JPS62296537A - Manufacture of selective oxide film - Google Patents

Abstract

PURPOSE:To prevent variation of the photoresist size by oxidizing a silicon substrate to about 1/2 of the groove depth, growing a polycrystalline silicon film, and oxidizing the polycrystalline silicon film and selectively oxidizing the underlying silicon oxide film. CONSTITUTION:In a silicon groove portion 5, a first selective oxide film 6 is formed in an oxygen and hydrogen gas atmosphere, and then a polycrystalline silicon layer 7 is grown. The polycrystalline silicon layer 7 and the first selective oxide film 6 are oxidized to prevent the polycrystalline silicon of the polycrystaline silicon layer 7 from remaining on a silicon nitride film 3 as a mask, and the first selective oxide film 6 and the polycrystalline silicon oxide film layer are oxidized, becoming a dense oxide film. The surface of the regions of the oxide film of the polycrystalline silicon layer 7 on the silicon nitride film 3 and a second selective oxide film 8 is removed, making the selective oxide film thickness a desired thickness. Further, the silicon nitride film 3 is removed to form a second selective oxide film 8 and a non-selective oxide film region 9. With this, variation of the photoresist size can be prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a selective oxide film for isolation between elements in the manufacturing process of a semiconductor device, and in particular to a method for manufacturing a selective oxide film for isolation between elements in the manufacturing process of a semiconductor device. The present invention relates to a method for manufacturing a selective oxide film that reduces burrs and steps.

[Conventional technology]

Conventionally, as a device isolation method using this type of oxide film, a silicon nitride film is formed on a silicon substrate, and a desired portion of the silicon nitride film is removed by etching using photoresist 1 as a mask. Next, after removing the photoresist, the silicon substrate is oxidized using the silicon nitride film as a mask to form a selective film, and element isolation regions are formed. Figure 2(a)
- (C) are vertical cross-sectional views of pellets shown in order of steps to explain the conventional selective oxide film forming method.

First, as shown in FIG. 2(a), a thin silicon oxide film 2 is formed on a silicon substrate 1, and a silicon nitride film 3 is formed on it.
After forming, a photoresist 4 is applied, and the photoresist 4 is patterned using lithography technology.

Thereafter, the photoresist nitride film 3 is etched as shown in FIG. 2(1). Next, after removing the photoresist 4, the silicon substrate 1 is oxidized from the opening of the silicon nitride film 3 using the silicon nitride film 3 as a mask. At this time, a selective oxide film 8 is formed as shown in FIG. 2(c).
A step is created between the surfaces of the non-oxidized region 9 of the silicon substrate 1 and the selective oxide film 8 under the silicon nitride film 3 serving as a mask. In addition, in oxidation using the silicon nitride film 3 as a mask, the silicon substrate 1 under the silicon nitride film
is continuously oxidized starting from the edge of silicon nitride 11, although the amount of oxidation gradually decreases, and its lateral dimension becomes approximately the same as the thickness of the selective oxide film.

At the same time, the end of the silicon nitride film, which is a mask, is lifted up by the oxidation of the silicon substrate under the end of the silicon nitride film, and the amount thereof is 50 to 50% of the film thickness of the selective oxide film 8. The amount will be 60%.

[Problem that the invention seeks to solve]

In the conventional element isolation method using a selective oxidation layer using a silicon nitride film as a mask, the volume of the oxide film expands when the oxidized region is oxidized, and the surface of the oxidized region becomes higher than the surface of the non-oxidized region. There is a step between the two. This step difference between the oxidized region and the non-oxidized region is used to create the desired fine photoresist in the non-oxidized region near the oxidized region when miniaturizing the device! ~ When trying to form a pattern, the pattern is not formed to the desired dimensions, and the dimensions of the pattern formed in an area sufficiently far away from the oxidized area are different from the dimensions of the pattern formed in the non-oxidized area near the oxidized area, resulting in poor dimensional accuracy. In addition, the silicon nitride film used as an oxidation mask is oxidized to the bottom of the mask, and its lateral dimension is almost the same as the selective oxide film thickness, making it unsuitable for future fine element region formation. be.

An object of the present invention is to prevent the progress of oxidation in the lateral direction of the silicon substrate when forming a selective oxide film using a silicon nitride film as a mask, and to prevent the height of the silicon substrate surface of the non-selective oxidation region and the surface of the selective oxidation region from increasing. It is an object of the present invention to provide a method for manufacturing a selective oxide film that can have substantially the same height and prevent large differences in the dimensions of the resist 711 formed in selectively oxidized regions and non-selectively oxidized regions.

[Means for solving problems]

The selective oxide film manufacturing method of the present invention involves patterning a silicon nitride film and a base silicon oxide film formed on a silicon substrate using photolithography, etching the silicon substrate using a photoresist as a mask, and dry etching the silicon substrate. A process of etching to form a silicon substrate groove, a process of oxidizing the silicon substrate to about 1/2 of the depth of the groove, a process of growing a polycrystalline silicon film using a vapor phase growth method, and a process of growing a polycrystalline silicon film using a vapor phase growth method. A process of selectively oxidizing the base silicon oxide film at the same time as etching, a process of etching and removing the polycrystalline silicon oxide film on the surface of the silicon nitride film and making the selective oxide film a desired thickness, and using it as an oxidation mask. The method includes a step of removing the silicon nitride film used.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1(a) to 1(g) are longitudinal cross-sectional views of pellets 1 to 1 shown in order of process for explaining one embodiment of the present invention.

First, as shown in FIG. 1(a), a silicon substrate 1 is oxidized in an oxidation furnace to form a thin silicon oxide film 2 of 200 to 300 layers, and a silicon nitride layer is formed on the surface using a vapor phase growth method. Film 3 is grown to a thickness of 1500 to 2500 nm.

Next, a photoresist is applied, and a desired pattern is formed on the photoresist 4 using photolithography technology.

Next, as shown in FIG. 1(b), the silicon nitride film is etched away using a photoresist etching device, and the silicon oxide film 2 is etched away using a hydrofluoric acid aqueous solution. Next, using the photoresist 4, silicon nitride film 3, and silicon:non-oxide film 2 having a desired pattern as masks, the silicon substrate 1 is etched by about 2,000 to 3,000 times using a dry etching apparatus. Then, a silicon hot water portion 5 is formed on the silicon substrate 1, which is then removed by a photoresist plasma stripper 6 used as a mask.

Next, as shown in FIG.
Approximately 3,000 to 4,000 people were oxidized under oxygen and hydrogen gas using a high-pressure oxidation furnace or a normal-pressure oxidation furnace at a temperature of 000 to 1,130°C.
If! i Selective oxidation deoxidation film 6.

Next, as shown in FIG. 1 (cl), a polycrystalline silicon layer 7 having a thickness of about 3000 wafers is grown using a reduced pressure vapor phase growth apparatus.

Next, as shown in FIG. 1(e), a polycrystalline silicon layer 7
Then, the first selective oxide film 6 is oxidized with oxygen and hydrogen gas using a high-pressure oxidation furnace or a normal-pressure oxidation furnace at 1000 to 1300°C, and a polycrystalline silicon layer is formed on the silicon nitride film 3 as a mask. 7 so that no polycrystalline silicon remains, and the first selective oxide film 6 and the polycrystalline silicon oxide film layer 2 of the first selective oxide film are sufficiently oxidized to form a dense oxide film,
The thickness should be approximately 1.2 μm. As a result, the edges of the silicon nitride film are sufficiently suppressed by the polycrystalline silicon layer, reducing oxidation in the lateral direction of the substrate, and also preventing the silicon nitride film 3, which serves as a mask, from being held at the edge of the pattern from forming on the sidewalls. The retention at the pattern end of a conventional silicon nitride film that does not contain polycrystalline silicon and does not cover the nitride top with polycrystalline silicon is reduced to approximately half the amount.

Next, as shown in FIG. 1(f), in order to remove the oxide film of the polycrystalline silicon layer formed on the surface and sidewalls of the silicon nitride film 3, a hydrofluoric acid aqueous solution is used to remove the polycrystalline silicon layer on the silicon nitride film. The oxide film 8 is completely removed and the second selective oxide film 8 is removed.
The surface of the area is slightly etched away to make the selective oxide film thickness to the desired thickness.

Next, the silicon nitride M3 used as a mask was removed with a phosphoric acid solution at around 160°C, and a second
A selective oxide film 8 and a non-selective oxide film region 9 are formed.

[Efficacy of invention Song Dynasty]

As explained above, the present invention forms a polycrystalline silicon layer on the surface of the silicon nitride film as an oxidation mask and on the sidewalls of the silicon substrate groove to prevent oxidation from progressing in the lateral direction of the silicon substrate under the silicon nitride film. By preventing the openings in the silicon nitride film from oxidizing, the progress of oxidation in the lateral direction of the silicon substrate is reduced to about half that of the conventional method, and the height of the silicon substrate surface in the non-selective oxidation region and the selective oxidation region are reduced. This has the effect of making the surface heights almost the same. Furthermore, when a photoresist is applied and patterned on the surface layer in the next step, it is possible to prevent the dimensions of the photoresist 1 formed in the selectively oxidized region and the non-selectively oxidized region from being significantly different.

[Brief explanation of drawings]

FIGS. 1(a) to (g>) are longitudinal cross-sectional views of a pellet shown in the order of steps for explaining one embodiment of the present invention, and FIG. 2(a)
-(c) are vertical cross-sectional views of pellets shown in order of steps to explain a conventional method of forming a selective oxide film. 1... Silicon substrate, 2... Thin silicon oxide film,
3... Silicon nitride film, 4... Photoresist, 5
... Silicon hot water part, 6... First selective oxide film, 7...
- Polycrystalline silicon layer, 8... second selective oxide film, 9...
Non-selective oxidation region. -10= Kaya l Figure Kaya 2 Figure

Claims (1)

[Claims] Patterning the silicon nitride film and base silicon oxide film formed on the silicon substrate using photolithography technology, etching the photoresist as a mask, etching the silicon substrate by dry etching, and forming a silicon substrate groove. , a step of oxidizing the silicon substrate to about 1/2 of the trench depth, a step of growing a polycrystalline silicon film using a vapor phase growth method, and a step of oxidizing the polycrystalline silicon film and selectively oxidizing the underlying silicon oxide film. a step of etching and removing the polycrystalline silicon oxide film on the surface of the silicon nitride film and making the selective oxide film thickness a desired thickness; and a step of removing the silicon nitride film used as an oxidation mask. A method for producing a selective oxide film, comprising: