JPH04105346A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the formation of a bird beak so as to obtain a semiconductor device suitable for face of a silicon film facing the side face of an element separating insulating film and one main surface of a silicon semiconductor substrate at the outer peripheral surface of the element separating insulating film and growing the element separating insulating film by oxidation by using the second insulating film formed on the exposed side face and one main surface as a mask. CONSTITUTION:After a silicon film 3 is formed on one main surface of a silicon semiconductor substrate 1, the first insulating film 4 is selectively formed on the silicon film 3 and an element separating insulating film 7 is formed by oxidizing the silicon film 3 and one main surface of the substrate 1 by using the insulating film 4 as a mask. Then the side face of the silicon film 3 facing the insulating film 7 and one main surface of the substrate 1 on the outer periphery of the insulating film 7 are exposed by etching the surface of the insulating film 7. Thereafter, the insulating film 7 is grown by oxidation by using the first and second insulating films 7 and 9 as a mask after the second insulating film 9 is formed on the above-mentioned exposed side face of the silicon film 3 and one main surface of the substrate 1.

Description

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

[Conventional technology]

In recent years, there has been a demand for the establishment of miniaturization technology for semiconductor integrated circuit devices as speed increases and integration increases.

One of the important items in this microtechnology is the reduction of the element isolation region that separates a plurality of MO5 field effect transistors (hereinafter abbreviated as MQ5FET) constituting a semiconductor integrated circuit device. Particularly in large-capacity memories, the dimensions of the element isolation region are a major factor in determining the memory cell size, and in the case of logic L5I, proportional reduction of the element isolation region is indispensable when proportionally reducing the entire chip pattern.

As an element isolation technology, after buttering the nitride film,
L selectively oxidizes only the silicon around the nitride film
OCO5 (Loell Qxidlton of 5i
1icon) There is a law.

A method of manufacturing an element isolation insulating film using the LOCO5 method will be described with reference to FIGS. 2(a) to 2(f).

First, as shown in FIG. 2(a), the concentration is 5×1014~
5X 10" txt-3, specific resistance full ~80!
1 ('I (7) P-type silicon IJ ': J A 200 to 500 thick underlayer oxide layer (2) is formed on the main surface of the semiconductor substrate (W) by a thermal oxidation method. Relaxing the stress of the silicon nitride film that will be formed in a later process,
This is to suppress the occurrence of dislocations and slips within the P-type silicon semiconductor substrate (6).

Next, as shown in FIG. 2(b), a silicon nitride film having a thickness of 100 to 8000 Å is deposited on the surface of the underlying oxide film (6) by the CVD method.

Next, as shown in FIG. 2(C), a silicon nitride film (2
), and the photoresist (b) is patterned by photolithography so as to remove the pattern on the region where the element isolation insulating film is to be formed. Subsequently, the silicon nitride film is etched using the photoresist (b) as a mask.

Next, as shown in FIG. 2(d), using the silicon nitride film @ and the photoresist (b) as a mask, accelerate Voltage 40-70 KeV, dose I x 101
Boron ion implantation was performed under 3”-”(7) conditions,
A throat-type high concentration layer (up to) with a concentration of ~10"tll"-3 is formed. This t-type high concentration layer cIFj will be formed in a later step.
This is a channel stopper that prevents the formation of a parasitic channel under the field oxide film.

Next, as shown in FIG. 2(,), after removing the photoresist (b) pattern, thermal oxidation is performed at a temperature of 900 to 1000 DEG C. using the silicon nitride film (to) as a mask. At this time, only the region not covered with the silicon nitride film is oxidized, and the film is used as a Flip edge film for the element (
A field oxide film (c) of 5,000 to 6,000 layers is formed.

Next, as shown in FIG. 2(f), a silicon nitride film μs
, and the underlying oxide film @ are removed in order, the negative main surface of the P-type silicon semiconductor substrate (6) is exposed only in the element formation region. Thereafter, an n-channel MO5FET is formed in the -main surface of the exposed P-type silicon semiconductor substrate (b) using a normal MQ5Ffil:T manufacturing technique.

[Problem to be solved by the invention]

In the conventional manufacturing method of the field oxide film as described above, the field oxide film sinks into the bottom of both ends of the silicon nitride film, resulting in a bird's beak-shaped oxide film called a perspective peak. Formed.

Here, a perth beak with a length t3 (5,000 to 6,000 layers) approximately equal to the thickness of the field oxide film is formed, expanding the area of the field oxide film and reducing the device formation area. Therefore, there was a problem of hindering miniaturization.

This invention was made to solve the above-mentioned problems, and aims to suppress the formation of perspective peaks and obtain a semiconductor device suitable for miniaturization.

[Means to solve the problem]

In the method for manufacturing a semiconductor device according to the present invention, a first insulating film selectively formed on a silicon film formed on a silicon semiconductor substrate is used as a mask to oxidize the silicon film and one main surface of the silicon semiconductor substrate. After forming the element isolation insulating film, the surface of the element isolation insulating film is etched to remove the side surface of the silicon film facing the side surface of the element isolation insulating film and the outer periphery of the element isolation insulating film. The second insulating film and the first insulating film formed on the side 1 of this silicon film and one side of the silicon semiconductor substrate are used as masks to expose the surface of the silicon semiconductor substrate. This method grows an insulating film by oxidation.

[Effect]

In the method for manufacturing a semiconductor device as described above, the insulating film formed on the side surfaces of the exposed silicon film and the seven sides of the exposed silicon semiconductor substrate suppresses the lateral growth and oxidation of the element isolation insulating film. , suppresses the formation of perspective peaks.

〔Example〕

FIGS. 1(a) to 1(j) are cross-sectional views showing a manufacturing method according to an embodiment of the present invention.

First, as shown in FIG. 1(a), the concentration of
X10''Cl11-3. An underlayer oxide film (2) of about 500 yen is formed by a thermal oxidation method on the main surface of a P-type silicon semiconductor substrate (1) having a specific resistance of 8 to +10 fi.

Next, as shown in FIG. 1(b), a silicon film with a thickness of 500 to 1000 layers is deposited on the surface of the underlying oxide film (2) by CVD. l (38 First insulating film with a film thickness of 500 to 200 mm)
Silicon nitride A (4), which becomes a first insulating film of 0A, is laminated in order. In order to form a silicon nitride film sidewall in a later step, it is necessary to increase the step from the -main surface of the P-type silicon semiconductor substrate (1). Here, silicon film (
3) provides a level difference.

Next, as shown in FIG.
), and the photoresist (5) is patterned by photolithography so as to remove the pattern on the region where the element isolation insulating film is to be formed. Subsequently, the silicon nitride film (4) is etched using the photoresist (5) as a mask.

Next, as shown in FIG. 1(d), a silicon nitride film (4
) and photoresist (5) as a mask from above the silicon film (3) to the negative main surface of the P-type silicon semiconductor substrate (1) at an acceleration voltage of 40 to 70 KeV and a dose of I
Boron f-on implantation was performed under the conditions of 1g13~5 x 10IacII-", and the concentration was ~10"cIll-"
A P+ type high concentration layer (6) is formed. This P+ type high concentration layer (6) serves as a channel stopper for preventing the formation of a parasitic channel under the field face film formed in a later step.

Next, as shown in No. 11'3 is), after removing the pattern of photoresist (5), silicon nitride PA (4) is removed.
) is used as a mask to perform thermal oxidation at a temperature of 900 to 1000°C. At this time, the silicon group (3) located in the region not covered with the silicon nitride film (4) and the P-type silicon semiconductor substrate (
1) is oxidized, and field oxidation &14 (7) is formed as an element isolation insulating film.

Next, as shown in FIG. 1(f), the surface of the field oxide film (7) is etched using a mixed solution of ammonium fluoride (NH,F) and hydrofluoric acid (HF). The - main surface and field oxide film (7) of the P-type silicon semiconductor substrate (1) located on the side surface of the silicon film (3> opposite to the side surface of 7), the outer periphery of the P+ type high concentration layer (6)
The inner circumferential surface of the P+ type high concentration layer (6) facing the side surface of the P+ type high concentration layer (6) is exposed.

Next, as shown in FIG. 1-), a silicon nitride film (8) is formed over the entire -main surface of the P-type silicon semiconductor substrate (1).

Next, as shown in FIG. 1(h), a silicon nitride film (8
) is subjected to reactive ion etching (mainly anisotropic), the silicon nitride film (
4) side surface, the side surface of the silicon film (3) opposite to the side surface of field oxidation@(7), the -main surface of the P-type silicon semiconductor substrate (1) located on the outer periphery of the P"aAi concentration layer (6), and A silicon nitride film (8) remains covering the inner peripheral surface of the P+ type high concentration layer (6) facing the side surface of the field oxide @ (7), and a silicon nitride film (8) is formed on the side wall of the silicon nitride film as a second insulating film. Sanru.

Next, as shown in FIG. 1(i), a silicon nitride film (4
) and the silicon nitride film sidewall (9) as a mask.
Thermal oxidation is carried out at a temperature of ~tooo<0>C. At this time, the field oxidation errors (7) will grow to 5000 to 6000 people.

Next, as shown in FIG. 1U), a silicon nitride film (4) is formed.
When the silicon nitride film sidewall (j), silicon film (3), and underlying oxide film (2) are removed in this order, the negative main surface of the P-type silicon semiconductor substrate (1) is exposed only in the element formation region.

Thereafter, an n-channel MO5FET is formed in the -main surface of the exposed P-type silicon semiconductor substrate (1) using a normal MOSFET manufacturing technique.

The field oxide film (
In the manufacturing method 7), after etching the surface of the field oxide film (7), from the silicon nitride film (4) toward the field oxide film (7), the silicon nitride m side! ! (9
) is formed and thermal oxidation is performed using the silicon nitride film sidewall (9) and silicon nitride film (4) as a mask, so that rII
It becomes difficult for elements to diffuse into the lower part of the silicon nitride film (4),
The oxide film in the lateral direction is suppressed. Therefore, the film thickness to
(5,000 to 6,000 people), the length of the field oxide film (7) that goes into the bottom of the silicon nitride film sidewall (9) is suppressed to 11 (toooo version). The device formation area is increased by suppressing the area expansion of the image (7). Therefore, a semiconductor device suitable for miniaturization can be obtained.

In the above embodiment, boron was implanted into the main surface of the P-type silicon semiconductor substrate (1) in order to prevent the formation of a parasitic channel, but instead of boron, a group III element such as aluminum or gallium was implanted. Even if f is injected, the same effect as in the above embodiment can be obtained.

Further, in Example 8 above, the field deposition film (7) was formed on the P-type silicon semiconductor substrate (1), but instead of the P-type silicon semiconductor substrate (1), an n-type silicon semiconductor substrate (1) was formed. Even if a silicon semiconductor substrate is used and a field oxide film is formed on an n-type silicon semiconductor substrate, the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, the present invention uses the first insulating film selectively formed on the silicon film formed on the silicon semiconductor substrate as a mask to oxidize the entire surface of the silicon film and the silicon semiconductor substrate. After forming the isolation insulating film, the surface of the element isolation insulating film is etched to expose the side surface of the silicon film facing the side surface of the element isolation insulating film and the entire surface of the silicon semiconductor substrate at the outer periphery of the element isolation insulating film. Since the device isolation insulating film was oxidized and grown using the second insulating film and the first insulating film formed on the side surface of the silicon film and the entire surface of the silicon semiconductor substrate as a mask, the lower part of the end of the insulating film was grown by oxidation. This has the effect of suppressing the formation of bird's peaks caused by the #+1 heat, thereby making it possible to obtain a semiconductor device suitable for miniaturization.

[Brief explanation of drawings]

FIGS. 1(a) to 1(j) are cross-sectional views sequentially showing an embodiment of the present invention in the order of steps, and FIGS. 2(a) to 2(f) are sectional views showing the conventional manufacturing of an element isolation insulating film. It is sectional drawing which shows a process one by one. In the figure, (1) is a P-type silicon semiconductor substrate, (3)
(4) is a silicon film, (4) is a silicon nitride film, (y) is a field oxide film, (September 2) is a silicon nitride film sidewall, and α1 is a bird's peak. In each figure, the same reference numerals indicate the same or equivalent parts. shows.

Claims (1)

[Claims] A step of forming a silicon film on one main surface of a silicon semiconductor substrate, a step of selectively forming a first insulating film on this silicon film, and a step of oxidizing the silicon film using this first insulating film as a mask. a step of oxidizing one main surface of the silicon semiconductor substrate to form an element isolation insulating film; etching the surface of the element isolation insulating film to expose a side surface of the silicon film opposite to a side surface of the element isolation insulating film; a step of exposing one main surface of the silicon semiconductor substrate at the outer periphery of an element isolation insulating film; a step of forming a second insulating film on the side surface of the exposed silicon film and the exposed one main surface of the silicon semiconductor substrate; A method for manufacturing a semiconductor device, comprising the step of growing the element isolation insulating film by oxidation using the first insulating film and the second insulating film as masks.