JPS5917845B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device that obtains a highly concentrated and shallow impurity diffusion layer.

Conventionally, when zinc is diffused into a □-V group compound semiconductor, for example in the manufacture of light emitting diodes, the following steps have been taken to increase luminous efficiency.

First, a deep, low-concentration diffusion layer is created by diffusing impurities through a silicon oxide film. Next, in order to reduce the contact resistance with the electrode metal and the sheet resistance of the diffusion layer,
By removing the silicon oxide film and directly diffusing impurities,
Forms a shallow, highly concentrated additional diffusion layer on the surface. However, this method has the following drawbacks. 1st
Second, in order to make the additional diffusion layer shallow, diffusion that does not involve the silicon oxide film has a high diffusion rate and requires a very short diffusion time, which is difficult to control. Second, the 10 surface is damaged due to direct high concentration diffusion in the bare area. The additional diffusion layer must be subjected to chemical etching in order to make it shallow and to remove damage to the surface, but the determination of the thickness of the additional diffusion layer by chemical etching causes large variations. 15 The present invention provides a solution to the above-mentioned problems.

The present invention will be explained below with reference to the drawings. An oxide film 2 is formed on the surface of a semiconductor substrate 1 (FIG. 1), and after this is heat-treated in an atmosphere containing hydrogen (FIG. 2), impurities are diffused through the oxide film 2. 3 is the diffusion/o layer (Figure 3).

Alternatively, this method is used to further diffuse impurities into a layer in which impurities have been previously diffused to a low concentration. According to the present invention, the impurity diffusion rate in the oxide film is increased by heat treatment in a hydrogen stream, so that a sufficiently high surface concentration can be obtained even by the diffusion method through the oxide film. In this case, since it is covered with an oxide film, there is little surface damage. 2 to 40 again
Since the diffusion takes a long time, it is easy to control the thickness of the shallow diffusion layer. Furthermore, this eliminates the need for chemical etching of the surface diffusion layer. Note that if the heat treatment temperature is too low, the impurity will not diffuse into the oxide film, and if it is too high, the interface with the oxide film will be destroyed, making it difficult to control the impurity diffusion rate.

Therefore, the optimum temperature range is 600°C to 1000°C. (5) Examples of the present invention will be described below.

Example l A silicon oxide film was formed on the surface of a silicon-doped n-type GaAs (impurity concentration 6 x 1017/Cd) substrate to a thickness of 1,000 mm, and was heated at 800°C in a hydrogen stream at 51/Mm for 1 hour. After the treatment, zinc arsenide ZnAs is placed in a quartz ampoule.
Vacuum-seal the container together with the second diffusion source.

Diffusion at 850° C. for 4 hours resulted in a 2 μm p-type region in the semiconductor.

After removing the silicon oxide film, a diameter of 10 mm is placed on the surface of the p-type region.
Attach a 0μ gold electrode to the center, 0.5m1L x 0.5mm
We fabricated a mesa-shaped infrared light emitting diode with a size of . The pattern of light emission examined with the vidicon is 80 mA from an input current of 20 mA.
Up to mA, light was emitted almost uniformly over the entire surface. From this, it can be seen that the sheet resistance of the p-type layer due to this diffusion is sufficiently small, and the injected current is uniformly distributed over the entire surface of the diode. Conventionally, zinc has been diffused through a silicon oxide film using Zn/Ga (an alloy of zinc and gallium) as a diffusion source, but in this diffusion layer, the current injected from the electrode is not distributed over the entire surface of the diode. Concentrates near the electrode.

On the other hand, the zinc diffusion layer formed by this method is
It can be seen that the layer has a sufficiently high concentration to reduce the sheet resistance. Example 2 Silicon-doped n-type GaAs
(Impurity concentration 6×1017/Cril) On the substrate surface,
A silicon oxide film is formed and vacuum sealed together with Zn (an alloy of zinc and gallium) in a quartz ampoule.

After performing the diffusion at 850°C for 16 hours, the silicon oxide film was reattached, and in the same manner as in Example 1, zinc was diffused through the silicon oxide film that had undergone hydrogen treatment to obtain a mesa-shaped infrared light emitting diode. Ta.

The characteristics of the diode were similar to the results of Example 1, with uniform light emission over the entire surface. Conventionally, after zinc diffusion is performed using Zn/Ga (alloy of zinc and gallium) as a diffusion source, the silicon oxide film is removed, and zinc diffusion is performed using zinc arsenide as a diffusion source while the substrate is bare. A diode was obtained by forming a concentration diffusion layer, but in this case, it was difficult to control the thickness of the diffusion layer because the time for high concentration diffusion was short.

In order to obtain the desired thickness, chemical etching was used, but this resulted in variations; too much etching led to light emission in the local area near the electrode, while insufficient etching led to light absorption in the highly concentrated diffusion layer. A problem occurred. Example 3 As in Example 2, Zn/Ga (zinc and gallium) was first selectively deposited on silicon-doped n-type GaAs (impurity concentration: 6 x 1017 impurities/Cd) using a nitride film and a silicon oxide film as diffusion masks. After performing zinc diffusion using a silicon oxide film (alloy), a silicon oxide film was reapplied, hydrogen treatment was performed, and zinc arsenide was used as a diffusion source to further perform zinc diffusion to obtain a planar type infrared light emitting diode.

The diode emitted light almost uniformly over the entire surface up to an input current of 20 mA to 80 mA. As explained above, according to the present invention, the impurity diffusion rate in the oxide film is increased by heat treatment in a hydrogen stream, so that a sufficiently high surface concentration can be obtained even by the diffusion method through the oxide film. .

Furthermore, since it is covered with an oxide film, there is less surface damage.
Furthermore, since the diffusion is for a long time of 2 to 40 hours, it is easy to control the thickness of the shallow diffusion layer. This therefore eliminates the need for chemical etching of the surface diffusion layer.

[Brief explanation of the drawing]

1 to 3 are process sectional views showing one embodiment of the present invention. 1...N-type GaAs substrate, 2...Silicon oxide film, 3...P+ type diffusion region.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, which comprises heat-treating a semiconductor substrate having an oxide film formed on its surface in an atmosphere containing hydrogen, and then diffusing impurities from a gas phase through the oxide film.