JPS6317332B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a semiconductor device.

In a method of manufacturing a semiconductor device, brazing an electrode metal to a Si substrate having an n-type diffusion layer on the surface has conventionally been carried out as shown in FIG. In FIG. 1, first, an Al vapor deposited film 2 is formed on the surface of a Si substrate 1, and then a vapor deposited film 3 made of an element that forms a eutectic with Al (for example, Si, Ge) is further formed on the upper surface. After that, this vapor deposited film 3 and the electrode metal 4
(For example, Mo, W) are heat-bonded. In order to obtain good adhesion between the vapor deposited film 3 and the electrode metal 4 using this conventional method, it was necessary to raise the heating bonding temperature to at least 550° C. or higher. However, when the heating bonding temperature is increased to 550℃ or higher,
Since the Si element on the surface of the Si substrate 1 precipitates at the interface between the electrode metal and the brazing material, and Al diffuses into the Si substrate 1, an inversion layer (due to P type) is formed on the boundary layer surface, resulting in a good condition. A proper ohmic junction is no longer formed. For this reason, there was a drawback that the forward voltage drop increased.

This invention was made in view of the above circumstances, and since Al and Ge are simultaneously vapor-deposited on the Si substrate and the electrode metal, thermal bonding is possible at a temperature below the melting point of the composition in the Al-Ge2 element phase diagram. It is an object of the present invention to provide a method for manufacturing a semiconductor device that enables the formation of a good ohmic junction.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 11 is a Si substrate having a thin n-type diffusion layer on its surface, and 12 is an electrode metal bonded to the Si substrate 11 by brazing. Al and Ge are simultaneously deposited on the surfaces of the Si substrate 11 and the electrode metal 12 in the following manner. This can be done by evaporating Al and Ge separately and using a mixed vapor to deposit them, or by electron beam evaporation using an Al-Ge alloy as a deposition source under an appropriate accelerating voltage. . When Al and Ge are simultaneously deposited on the surfaces of the Si substrate 11 and the electrode metal 12 in this way, the AlGe deposited film 1 is distributed so that finer Ge is distributed than the Al-Ge eutectic obtained by normal heat treatment.
3a and 13b are formed. In the phase diagram, the composition of the Al-Ge deposited films 13a and 13b is such that the Al primary crystal and the Al-Ge eutectic phase coexist.
30 atm% (atomic percent) can be applied as brazing material. In addition, considering thermal resistance and forward voltage drop, the optimum composition is Ge 15 to 25 atm%, and the brazing temperature at this time is 450 to 550℃ in an inert gas atmosphere, hydrogen gas atmosphere, or vacuum. It becomes possible. This temperature is approximately
This shows that brazing is possible at temperatures as low as nearly 100℃.

Figure 3 shows the surface of a P-type Si substrate uniformly doped with B (boron) at a concentration of 10 ¹⁴ /cm ^2.The surface concentration of P (phosphorous) is 10 ²⁰ /cm ² , the depth is 10μ, and the junction area is is 1
cm ² , forming a thin n-type diffusion layer (N ⁺ in Figure 3) on the surface, and further forming a B diffusion layer 10 ¹⁹ /cm ² to a depth of 10μ to make ohmic contact on the back surface. (P ⁺ in FIG. 3) is formed and is an example of a diode which is alloy-bonded with the anode W electrode. In a diode manufactured using the conventional method, in which Al and Ge are vapor-deposited in two stages on the n-type surface of the diode formed as shown in Figure 3, and the cathode W electrode is heated and bonded at 600°C, the forward voltage drop (V _F ) current is 300A
When flowing, it becomes 3-5V. However, with the method of simultaneous vapor deposition of Al-Ge as in this invention, (Ge is 20atm
%) of the present invention obtained by heating bonding in an _Ar atmosphere at 500° C., a V _F of 1.2 to 1.8 V, which is extremely low compared to the conventional method, was obtained.

As described above, according to the present invention, since Al and Ge are simultaneously vapor-deposited on the Si substrate and the electrode metal, the brazing temperature can be lowered, and the Al- Reactions between Si can be suppressed to a smaller level than in conventional methods. Further, since the forward voltage drop can be reduced and the Al% of Al-Ge can be increased, the contact resistance can be reduced. In addition to the above, compared to conventional brazing methods, only one vapor deposition process is required;
There are advantages such as the process can be simplified.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram illustrating a conventional method of manufacturing a semiconductor device, FIG. 2 is an explanatory diagram illustrating an embodiment of the present invention, and FIG. 3 is an explanatory diagram showing an example of manufacturing a diode. 11...Si substrate, 12...electrode metal, 13a,
13b...Al-Ge...deposited film.

Claims (1)

[Claims] 1. In a method of brazing a Si substrate having an n-type diffusion layer on the surface and an electrode metal, Al and Ge are simultaneously deposited on the Si substrate and the electrode metal to form an Al-Ge deposited film, and the composition of the deposited film is determined. The brazing temperature between the Si substrate and the electrode metal is set to be 400°C to 600°C, and the brazing atmosphere is inert gas, hydrogen gas, or vacuum. A method for manufacturing a semiconductor device, characterized in that: