JPH03220748A - Method of isolation of elements in semiconductor device - Google Patents

Abstract

PURPOSE:To control the extension of an ion-diffused region by forming a smaller diffused region using a photomask, and then enlarging the region after ion implantation. CONSTITUTION:Nitride film 4 on an isolation region 7 is etched with an active region 5 masked by photoresist 6. Taking into consideration the extension of ion-diffused region, the size of the isolation region is reduced using a photomask 11. Ions 8 are implanted into the isolation region, where the silicon nitride 4 is removed, to prevent formation of parasitic channels between elements. The silicon nitride film 4, masked by the photoresist 6, is subjected to isotropic etching using Freon gas to form an enlarged isolation part 12. A semiconductor device with a smaller ion-diffusted region 10 is provided in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to element isolation thereof.

[Conventional technology]

FIGS. 2(a) and 2(b) are cross-sectional views of a semiconductor device for explaining an element isolation method in a conventional semiconductor device, in which 1 is a silicon substrate, 2 is a silicon oxide film,
3 is a polysilicon film, 4 is a silicon nitride film, 5 is an element region portion, 6 is a photoresist, 7 is an element isolation region portion,
8 is an ion for preventing parasitic channels between elements, 9 is a silicon oxide film for element isolation, and 10 is an ion diffusion region.

First, a silicon oxide film 2 as a base oxide thin film is formed on a silicon substrate 1, and a polysilicon film 3 and a silicon nitride film 4 are formed thereon. Next, the element region portion 5 is masked with a photoresist 6, and the silicon nitride film 4 in the element isolation region portion 7 is removed by etching. Next, ions 8 for preventing inter-element parasitic channels are implanted into the element isolation region portion 7 from which the silicon nitride film 4 has been removed. For example, boron is used as the ions 8 for preventing parasitic channels between elements.

This is to prevent the semiconductor elements from being electrically connected to each other.

Thereafter, the photoresist 6 is removed, and using the silicon nitride film 4 remaining in the element region portion 5 as a mask, the underlying polysilicon film 3 of the element isolation region portion 7 is oxidized to form a silicon oxide film 9 for element isolation. admonish.

Next, after removing the silicon nitride film 4 by wet processing with hot phosphoric acid or the like, the polysilicon film 3 in the element region 5 is removed using, for example, dry etching using Freon gas.
Furthermore, the base oxide thin film 2 is removed by etching using, for example, a 10% 0% fluorine aqueous solution. Then, the silicon substrate 1 in the element region portion 5 is exposed. In this way, element isolation is achieved.

[Problem to be solved by the invention]

However, in the conventional device isolation method, when forming the silicon oxide film 9 in the device isolation region portion 7, the ions 8 are diffused and the ion diffusion region 10 is formed. If, for example, a transistor is formed in such a state, there is a problem in that the width of the transistor is limited by the ion diffusion region 10.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a device isolation method in a semiconductor device that can suppress the spread of an ion diffusion region.

[Means to solve the problem]

In the element isolation method in a semiconductor device according to the present invention, the dimensions of the ion diffusion region are preliminarily reduced using a photomask, and the element isolation region portion is expanded after ion implantation.

[Effect]

In this invention, the dimensions of the ion diffusion region are reduced in advance using a photomask, and the element isolation region is expanded after ion implantation, which has the effect of reducing the width of the ion diffusion region. .

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1(a) to 1C) are cross-sectional views showing an element isolation method in a semiconductor device according to an embodiment of the present invention,
In the figure, the same reference numerals as in FIG. 2 indicate the same or corresponding parts, 11 is a photomask, and 12 is an element isolation width enlarged region.

First, a silicon oxide thin film 2, which is a base oxide thin film, is formed on a silicon substrate 1, and a polysilicon film 3 and a silicon nitride film 4 are formed thereon (each step is not shown).

Next, the element region portion 5 is masked with a photoresist 6, and the nitride film 4 in the element isolation region portion 7 is removed by etching. At this time, taking into consideration the expansion of the ion diffusion region 10, the dimensions of the element isolation region portion 7 are reduced using a photomask 11 (FIG. 1(a)).

Next, ions 8 for preventing inter-element parasitic channels are implanted into the element isolation region portion 7 from which the silicon nitride film 4 has been removed.

Then, using the photoresist 6 as a mask, the silicon nitride film 4 is etched by isotropic etching using Freon gas or the like to form an element isolation width enlarged region 12 (FIG. 1(b)).

After that, the photoresist 6 is removed (process diagram not shown),
Using the silicon nitride film 6 remaining in the element region portion 5 as a mask, the underlying polysilicon 3 in the element isolation region portion 7 is oxidized to form a silicon oxide film 9 for element isolation (FIG. 1(C)).

As described above, according to the element isolation method in a semiconductor device according to this embodiment, the ion diffusion region 10 is connected to the photomask 1.
1, its dimensions are reduced in advance, and the element isolation region portion 7 is expanded after the ions 8 are implanted, so that the width of the ion diffusion region 10 can be reduced.

〔Effect of the invention〕

As described above, according to the device isolation method in a semiconductor device according to the present invention, before ion implantation, the device isolation region is limited using a photomask, and then the device isolation region is etched and expanded. Therefore, even if the silicon oxide film for element isolation has the same dimensions as the conventional one, it is possible to obtain a semiconductor device in which the ion diffusion region is reduced.

[Brief explanation of drawings]

1(a) to 1C) are cross-sectional views of a semiconductor device for explaining one embodiment of the present invention, and FIGS. 2(a) to 2(b)
) is a cross-sectional view for explaining an element isolation method in a conventional semiconductor device. In the figure, 1 is a silicon substrate, 2 is a silicon oxide film,
3 is a polysilicon film, 4 is a silicon nitride film, 5 is an element region portion, 6 is a photoresist, 7 is an element isolation region portion,
Reference numeral 8 designates ions for preventing parasitic channels between elements, 9 a silicon oxide film for element isolation, 10 an ion diffusion region, 11 a photomask, and 12 an element isolation width expansion region. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In an element isolation method for semiconductor devices, field oxidation is achieved by injecting isolation into an etched region that has been reduced in advance using a photomask, and then performing isotropic etching until the opening in the nitride film reaches the designed dimensions. A method for isolating elements in a semiconductor device, characterized in that a separation width of a membrane and an isolation width are made to match.