JPH0567626A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide the manufacturing method for super-high frequency bipolar transistor. CONSTITUTION:Non-doped polysilicon 6 is deposited by bringing it into the low temperature state of about 500 deg.C, and then a base contact part is formed by conducting a work on a T-shaped emitter electrode 8 conjointly using a reactive dry etching and a wet etching. As a result, the manufacturing process can be cut down sharply, the T-shaped emitter electrode can be formed uniformly and microscopically in the surface of a wafer, and besides, defective appearance and the unsatisfactory characteristics resulting from it are not generated. A highly efficient bipolar transistor, especially for ultra-high frequency, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device capable of manufacturing a high performance bipolar transistor for high frequency.

[0002]

2. Description of the Related Art A conventional bipolar transistor in which an emitter portion formed on a silicon substrate has a two-layer structure of a doped silicon film and a non-doped silicon film, and a base contact hole and an emitter electrode are formed by self-alignment. The manufacturing method will be described with reference to FIG.

2A to 2C are vertical cross-sectional views in order of steps showing a conventional method for manufacturing a bipolar transistor. First, as shown in step A, an oxide film 2 provided on a silicon substrate 1 is selectively formed. Then, a base region 3 is formed by performing base ion implantation. Then, in order to form the emitter 4 (see step C), the doped polysilicon 5 and the non-doped polysilicon 6 are grown.

Next, as shown in step B, the photoresist 7 is used as a mask to ion-implant the non-doped polysilicon 6 layer to facilitate etching, and a hydrofluoric acid / nitric acid-based wet etch is used to form a T-shape. Then, the T-shaped emitter electrode 8 is formed. Thereafter, as shown in step C, a CVD oxide film 9 ′ is deposited on the T-shaped emitter electrode 8 and heat-treated at a high temperature to remove impurities in the doped polysilicon 5 from the silicon substrate 1. The emitter 4 is formed by diffusing into the base region 3. At this time, the impurities in the doped polysilicon 5 are also diffused into the non-doped layer 6.

Next, the photoresist 7 is used to open the base contact portion, and the base contact portion 10 is formed by ion implantation (step D). Then, the photoresist 7 is processed again. , Non-doped polysilicon 6
The CVD oxide film 9'on the layer is removed (step E).

[0006]

The conventional method of manufacturing a semiconductor device described above has a drawback that it is not suitable for miniaturization to obtain high frequency characteristics. That is, since the non-doped polysilicon 6 is grown at a high temperature of about 750 ° C. like the doped polysilicon 5, during this growth,
Since the impurities in the doped polysilicon 5 are diffused into the non-doped polysilicon 6, it is difficult to process the T-shape during wet etching, and the thickness of each element is different. T-shaped part is missing in the
However, there are problems such as the disappearance of the layer.

A defective appearance occurs due to the lack of the T-shaped portion, the lack of the non-doped layer, and the like, and there are many characteristic defects associated with the defective appearance, and the non-defective rate in the wafer. However, the manufacturing process is long, and fine processing is difficult.

An object of the present invention is to provide a method of manufacturing a semiconductor device that solves the above problems and drawbacks. Specifically, the manufacturing process can be greatly shortened, and the manufacturing method is uniform and fine. It is an object of the present invention to provide a method of manufacturing a bipolar transistor for high frequency, which can form an emitter electrode, reduce appearance defects and characteristic defects, and has higher performance.

[0009]

According to the present invention, non-doped polysilicon is deposited at a temperature lower than that of doped silicon, and T-shaped emitter electrode processing is performed by using both reactive dry etching and wet etching. However, it is characterized in that the base contact portion is formed by self-alignment, which solves the problems and drawbacks in the conventional method and achieves the above object.

That is, according to the present invention, (1) a step of forming an oxide film formed on a silicon substrate to form a base layer, (2) a base silicon film on the base layer, A step of sequentially forming a non-doped silicon film and a first insulating film that grow at a lower temperature than the doped silicon film, (3) the non-doped silicon film
After etching each silicon film by reactive ion etching with a mask selectively formed on the silicon oxide film and the first insulating film, the remaining film is wet-etched with hydrofluoric acid or nitric acid to form an emitter electrode. Forming process, (4)
Depositing a second insulating film on each of the processed silicon films, and diffusing impurities from the emitter electrode into the base layer to form an emitter layer, (5) by reactive ion etching, Etching the second insulating film to open a base contact and at the same time leave the second insulating film on the side wall of the silicon film; (6) forming a base contact layer by ion implantation. And a method for manufacturing a semiconductor device.

The present invention will be described in detail below. The method of manufacturing a semiconductor device according to the present invention is a method of growing a non-doped layer.
It is carried out at a temperature lower than that of the doped layer, which is characterized in that the impurities in the doped polysilicon film are prevented from diffusing into the non-doped layer. To specifically explain this point, in the present invention, first, the growth of the doped polysilicon film is performed at about 750 ° C., and then the growth of the non-doped silicon film is performed at about 500 ° C. or less. preferable. This prevents impurities in the doped layer from diffusing into the non-doped layer during the growth of the non-doped layer, and, as a result, together with the subsequent etching step, the T Defects such as a lack of character portions and a lack of non-doped layers can be eliminated.

Next, the polysilicon film is etched by reactive ion etching using the first insulating film and the photoresist as a mask, and the thickness of the residual film and the doped polysilicon of the T-shaped emitter electrode portion is adjusted. By adjusting the etching with wet etching, the inside of the wafer can be made uniform.
Moreover, it can be finely processed. Then, a second insulating film is deposited on the silicon substrate, and the insulating film is removed by reactive ion etching to open a base contact portion and form an insulating film on the side wall of the T-shaped emitter electrode portion. It will remain.

Ions are implanted to form the base contact portion. However, since the insulating film remains on the non-doped layer, the non-doped layer is not ion-implanted.
A base contact portion is formed. After that, the insulating film of the non-doped layer is removed with hydrofluoric acid. The present invention is to manufacture a semiconductor device by the above-mentioned steps, whereby a high performance bipolar transistor, especially for a super high frequency, can be manufactured.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to FIG. (Embodiment 1) FIG. 1 is a vertical cross-sectional view in order of the steps of a method for manufacturing a semiconductor device, showing an embodiment of the present invention. First, the oxide film 2 provided on the silicon substrate 1 is opened, and impurities are diffused to form the base region 3. After that, the emitter 4 (process C
(See FIG. 2), the doped polysilicon 5 is deposited at about 750 ° C., the non-doped polysilicon 6 is deposited at about 500 ° C., and the first CVD oxide film 9 is sequentially deposited (step) A).

Next, as shown in step B, using photoresist 7, the deposited film is selectively etched by reactive ion etching until the doped polysilicon 5 remains thin. At this time, in order to adjust the thickness of the doped polysilicon 5, control is performed by wet etching using hydrofluoric acid or nitric acid. At this time, since the non-doped polysilicon 6 does not contain impurities, its shape does not collapse, and it serves as a sufficient mask to obtain a uniform T-shaped emitter electrode 8.

Thereafter, the photoresist 7 is removed, the second CVD oxide film 11 is deposited on the entire surface of the silicon substrate 1, and the impurities in the doped polysilicon 5 are removed by high temperature heat treatment. Medium and silicon substrate 1
To form an emitter 4 (step C).

Next, as shown in step D, the second CVD oxide film 11 is etched by reactive ion etching to open the base contact portion 10. At this time, the second CVD oxide film 11 is left on the sidewall of the T-shaped emitter electrode 8, and the emitter electrode 8 and the base contact portion 10 are separated. Then, the first CVD oxide film 9 and the second CV remaining on the non-doped polysilicon 6 are formed.
Ion implantation is performed using the D oxide film 11 as a mask to form the base contact portion 10. Then, the first CVD oxide film and the second CVD oxide film 11 on the non-doped polysilicon 6 are removed by hydrofluoric acid-based wet etching to form the T-shaped emitter electrode 8 shown in step D.

(Embodiment 2) In Embodiment 1, a CVD oxide film is used as an insulating film, but in Embodiment 2, a CVD nitride film is used instead of this oxide film, and steps A to D in FIG. Then, a T-shaped emitter electrode 8 was formed. Even when this nitride film was used, it was possible to obtain a film having excellent workability and insulating properties, as in Example 1.

In Examples 1 and 2, the processed shape can be changed by selecting the thickness of each deposited film. Further, when the non-doped polysilicon 6 and the doped polysilicon 5 are processed, a CVD oxide film or a CVD nitride film is deposited immediately after dry etching, and the non-doped polysilicon is removed by dry etching. By performing wet etching of the doped polysilicon while leaving the CVD oxide film or the CVD nitride film on the side wall of 6, the processing accuracy is further improved.

[0020]

As described in detail above, according to the present invention, non-doped polysilicon is deposited at a temperature lower than that of doped silicon, and T-shaped emitter electrode processing is performed by reactive dry etching and wet etching. It is also characterized in that the base contact portion is formed by self-alignment in combination with this, which makes it possible to significantly shorten the manufacturing process as compared with the conventional method, and to reduce the T The V-shaped emitter electrode can be formed uniformly and finely, and further, there is a remarkable effect that appearance defects and accompanying characteristic defects do not occur. Further, according to the present invention, it is possible to provide a bipolar transistor having high performance, especially for super high frequency.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view in order of the steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

2A to 2D are vertical cross-sectional views in order of the steps, showing a conventional method for manufacturing a bipolar transistor.

[Description of Reference Signs] 1 silicon substrate 2 oxide film 3 base region 4 emitter 5 doped polysilicon 6 non-doped polysilicon 7 photoresist 8 T-shaped emitter electrode 9 first CVD oxide film 9'CVD oxidation Film 10 Base contact part 11 Second CVD oxide film

Claims (3)

[Claims] 1. A step of forming a base layer by opening an oxide film provided on a silicon substrate, and (2) a doped silicon film and the doped silicon film on the base layer. A step of sequentially forming a non-doped silicon film and a first insulating film that grow at a lower temperature, (3) on the non-doped silicon film and the first insulating film,
A step of forming the emitter electrode by performing wet etching of the residual film with hydrofluoric acid or nitric acid after etching each silicon film by reactive ion etching with the mask selectively formed, (4) Each of the processed A step of depositing a second insulating film on the silicon film and then diffusing impurities from the emitter electrode into the base layer to form an emitter layer, (5) the second insulating film by reactive ion etching Are etched to open the base contact and at the same time leave the second insulating film on the side wall of the silicon film, and (6) forming a base contact layer by ion implantation. A method of manufacturing a semiconductor device, which is characterized. 2. The manufacturing of a semiconductor device according to claim 1, wherein the doped silicon film formed on the base layer grows at about 750 ° C., while the non-doped silicon film grows at about 500 ° C. or less. Method. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second insulating films are a CVD oxide film or a CVD nitride film.