JPH03252399A - Production of semi-insulating gaas substrate - Google Patents

Abstract

PURPOSE:To obtain a semi-insulating GaAs substrate having low dislocation density and >=10<7> specific resistance without adding chromium in growing GaAs crystal by vertical temperature gradient method by adding a specific amount of impurity such as carbon to be an acceptor to raw material crystal or the impurity and a raw material to a growing crucible. CONSTITUTION:In growing GaAs crystal by vertical temperature gradient method, an impurity of at least one of carbon, copper, zinc, beryllium, magnesium, cadmium, lithium, gold, silver, lead, cobalt and nickel to become an acceptor in an amount to give 1X10<15> atoms cm<-3> to 3X10<15> atoms cm<-3> atomic concentration in grown crystal after subtracting concentration of impurities such as silicon or sulfur is added to raw material crystal or the impurity and a raw material are added to a growing crucible, crystal is produced and then cut into a wafer shape.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to LSI and IC substrates with a resistivity of 10 Ωcm.
The present invention relates to a method of manufacturing the above semi-insulating GaAs substrate.

[Conventional technology]

Since GAAs has a higher electron mobility than Sl, it is used as a substrate for microwave communication devices, and is also being used as a substrate for next-generation ultrahigh-speed integrated circuit devices with increasing peripheral speed. This GaAs substrate is usually manufactured from an ingot obtained by the liquid seal pulling method (hereinafter abbreviated as LEC method) or the horizontal Bridgman method (hereinafter abbreviated as HB method) in which chromium is added. However, in devices manufactured by growing an epitaxial film on a GaAs substrate, the GaAs substrate obtained by the HB method has a low dislocation density, but the chromium added to the substrate has an adverse effect on the epitaxial film, so it is difficult to add chromium. It is desired to provide a semi-insulating GaAs substrate without additives. In addition, GaA obtained by the LEC method
Although the s-substrate does not contain any impurities and is semi-insulating, it is not used because of its high dislocation density.

In order to solve these problems, the vertical temperature gradient method (VG
Although the GaAs substrate obtained by the GF method has the same dislocation density as the GaAs substrate obtained by the HE method, the resistivity remains in the 1o"hw) range. There is.

For LSI and IC substrates, it is important to have good electrical isolation between elements and a high specific resistance to enable high integration, and generally 107Ω (m or more is required. However, the vGF method The resistivity of the additive-free GaAs substrate obtained in the above method is too low as described above, and therefore electrical isolation between elements is incomplete, causing a problem of leakage current through the substrate.

[Problem to be solved by the invention]

An object of the present invention is to provide a method for obtaining a semi-insulating GaAs substrate having a low dislocation density and a resistivity of 107ΩCI+1 or more without addition of chromium.

[Means to solve the problem]

In order to achieve the above-mentioned problems, the present invention utilizes Ga by the VGF method.
When growing Al1 crystals, carbon, copper, zinc, beryllium, magnesium, cadmium, lithium, gold, silver, lead, cobalt,
Impurities that serve as acceptors for at least one of nickel, after subtracting the concentration of impurities that serve as donors such as silicon and sulfur, are present in the grown crystal at 1X1 x 1015 am-' ~ 3 x 10''6 cm. The feature is that the crystal is manufactured by adding it to an atomic concentration of -'', and then it is cut into wafer shapes.

[Effect]

In GaAs crystals obtained by the LECt method, there are rare cases where the atomic concentration of residual carbon, which is an acceptor, is lower than 1Xl x 1015 C1n, but in that case, the temperature is 500 to 650 C'' as shown in the figure. When heat-treated in a range of
The inventors have confirmed that when the specific resistance decreases to Ωcm or less, and then heat-treats it at 700 C' or higher and rapidly cools it to 450 C', the deep donor level disappears and the resistivity recovers to 10' Qm or higher. . However, in general, crystals obtained by the LWC method have a carbon atom concentration of 1
The resistivity is higher than 0 pieces cm, and it is extremely rare for the specific resistance to drop below 020 m.

On the other hand, GaAs crystals obtained by the vGF method do not contain any carbon components in the crystal growth system, so there is no contamination, and the carbon atom concentration is always below lXl0' cm-. As described above, a deep donor level is generated, and the resistivity decreases to the order of 10'Ωcm. This resistivity is 107
When growing a GaAs crystal using the vGF method, in order to achieve a GaAs crystal of Ωcm or more, impurities such as silicon, sulfur, etc., which act as acceptors such as carbon, are added to the raw material crystal or to the growth crucible together with the raw material. After subtracting the concentration of donor impurities, 1 x 101 cTn ~3
Crystals are produced by adding X 10' pieces/cm. Acceptor, donor, KL2 (0 below conduction band
．． The above concentration balance between the donor level (located at 78 eV) indicates that the acceptor remaining after electrically compensating the donor is electrically compensated to EL2, and this In this case, the GaAs crystal becomes semi-insulating with a specific resistance of 10"9 cm or more.

By manufacturing a GaAs crystal by adding impurities with such a balanced concentration, a semi-insulating substrate can be stably obtained without adding chromium.

〔Example〕

Comparative Example (Manufacture of additive-free GaAs) In a pyrolytic boron nitride crucible with an inner diameter of 52 mm, 700 g of GaAs raw material was placed on top of a GaAs single crystal as a seed crystal, and a gold J! A quartz-sealed tube containing 15 g of iAs in a reservoir and sealed by reducing the internal pressure to 10 torr was set in a VGF furnace. A8
After heating the reservoir to 615C' and melting the upper end of the seed crystal and the raw material crystal part above it to 1238-1350C',
The temperature decreased at 0.6°C per hour. After the crystal growth was completed, the entire crucible was subsequently cooled to room temperature at a cooling rate of 1.0 to 1.5 C' per minute, thereby growing a single crystal using the VC)F method. A GaAs crystal having a carbon atom concentration of less than 1×10 CTn obtained by the VGF method was cut into a wafer shape with a thickness of 0.6 mrr, which was further shaped into a chip with a four-angle shape, and the specific resistance was measured. Specific resistance measurement is
This was done using the Hall coefficient measurement method. The results are shown in Table 1.

Example 1 (Manufacture of zinc-doped GaAs) Carbon atom concentration lXl×1015 (less than m G
When growing an aAs crystal, zinc is added to the raw material crystal, after subtracting the concentration of donor impurity atoms such as silicon, so that the number of zinc atoms in the grown crystal is 3 x 10 cm or less. was manufactured and then cut into wafers and the specific resistance was measured. Specific resistance was measured using the Hall coefficient measurement method. The results are shown in Table 1.

As is clear from Table 1, the additive-free wafer is 5X1
At a carbon atom concentration of 0'CwI, the specific resistance is 5×10Ωc
The wafer produced according to the present invention has a zinc atomic concentration of 2 × 10 cm and 3 ×
It shows semi-insulating property of 10'Ωcm.

Table 1 Example 2 (Manufacture of copper-doped GaAs) Copper was added by the VGF method similar to Example 1 to a concentration of 3×10 in the grown crystal after subtracting the concentration of impurity atoms serving as donors such as silicon. A crystal was manufactured by adding 1000 mol (m) or less, and then it was cut into wafers and the specific resistance was measured.The specific resistance was measured using the Hall coefficient measurement method.

Similar to that obtained in Example 1, the copper-doped wafer obtained a copper atomic concentration of 2 x 1 x 1015 cm2 and exhibited semi-insulating property of 3 x 10''ΩcTI+.

〔Effect of the invention〕

As described above, according to the present invention, a semi-insulating ()aAs substrate with a low dislocation density can be obtained without adding chromium, and a G
It can greatly contribute to the development of aAs technology (!, LS).It goes without saying that the present invention can also be applied to the vertical Bridgman method, which has the same principle as the VGF method.

[Brief explanation of drawings]

The figure is a graph showing the temperature dependence of resistivity change due to generation and extinction of deep donor levels, which is the basis of the present invention. Heat treatment temperature (0C) Procedural amendment (voluntary) 1゜Indication of the case Heisei Patent Application No. 8881 2. Name of the invention Method for manufacturing semi-insulating G&All substrates 3゜Relationship with the person making the amendment

Claims (1)

[Claims] (1) When growing GaAs crystals by the vertical temperature gradient method, carbon, copper, zinc, beryllium, magnesium, cadmium, lithium, gold, silver, lead, cobalt, and nickel are placed in the raw material crystal or in the growth crucible together with the raw materials. After subtracting the concentration of at least one acceptor impurity such as silicon and sulfur, there are still 1 x 10^1^5 cm^-^3~3x in the crystal after growth.
A method for manufacturing a semi-insulating GaAs substrate, characterized by manufacturing a crystal by adding 10^1^6 atoms to an atomic concentration of 10^1^6 cm^-^3, and then cutting it into wafer shapes.