JPS5912020B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for preventing defects due to emitter-collector shorting at the emitter end, which is a problem when the base diffusion region of a transistor part is made smaller for the purpose of increasing the speed and density of a semiconductor device. It is related to.

In order to make a transistor with a fixed emitter area smaller and faster, it is necessary to make the base region smaller.

In a general transistor, the emitter region 2 is completely contained within the base region 1 as shown in FIG. It is being In this structure, since the two sides of the emitter are in contact with the periphery of the base region, the excess area in the vertical direction can be completely eliminated. To obtain such a structure, as shown in Figure 2, after diffusing the base region 1, photoetching is performed using an emitter pattern 3 that is 15 times larger than the base region, and the area outside the base and on the base is etched. A method is used in which a hole for emitter diffusion is formed only on the base by taking advantage of differences in the thickness of the oxide film.

20. FIG. 3 is a sectional view corresponding to the A and N sections in FIG. 2.

After selectively oxidizing parts other than the base area. The base layer 7 is diffused, the oxide film 5 is etched using the photoresist film 4, and the emitter layer 8 is diffused. 25 During the base diffusion, the oxide film 5 had spread to the area indicated by the dotted line, so the lateral diffusion under the oxide film started from point B and reached approximately 0.8 times the depth in the depth direction. Spread.

On the other hand, since the emitter diffusion starts from the point C that retreated during emitter photoetching, the base width at the end is narrower than in the depth direction, resulting in a short circuit between the emitter layer 8 and the collector layer 6, resulting in failure There is a huge possibility that this will happen. The present invention solves this drawback by providing a deep diffusion layer around the base region, making it possible to manufacture 35 semiconductor devices with good characteristics.

The present invention will be explained in detail below using examples.

FIGS. 4a to 4e show the manufacturing process of a transistor according to the present invention.

a is n-type 0.5Ω=, after forming a thermal oxide film 10 at 500× on the surface of the (100) plane silicon wafer 9, a silicon nitride (Si3N,) film is formed by the reaction of monosilane (SiH, ) and ammonia 3). 11 to a thickness of 1000A, and on top of that a SiO2 film 12 made of monosilane with a thickness of 50A.
This is the area where the coating was applied to a thickness of 00A. Figure b shows a predetermined pattern formed on the film using photoetching technology. First, a photoresist film 13 is formed using a predetermined mask, and then the SiO2 film 13 is formed using this film as a mask.
Etch 2. As an etching solution, one part hydrofluoric acid (50%) and one part neutral ammonium fluoride solution (40%) were used.
They were mixed at a ratio of 6:1. Subsequently, the silicon nitride film 11 was etched with a spacing of 20 m in Freon gas plasma. In addition. When hot phosphoric acid is used to etch the silicon nitride film, the photoresist film is also removed, but when plasma etching is performed, it is possible to leave the photoresist film. After etching the silicon nitride film, the side surfaces of the SiO2 film 12 are etched using the hydrofluoric acid-based etching solution using the photoresist film 13 as a mask, thereby forming a small SiO2 film once on the silicon nitride film. Specifically, it is etched for 4 minutes using the above etching solution to make it 2 μm smaller than the silicon nitride film. Note that during this etching, the thermal oxide film 10 on the silicon nitride film 11 is also etched at the same time, but the etching speed is slow (χ1000X/=
), the lateral spread D is very small. In Figure c, after removing the photoresist film 13, the silicon surface was etched to a depth of 0.7 μm in a potassium hydroxide solution (40%) at 25°C, and then etched in oxygen containing water vapor at 1000°C for 16 hours. This is the area where a thermal oxide film 14 of 1.8 μm was formed by oxidation.

After oxidation, the silicon nitride film 11 used as an oxidation mask is
By etching using the iO2 film 12 as a mask, only the exposed area of the silicon nitride film around the pattern can be removed. Next, the thermal oxide film 10 underneath is etched. When the boron diffusion layer 15 is formed, the shape becomes as shown in the figure d.
FIG. 4e shows the SlO2 film 12, the silicon nitride film 11. The thermal oxide film 10 is removed. The paste layer 16 and emitter layer 17 are formed by diffusion of poron and phosphorus using a conventional method.

After this, although not shown in the figure, by forming electrodes, a transistor whose periphery is protected by the deep diffusion layer 15 can be formed. Note that here, to simplify the explanation, we have described the case of a single transistor. Integrated circuit (
It goes without saying that the present invention can also be applied to engineering C) and large-scale integrated circuits (LSI).

[Brief explanation of drawings]

Figure 1 is a plan view of a conventional transistor. Figure 2,
Figure 3 is a plan view and a cross-sectional view to explain the problems of the conventional method. FIGS. 4a-4e are cross-sectional views for explaining the present invention.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device including the following steps (1) A method for manufacturing a semiconductor device including the following steps: (1) forming a thermal oxide film, a silicon nitride film and an SiO
_2 The process of laminating and depositing films. (2) Using a mask having a desired shape, the SiO
A step of removing the exposed portions of the _2 film and the silicon nitride film. (3) A step of removing the exposed portion of the thermal oxide film and side-etching the SiO_2 film. (4) A step of oxidizing the surface of the silicon substrate using the silicon nitride film to form a thick thermal oxide film. (5) Above S
Using the iO_2 film as a mask, the exposed parts of the silicon nitride film and the thermal oxide film are removed to expose the surface of the silicon substrate, and then impurities are introduced into the silicon substrate from the exposed parts to form a deep layer. Step of forming a diffusion layer. (6) After removing the SiO_2 film, the silicon nitride film, and the thermal oxide film, a step of sequentially introducing impurities having different conductivity types into the exposed portion of the silicon substrate to form a base and an emitter.