JPS63300526A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate the etching of a substrate and to prevent the characteristics of a semiconductor device from being deteriorated by relatively increasing the etching selection ratio of a second semiconductor oxide film to a first anti-oxide film to form a semiconductor layer between a first semiconductor oxide film and the first anti-oxide film on the substrate. CONSTITUTION:A thin first semiconductor oxide film 2, a semiconductor layer 3, a first anti-oxide film 4 and a second semiconductor oxide film 5 are sequentially formed on a silicon substrate 1. A resist 12 is selectively formed thereon, the films 5, 4 are selectively etched by RIE in such a manner that the film 4 is effectively removed slightly by overetching. With the film 5 as a mask P-type impurity is ion implanted through the layer 3 and the film 2 into the substrate 1. Then, an etching remainder 9 is formed on a sidewall 8 by anisotropically etching by RIE the film 6 formed on its whole surface, and with the film 4 and the remainder 9 as masks the substrate 1 is selectively thermally etched to form a field SiO2 film 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device. INDUSTRIAL APPLICATION This invention can be used suitably, for example when forming element bone Ma regions, such as VLSI.

[Summary of the invention]

The present invention sequentially forms a first semiconductor oxide film, a semiconductor layer, a first oxidation-resistant film, and a second semiconductor oxide film on a semiconductor substrate, and selects the second semiconductor oxide film and the oxidation-resistant film. impurities are introduced into the semiconductor substrate using the second semiconductor oxide film as a mask, a second oxidation-resistant film is formed on the entire surface, and the second oxidation-resistant film is anisotropically etched. By forming an etching residue on the sidewall portion, removing the second semiconductor oxide film, and selectively oxidizing the substrate using the oxidation-resistant film as a mask, fine and good characteristics can be obtained in a semiconductor device. This makes it possible to form an element isolation region provided with the structure.

[Conventional technology]

Conventional methods for manufacturing semiconductor devices, such as methods for forming element isolation regions in semiconductor devices, include LOCO, which has been conventionally performed.
Although there are three methods, miniaturization of the element isolation region is not easy due to the occurrence of bird's beaks.

FIG. 2 is a semiconductor cross-sectional view showing a conventional method for manufacturing a semiconductor device, in which (a) is a cross-sectional view when silicon nitride is formed, and (b) is a cross-sectional view when sidewalls are formed.
As shown in the same figure (a), SiO2 is placed on the silicon substrate 21
Film 22 + Si3N4 film 23 (in the case described later, S
After sequentially depositing the iO□ film 24), the Si and N4 films 23 in the region where element isolation is to be formed are selectively removed (along with the SiO□ film 24 in the case described later). By inserting a step in which silicon nitride (SiJ4) is deposited on the entire surface by CVD and anisotropically etched, the side wall 27 of the recess 26 is formed as shown in FIG. 2(b).
A side wall 26' is formed in the portion to suppress the occurrence of bird's beak and to miniaturize the element isolation region.

[Problem that the invention seeks to solve]

As mentioned above, silicon nitride (
According to the conventional method of forming an element isolation region by forming a side wall 26' of SiJ4), etc.,
), CV of silicon nitride (SiJa)
After D, when etching the entire surface with RIB etc.
Since it is difficult to obtain a selectivity with respect to the NG film 22, there is a possibility that even the silicon substrate 21 is etched and the substrate is exposed. If you hit the board 21 directly with RIH like this,
There is a risk of damaging the substrate and deteriorating device characteristics.

Furthermore, if the substrate is exposed, large bird's beaks may appear during selective oxidation to form element isolation regions, which is a problem.

Also, silicon nitride (
Since the film thickness of the Sing film 22 shown by arrow A below the side wall 26' of SisNa) is reduced, stress is caused by the silicon substrate 21 and the side wall (st3N4) 26'' during selective oxidation to form an element isolation region. There is a problem that crystal defects may occur.

Furthermore, when forming an element isolation region, channel stop ions are implanted at -a to increase the impurity concentration under the element isolation region, but if the acceleration voltage of ion implantation is large, the ions will selectively oxidize ( For example 5i3N4
) and reach the element formation region, causing a problem of changing device characteristics. Therefore, as shown in FIG. 2(a), it is conceivable to form 5iOtrPA 24 on the 5iJ4 film 23 to increase the film thickness on the element formation region. However, when trying to apply this to the conventional LOCOS method, the RIH of the 5isNa film 23 and the Sing film 24
The selection ratio of etching is small, and the
Since the film 22 and the film 22 have the same etching selectivity, there is a problem that the etching processability is poor.

The present invention has been created in view of the above-mentioned problems, and an object of the present invention is to manufacture element bone NS by the above-described conventional manufacturing method.
It is an object of the present invention to provide a method for manufacturing a semiconductor device that can solve problems arising from the formation of the R region.

[Means for solving problems]

In order to solve the above problems, the present invention includes a step of forming a first semiconductor oxide film on a semiconductor substrate, a step of forming a semiconductor layer on the semiconductor oxide film, and a step of forming a first acid-resistant film on the semiconductor layer. a step of forming a second semiconductor oxide film on the oxidation-resistant film; a step of selectively etching away the second semiconductor oxide film and the oxidation-resistant film; A step of introducing impurities into the semiconductor substrate using the second semiconductor oxide film as a mask, a step of forming a second oxidation resistant film on the entire surface, and anisotropic etching of the second oxidation resistant film to remove sidewall portions. A method is adopted which includes a step of forming an etching residue on the substrate, a step of removing the second semiconductor oxide film, and a step of selectively oxidizing the substrate using the oxidation-resistant film as a mask.

Hereinafter, a method for manufacturing a semiconductor device according to the present invention will be described with reference to FIGS.
f) Explain with reference to (g).

The method for manufacturing a semiconductor device of the present invention is the PPL method (Poly Pad Locos method), which is an improved version of the LOCO3 method for forming element isolation regions and was filed by the same applicant as the present application.

This is a further improvement based on the patent application No. 59-T9S3OIT.

As shown in FIG. 1(a), the method for manufacturing a semiconductor device according to the present invention includes a method for manufacturing a semiconductor device on a semiconductor substrate 1 made of, for example, p-type silicon.
A semiconductor oxide film (for example, SiO□) 2 is formed, a semiconductor layer (for example, polysilicon) 3 is formed on the semiconductor oxide film 2, and a first oxidation-resistant film (for example, 5iJ) is formed on the semiconductor layer 3.
n) 4 is formed, a second semiconductor oxide film (for example, Sing) 5 is formed on the oxidation-resistant film 4, and a resist 1 is formed on it.
2 is selectively formed.

As shown in FIG. 1 (Ql+), the second semiconductor oxide film 5 and the first oxidation-resistant film 4 are selectively etched away using RIB or the like, and the second semiconductor oxide film 5 is used as a mask to remove the An impurity (for example, boron B) 7 is implanted into the semiconductor substrate 1 using ion implantation silane or the like (the implanted impurity is represented by a black dot in the figure).

Next, as shown in Fig. 1 (tc), a second oxidation-resistant film (
For example, 5i3N4) 6 is formed, and the second oxidation-resistant film 6 is subjected to anisotropic etching such as RIB to form etching residues 9 on the sidewall portions 8, as shown in FIG. 1(d).

This is because the second oxidation-resistant film 6 is etched at a constant speed in the etching direction, so that etching remains (also called sidewalls) are left on the sidewall portions where the film is thick.

As shown in FIG. 1(e), the second semiconductor oxide film 6 is removed using a hydrochloric acid solution or the like.

As shown in FIG. 1(f), by selectively thermally oxidizing the substrate 1 using the first oxidation-resistant film 4 and the etching residue 9 as a mask, the semiconductor substrate 1 is coated with Sin and the film 1.
0 (also called field SiO□ film) is formed.

As shown in FIG. 1(g), the first semiconductor oxide film,
Semiconductor layer 3, first oxidation resistant film 4 and etching residue 9
is removed by an appropriate means (for example, by oxidation and etching, or by using a hydrochloric acid solution, a phosphoric acid solution, etc.) to form an element region m1911.

Note that the impurity 7 implanted into the semiconductor substrate 1 is electrically activated during thermal oxidation and is also diffused in the depth direction, so if boron ions are used below the 5iOt film 10, p''' type channel stopper 11 is formed.

The thickness of the first semiconductor oxide film 2 is thin (by forming the first semiconductor oxide film 2, the occurrence of bird's beak can be suppressed to a small level.

For example, it can be preferably formed to be as thin as about 50 people.

The material of the second semiconductor oxide film 5 is desirably one that can maintain an etching selectivity in relation to the first oxidation-resistant film 4 before selective oxidation, and that can serve as a mask during ion implantation.

It is desirable that the semiconductor layer 3 serves as a stopper that can maintain a selectivity when selectively etching away the second semiconductor oxide film 5 and the first oxidation-resistant film 4. For example, polysilicon or the like can be preferably used.

[Effect]

As described above, in the present invention, in order to form a semiconductor layer between the first semiconductor oxide film and the first oxidation-resistant film on the semiconductor substrate, the second semiconductor oxide film and the first oxidation-resistant film In the process of selectively removing the film by etching, a relatively high etching selectivity can be achieved, which prevents the semiconductor substrate from being etched and hitting the substrate (which prevents deterioration of device characteristics. can do.

Furthermore, since impurities can be selectively introduced into the semiconductor substrate using the second semiconductor oxide film as a mask, impurities can be reliably introduced into desired positions and desired device characteristics can be obtained.

In addition, by forming a second oxidation-resistant film on the entire surface and anisotropically etching the second oxidation-resistant film to form etching residues on the sidewalls, for example, the element isolation region shown in FIG. 1(b) can be formed. Even if the width W is the limit width due to the wavelength of photolithography, as shown in FIG. Since the width of the isolation region can be reduced by the width W'x2, the integration of the semiconductor device can be increased.

〔Example〕

Hereinafter, a first embodiment of the method for manufacturing a semiconductor device of the present invention will be described.
This will be explained in detail with reference to the drawings. It should be noted that, as a matter of course, the following example shows an example of the present invention, and the present invention is not limited only to this example.

FIGS. 1(a) to 1(g) are cross-sectional views showing the manufacturing process of the semiconductor device of this embodiment.

In this embodiment, as shown in FIG.
A p-type silicon substrate is used, and the substrate surface is thermally oxidized to form an extremely thin first semiconductor oxide film (here, S
A semiconductor layer (polysilicon in this case) 3 with a thickness of 500 and a first oxidation-resistant film (in this case with a thickness of 1000) are formed on the first semiconductor oxide film 2 by CVD. 5isNn) 4 is formed, and a second semiconductor oxide film (here Sing) is formed on the oxidation-resistant film 4.
5 to form, for example, 500 people.

Then, a resist 12 is selectively formed on the semiconductor oxide film 5.

As shown in FIG. 1(b), the second semiconductor oxide film 5 and the first oxidation-resistant film 4 are selectively etched away by RIB. In this case, the first oxidation-resistant film 4 is surely removed with a slight overetching. Then, using the second semiconductor oxide film 5 as a mask, a p-type impurity, such as boron (B) 7, is implanted into the semiconductor substrate l using an ion implantation method to form the semiconductor layer 3 and the first semiconductor oxide film. Ions are implanted into the semiconductor substrate 1 through 2 (injected impurities are represented by black dots in the figure).

Next, as shown in Figure 1 (01), a second oxidation-resistant film (
Here, 5iaNe) 6 is formed, and as shown in FIG. 1(d), the second oxidation-resistant film 6 is anisotropically etched by RIE to form etching residues 9 on the sidewall portions 8.

Next, as shown in FIG. 1(e), the second semiconductor oxide film 6 is removed using a hydrofluoric acid solution.

As shown in FIG. 1(f), by selectively thermally oxidizing the substrate 1 using the first oxidation-resistant film 4 and the etching residue 9 as a mask, a SiO□ film 1 is formed on the semiconductor substrate 1.
0 (also called field 5ift film) is formed.

Then, as shown in FIG. 1(g), the first semiconductor oxide film is wet-etched with a hydrofluoric acid solution, and the first oxidation-resistant film 4 is etched.
The etched residue 9 is wet-etched with a phosphoric acid solution, and the semiconductor layer 3 is oxidized and removed by etching to form an element isolation region.

The N regions obtained by the method of this example have a layer structure that allows for etching selectivity, so that the substrate is not hit by etching, stable device characteristics are obtained, and impurities are not introduced into the semiconductor substrate. Since it is possible to reliably insert the semiconductor device into a desired position, desired device characteristics can be obtained, and furthermore, by reducing the width of the element isolation region, it is possible to increase the integration of the semiconductor device.

〔Effect of the invention〕

As described above, by using the semiconductor device manufacturing method of the present invention, stable and desired device characteristics can be obtained, and by miniaturizing the width of the element isolation region, it is possible to increase the integration of the semiconductor device. It became.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(a) are cross-sectional views showing the manufacturing process of the semiconductor device of this embodiment. FIG. A cross-sectional view when forming a ride, and (b) a cross-sectional view when forming a sidewall. 1... Semiconductor substrate, 2... First semiconductor oxide film, 3... ...semiconductor layer, 4...
・First oxidation-resistant film, 5... Second semiconductor oxide film, 6... Second oxidation-resistant film, 7... Impurity, 8... ...Side wall, 9...Etching remaining.

Claims (1)

[Claims] A step of forming a first semiconductor oxide film on a semiconductor substrate, a step of forming a semiconductor layer on the semiconductor oxide film, and a step of forming a first oxidation-resistant film on the semiconductor layer. a step of forming a second semiconductor oxide film on the oxidation-resistant film; a step of selectively etching away the second semiconductor oxide film and the oxidation-resistant film; and the second semiconductor oxide film. a step of introducing impurities into the semiconductor substrate using a mask as a mask, a step of forming a second oxidation-resistant film on the entire surface, and anisotropic etching of the second oxidation-resistant film to form an etching residue on the sidewall portion. a step of removing the second semiconductor oxide film; and a step of selectively oxidizing the substrate using the oxidation-resistant film as a mask.