JPH03155651A - Manufacturing method of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figures 3 to 6) Problems to be solved by the invention! Embodiments of Means and Effects for Solving LA (FIGS. 1 and 2) Effects of the Invention [Summary] Concerning a method of manufacturing a semiconductor device, more specifically, a method of forming a field oxide film and a channel stop region. A special field leakage current prevention impurity is used to prevent field leakage current from occurring between the source and drain of the transistor due to positive fixed charges generated in the field oxide film due to the incidence of radiation such as rLit. The purpose of this method is to form an oxidation-resistant film on a semiconductor substrate of one conductivity type, and then pattern the oxidation-resistant film. A step of implanting one conductivity type impurity for forming a channel stop into the surface of the semiconductor substrate using the oxidation-resistant film as a mask, and forming a field oxide film on the surface of the semiconductor substrate by thermal oxidation using the oxidation-resistant film as a mask. After forming a channel stop region directly under the oxide film and removing the oxidation-resistant film, controlled etching of the field oxide film is performed to remove the edge of the field oxide film to expose the surface of the channel stop region. The method includes the steps of partially exposing the region, and forming a transistor in a region surrounded by the field oxide film and the channel stop region.

[Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and more specifically, to a method of forming a field oxide film and a channel stop region.

[Conventional technology]

FIGS. 3(a) to 3(c) are explanatory diagrams of a first conventional method for manufacturing a semiconductor device.

First, as shown in FIG. 3(a), after forming a p-type Sii hypothetical i3Na film 2, the 5L3N4 film 2 is patterned, and then boron ions (Bo ) is injected into the surface of the St substrate 2. Next, using the 5ixN and film 2 as a mask, the St base it
When the surface is selectively thermally oxidized (selective oxidation method), thick 5y
An i- field 5i (h film 3) is formed, and at the same time a p-type channel stop region 4 is formed directly under the field 5ins film 3 (FIG. 3(b)).

Thereafter, after removing the SiJ film 2, a normal transistor forming process is performed, and as shown in FIG. 3(c), the gate 3toiWi5. A MOS transistor is formed having a poly-Si gate electrode 6 and source/drain regions 7.8.

Note that FIG. 4(a) is a top view of a MOS transistor manufactured by the first conventional manufacturing method, and in the figure, the sectional view taken along the line A-A corresponds to FIG. 4(b). B-
The sectional view taken in the direction of arrow B corresponds to the above-mentioned FIG. 3(c).

However, according to the first conventional method for manufacturing a semiconductor device, the following problem occurs.

That is, as shown in FIG. 4(c), radiation damage may occur in the field SiO□ film 3 due to the incidence of radiation such as γ rays, and positive fixed charges may be generated in the field Sing film 3. .

By the way, the p-type impurity concentration on the surface of the channel stop right page area 4 directly under the field 5iot14 is 1 compared to the substrate concentration.
Although the field SiO□ film is 5,000 to 6,000 thick, even though it is two orders of magnitude higher, a large number of fixed charges are generated and reversed. This charge remains semi-permanently even after the incidence of radiation has ended.

Therefore, as shown in FIG. 4(d), regardless of the state of the gate voltage, a leak current path is formed between the source and drain 7.8 through the n-type inverted portion, and the electrical characteristics of the transistor are affected. There is a problem of damage.

Therefore, in order to solve this problem, the second
A conventional method for manufacturing a semiconductor device has been proposed.

According to this method, first, as shown in FIG.
11 and p immediately below the field stomWA11.
A mold channel stop region 12 is formed.

Next, as shown in FIG. 2B, by implanting boron ions using the resist Fit3 as a mask, a highly concentrated p-type impurity region called a guard band 14 is formed along the edge of the field SiO□ film 11. Form.

Next, after forming a gate Si0g film 15 and a poly-Si gate electrode 16 (FIG. 1(c)), n-type impurities are ion-implanted using the resist film 17 and gate electrode 16 as masks to form source/drain regions 18, 19. is formed. ((d) in the same figure).

Next, the glabella insulation 11! of Si0g film etc. is made by CVD method. !
! 51, a window for source/drain electrode contact is opened (see (e) in the same figure), and a source/drain electrode contact window made of AI film is opened.
After forming the drain electrodes 52 and 53, the semiconductor device according to the conventional example is completed (FIG. 2(f)).

As described above, according to the second conventional manufacturing method, since the P-type guard band 14 is formed around the source/drain, even if the lower part of the field SiO□ film 11 is
Even if type inversion occurs, the guard band 14 prevents the n-type inversion region from being connected to the n-type source region 18 or the drain region 19. Thereby, it is possible to form a semiconductor device with good performance in which no leakage current occurs between the source and the drain.

[Problems to be Solved by the Invention] However, according to the method of manufacturing the semiconductor device of the second conventional example, as shown in the top view of the semiconductor device of the second conventional example, the source/drain Since the guard band 14 is formed between the region 18, 19 and the field SiO□ film 11, the area for forming the semiconductor device becomes large corresponding to the area of the guard band, and there is a problem that integration is impaired.

The present invention was created in view of such conventional problems, and the field leakage current between the source and drain of the transistor is caused by the positive fixed charge generated in the field oxide film due to the incidence of radiation such as gamma rays. An object of the present invention is to provide a method for manufacturing a semiconductor device that can easily prevent the occurrence of channel leakage current without forming a special impurity region for preventing channel leakage current.

(Means for Solving ill!i) The method for manufacturing a semiconductor device of the present invention includes a step of forming an oxidation-resistant film on a -conductivity type semiconductor substrate, and then patterning the oxidation-resistant film; A process of implanting one conductivity type impurity for forming a channel stop into the semiconductor substrate surface using a patterned oxidation-resistant film as a mask, and thermal oxidation.
A step of forming a field oxide film on the surface of the semiconductor substrate using the oxidation-resistant gland as a mask, and forming a channel stop region directly under the field oxide film, and after removing the oxidation-resistant film, controlled etching of the field oxide film. a step of partially exposing the surface of the channel stop region by removing an end of the field oxide film; and a step of forming a transistor in a region surrounded by the field oxide film and the channel stop region. The above-mentioned item J is achieved.

[Operation] According to the present invention, controlled etching of a field oxide film formed by a selective oxidation method is performed.

The amount of controlled etching at this time is determined so that it ends when the edge of the field oxide film is removed and a channel stop region with a relatively high impurity concentration appears.

This creates a state ζ2 which is essentially the same as if a guard band with a high impurity concentration not covered by the field oxide film was formed inside the field oxide film.

Therefore, even if positive fixed charges are generated in the field oxide film by γ rays, etc., the substantial guard band prevents the formation of a leakage current path between the source and drain of a MOS transistor, for example. can.

Further, according to the manufacturing method of the present invention, there is no need to form an impurity region for preventing channel leakage, so the number of manufacturing steps can be reduced, and the formation area does not increase, making it possible to improve the performance of semiconductor devices. Integration is not impaired.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A to 1H are diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.

First, the impurity concentration I x 101s/cta' (DS
The surface of the i3 temporary 20 is thinly thermally oxidized and siogW (not shown) is applied.
After forming the 5rsNa film 21, an oxidation-resistant film 9, for example, 5isN411121, with a thickness of 1,500 is formed by the CVD method, and then, after patterning the 5iJa film 21, boron (B'') is ion-implanted using the 5rsNa film 21 as a mask. (
Figure (a)).

Next, wet oxidation was performed at an oxidation temperature of 900°C to form a 5tJa film 2.
Using 1 as a mask, show a field with a film thickness of 0.6 μm□
A film 22 is selectively formed (FIG. 2(b)).

The boron ions implanted at this time are also activated by heat treatment, and a channel stop region 23 having a surface concentration of 1 x 10'1/am' is formed. However, field 5 (channel stop region 23 directly under the edge of 01 film 22)
The surface concentration of is quite low because it is at the edge of the impurity diffusion distribution.

Next, after removing the Si3N4 film 21, 10% IF
Performing controlled etching of the field 5tOt film 22 approximately 0.1 to 0.2 μm from the surface using an aqueous solution.
As a result, the edge of the field 5102M122 with a thin film thickness is removed, and the edge of the field Si0g film 22 becomes 0.
．． It retreats by about 3 to 0.5 μm. As a result, the high surface concentration portion of the channel stop region 23 is exposed (
Figure (c)).

Next, a gate SiO□ film is formed by thermal oxidation, and polysit! is formed by CVD. After forming the poly 5tlI5! using a resist film (not shown) as a mask, and gate S
iO! Pattern the film and gate 510g1i 24
and a poly-Si gate electrode 25 (FIG. (d)).
).

Next, the patterned resist film 26 and polyS
Using the i-gate electrode 25 as a mask, phosphorus (P') is ion-implanted to form an n-type source region 27 and drain region 28 (FIG. 4(e)).

Next, a glabellar insulating film 29 such as a PSG film or a 5iOz film is formed by the CVD method (FIG. 6(r)).

After that, the glabellar insulating film 29 is patterned and the source
Openings 30.degree. 31 for drain electrode contacts are formed (FIG. 3(g)).

Next, after forming ^1119, the A1 film is patterned to form a source electrode 32 and a drain electrode 33, completing the semiconductor device of the present invention ((h) in the same figure).
.

FIG. 2 is a top view of a semiconductor device according to an embodiment of the present invention. Note that the source/drain electrodes 32 and 33 and the glabella insulation M29 are omitted to make the explanation easier to understand.

As described above, according to the method of manufacturing a semiconductor device according to the embodiment of the present invention, as shown in FIG. 1(d), the field stow) I! The end portions of the field SiO□ film 22 are removed by etching so that the channel-stensive region 23 with a high surface concentration comes out from the field SiO□ film 22. Therefore, this exposed channel stop region 23 with high surface concentration functions substantially like a guard band, and even if radiation such as γ-rays is incident, the field sio, l! ! ! Even if positive fixed charges are generated in the source and drain regions 27 and 22, it is possible to prevent leakage current from occurring between the source and drain regions 27 and 28.

Further, in the present invention, there is no need to specially form a guard band for preventing leakage current as in the conventional example, so the process is greatly simplified and the area of the transistor forming region does not increase.

Therefore, it is possible to improve the yield of non-defective devices and the integration.

〔Effect of the invention〕

As explained above, according to the present invention, the edge of the field oxide film is etched away by controlled etching, the edge of the field oxide film is retreated, and the impurity concentration is substantially reduced to the outside of the field oxide film. This creates a state where a high guard band is formed.

Therefore, even if positive fixed charges are generated in the field oxide film due to the incidence of radiation such as γ-rays, the substantial guard band prevents leakage current from occurring between the source and drain of the transistor. becomes possible.

In addition, in the present invention, unlike the conventional example, there is no need to specifically form a guard band for preventing leakage current, so the process is greatly simplified and the area of the transistor formation region does not increase9. Therefore, it is possible to improve the yield of non-defective devices and the integration.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a top view of a semiconductor device according to an embodiment of the present invention, and FIG. 3 is a diagram of a first conventional example. An explanatory diagram of a method for manufacturing a semiconductor device, FIG. 4 is an explanatory diagram of problems in the first conventional example, and FIG.
FIG. 6 is a top view of the semiconductor device according to the second conventional example. (Explanation of symbols) 20...Si-based Vi (-conductivity type semiconductor substrate), 21
...Si3N, film (oxidation resistance It), 22...Field 5t (h film, 23...Channel stop region, 24...Gate Sio*M%25...Poly-Si gate electrode, 27...Source region, 2B...Drain as a member ring.

Claims (1)

[Claims] A step of forming an oxidation-resistant film on a semiconductor substrate of one conductivity type and then patterning the oxidation-resistant film, and using the patterned oxidation-resistant film as a mask to form a channel on the surface of the semiconductor substrate. A step of implanting one conductivity type impurity for forming a stop, and forming a field oxide film on the surface of the semiconductor substrate by thermal oxidation using the oxidation-resistant film as a mask, and forming a channel stop region directly under the field oxide film. After removing the oxidation-resistant film, control etching is performed on the field oxide film to remove an edge of the field oxide film to partially expose the surface of the channel stop region; 1. A semiconductor device comprising: forming a transistor in a region surrounded by an oxide film and a channel stop region.