JPH0234179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION To describe the present invention in more detail than a semiconductor device, the present invention relates to a VIP (V-groove Isolation Polycrystal
This invention relates to a method of manufacturing a semiconductor device in which a semiconductor substrate is grounded using an insulating layer separation structure (backfill).

An epitaxial growth layer is formed on a semiconductor substrate (silicon wafer), and when active elements such as transistors and passive elements such as resistors are formed within this epitaxial growth layer, these elements are isolated. It is also necessary to provide a conductive portion in the epitaxial layer for grounding the substrate at an appropriate location. If isolation is performed using the PN junction separation method,
The impurity diffusion region reaching the substrate can be used as a conductor portion for grounding at the same time as the separation layer. If the semiconductor substrate is P-type, P-type impurities (for example, boron) are separated and diffused into the N-type epitaxial growth layer, but this separation and diffusion requires heat treatment at a fairly high temperature for a long time. be. For example, to diffuse boron (B) into a 2.4 μm thick epitaxial growth layer until it reaches the substrate, the temperature is 1150 [℃].
It takes 40 minutes. Due to this heat treatment, N-type impurities are also diffused from the buried layer (for example, N ⁺ buried region) formed in the semiconductor device, and the buried layer expands into the epitaxial layer, which also induces crystal defects. be done. This deteriorates the characteristics of the semiconductor device.

In a semiconductor device using the insulation layer separation of the VIP structure, as is clear from FIG. 1, the VIP structure cannot be used to connect the substrate to ground because of the silicon dioxide (SiO ₂ ) insulation film. Note that FIG. 1 is a schematic cross-sectional view of a VIP structure portion of a semiconductor device, and shows that a V-groove 3 formed in a semiconductor substrate 1 and an epitaxial growth layer 2 thereon is an oxide film (SiO ₂ ) on the surface of the V-groove. film)
4 and a polycrystalline silicon layer 5, and there is a thick oxide film (SiO ₂ film) 6 on the surface of the polycrystalline silicon film 5.

An object of the present invention is to provide a method for manufacturing a semiconductor device that can connect the surface of the semiconductor device to the semiconductor substrate without performing long-term high-temperature heat treatment such as separation diffusion in PN junction separation.

An object of the present invention is to provide a method for manufacturing a semiconductor device using a VIP insulating layer isolation structure for grounding a semiconductor substrate.

The above purpose is to form an epitaxial layer of an opposite conductivity type on a semiconductor substrate of one conductivity type, then to form a V-groove reaching from the surface of the epitaxial layer to the semiconductor substrate, and then to form an epitaxial layer in the V-groove. a step of sequentially depositing an oxidation-resistant film and a polycrystalline silicon film; then a step of oxidizing the polycrystalline silicon film portion other than the polycrystalline silicon film portion at the tip of the V-groove; removing the polycrystalline silicon film and exposing the polycrystalline silicon film at the tip of the V-groove, and then selectively etching the oxidation-resistant film using the exposed polycrystalline silicon film as a mask. a step of leaving an oxidation-resistant film portion only at the tip of the V-groove; a step of performing selective oxidation using the oxidation-resistant film portion at the tip of the V-groove as a mask to form a silicon oxide film on the inner surface of the V-groove; Next, after removing the oxidation-resistant film to expose the semiconductor substrate at the bottom of the V-groove, a step of embedding a semiconductor layer containing one conductivity type impurity in the V-groove is performed, and then heat treatment is performed. This can be achieved by a method for manufacturing a semiconductor device, comprising the step of diffusing impurities in the semiconductor layer into the semiconductor substrate.

To describe in detail the process from after V-groove formation to before disposing a semiconductor layer containing one conductivity type impurity, for example, the following steps (a) to (g): (a) Epitaxial growth layer and semiconductor substrate A thin silicon dioxide (SiO ₂ ) film is formed on the exposed surface of the V-groove by thermal oxidation. (a) A nitride film, which is an oxidation-resistant film, is formed on the formed SiO ₂ film. (c) This nitride film A thin polycrystalline silicon film (e.g., 2000 Å thick) is formed on top of the V-groove, and this polycrystalline silicon film is oxidized by thermal oxidation except for the tip of the V-groove to form a SiO ₂ film. (d) SiO ₂ (e) Remove the nitride film on the slope of the V-groove using the polycrystalline silicon film remaining at the tip of the V-groove as a mask; (f) Thermal oxidation Further oxidize the V-groove slope by
This can be done by increasing the thickness of the SiO ₂ film, and (g) removing the remaining polycrystalline silicon film, nitride film, and thin SiO ₂ film thereunder.

Hereinafter, a semiconductor substrate and a method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

For example, P-type silicon semiconductor substrate 11 (second
An N-type silicon epitaxial growth film (for example, 2.4 μm thick) 12 is formed on the top of the epitaxial growth layer (Fig.), and the surface of this epitaxial growth layer is subjected to a thermal oxidation method or
A silicon dioxide (SiO ₂ ) film 13 (for example, 1500 mm thick) is deposited by the (Chemical Vapor Deposition) method.
), and then a silicon nitride (Si ₃ N ₄ ) film 14 (eg, 2800 Å thick) is formed by CVD. Next, the silicon nitride film 4 and silicon dioxide film 13 in the V-groove formation region are etched by photoetching.
The epitaxial growth layer 12 and the substrate 11 are selectively etched and further anisotropically etched.
A V-groove is formed as shown in FIG. The surface (slope) of the V-groove is oxidized by thermal oxidation to form a thin silicon dioxide film 15 (eg, 500 Å thick) (FIG. 2).

A silicon nitride film 16 (eg, 800 Å thick) is deposited by CVD on the silicon dioxide film 15 in the V-groove and the previously formed silicon nitride film 14 (FIG. 3). The total thickness of the nitride film 14 outside the V-groove is 3600 Å. Next, a polycrystalline silicon film (for example, 2000 Å thick) is formed on the silicon nitride film by CVD, and this polycrystalline silicon film is oxidized by thermal oxidation to form a silicon dioxide film 17.
(4000 Å thick). During this thermal oxidation, V
The polycrystalline silicon film 18 at the tip of the groove remains as shown in FIG. 3 without being oxidized.

Next, the silicon dioxide film 17 is removed using an etching solution (fluoric acid solution) to expose the polycrystalline silicon film 18 and the silicon nitride film. Subsequently, the silicon nitride film 16 is removed using an etching solution (phosphoric acid boiling solution). At this time, the remaining polycrystalline silicon film 18 serves as a mask, and a portion of the silicon nitride film 16 remains at the tip of the V-groove, and the nitride film 14 outside the V-groove is thinned by etching to its original thickness. (Figure 4).

The polycrystalline silicon film 18 is removed, and the epitaxial growth layer 12 and substrate 11 are oxidized by thermal oxidation through the thin silicon dioxide film 15 on the V-groove surface to form a relatively thick silicon dioxide film 19 (for example, 5000 Å thick). form (Figure 5).

The silicon nitride film 16 remaining at the tip of the V-groove is removed by etching. At this time, the thickness of the silicon nitride film 14 is also reduced, but it must not be removed. Next, a thin silicon dioxide film 15 at the tip of the V-groove is
is removed by etching to expose the semiconductor substrate 11. This etching also reduces the thickness of the relatively thick silicon dioxide film 19 on the V-groove surface by about 500 Å. Next, polycrystalline silicon is formed thick enough to fill the V-groove while doping impurities (for example, boron) using the CVD method, and by wrapping, the polycrystalline silicon 20 is left only in the V-groove and the rest is removed. (Figure 6). Of course, impurities may be doped after the polycrystalline silicon is grown and wrapped. During wrapping, the silicon nitride film 14
acts as a stopper.

Then, the surface of the polycrystalline silicon 20 is thermally oxidized to form a thick silicon dioxide film 21 (for example, 8000 mm thick).
Å) is formed. Impurities (boron) doped into the polycrystalline silicon 20 by this heat treatment
diffuses into the semiconductor substrate 11 at the tip of the V-groove, and also diffuses during heat treatment when forming the base, emitter, etc. of the transistor, and spreads to the region 22 shown by the broken line in FIG. This diffusion region 22 also serves as a channel cut. An opening for contact is formed in the silicon dioxide film 21 on the surface by photoetching, and a ground electrode 23 is formed. In this way, the substrate can be grounded, and a semiconductor device according to the present invention can be obtained.

Although active elements such as transistors, passive elements, and buried layers are not shown in the drawings, they are formed by conventional known methods.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a semiconductor device having a VIP insulation layer isolation structure, and FIGS. 2 to 7 are partial cross-sectional views of the semiconductor device for explaining a method of manufacturing a semiconductor device according to the present invention. 11... Semiconductor substrate, 12... Epitaxial growth layer, 13... Silicon dioxide film, 14... Silicon nitride film, 15... Silicon dioxide film, 16
...Silicon nitride film, 18...Polycrystalline silicon,
19... Silicon dioxide film, 20... Polycrystalline silicon, 22... Diffusion region, 23... Earth electrode.

Claims (1)

[Scope of Claims] 1. A step of forming an epitaxial layer of an opposite conductivity type on a semiconductor substrate of one conductivity type; Next, a step of forming a V groove reaching from the epitaxial layer to the semiconductor substrate; a step of sequentially depositing an oxidation-resistant film and a polycrystalline silicon film in the groove; then a step of oxidizing the polycrystalline silicon film portion other than the polycrystalline silicon film portion at the tip of the V-groove; removing the exposed polycrystalline silicon film to expose the polycrystalline silicon film portion at the tip of the V-groove, and then selectively removing the oxidation-resistant film using the exposed polycrystalline silicon film portion as a mask. A step of etching to leave an oxidation-resistant film portion only at the tip of the V-groove, and a step of performing selective oxidation using the oxidation-resistant film portion at the tip of the V-groove as a mask to form a silicon oxide film on the inner surface of the V-groove. Then, after removing the oxidation-resistant film to expose the semiconductor substrate at the bottom of the V-groove, burying a semiconductor layer containing one conductivity type impurity in the V-groove, and then heat treatment. and diffusing impurities in the semiconductor layer into the semiconductor substrate.