JPS6355207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of introducing atoms into a -group compound semiconductor substrate such as GaP, GaAs, GaAsP, GaAlAs, etc., which can control the conductivity type or conductivity of the substrate.

That is, the present invention provides acceptor impurity atoms such as Zn and Cd, S,
It relates to a method of introducing donor impurity atoms such as Se.

The present invention will be explained using a method of introducing Zn into a GaP substrate as a typical example of these methods.

As a conventional technique to be compared with the present invention, a method will be described in which ZnP ₂ is used as a diffusion source and the n-type GaP substrate is converted to a p-type from the surface to a depth of approximately 10 μm. In this method, 20 mg of well-polished and chemically etched GaP and ZnP ₂ powders are vacuum sealed in a 100 c.c. quartz ampoule and heat treated at 750°C for 16 hours.
In this way, the donor concentration of the n-type GaP substrate is 3
×10 ¹⁷ cm ^-3 , approximately
Zn diffuses to a depth of 10 μm and converts to p-type. However, this method requires vacuum sealing in a quartz ampoule, and of course expensive quartz ampoules cannot be reused, and considering mass production, vacuum sealing of quartz ampoules requires many steps and time. In particular, when using a large substrate, the diameter of the quartz ampoule required is also large, making it difficult to mass-produce. Furthermore, the diffusion method is easily affected by the condition of the substrate surface and is also greatly affected by the purity of the diffusion source, making it difficult to obtain a uniform diffusion concentration and depth.

Let me briefly explain the reason.

The ZnP ₂ in the ampoule decomposes to some extent, and the Zn
As a source of diffusion into GaP, P acts as a pressure source that suppresses the decomposition of GaP. The diffusion source Zn is GaP
However, since the effective energy for diffusion is thermal energy, it is at most about 1 eV or less. Therefore, if impurities are attached to the GaP surface or an oxide film is formed, diffusion will be hindered and the diffusion depth will likely be uneven. Of course, if there are impurities in ZnP ₂ , there is a possibility that they will enter GaP.

The present invention has been made in order to eliminate the drawbacks of the above-mentioned methods, and includes providing a first protective film on a single crystal or polycrystalline plate of a - group compound semiconductor;
A protective film is processed into a predetermined shape, impurity atoms are irradiated onto the substrate by ion implantation, the first protective film is removed after the ion implantation, and a second protective film is applied to the substrate. The impurity atoms are introduced into the substrate by heat treatment at a temperature of 700° C. or higher using an open tube method. According to the method described below, Zn etc. can be introduced into GaP etc. by the open tube method without vacuum sealing the sample GaP etc. in a quartz ampoule and without using ZnP ₂ etc.
Ions have energy greater than KeV, so they are less susceptible to the effects of surfaces such as GaP, and in addition, Zn, etc., are selectively separated in the ion state using methods such as mass spectrometry, so they are less susceptible to purity. Very good.

In order to achieve the above object, the present invention provides the first
Polished and chemically etched as shown.
The substrate 1 is made of GaP etc. using the CVD method
SiO ₂ , PSG
A protective film 21 of about 100 to 10,000 Å is formed using an oxide film such as (phosphorous silicate glass), Al ₂ O ₃ , Si ₃ N ₄ or the like, a nitride film, or a photoresist. This protective film is then processed into a desired shape. When pattern processing is performed before ion implantation in this manner, processing is easy because the PSG film is not altered by ion implantation. Therefore, machining accuracy is good. Ions 51 of Zn or the like accelerated by an electric field or the like are irradiated from above. Zn etc. are introduced into part 4. The amount of ion irradiation such as Zn or the like varies depending on the desired depth of introduction of Zn or the like and its concentration. Also, the irradiation energy is
It is determined from two points: the amount of Zn, etc., and the depth to which the irradiated Zn, etc. will not evaporate and disperse from the surface to the outside during the heat treatment for diffusion. After irradiating Zn, etc., the first protective film affected by this irradiation is removed.
This reduces the possibility that leakage current or peeling of the second protective film to be formed next will occur in the semiconductor device manufactured.

A second protective film 6 made of PSG or the like is again formed on the semiconductor substrate thus prepared. Then, by heat treatment at a suitable high temperature of 700° C. or higher, Zn and the like are introduced into the portion 7 by diffusion, as shown in FIG. 1c. In this way, the surface of GaP etc. is covered with a protective film, and Zn etc. are not dispersed to the outside during heat treatment.
There is no need to seal it in a quartz ampoule, it is sufficient to flow an inert gas, etc., and there is less contamination by impurities.
Stable introduction of Zn etc. can be performed. Therefore, expensive quartz ampoules are unnecessary and steps such as vacuum sealing can be omitted, so it is highly useful industrially.

In the present invention, it is particularly important to perform heat treatment at a temperature of 700° C. or higher while covering the substrate with a protective film after ion irradiation. When the heat treatment temperature is lower than 700° C., it is almost impossible to diffuse impurity atoms such as Zn into the substrate favorably. When heat treatment is performed at a heat treatment temperature lower than 700° C., it is undeniable that an enormous amount of time is required to diffuse impurity atoms such as Zn into the substrate to a desired depth.

EXAMPLE FIG. 1 shows a method of manufacturing a green light emitting diode using GaP according to the method of the present invention.

FIG. 1 shows the main parts of the process of this example. First a
A substrate 1 with an n-type epitaxial growth layer of about 30 μm is coated with PSG (phosphorous) of about 5000 Å, as shown in
silicate glass) 2 by CVD method, and only the areas where Zn diffusion is required by photoresist method.
Get rid of PSG. Next, 5×10 ¹⁵ cm ⁻² of Zn ions 5 accelerated to 100 KV are irradiated. 3 and 4 are Zn
This is the part where ions are introduced. If the temperature of the sample is raised to about 500°C during this irradiation, Zn ions can be stably introduced with fewer lattice defects. then b
Remove PSG 3 as shown in the figure and cover the entire surface again with PSG.
Attach 6 to about 3000Å. After that, when heat treated in a nitrogen stream at 900℃ for 14 hours, Zn diffuses and
Convert to p-type up to a depth of about 9 μm as shown in the figure. after that,
A light-emitting diode can be obtained by attaching electrodes in the usual way, cutting it into single diodes, and assembling them. A product with excellent green luminescence efficiency was obtained. Of course, a quartz ampoule is not required, and the vacuum sealing process can also be omitted.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an apparatus at each step showing a method of manufacturing a GaP green light emitting diode of the present invention. 1: Semiconductor substrate, 2: First protective film, 3, 4:
Implanted ion, 5: implanted ion, 6: second
protective film, 7: p-type region.

Claims (1)

[Claims] A first protective film is provided on a single crystal or polycrystalline substrate of a 1-group compound semiconductor, the first protective film is processed into a predetermined shape, and impurity atoms are irradiated onto the substrate by an ion implantation method. After this ion implantation, the first protective film was removed, a second protective film was provided on the substrate, and then an open tube method was used to remove the first protective film.
A method for manufacturing a semiconductor device, comprising the step of introducing the impurity atoms into the substrate by heat treatment at a temperature of .degree. C. or higher.