JPS627695A - Production of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To produce the titled dislocation-free high-purity group III-V compd. semiconductor single crystal by detecting the amt. of the splashed group V volatile element in the melt and growing the single crystal while injecting the element equivalent to the detected amt. and correcting the composition. CONSTITUTION:In an airtight vessel 1 using a gaseous Ar at 5kg/cm<2> pressure as the atmospheric gas, the melt 2 of GaAs in a crucible 3 is kept at a prescribed temp. with a heater 5 and an insulating material 6 and a pulling rod 9 is lowered and then pulled up to grow a GaAs single crystal on the leading end of the rod. In the device, the weight of the melt 2 in the crucible 3 is detected by a lower weight sensor 8 and a sensor rod 7 for supporting a supporting cylinder 4 for the crucible 3, the weight of the formed single crystal is also detected by the pulling rod 9 and an upper weight sensor 10, and the amt. of As splashed is calculated by a computer 13 from the detected values. Then a heater 12 is controlled and As equivalent to the amt. of the splashed As is injected and replenished into the melt 2 from an As injector 11 to satisfy the stoichiometrical composition and the crystal is grown.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing an m-v group compound semiconductor single crystal in which volatile elements are in the V group by the Czochralski method.
In particular, the present invention relates to a method for manufacturing dislocation-free crystals without using a liquid sealant.

[Conventional technology]

In recent years, high-quality crystals of m-v group compound semiconductors have become available, and they have come to be widely used in integrated circuits, opto-electronic integrated circuits, electronic materials, and the like. Among m-v group compound semiconductors, gallium arsenide (GaAs) has characteristics such as high electron mobility, easy luminescence, and light detection, and is used in microwave transistors, high-speed integrated circuits, solar cells, and light-emitting devices. It is being used as an electronic material.

In order for a GaAs single crystal to be used as a substrate for the above-mentioned integrated circuit, it must have semi-insulating properties with a resistivity of 107 Ωcm or more, be free of physical and chemical defects such as dislocations and lattice defects, and have little residual impurities. Furthermore, it is required to have good heat treatment characteristics. Among these, dislocations and lattice defects particularly affect the characteristics of integrated circuits and cause a decrease in yield.

By the way, 2m-v group compound semiconductor single crystals have conventionally been manufactured by the liquid-encapsulated Czochralski method (LEC method). That is, by pulling up the GaAs melt and growing it, GaAs
While growing a single crystal, this melt is covered with boron oxide (BzOl), which is a liquid sealant, to suppress evaporation of group V elements.

[Problem that the invention seeks to solve]

In the method for manufacturing the m-v group compound semiconductor single crystal described above,
Since boron oxide, which has a large heat transfer coefficient, is used as the liquid sealant, the temperature gradient at the GaAs solid-liquid interface increases, which is necessary to obtain a high-quality crystal without dislocations.
It is difficult to realize a low temperature gradient at the solid-liquid interface of s.

Also, the scattering of arsenic through boron oxide cannot be ignored.
This causes a difference in composition between group (I) and group (II) elements, which causes dislocations and inherent defects. Further, boron oxide is incorporated into the GaAs single crystal during crystal growth, and GaAs produced by the LEC method contains 101b to 10 "C11-" poron, which inhibits high purity of the crystal.

The arsenic control Czochralski method has been proposed as a method to solve these problems, but this method involves growing crystals in a quartz container in order to control the arsenic installed in the furnace. As a result, silicon elements are mixed into the crystal, making it impossible to obtain a semi-insulating substrate.

[Means for solving problems]

The method for manufacturing a compound semiconductor single crystal of the present invention includes:
In this method, the amount of scattered group elements is detected by a weight sensor, and an amount corresponding to this amount of scattered elements is injected into the melt for correction, thereby growing a single crystal while satisfying the stoichiometric composition.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an apparatus for producing GaAs single crystals by the method of the present invention. In the figure, inside the airtight container l, G
A crucible 3 containing aAs melt 2 (for example, a 4-inch diameter P
A BN crucible) is supported by a support tube 4, which is surrounded by a carbon heater 5 and a carbon heat insulating material 6 to maintain a predetermined temperature. A sensor rod 7 extending downward is connected to the support cylinder 4, and a lower weight sensor 8 is attached to the lower end of the sensor rod 7 to detect the weight of the crucible 3 and the GaAs melt 2. Further, a lifting rod 9 is vertically extended above the crucible 3, and a lower weight sensor 10 is installed at the upper end of the pulling rod 9.
The weight of the GaAS crystal that is attached and pulled is detected.

Furthermore, an arsenic injection device 11 is installed inside the airtight container 1, and arsenic can be additionally injected into the GaAs melt 2. This arsenic injection device 11 is connected with an arsenic injection heater device 12, and by controlling the heating temperature of the arsenic injection device 11, the amount of arsenic to be injected can be controlled. The arsenic heater device 12 can be controlled by a computer 13, which includes the upper and lower weight sensors 8. An IO detection signal is input. In the figure, 14 is an observation window, and although not shown, an atmospheric gas such as argon can be supplied into the airtight container 1.

Using this device, 2 kg of equal chemical equivalents of Ga and As were charged into the crucible 3, argon was used as the atmosphere gas, the pressure during direct synthesis was 80 kg/cal, and the pressure during crystal growth was 5 kg/ctA. It is. Under these conditions, the GaAs melt in crucible 3 was pulled up and
The crystal is grown by pulling it up with a single pin 9. and 0
At the same time, the weights are detected by the lower weight sensor 8 and the lower weight sensor 10, respectively, and these values are calculated by the computer 13 to calculate the amount of arsenic scattered from the GaAs melt 2. The computer 13 controls the arsenic injector heater 12 based on the calculated value, corrects it by additionally injecting arsenic into the GaAs melt 2 in an amount corresponding to the arsenic scattered via the arsenic injection device 11, and Satisfy the stoichiometric composition. As a result, a GaAs single crystal A having a diameter of 540 mm and a length of 100 B was manufactured.

In order to compare with this single crystal A, we used the same device and charged 300 g of boron oxide in addition to 2 kg of Ga and As, and used normal LEC without making any correction for the scattered arsenic.
GaAs single crystal B under argon pressure of 5 kg/cm by method
In other words, the same crystal as the conventional one was produced.

Here, boron oxide has a large heat transfer coefficient as shown in Figure 2, but the inert gas such as argon has a property that the larger the molecular weight, the smaller the heat transfer coefficient. Even helium gas, which has a small molecular weight, has a heat transfer coefficient at the growth temperature that is more than an order of magnitude smaller than that of boron oxide. Therefore, in this example using readily available nitrogen gas or argon gas, the temperature gradient at the GaAs solid-liquid interface can be significantly reduced compared to the LEC method.

Furthermore, by automatically repeating additional implantation of arsenic scattered by the arsenic implantation device 11 during crystal growth,
Growth can proceed while the stoichiometric composition of Ga and As is kept constant.

A wafer was cut from the single crystals A and B produced as described above at a distance of 20 tm from the top of the straight body as shown in FIG. 3, and the dislocation density of each crystal was examined using a KOH melt.

As a result, as shown in FIG. 4, single crystal A (of the present invention)
If the peripheral 2fl are excluded, the dislocation density is less than 500 per 1, but in single crystal B (conventional), it is as high as 104. In addition, residual impurities (
When analyzing boron), crystal A was found as shown in Figure 5.
In crystal B, it is less than 10"c-', but in crystal B it is less than 10"c
m-' or more were observed. Furthermore, when the stoichiometry was measured by the X-ray quasi-forbidden reflection method, as shown in FIG. 6, the stoichiometry was constant within the plane for crystal A, but was non-uniform for crystal B.

In addition, we actually fabricated FETs using crystal A and B wafers, and demonstrated that the threshold voltage (vth), which is one of the device characteristics, was
), the standard deviation of the variation was as small as 3 mV for crystal A, and 50 mV for crystal B.
It turned out to be a big deal.

From these results, it can be seen that the production method according to the present invention produces a highly pure dislocation-free crystal with a controlled composition.

Furthermore, when the method of the present invention is adopted, since the grown single crystal is exposed to high temperatures, there is a concern that dislocations may occur due to the dissociation of arsenic from the periphery of the crystal. It exists only at the periphery, and the outer periphery 2 of the crystal.
There is no practical problem if n is cylindrically ground.

Furthermore, although the method of the present invention is effective for undoped crystals and chromium-doped crystals, it is also effective when neutral impurities are added to harden the crystals.

Furthermore, the present invention can be applied to GaP and InP, which are m-v group compound semiconductors other than GaAs, for the same reason.

[Effects of the Invention] As explained above, the method for manufacturing a compound semiconductor single crystal of the present invention detects the amount of scattered group V elements with a weight sensor when growing a compound semiconductor single crystal by the Czochralski method,
Since the amount equivalent to this amount of scattering is injected into the melt and corrected, the single crystal is grown while satisfying the stoichiometric composition.
A highly pure dislocation-free crystal with controlled composition can be obtained,
Even when a semiconductor device is constructed, an element with very little variation in characteristics can be constructed, and an excellent m-v group compound semiconductor single crystal or a semiconductor device thereof can be constructed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram of an apparatus for carrying out the method of the present invention, FIG. 2 is a graph showing the heat transfer coefficient of each gas, FIG. 3 is a diagram explaining the position of cutting out the manufactured single crystal wafer, Figure 4 shows the distribution of dislocation density within the wafer surface, and Figure 5 shows the distribution of dislocation density within the wafer surface.
Figure 6 shows the analysis results of residual boron by secondary ion mass spectrometry.
FIG. 3 is a diagram showing an in-plane distribution of deviations from the wafer. DESCRIPTION OF SYMBOLS 1... Airtight container, 2... GaAs melt, 3... Crucible, 5... Carbon heater, 6... Carbon insulation material, 8... Lower weight sensor, 9... Pulling rond ,
10... Lower weight sensor, 11... Arsenic injection device, 1
2... Arsenic heater, 13... Computer,
14...Observation window. Figure 1 Figure 2 Figure 2 Arashi (K)

Claims (1)

[Claims] 1. When growing a III-V group compound semiconductor single crystal having a volatile element in group V by the Czochralski method, the amount of the group V volatile element scattered in the melt is calculated by weight. 1. A method for manufacturing a compound semiconductor single crystal, which comprises detecting the amount of scattering with a sensor, injecting and correcting an amount corresponding to the amount of scattering into the melt, and growing the single crystal while satisfying the stoichiometric composition. 2. A method for manufacturing a compound semiconductor single crystal according to claim 1, which comprises corrective injection of As into the melt when growing a GaAs single crystal using a melt of Ga and As.