JPS60193324A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To provide an epitaxial layer with better crystallization, by forming an opening through an insulating film being coated on an Si substrate, and by growing the opitaxial layer only in the opening after a polycrystalline or amorphous Si thin film touching the substrate surface is formed on the walls of the opening. CONSTITUTION:After an SiO2 film is coated on an Si substrate 11 and an SiO2 film pattern 12 with a vertical cross sectional area is formed with photolithography and reactive ion etching, a contaminated layer produced on the substrate 11 surface is removed with wet etching. Next, an amorphous Si layer 13 is deposited over all faces including top faces and side faces of the pattern 12, and the layer 13 only on the side faces of the pattern 12 is left and the other is removed with reactive ion etching. Thereafter, using H2 gas and SiH2Cl2 gas containing HCl gas of about 1vol%, an epitaxial layer 14 having the approximately same height as that of the pattern is grown. Accordingly, the epitaxial layer free from crystal defect which is surrounded by the amorphous layer can be provided.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a semiconductor substrate in which a silicon epitaxial layer is selectively grown on a single crystal silicon substrate having an insulating film pattern on its surface. Yes (Problems with the Prior Art) A partial oxidation method (LOCOa method) has been used to isolate active elements in conventional semiconductor devices.

However, in the selective thermal oxidation step, the oxidized layer undergoes lateral bite (bird's beak), which changes with respect to the mask dimensions, which has been an obstacle to achieving higher density.

Selective epitaxial technology is one of the techniques for improving the above-mentioned drawbacks. In this method, an insulating film is formed partially on a semiconductor single crystal substrate, and a semiconductor crystal of the same type as the substrate is epitaxially grown only on the exposed substrate area without depositing on the insulating film, and that part is used as the active area of the device. It is something to do.

The substrate used in conventional selective epitaxy is formed by forming an insulating film on a single crystal substrate and then partially opening the insulating film, so the interface between the insulating film and the epitaxial film depends on the plane orientation of the single crystal substrate used. be influenced by. Although the surface of the pinched epitaxial layer is smooth, since the crystal growth rate differs depending on the crystal plane, facets occur and a flat surface without irregularities cannot be obtained. A semiconductor substrate in which a polycrystalline or amorphous silicon thin film is formed only on the side walls of the insulating film in the opening to flatten this, and then silicon is epitaxially grown to form a flat structure regardless of the substrate surface. The manufacturing method is described in Japanese Patent Application No. 57-153766.

The structure of this semiconductor substrate will be explained in detail using the drawings.

Figure 1 (a) l (b) j (C1j (d) schematically shows the cross-sectional structure of the substrate in the main manufacturing steps of the above manufacturing method in order. 8
A desired portion K8i0. An insulating layer 2 is formed thereon. Since the reactive ion etching in this case mainly uses an etching gas containing carbon, an impurity contamination layer is formed on the exposed silicon surface after the 8i0° etching. In order to prevent this, it is necessary to leave or form a thin insulating film 3 with a thickness of about 50X on the 8i substrate 1 in advance. Next, as shown in FIG. 1(b), after a polycrystalline or amorphous 8i' film 4 is deposited on the entire surface, it is etched onto the side walls of the insulating film by reactive ion etching. Leave the quality Si layer. The thin insulating film 3 shown in FIG. 1(a) serves as a stopper during reactive ion etching of the polycrystalline or amorphous 8i shown in FIG. 1(b)K. This prevents crystal damage and impurity contamination. Next, after removing the thin insulating film shown in FIG. 1(C) using a wet etching method containing hydrofluoric acid, selective epitaxial growth is performed to form Si only on the 8i substrate with the opening shown in FIG. 1(d). A t-deposited flat epitaxial Si layer 5 is obtained. However, since the silicon layer covering the side walls of the insulating film does not come into contact with the single crystal silicon substrate through the insulating film layer 6, it is difficult to rearrange it into a high-quality single crystal during epitaxial growth. A layer 7 with many crystal defects is formed. For example, when a p-n junction is provided in such an epitaxial silicon layer, a leakage current is generated, which causes a decrease in dielectric strength and a significant drop in manufacturing yield. In a semiconductor substrate in which a silicon thin film is entirely formed without intervening an insulating film 3, and the silicon layer covering the side walls 2 of the insulating film is in contact with an 8i substrate by reactive ion etching, an impurity contamination layer is formed on the Si substrate. arise. Although this contamination layer can be recovered by heat treatment at 900°C, the crystallization of the silicon layer covering the sidewalls of the insulating film progresses and the number of crystal grains increases, making it difficult to rearrange into a single crystal during epitaxial growth. there was.

(Object of the Invention) The object of the present invention is to provide a method for manufacturing a semiconductor substrate for obtaining a selective epitaxy layer with good crystallinity and no crystal defects even near the sidewalls of an insulating film pattern formed on a silicon single crystal substrate. It is about providing.

(Structure of the Invention) According to the present invention, an insulating film is formed on a substrate having a silicon single crystal layer, an opening is provided in a desired portion of the insulating film, and then an opening is selectively formed only in the opening. In a method for manufacturing a semiconductor substrate in which a crystalline silicon film is grown epitaxially, a contamination layer formed on the exposed silicon surface after forming an opening in the insulating film by dry etching is removed,
Next, a polycrystalline or amorphous silicon thin film is formed, and then reactive ion etching is performed using an etching gas containing carbon to form a polycrystalline or amorphous silicon thin film on the side wall of the insulating film in contact with the substrate silicon. A method for manufacturing a semiconductor substrate, characterized by:

(Example) Next, the present invention will be explained in detail using the drawings. Figure 2(a)
(b) (c) (dl is a diagram for explaining the present invention in detail, and is a schematic cross-sectional view sequentially showing the cross-section of the substrate in the main manufacturing process.

First, a silicon single crystal substrate 11 having a (100) plane is
After thermally oxidizing at 00σC to form a Si film with a thickness of approximately 2 μm, an 8i0. Insulating film pattern 12
Form ft. Removes a contamination layer formed on the surface of a silicon substrate by dry etching.
When a 5i02 film of about 6200 to 300X is formed and the 5i02 film is etched by ordinary wet etching, the structure shown in FIG. 2(a) is obtained.

Next, sheamorph gas silicon 1 was produced using plasma CVD method.
2(b) is obtained by depositing 3 at 700X. Next, stG/* gas 40 cc/1 nin was introduced using a parallel plate dry etching device, and the pressure was 80 mTorr.
When reactive ion etching is performed at a power density of 0.1 wA-rl, only the silicon substrate surface and the upper part of the 5i02 insulating film pattern are etched.If etching gas is used, only Cl impurities are mixed into the substrate, so heat treatment in an inert gas Can be easily removed. Next, about 1 vol% of HCII is added to the gas system consisting of 8iH, CI, and H, and silicon is epitaxially grown selectively only on the silicon substrate surface at a temperature in the range of 900'C to 1100'C. When the film thickness is 2 μm, the result shown in FIG. 2(d) is obtained.

In the above embodiment, a plasma CVD-'J' morph gas silicon thin film with a thickness of 700A was used as the silicon thin film formed on the side wall of the insulating film, but the invention is not limited to this if writing alignment is possible during epitaxial growth. Instead, polycrystalline or amorphous silicon formed by low-pressure CVD, photoCVD, or sputtering may also be used.
Although IC/4 gas was used, a mixed gas of C72 and Ar may be used as long as it is free from contamination such as carbon.

Further, in the above embodiment, the insulating film is made of Sin by thermal oxidation.
, Si, N4 film, 8i0. It may be a deposited film or a PSG film (phosphorus glass film).

Further, in the above embodiment, S I H2Cit p Hz p 1”I was used as the gas used for selective epitaxial growth.
Although a C1 mixed gas was used, it is not limited to this.
II2, 14CI mixed gas or the like may be used. Further, a doping gas such as AsH3°PH, B, H6, etc. may be included in these mixed gases.

(Effect of the invention) By using the present invention, a polycrystalline or amorphous silicon layer is formed on the side wall of the insulating film in contact with the silicon substrate without forming an impurity contamination layer on the surface of the silicon single crystal substrate. In addition, polycrystalline or amorphous silicon can be easily rearranged during epitaxial growth, and a flat epitaxial layer without crystal defects can be obtained.

[Brief explanation of the drawing]

1(a) to 1(d) are schematic cross-sectional views sequentially showing the cross sections of the substrate in the main manufacturing steps according to the conventional method. 1 is a schematic cross-sectional view sequentially showing the cross-section of a substrate in the process. Numbers in the figure indicate the following: 1.11...Silicon single crystal substrate, 2.12...Insulating film cut turn , 3... Thin insulating film, 4... Polycrystalline silicon film, 5.14... Single crystallized epitaxial silicon region, 6... Thin insulating film between polycrystalline silicon film and silicon substrate, 7...Epitaxial silicon region containing crystal defects, 13...Amorphous silicon thin film.

Claims (1)

[Claims] Manufacturing a semiconductor substrate by forming an insulating film on a substrate having a silicon single crystal layer, then providing an opening in a desired portion of the insulating film, and then epitaxially growing a single crystal silicon film selectively only in the opening. In this method, after forming an insulating film opening, a contamination layer formed on the exposed silicon surface by dry etching is removed, a polycrystalline or amorphous silicon thin film is formed, and then a carbon-free etching gas is used. 1. A method for manufacturing a semiconductor substrate, which comprises performing reactive ion etching to form a polycrystalline or amorphous silicon thin film on the sidewall of an insulating film in contact with substrate silicon.