JPH0637353B2 - Method and apparatus for growing silicon carbide single crystal - Google Patents

Description

The present invention relates to a silicon carbide single crystal growth method and apparatus. More specifically, the present invention relates to a silicon carbide single crystal growth method and apparatus for efficiently growing a large area silicon carbide single crystal useful for applications such as blue light emitting diodes.

(Prior Art) Conventionally, as a silicon carbide single crystal growth method, the Acheson method,
Liquid phase method, chemical vapor phase method, sublimation recrystallization method and the like are known. Among these, the Acheson method is a method of heating a mixture of silica and coke in an electric furnace to precipitate crystals, which has many impurities and the growth is due to spontaneous nucleation. It is difficult to control the crystal plane. In the liquid phase method and the chemical vapor phase method, it is possible to control the crystal shape and the crystal plane because epitaxial growth is possible, but both methods have a very slow crystal growth rate and cannot obtain a large silicon carbide single crystal. Have difficulty.

As a crystal growth method by sublimation recrystallization, a Rayleigh method in which a raw material silicon carbide is sublimated in a graphite crucible having an appropriate temperature distribution and recrystallized in a low temperature portion in the crucible, and a silicon carbide substrate is formed in a low temperature portion on the crucible. Place and place an inert gas atmosphere at 100
The method of Tyroff et al. For gradually reducing from about Torr to vacuum has been known. However, in the Rayleigh method, it is difficult to form crystals and control the crystal planes because the crystals grow due to spontaneous nucleation. On the other hand, in the method of Tyroff et al., The growth rate of the crystal is extremely high, and it is possible to control the crystal formation and the crystal plane to grow the crystal on the substrate, but the crystal easily grows in a columnar shape,
Crystal planes of various shapes and directions appeared and the crystallinity was poor. As a method for further improving this point, Japanese Patent Publication No. 59
No. 48792, in heating and sublimating silicon carbide powder in an inert gas atmosphere to grow a silicon carbide single crystal on a silicon carbide single crystal substrate, the temperature and temperature difference between the silicon carbide powder and the silicon carbide substrate, Further, it has been proposed to control the pressure of the inert gas, and it is said that a good quality and large-sized silicon carbide single crystal can be grown at a high speed.

In the method as described in Japanese Patent Publication No. 59-48792, it is true that a good quality silicon carbide single crystal can be grown on a single crystal substrate, but it is made of graphite which holds the silicon carbide single crystal substrate. Polycrystalline silicon carbide also grows on the crucible lid, so that the portion where the single crystal grows is limited to the portion where the single crystal substrate exists. In addition, as the crystal growth progresses, the polycrystal generated in the lid part also continues to grow, so the polycrystal may bite into the single crystal part and grow, and in this case, the area of the single crystal becomes rather small. . Further, if a polycrystal grows in the surroundings, it becomes necessary to cut off the polycrystal portion when the single crystal is taken out, resulting in complication of the process.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide an improved method and apparatus for growing a silicon carbide single crystal. The present invention also relates to a method of sublimating silicon carbide powder in an inert gas atmosphere to grow a silicon carbide single crystal on a silicon carbide substrate, which prevents generation of polycrystals in the crucible lid portion during the growth of the silicon carbide single crystal. An object of the present invention is to provide a method and an apparatus for growing a silicon carbide single crystal that suppresses the growth of only single crystal silicon carbide and obtains a good quality silicon carbide single crystal having a large cross-sectional area.

(Means for Solving the Problems) The above-described objects are to provide a method for growing a silicon carbide single crystal on a silicon carbide single crystal substrate by sublimating silicon carbide powder in an inert gas atmosphere in a graphite crucible. A silicon carbide single crystal substrate is attached to the central portion on the inner surface side of the graphite crucible lid that covers the upper end opening of the graphite crucible, and a graphite partition plate having an opening slightly smaller than the substrate and having the same shape as the crucible space section is formed. The substrate is placed in a crucible spaced 0.1 to 2.0 mm from the substrate, only the substrate is exposed to the crucible side without exposing the inner surface of the lid, and silicon carbide powder is inserted into the crucible. Heating the crucible at 2200 to 2400 ° C. in an inert gas atmosphere and maintaining the temperature of the silicon carbide single crystal substrate and the crucible lid at a temperature lower than that of the crucible and the graphite partition plate, This is achieved by a silicon carbide single crystal growth method which is a method for growing a single crystal on a silicon single crystal substrate.

The above-mentioned purposes also include a crucible that also functions as a heating element made of graphite,
A graphite crucible lid for covering the upper end opening of the crucible having a silicon carbide single crystal substrate mounting portion at the inner surface side central portion,
A graphite partition plate attached inside the crucible, having a hole with a predetermined diameter in the central portion, heating means for heating the crucible, and a vacuum system for inserting the crucible and controlling the atmosphere to a vacuum or an inert gas atmosphere. It is also achieved by a silicon carbide single crystal growth apparatus characterized by having.

The present invention also provides a crucible that also serves as a heating element made of graphite, a graphite crucible lid that covers the upper end opening of the crucible having a silicon carbide single crystal substrate attachment portion in the center of the inner surface, and the inner surface of the crucible lid. A partition plate made of graphite having an opening with a predetermined diameter in the central part, which is attached by a height-adjustable graphite fitting, a heating means for heating the crucible, and a vacuum or an inert gas by inserting the crucible. 1 shows a silicon carbide single crystal growth apparatus having a vacuum system controlled to an atmosphere. The present invention further comprises a crucible that also serves as a heating element made of graphite, a graphite partition plate having an opening of a predetermined diameter in the central part integrally attached to the upper inner peripheral surface of the crucible, and an inner surface side central part. A graphite crucible lid covering the upper opening of the crucible having a silicon carbide single crystal substrate mounting portion, a heating means for heating the crucible, and a vacuum system for inserting the crucible to control a vacuum or an inert gas atmosphere. 1 shows a silicon carbide single crystal growth apparatus characterized by having.

(Operation) The method for growing a silicon carbide single crystal of the present invention is a raw material powder that is placed in a graphite crucible lid that covers a top opening of a crucible by sublimating silicon carbide powder in a graphite crucible in an inert gas atmosphere. A silicon carbide single crystal is deposited and grown from a sublimated silicon carbide gas on a silicon carbide single crystal substrate held at a slightly lower temperature. In the vicinity of the crucible lid to which the silicon carbide single crystal substrate is attached, A graphite partition plate having an opening slightly smaller than the substrate and having the same shape as the crucible space cross section is arranged. Therefore, the crucible lid itself is not exposed on the crucible side, and only the silicon carbide single crystal substrate is exposed. If the temperature of the graphite partition plate is set higher than that of the single crystal substrate, the sublimated silicon carbide gas will not be deposited on the graphite partition plate and will be exposed at a lower temperature. Concentrated deposition on a single crystal substrate. Therefore, the generation of polycrystals is suppressed, only the single crystal grows, and the single crystal can also spread in the horizontal direction, so that the size of the single crystal can be increased.

Hereinafter, the present invention will be described in more detail based on embodiments.

FIG. 1 shows an example of a single crystal growth apparatus preferably used in the method for growing a silicon carbide single crystal of the present invention.

As shown in FIG. 1, the single crystal growth apparatus includes a crucible 1 which also serves as a heating element made of graphite and has a shape of, for example, a circular shape or a box shape, and a mounting portion of a silicon carbide single crystal substrate at the center of the inner surface side. A crucible lid 6 made of graphite for covering the upper end opening of the crucible 1 having 10 and an opening of a predetermined diameter in the central portion, which is attached to the inner surface side of the crucible lid 6 by a height adjustable graphite attachment 7. It has a graphite partition plate 5 having the same shape as the internal space cross section of the crucible 1 having the holes 11. Opening 1 provided in the central part inside the graphite partition plate 5
1 is slightly smaller than the silicon carbide single crystal substrate 3 attached to the silicon carbide single crystal substrate attaching portion 10, and its shape depends on the shape of the silicon carbide single crystal to be obtained, but is preferably In order to obtain a circular silicon carbide single crystal ingot which is particularly useful in application, the circular ingot is used. Furthermore, in the single crystal growth apparatus of this embodiment, the outer peripheral surfaces of the crucible 1 and the crucible lid 6 are covered with a heat insulating material 8 made of graphite felt, and further vacuum exhaust is performed by a vacuum exhaust device (not shown). The internal atmosphere can be set to 1 from atmospheric pressure with an inert gas such as Ar or Xe gas.
It is contained in a container 12 that can be controlled to about Torr. Further, the container is provided with heating means (not shown) for heating the crucible such as a high frequency induction coil wound outside the container. Therefore, the heating means such as the high frequency induction coil and the heat insulating material 8 are arranged so that when the crucible 1 is heated by such a heating means, the crucible 1 and the graphite partition plate 5 have the same temperature. 6 and the silicon carbide single crystal substrate 3 are more preferably kept at a temperature lower than the temperature of the crucible 1 and more preferably 50 to 100.
The arrangement is adjusted so that the temperature is kept low at about ℃.

FIG. 2 shows another example of the silicon carbide single crystal growth apparatus of the present invention.

The embodiment shown in FIG. 2 has an opening 1 with a predetermined diameter in the center.
1, except that the graphite partition plate 5 having 1 is directly attached to the inner peripheral surface of the crucible 1 without being attached to the crucible lid 6 as in the embodiment shown in FIG. It has the same structure as that in the embodiment shown in FIG.

That is, the single crystal growth apparatus in this embodiment has a crucible 1 also serving as a heating element made of graphite, and the crucible 1 having a mounting portion 10 for a silicon carbide single crystal substrate in the center portion on the inner surface side.
A crucible lid 6 made of graphite for covering the upper end opening of the crucible and a partition plate 5 made of graphite having an opening 11 of a predetermined diameter in the central part integrally attached to the upper inner peripheral surface of the crucible 1. Cage,
The outer peripheral surfaces of the crucible 1 and the crucible lid 6 are covered with a heat insulating material 8 made of graphite felt, which can be further evacuated by a vacuum evacuation device (not shown) and the inner atmosphere can be an inert gas. Controllable container 12
It is put in. The container 12 is provided with heating means (not shown) for heating the crucible.

In order to grow a silicon carbide single crystal using such a single crystal growth apparatus, first, the silicon carbide powder 2 is housed in the crucible 1, while the silicon carbide single crystal substrate mounting portion 10 of the crucible lid 6 is placed. The silicon carbide single crystal substrate 3 is attached to the silicon carbide single crystal substrate 3 by a graphite attachment 9.

Further, in the case of the single crystal growth apparatus shown in FIG. 1, the graphite partition plate 5 having the opening as described above is attached to the crucible lid body 6 by the graphite partition plate fixture 7. At this time, the graphite partition plate 5 and the single crystal substrate 3 are 0.1 to
Partition plate attachment 7 so that it has a gap of 2.0 mm
Adjust and install. That is, when the distance between the graphite partition plate 5 and the single crystal substrate 3 exceeds 2.0 mm, when the silicon carbide powder 2 is sublimated while being kept at a high temperature, silicon carbide gas is deposited on the crucible lid 6. It is not desirable because polycrystalline silicon carbide is formed on the crucible lid 6, and if the distance is less than 0.1 mm, the silicon carbide single crystal substrate 3 and the crucible lid 6 are separated as described above. This is because it may be difficult to provide a temperature difference with the graphite partition plate 5. In the single crystal growth apparatus shown in FIG. 2, such a graphite partition plate 5 is integrally formed with the graphite crucible 1 in advance. In this case as well, a silicon carbide single crystal attached to the crucible lid 6 is formed. The space between the substrate 3 and the graphite partition plate 5 is to prevent the formation of polycrystalline silicon carbide on the crucible lid 6 and to prevent the silicon carbide single crystal substrate 3 and the crucible lid 6 from being formed.
In order to secure a temperature difference between the graphite partition plate 5 and the graphite partition plate 5.
1 to 2 mm.

After the crucible lid 6 having the silicon carbide single crystal substrate 3 and the graphite partition plate 5 attached thereto is placed on the crucible 1 containing the silicon carbide powder 2, or the silicon carbide single crystal substrate 3 is attached. The crucible lid 6 is replaced with silicon carbide powder 2
After covering the crucible 1 integrated with the graphite partition plate 5 containing the above, the inside of the system was degassed by a vacuum exhaust device (not shown), and an inert gas was introduced to create an inert gas atmosphere. Then, the crucible 1 is heated by a heating means (not shown) to sublimate the silicon carbide powder 2 to grow a single crystal.
At this time, until the temperature of the crucible 1 reaches a high temperature of 2200 to 2400 ° C., the inert gas atmosphere pressure is set to about 700 Torr in order to prevent evaporation of the silicon carbide powder, and after the temperature becomes sufficiently high, it becomes inactive. The gas pressure is gradually reduced and maintained at 1 to 100 Torr for several hours to grow a silicon carbide single crystal on the silicon carbide single crystal substrate. In addition,
If the heating temperature is lower than 2200 ° C., the sublimation of silicon carbide is not sufficient, while if it exceeds 2400 ° C., the growth of silicon carbide is hindered, which is not preferable. here,
As described above, the crucible lid 6 is not exposed to the silicon carbide gas that sublimes due to the presence of the graphite partition plate 5, and the graphite partition plate 5 is kept at a higher temperature than the silicon carbide single crystal substrate 3. Because of the sagging, the crystal growth is mainly performed on the silicon carbide single crystal substrate 3, and since the growth of the polycrystal is suppressed, it is particularly desirable that the crystal has a large cross-sectional area where the polycrystal is not attached. This makes it possible to manufacture a silicon carbide single crystal having a circular large cross-sectional area, which is extremely useful in industry.

In the method for growing a silicon carbide single crystal of the present invention, various kinds of silicon carbide powder can be used, but preferably silicon carbide powder such as a commercially available silicon carbide abrasive is treated with hydrofluoric acid. It is desirable to use one that is washed with a mixture of nitric acid to remove oxides and impurities attached to the surface, washed with pure water, dried, and further heat-treated at 1800 to 2000 ° C. in vacuum.

As a silicon carbide single crystal substrate, for example, an amorphous single crystal obtained as a by-product when industrially manufacturing a silicon carbide abrasive is shaped and polished, and a molten potassium hydroxide is used to remove polishing scratches. A single crystal substrate which has been etched with, dried by acid cleaning with aqua regia and hydrofluoric acid and then dried can be used. Needless to say, a single crystal substrate obtained by cutting a single crystal manufactured by the growth method of the present invention may be used. The usable silicon carbide single crystal substrate is not limited to the above.

(Examples) Hereinafter, the present invention will be described more specifically with reference to Examples.

Example 1 An attempt was made to grow a silicon carbide single crystal by using a single crystal growth apparatus having a structure as shown in FIG.

First, as the silicon carbide powder 2, a mixture of commercially available silicon carbide abrasives No. 54 and No. 80 in a ratio of 1: 1 was used, and this was mixed with a mixture of hydrofluoric acid and nitric acid (1: 1) for 10 minutes. After washing, wash with pure and replace with ethyl alcohol,
It was dried by a vacuum dryer and put in a graphite crucible 1 which had been heat-treated at 2400 ° C. in advance, and heated at 1800 to 2000 ° C. under a high vacuum of 10 ⁻⁶ to 10 ⁻⁷ Torr, and heat-treated for 10 minutes.

On the other hand, the silicon carbide single crystal substrate 3 as a seed crystal is a hydroxylated product obtained by polishing a single crystal obtained as a by-product in the process of industrially manufacturing a silicon carbide abrasive and polishing and melting it at 500 ° C. Etching in potassium to remove polishing scratches, cleaning with pure water, cleaning with aqua regia for 15 minutes, cleaning with pure water, further cleaning with hydrofluoric acid for 5 minutes and pure water cleaning, and then nitrogen blowing The dried product was used. The shape of the silicon carbide single crystal substrate 3 is 10 m in diameter of the graphite partition plate 5.
A polygonal shape larger than the opening 11 of m was used.

The single crystal substrate 3 pretreated as described above is attached to the graphite crucible lid 6 by the graphite attachment 9, and the graphite partition plate 5 is placed at a distance of 0.5 mm from the silicon carbide single crystal substrate 3. It was prepared so that A graphite crucible 1 containing the silicon carbide powder 2 that has been heat-treated as described above is covered with a crucible lid 6 to which a silicon carbide single crystal substrate 3 is attached, graphite felts 8 are attached to the periphery and top and bottom, and a quartz container is provided. 12
And was evacuated to a high vacuum of 6 × 10 ⁻⁷ Torr to remove residual gas as impurities.

Next, high-purity Ar gas was introduced into the container 12, and the pressure was adjusted to 7
The temperature was maintained at 00 Torr, and the crystal growth furnace system was heated by high frequency induction heating so that the temperature of the wall surface of the crucible 1 became 2200 to 2400 ° C. The wall temperature of the crucible was measured from the outside of the container 12 using a two-color thermometer through a hole made in the felt 8 made of graphite. When the temperature of the crucible wall surface reached a sufficiently high temperature and became constant, the Ar gas pressure in the container 12 was gradually reduced from 700 Torr to 10 Torr in 1 hour.
Crystal growth was carried out at 0 Torr for 3 hours. When terminating the crystal growth, there is a possibility that crystal growth will occur at a low temperature in the process of lowering the crucible temperature. Therefore, when terminating the crystal growth, the Ar gas pressure is raised to atmospheric pressure and carbonization is performed. Prevented evaporation of silicon.

As a result, a silicon carbide single crystal ingot 4 having a diameter of about 5 mm and a diameter of about 5 mm was grown in the circular opening 11 in the central portion of the graphite partition plate 5 by about 20%. On the other hand, although some silicon carbide polycrystals were slightly grown on the graphite partition plate 5, they were not grown to the extent that they hinder the growth of the single crystal, and only the single crystal to which the polycrystal was not attached was I was able to grow.

Example 2 An attempt was made to grow a silicon carbide single crystal by using a single crystal growth apparatus having a structure as shown in FIG.

The silicon carbide powder 2 and the silicon carbide substrate 3 that is a seed crystal used were the same as those used in Example 1.
A silicon carbide single crystal substrate 3 having a thickness of 1.0 mm is used, and the crucible 1 and the graphite partition plate 5 are integrally molded so that the distance between the single crystal substrate 3 and the partition plate 5 is 1.2 mm. The crucible 1 containing the heat-treated silicon carbide powder 2 is covered with the lid 6 having the silicon carbide single crystal substrate 3 attached thereto, and the graphite felt 8 is attached to the periphery and the upper and lower sides of the crucible 1. It was introduced into the container 12 and evacuated to a high vacuum of 6 × 10 ⁻⁷ Torr to remove residual gas.

Then, Ar gas was introduced, the temperature was raised, and the pressure was reduced in the same manner as in Example 1 to perform crystal growth. As a result, the diameter of the circular opening 11 at the center of the graphite partition plate 5 was 13 mm.
A silicon carbide single crystal ingot 4 having a diameter of 20 mm and a thickness of about 18 mm, which is larger by about 50%, was grown. On the other hand, although some silicon carbide polycrystals were slightly grown on the graphite partition plate 5, they were not grown to the extent that they hinder the growth of the single crystal, and only the single crystal to which the polycrystal was not attached was I was able to grow.

(Effects of the Invention) As described above, according to the present invention, a silicon carbide single crystal substrate is attached to a central portion on the inner surface side of a graphite crucible lid that covers an upper end opening of a crucible, and an opening slightly smaller than the substrate is formed. A graphite partition plate having the same shape as that of the crucible space section is installed in a crucible with a distance of 0.1 to 2.0 mm from the substrate, and only the substrate is exposed without exposing the inner surface of the lid. It is exposed to the crucible side, silicon carbide powder is inserted into the crucible, and the crucible is set at 2200-24 in an inert gas atmosphere.
Carbonization for growing a single crystal on a silicon carbide single crystal substrate by heating and maintaining the temperature at 00 ° C. and maintaining the temperature of the silicon carbide single crystal substrate and the crucible lid lower than the temperatures of the crucible and the graphite partition plate. Since it is a silicon single crystal growth method, it is possible to grow a good-quality silicon carbide single crystal ingot with a large cross-sectional area where no polycrystal is attached to the periphery by using a relatively simple apparatus. It is possible to supply a silicon carbide single crystal wafer having a circular large cross-sectional area, which is effective for various applications such as a light emitting diode.

The present invention also includes a crucible that also serves as a heating element made of graphite, a graphite crucible lid that covers the upper end opening of the crucible having a silicon carbide single crystal substrate attachment portion in the inner surface side central portion, and is attached inside the crucible. Also, a graphite partition plate having an opening of a predetermined diameter in the central portion, and heating means for heating the crucible,
A silicon carbide single crystal growth apparatus having a vacuum system in which a crucible is inserted to control a vacuum or an inert gas atmosphere, and thus is preferably used in the single crystal growth method as described above. Despite its simple structure, a good quality silicon carbide single crystal ingot having a large cross-sectional area can be grown.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the silicon carbide single crystal growth apparatus of the present invention in the use stage, and FIG. 2 is another example of the silicon carbide single crystal growth apparatus of the present invention in the use stage. It is sectional drawing which shows typically. DESCRIPTION OF SYMBOLS 1 ... Crucible, 2 ... Silicon carbide powder, 3 ... Silicon carbide single crystal substrate, 4 ... Silicon carbide single crystal ingot, 5 ... Graphite partition plate, 6 ... Crucible lid, 10 ... Silicon carbide Single crystal substrate mounting part, 11 ... Open hole.

Front Page Continuation (72) Inventor Masaetsu Takahashi 16-1, Shineicho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Ricoh Central Research Institute Co., Ltd. (JP, U) Actually open 61-43275 (JP, U)

Claims (3)

[Claims] 1. A method of growing a silicon carbide single crystal on a silicon carbide single crystal substrate by sublimating silicon carbide powder in an inert gas atmosphere in a graphite crucible, the graphite crucible covering an upper end opening of the crucible. A silicon carbide single crystal substrate is attached to the central portion on the inner surface side of the lid body, and a graphite partition plate having an opening slightly smaller than the substrate and having the same shape as the crucible space cross section is formed from the substrate 0.1 to 2. The crucible is placed in a crucible with an interval of 0 mm, the substrate is exposed to the crucible side without exposing the inner surface of the lid, silicon carbide powder is inserted into the crucible, and the crucible is placed in an inert gas atmosphere. A single crystal is grown on a silicon carbide single crystal substrate by heating and holding it at 2200 to 2400 ° C. and keeping the temperature of the silicon carbide single crystal substrate and the crucible lid lower than the temperatures of the crucible and the graphite partition plate. Those in which a silicon carbide single crystal growth method of. 2. The single silicon carbide powder according to claim 1, wherein the silicon carbide powder is a silicon carbide powder that has been treated with a mixture of hydrofluoric acid and nitric acid, washed, dried, and then heat-treated at 1800 to 2000 ° C. in vacuum. Crystal growth method. 3. A crucible that also functions as a heating element made of graphite, a crucible lid made of graphite that covers an upper end opening of the crucible having a mounting portion for a silicon carbide single crystal substrate at an inner surface side center portion, and a crucible attached inside the crucible. It is characterized by having a graphite partition plate having an opening with a predetermined diameter in the center part, heating means for heating the crucible, and a vacuum system for inserting the crucible and controlling the atmosphere to a vacuum or an inert gas atmosphere. Silicon carbide single crystal growth apparatus.