JPH02237133A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To simplify a process and to enhance reliability by a method wherein, after a mask used to form a highly doped layer has been formed at an opening part in a semiconductor substrate, a mask, for opening-port formation use, which includes the mask directly under it is formed and an epitaxial layer whose film thickness is different is formed on the semiconductor substrate. CONSTITUTION:A silicon oxide film 16 is formed on a semiconductor substrate 1; the silicon oxide film 16 on a region used to form a highly doped layer is removed. Then, a silicon nitride film 17 is formed; the silicon nitride film 17 on a region to form a thick epitaxial layer is removed; after that, an etching operation is executed by making use of a remaining silicon nitride film 17a as a mask; an opening part is formed. Then, the silicon nitride film 17a is removed; the highly doped layer is formed by making use of a remaining silicon oxide film 16a as a mask; the remaining silicon oxide film 16a is removed; after that, an epitaxial layer is grown on the semiconductor substrate; its surface is flattened. Thereby, it is possible to simply form the epitaxial layer whose film thickness is different.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method of manufacturing a semiconductor device having a structure in which the epitaxial layer thickness is varied within the same chip depending on the use of the device.

(Example) Conventional technology Conventionally, when a high-voltage element and a low-voltage element are formed on one semiconductor substrate, the epitaxial layer in the high-voltage element forming area needs to be thickened according to the breakdown voltage in order to satisfy the characteristics. This has hindered the speeding up of low voltage devices. Therefore, as a method of forming a thick epitaxial layer only in the area where the high voltage withstand voltage element is formed, a method is used in which the semiconductor substrate under the formation of the high voltage withstand voltage element is etched. Then, epitaxial layers with different thicknesses were formed by growing epitaxial layers over the entire surface.

(c) Problems to be solved by the invention In order to form epitaxial layers with different thicknesses as described above, a semiconductor substrate is etched, a highly concentrated impurity layer is formed on the surface of the opening, and then a high concentration impurity layer is formed on the surface of the opening. The method of growing an epitaxial layer after filling the opening without growing an epitaxial layer and forming a highly concentrated impurity stone for forming a low breakdown voltage element requires multiple steps.

In addition, after etching the semiconductor substrate, a high concentration impurity layer is formed both under the formation of the high-voltage element and under the formation of the low-voltage element, and after growing an epitaxial layer on it, the surface of the epitaxial layer is flattened. There is also a method of forming epitaxial layers with different thicknesses, or because there are steps in the etched area of the semiconductor substrate, a photoresist can be uniformly applied using a photolithography process to selectively form a high aK impurity layer. Furthermore, even if the photoresist can be uniformly applied to the substrate surface, it is difficult to accurately expose the substrate surface having a step difference of several tens of microns.

(2) Means and Effects for Solving the Problems The present invention provides a method for manufacturing a semiconductor device in which epitaaxial layers having different thicknesses are formed on a semiconductor substrate of one conductivity type, and a silicon oxide film is formed on the semiconductor substrate. forming a silicon nitride film covering the semiconductor substrate and the remaining silicon oxide film to form a thick epitaxial layer. removing the silicon nitride film on the area to be removed and etching the semiconductor substrate using the remaining silicon nitride film as a mask to form an opening; A step of forming a highly concentrated impurity layer on the semiconductor substrate including the opening using the film as a mask, and after removing the remaining silicon oxide film, growing an epitaxial layer on the semiconductor substrate, and forming an epitaxial layer on the surface of the epitaxial layer. The present invention provides a method for manufacturing a semiconductor device, comprising a step of forming epitaxial layers having different thicknesses by planarization treatment.

That is, the present invention selectively etches a semiconductor substrate to form an opening, and when forming a high a degree impurity layer at least in the opening, after forming a mask for forming the high concentration impurity layer. In addition, we formed a mask for forming openings directly below this mask, and used this to form epitaxial layers with different thicknesses on the semiconductor substrate, so we could easily remove the mask after forming the openings. In addition to being able to easily form the high concentration impurity layer by a method such as ion implantation, it is no longer necessary to perform patterning after etching the semiconductor substrate to selectively form the high concentration impurity layer.

(e) Examples The present invention will be described in detail below based on embodiments shown in the figures.

Note that this invention is not limited by this.

In FIG. 2, the semiconductor device has a high breakdown voltage element region (hereinafter referred to as a first region) that has a thick epitaxial layer 3a.
A P-type silicon substrate l having an inverted trapezoidal opening 1a on F and a flat portion 1b on the surface other than the first region;
N° buried layer 2a arranged along a and flat part lb
A N buried layer 2b is selectively provided in a low breakdown voltage device region (hereinafter referred to as a second region) S having a shallow epitaxial layer 3b thereon, and a N buried layer 2a in an opening 1a is formed on the substrate l. an epitaxial layer 3b disposed through the N° buried layer 2b of the flat portion 1b and having a shallower layer thickness than the epitaxial layer 3a; high-voltage element 20 and the second
It mainly consists of a low breakdown voltage element section 21 disposed on the region S.

Further, in both element parts 20 and 2l, a P-well layer 6 and an N-well layer 7 are grown on the surfaces of epitaxial layers 3a and 3b, respectively, and a gate electrode made of polycrystalline silicon is formed on these well layers via an insulating film. It has 8. Further, 9 is an N° source/drain layer, IO is a P° source/drain layer, which penetrates the epitaxial layer 3b between the first and second @ regions to provide P′ isolation/! ! It has 4.

11 is an insulating film between the eyebrows, l2 is an electrode metal, and this electrode metal l2 and the N buried layer 2f of the opening 1a.
L is coupled through the N° drain layer 5.

The manufacturing method will be described below with reference to FIG.

First, as shown in FIG. 1(a), a silicon oxide film 16 and a photoresist film (not shown) are laminated on the entire surface of a silicon substrate 1 by oxidizing its surface, and then a mask having a predetermined pattern is formed. (not shown) in a predetermined region between the first region F and second region S and within the second region +
6a, remove the oxide film so that only the photorenost film remains
6 is etched, and the remaining photoresist film is removed to form a substrate 1 having an oxide film 16a between the first region and the second region and in predetermined regions within the second region.

Next, as shown in FIG. 1(b), after laminating silicon nitride [17 and photoresist @l8] on the entire surface of the substrate 1,
The photoresist film on the first region F is removed using a mask having a predetermined pattern, and the silicon nitride film is etched using this as a mask [see FIG. 1(c)]. Furthermore, the remaining photoresist film 18a is removed, and the first region F
In addition, a substrate l having a nitride film 17a is created. Subsequently, using the silicon enriched film 17a as a mask, the substrate 1 is subjected to KO treatment.
Perform anisotropic etching using H etc., and add 20μ to the first region.
A substrate l having an inverted trapezoidal opening 1a with a depth of about See figure (d)]. Thereafter, the silicon nitride film 17a is removed, and ions are implanted using the remaining oxide film 16 as a mask to create a substrate 1 having N0 buried layers 22L and 2b in the 11th region and predetermined regions in the second region, respectively. [See Figure 1(e)]. Then, the silicon oxide film 16a is removed, an epitaxial layer 3 is formed by epitaxial growth, and the surface of the epitaxial layer 3 is polished and planarized to create a substrate with a planarized surface [see FIG. E. Next, as shown in FIG. 2, a high breakdown voltage element 20 and a low breakdown voltage element 21 are formed on the first region and the second region via epitaxial layers 3a and 3b, respectively, by a conventional method.

Thereafter, the device structure shown in FIG. 2 is obtained using a well-known technique.

In this way, the high breakdown voltage element section 20 can be formed on the first region F with a deep epitaxial layer thickness, and the low breakdown voltage element section 2l can be formed on the second region S with a shallow epitaxial layer thickness.

As described above, in this embodiment, silicon oxide ffll6 is buttered in the area where the silicon substrate l is selectively etched to form the opening 1a, and silicon nitride is deposited covering the buttered silicon oxide film t6a. The film 17 is deposited, and then the silicon nitride film 17 is patterned, and the substrate 1 is anisotropically etched using this as a mask, so that the photo process for selectively forming the N° buried layer after etching the substrate is performed. No longer needed, oxide film 1
Using 6a as a mask, the N° buried layer can be easily formed by a method such as ion implantation, and the photo step of vacuuming the substrate surface after etching can be omitted.

FIG. 3 shows a device in which the structures of the high voltage element section and the low voltage element section are different.

In FIG. 3, 13 is the external base layer of the NPN transistor, 14 is the internal base layer thereof, and 15 is the emitter layer.Similar to the device obtained in the above embodiment, the high breakdown voltage device section 20a has an epitaxial layer thickness. The low breakdown voltage element 2+a is arranged above the thick FJ 3a, and the low breakdown voltage element 2+a is arranged above the thin layer 3b.

(F) Effects of the Invention According to the present invention, when selectively etching the semiconductor iIff to form an opening and forming a high concentration impurity layer at least in the opening, a mask for forming the high concentration impurity layer is used. After forming the mask, a mask for forming an opening was formed directly below the mask, and epitaxial layers with different thicknesses were formed on the semiconductor substrate. A high-concentration impurity layer can be easily formed by ion implantation or other methods by simply removing it, and there is no need to form a mask for forming a high-concentration impurity layer in a photolithography process after etching the semiconductor substrate, simplifying the process. This has the effect of improving reliability.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process explanatory diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are diagrams explanatory of the structure of an element obtained by the above embodiment. 2 1. &...Low breakdown voltage element, F...First region, S...Second region. ......P-type semiconductor substrate, a...opening, 1b...flat surface of substrate, λ, 2b...N゛buried layer,

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device in which epitaxial layers having different thicknesses are formed on a semiconductor substrate of one conductivity type, wherein a silicon oxide film is formed on the semiconductor substrate, and a highly concentrated impurity layer is formed on the semiconductor substrate. forming a silicon nitride film covering the semiconductor substrate and the remaining silicon oxide film, and forming the silicon nitride film on the region where a thick epitaxial layer is to be formed; and etching the semiconductor substrate using the remaining silicon nitride film as a mask to form an opening; After removing the silicon nitride film, etching the opening using the remaining silicon oxide film as a mask. After removing the remaining silicon oxide film, an epitaxial layer is grown on the semiconductor substrate, and the surface of the epitaxial layer is planarized to increase the film thickness. 1. A method for manufacturing a semiconductor device, comprising the steps of: forming epitaxial layers having different values.