JP6338439B2 - Method for producing silicon carbide single crystal ingot - Google Patents

Description

  The present invention relates to a method for manufacturing a silicon carbide single crystal ingot in which a silicon carbide single crystal is grown by a sublimation recrystallization method using a seed crystal.

A silicon carbide single crystal having high thermal conductivity and a large band gap is a useful material as a substrate for electronic materials used at high temperatures and electronic materials that require high breakdown voltage.
As one method for producing such a silicon carbide single crystal, a sublimation recrystallization method (Rayleigh method) is known. In this sublimation recrystallization method, a silicon carbide single crystal is produced by sublimating a raw material silicon carbide powder at a high temperature exceeding 2000 ° C. and recrystallizing the generated sublimation gas (raw material gas) to a low temperature part. It is. Further, in this Rayleigh method, a method of producing a silicon carbide single crystal using a seed crystal composed of a silicon carbide single crystal is called an improved Rayleigh method (Non-patent Document 1), and is a bulk silicon carbide single crystal ingot. It is used for manufacturing.

  In this improved Rayleigh method, since a seed crystal is used, the nucleation process of the crystal can be optimized, and by adjusting the atmospheric pressure by an inert gas to about 10 Pa to 15 kPa, a silicon carbide single crystal The reproducibility of the growth rate and the like can be improved. For this reason, generally, an appropriate temperature difference is provided between the raw material and the crystal, and a silicon carbide single crystal is grown on the seed crystal. Further, the obtained silicon carbide single crystal (silicon carbide single crystal ingot) is used after being subjected to processing such as grinding, cutting, and polishing in order to obtain a standard shape as a substrate of an electronic material.

  Here, the principle of the improved Rayleigh method will be described with reference to FIG. Silicon carbide crystal powder used as the raw material 3 [usually, a silicon carbide crystal powder produced by the Acheson method is washed and pretreated. ] And a silicon carbide single crystal serving as a seed crystal 2 are placed and loaded into a graphite crucible 1. In the crucible 1, the raw material 3 of the silicon carbide raw material powder is loaded into the lower raw material loading portion in the crucible 1, and the seed crystal 2 of the silicon carbide single crystal is supported (mounted) on the lid member 1 a of the crucible 1. Is done. In order to sublimate the raw material 3 in an inert gas atmosphere such as argon (10 Pa to 15 kPa), the raw material 3 is heated to 2400 ° C. or higher. At this time, a temperature gradient is set in the crucible 1 so that the seed crystal 2 side is slightly cooler than the raw material 3 side. After being heated and sublimated, the raw material 2 is diffused in the direction of the seed crystal 2 by a concentration gradient (formed by a temperature gradient) and transported. The growth of the silicon carbide single crystal is realized by recrystallizing the source gas arriving at the seed crystal 2 on the seed crystal 2 to form a single crystal ingot 4. In addition, the code | symbol 5 is a heat insulating material in FIG.

  By the way, the diameter of the silicon carbide single crystal substrate is required to be increased when used as a substrate for manufacturing an electronic device. At the same time, when manufacturing a silicon carbide single crystal substrate, a large number of substrates can be manufactured from one ingot, and the productivity of the ingot obtained by crystal growth can be further increased during cutting and grinding. There is a need for longer lengths. However, when crystal growth is performed as described above, since a method is used in which a raw material is charged in a graphite crucible and heated, it is difficult to add the raw material during the crystal growth. Therefore, in order to produce a large-diameter and long-sized silicon carbide single crystal ingot, it is necessary to load a large amount of raw material powder in the raw material loading portion of the crucible as compared with small-diameter crystal growth. However, in order to increase the amount of the raw material, it is necessary to increase the depth of the raw material loading portion or to increase the diameter of the graphite crucible 1, and in addition, the raw material loaded in such a large amount is required. In order to use it effectively for crystal growth, it is necessary to efficiently heat the temperature of the entire raw material in the raw material loading section to the sublimation temperature.

  As a method for heating the crucible, generally, a graphite crucible is heated using high-frequency induction heating, the silicon carbide raw material in the crucible is heated through the heated crucible, and the temperature gradient described above is introduced into the crucible. Has been made to form. In addition, in this high frequency induction heating, since the induced high frequency current depends on the penetration depth of the high frequency, it has a heat generation distribution defined by the shape of the crucible, and a strong heat generation occurs near the surface of the crucible side surface. Heat is transferred to the raw material portion by heat conduction or heat radiation, thereby heating the raw material portion.

  When the raw material part is heated in this way, sublimation gas is generated from the high temperature part inside the raw material and crystal growth occurs, but temperature distribution is inevitably generated inside the raw material, and sublimation occurs at the high temperature part inside the raw material. Some of the source gas may recrystallize at a low temperature inside the source material and may not contribute to crystal growth. And in order to raise the temperature of this low temperature part and sublimate the raw material in that part, it is necessary to increase the current value of the induced current to make the temperature of the side wall part of the graphite crucible higher, When the temperature of the side wall portion of the crucible is increased, the entire crucible is increased in temperature, the temperature of the crucible in the portion in contact with the seed crystal is also increased, and the temperature of the seed crystal and the growing single crystal is also increased. The driving force for crystal growth based on the temperature gradient is reduced, and there is a problem of crystal growth stop that stops crystal growth in the middle.

  Therefore, some proposals have been made on the method of heating the crucible in the past. For example, in order to change the temperature distribution inside the raw material, the relative positions of the high frequency induction heating coil and the crucible are changed during crystal growth. A method is disclosed in which the raw material loaded is controlled so as not to remain in an unsublimated state (Patent Document 1). The method of Patent Document 1 is a method of sublimating a raw material by changing the heat generation distribution in the depth direction of the raw material loading portion by changing the relative position of the coil and the crucible. However, as described above, high-frequency induction heating generates strong heat near the surface of the crucible side surface. Therefore, when the diameter of the crucible is increased to produce a large-diameter silicon carbide single crystal, heat is generated by high-frequency induction heating. The distance from the crucible side wall portion to the raw material of the crucible center portion (portion in the vicinity of the central axis of the crucible) is increased compared to the case of growing a small-diameter silicon carbide single crystal, and the raw material at the crucible center portion is efficiently used. It becomes difficult to heat well. For this reason, in order to heat the raw material of the central part to the sublimation temperature, it is necessary to make the temperature of the side wall portion of the graphite crucible higher than in the case of a small diameter. When the temperature is raised, the above-mentioned problem of crystal growth stoppage becomes more prominent, and it is difficult to adopt for the purpose of efficiently heating the raw material in the center of the crucible whose diameter has been increased to increase the diameter. There is a problem.

  A method of controlling the shape of the side wall of the crucible at the part where the raw material is heated to make the temperature distribution inside the raw material uniform is disclosed (Patent Document 2). In this method, as the heat generation distribution on the crucible side wall changes, the heat generation distribution in the vicinity of the growing crystal portion also changes. Crystal growth is thought to proceed along the isotherm, and the heat generation distribution changes, so the growth surface shape of the growing crystal is also affected, and both temperature equalization of the raw material part and optimization of the temperature of the growing crystal part are compatible. There is a problem that optimization takes time or cannot be optimized.

  A method is disclosed in which the temperature distribution inside the raw material is changed during crystal growth so that the supply of the sublimation gas is not interrupted by moving the heat insulating material on the side surface of the portion for heating the raw material during crystal growth ( Patent Document 3). In this method, heating is still performed from the outer peripheral portion, and the temperature difference between the outer peripheral portion and the central portion of the raw material cannot be reduced, and in order to heat the raw material central portion, the temperature of the entire crucible must be increased. There is a problem that the temperature of the growing crystal part becomes high and the driving force for crystal growth becomes small.

  By allowing the members that make up the raw material part and the members that support the growing crystal to move independently, the sublimation gas path is changed and adjusted during crystal growth so that the supply of the raw material gas is not interrupted. Is disclosed (Patent Document 4). In this method, the raw material portion moves during crystal growth, the object to be heated moves, the heat generation distribution inside the raw material changes, and at the same time, the side wall near the central portion of the raw material can be heated. However, the movement of the object to be heated during crystal growth increases the complexity of the growth apparatus and at the same time disturbs the crystal growth due to the change in the supply of the source gas accompanying the movement of the object to be heated, that is, the defect There is a problem that the problem of occurrence or generation of different polytypes arises.

  Furthermore, the bottom part of the raw material part is heated by increasing the electric conductivity of the bottom part of the crucible in which the raw material is loaded to be higher than that of the side part, increasing the heat generation of the bottom part and raising the temperature of the bottom part of the raw material part. A method is disclosed (Patent Document 5). However, as described above, since the induced current flows through the side surface of the crucible, the portion near the center cannot be heated, and the arrangement of the bottom of the crucible and the raw material can change during crystal growth. Therefore, in order to raise the temperature of the bottom part of the raw material part, it is necessary to raise the temperature of the whole system. When the temperature of the whole system is raised, the temperature of the growing crystal part becomes high, and the crystal itself may be sublimated due to the high temperature of the grown crystal. There is a problem that the crystal cannot be obtained. For this reason, even if it uses the method of this patent document 4, it is difficult to heat the raw material of the central part vicinity effectively, and is unsuitable for the enlargement of the ingot which requires a lot of sublimation gas, and lengthening. .

JP 2010-275,190 JP 2007-230,846 JP 2010-138,006 JP 2008-290,903 JP JP 2012-171,832

Yu. M. Tairov and V. F. Tsvetkov, Journal of Crystal Growth, 52 (1981) pp.146

  Therefore, the present inventors have a method for efficiently sublimating the silicon carbide raw material charged in the crucible when manufacturing a large-diameter and long silicon carbide single crystal ingot using high-frequency induction heating. As a result of intensive studies, the thermal distribution inside the silicon carbide raw material is reduced by arranging a heat insulating member that blocks the flow of heat generated from the upper surface of the center of the silicon carbide raw material toward the seed crystal in the crucible. It was found that the raw material can be sublimated at a more uniform temperature, the silicon carbide raw material loaded in the crucible can be sublimated efficiently, and a large-diameter and long silicon carbide single crystal ingot can be produced. completed.

  The present invention provides a silicon carbide single crystal ingot suitable for producing a large-diameter and long silicon carbide single crystal ingot by efficiently sublimating a silicon carbide raw material charged in a crucible during the growth of the silicon carbide single crystal. An object is to provide a manufacturing method.

That is, the gist of the present invention is as follows.
[1] A silicon carbide single crystal is grown by a sublimation recrystallization method in which a sublimation gas generated by heating a silicon carbide raw material charged in a crucible is recrystallized on a silicon carbide seed crystal disposed opposite to the crucible. A method for producing a silicon carbide single crystal ingot, comprising:
The said crucible, characterized in that the graphite heat insulating member that blocks the flow of heat generated toward the seed crystal side from the center upper surface of the silicon carbide raw material, are arranged in contact with the silicon carbide raw material A method for producing a silicon carbide single crystal ingot.
[2] The silicon carbide single crystal according to [1], wherein the heat insulating member is placed on an upper surface of a center portion of the silicon carbide raw material and is in contact with a surface of the silicon carbide raw material. Ingot manufacturing method.
[3] The silicon carbide unit according to [1] or [2], wherein the heat insulating member is formed in an inverted cone shape that decreases from the seed crystal side toward the silicon carbide raw material side. A method for producing a crystal ingot.
[4] The heat insulating member according to any one of [1] to [3], wherein the heat insulating member is housed in a container having a shape similar to the contour shape of the heat insulating member and disposed in a crucible. A method for producing a silicon carbide single crystal ingot.
[5] The method for producing a silicon carbide single crystal ingot according to [4], wherein the container is made of graphite.
[6] The method for producing a silicon carbide single crystal ingot according to any one of [1] to [5], wherein the height of the produced silicon carbide single crystal ingot is 40 mm or more and 200 mm or less.

  By the way, in the induction heating by high frequency using a graphite crucible, the side wall of the crucible which is a heat generating member is easily heated, but the central part of the silicon carbide raw material loaded in this crucible (the part near the central axis of the crucible) Is difficult to be heated, in particular, the bottom part of the raw material is in contact with the bottom part of the crucible, and is the part where the heat input into the raw material flows out from the side wall of the crucible, the temperature is low with respect to the side wall, It is difficult to effectively heat the vicinity of the center of the raw material bottom that is far from the side wall.

  In general, a graphite crucible that generates heat by high-frequency induction heating, a heating member made of a heat generating member made of a crucible constituent member and a silicon carbide raw material made of a heat insulating member, a work coil that generates an induction heating current in the heating member, and the like are provided. When the high frequency induction heating current is increased without changing the arrangement of these facilities in the silicon carbide single crystal ingot manufacturing apparatus, the temperature distribution isotherm pattern does not change greatly, and the absolute value of the temperature. Is known to rise. Therefore, in order to change the shape of the isotherm of the temperature distribution inside the crucible, for example, the shape and structure of the heat generating member and the heat insulating member are changed, or the relative position between the heat generating member, the heat insulating member and the work coil. It is necessary to change the relationship.

  In order to perform crystal growth, it is necessary to form a temperature gradient inside the crucible, increase the temperature of the raw material portion, and relatively decrease the temperature of the crystal portion to be grown. That is, it is necessary to form a heat flow from the raw material to the crystal in the crucible. For this purpose, heat generated by high frequency induction at the crucible side wall is released to the outside of the system through the inside of the raw material and then through the growth crystal. As a result, the temperature of the outer peripheral portion is high inside the raw material, the temperature decreases toward the central portion, and a temperature gradient is generated toward the growing crystal.

  Therefore, in the present invention, the heat flow generated from the upper surface of the center portion of the silicon carbide raw material toward the crystal is blocked by the heat insulating member, and the seed crystal side (the seed crystal or By creating a heating state or heating atmosphere that allows more heat to flow into the silicon single crystal), while maintaining the temperature gradient necessary for crystal growth, the temperature drop at the center of the raw material is suppressed, and the entire raw material The temperature is made more uniform and the raw material is sublimated efficiently.

  That is, in the present invention, a heat insulating member is arranged between the center portion of the silicon carbide raw material and the seed crystal side, the heat flow inside the crucible is controlled, and the temperature distribution inside the raw material is reduced due to the effect. Suppressing recrystallization of silicon carbide sublimation gas in the lower part of the center of the raw material (bottom of the center), and as much as possible to the center of the silicon carbide raw material in the crucible, especially to the bottom of the center It effectively sublimates as a raw material for crystal growth.

  According to the method for producing a silicon carbide single crystal ingot of the present invention, when growing a large-diameter and long silicon carbide single crystal ingot, the temperature and the periphery of the silicon carbide raw material loaded in the crucible It is possible to heat with a small temperature difference between the temperature of the part and effectively sublimate the charged raw material, that is, the crystallization rate of the silicon carbide raw material [= (of the grown silicon carbide single crystal ingot Weight) / (weight of loaded silicon carbide raw material)] can be increased.

  In addition, the sublimated source gas is less recrystallized and consumed near the center of the bottom of the source material, and the sublimation gas is efficiently and stably supplied to the crystal growth surface. The generation of defects due to fluctuations in the supply of sublimation gas can be suppressed, and a high-quality silicon carbide ingot can be produced, and electrons can be produced using this high-quality silicon carbide single crystal ingot. If the silicon carbide single crystal substrate for the material is manufactured, the yield of the substrate manufactured with respect to the silicon carbide raw material is improved, and the cost of the silicon carbide single crystal substrate can be reduced.

FIG. 1 is an explanatory diagram for explaining the principle of the improved Rayleigh method. FIG. 2 is an explanatory view showing the entire manufacturing apparatus for a silicon carbide single crystal ingot used in the embodiment of the method for manufacturing a silicon carbide single crystal ingot according to the present invention.

FIG. 3 is an explanatory diagram showing an outline of the heat insulating member used in Example 1 of the present invention. FIG. 4 is an explanatory diagram illustrating another example of the arrangement of the heat insulating members according to the first embodiment of the present invention.

FIG. 5 is an explanatory view showing an outline of the heat insulating member used in Example 2 of the present invention. FIG. 6 is an explanatory view showing an outline of a heat insulating member used in Example 3 of the present invention.

Hereinafter, an embodiment of a method for manufacturing a silicon carbide single crystal ingot of the present invention will be described using a silicon carbide single crystal ingot manufacturing apparatus shown in the accompanying drawings.
FIG. 2 is for explaining the whole manufacturing apparatus of a silicon carbide single crystal ingot. In this manufacturing apparatus, a double quartz tube 13 covers a crucible 1 made of graphite and surrounding the crucible 1. A graphite heat insulating material 5 is provided, and the crucible 1 is provided with a graphite lid member 1a at the top thereof. Furthermore, a work coil 17 for high-frequency induction heating that heats the crucible 1 functioning as a heat generating member is installed outside the double quartz tube 13.

  The graphite crucible 1 is loaded with a silicon carbide silicon carbide raw material 3 made of silicon carbide crystal powder at the lower portion thereof, and in the upper part of the inside [cover member (graphite crucible lid) 1a]. Is attached with a seed crystal 2 made of a silicon carbide single crystal. In FIG. 2, reference numeral 6 denotes a notch hole, reference numeral 10 denotes a crucible support, reference numeral 14 denotes a vacuum exhaust device, reference numeral 15 denotes an Ar gas pipe, reference numeral 16 denotes an Ar gas mass flow controller, and the work coil 17 A non-illustrated high-frequency power source for supplying a high-frequency current is attached to the.

In this manufacturing apparatus, the inside of the double quartz tube 13 can be evacuated to a high vacuum (10 ⁻³ Pa or less) by the vacuum exhaust device 14, and the Ar gas pipe 15 and the Ar gas mass flow controller 16 are used to The pressure of the atmosphere can be controlled with Ar gas. The temperature of the graphite crucible is measured by providing an optical path at the center of the graphite heat insulating material 5 covering the upper and lower parts of the graphite crucible, and taking out light from the upper part (lid member) and the lower part (bottom part) of the graphite crucible. Then, using a two-color thermometer, the temperature of the lower part (bottom part) of the graphite crucible is used as the raw material temperature, and the temperature of the seed crystal is determined from the temperature of the upper part (lid member) of the graphite crucible.

  In this manufacturing apparatus, the crucible 1 functioning as a heat generating member is heated by high-frequency induction heating by the work coil 17 to heat the silicon carbide raw material 3 and the seed crystal 2 to desired temperatures to sublimate the raw material 3. Crystal growth is performed by recrystallizing the sublimation gas on the silicon carbide single crystal used as the seed crystal 2.

  Here, in the present invention, for example, as shown in FIG. 2 and FIG. 3, the heat flow generated from the center of the silicon carbide raw material 3 toward the seed crystal 2 side is blocked using a heat insulating member 20, By making the heating state such that more heat flows from the part to the seed crystal 2 side, while maintaining the temperature gradient necessary for crystal growth, the temperature drop at the center of the raw material 3 is suppressed, The temperature can be made more uniform and the source gas can be sublimated effectively.

  Here, the shape of the heat insulating member 20 that blocks the flow of heat generated from the center of the silicon carbide raw material 3 toward the seed crystal 2 side is not particularly limited as long as such a flow of heat can be blocked. However, in the production of a normal silicon carbide single crystal ingot, since an axially symmetric crystal is grown using an axially symmetric crucible, the heat insulating member 20 to be disposed preferably has an axially symmetric shape, for example, Starting with a disc shape as shown in FIG. 3, a cylindrical shape, a conical shape, or a combination of these shapes can be exemplified, and the seed crystal 2 side has a planar shape, and the central axis of the crucible It is preferable to arrange on top. However, the effect of the present invention can be obtained even if a non-axisymmetric shape is used.

  Further, the material of the heat insulating member is preferably made of graphite, which is a material that does not become an impurity in the silicon carbide single crystal ingot produced by the method of the present invention and can be used at a temperature of 2000 ° C. or higher. Specifically, for example, a felt-shaped graphite heat insulating member or a molded heat insulating member made of graphite is processed into an appropriate shape and arranged. Moreover, about the thickness of a heat insulation member, it can adjust suitably according to the heat conductivity which a heat insulation member has.

  Furthermore, the arrangement of the heat insulating member 20 that blocks the flow of heat generated from the center of the silicon carbide raw material 3 toward the seed crystal 2 side is not particularly limited as long as such a flow of heat can be blocked. As a specific example, as shown in FIGS. 2 and 3, it is possible to place a heat insulating member on the upper surface of the center portion of the silicon carbide raw material. By disposing the heat insulating member in contact with the surface of the silicon carbide raw material 3 in this way, the shape and structure of the crucible are not particularly complicated when the present invention is implemented. Here, the placement on the upper surface of the silicon carbide raw material 3 includes the case where the heat insulating member 20 is disposed so as to be embedded in the raw material 3 as shown in FIG. Even if the shape and structure of the crucible are devised and a gap is provided between the heat insulating member and the silicon carbide raw material, the temperature inside the raw material can be made uniform. The structure may be complicated, or the silicon carbide sublimation gas may be recrystallized on the surface of the heat insulating member on the silicon carbide raw material side, and measures for that are required.

  The area of the heat insulating member covering the surface of the silicon carbide raw material is usually 30% to 70%, preferably 30% to 60% of the raw material surface. If it exceeds 70%, the temperature of the raw material portion is promoted to be uniform, but the supply path of the raw material gas is reduced, and the supply of gas to the growing crystal may be insufficient. If it is less than 30%, the effect of heat insulation cannot be sufficiently obtained, the temperature inside the raw material is insufficiently uniformed, the temperature at the center of the raw material is lowered, and the effect of efficiently sublimating the raw material cannot be obtained. .

  By the way, when the heat insulating member is placed and disposed on the upper surface of the center portion of the silicon carbide raw material as in the case of FIG. 3 or FIG. 4, the heat insulation is caused by a slight temperature distribution remaining inside the raw material. The sublimation gas may recrystallize on the raw material side surface of the member. Therefore, in order to prevent such recrystallization, for example, as shown in FIG. 5, the shape of the heat insulating member is reduced to a reverse cone shape, preferably an inverted cone shape, which is reduced from the seed crystal side toward the raw material side. In addition, it is preferable that the seed crystal side be a plane opposite to the seed crystal (or the crystal in the growth process). The apex angle at this time is preferably 60 ° or more and 150 ° or less. When the apex angle is larger than 150 °, it is difficult to prevent recrystallization on the surface of the heat insulating member on the raw material side. Although the effect of the present invention can be obtained, the volume of the heat insulating member in the raw material is increased, and the raw material charging efficiency is deteriorated.

  Further, in the sublimation gas atmosphere, the heat insulating member is damaged by the sublimation gas, and the heat insulating performance is likely to change. Therefore, in order to prevent the heat insulating member from being damaged by the sublimation gas, it is effective to coat the surface of the heat insulating member with a material that does not become an impurity of a silicon carbide single crystal, such as graphite or silicon carbide. As a simple method for avoiding contact with the sublimation gas and reducing damage to the heat insulating member, for example, the heat insulating member is housed in a container formed of a material that does not become an impurity of silicon carbide single crystal. Can be illustrated. When graphite is used as the container, the thermal conductivity of the container is higher than that of the heat insulating member. Therefore, in order to reduce heat conduction by the container, the thickness of the container should be 2 mm or more and 5 mm or less. Is preferred. When the thickness is less than 2 mm, the container is greatly damaged by the sublimation gas, and the heat insulating member may be damaged. When the thickness exceeds 5 mm, the heat insulating member can be prevented from being damaged, but it is difficult to obtain the effect of controlling the flow of heat and equalizing the temperature inside the raw material.

  When a silicon carbide single crystal ingot having a growth height of 40 mm or more and 200 mm or less is manufactured by the manufacturing method of the present invention, the silicon carbide raw material charged in the crucible can be used effectively, Since the fluctuation of the crystal growth rate is reduced and a high-quality silicon carbide single crystal can be obtained, a silicon carbide single crystal ingot capable of efficiently producing a silicon carbide single crystal for electronic materials is manufactured at a lower cost. can do.

[Example 1]
In Example 1, 2.6 kg of the raw material 3 made of silicon carbide crystal powder produced by the Atchison method was charged in the lower part of the graphite crucible 1 in the production apparatus shown in FIG. At this time, the height of the raw material 3 (distance between the upper surface of the raw material and the lower surface of the raw material) was 125 mm. On the lid member 1a of the graphite crucible 1, a 4H polytype silicon carbide single crystal wafer having a (0001) face with a diameter of 105 mm was disposed as the seed crystal 2. Further, on the upper surface of the central portion of the raw material 3 in the crucible 1, as shown in FIG. 3, a cylindrical graphite heat insulating member 20 having a height of 20 mm having an area that is 40% of the area of the raw material 3 surface (upper surface). Was placed.

  The graphite crucible 1 thus prepared was placed inside the double quartz tube 13 as described above, and a silicon carbide single crystal was grown in accordance with a conventional method according to the above procedure. That is, after raising the raw material temperature to the target temperature of 2400 ° C., the pressure of Ar in the double quartz tube 13 is reduced to a growth pressure of 1.3 kPa over 30 minutes to start crystal growth and heating. Crystals were allowed to grow for 120 hours.

  As a result, a single crystal ingot having a growth rate of about 0.5 mm / hour, a crystal diameter of about 105 mm, and a height of about 60 mm was obtained. When the residue of the raw material in the graphite crucible was observed, it was found that the raw material was efficiently sublimated even in the vicinity of the center, and the heating temperature for the raw material could be effectively changed during high-frequency induction heating. The raw material near the center could also be heated efficiently. Further, the weight of the obtained single crystal ingot was about 1.7 kg, and the crystallization rate was 65%.

Furthermore, when the obtained silicon carbide single crystal ingot was analyzed by X-ray diffraction and Raman scattering, it was an ingot consisting of a single polytype of 4H, and it was extremely high quality with few crystal defects such as micropipes. It was confirmed.
The silicon carbide single crystal substrate cut out from the ingot is useful as a substrate for manufacturing an electronic device.

[Example 2]
In Example 2, 5.2 kg of raw material 3 made of silicon carbide crystal powder produced by the Atchison method was charged in the lower portion of the graphite crucible 1 in the production apparatus shown in FIG. At this time, the height of the raw material 3 (distance between the upper surface of the raw material and the lower surface of the raw material) was 90 mm. In addition, a 4H polytype silicon carbide single crystal wafer having a (0001) face with a diameter of 155 mm was disposed as a seed crystal 2 on the lid member 1a of the graphite crucible 1. Further, as shown in FIG. 5, the central portion of the raw material 3 in the crucible 1 has an area that is 60% of the area of the raw material surface (upper surface), an apex angle of 90 °, and a height of 80 mm. An inverted conical graphite molded heat insulating member 20 was disposed. At this time, it was arranged so that the position of the bottom surface (plane) of the heat insulating member 20 having an inverted cone shape substantially coincided with the raw material surface.

  The graphite crucible 1 thus prepared was placed inside the double quartz tube 13 as described above, and a silicon carbide single crystal was grown in accordance with a conventional method according to the above procedure. That is, after raising the raw material temperature to the target temperature of 2400 ° C., the pressure of Ar in the double quartz tube 13 is reduced to a growth pressure of 1.3 kPa over 30 minutes to start crystal growth and heating. Crystals were grown continuously for 150 hours.

  As a result, a single crystal ingot having a growth rate of about 0.4 mm / hour, a crystal diameter of about 155 mm, and a height of about 60 mm was obtained. When the residue of the raw material in the graphite crucible was observed, it was found that the raw material was efficiently sublimated even in the vicinity of the center, and the heating temperature for the raw material could be effectively changed during high-frequency induction heating. The raw material near the center could also be heated efficiently. Further, the weight of the obtained single crystal ingot was about 3.6 kg, and the crystallization rate was 70%.

Furthermore, when the obtained silicon carbide single crystal ingot was analyzed by X-ray diffraction and Raman scattering, it was an ingot consisting of a single polytype of 4H, and it was extremely high quality with few crystal defects such as micropipes. It was confirmed.
The silicon carbide single crystal substrate cut out from the ingot is useful as a substrate for manufacturing an electronic device.

Example 3
In Example 3, in the manufacturing apparatus shown in FIG. 2, 8.1 kg of the raw material 3 made of silicon carbide crystal powder produced by the Atchison method was charged into the lower portion of the graphite crucible 1 inside the container. At this time, the height of the raw material 3 (distance between the upper surface of the raw material and the lower surface of the raw material) was 140 mm. In addition, a 4H polytype silicon carbide single crystal wafer having a (0001) face with a diameter of 155 mm was disposed as a seed crystal 2 on the lid member 1a of the graphite crucible 1. Further, as shown in FIG. 6, the central portion of the raw material 3 in the crucible 1 has an area that is 50% of the surface area (upper surface) of the raw material, a 5 mm high cylindrical portion, and an apex angle of 120 °. A graphite felt heat insulating member 20b having a shape combined with an inverted conical portion having a height of 40 mm was placed in a graphite container 21 having a thickness of 3 mm. At this time, the bottom surface (plane) of the container 21 that accommodates the heat insulating member 20b was disposed so that the position was 8 mm higher than the raw material surface.

  The graphite crucible 1 thus prepared was placed inside the double quartz tube 13 as described above, and a silicon carbide single crystal was grown in accordance with a conventional method according to the above procedure. That is, after raising the raw material temperature to the target temperature of 2400 ° C., the pressure of Ar in the double quartz tube 13 is reduced to a growth pressure of 1.3 kPa over 30 minutes to start crystal growth and heating. Crystals were grown for 200 hours continuously.

  As a result, a single crystal ingot having a growth rate of about 0.5 mm / hour, a crystal diameter of about 155 mm, and a height of about 100 mm was obtained. When the residue of the raw material in the graphite crucible was observed, it was found that the raw material was efficiently sublimated even in the vicinity of the center, and the heating temperature for the raw material could be effectively changed during high-frequency induction heating. The raw material near the center could also be heated efficiently. The weight of the obtained single crystal ingot was about 6.1 kg, and the crystallization rate was 75%.

Furthermore, when the obtained silicon carbide single crystal ingot was analyzed by X-ray diffraction and Raman scattering, it was an ingot consisting of a single polytype of 4H, and it was extremely high quality with few crystal defects such as micropipes. It was confirmed.
The silicon carbide single crystal substrate cut out from the ingot is useful as a substrate for manufacturing an electronic device.

[Comparative Example 1]
For comparison with Example 1, crystal growth was performed in the crucible without disposing a heat insulating member between the silicon carbide raw material and the seed crystal.
As a result, an ingot having a crystal diameter of about 105 mm and a height of about 20 mm was obtained. When the residue of the raw material in the graphite crucible was observed, recrystallization of the raw material was observed at the center. Since the raw material in the central part is not effectively heated, it is considered that the raw material gas sublimated in the peripheral part of the raw material is recrystallized in the central part of the raw material without being used for crystal growth. Due to the recrystallization of the sublimation gas at the center of the raw material, the supply of the raw material gas was interrupted during the crystal growth, the growth surface of the grown crystal was sublimated, and the growth surface was carbonized. Therefore, the crystallization rate of the ingot was a low value of 22%.

  Since the obtained silicon carbide single crystal ingot had a low ingot height, there was a problem that the yield when cutting out a substrate for manufacturing an electronic device was low. In addition, there is a problem that the weight of the ingot is small with respect to the loaded raw material, and the raw material cannot be effectively used.

  DESCRIPTION OF SYMBOLS 1 ... Crucible, 1a ... Crucible lid member, 2 ... Seed crystal, 3 ... Silicon carbide raw material, 4 ... Single crystal ingot, 5 ... Thermal insulation, 6 ... Notch hole, 10 ... Crucible support, 13 ... Double quartz Pipes, 14 ... vacuum exhaust device, 15 ... Ar gas piping, 16 ... mass flow controller for Ar gas, 17 ... work coil, 20 ... heat insulation member, 21 ... container.

Claims (6)

A silicon carbide single crystal for growing a silicon carbide single crystal by a sublimation recrystallization method in which a sublimation gas generated by heating a silicon carbide raw material charged in the crucible is recrystallized on a silicon carbide seed crystal disposed opposite to the crucible. A method for producing a crystal ingot, comprising:
The said crucible, characterized in that the graphite heat insulating member that blocks the flow of heat generated toward the seed crystal side from the center upper surface of the silicon carbide raw material, are arranged in contact with the silicon carbide raw material A method for producing a silicon carbide single crystal ingot. 2. The method for producing a silicon carbide single crystal ingot according to claim 1, wherein the heat insulating member is placed on an upper surface of a center portion of the silicon carbide raw material and is in contact with a surface of the silicon carbide raw material. .   3. The silicon carbide single crystal ingot according to claim 1, wherein the heat insulating member is formed in an inverted cone shape that decreases from the seed crystal side toward the silicon carbide raw material side. Method.   The said heat insulation member is accommodated in the container of the shape similar to the outline shape of this heat insulation member, and is arrange | positioned in the crucible, The silicon carbide single crystal ingot in any one of Claims 1-3 characterized by the above-mentioned. Production method.   The method for manufacturing a silicon carbide single crystal ingot according to claim 4, wherein the container is made of graphite.   The method for producing a silicon carbide single crystal ingot according to any one of claims 1 to 5, wherein a height of the produced silicon carbide single crystal ingot is 40 mm or more and 200 mm or less.

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