JPH06191998A - Method for growing silicon carbide single crystal and device for growing the same - Google Patents

Abstract

PURPOSE:To save labors for judging the direction of the crystal on the cutting and grinding of the crystal and simplify a process for producing crystal products by subliming silicon carbide raw material powder for the growth of the crystal on a substrate under prescribed conditions in a crucible having a prescribed inner shape. CONSTITUTION:A crucible 1 having a structure in which a part of the cylindrical shape wall of the crucible 1 is flat, the flat part being tilted from the opening side of the crucible toward its bottom side, is prepared. The substrate 3 of a seed crystal is attached to the lid 2 of the crucible 1 so that the direction of the crystal is directed in the rectangular direction against the flat part. The crucible 1 is held at a temperature of 2100-2400 deg.C in an inert gas atmosphere having a pressure of <=27Kpa to sublime the silicon carbide raw material powder 4 charged onto the bottom of the crucible and to grow a silicon carbide single crystal on the substrate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for growing a high-quality silicon carbide single crystal, and more particularly to efficiently producing a large area and highly homogeneous silicon carbide single crystal such as a blue light emitting diode. The present invention relates to a growth method and a growth apparatus for growing.

[0002]

2. Description of the Related Art Silicon carbide is a material which is excellent in chemical resistance such as acid resistance and alkali resistance, and is excellent in durability which is not easily damaged by high energy rays, and is widely used as a semiconductor material. Silicon carbide single crystal has a characteristic of polymorphism, and the forbidden band width can be arbitrarily selected from 2.2 eV to 3.3 eV according to the polymorphism, and its operable temperature range is also extremely higher than that of other materials. Due to its wide range, the use of silicon carbide in semiconductor materials has long been in use before the 1960s. Here, the polymorph means a material having the same chemical composition but different crystal structure, or a material exhibiting the phenomenon.

By the way, in order to industrially utilize silicon carbide, it is required to be a high quality single crystal having a certain size. Therefore, conventionally, by utilizing a chemical reaction called the Athison method, or by using a sublimation recrystallization method called the Rayleigh method to grow a single crystal to the size of the target scale, or by these methods A method has been adopted in which the obtained single crystal of silicon carbide is used as a substrate and silicon carbide is grown on the substrate by a vapor phase epitaxial growth method or a liquid phase epitaxial growth method to obtain a target single crystal.

In particular, as a means for growing a bulk single crystal, a silicon carbide single crystal of a certain suitable size is used as a seed crystal in a graphite crucible, and the raw material silicon carbide powder is sublimated in a reduced pressure atmosphere. The improved Rayleigh method in which the crystals are recrystallized on a seed crystal and grown is widely used.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The conventional method as shown in 48792 makes it possible to obtain a good quality single crystal. However, the silicon carbide crystal obtained by crystal growth has a shape close to a cylinder,
Once the crystal obtained as a result of growth is removed from the growth apparatus, the crystal orientation is unclear, which is inconvenient.

It is well known that in the case of vapor phase epitaxial growth of silicon carbide on a silicon carbide substrate, a significant difference appears in the surface morphology and crystallinity of the crystal film obtained by epitaxial growth depending on the crystal plane orientation of the substrate [S. Nishino et al. , Late Ne
ws Abst. , 16th Conf. SSDM, L
D-1-4 (1984). ]. Therefore, strict accuracy is required for selecting the plane orientation of the silicon carbide substrate.

Therefore, in order to obtain a wafer having a plane of a specific crystal plane from the grown silicon carbide single crystal ingot (in particular, a wafer inclined by a few degrees in a specific direction of a certain crystal plane). After the crystal plane orientation was determined by the X-ray diffraction method, a very complicated process of cutting and polishing the crystal had to be performed, which was uneconomical.

The present invention has been made to solve the above problems, and is a method for growing a silicon carbide single crystal capable of efficiently forming a wafer crystal in which a specific crystal plane is strictly determined with good controllability. And a growth apparatus.

[0009]

In order to achieve the above object, the present invention comprises the following growth method and growth apparatus.

The present invention is a method for growing a silicon carbide single crystal on a silicon carbide single crystal substrate by sublimating silicon carbide powder in an inert atmosphere in a graphite crucible, wherein the graphite crucible has a cylindrical internal structure. Part of which has a flat structure, and the flat part has a structure in which the flat part is inclined from the crucible opening side toward the crucible bottom side, and a seed crystal of silicon carbide fitted in a direction perpendicular to the flat part of the crucible is used. Installed, heated and maintained at a desired temperature in an inert gas atmosphere, and the crucible lid and the silicon carbide single crystal substrate attached to the lid are heated to a temperature lower than that of the silicon carbide raw material powder filled in the bottom of the crucible. It is characterized by holding and growing a silicon carbide single crystal on a silicon carbide single crystal substrate in a reduced pressure atmosphere.

In particular, in order to obtain high-quality silicon carbide having a large band gap (in other words, 4H or 6H polymorph), a seed crystal of silicon carbide is used in the above-mentioned method for growing a silicon carbide single crystal. Set the inert gas atmosphere to 2
The method is characterized in that the silicon carbide single crystal is grown on a silicon carbide single crystal substrate in a reduced pressure atmosphere of 27 kPa or less by heating and holding at a temperature of 100 to 2400 ° C.

Further, in the growth apparatus, a part of the cylindrical internal structure is a flat structure, and the flat part has a structure in which the flat part is inclined from the opening side of the crucible toward the crucible bottom side, and the inner surface of the crucible. A graphite crucible lid body to which the silicon carbide single crystal substrate is attached to the side, heating the graphite crucible assembly, and means for maintaining the temperature, a high vacuum atmosphere for the graphite crucible assembly, or, And a means for maintaining and controlling in an inert gas atmosphere.

[0013]

The principle of growth of a silicon carbide single crystal according to the present invention is that a silicon carbide seed crystal attached to the lid of a crucible is obtained by sublimating silicon carbide powder in a depressurized atmosphere of an inert gas inside a graphite crucible. The purpose is to grow a single crystal by recrystallization on a substrate.

By sublimation recrystallization based on the seed crystal, the crystal is not only perpendicular to the seed crystal (assuming the Z-axis direction in the Cartesian coordinate system) but also two horizontal directions (X The growth is also freely spread in the axial direction and the Y-axis direction). However, due to the relationship between the inner diameter of the crucible and the size of the seed crystal, a region where free growth is hindered is created, but the crystal can only grow in a shape along the crucible shape. Therefore, in the present invention, a crystal having a shape as shown in FIG. 3 can be obtained by utilizing the above phenomenon and forming a flat wall structure in advance in a portion where free growth is hindered by the crucible shape. .

That is, since the crystal orientation of the seed crystal coincides with the portion of the grown crystal where the free crystal is obstructed (hatched portion in FIG. 3), if the crystal orientation is attached when the seed crystal is attached, the flat portion The crystal plane of can be controlled. In other words, it is possible to know the crystal orientation of a single crystal without investigating the crystal orientation of the single crystal by an X-ray diffraction method, and by cutting the bulk single crystal in a target direction and polishing it, it is possible to obtain a semiconductor with good workability and at low cost. A silicon carbide single crystal wafer suitable for device growth can be supplied.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to FIGS. FIG. 1 is a schematic view of a carbon-silicon single crystal growth cell, and FIG. 2 is a schematic view of a growth apparatus.

First, the (00.1) plane of silicon carbide is <11.
・ The substrate is 5 ° off in the 0> direction, and the crystal polymorphism is 6H.
An example for obtaining the above silicon carbide single crystal is shown. As shown in FIGS. 1 and 2, the flat portion extends from the opening toward the bottom.
Using a graphite crucible body 1 having a structure inclined at an angle of °, a silicon carbide single crystal was grown. As raw material powder 4 of silicon carbide, commercially available # 240 silicon carbide powder (having an average particle diameter of about 30 μm) as a polishing material was oxidized in air and then stirred in hydrofluoric acid for 1 hour. After the transition metal-based impurity element mixed in the raw material was dissolved and removed, it was sufficiently washed by decantation with water, and dried by heating in a reduced pressure atmosphere. A graphite crucible 1 previously heat-treated at a high temperature of 2000 ° C. for 1 hour in a high vacuum atmosphere was filled with the above-mentioned acid-treated raw material silicon carbide powder 4, and a high-vacuum induction furnace 5 was provided with a high vacuum by an exhaust device 5. To 1500 ° C for 3
A high temperature heating vacuum heat treatment was performed by heating and holding for 0 minutes.

On the other hand, a silicon carbide single crystal substrate 3 which is a seed crystal
In addition, a single crystal obtained as a by-product in the process of industrially manufacturing a silicon carbide abrasive is used as a seed crystal, and a single crystal with an extremely low carrier concentration obtained by the sublimation recrystallization method is cut out and polished. The product was thermally oxidized in a wet oxygen atmosphere to remove polishing scratches, surface-treated with an acid, washed with water and dried.

The seed crystal substrate is placed on the lid 2 of the single crystal growth apparatus 1 in which the raw material silicon carbide powder is heated and vacuum-treated at a high temperature <11.
-Install so that the 0> direction is perpendicular to the flat part of the crucible, and set the single crystal growth apparatus 1 and the chamber 7 to 8
The residual gas was removed by evacuation to a vacuum degree of 0 μPa (0.6 μTorr) using the high vacuum evacuation device 5. High-purity Ar gas is supplied to the chamber 7 by the atmosphere gas supply device 8.
Introduced inside, at a pressure of 93 kPa (700 Torr),
The gas flow rate is controlled using the pressure control device 9 so that the flow rate is 200 sccm, and the radiation thermometer 10 measures the surface temperature of the crucible lid body 2 by the high frequency induction heating device 6 to 2100 ° C. Control device 11 and heat insulating material 12
This was maintained for about 30 minutes until the whole system, which was controlled and heated so that the temperature was within ± 3 ° C., reached a steady state. Then, the pressure control device 9 is operated to reduce the atmospheric pressure to 3
The pressure was gradually reduced to 4.6 kPa (35 Torr) over a period of 0 minutes. When crystal growth was carried out for 4 hours in this pressure atmosphere, a bulk crystal having a length of 10 mm was obtained.

When the obtained crystal was taken out from the crucible, it was a cylindrical crystal having a flat part as shown by the slanted lines in FIG. When the crystallographic orientation of the shaded area in FIG. 3 was examined by an X-ray diffractometer, it was found that the (11.0) plane was a plane tilted by 5 ° in the <00.1> direction.

Next, after fixing the flat portion (hatched portion in FIG. 3) of this crystal and cutting it with a cutting machine,
A flat wafer crystal having a thickness of 0.5 mm was prepared by polishing the surface roughness to 1 μm or less. This wafer was subjected to thermal oxidation in a wet oxygen atmosphere, surface treatment by acid treatment, and then the orientation of crystal planes was examined by an X-ray diffractometer. As a result, the surface of this wafer is <11.
It was found that the surface was inclined by 5 ° in the 0> direction.

Although the growth method and the growth apparatus for obtaining the plane in which the (00.1) plane is inclined by 5 ° in the <11.0> direction have been described in the above embodiments, the present invention is not limited to this. However, the flat portion can be arbitrarily set according to the purpose depending on how many times the graphite crucible having the structure in which the flat portion is inclined from the opening to the bottom is used.

In general, it is known that the growth rate of crystals by the sublimation recrystallization method of silicon carbide depends on the pressure of the growth atmosphere. Furthermore, as a result of the research on the growth method in the present invention, it is aimed at now. High-quality silicon carbide with a large band gap, in other words, 3C is not included, 4H,
Alternatively, in order to obtain a silicon carbide single crystal composed of only a single crystal polymorph of 6H, in the growth method of the present invention, an inert gas atmosphere in which a seed crystal of silicon carbide is installed is set to a temperature of 2100 to 2400 ° C. Heated and held at 27 kPa
It has been found that it is desirable to grow a silicon carbide single crystal on a silicon carbide single crystal substrate in the following reduced pressure atmosphere.

[0024]

According to the present invention, a large-area silicon carbide single crystal wafer can be obtained without going through a process such as crystal orientation determination, and thus the complicated process which is conventionally required can be omitted. . That is, it becomes possible to inexpensively supply a substrate suitable for semiconductor component formation by a simple growth method.

[Brief description of drawings]

FIG. 1 is a schematic view of a silicon carbide single crystal growth cell used in an example of the present invention.

FIG. 2 is a schematic view of a crystal growth system used in an example of the present invention.

FIG. 3 is a schematic view of a bulk single crystal ingot obtained in an example of the present invention.

[Explanation of symbols]

 1 Graphite Crucible 2 Graphite Crucible Lid 3 Silicon Carbide Single Crystal Substrate 4 Silicon Carbide Raw Material Powder 5 Vacuum Evacuation Device 6 High Frequency Induction Heating Device 7 Chamber 8 Atmosphere Gas Supply Device 9 Pressure Control Device 10 Radiation Thermometer 11 Temperature Control Device 12 Thermal insulation

Claims (3)

[Claims] 1. A method for growing a silicon carbide single crystal on a silicon carbide single crystal substrate by sublimating silicon carbide powder in an inert atmosphere in a graphite crucible, wherein a part of a cylindrical internal structure of the graphite crucible is provided. Using a crucible having a flat structure, the flat portion of which has a structure inclined from the crucible opening side toward the crucible bottom side, and a silicon carbide seed crystal aligned in a direction perpendicular to the flat portion of the crucible is installed. , Heating and holding at a desired temperature in an inert gas atmosphere, and holding the crucible lid and the silicon carbide single crystal substrate attached to the lid at a temperature lower than the silicon carbide raw material powder filled in the bottom of the crucible. And growing a silicon carbide single crystal on a silicon carbide single crystal substrate in a reduced pressure atmosphere. 2. The method for growing a silicon carbide single crystal according to claim 1, wherein an inert gas atmosphere in which a seed crystal of silicon carbide is installed is heated and maintained at a temperature of 2100 to 2400 ° C., and 27
A method for growing a silicon carbide single crystal, which comprises growing a silicon carbide single crystal on a silicon carbide single crystal substrate in a reduced pressure atmosphere of kPa or less. 3. A crucible body made of graphite having a structure in which a part of a cylindrical internal structure has a flat structure, and the flat part is inclined from the opening side of the crucible toward the crucible bottom side, and silicon carbide is provided on the inner surface side. A graphite crucible lid to which the single crystal substrate is attached, a means for heating the graphite crucible assembly, and maintaining the temperature, a high vacuum atmosphere for the graphite crucible assembly, or an inert gas atmosphere And a means for maintaining and controlling the silicon carbide single crystal growth apparatus.