JPH02268434A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the growth of the protrusion on the second oxide film by forming a conductor film and an oxidation-resistant film in a nonoxidizing atmosphere on the first oxide film formed on a semiconductor substrate, removing the oxidation-resistant film on an element isolation intended area, and forming the second oxide film. CONSTITUTION:A silicon oxide film 102 is formed on a silicon substrate 101 being a semiconductor substrate. And, a polycrystalline silicon film 103 and a silicon nitride film 105 are formed on the silicon oxide film 102 in a nonoxidizing atmosphere. Then, the silicon nitride film 105 in an element isolation and formation intended area is selectively removed, and a field oxide film 106 is formed as the element isolation area in a part 109 where the silicon nitride film 105 was selectively removed. After forming the field oxide film 106, the silicon nitride film 105 and polycrystalline silicon film 103 having become unnecessary are removed. Then, by removing the unnecessary silicon oxide film 102 after oxidizing the surface of the silicon substrate 101, the formation of the field oxide film 106 finishes. In this way, the growth of the protrusion on the field oxide film 106 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device in element isolation.

(Prior Art) Each element constituting a semiconductor device is generally insulated and isolated by a thick field oxide film. Recently, progress has been made to miniaturize field oxide films in order to increase the integration density of semiconductor devices, and in order to miniaturize field oxide films, selective oxidation as shown in FIGS. 4(a) to (g) is being carried out. law is used.

First, a silicon oxide film (202) is formed on the surface of a silicon substrate (201) by thermal oxidation, and then a polycrystalline silicon film (203) is formed on the film by CVD (Chesle).
It is deposited by the alVapor Deposltlon method. After depositing the polycrystalline silicon film (203),
The substrate is transferred from the reaction tube to another reaction tube for the next step. At this time, since the surface of the polycrystalline silicon film (203) is exposed to the atmosphere, a very thin natural oxide film (204) of about 10 to 30 layers is usually formed on the surface of the polycrystalline silicon film (203). Figure (a)).

A natural oxide film (203) is formed on this polycrystalline silicon film (203).
4), a silicon nitride film (205) is deposited by the CVD method (FIG. 4(b)).

The silicon nitride film (205) in the region where element isolation is to be formed is removed by etching using a resist pattern (not shown) as a mask (FIG. 4(C)).

Subsequently, a field oxide film (208) with a thickness of 5,000 wafers is formed as an element isolation region by thermal oxidation on the portion (209) (shown in FIG. 4(e)) where the silicon nitride film (205) has been selectively removed. (Figure 4(d)).

After field oxidation 5 (2H) is formed, the unnecessary silicon nitride film and polycrystalline silicon film are simultaneously removed by etching (FIG. 4(e)).

Next, the silicon substrate (201) is oxidized by thermal oxidation to form a field oxide film (20B) and a silicon oxide film (
202) is formed to be even thicker (FIG. 4(r)).

When forming the field oxide film (20B), H2O generated by reaction during oxidation and the silicon nitride film (20B) are mixed together.
5) reacts to form ammonia, and this ammonia reacts with the surface of the silicon substrate to form nitride, thereby lowering the breakdown voltage of the gate oxide film to be formed on the silicon substrate (201) in the next step.

For this purpose, the surface of the silicon substrate (201) is oxidized, and in the next step, the unnecessary oxide film and nitride are removed by etching.

After oxidizing the surface of the silicon substrate (201), unnecessary silicon oxide film (202) (shown in FIG. 4(r)) is removed by etching to complete the field oxide film (20B) forming process (FIG. 4). (g)).

According to the above manufacturing method 1, a silicon oxide film (202),
Polycrystalline silicon film (203), and silicon nitride film (
By appropriately changing the film thickness of the field oxide film (205), the width of the field oxide film (20B) can be made finer.

However, in this way, the field oxide film (2H
), the field oxide film (
208) A large protrusion (20g) grows at the upper end. This protrusion (20g) is a field oxide film (
20B), oxidation of the polycrystalline silicon film (203) near the native oxide film (204) thinly formed between the polycrystalline silicon film (203) and the silicon nitride film (205) progresses. caused by For this reason, when miniaturizing the field oxide film (20B), the step coverage of the film formed around this protrusion (2011) decreases, and the wiring etc. provided at the lower end of this protrusion (20g) are difficult to remove. These problems have been clarified by the inventors of the present application.

(Problems to be Solved by the Invention) As detailed above, in the past, when the field oxide film is made finer, the protrusion at the top of the field oxide film grows large, and this protrusion causes the upper end of the field oxide film to grow. Problems have arisen in that the step coverage of films such as electrodes provided on the field oxide film is reduced, and that wiring and the like provided on the field oxide film become difficult to remove due to this protruding lower end. An object of the present invention is to prevent a protrusion from growing at the upper end of the field oxide film.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a first step of forming a first oxide film on a semiconductor substrate; a second step of forming a conductor film on the oxide film of No. 1; a third step of forming an oxidation-resistant film on the conductor film;
a fourth step of selectively removing the oxidation-resistant film on the intended element isolation region, a fifth step of forming a second oxide film on the intended element isolation region, the oxidation-resistant film, and a sixth step of removing the conductor film; a second step and a third step;
During the process, a method for manufacturing a semiconductor device is provided, which is characterized by a non-oxidizing atmosphere.

In the second invention, a first step of forming a first oxide film on a semiconductor substrate, a second step of forming a conductor film on the first oxide film, and a second step of forming a conductor film on the surface of the conductor film. a third step of converting the native oxide film into an oxidation-resistant material by heat treatment; a fourth step of forming an oxidation-resistant film on the oxidation-resistant material; a fifth step of selectively removing the secondary film, and a second step of removing the
A method for manufacturing a semiconductor device is provided, comprising: a sixth step of forming an oxide film; and a seventh step of removing the oxidation-resistant film and the conductor film.

In a third aspect of the invention, there is provided a first step of forming a first oxide film on a semiconductor substrate, a second step of forming a conductor film on the first oxide film, and a second step of forming a conductor film on the surface of the conductor film. a fourth step of forming an oxidation-resistant film on the conductor film; and selectively removing the oxidation-resistant film on the area to be isolated. A fifth step,
a sixth step of forming a second oxide film in the intended element isolation region; and a step of removing the oxidation-resistant film and the conductor film; between the third step and the fourth step; Provided is a method for manufacturing a semiconductor device characterized by a non-oxidizing atmosphere.

(Function) In the first invention, a silicon oxide film and a polycrystalline silicon film are sequentially formed.1. After that, the reaction gas was replaced in the same reaction tube without exposing the surface of the polycrystalline silicon film to the atmosphere.
By depositing the silicon nitride film, it is possible to prevent a natural oxide film from being formed on the surface of the polycrystalline silicon film, and therefore, the growth of a protrusion at the upper end of the field oxide film can be prevented.

In the second invention, since the natural oxide film formed on the polycrystalline silicon film is converted into nitride by thermal nitridation, it is possible to prevent the growth of the protrusion at the upper end of the field oxide film, as in the first invention. .

In the third invention, the semiconductor substrate is transferred from a reaction tube for forming a polycrystalline silicon film to a reaction tube for forming a silicon nitride film.1. After that, the natural oxide film formed by exposure to the atmosphere is removed by etching, and a silicon nitride film is deposited in the same reaction tube. Growth of protrusions can be prevented.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

First, an embodiment of the first invention is shown in FIGS. 1(a) to (g).
Explain using. Silicon substrate (1) which is a semiconductor substrate
01) A silicon oxide film (102) with a thickness of 500 wafers is formed by thermal oxidation on top (FIG. 1(a)).

CV D (Che
ml-cal Vapor Deposltlon) method at a temperature of 650°C and a pressure of 1. A polycrystalline silicon film (tOa) was formed by flowing 5iHa gas into the reaction tube set to OTorr.
Deposit 2,000 people.

Next, in the same reaction tube, this polycrystalline silicon film (103) was heated without exposing the surface of the polycrystalline silicon film (103) to the atmosphere.
3) The temperature is 800℃ and the pressure is 1.0T using the CVD method.
NH containing 5iH2CJ72 in the orr reaction tube
3. Flow the silicon nitride film (1,05) to 2000 ml of silicon nitride film.
People accumulate (Figure 1(b)).

The silicon nitride film (105) in the region where element isolation is to be formed is removed by etching using a resist pattern (not shown) as a mask (FIG. 1(C)).

Next, a field oxide film (1,06) is formed as an element isolation region by thermal oxidation on the portion (109) where the silicon nitride film (105) has been selectively removed (FIG. 1(d)).
.

After forming the field oxide film (10B), the silicon nitride film (105) which is no longer needed is coated with CF4,02. A reaction gas containing N2 is flowed into the reaction tube to generate plasma and remove it by etching. Next, the polycrystalline silicon film (103) is etched using a reactive gas that has a high etching selectivity of the polycrystalline silicon film (103) to the silicon oxide film (102).
) is removed by etching (Fig. 1(e)).

Next, under the field oxide film (10B) by thermal oxidation,
and the silicon substrate (10) under the silicon oxide film (102).
1) is oxidized to form an even thicker film (Fig. 1(f)
).

When forming a field oxide film (LOG), H2O produced by reaction and silicon nitride film (1
05) to form ammonia, and this ammonia reacts with the surface of the silicon substrate to form nitride, which deteriorates the thickness of the gate oxide film to be formed in the next step on the silicon substrate (101). For this purpose, the portion of the surface of the silicon substrate (101) on which the nitride is formed is oxidized, and the unnecessary oxide film and nitride are removed by etching.

After oxidizing the surface of the silicon substrate (101), unnecessary silicon oxide film (102) is removed by etching to complete the field oxide film (10B) forming process (see FIG. 1).
g)).

According to the above manufacturing method, after depositing the polycrystalline silicon film (103), the surface of the polycrystalline silicon film (103) is not exposed to the atmosphere. ), no natural oxide film is formed, and the protrusion (
108) can be prevented from being formed.

Therefore, when miniaturizing the field oxide film (10G), the step coverage of the film formed around the protrusion (108) decreases, and the wiring etc. provided at the lower end of the protrusion (108) become difficult to remove. This can be prevented.

An embodiment of the second invention will be described using FIGS. 2(a) to 2(e).

First, a silicon oxide film (102) with a thickness of 500 nm is formed on a silicon substrate (101), which is a semiconductor substrate, by thermal oxidation.
form. CVD on this silicon oxide film (102)
A polycrystalline silicon film (103) was formed by flowing StH gas into a reaction tube at a temperature of 650°C and a pressure of 0 Torr.
Deposit 2,000 people. After depositing the polycrystalline silicon film (103), the silicon substrate (101) is transferred from the reaction tube to another reaction tube for the next step. At this time, since the surface of the polycrystalline silicon film (103) is exposed to the atmosphere, a very thin natural oxide film (104) is formed on the surface of this polycrystalline silicon film (103) (FIG. 2(a)).

Next, after transferring this silicon substrate (lot) into another reaction tube, the silicon substrate (lot) is rapidly heated to a temperature of 1200℃ using the lamp annealing method, and this gas is naturally Oxide film (104) is reacted and nitride (107) is formed on polycrystalline silicon film (103).
(Fig. 2(b)).

This nitride (107) is thought to be composed of polynitride and polyoxynitride, and polynitride is a nitride formed by reaction between the surface of the polycrystalline silicon film (103) and nitrogen. It is considered. Polyoxynitride is considered to be a nitride formed by a reaction between the natural oxide film (104) and nitrogen.

After changing the natural oxide film (104) into a nitride (107), the nitride (107) is coated at a temperature of 80°C by CVD.
5IH2 was placed in the reaction tube at 0℃ and pressure 1.0 Torr.
A silicon nitride film (10
5) for 2000 people (Figure 2 (C)).

The silicon nitride film (105) in the region where element isolation is to be formed is removed by etching using a resist pattern (not shown) as a mask (FIG. 2(d)).

Next, a field oxide film (10B) with a thickness of 5,000 wafers is formed as an element isolation region by thermal oxidation on the part (109) where the silicon nitride film (105) has been selectively removed (shown in FIG. 2(d)). (Figure 2(e)).

After this step, the same steps as those shown in FIG. 1 (8) to (g) used for the detailed explanation of the first invention are performed to form a field oxide film (10B) on the silicon substrate (101) as an element region. form.

According to the above manufacturing method, the polycrystalline silicon film (103)
After depositing the polycrystalline silicon film (103), the surface of the polycrystalline silicon film (103) is exposed to the atmosphere, and a natural oxide film (104) is formed on the surface of the polycrystalline silicon film (103). However, after this, the natural oxide film (104) was replaced with nitride (104) by thermal nitriding.
07), it is possible to prevent the formation of a protrusion (108) at the upper end of the field oxide film (1oe). Therefore, similarly to the embodiment of the first invention, the field oxide film (1
It is possible to prevent a decrease in step coverage of a film formed around the protrusion (108) when miniaturizing the protrusion (108), and to prevent wiring etc. provided at the lower end of the protrusion (108) from becoming difficult to remove.

An embodiment of the third invention will be described using FIGS. 3(a) to 3(d).

First, a silicon oxide film (102) with a thickness of 500 nm is formed on a silicon substrate (101), which is a semiconductor substrate, by thermal oxidation.
form. CVD on this silicon oxide film (102)
According to the method, the temperature is 650°C and the pressure is 1. A polycrystalline silicon film (103) was formed by flowing 5iHa gas into the OTorr reaction tube.
Deposit 2,000 people. After depositing the polycrystalline silicon film (103), the silicon substrate (101) is transferred from the reaction tube to another reaction tube for the next step. At this time, since the surface of the polycrystalline silicon film (103) is exposed to the atmosphere, a very thin natural oxide film (104) is formed on the surface of this polycrystalline silicon film (103) (FIG. 3(a)).

Next, this silicon substrate (TOI) is transferred into another reaction tube, and then CFa gas is flowed to generate plasma to remove the natural oxide film (104) by etching.

Subsequently, after removing the natural oxide film (104) in the same reaction tube, CVD was performed on the polycrystalline silicon film (103) without exposing the surface of the polycrystalline silicon film (103) to the atmosphere.
The temperature is 800℃ and the pressure is 1. NH3 gas containing 5iH2CJij2 was flowed into a reaction tube set to OTorr to deposit 2000 silicon nitride films (105) (Fig. 13(b)).

The silicon nitride film (105) in the region where element isolation is to be formed is removed by etching using a resist pattern (not shown) as a mask (FIG. 3(C)).

Subsequently, a field oxide film (Hoe) having a thickness of 500 mm is formed as an element isolation region by thermal oxidation on the portion (109) (shown in FIG. 3(C)) where the silicon nitride film (105) has been selectively removed. (Figure 3(d)).

After this step, the same steps as those shown in FIGS. 1(e) to (g) used to explain the details of the first invention are performed to form a field oxide film (TOE) to be used as an element region on the silicon substrate (101). form.

According to the above manufacturing method, after depositing the polycrystalline silicon film (103), the surface of the polycrystalline silicon film (103) is exposed to the atmosphere, and the natural oxide film (104) is
103) Formed on the surface. However, after this, the natural oxide film (104) is removed by etching,
In order to form a silicon nitride film without continuously exposing the surface of the polycrystalline silicon film (103) to the atmosphere, a natural oxide film is formed between the silicon nitride film (105) and the polycrystalline silicon film (1,03). Field oxide film (LOE)
) The formation of a protrusion (10g) on the upper end can be prevented.

Therefore, similar to the first and second embodiments of the invention, when the field oxide Ha (108) is refined, the protrusions (
108) It is possible to prevent a decrease in step coverage of a film formed around the protrusion (108) and to prevent wiring etc. provided at the lower end of the protrusion (108) from becoming difficult to remove.

Moreover, in the embodiment of the third invention, the natural oxide film (104)
Another method for removing polycrystalline silicon film (103)
The natural oxide film (104) formed on the surface is treated with H2O and HF.
A similar effect can be obtained by removing the polycrystalline silicon film (103) by etching by flowing gas, and then depositing the silicon nitride film (105) in the same reaction tube without exposing the surface of the polycrystalline silicon film (103) to the atmosphere.

In addition, the silicon nitride film (105) and polycrystalline silicon film (10
In the removal of step 3), the silicon nitride film (105) is removed, and then the polycrystalline silicon film (103) is etched using a reactive gas with a high etching preference for the polycrystalline silicon film (103) relative to the silicon oxide film (102). ), but this is because the thickness of the field oxide film (106) is changed appropriately to make the field oxide film (106) finer, and etching progresses in the thinner silicon oxide film (102), creating pinholes. This is done to prevent the silicon substrate (101) directly below from being etched.

Further, in each of the embodiments of the first to third inventions, dry etching was used in this case, but wet etching was used to remove the silicon nitride film (105) and polycrystalline silicon H (103). Good too.

In this case, for example, the silicon nitride film (105) is heated to 1
The polycrystalline silicon film (103) may be removed using a 60'C H3P0a solution, and a mixed solution of hydrofluoric acid, nitric acid, and acetic acid.

[Effects of the Invention] According to the present invention, even if the field oxide film is miniaturized, the protrusion at the upper end of the field oxide film does not grow, thereby reducing the step coverage of films such as electrodes provided on the field oxide film, and reducing the protrusion. It is possible to prevent wiring and the like provided at the lower end from becoming difficult to remove.

[Brief explanation of drawings]

1(a) to 1(g) are cross-sectional views showing a method for manufacturing a field oxide film in an embodiment of the first invention, and FIG. 2(a)
) to (e) are cross-sectional views showing the method for manufacturing a field oxide film in the 12th embodiment of the invention, and FIGS. 3(a) to (d)
) is a sectional view showing a method of manufacturing a field oxide film in the third embodiment of the invention, and FIGS. 4(a) to 4(g) are sectional views showing a conventional method of manufacturing a field oxide film. Silicon substrate 101. 201° Silicon oxide film 102. 202° polycrystalline silicon film 103. 203° Natural oxide film Silicon nitride film Field oxide film Nitride protrusion Portion where silicon nitride film is selectively removed at 104, 204° 105, 205° toe, 208° 107, 207° 108, 208°

Claims (3)

[Claims] (1) A first step of forming a first oxide film on a semiconductor substrate, a second step of forming a conductor film on the first oxide film, and a second step of forming an oxidation-resistant film on the conductor film. a fourth step of selectively removing the oxidation-resistant film on the intended element isolation region; and a fifth step of forming a second oxide film on the intended element isolation region. , a sixth step of removing the oxidation-resistant film and the conductive film;
A method for manufacturing a semiconductor device, characterized in that a non-oxidizing atmosphere is used during the step. (2) A first step of forming a first oxide film on the semiconductor substrate, a second step of forming a conductor film on the first oxide film, and a step of forming a conductor film on the surface of the conductor film. a third step of converting the oxide film into an oxidation-resistant material by heat treatment; a fourth step of forming an oxidation-resistant film on the oxidation-resistant material; Fifth selectively removed
A sixth step of forming a second oxide film in the region to be isolated, and a seventh step of removing the oxidation-resistant film and the conductor film. A method for manufacturing a semiconductor device. (3) a first step of forming a first oxide film on the semiconductor substrate; a second step of forming a conductor film on the first oxide film; and a step of forming a conductor film on the surface of the conductor film. a third step of removing an oxide film; a fourth step of forming an oxidation-resistant film on the conductor film; and a fifth step of selectively removing the oxidation-resistant film on the intended element isolation region. a sixth step of forming a second oxide film in the region to be isolated, and a step of removing the oxidation-resistant film and the conductive film, and a third step and a fourth step. A method for manufacturing a semiconductor device, characterized in that the atmosphere is non-oxidizing.