JP5580764B2 - SiC single crystal manufacturing equipment - Google Patents

Description

  The present invention relates to an SiC single crystal manufacturing apparatus, and more particularly to an SiC single crystal manufacturing apparatus that can soak the inside of a growth furnace and suppress generation of SiC polycrystals in the vicinity of a seed crystal.

  SiC single crystal is very stable thermally and chemically, excellent in mechanical strength, resistant to radiation, and excellent in breakdown voltage and high thermal conductivity compared to Si (silicon) single crystal. It has physical properties and can easily control p- and n-conductivity type electrons by adding impurities, and has a wide forbidden band width (about 3.3 eV for 4H type single crystal SiC and about 3.3 eV for 6H type single crystal SiC). 0 eV). For this reason, it is possible to realize high temperature, high frequency, withstand voltage and environmental resistance that cannot be realized with existing semiconductor materials such as Si single crystal and GaAs (gallium arsenide) single crystal. It is growing.

  Conventionally, the solution method is known as one of the growth methods of SiC single crystal. This solution method is basically composed of a crucible containing a solvent, for example, a graphite crucible, a solvent, an external heating device such as a high frequency coil, a heat insulating material, a carbon rod for supporting a substrate that can be raised and lowered, and a seed crystal substrate attached to the tip of the carbon rod. C (carbon) supply source in a Si-containing solution such as a Si melt or a Si compound liquid (also referred to as a solution) obtained by melting a metal in a crucible using an apparatus for producing a SiC single crystal having a mechanical structure, for example, In this method, C is melted from a graphite crucible, and, for example, a SiC single crystal is grown from a raw material solution by precipitation on a SiC seed crystal substrate placed in a low temperature portion.

With this solution method SiC single crystal production device, single crystals with good crystal form can be obtained, but the solution is grown with a temperature gradient so that the solution temperature in the vicinity of the seed crystal is lower than the solution temperature of other parts. The SiC single crystal growth method, which is a method of slow cooling the whole solution or a method of growing the whole solution, is used. In either case, the formation of polycrystals is caused by the temperature distribution and concentration distribution in the solution at the time of cooling the solution. It is known that it cannot be avoided.
This problem of polycrystal formation also exists in the growth method of SiC single crystal by the sublimation method.
On the other hand, the necessity to prevent or suppress the formation of polycrystals is a problem to be solved in the production of a semiconductor single crystal such as a compound semiconductor, and various studies have been made.

  For example, in Patent Document 1, a single crystal is grown by heating with a heater provided in a high-pressure vessel to melt a raw material and a sealant, and bringing a seed crystal into contact with the solution surface and pulling it up while rotating. In the apparatus, there is provided a single crystal manufacturing apparatus such as GaAs in which at least the inner surface of the ceiling portion of the high-pressure vessel is coated with a material having a radiation rate higher than 0.4, such as graphite, in order to increase the heat absorption capacity above the pulled crystal. Have been described.

  Patent Document 2 discloses that an upper part of a crucible, an intermediate part of a crucible, and a bottom part of a crucible for sublimating SiC powder by high-frequency heating to grow a SiC single crystal as a seed crystal are 2200 ° C. or lower and 2400-2800, respectively. A manufacturing apparatus is described in which a coil is heated by a current induced by a high-frequency magnetic flux from a high-frequency heating coil that can be set to different temperatures of 0 ° C. and a sublimation temperature of SiC or higher and 2400 ° C.

  Patent Document 3 discloses a single crystal provided with a crucible, a heating means such as a heating coil for heating the entire crucible, and a shield member that covers a part of a lid constituting the crucible and generates heat by the heating means. A manufacturing apparatus is described. As a specific example, an apparatus for producing a single crystal by a sublimation method in which a shield member is provided on a part of the outside of a heat insulating material is shown.

  Furthermore, Patent Document 4 describes an apparatus for producing a silicon carbide single crystal by a sublimation method. As a specific example, a first induction heating coil disposed at a height corresponding to the bottom of the reaction vessel body, and a seed crystal A silicon carbide single crystal manufacturing apparatus including a second induction heating coil disposed at a corresponding height position and an interference preventing coil provided between the two coils is shown.

JP-A-8-73295 JP-A-10-101495 JP 2009-274931 A JP 2010-132517 A

However, in these known single crystal production apparatuses, a high-frequency heating coil is provided to directly heat the inside of the growth furnace, and these techniques are applied to an SiC single crystal production apparatus, particularly a SiC single crystal produced by a solution method. When applied to a manufacturing apparatus, it is inevitable that the temperature in the solution becomes uneven, and it is difficult to prevent or suppress the formation of polycrystals due to partial supercooling.
Accordingly, an object of the present invention is to provide a SiC single crystal manufacturing apparatus, in particular a SiC single crystal manufacturing apparatus by a solution method, which can soak the inside of the growth furnace and suppress the generation of SiC polycrystals in the vicinity of the seed crystal. Is to provide.

The present invention provides a seed crystal for growing a SiC single crystal on a SiC seed crystal substrate from a raw material solution heated to a solution temperature of 1800 to 2100 ° C. by a solution method in a growth furnace, and supports the seed crystal. It is output from the support shaft for transferring heat from the crystal to the outside, the crucible containing the raw material solution , the heat insulating material for preventing heat dissipation from the crucible, and the energy emitter that can release multiple energy provided outside the furnace. A heat generating member is provided inside the heat insulating material to generate heat by the generated energy and heat the inside of the growth furnace, the growth furnace has a space at least above the crucible, and the heat generating member is disposed inside the heat insulating material. The present invention relates to a SiC single crystal production apparatus provided on the entire surface surrounding the crucible and the space .

  ADVANTAGE OF THE INVENTION According to this invention, the inside of a growth furnace can be soaked, and the SiC single crystal manufacturing apparatus by the solution method which can suppress generation | occurrence | production of the SiC polycrystal in the seed crystal vicinity can be obtained.

FIG. 1 is a schematic view of an apparatus for producing an SiC single crystal by a solution method according to an embodiment of the present invention. FIG. 2 is a schematic view of a conventional SiC single crystal manufacturing apparatus using a solution method. FIG. 3 is a schematic view showing a state in which the temperature distribution in the crucible is measured under the condition of no solution using the SiC single crystal growth apparatus according to the embodiment of the present invention. FIG. 4 is a graph showing the temperature distribution in the crucible measured using the SiC single crystal growth apparatus according to the embodiment of the present invention under the condition of no solution. FIG. 5 is a schematic diagram showing a state in which the temperature distribution in the crucible is measured under conditions with a solution using the SiC single crystal growth apparatus according to the embodiment of the present invention. FIG. 6 is a graph showing the temperature distribution in the depth direction in the crucible measured under conditions with a solution using an embodiment of the present invention or a conventional SiC single crystal growth apparatus. FIG. 7 is a graph showing the temperature distribution in the depth direction in the crucible measured using the SiC single crystal growth apparatus according to the embodiment of the present invention and changing the output of the high-frequency coil under conditions with a solution. FIG. 8 is a copy of a SiC single crystal growth photograph in the vicinity of the seed crystal obtained using the SiC single crystal production apparatus according to the solution method of the embodiment of the present invention. FIG. 9 is a copy of a SiC single crystal growth photograph in the vicinity of a seed crystal obtained using a conventional SiC single crystal production apparatus by a solution method.

In particular, in the present invention, the following embodiments can be mentioned.
1) The SiC single crystal manufacturing apparatus, wherein the growth furnace has a space at least above the crucible, and the heating member is provided on the entire surface surrounding the crucible and the space inside the heat insulating material.
2) The SiC single crystal manufacturing apparatus, wherein the heat generating member is made of graphite.
3) The SiC single crystal manufacturing apparatus, wherein the energy emitter is a high-frequency coil.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1, an SiC single crystal growth apparatus 1 according to an embodiment of the present invention includes a seed crystal 4 for growing an SiC single crystal on a SiC seed crystal substrate from a raw material solution 3 in a growth furnace 2 by a solution method. A support shaft 5 for supporting the crystal and transferring heat from the seed crystal to the outside, a crucible 6 for containing the raw material solution, a heat insulating material 7 for preventing heat dissipation from the crucible 6, and a plurality of different energies provided outside the furnace A heat generating member 9 is provided inside the heat insulating material 7 in order to generate heat by the energy output from the energy emitting body 8 that can release the heat and heat the inside of the growth furnace 2.

According to the SiC single crystal growth apparatus of the embodiment of the present invention, by having an indirect heating structure with a heating member that receives the energy output from the energy emitter, the temperature at each position can be set as shown in FIG. The temperature difference ΔT in the depth direction (vertical direction) in the crucible in the absence of the solution obtained by changing the position of the thermocouple is 1.90 ° C./cm, and the temperature in the solution surface direction (horizontal direction) The difference ΔT can be 1.22 ° C./cm, and as shown in FIG. 6, the temperature difference in the depth direction (vertical direction) when the solution is present is the sum of the space in the solution in the crucible and on the solution. It is possible to obtain an almost uniform temperature distribution within about 10 ° C. with almost no.
Thereby, according to the solution method SiC single crystal manufacturing apparatus of the embodiment of the present invention, as shown in FIG.

  On the other hand, the conventional SiC single crystal growth apparatus 10 has a seed crystal for growing a SiC single crystal on a SiC seed crystal substrate from a raw material solution 3 by a solution method in a growth furnace 2 as shown in FIG. 4. A support shaft 5 for supporting the seed crystal and transferring heat from the seed crystal to the outside, a crucible 6 for containing the raw material solution 3, a heat insulating material 7 for preventing heat radiation from the crucible 6, and optionally a crucible A heat generating member (not shown) is provided outside the heat insulating material 7 for covering the part and generating heat by the energy emitting body, and an energy emitting body 8 for heating the inside of the growth furnace outside the furnace.

For this reason, according to the conventional solution method SiC single crystal manufacturing apparatus, even if the crucible covers a part of the crucible and has a heat generating member that generates heat by the energy emitter, heat escape occurs between the upper surface and the lower surface, Generation of temperature distribution (temperature gradient) is unavoidable, and as shown in FIG. 6, a large temperature difference of about 200 ° C. occurs in the depth direction (vertical direction) in the solution in the crucible and on the solution. obtain. Similarly, a carbon (C) concentration distribution in the solution in the crucible is generated.
For this reason, according to the conventional solution method manufacturing apparatus, as shown in FIG. 9, polycrystals adhere to the seed crystal.

In the SiC single crystal growth apparatus of the present invention, the seed crystal may be any SiC single crystal, for example, 4H—SiC, 6H—SiC, 3C—SiC, or the like.
In the SiC single crystal growth apparatus according to the embodiment of the present invention, the crucible is usually made of carbon, and carbon (C) can be eluted into the raw material solution to be a carbon source for SiC. And this crucible may consist of a single component, but as shown in FIG. 3, it may consist of an intermediate crucible and an outer crucible.

Further, in the SiC single crystal growth apparatus of the present invention, the support shaft may be a carbon rod because heat resistance is required, and a cooling mechanism such as a gas cooling mechanism is provided outside the furnace in order to transfer heat from the seed crystal to the outside. Alternatively, a water cooling mechanism may be provided.
In the SiC single crystal growth apparatus of the embodiment of the present invention, examples of the energy emitter that can emit a plurality of different energies include a high-frequency coil that emits high-frequency energy. In the SiC single crystal growth apparatus of the present invention, the heat generating member can be made of, for example, graphite, and what is usually called a susceptor can be used.

In the SiC single crystal growth apparatus of the present invention, the above-described constituent members are essential requirements. However, in addition to the constituent members, the growth furnace 2 is placed at least above the crucible 6 as shown in FIG. The heat generating member 9 may be provided on the entire surface surrounding the crucible 6 and the space 11 inside the heat insulating material 7.
In the SiC single crystal growth apparatus according to the embodiment of the present invention, the heat generating member may be integrated, and the vertical length may be 1.5 times or more, particularly 2 times or more of the length of the crucible, The entire space in the furnace can be heated uniformly.

In the SiC single crystal growth apparatus according to the embodiment of the present invention, a plurality of energy emitters capable of releasing a plurality of different energies are usually provided outside the furnace.
If the SiC single crystal manufacturing apparatus according to the embodiment of the present invention is used, by changing the energy output ratio of at least two high-frequency coils, for example, the current ratio, the depth in the solution in the crucible as shown in FIG. It is possible to provide a temperature distribution in the vertical direction within a narrow range, and it is easy to cause convection in the solution, and it is possible to achieve a uniform carbon (C) concentration, and to change the SiC single crystal growth over time. Can be suppressed.

Examples of the raw material solution in the embodiment of the present invention include any solution containing Si and C as essential components. For example, a Si-containing solution further containing Ti and / or Cr, for example, a Si-Ti-C solution or a material containing Ni and Cr, and elements other than the Si, Cr, Ni and C and rare earth elements, Examples include those containing any one element selected from a transition metal element and an alkaline earth metal element, for example, those in which the element is Ce. Moreover, arbitrary dopants can be contained for semiconductor materials.
The temperature of the raw material solution may be about 1800 to 2100 ° C, particularly about 1850 to 2050 ° C.

  The temperature control by the SiC single crystal manufacturing apparatus of the embodiment of the present invention is performed by an indirect heating structure with a heating member that receives energy output from a high frequency coil, for example, temperature observation of the solution surface with a radiation thermometer and / Or a temperature control device (not shown) based on the measured temperature obtained by measuring the temperature using a thermocouple installed inside the carbon rod, for example, a W-Re (tungsten / renium) thermocouple. it can.

In the method for producing a SiC single crystal using the SiC single crystal production apparatus of the present invention, except for changing the output ratio of at least two high-frequency coils, the production method known per se, for example, the solution method itself Known production methods such as the shape of the graphite crucible, the heating method, the heating time, the atmosphere, the heating rate and the cooling rate can be applied.
For example, the heating time by the indirect heating by the heat generating member that receives the energy output from the high frequency coil (the approximate time from the preparation of the raw material until the SiC saturation concentration is reached) is 20 minutes although it depends on the size of the crucible. About 10 to 10 hours (for example, about 1 to 10 hours), the atmosphere includes a rare gas, for example, an inert gas such as He, Ne, or Ar, or a part of them replaced with N ₂ or methane gas.
By using the SiC single crystal manufacturing apparatus of the present invention, it is possible to prevent the growth of polycrystals at a high temperature of about 2000 ° C., for example, at a solution temperature of about 1800 to 2100 ° C., particularly about 1850 to 2050 ° C. for a long time, for example, 1 hour or more. Can obtain a suppressed SiC single crystal.

Examples of the present invention will be described below.
In each of the following examples, SiC single crystal growth was performed under the following conditions.
Solution temperature: 1900 ° C
Gas flow rate: 5L / min Growth time: 1 hour

Example 1
The growth of the SiC single crystal was performed using the SiC single crystal manufacturing apparatus according to the embodiment of the present invention shown in FIG. The growth amount was 340 μm, and no polycrystalline adhesion was observed in the vicinity of the seed crystal.
The obtained SiC single crystal growth photograph (as-grown) is shown in FIG.

Comparative Example 1
The growth of the SiC single crystal was performed using the conventional SiC single crystal manufacturing apparatus shown in FIG. The growth amount was 340 μm, and polycrystal adhesion in the vicinity of the seed crystal was observed.
The obtained SiC single crystal growth photograph (as-grown) is shown in FIG.

  With the SiC single crystal manufacturing apparatus of the present invention, the inside of the growth furnace can be soaked, and even if crystal growth is performed at a high solution temperature of about 1800 to 2100 ° C. It becomes possible to prevent or suppress, and a SiC single crystal can be manufactured with high productivity.

DESCRIPTION OF SYMBOLS 1 SiC single crystal manufacturing apparatus of embodiment of this invention 2 Growth furnace 3 Raw material solution 4 Seed crystal 5 Support shaft 6 Crucible 7 Heat insulating material 8 Energy emission body 9 Heating member 10 Conventional SiC single crystal manufacturing apparatus 11 Space

Claims (3)

A seed crystal for growing a SiC single crystal on a SiC seed crystal substrate from a raw material solution heated to a solution temperature of 1800 to 2100 ° C. by a solution method in a growth furnace, supporting the seed crystal, and applying heat from the seed crystal Heat is generated by the energy output from the support shaft for transmitting to the outside, the crucible for storing the raw material solution , the heat insulating material for preventing heat dissipation from the crucible, and the energy emitting body capable of releasing a plurality of energy provided outside the furnace. In order to heat the inside of the growth furnace, a heat generating member is provided inside the heat insulating material , the growth furnace has a space at least above the crucible, and the heat generating member is a crucible and space inside the heat insulating material. SiC single crystal manufacturing apparatus provided on the entire surface surrounding the substrate. The SiC single crystal manufacturing apparatus according to claim 1, wherein the heat generating member is made of graphite. The SiC single crystal manufacturing apparatus according to claim 1 or 2, wherein the energy emitter is a high-frequency coil.