JPH0639356B2 - Boat member for liquid phase epitaxial growth equipment - Google Patents

Description

The present invention relates to a boat member used for liquid phase epitaxial growth of a compound semiconductor such as indium-gallium-arsenic-phosphorus.

(Prior Art and its Problems) The liquid phase epitaxial growth apparatus has a structure shown in FIG. That is, a boat (1) having a liquid reservoir for containing a solution for epitaxial growth, a slider (2) for mounting a single crystal plate and moving the boat, a quartz reaction tube (6) containing these members, It comprises a hydrogen gas supply pipe (8) attached to the quartz reaction tube, an electric furnace (11) for heating the quartz reaction tube, and the like.

The method of using this device is to put a metal lump, which is the raw material of various mother liquors for epitaxial growth, in the liquid reservoir of the boat, place a single crystal plate of indium phosphorus, gallium arsenic, etc. in the recess of the slider and carry out the quartz reaction. It is installed in a tube, the quartz reaction tube is heated to a predetermined temperature while passing hydrogen gas, the raw metal ingot is melted into a mother liquor, and then the slider is moved to sequentially change the composition on the single crystal plate. It allows for different epitaxial growth.

The boat member of the liquid phase epitaxial growth apparatus, that is,
Highly pure and dense graphite is used as the material for the boat body, slider, boat lid, and the like. Graphite is suitable as such a boat member because it has high thermal shock resistance, high thermal conductivity, and is difficult to react with various metals. However, graphite has the disadvantages that open pores are present on the surface and that graphite powder is easily separated from the surface. If there are open pores, impurities such as water and carbon dioxide will be adsorbed or arsenic and phosphorus will be deposited on those areas, and these impurities will come into contact with the epitaxial film during epitaxial growth, thus deteriorating the characteristics of the epitaxial film. It tends to be.

Attempts have been made to densify the graphite used in order to eliminate open pores, but the limit is to reduce the open porosity to about 5%, and it is not possible to completely eliminate open pores. Here, the open porosity is the ratio of the total volume of open pores on the surface of graphite to the volume of the graphite member. Attempts have also been made to make boat members by processing glassy carbon, but since glassy carbon is extremely hard and difficult to process, a boat member for liquid phase epitaxial growth, which requires precision by such a method, is used. It was impossible to create.

Further, when the graphite powder comes off, graphite is mixed into the epitaxial film, which adversely affects the characteristics, but there is no preventive measure.

An object of the present invention is to easily provide a boat member for a liquid phase epitaxial growth apparatus which has no open pores on the surface and has no separation of graphite powder from the surface.

(Means for Solving Problems) As a result of various studies on the surface coating of the boat member made of graphite in order to achieve the above-mentioned object, the inventors have only required to coat the surface of the graphite member with glassy carbon. Moreover, they have found that the thermal decomposition product of an organic polymer dissolved in an aliphatic chlorine-based solvent may be used as the coating raw material, and have completed the present invention.

That is, the present invention is a graphite member coated with glassy carbon, wherein the glassy carbon is formed from a thermal decomposition product of an organic polymer dissolved in an aliphatic chlorine solvent. A boat member for a liquid phase epitaxial growth apparatus, which is characterized in that

Hereinafter, the present invention will be described in detail.

The organic polymer used in this invention is a vinyl chloride resin,
Examples thereof include polyvinyl alcohol, oil-soluble phenol resin, alkylphenol resin, chlorinated paraffin, chlorinated polypropylene, vinyl acetate resin or polycarbonate resin. Of the above, vinyl chloride resin is particularly preferable from the viewpoint of impurities.

For the thermal decomposition of these organic polymers, granules or powders of any kind are used in an inert atmosphere such as argon gas for 20 times.
The heating is performed at 0 to 500 ° C. for 30 minutes or more. However, it is preferred not to completely carbonize.

The desirable temperature and time for this heating differ depending on the heating device and the type of organic polymer, but the atomic ratio of carbon atoms and hydrogen atoms (hereinafter referred to as C / H ratio) in the decomposition product is eventually 0.
It may be determined by experiments so that it falls within the range of 8 to 1.5, preferably 0.9 to 1.2.

A solvent is added to the pitch-like substance (hereinafter referred to as PC substance) thus obtained to dissolve it, and the concentration is 200 to 500.
Make a solution of g /. The solvent is preferably an aliphatic chlorine-based solvent, especially trichlene, from the viewpoint of increasing the solubility of the PC substance and improving the productivity of the boat member. If insoluble matter remains, it is filtered to remove the insoluble matter. In particular, when it is desired to enhance the effect of preventing cracks, it is also preferable to add a heat-resistant inorganic powder such as graphite or silicon carbide to the solution as an aggregate.

The solution is applied to the surface of the boat member. The boat member is preferably a commercially available graphite block having a density of 1.7 to 1.9 g / cm ³ . The method of application is ultrasonic impregnation, brush coating, spraying, dipping and the like. Relatively low temperature (50
It is preferable to dry at about 100 ° C.

Then, under an inert atmosphere such as nitrogen or argon, 800 ~
The PC substance on the surface of the graphite member is vitrified by heating and firing at 1300 ° C. for 30 minutes or more.

The boat member thus obtained has a hard surface, and since the open pores are completely filled and covered with a dense and high-purity layer, there is no separation of graphite powder, and there is also no volatilization of impurities from the inside. Further, the incorporation of impurities into the open pores can be completely suppressed.

(Examples) Hereinafter, examples and comparative examples will be described.

Example A boat member, that is, a boat body 1, a slider 2 and a boat lid 3 of a liquid phase epitaxial growth apparatus shown in FIGS. 1 and 2 were made of high-purity graphite (T-6 manufactured by Ibiden Co., Ltd.).
P and density 1.90 g / cm ³ ) were prepared by machining as follows. That is, the boat body has a total length of 150 mm and a width of 20.
A rectangular parallelepiped having a size of 20 mm and a height of 20 mm was provided with four square holes to form a solution reservoir 4.

A gap for inserting the slider 2 in the longitudinal direction of the boat was provided near the bottom surface of the boat body. The solution reservoir has no bottom and has a structure in which the outflow of the solution is blocked by the inserted slider. The slider is 15mm wide and 300mm long,
It was a strip with a thickness of 3 mm, and was formed with a plurality of indentations 5 on which a single crystal plate was placed. The boat lid 3 has a plate shape of 15 mm × 15 mm × 3 mm, and the periphery of its back surface is thin to prevent the lid from slipping.

Vinyl chloride resin powder (SS-11, Denki Kagaku Kogyo Co., Ltd.)
0) 100 g was placed in a quartz flask with a volume of 1 liter,
The vinyl chloride resin was pyrolyzed by heating at a temperature of 390 ° C. for 2 hours under a nitrogen gas atmosphere. PC obtained
The C / H ratio of the substance is 1.05 as a result of measurement with a CHN coder.
It was.

The PC material was lightly crushed using a ball mill (the inner wall of the pot and the surface of the ball were covered with nylon) to obtain particles having a diameter of 1 mm. The particles were dissolved in trichlene to give a solution having a concentration of 300 g /. This solution was applied to the surface of the graphite member using a nylon brush.

Then, each member coated with the PC substance was put into an electric furnace, and heated and baked at a temperature of 1200 ° C. for 60 minutes in a nitrogen atmosphere to vitrify the coated PC substance. The coating amount of glassy carbon was calculated from the weight change before and after coating, and the coating and firing of the PC substance was repeated until the coating amount reached 3 mg / cm ² . The boat member thus obtained was assembled and placed in the liquid phase epitaxial apparatus shown in FIG. 3, and GaAs was epitaxially grown as described below. That is, a lump of gallium was put into the solution reservoir 4 of the boat body 1 at room temperature and the boat lid 3 was placed. The slider 2 has a GaAs substrate as a raw material for solution preparation and an epitaxial growth target.
A GaAs substrate was placed.

First, a boat member in which a slider was adjusted so that the bottom of the solution reservoir was in a position where it did not contact any substrate was placed in the quartz reaction tube 6 and the quartz reaction tube was evacuated. Next, high-purity hydrogen was flown to raise the temperature of the electric furnace 11. After the gallium was melted, first, the GaAs substrate for the raw material was moved under the solution reservoir to saturate GaAs in the gallium, and then cooling of the gallium solution was started. Next, the GaAs substrate to be epitaxially grown was moved to the bottom of the solution reservoir, and cooling was continued at a constant rate to grow GaAs on the substrate.

The GaAs single crystal plate used here was LEC (Liquid Encaps
non-doped semi-insulating property made by the ulated Czochralski method
GaAs substrate (2 ° off-cut from (100) surface in <110> direction)
Was used, and the GaAs substrate for epitaxial growth had a single-sided mirror finish. The growth start temperature was 700 ° C., the initial supercooling temperature was 10 ° C., the temperature decrease rate was 0.7 ° C./min, and the epitaxial film growth rate was 5 μm / hour.

The growth of the above epitaxial film under the same method and under the same conditions
It was a round trip. With respect to the obtained epitaxial film, the conductivity type was confirmed and the carrier concentration, mobility, carbon concentration and oxygen concentration of the epitaxial film were measured by the following methods. The results are shown in the table.

Confirmation of conductivity type, measurement of carrier concentration, measurement method of mobility Constant current power supply section (Keisley 220 type), switching matrix section (Keithley 7058 type), voltage measuring section (Keithley 195 type) And Juan de Pau (Van de
r pauw) measuring device, applied current 1nA, applied magnetic field 5K
It was measured under the conditions of Gauss and temperature of 300K.

Ion microanalyzer (IMA2 type manufactured by Hitachi Ltd.) for measuring carbon content and oxygen content
The carbon is an oxygen ion spatula and the total ion current is 2 nA.
Oxygen was measured under a condition of total ion current of 2 nA with an argon ion spatula under the above condition.

Comparative Example A boat member was formed in the same shape and size as those of the examples, but was assembled and used without being coated with glassy carbon and washed with a chlorofluorocarbon solvent. The epitaxial film was grown 5 times under the same conditions as in the example, and the characteristics of the obtained epitaxial film were measured. The results are shown in the table.

From the above results, when the boat member coated with glassy carbon of the present invention is used, the obtained epitaxial growth film has n type conductivity, low carrier concentration, high mobility, and high carbon content. It is clear that the oxygen concentration decreases. On the other hand, when a boat member not coated with glassy carbon is used, the epitaxial growth film has a p-type conductivity, a high carrier concentration, a low mobility, and a high carbon / oxygen concentration. Become.

(Effect of the invention) Since the graphite member for liquid phase epitaxial growth apparatus of the present invention does not have open pores on the surface, adsorption of water and the like does not occur, and since graphite powder is not separated, epitaxy caused by these The quality of the epitaxial growth film can be kept high without deterioration of the characteristics of the epitaxial growth film. Moreover, since the glassy carbon is formed from the thermal decomposition product of the organic polymer dissolved in the aliphatic chlorine-based solvent, the product of the present invention can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an example of a boat member according to the present invention. FIG. 2 is a perspective view of an example of the boat member of the present invention. FIG. 3 is a sectional view of a liquid phase epitaxial growth apparatus,
Fig. 7 shows how to use the boat member of the present invention. Reference numeral 1 ... Boat main body, 2 ... Slider, 3 ... Boat lid, 4 ... Solution reservoir, 5 ... Dimple, 6 ... Quartz reaction tube, 7 ... Vacuum pump connection tube, 8 ... Hydrogen gas supply Pipe, 9 ... Exhaust pipe, 10 ... Slider operating rod, 11 ...
…Electric furnace

Continuation of the front page (56) Reference JP-A-54-158165 (JP, A) JP-A-60-103087 (JP, A) JP-A-53-124189 (JP, A) JP-B-52-39684 (JP , B2)

Claims (1)

[Claims] 1. A graphite member coated with glassy carbon, wherein the glassy carbon is formed from a thermal decomposition product of an organic polymer dissolved in an aliphatic chlorine solvent. A boat member for a liquid phase epitaxial growth apparatus, which is characterized in that