JP2737990B2 - Compound semiconductor single crystal manufacturing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for growing a compound semiconductor single crystal by a liquid-sealed Czochralski method, and more particularly, to uniforming the distribution of impurities having a segregation coefficient larger than 1.0 in a crystal. The present invention relates to an apparatus for performing correction.

[Related Art] In recent years, compound semiconductors have been improved in crystal quality mainly of III-V group compounds, and have been widely used for integrated circuits, opto-electronic integrated circuits, materials for electronic devices, and the like. III
Among group V compound semiconductors, gallium arsenide (GaAs) has features such as high electron mobility, easy light emission, and light detection. Microwave transistors, high-speed integrated circuits,
It is being widely used as a material for solar cells.

GaAs crystals are generally grown by a liquid-sealed Czochralski method (LEC method) using a high-pressure crystal growth furnace.・ Semi-insulating property of more than cm, no physical or chemical defects such as dislocations and lattice defects, good heat treatment characteristics, etc., and impurities in the crystal are uniform at the top and tail of the crystal And that the wafer characteristics do not change within the crystal ingot.

[Problems to be solved by the invention]

However, in the semi-insulating GaAs single crystal grown by the LEC method in the conventional high-pressure crystal growth furnace described above, since the carbon element in the crystal has an effective segregation coefficient greater than 1.0, its concentration increases from the top of the crystal to the tail. It has the disadvantage of decreasing.

The above drawbacks are significant because the carbon in the semi-insulating GaAs crystal acts as an acceptor, altering the apparent activation rate of the silicon element implanted to form the active layer, thereby reducing the yield of GaAs devices. Problem.

An object of the present invention is to provide a compound semiconductor single crystal manufacturing apparatus which solves the above-mentioned problems.

[Differences of the Invention from the Prior Art]

Compared with the above-mentioned conventional high-pressure single crystal pulling furnace for compound semiconductors, the apparatus according to the present invention is characterized in that the concentration of impurities whose effective segregation coefficient is larger than 1.0 decreases as crystal growth progresses in the crystal, There is a difference that the impurity element can be corrected by injecting the impurity element in the form of an oxide gas or the like and the distribution in the crystal can be made uniform.

[Means for solving the problem]

In order to achieve the above object, a compound semiconductor single crystal manufacturing apparatus according to the present invention is a compound semiconductor single crystal manufacturing apparatus for growing a compound semiconductor single crystal by a liquid-sealed Czochralski method. It has a means for supplying gas and a means for controlling the pressure of the carbon dioxide gas so as to make the carbon concentration from the top to the tail of the single crystal uniform.

〔Example〕

Next, the present invention will be described with reference to the drawings, taking a GaAs semiconductor as an example.

Embodiment 1 FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.

In the figure, 1 is a gas injection nozzle, 3 is a high-pressure gas cylinder for supplying gas to the nozzle 1, 2 is a high-precision pressure controller, 4 is a crucible, 5 is a furnace body, 6 is a compound semiconductor melt, and 7 is a heater. , 8 denotes a compound semiconductor single crystal, 9 denotes a pressure tool part, 10 denotes a heat retaining member, and 11 denotes a liquid sealant layer.

 Crystal growth was performed as follows.

A 6-inch diameter PBN crucible 4 is charged with a total of 4000 g of Ga metal and As metal and boron oxide (B ₂ O ₃ ) as a sealant, and the inside of the furnace body 5 is replaced with argon (Ar) gas. The temperature was raised to produce a GaAs melt. On the other hand, a carbon monoxide gas cylinder was used as the injection high-pressure gas cylinder 3 for the purpose of correcting the non-uniformity of the carbon concentration in the crystal, and the nozzle 1 was inserted into the GaAs melt immediately before seeding the crystal. The nozzle 1 was made of PBN (pyrolytic boron nitride) in order to avoid impurity contamination of the melt, and was designed to be located very close to the inner wall of the crucible 4 so as not to adversely affect the convection of the melt in the crucible 4.

Since the effective segregation coefficient of carbon in the GaAs crystal is greater than 1.0, the carbon concentration decreases with the progress of crystal growth. In this experiment, the CO gas pressure in the tube of the nozzle 1 was controlled to introduce CO gas into the melt. By introducing the GaAs crystal, a 3-inch diameter GaAs crystal was produced while correcting the decreasing amount of carbon.

The obtained crystal was cut, and seven carbon concentration measurement samples were prepared at equal intervals between the top and the tail of the crystal. As a result of measurement by the Fourier transform infrared absorption method, 2.0 ± 0.5 × 10 ¹⁵ cm ⁻³
Within the range.

Also, seven wafers for device fabrication were cut out from the grown crystal at equal intervals to form a GaAs FET group, and the distribution of the FET threshold voltage between each wafer was examined.As a result, the characteristics of each wafer were uniform. Conventional 100-2 at the shoulder and tail of the crystal
The difference between the threshold voltages, which was 00 mV, was improved to 10 to 20 mV.

Second Embodiment Next, a second embodiment will be described.

In this embodiment, the raw material of GaAs is not a direct synthesis method but a polycrystalline GaAs crystal. Crystal preparation procedure and carbon concentration,
The FET threshold voltage evaluation method is the same as in the first embodiment.

Also in this embodiment, the variation in the carbon concentration in the crystal is
As good as 2.5 ± 0.5 × 10 ¹⁶ cm ^-3 , variation in threshold voltage
An improvement effect of 10 to 20 mV was observed.

〔The invention's effect〕

As described above, by using the compound semiconductor single crystal manufacturing apparatus according to the present invention, it is possible to obtain a GaAs single crystal having no carbon concentration variation, and to manufacture a GaAs integrated circuit or a large-scale integrated circuit using this crystal. This has the effect of significantly improving the yield.

Further, it is apparent that the device of the present invention can be applied to other compound semiconductors such as InP and GaP due to its structure, and has an effect of uniformly distributing residual impurities having an effective segregation coefficient larger than 1.0 in those crystals. is there.

[Brief description of the drawings]

 FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Gas injection nozzle 2 ... High precision pressure controller 3 ... High pressure gas cylinder for injection, 4 ... Crucible 5 ... Furnace body, 6 ... Compound semiconductor melt 7 ... Heater, 8 ... Compound semiconductor unit Crystal 9 ... Pressure tool part, 10 ... Insulation member

Claims (1)

(57) [Claims] 1. A compound semiconductor single crystal manufacturing apparatus for growing a compound semiconductor single crystal by a liquid-sealed Czochralski method, comprising: means for supplying carbon dioxide to a compound semiconductor melt in a crucible; Means for controlling the pressure of the carbon dioxide gas so as to equalize the carbon concentration in the compound semiconductor.