JPH04192516A - Impurity diffusion into inalp compound semiconductor - Google Patents

Abstract

PURPOSE:To enable formation of a P type semiconductor layer in the vicinity of the extreme surface in the depth of about 1mum of a InAlLP semiconductor by using a substance obtained by adding phosphorus to a compound including zinc and phosphorus as a diffusion source, setting the phosphorus pressure in the system to 0.01 to 3 atmospheric pressure, heating the substance up to 670 to 750 deg.C and diffusing it and thereafter cooling it quickly. CONSTITUTION:As a InAlP group wafer 3, InAlP, InAlGaP, etc., are sued and as a diffusion source 2 obtained by adding phosphorus to a compound including zinc and phosphorus, a substance ading P such as Zn3P2, ZnP2 is used. A quartz ampul 1 is heated at 670 to 750 deg.C. The phosphorus pressure in the system can be adjusted by kind and quantity of diffusion source 2 and a heating temperature and the desirable pressure is set to 0.01 to 3 atmospheric pressure. After the diffusion processing, a quartz ampul 1 is quickly cooled by ice water. Thereby, a P type semiconductor layer can be formed in the vicinity of the extreme surface in the depth of about 1mum of the InAlP semiconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to InAl! A method of impurity diffusion into P-based compound semiconductors, especially a method of impurity diffusion to form a P-type semiconductor layer (hereinafter referred to as P layer) near the extreme surface of an InAIP semiconductor with a depth of about 1 μm and to easily control the depth of the P layer. It is related to.

(Prior Art) InAIP-based materials and gold conductor materials have recently attracted attention, including materials for visible light semiconductor lasers that oscillate at short wavelengths, and are expected to develop in the future. This In, Lj
In creating a device using a 7P compound semiconductor,
Formation of the P layer by Zn diffusion is a fundamental and important process. Conventionally, methods for forming a P layer and diffusion of zinc with good controllability for compound semiconductors with a relatively small bandgap such as GaAs, and InP systems that do not contain Aβ are known (for example, Japanese Patent Publication No. 2-24369). Public bulletin)
. In other words, a zinc compound as a diffusion source and the compound semiconductor wafer are sealed in a quartz ampoule under vacuum, and then heated in an electric furnace or the like for a predetermined temperature and time, and the zinc vapor generated in the ampoule causes the wafer to be heated. This causes the zinc to diffuse into the interior of the body.

(Problems to be Solved by the Invention) A semiconductor laser is an example of a semiconductor device using InA7P. In this case, InAl! due to diffusion of impurities such as zinc! A zinc diffusion layer (P layer) must be formed near the extreme surface with a depth of about 1 μm from the P surface. For this purpose, a zinc diffusion method that can form a P layer and has good controllability of the depth is required.

Conventionally, zinc diffusion for GaAS, InP, etc.
The P layer can be formed under conditions where the diffusion temperature is relatively low, such as 50° C. or less. Furthermore, since the diffusion rate is slow and the steepness of the zinc diffusion profile in the depth direction is good, the P layer can be formed near the extreme surface (approximately 1 μm) with good controllability.

When this method is applied directly to [nl'P, zinc is
Despite diffusing very quickly into n1P, no P layer can be formed. In other words, this means that the bonds between Af and P atoms that make up the substrate material are strong, and either they are broken and enter a site in the solid to be developed as a zinc or P-type semiconductor, or (nP, GaAs This is because it is significantly more difficult than

The present invention utilizes 1nAI!, which has not been used in semiconductor devices in the past! For P-based semiconductor materials, near the surface (approximately 1μ
m) to form a P layer and to provide a zinc diffusion method that allows good controllability of the depth from the surface.

(Means for solving problems) That is, the gist of the present invention is as follows.

In a method of diffusing impurities by heating InAIP-based compound semiconductor materials to high temperatures, a compound containing zinc and phosphorous plus phosphorus is used as a diffusion source, and the phosphorus pressure in the system is set to 0.01 to 3 atm. , heat at 670-750″C,
This is an impurity diffusion method into an In1P-based compound semiconductor characterized by rapid cooling after the diffusion treatment.

The present invention will be explained in more detail below.

FIG. 1 shows a state in which a diffusion source 2 and an InAlP wafer 3 are sealed in a quartz tube ampoule 1 under vacuum for diffusion processing. InA17P wafer is InAl
P, InAl! GaP etc. are used. When phosphorus is added to a compound containing zinc and phosphorus that is a diffusion source, Z
n+P2, ZnP*, etc. plus P is used. This quartz tube ampoule was heated to 670 to 7
Heat at 50°C.

P if diffusion treatment is performed at a temperature lower than 670°C.
The formation of a ' type semiconductor layer is not observed, and if the diffusion treatment is performed at a temperature higher than 750°C, problems such as diffusion of impurities originally contained in the InAj7P wafer and deterioration of the wafer itself may occur, so it is not practical. It is difficult to form a typical P layer.

The phosphorus pressure in the system can be adjusted by the type and amount of the diffusion source and the heating temperature, and is preferably 0.01 to 3 atm. FIG. 2 is a diagram showing carrier concentration and zinc diffusion depth when rnAlpnAl- is subjected to diffusion treatment under various diffusion conditions. If the phosphorus pressure is lower than 0.01 atm, phosphorus evaporates from the wafer rapidly, Zn diffuses quickly, and it is difficult to control the diffusion depth from the surface.

That is, the curve in Figure 2A is 670'C or 0 phosphorus pressure.
．． This may be due to the relationship between carrier concentration and zinc diffusion depth when diffusion treatment is performed at 0.001 atm for 20 minutes.The diffusion rate of zinc is extremely slow, and the change in carrier concentration in the depth direction is small. Since the profile is not steep, controllability is low. On the other hand, for example, 670°C17
For those subjected to diffusion treatment for 20 minutes at a pressure of 3 atm at 50'C, the carrier concentration was significantly reduced at a diffusion depth of 1 μm.
It is easy to control the depth of the P layer.

However, if the phosphorus pressure is increased above 0.3 atm,
After diffusion, surface roughness appears on the wafer, which is thought to be due to phosphorus condensation. Roughness of the wafer surface is a fatal problem in the production of semiconductor devices.

The vapor pressure of phosphorus is quite high, so when it is rapidly cooled after diffusion, it does not completely condense on the inner wall of the quartz tube, but instead condenses on the wafer.To prevent surface roughening, the pressure of phosphorus must be set to zero.
．． It is necessary to set the pressure to 1 to 3 atmospheres.

In this case, if the quartz ampoule is slowly cooled, phosphorus will condense on the wafer, so it is necessary to cool it quickly. That is, after the diffusion treatment under the conditions described above, it is necessary to quickly cool the quartz ampoule with ice water, preferably within 10 seconds.

Since the conditions for quenching vary depending on the size of the ampoule, that is, the content thereof, it is preferable to cool it as quickly as possible, or if it cannot be determined exactly.

(Examples and Comparative Examples) The present invention will be specifically explained below by giving Examples and Comparative Examples.

[Examples 1 to 7] As shown in Fig. 1, a quartz ampoule (10Mφ x 60mm
) 1 as a diffusion source 2, Zn3P2+p as a diffusion source 2, wafer 3
as Ino, sAz O,sP or Ino, s
AI! 0.25G0.2SP (9X 9Xo, 4m
m) and vacuum-sealed in a vacuum of 2 x 10-'torr, then placed in an electric furnace and subjected to diffusion treatment under the conditions shown in Table 1. The pressure of phosphorus was adjusted by the amount of phosphorus charged as a diffusion source. For rapid cooling, after the diffusion treatment, the quartz ampoule containing the diffusion source was cooled with ice water. As a result, the results shown in Table 1 were obtained.

The wafer thus obtained has a good surface condition;
The formation of the P layer was also satisfactory and had a thickness of 1 μm or less. The steepness of the P layer was also good and excellent, and when used as a semiconductor laser device, it exhibited good characteristics.

Note that the diffusion profile of Example 3 corresponds to B in FIG. Similarly, Example 4 corresponds to C and Example 5 corresponds to D.

[Comparative Examples 1 to 7] Zn3 was added as a diffusion source in a quartz ampoule as in the example.
After putting P2+p, Ino, 5Ajl'o, and sP wafers and vacuum sealing, put it in an electric furnace and put it in the second
Diffusion treatment was performed under the conditions shown in the table. The rapid cooling was performed in the same manner as in Examples, or the slow cooling was performed by taking it out of the electric furnace and leaving it to cool in the air. As a result, the results shown in Table 2 were obtained. These factors include wafer surface condition, P layer formation,
It could not be used as a semiconductor laser device because either the thickness of the P layer or the steepness of the P layer was defective.

Incidentally, the diffusion profile of Comparative Example 3 corresponds to A in FIG.

(Effect of the invention) According to the invention, Inl? When forming a P-type semiconductor layer of a P-based semiconductor, the depth of the P layer can be easily controlled, the P-type semiconductor layer can be formed close to the extreme surface of about 1 μm, and the surface condition is good. You can get something out of it. By using a P-type semiconductor obtained by this diffusion method, a good semiconductor laser device can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a quartz ampoule containing a diffusion source and a wafer for the diffusion process. 1... Quartz ampoule 2... Diffusion source 3... Wafer FIG. 2 shows the relationship between carrier concentration and zinc diffusion depth when [nAAP wafer is subjected to diffusion treatment]. A-D are diffusion treatment conditions (temperature, phosphorus pressure, time) A:6
70°C, 0,001 atm, 20 minutes B: 670",
0.3〃, 20"C: 670",
3, 20〃D Near 50”, 3〃
, 20 Patent applicant Denki Kagaku Kogyo Co., Ltd. Figure 1 Figure 2 Zinc diffusion depth (7.1 m)

Claims (1)

[Claims] In a method of diffusing impurities by heating InAlP-based compound semiconductor materials to high temperatures, a compound containing zinc and phosphorus plus phosphorus is used as a diffusion source, and the phosphorus pressure in the system is set to 0.01 to 3 atm. and heated at 670-750℃,
A method for diffusing impurities into an InAlP-based compound semiconductor, which is characterized by rapid cooling after diffusion treatment.