JP5979740B2 - Silicon carbide single crystal growth apparatus and method - Google Patents

Description

  The present invention relates to an apparatus and method for growing a silicon carbide single crystal by solution growth, and more particularly, a silicon liquid in which carbon contained in a graphite crucible is a main raw material. The present invention relates to an apparatus and method for allowing a silicon carbide single crystal to grow at a high rate by allowing it to dissolve smoothly therein.

Compound semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride are widely studied as next-generation semiconductor materials that have superior characteristics compared to silicon, which is currently the most commonly used semiconductor material. Has been. Among them, particularly, silicon carbide has high mechanical strength, excellent 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 limit of silicon. Compared with the temperature being 200 ° C. or lower, the operation limit temperature is 650 ° C. or lower, which is very high. In addition, all silicon carbides having a crystal structure of 3C silicon carbide, 4H silicon carbide, and 6H silicon carbide have a band gap of 2.5 eV or more, which is twice or more higher than silicon, and therefore for high-power and low-loss converters. Excellent as a semiconductor material. Therefore, in recent years, it has attracted attention as an optical semiconductor such as an LED and a semiconductor material for power conversion.

  Usually, as a growth method of 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 sublimation is performed at a high temperature of 2000 ° C. or higher using silicon carbide (SiC) as a raw material. There is a sublimation method for growing single crystals. In addition, a chemical vapor deposition method using a gas source is used.

  However, the Acheson method is very difficult to obtain a high-purity silicon carbide single crystal, and the chemical vapor deposition method can be grown only on a thin film having a limited thickness. Therefore, research on a sublimation method in which crystals are grown by sublimating silicon carbide at a high temperature has been mainly performed. However, the sublimation method is usually performed at a high temperature of 2200 ° C. or higher, and various defects such as micropipe defects and stacking faults are likely to occur. There is a problem that there is.

  In order to solve such problems of the sublimation method, a liquid phase growth method applying the Czochralski method (crystal pulling method) has been introduced. The Czochralski method is a method of growing a single crystal from a melt. The shape and properties of the crystal are determined by pulling speed (growth speed), rotational speed, temperature gradient, or crystal orientation. A liquid phase growth method for growing a silicon carbide single crystal is usually performed by charging 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. Crystals are grown from the surface of the silicon carbide seed crystals located. However, such a method is inferior in economic efficiency because the crystal growth rate is as low as 50 μm / hr or less.

  In Patent Document 1, in addition to silicon, titanium (Ti) or manganese (Mn) is mixed with silicon (Si) at a predetermined ratio to increase the crystal growth rate.

  Patent Document 2 reports that the crystal growth rate is increased by using iron (Fe) and cobalt (Co) together with silicon (Si) in a predetermined ratio in addition to silicon. In this method, a metal other than silicon is mixed to form an eutectic point, thereby increasing the solubility of carbon in the silicon solution and increasing the speed of the silicon carbide single crystal. However, in the surface area inside the graphite crucible used as the carbon source, there is a limit that the area in contact with the metal melt is still small.

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

JP 2004-2173 A JP 2006-143555 A

  The present invention has been made 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 capable of making a silicon carbide single crystal grow faster. There is.

  In order to achieve the above object, the present invention is provided in a reaction chamber in a constant pressure state, and inside the reaction chamber, in which silicon (Si) or silicon carbide (SiC) powder, or a mixture thereof is provided. A crucible made of graphite, in which a silicon carbide seed crystal on which silicon carbide grows and a seed crystal connecting rod formed extending from the silicon carbide seed crystal are provided on the inner upper part, and the crucible There is provided a silicon carbide single crystal growth apparatus in which a cylindrical auxiliary tool made of graphite including a heating element for heating and having a large number of pores formed on at least side surfaces is provided inside the crucible.

  The cylindrical auxiliary tool preferably has a thickness of 1 mm or more and a hole having a diameter of 2 mm or more. If the thickness is smaller than the above value, it is difficult not only to manufacture the cylindrical auxiliary tool, but also it is difficult for the cylindrical auxiliary tool to crack and maintain its shape during growth. On the other hand, if the hole size is smaller than the above value, the workability is poor and the flow of carbon introduced into the crucible is hindered, which may hinder the growth of the silicon carbide single crystal.

  In the present invention, the silicon carbide seed crystal is provided rotatably with respect to the crucible with the aid of the seed crystal connecting rod. Further, the silicon carbide seed crystal is provided to be movable up and down with respect to the crucible with the aid of a seed crystal connecting rod.

  The present invention may further include a rotation support disposed at a lower portion of the crucible so as to rotate the crucible. The crucible itself disposed inside the reaction chamber can be rotated by the rotating support. As a result, silicon (Si) filled in the crucible and carbon come into contact with each other more quickly, so that the growth rate of the silicon carbide single crystal is increased.

In the present invention, the heating element may be disposed anywhere around the crucible, but is preferably disposed on the outer peripheral surface of the crucible in order to increase the operability of the cylindrical auxiliary tool. As such a heating element, any heating element having a heat generation characteristic or performing a heating operation can be used. Typically, for example, a resistance heating element or an induction heating heating element is used. it can. 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 inside of the reaction chamber is filled with an inert gas such as argon or helium gas, and the pressure in the reaction chamber is maintained at 0.3 to 50 Kgf / cm ² . ^Usually grown in ^{1kgf / cm 2 ~2kgf / cm 2} , higher pressures, the growth rate increases. In order to maintain the atmosphere as described above, for example, a vacuum pump and an atmosphere control gas cylinder can be connected via a valve. Those skilled in the art will be able to recognize 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, a graphite-type airfoil auxiliary device is further provided at a lower portion of the cylindrical auxiliary device to induce a fluid flow in a predetermined direction. This airfoil auxiliary tool selectively orients the fluid flow caused by the rotation of the silicon carbide seed crystal and / or the fluid flow caused by the rotation of the crucible by the rotating support provided at the lower part of the crucible. Play a role. This increases the rate of formation of the silicon carbide single crystal by providing an opportunity for a substance such as carbon to contact the silicon carbide seed crystals faster and more.

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

It is sectional drawing which showed roughly the principal part of the silicon carbide single crystal growth apparatus by the preferable specific example of this invention. FIG. 2 is a schematic perspective view of a cylindrical auxiliary tool made of a porous graphite material shown in FIG. 1. 1 is a view showing a flow of fluid in a crucible provided in a silicon carbide single crystal growth apparatus according to a preferred embodiment of the present invention. It is sectional drawing which showed roughly the principal part of the silicon carbide single crystal growth apparatus by the more preferable specific example of this invention. FIG. 5 is a perspective view of the wing-shaped auxiliary tool made of graphite shown in FIG. 4. 4 is a view showing a flow of fluid induced by a wing-shaped auxiliary tool made of graphite provided in a silicon carbide single crystal growth apparatus according to a more preferred embodiment of the present invention.

  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 may be omitted to clarify the gist of the present invention.

  FIG. 1 is a schematic view showing a main part of a silicon carbide single crystal growth apparatus according to a preferred embodiment of the present invention. FIG. 2 is a schematic view of a cylindrical auxiliary tool made of a porous graphite material shown in FIG. FIG. 3 is a view showing the flow of fluid in the crucible provided in the silicon carbide single crystal growth apparatus shown in FIG.

  1 to 3, a silicon carbide single crystal growth apparatus 1 according to an embodiment of the present invention heats a reaction chamber 10, a crucible 30 provided in the reaction chamber 10, and the crucible 30. And a cylindrical auxiliary tool 70 provided inside the crucible 30.

The reaction chamber 10 is filled with an inert gas such as argon or helium, and the pressure is about 0.3 to 50 kgf / cm ² . In order to maintain this atmosphere, although not shown in the drawings, a vacuum pump and an atmosphere control gas cylinder are connected to the reaction chamber 10 via valves. Those skilled in the art will be able to recognize a variety of other means for maintaining the reaction chamber atmosphere.

  The crucible 30 is provided in the reaction chamber 10 as described above, 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 can be used as a carbon supply source.

  As shown in FIG. 1, a silicon carbide seed crystal 32 on which silicon carbide grows with the aid of a seed crystal connecting rod 34 is provided on the inner upper portion of the crucible 30. The seed crystal connecting rod 34 is provided to be rotatable with respect to the upper end portion of the crucible 30 as necessary. Further, the seed crystal connecting rod 34 is provided so as to be movable up and down with respect to the upper end portion of the crucible 30 as the single crystal grows as necessary. Thereby, the silicon carbide seed crystal 32 is also provided to be rotatable and provided to be movable up and down. Such an arrangement will be apparent to those skilled in the art even if not shown in FIGS.

  A heating element 50 is provided on the outer peripheral surface of the crucible 30 as shown in FIG. As the heating element 50, any heating element can be used. However, in the present invention, a resistance heating element or an induction heating heating element can be preferably used.

  As shown in FIG. 1, a cylindrical auxiliary tool 70 made of graphite is provided inside the crucible 30. A large number of pores 72 are formed on the side surface of the cylindrical auxiliary tool 70 as shown in FIG. This cylindrical auxiliary tool 70 made of graphite is made of silicon carbide by increasing the carbon concentration around the portion where the single crystal is grown by dissolving more carbon in the solution containing silicon. Increase crystal growth rate.

  The cylindrical auxiliary tool 70 itself becomes a carbon supply source. Further, as shown in FIG. 3, the heating of the crucible 30 by the heating element 50, the rotation of the silicon carbide seed crystal 32 as necessary, and / or the rotation of the rotation support 40, which will be described later, is performed. Silicon and additive flows are generated through the pores 72, thereby further increasing the feed rate and feed rate of the carbon source. At this time, the amount of carbon dissolved from the cylindrical auxiliary tool 70 is increased, and the carbon concentration around the crystal growth site of the silicon carbide seed crystal is further increased by the flow as described above. The crystal growth rate is increased.

  A rotating support 40 is provided at the lower part of the crucible 30. The rotary support 40 is rotated as necessary so that the crucible 30 rotates at a predetermined speed. Also by this rotation, the carbon from the crucible 30 and the carbon from the cylindrical auxiliary tool 70 are quickly dissolved in the silicon-containing solution. By this rotation, the carbon concentration around the silicon carbide seed crystal 32 is increased, so that the growth rate of the silicon carbide single crystal is further increased.

  FIG. 4 is a view schematically showing a main part of a silicon carbide single crystal growth apparatus according to a more preferred embodiment of the present invention, and FIG. 5 is a schematic view of an airfoil auxiliary tool made of graphite shown in FIG. FIG. 6 is a view showing a flow of fluid induced by a wing-shaped auxiliary tool made of graphite provided in a silicon carbide single crystal growth apparatus according to a more preferred embodiment of the present invention.

  4 to 6, a silicon carbide single crystal growth apparatus according to a more preferred embodiment of the present invention has a crucible 30 in addition to the configuration of the silicon carbide single crystal growth apparatus 1 according to the above-described preferred embodiment of the present invention. Further, a wing-shaped auxiliary tool 90 made of graphite is formed at the bottom of the wing.

  In the present invention, a wing-shaped assisting device 90 made of graphite belonging to a part of the present invention is provided together with the above-described cylindrical assisting device 70. It will be appreciated that the airfoil aid 90 can be provided alone without the cylindrical aid 70.

  4 to 6, a wing-shaped auxiliary tool 90 made of graphite belonging to a part of the configuration of the present invention is provided on the bottom of the crucible 30 so as to induce a flow of fluid having a predetermined orientation. The airfoil aid 90 may be provided alone or with the cylindrical aid 70 described above. If the airfoil aid 90 is provided with the cylindrical aid 70 described above, the airfoil aid 90 is provided at the lower end within the cylindrical aid 70 or a predetermined distance from the cylindrical aid 70. It can be provided separately in a separated state. When the airfoil aid 90 is separately provided with a predetermined distance from the cylindrical aid 70, the cylindrical aid 70 is separated from the bottom surface, inner peripheral surface, or upper inner surface of the crucible 30. It must be fixed spatially by means, or spatially spaced by another means from the airfoil aid 90.

  The airfoil aid 90 is configured to allow fluid to flow in one direction, particularly as illustrated in FIG. Further, since the airfoil auxiliary tool 90 is made of a graphite material, the airfoil auxiliary tool 90 itself is used as a carbon supply source. When a rotational flow is generated by the rotation of the silicon carbide seed crystal 32 and / or the rotary support 40, the airfoil auxiliary tool 90 that guides the flow in one direction as described above further increases the rotational flow, and silicon carbide. The carbon concentration around the seed crystal 32 is increased. Even when the rotational flow due to the rotation of the silicon carbide seed crystal 32 and / or the rotary support 40 is not generated, the airfoil auxiliary tool 90 allows the fluid flow generated by the heating of the crucible 30 by the heating element 40 to flow in one direction. Therefore, the carbon concentration around the silicon carbide seed crystal 32 is increased. Thereby, the carbon concentration in the periphery of the site where the silicon carbide single crystal is grown increases. In the present invention, only the structure having two wings is shown as the airfoil auxiliary tool 90, but the number and form of the wings are not limited to the number and structure shown in FIGS. .

  Although the present invention has been described with reference to the preferred specific examples, those skilled in the art will be within the spirit and scope of the present invention described in the appended claims. It will be understood that the present invention can be modified and changed in various ways.

DESCRIPTION OF SYMBOLS 10 Reaction chamber 30 Crucible (of graphite material) 32 Silicon carbide seed crystal 34 Seed crystal connecting rod 50 Heat generating element 70 Cylindrical auxiliary tool (of graphite material) 72 Pore 90 Airfoil auxiliary tool

Claims (8)

A reaction chamber at a constant pressure,
A silicon carbide seed crystal that is provided inside the reaction chamber, is charged with silicon (Si) or silicon carbide (SiC) powder, or a mixture thereof; A crucible of graphite material provided with a seed crystal connecting rod formed extending from a silicon carbide seed crystal;
A heating element for heating the crucible,
The temperature gradient inside the crucible by the heating element is 5 ° C./cm or more in the vertical direction,
The crucible is further provided with a cylindrical auxiliary tool made of graphite that is separable from the crucible, and the cylindrical auxiliary tool has a large number of pores formed in the circumferential direction on the side surface from the lower part to the upper part. A silicon carbide single crystal growth apparatus, which is formed at a predetermined interval .   2. The silicon carbide single crystal growth apparatus according to claim 1, further comprising a wing-shaped auxiliary tool made of graphite for inducing a fluid flow in a predetermined direction at a lower portion of the cylindrical auxiliary tool.   The silicon carbide single crystal growth apparatus according to claim 2, wherein the cylindrical auxiliary tool has a thickness of 1 mm or more and a hole having a diameter of 2 mm or more.   3. The silicon carbide single crystal growth apparatus according to claim 1, wherein the silicon carbide seed crystal is provided to be rotatable with respect to the crucible with the aid of the seed crystal connecting rod. 4.   3. The silicon carbide single crystal growth apparatus according to claim 1, further comprising a rotating support disposed at a lower portion of the crucible so as to rotate the crucible.   The silicon carbide single crystal growth apparatus according to claim 1, wherein the heating element is disposed 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. The inside of the reaction chamber is filled with argon or helium gas, and the internal pressure of the reaction chamber is 0.3 to 50 kgf / cm ^2. Crystal growth equipment.

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