domain 1' is completely separated from the substrate 1 by the oxide domain 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device suitable for a (1108 (complementary MO8) integrated circuit).

[Technical background of denting and its problems]

In conventional CMO8 integrated circuits, as elements are made smaller and the degree of integration is increased, so-called latch-up phenomena are more likely to occur due to external noise, etc.

This makes it difficult to increase the degree of integration.

Two techniques are currently being considered to prevent the latch-up phenomenon and improve the degree of integration. (a) 8
0 I (5ilicon On In5ulator
) That is, a method in which the element parts are separated from each other on an insulator, and (01) a method in which element isolation is performed by digging trenches between elements and filling them with an insulator.

However, in the method (a) above, it is difficult to epitaxially form silicon on an insulator as a substrate, and the chip price becomes high.

In the method (b) above, elements cannot be completely separated.

[Purpose of the invention]

The present invention has been made in view of the above circumstances.

This paper aims to provide a method for manufacturing a semiconductor device that can improve the degree of integration of a CMO8 integrated circuit by advancing the latter method of the prior art to completely isolate elements and improve the degree of integration of a CMO8 integrated circuit. In the present invention, a silicon oxide film is formed on the surface of a semiconductor substrate, a silicon nitride film is formed thereon, and then the silicon nitride film and silicon oxide film in an element isolation region are etched, and the semiconductor substrate is etched to an appropriate depth. and the process of forming.

After forming a silicon oxide film on the surface of the semiconductor substrate exposed in this process and forming a silicon nitride film on it, the silicon nitride film and silicon oxide film at the bottom of the trench formed in the semiconductor substrate are removed and the silicon oxide film is removed to an appropriate depth. A process of etching a semiconductor substrate.

This method includes a step of oxidizing the semiconductor substrate exposed in this step to form an oxidized region under the element formation region of the semiconductor substrate.

[Embodiments of the invention]

An embodiment of the present invention will be explained below with reference to the drawings. First, as shown in FIG. 1 (al), the surface of a silicon substrate 1 is oxidized to form a silicon oxide film 2 as a buffer material, and a SiN film 3 is formed thereon by deposition.Next, as shown in FIG. As shown in (b), element isolation regions are patterned using photoresist 4, etc., and then RIE
(Reactive Ion Etching) Grooves 5 are formed in the substrate 1 by isotropic etching. Thereafter, as shown in FIG. 1C, the inside of the trench is oxidized to form a silicon oxide film 6 as a buffer material. This oxide film 6 is formed by oxidation to the same degree as the oxide film 2. Next, as shown in IJI diagram (d), a SiN film 2 is formed on the substrate by deposition.

This 8iN film 2 is formed much thinner than the 8iN film 3.

Next, as shown in FIG. 1 (el), the groove 5 is
Further grooves 8 are formed in the substrate 1 by etching the bottom of the substrate 1.

Next, as shown in FIG. 1 (fl), the substrate 1 exposed by the formation of the groove 8 is oxidized.

Oxidized regions 9 are formed to isolate element forming regions 1'. Next, as shown in FIG. A resist may be applied thereon, and then the resist and oxide film may be etched.

The element forming region 1' thus formed is completely separated from the substrate 1 by the oxidized region 9.

This can reliably prevent latte-up when the degree of integration is increased.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, in FIG.
Although oxidation was performed until they intersected under the element formation region 1', a considerable latch-up prevention effect can be expected even if the oxidation is stopped before they intersect.

〔Effect of the invention〕

As described above, according to the present invention, element isolation can be performed reliably and the degree of integration of a CMO8 integrated circuit can be improved without causing latch-up phenomena.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1(a) to 1(g) are manufacturing process diagrams showing one embodiment of the present invention. 1... Semiconductor substrate, 2, 6... Silicon oxide film. 3.7...8iNII! , 4... resist, 5, 8
···groove.

Claims (3)

[Claims] (1) After forming a silicon oxide film on the surface of a semiconductor substrate and forming a silicon nitride film thereon, the silicon nitride film and the silicon oxide film in the element isolation region are etched, and the groove is etched in the semiconductor substrate to an appropriate depth. After forming a silicon oxide film on the surface of the semiconductor substrate exposed in this step and forming a silicon nitride film on it,
A second step of removing the silicon nitride film and silicon oxide film at the bottom of the groove formed in the semiconductor substrate and etching the semiconductor substrate to an appropriate depth, and oxidizing the semiconductor substrate exposed in this step to remove the silicon oxide film from the bottom of the groove formed in the semiconductor substrate. A method of manufacturing a semiconductor device, comprising: a third step of forming an oxidized region below the element forming region. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the etching of the semiconductor substrate performed in the second step is reactive ion etching. (3) In the third step, the semiconductor substrate is oxidized until the oxidized regions intersect under the element formation region of the semiconductor substrate.
A method for manufacturing a semiconductor device according to paragraph 1.