JP2014518194A - Silicon carbide single crystal growth apparatus and method - Google Patents

Abstract

The present invention relates to an apparatus and a method for growing a silicon carbide single crystal by solution growth. A silicon carbide single crystal growth apparatus according to the present invention is provided in a reaction chamber in a predetermined pressure state, and inside the reaction chamber, in which silicon (Si) or silicon carbide (SiC) powder or a mixture thereof is loaded. And a graphite crucible having a silicon carbide seed crystal in which silicon carbide grows on the inner upper side rf and a seed crystal connecting rod formed extending from the silicon carbide seed crystal, and a heating element for heating the crucible And including. Inside the crucible, at least one or more projecting step portions made of a graphite material, which are formed at least partially or entirely along the inner peripheral surface of the crucible, are provided.
[Selection] Figure 1

Description

  The present invention relates to an apparatus and a method for growing a silicon carbide single crystal by solution growth, so that carbon contained in a graphite crucible is smoothly dissolved in a silicon liquid phase as a main material. Thus, the present invention relates to an apparatus and method for rapidly growing a silicon carbide single crystal.

Currently, compound semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride have been widely studied as materials for next-generation semiconductors that have characteristics superior to silicon, which is currently the most widely used semiconductor material. ing. Among them, silicon carbide is not only excellent in mechanical strength but also excellent in thermal stability and chemical stability, and not only has a very high thermal conductivity of 4 W / cm ² or more, but also has an operating temperature limit. It is very high at 650 ° C. or lower compared with that of silicon at 200 ° C. or lower. Further, when the crystal structure is 3C silicon carbide, 4H silicon carbide, or 6H silicon carbide, the band gaps are all 2.5 eV or more, which is twice or more that of silicon. In recent years, it has attracted attention as a material for optical semiconductors such as LEDs and semiconductors for power conversion.

  Usually, in order to grow a silicon carbide single crystal, for example, an Acheson method in which carbon and silica are reacted in a high-temperature electric furnace of 2000 ° C. or higher, and silicon carbide (SiC) as a raw material at a high temperature of 2000 ° C. or higher. A sublimation method in which a single crystal is grown by sublimation is used. In addition, a chemical vapor deposition method using a gas source is used.

  However, it is very difficult to obtain a high-purity silicon carbide single crystal by the Acheson method, and the chemical vapor deposition method can be grown to a limited thickness only as a thin film. . Therefore, research on a sublimation method in which silicon carbide is sublimated at a high temperature to grow a crystal has been concentrated. However, the sublimation method is also usually performed at a high temperature of 2200 ° C. or more, and many defects such as micro defects and stacking faults are likely to occur, and there is a limit in terms of production cost. I have a problem.

  In order to solve the problem of the sublimation method, a liquid phase growth method using the Czochralski method (crystal pulling method) has been introduced. The Czochralski method is a method for growing a single crystal from a melt. The shape and properties of the crystal are determined according to the pulling rate (growth rate), rotational speed, temperature gradient, or crystal orientation. The liquid phase growth method for silicon carbide single crystal is usually performed by placing silicon or silicon carbide powder in a graphite crucible and then raising the temperature to a high temperature of about 1600 ° C. to 1900 ° C. The crystal is grown from the surface of the silicon carbide seed crystal. However, such a method is inferior in economic efficiency because the crystal growth rate is very slow at 50 μm / hr or less.

  In Japanese Unexamined Patent Application Publication No. 2004-2173, titanium (Ti) or manganese (Mn) is mixed with silicon (Si) at a predetermined ratio in addition to silicon to increase the crystal growth rate.

  Japanese Patent Application Laid-Open No. 2006-143555 discloses that, in addition to silicon, iron (Fe) and cobalt (Co) are used together with silicon (Si) at a predetermined ratio to increase the crystal growth rate. It is disclosed. Such a method has the effect of increasing the carbon solubility in the silicon solution by mixing a metal other than silicon to form an eutectic point, thereby increasing the speed of the silicon carbide single crystal. However, there is still a limit that the area in contact with the metal melt is small in the internal surface area of the graphite crucible used as the carbon source.

  In the case of a liquid phase growth method for growing a silicon carbide single crystal, graphite for the crystal growth is usually a graphite crucible. That is, the carbon atoms constituting the graphite crucible are separated into a liquid phase, and thereafter, after spreading into the solution, a part thereof moves to the growth point of the silicon carbide single crystal to grow a single crystal. However, there is a difference between the carbon concentration around the crucible to which carbon atoms are supplied and the carbon concentration around single crystal growth where carbon atoms are synthesized into silicon carbide and disappear. Therefore, it is necessary to actually increase the carbon concentration around the single crystal growth by making the carbon concentration in the solution in the crucible uniform in a closed growth furnace operated at a high temperature. For this purpose, as in the method used in the Czochralski method, the seed crystal fixing rod on which the seed crystal is fixed is rotated and / or the crucible is rotated to increase the uniformity of the carbon concentration in the solution. Increase.

  The present invention has been derived in order to improve the limitations of the prior art, and an object of the present invention is to provide a silicon carbide growth apparatus and method that can more rapidly grow a silicon carbide single crystal. It is in.

  In order to achieve the above and other objects, the present invention provides a reaction chamber in a predetermined pressure state, a silicon (Si) or silicon carbide (SiC) powder or a mixture thereof provided in the reaction chamber. And a graphite crucible having a silicon carbide seed crystal in which silicon carbide grows on the inner upper part and a seed crystal connecting rod formed extending from the silicon carbide seed crystal, and heat generated to heat the crucible A silicon carbide unit provided with at least one or more graphite protruding step portions formed along the inner peripheral surface of the crucible at least partially or entirely inside the crucible. A crystal growth apparatus is provided.

  In the present invention, it is preferable that a part or all of the protruding stepped portion is formed into a structure that does not hinder the flow of the silicon solution charged into the crucible, and in particular has a donut shape, for example. It is preferable.

  In the present invention, the silicon carbide seed crystal may be provided so as to be rotatable with respect to the crucible by the seed crystal connecting rod. In addition, such a silicon carbide seed crystal is provided so as to be movable up and down with respect to the crucible by a seed crystal connecting rod. With such a structure capable of rotating and vertically moving the silicon carbide seed crystal, the temperature distribution inside the crucible can be easily controlled.

  In the present invention, it is preferable that a rotation support provided to rotate the crucible is further included below the crucible. Such a rotating support allows rotation of the crucible itself disposed inside the reaction chamber, thereby providing an opportunity for more rapid contact between silicon (Si) and carbon filled in the crucible. As a result, the growth rate of the silicon carbide single crystal is increased.

In the present invention, the heating element may be disposed at any position around the crucible, and along the outer peripheral surface of the crucible for a smoother flow through the protruding step provided inside the crucible. Preferably they are arranged. As such a heating element, any heating element having a heating characteristic or a heating operation is possible, but typically, for example, a resistance heating element or an induction heating heating element may be used. The temperature gradient inside the crucible by the heating element is preferably 5 ° C./cm ² or more in the vertical direction.

In the present invention, the reaction chamber is filled with an inert gas such as argon or helium gas, and the pressure inside the reaction chamber is maintained at 0.3 to 50 kgf / cm ² . In order to maintain such a pressure, for example, a vacuum pump and an atmosphere control gas cylinder may be connected via a valve. Those skilled in the art will be aware of various other means by which the interior of the reaction chamber can be maintained in a vacuum.

  In a more preferred embodiment of the present invention, it may further include a wing-shaped auxiliary tool made of graphite provided on the bottom surface inside the crucible for inducing a fluid flow in a predetermined direction. Such a wing-like auxiliary tool selectively selects the flow of fluid accompanying rotation of the silicon carbide seed crystal and / or the flow of fluid accompanying rotation of the crucible by the rotating support provided at the lower part of the crucible in one direction. By performing the function of orienting, a material such as carbon is given an opportunity to contact the silicon carbide seed crystal more quickly and frequently, thereby increasing the formation rate of the silicon carbide single crystal.

  According to the present invention, the carbon concentration around the silicon carbide seed crystal is increased, thereby increasing the growth rate of the silicon carbide single crystal.

It is sectional drawing which shows roughly the principal part of the growth apparatus of the silicon carbide single crystal by one preferable example of this invention. FIG. 2 is a partial cutaway perspective view showing a part of the internal shape of the graphite crucible shown in FIG. 1. It is sectional drawing which shows roughly the principal part of the growth apparatus of the silicon carbide single crystal by the more preferable example of this invention. FIG. 4 is a partial cutaway perspective view schematically showing a part of the shape of a graphite crucible provided with the wing-like auxiliary tool shown in FIG. 3.

  Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. However, in describing the present invention, descriptions of functions or configurations already known are omitted for the purpose of clarifying the gist of the present invention.

  FIG. 1 schematically shows an essential part of a silicon carbide single crystal growth apparatus according to one preferred embodiment of the present invention, and FIG. 2 shows a partially cut-out portion of the shape of a graphite crucible. And is shown schematically.

  1 and 2, a silicon carbide single crystal growth apparatus 1 according to one preferred embodiment of the present invention includes a reaction chamber 10, a crucible 30 provided in the reaction chamber 10, and a crucible 30. And heating element 50 for heating. As shown in FIGS. 1 and 2, at least one or more projecting step portions 38 made of a graphite material formed at least partially or entirely along the inner peripheral surface of the crucible 30 are provided inside the crucible 30. Provided.

After maintaining the reaction chamber 10 in a vacuum state, the reaction chamber 10 is filled with an inert gas such as argon or helium, and the pressure is adjusted to a level of 0.3 to 50 kgf / cm ² . In order to maintain such an atmosphere, although not shown in the figure, a vacuum pump and an atmosphere control gas cylinder are connected to the reaction chamber 10 via a valve. Those skilled in the art will be aware of various other means for maintaining the reaction chamber atmosphere.

  As described above, the crucible 30 is provided inside the reaction chamber 10, and silicon (Si) or silicon carbide (SiC) powder or a mixture thereof is charged into the crucible 30. The crucible 30 is made of a graphite material, and the crucible 30 itself may be used as a carbon supply source.

  As shown in FIG. 1, a silicon carbide seed crystal 32 on which silicon carbide grows by a seed crystal connecting rod 34 is provided on the inner upper portion of the crucible 30. The seed crystal connecting rod 34 is rotatably provided with respect to the upper end portion of the crucible 30 as necessary. Further, the seed crystal connecting rod 34 is provided to be movable up and down with respect to the upper end portion of the crucible 30. Thereby, the silicon carbide seed crystal 32 is also provided rotatably, and is provided so as to move up and down when necessary as the single crystal grows. Such a configuration is not shown in the figure, but will be obvious to those skilled in the art who are familiar with the present specification.

  As shown in FIG. 1, a heating element 50 is provided on the outer peripheral surface side of the crucible 30. As the heating element 50, any heating element having heat generation characteristics may be used. In the present invention, a resistance heating element or an induction heating heating element is preferably used.

  Inside the crucible 30 is provided at least one or more graphite-made protruding step portions 38 formed at least partially or entirely along the inner peripheral surface of the crucible 30. A number of protrusions or pores may be formed in the projecting step portion 38 made of the graphite material in order to provide more opportunities for contact with the silicon-containing liquid filled in the crucible 30. Such protrusion structure and pore structure are also included in the configuration of the present invention. By such a protruding step portion 38, the growth rate of the silicon carbide single crystal is increased by increasing the carbon concentration in the vicinity where more carbon is dissolved and the single crystal grows in the silicon-containing solution.

  The protruding step 38 is a carbon supply source and is generated by heating the crucible 30 by the heating element 50 and, if necessary, rotation of the silicon carbide seed crystal 32 and / or rotation of the rotary support 40 described later. Increasing the contact surface due to inductive or forced contact of silicon and additive increases the amount of carbon source and increases the supply and rate of the carbon source. At this time, the amount of carbon dissolved from the protruding step portion 38 increases with the inner surface of the crucible 30, and the carbon concentration around the crystal growth site of the silicon carbide seed crystal 32 is further increased by the spiral flow. This results in increasing the growth rate of the silicon single crystal.

  A rotation support body 40 is provided at the lower part of the crucible 30. Such a rotating support 40 rotates when necessary to rotate the crucible 30 at a predetermined speed. Also by such rotation, carbon from the crucible 30 and carbon from the protruding step portion 38 formed inside the crucible 30 are rapidly dissolved in the silicon-containing solution, and by such rotation, around the silicon carbide seed crystal 32 The carbon concentration increases, and the growth rate of the silicon carbide single crystal is further increased.

  FIG. 3 schematically shows a main part of a silicon carbide single crystal growth apparatus according to a more preferred embodiment of the present invention, and FIG. 4 shows a flow of fluid induced through a wing-like auxiliary tool made of graphite. In addition, the internal shape of the crucible is schematically shown.

  3 and 4, a silicon carbide single crystal growth apparatus according to a more preferred embodiment of the present invention includes a wing-like auxiliary tool 90 made of graphite provided at the bottom of crucible 30 in addition to the above-described embodiment. In addition.

  In the present invention, the wing-like auxiliary tool 90 made of graphite belonging to a part of the configuration of the present invention is provided together with the above-described protruding step portion 38. It will be appreciated that the wing-like assisting tool 90 made of graphite may be provided alone without the protruding step 38 formed along the inner peripheral surface.

  3 and 4, the wing-like auxiliary tool 90 made of graphite belonging to a part of the configuration of the present invention is provided at the bottom of the crucible 30 in order to induce a flow of fluid having a predetermined orientation. The wing-shaped auxiliary tool 90 may be provided alone, or may be provided together with the protruding step portion 38 described above. When the wing-shaped auxiliary tool 90 is provided together with the protruding step portion 38 described above, it is provided alongside the protruding step portion 38 or separately from the protruding step portion 38 provided at the lowermost end by a predetermined distance. May be.

  The wing-shaped auxiliary tool 90 is configured to allow fluid to flow in one direction, particularly as shown in FIG. Further, since the wing-shaped auxiliary tool 90 is made of a graphite material, it itself is used as a carbon supply source. The wing-like auxiliary tool 90 capable of guiding the flow in one direction increases the flow when heating by the heating element 50, rotation of the silicon carbide seed crystal 32 and / or rotation support 40 is generated, and increases the silicon carbide species. The carbon concentration around the crystal 32 is increased. Even when there is no rotating flow by the silicon carbide seed crystal 32 and / or the rotating support 40, the flow of the fluid generated by heating the crucible 30 by the heating element 40 is guided in one direction, so that The carbon concentration in the vicinity where the silicon carbide single crystal grows can finally be increased by increasing the carbon concentration. In the present invention, only the structure of two wings is shown as the wing-shaped auxiliary tool 90, but the number and shape of the wings are not limited to the number and structure shown in FIGS.

  The present invention has been described above with reference to the preferred specific examples. However, those skilled in the art will appreciate that the scope of the present invention described in the following claims does not depart from the spirit and scope of the present invention. It can be understood that various modifications and changes can be made to the present invention.

DESCRIPTION OF SYMBOLS 10 Reaction chamber 30 Crucible (of graphite material) 32 Silicon carbide seed crystal 34 Seed crystal connecting rod 38 Projection step part 50 Heating element 90 Wing-like auxiliary tool

Claims (9)

A reaction chamber in a predetermined pressure state;
A silicon carbide seed crystal that is provided inside the reaction chamber, in which silicon (Si) or silicon carbide (SiC) powder or a mixture thereof is charged, and silicon carbide grows on an inner upper part; and the silicon carbide seed crystal A graphite crucible having a seed crystal connecting rod formed by extension;
A heating element for heating the crucible,
An apparatus for growing a silicon carbide single crystal, wherein the crucible is provided with at least one or more projecting step portions made of graphite formed at least partially or entirely along the inner peripheral surface of the crucible.   The apparatus for growing a silicon carbide single crystal according to claim 1, further comprising a wing-like auxiliary tool made of graphite provided at a lower portion of the protruding step portion for inducing a fluid flow in a predetermined direction.   3. The silicon carbide single crystal growth apparatus according to claim 2, wherein at least a part of the protruding step portion has a donut shape.   3. The silicon carbide single crystal growth apparatus according to claim 1, wherein the silicon carbide seed crystal is provided so as to be rotatable with respect to the crucible by the seed crystal connecting rod.   The silicon carbide single crystal growth apparatus according to claim 1, further comprising a rotation support disposed at a lower portion of the crucible and provided to rotate the crucible.   The silicon carbide single crystal growth apparatus according to claim 1, wherein the heating element is arranged on an outer peripheral surface of the crucible.   The silicon carbide single crystal growth apparatus according to claim 6, wherein the heating element is a resistance heating element or an induction heating heating element. 3. The silicon carbide single crystal growth apparatus according to claim 1, wherein a temperature gradient inside the crucible by the heating element is 5 ° C./cm ² or more in the vertical direction. The carbonization according to claim 1 or 2, wherein the inside of the reaction chamber is filled with argon or helium gas, and the degree of vacuum inside the reaction chamber is 0.3 to 50 kgf / cm ^2. Silicon single crystal growth equipment.

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