JPH0340512B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor substrate, and particularly to a method for manufacturing a semiconductor substrate that has a silicon nitride layer therein and an impurity diffusion layer adjacent to the silicon nitride layer. It is about the method.

[Technical background of the invention and its problems] Generally, it is easy to form an insulating layer on the surface of a semiconductor substrate or to form an impurity diffusion layer from the surface inward. It is not easy to form an insulating layer or an impurity diffusion layer, and in particular, it is virtually impossible to form an insulating layer or an impurity diffusion layer with good reproducibility when buried deep from the surface of a semiconductor substrate using conventional techniques. It was hot.

However, with the recent development of semiconductor devices, there has been a demand for semiconductor substrates having an insulating layer or an impurity diffusion layer buried deep from the surface of the substrate.

[Object of the Invention] An object of the present invention is to provide a method for manufacturing a semiconductor substrate having an insulating layer and an impurity diffusion layer adjacent to the insulating layer inside the semiconductor substrate.

[Summary of the Invention] The method according to the present invention involves bonding a second semiconductor thin plate to a first semiconductor thin plate on which a silicon nitride layer has been formed and impurities introduced into the silicon nitride layer, and then thermal diffusion treatment is performed. By doing so, a semiconductor substrate having a silicon nitride layer and an impurity diffusion layer adjacent to the silicon nitride layer is manufactured. According to the method of the present invention, a semiconductor substrate having a silicon nitride layer and an impurity diffusion layer buried deep from the surface of the substrate can be manufactured with good reproducibility.

[Embodiments of the Invention] Examples in which the method of the present invention is applied to manufacturing a silicon semiconductor substrate will be described below with reference to FIGS. 1 to 3 of the accompanying drawings.

FIGS. 1A to 1F illustrate the method of the present invention as a process for manufacturing a silicon semiconductor substrate.

In this example, a first silicon nitride film (hereinafter abbreviated as SiN film) 2 is first formed on one surface of a first N-type silicon single crystal plate 1 by low pressure CVD. It is formed as shown in FIG. 1A. Next, as shown in FIG. 1B, a P-type impurity such as Ga is introduced into the SiN film 2 by, for example, ion implantation. Next, as shown in FIG. 1C, a second SiN film 3 is further deposited on the first SiN film 2 in the same manner as described above, and then the second SiN film 3 is deposited as shown in FIG. 1D. Finish the surface of the SiN film 3 to a mirror finish. In this case, the surface roughness of the mirror surface is set to 500 Å or less, and the mirror-finished surface is washed with clean water for several minutes. Spinner treatment at room temperature is suitable for this dehydration, and it is best to avoid heating and drying at temperatures above 100°C. This is because it is recognized that it is important for the next bonding to not completely remove the moisture adsorbed on the mirror surface.

On the other hand, a second N-type silicon single crystal plate 4 is prepared, and one surface of the silicon single crystal plate 4 is mirror-finished. In this case as well, the mirror-finished surface of the second silicon single crystal plate 4 is polished so that the surface roughness is 500 Å or less, and depending on the mirror-finished state,
H ₂ O ₂ −H ₂ SO ₄ mixture, then HF solution, then dilute HF
Pretreatment is performed with a liquid, followed by washing with water and dehydration as in the case of polishing the SiN film.

Next, the mirror surface of the second silicon single crystal plate 4 is brought into close contact with the mirror surface of the second SiN film 3 of the first silicon single crystal plate 1 at a temperature of 200° C. or higher, preferably.
After heat treatment at a temperature of 1000 to 1200℃, Fig. 1E
As shown in FIG. 2, a semiconductor substrate has two silicon single crystal plates 1 and 4 bonded to each other via a silicon nitride layer 5 (this is a combination of the first and second SiN films 2 and 3). Get 6. In this case, it is important to make direct contact between the two mirror surfaces without any foreign matter intervening, and it is best to do so in an atmosphere of class 1 or lower (class 1 means that there is only one piece of 0.5 μm dust in 1 ft ³ ). (a certain state).

Thereafter, when the semiconductor substrate 6 is subjected to thermal diffusion treatment at a high temperature of about 1200° C. for several hours, Ga is diffused into both sides of the silicon nitride layer 5 inside the semiconductor substrate 6, as shown in FIG. 1F. A semiconductor substrate 6 in which P-type impurity diffusion layers 7 are formed on both sides of the silicon nitride layer 5 is completed.

Note that although a semiconductor substrate made of a silicon single crystal plate is shown, other semiconductor substrates may be used. Further, impurities may be introduced into the silicon nitride film by any method, but by using ion implantation, an impurity diffusion layer can be formed in a controlled amount and with the best reproducibility.

FIGS. 2 and 3 show examples of semiconductor substrates manufactured using the method of the present invention.

In the semiconductor substrate 6A shown in FIG. 2, a silicon nitride layer 5A is formed, and an N-type impurity is introduced into the silicon nitride layer 5A, so that an N-type high concentration layer of impurities is diffused on both sides of the silicon nitride layer 5A. This is the layer 7A formed thereon.

Further, the semiconductor substrate 6B shown in FIG. 3 is manufactured by forming a silicon nitride layer 5A only on a part of the surface of the first semiconductor thin plate 1 and introducing an N-type impurity into the silicon nitride layer 5A. Impurity diffusion layers 7A of N-type high concentration layer are provided on both sides of layer 5A.
is formed.

[Effects of the Invention] As described above, according to the method of the present invention, a semiconductor substrate having a silicon nitride layer and an impurity diffusion layer adjacent to the silicon nitride layer can be manufactured. It has become possible to manufacture various semiconductor devices that were previously difficult to manufacture.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the main steps of the method of the present invention in cross section of a semiconductor, and FIGS. 2 and 3 show examples of semiconductor substrates that can be manufactured by the method of the present invention shown in FIG. This is a diagram. 1, 4... Silicon single crystal plate, 2, 3... Silicon nitride film, 5, 5A... Silicon nitride layer, 6,
6A, 6B... Semiconductor substrate, 7, 7A... Impurity diffusion layer.

Claims (1)

[Claims] 1. A step of forming a first silicon nitride film on one surface of a first semiconductor thin plate, a step of introducing an impurity into the first silicon nitride film, and a step of forming the first silicon nitride film. forming a second silicon nitride film on the surface of the film; mirror-finishing the surface of the second silicon nitride film; and polishing the surface of the second semiconductor thin plate with one surface mirror-finished. forming a single semiconductor substrate by bonding the first and second semiconductor thin plates by performing heat treatment while the first semiconductor thin plate is in close contact with the second silicon nitride film; and forming impurity diffusion layers adjacent to both sides of the silicon nitride layer by subjecting the substrate to thermal diffusion treatment, the method includes a silicon nitride layer therein and an impurity diffusion layer adjacent to the silicon nitride layer. A method for manufacturing a semiconductor substrate. 2. The method of manufacturing a semiconductor substrate according to claim 1, wherein the step of introducing impurities into the first silicon nitride film is performed by ion implantation technology.