JPH02214163A - Manufacture of thyristor - Google Patents

Abstract

PURPOSE:To sufficiently recover a lifetime and to prevent an ON voltage from being increased by a method wherein an oxide film, on one face, to be used as a mask is removed selectively, also an oxide film on the other face is removed and phosphorus is deposited. CONSTITUTION:An oxide film 2 of a silicon wafer 1 of a P-n-P structure is formed again; a window is opened in an oxide film 2 on the side of one main face by using a photolithographic technique; an oxide film 2 on the side of the other main face is removed. In order to form N-type semiconductor regions in P-type semiconductor regions on the two main faces, phosphorus is diffused including a driving operation of the phosphorus in such a way that the phosphorus having surface concentration of 10<21>/cm<2> or higher is deposited and that the surface concentration after the driving operation is 10<21>/cm<2> or higher; in addition, a phosphorus diffusion layer on the side of the other main face is removed by a lapping operation or the like. Thereby, a lifetime of the silicon wafer 1 after the phosphorus has been driven is recovered to a level identical to an initial wafer; it is possible to prevent an ON voltage from being increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a diristor, and particularly to improving the lifetime of silicon wafers.

[Conventional technology]

Conventionally, the commonly known thyristor is P-n-P-n
It has a 4m structure.

The third method for manufacturing a thyristor with this conventional four-layer structure
As shown in the figure. First, in order to obtain the target breakdown voltage, A
A P-type dopant of I or Ga is diffused to have a predetermined surface concentration and junction depth to form a P-n-P structure [No. 31'3b]. Next, the oxide film 2 is reattached to the silicon wafer 1, and a window is opened in the oxide film 2 on one main surface side by photolithography (FIG. 3C). Next, in order to form a P-n-P-n four-layer structure of the thyristor, the oxide film 2 with the window opened and the oxide film 2 on the entire other main surface.
Deposit phosphorus using the mask as a mask. Next, the oxide film 2 used as a mask is removed and phosphorus is driven to diffuse phosphorus (FIG. 3d). In this way,
A PnPn4M thyristor structure was manufactured.

FIG. 2 is a curve diagram (solid line B) showing the state of lifetime change of a silicon wafer in each process when this conventional manufacturing method is used. The lifetime of the silicon wafer after the phosphorus drive is completed has not recovered to the level of the initial wafer.

[Problem to be solved by the invention]

Conventional thyristor manufacturing methods have the above-mentioned structure, which causes a reduction in the lifetime of the silicon wafer due to the diffusion of P-type dopants such as sGa and the formation of oxide films. By deposit. Although the lifetime can be recovered by using this method, this method is not sufficient.
Thickness of n-paste layer of thyristor, L: lifetime in n-paste layer] There was a problem in that the on-voltage vT of the thyristor became high.

This invention was made to solve the above-mentioned problems, and aims to provide a method for manufacturing a thyristor that sufficiently restores the lifetime and prevents the on-voltage from becoming high.

[Means to solve the problem]

The method for manufacturing a thyristor according to the present invention is such that the oxide film on one main surface used as a mask is selectively removed, and the oxide film on the other main surface is also removed to perform phosphorus deposition. It is.

[Effect]

In the method of manufacturing a thyristor according to the present invention, phosphorus is deposited on both sides, so that gettering is more effective and the lifetime of the silicon wafer is fully recovered.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained regarding a leap.

FIG. 1 is a sectional view showing a method for manufacturing a thyristor according to an embodiment of the present invention. Look at it the same way as the manufacturing process. After the process shown in FIG. 1(b), the oxide film 2 of this silicon wafer 1 is reattached, and a window is opened on the oxide film 2 of <1111 on one main surface by photolithography, and at the same time, the other main surface is The side film 2 is removed (FIG. 1C). next,
A silicon wafer 1 is subjected to phosphorus deposition. On this occasion,
The oxide film 2 on the other main surface side has been removed, increasing the area on which phosphorus is deposited on the silicon wafer 1, effectively sucking out impurities due to the gettering effect, and sufficiently recovering the lifetime. . Next, after removing the oxide film 2 used as a mask, phosphorus is diffused by driving phosphorus (FIG. 1d). Furthermore, P −n
In order to obtain a -P-n 4 m structure, the phosphorus diffusion layer on the other main surface side is removed by lapping or the like (FIG. 1e).

As described above, the thyristor P-n-P-n
Fabricate a four-circle structure.

FIG. 2 shows the state of lifetime fluctuation of a silicon wafer when the manufacturing method of this embodiment is used (broken HA). When the manufacturing method of this embodiment is used, the lifetime of the silicon wafer after completion of the phosphorus drive is recovered to the same level as that of the initial wafer. This can prevent the pressure from increasing when the switch is on.

〔Effect of the invention〕

According to the present invention, as described above, the gettering effect due to phosphorus deposition is utilized to the fullest and the lifetime is restored to the initial level, thereby making it possible to suppress the on-voltage to a low level.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a method for manufacturing a thyristor according to an embodiment of the present invention, FIG. 2 is a curve diagram showing variations in the lifetime of a silicon wafer according to the thyristor manufacturing process common to the conventional method and the present invention, and FIG. 1 is a cross-sectional view showing a conventional method of manufacturing a thyristor. In the figure, l is a silicon wafer and 2 is an oxide film. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] Forming a P-type semiconductor region by diffusing P-type impurities into two opposing main surfaces of an N-type semiconductor substrate, and simultaneously forming an N-type semiconductor region in the P-type semiconductor regions on the two main surfaces. a phosphorus diffusion step including a phosphorus drive having a surface concentration of 10^2^1/cm^3 or more to achieve a phosphorus deposition and a phosphorus drive such that the surface concentration after driving becomes 10^2^1/cm^3 or more; A method for manufacturing a thyristor, comprising the step of removing the N-type semiconductor region diffused into the P-type semiconductor region on one main surface.