JPS5994852A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the generation of a strain stress and to prevent the generation of warpages and crystal defects of a semiconductor substrate, which are caused by the strain stress, by a method wherein nitride films are formed on the back surface of the substrate and the back surface is made into a condition to make it difficult for thick oxide films to be formed on the back surface, when the thick oxide films are formed by performing a selective oxidation on the substrate. CONSTITUTION:An N type epitaxial layer 2 is grown on a P type silicon substrate 1. Oxide films 3 and nitride films 4 are formed on the surface and the back surface of the substrate 1, and the epitaxial layer 2 is insulatingly separated by oxide films 5 according to a selective oxidation. On the separated region 2', a P type base diffusion region 6, an N<+> type collector diffusion region 7 and an N<+> type emitter region 8 are diffused in order to form a transistor. The oxide films are not formed so much on the back surface due to the nitride films 4, and a strain stress, which is generated when the thick oxide films 5 are formed by patterning, can be absorbed even on the surface of the substrate, so it is made more difficult for the strain stress to generate on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device using a selective acid (1' method), and in particular, when forming an i-oxide film by selective oxidation, stress generated due to strain stress applied to a substrate crystal. The present invention relates to a method of manufacturing a semiconductor device that can prevent warpage and crystal defects from completely deteriorating device characteristics.

(generally produced using selective oxidation method) (Ibora IC
Figures 1(a) and 1(b) are diagrams showing the entire manufacturing process. First, as shown in FIG. 1(a), an N- type epitaxial layer 2 is grown on a P-type semiconductor substrate 1. Next, an extremely thin oxide film (SiU) is applied to the surface of the epitaxial layer.
z) A nitride film (SiaNs) is formed on the surface of the substrate via the nitride film 4, and a desired notch is formed in the nitride film 4 by selective etching (No. 11(b)). Furthermore, Figure 1 (c
) As shown in VC, selective ridge formation is performed on the substrates other than the protective film 4 until it reaches the P-type substrate 1, and the entire epitaxial layer is insulated and separated by a thick single-layer film 5 formed by selective heating. Next, a transistor is formed by diffusing a P type base diffusion region 6N + type collector diffusion region 7 into the separated region 2', and further diffusing an N + type emitter region 8 into the base diffusion region 6 using a selective diffusion technique (i1 Figure (d)).

In this case, when the thick oxide film 5 is formed by selective oxidation, a thin oxide film 5'75Et is simultaneously formed on the entire back surface (Fig. 1(C)), which is larger than the area of the thick L'&Ihi film 5 on the front surface of the substrate. The planar shape of the thick oxide film 5' on the back side of the substrate is much larger (because it is larger, the expansion force due to the oxide film on the back side is stronger than that on the front side, causing the board to warp in a concave shape.For this reason, strain stress is concentrated in the center of the board. This causes crystal defects 9 to coexist and deteriorates device characteristics.

As described above, warpage and crystal defects occurring in the substrate are strongly influenced by the overnight film thickness of selective oxidation, pattern surface quality, etc., so it was difficult to select one manufacturing process.

The present invention has been made in response to the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a semiconductor device that eliminates the adverse effects of selection and has good device characteristics.

The unique feature of this invention is that when forming a thick oxide film by selectively oxidizing the semiconductor substrate, it is necessary to form a nitride film or a heat-resistant metal such as tungsten on the back surface in advance, or to make it adhere to a quartz plate, etc. By creating a state in which it is difficult to fully form a thick oxide film, the purpose is to suppress the generation of strain stress and prevent warping of the substrate and crystal defects caused by strain stress.

Detailed explanation of the present invention with reference to Figure ll1I below Figure 2 (a
)~((1) is a cross-sectional view of the fabrication process of a semiconductor device for explaining an embodiment of the present invention. First, as shown in FIG. 2(a), a P-type silicon substrate is prepared. A VCN-type epitaxial layer 2 is entirely grown on top of this.

Next, an extremely thin oxide film 3 having a thickness of about 0.03 μm is expanded on the front and back surfaces of the substrate 10 having the entire epitaxial layer 2, and a layer 11 and a layer 4 are formed thereon, and then a nitride film is formed only on the surface of the substrate. A pattern corresponding to the entire insulating region is selectively etched and removed (FIG. 2(b)).

In addition, selective oxidation is performed like the K pore in FIG.
For example, selective oxidation of about 1.5 μm is performed until vc is reached, and the epitaxial layer is insulated and isolated by a thick oxide film 5Vc by selective oxidation.

Next, a P-type base diffusion region 6sN"!J! collector diffusion region 7, and further a Vr-N+ type emitter region 8 in the base diffusion region 6 are diffused into the separated region 2' by a selective diffusion technique. formed (Fig. 2 (
d)).

With the method described above, the oxide film is not formed much on the back surface due to the nitride film left on the back surface when the thick oxide film 5 is entirely formed by selective oxidation (FIG. 2(C)). For this reason, there is almost no change in the film quality on the back side of the substrate, and since the strain stress generated when forming the thick oxide film 5 can be absorbed by the pattern on the front side of the substrate, strain stress is less likely to occur on the substrate. Therefore, it is possible to prevent warping of the substrate and the occurrence of crystal defects due to strain stress, and therefore it is possible to directly manufacture semiconductor devices with good device characteristics.

As explained above, the present invention provides a method of manufacturing a semiconductor device with excellent device characteristics by eliminating the adverse effects of selective oxidation.

[Brief explanation of drawings]

FIGS. 1(a) to (d) are schematic cross-sectional views of the manufacturing process showing the conventional manufacturing method of a semiconductor device and the occurrence of crystal defects associated therewith, and FIGS. 2(a) to (d) are one example of the present invention. FIG. 1 is a schematic cross-sectional view of a manufacturing process showing a method of manufacturing a semiconductor device according to the Rin Example. 1...P-type silicon substrate, 2...N-
type epitaxial layer, 2'... isolated epitaxial layer region, 3... extremely thin oxide film, 4... nitride film, 5... selection Thick oxide film formed by oxidation, 5'... Thick oxide film formed on the back surface by oxidation, 6... P type base diffusion region, 7... N+ type collector Amnesty area, 8.
...N-type emitter region.

Claims (1)

[Claims] When selectively converting the surface of a semiconductor substrate, it is necessary to form an oxide-resistant layer such as a substrate element nitride film or a high-temperature heat-resistant metal on the back side of the substrate in advance, or to bring the back side into close contact with an oxide-resistant plate such as a quartz plate. 1. A method of manufacturing a semiconductor device, comprising: bringing the surface of the semiconductor device into a state where it is more difficult to form an oxide film.