JP4310880B2 - Method and apparatus for producing silicon carbide single crystal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a silicon carbide (hereinafter referred to as SiC) single crystal that can be used as a material such as a semiconductor or a light emitting diode, and a manufacturing apparatus therefor.
[0002]
[Prior art]
As a method for producing a SiC single crystal used for a substrate of a semiconductor element, a sublimation method is widely adopted. FIG. 4 shows a cross-sectional configuration of a crystal growth apparatus used for this sublimation method.
[0003]
As shown in FIG. 4, SiC raw material powder 12 is arranged at the bottom of graphite crucible 11, SiC crystal substrate 13 is fixed to lid 11 a so as to face raw material powder 12, and heat treatment is performed to form SiC. By sublimating the raw material powder 12, the raw material gas 14 is supplied and recrystallized on the SiC single crystal substrate 13 to grow the SiC single crystal 15.
[0004]
Examples of gas phase species related to growth in the sublimation method include Si, SIC ₂ , and Si ₂ C. These vapor phase species have different equilibrium vapor pressures, and their proportions change depending on the growth temperature. For this reason, when trying to obtain a homogeneous high-quality single crystal with few defects, it prevents the Si / C ratio fluctuation, the graphite fine particles due to the rough surface of the graphite container, and the contamination of impurities contained in the graphite container, It is important to perform crystal growth under stable conditions.
[0005]
However, as described above, when the SiC single crystal 15 is grown in the graphite crucible 11, during the growth of the SiC single crystal 14, the vapor phase species containing Si or Si reacts with graphite (C) which is a crucible material. For this reason, it is difficult to avoid fluctuations in the Si / C ratio and contamination of the graphite fine particles and impurities contained in the graphite container into the single crystal. The difference in the number of Si and C atoms reaching the SiC single crystal 15 and the above-mentioned contaminants cause various defects, making it difficult to produce a high-quality SiC single crystal 15 with few defects.
[0006]
On the other hand, JP-A-10-139589 proposes that the inner wall surface of a graphite crucible is covered with silicon carbide polycrystal so as to surround a space in which a single crystal grows.
[0007]
However, although the method of the above publication can alleviate the fluctuation of the Si / C ratio to some extent, it cannot completely cover the surface of the graphite crucible, so it is still difficult to prevent the inclusion of impurities in the graphite fine particles and the graphite container. It is. There is also a problem that it takes time to grow a silicon carbide polycrystal in advance before performing single crystal growth.
[0008]
On the other hand, in Japanese Patent Application Laid-Open No. 11-116399, it has been proposed to prevent reaction between a gas phase species containing Si or Si and graphite in a graphite crucible by coating the inner wall surface of the graphite crucible with tantalum carbide. ing.
[0009]
However, even in this case, there is a problem that it takes time to perform coating with tantalum carbide in advance before performing single crystal growth.
[0010]
[Problems to be solved by the invention]
In view of the above points, the present invention can suppress fluctuations in the Si / C ratio in the sublimation gas without forming silicon carbide polycrystals or coating with tantalum carbide in advance, and is included in graphite fine particles and graphite containers. It is an object to make it possible to manufacture a high-quality single crystal with few defects without taking in impurities.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a silicon carbide single crystal substrate (3) serving as a seed crystal is placed in a graphite vessel (1) and sublimated to a silicon carbide single crystal substrate. In the method for manufacturing a silicon carbide single crystal in which the silicon carbide single crystal (4) is grown on the silicon carbide single crystal substrate by supplying the silicon carbide raw material (2), the gas (5) is provided along the inner wall surface of the container. And a silicon carbide single crystal is grown on the silicon carbide single crystal substrate while forming a gas fluid layer (5a) of gas on the surface of the inner wall surface.
[0012]
Thereby, the inner wall of a container is coat | covered and it can suppress that the gaseous-phase seed | species which contains Si or Si reacts with the graphite which comprises a container. This makes it possible to suppress fluctuations in the Si / C ratio in the sublimation gas without forming silicon carbide polycrystals or coating with tantalum carbide in advance, and without incorporating impurities contained in the graphite fine particles and the graphite container, High quality single crystals with few defects can be manufactured.
[0013]
Specifically, the container is provided with an inflow port through which gas flows in from the outside of the container, and the container is provided with an outflow port through which gas flows out of the container. After the gas flows into the container from the inflow port, , Ru drained gas out of the container from the outlet.
[0014]
Then, the flow rate of the gas to 0.1 to 10 m / s. With such a flow rate, the gas can flow without diffusing too much into the growth space.
[0015]
The invention according to claim 2 is characterized in that after the gas flow rate is stabilized, the sublimated silicon carbide raw material is supplied. In this way, since the gas fluid layer is already formed when the sublimated silicon carbide raw material is supplied, a high-quality crystal can be obtained from the initial stage of growth of the silicon carbide single crystal.
[0016]
The gas shown in claim 1 can be, for example, an inert gas, or a mixed gas of an inert gas and a dopant to be introduced into the silicon carbide single crystal, as shown in claim 3 . Since the inert gas does not react with the sublimation gas of graphite or silicon carbide raw material, the Si / C ratio is not changed, and if the dopant is mixed, a process for introducing the dopant into the silicon carbide single crystal is not performed later. It will be better.
[0017]
An introduction port may be provided at a position different from the gas inlet in the vessel, and the sublimated silicon carbide raw material may be introduced into the vessel through the introduction port (1e) .
[0018]
Thus, if the silicon carbide raw material sublimated is introduced through the inlet provided at a position different from the gas inlet, the silicon carbide single crystal is continuously formed without depletion of the silicon carbide raw material. Can be grown.
[0019]
In this case, in flowing gas as crystal growth room for growing the carbonization silicon single crystal is enclosed, if to introduce a silicon carbide raw material is sublimed from the inside of the peripheral surrounding gas, silicon carbide was sublimed It is possible to prevent the raw material from being carried to the gas.
[0020]
Moreover, it is preferable that the flow rate of the sublimated silicon carbide raw material supplied through the inlet is slower than the flow rate of the gas . Thereby, it is possible to prevent the gas fluid layer from being disturbed by the flow of the sublimated silicon carbide raw material.
[0021]
In addition, invention of Claim 4-10 is invention of the manufacturing apparatus used for implementation of the manufacturing method of the silicon carbide single crystal of the said Claim 1 thru | or 3 .
[0022]
In the invention according to claim 4 , the container (1) is arranged with a cylindrical crucible body (1a) having an open bottom and a first gap (S2) from the inner peripheral surface of the crucible body. It has a cup-shaped raw material container (1c), and an inflow port is constituted by the first gap.
[0023]
Thus, an inflow port can be comprised by providing a 1st clearance gap between a crucible main body and a bottom face part. Then, if a raw material container cup-shaped housing the carbonization silicon material, it is possible to form the first gap without adding a new configuration.
Furthermore, in the invention according to claim 4, the lid member (1b) to which the silicon carbide single crystal substrate is attached by providing the second gap (S1) from the outer peripheral surface of the crucible body is disposed on the upper surface side of the crucible body. The outlet is constituted by the second gap.
Thus, by providing the second gap between the crucible main body and the lid member, the outflow port can be configured without adding a new configuration.
[0024]
The invention according to claim 5 is characterized in that the first gap is 1 to 20 mm. By setting the first gap to this extent, the gas flow rate can be secured, and a gas fluid layer having a stable thickness can be formed.
[0027]
The invention according to claim 6 is characterized in that the second gap is larger than the first gap and not more than 50 mm. By doing so, most of the gas that has flowed in can flow out of the container, so that a stable Si / C ratio can be maintained without changing the pressure of the sublimation gas of the silicon carbide raw material. it can.
[0028]
In a seventh aspect of the invention, the lid member is characterized in that it has a parabolic shape in cross section such that a central portion to which the silicon carbide single crystal is attached protrudes most toward the bottom surface side. In this way, if the lid member has a parabolic cross section, the outer wall of the lid member has a smooth curve, so that the lid member does not hinder gas flow.
[0029]
The invention described in claim 8 is characterized in that the crucible body has a cylindrical shape. Since such a cylindrical shape has no irregularities on the inner wall, the gas fluid layer can be reliably formed in contact with the inner wall of the crucible body.
[0030]
The invention according to claim 9 is characterized in that the crucible main body has a conical shape extending to the downstream side of the gas flow path. Thus, if the crucible body is configured in a conical shape, the gas can flow more easily, and the gas can be prevented from diffusing into the growth space of the silicon carbide single crystal.
[0031]
The invention described in claim 10 is characterized in that the crucible body forms a hollow hexagonal column. In this case, since it is equal to the crystal form of the silicon carbide single crystal to be grown, crystal defects are hardly induced and a high quality silicon carbide single crystal can be obtained.
[0032]
In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a crystal growth apparatus used in the first embodiment of the present invention. A graphite crucible 1 used as a container of this crystal growth apparatus is a method in which a SiC raw material powder (SiC raw material) 2 provided at the bottom of a graphite crucible 1 is sublimated by heat treatment, and is deposited on a SiC single crystal substrate 3 as a seed crystal. The SiC single crystal 4 is crystal-grown.
[0034]
This graphite crucible 1 is arranged on the bottom side of the crucible body 1a, a substantially cylindrical crucible body 1a having an open top surface and a bottom surface, a graphite lid 1b disposed on the upper surface side of the crucible body 1a. And a raw material container 1c made of graphite constituting the bottom surface portion.
[0035]
The lid 1b of the graphite crucible 1 has a substantially parabolic cross section in which the upper surface has a circular shape, and the central portion of the circular shape projects most toward the bottom surface. By setting it as such a shape, the outer wall of the lid | cover material 1b becomes a smooth surface, and it can prevent it from interfering with the flow of the gas 5 mentioned later. Between the outer peripheral wall on the upper surface of the lid member 1b and the inner wall of the crucible main body 1a, a substantially uniform gap (second gap) S1 is provided. In the present embodiment, the gap S1 is about 50 mm or less. Then, using this lid 1b as a base, SiC single crystal substrate 3 is bonded to the center of lid 1b via an adhesive or the like.
[0036]
On the other hand, the raw material container 1c of the graphite crucible 1 has a cup shape with a circular bottom, and accommodates the SiC raw material powder 2. A gap (first gap) S <b> 2 having substantially equal intervals is also provided between the outer peripheral wall of the raw material container 1 c and the inner peripheral wall of the crucible main body 1 a. In the present embodiment, the gap S2 is made smaller than the gap S1. Here, the gap S2 is set to 1 to 20 mm.
[0037]
Although not shown, the graphite crucible 1 can be heated by a heating device in a vacuum vessel into which argon gas can be introduced. For example, by adjusting the power of the heating device, SiC that is a seed crystal is used. The temperature of the single crystal substrate 3 can be maintained at a temperature lower by about 100 ° C. than the temperature of the SiC raw material powder 2.
[0038]
A method for manufacturing SiC single crystal 4 using the crystal growth apparatus configured as described above will be described.
[0039]
First, as shown by an arrow A in the figure, the gas 5 is caused to flow into the graphite crucible 1 from the gap S2 between the crucible main body 1a and the raw material container 1c, and also from the gap S1 between the crucible main body 1a and the lid material 1b. Thereby, the gas 5 flows along the inner peripheral wall of the crucible body 1a. At this time, if the flow rate of the gas 5 is slow, the gas 5 cannot flow from the gap S2 to the gap S1, and diffuses to the growth space side of the SiC single crystal 4 as indicated by an arrow B in the figure. The flow rate of 5 is, for example, 0.1 to 10 m / s, preferably 1 m / s or more. As the gas 5, an inert gas or a mixed gas of an inert gas and a dopant to be introduced into the SiC single crystal 4 is used. As described above, if an inert gas is used, the Si / C ratio is not changed, and impurities contained in the graphite fine particles and the graphite crucible 1 are not generated. There is no need to perform the introducing step later.
[0040]
Then, after the flow rate of the gas 5 is stabilized, the temperature of the SiC raw material powder 2 is heated to 2000 to 2500 ° C., and the SiC single crystal substrate 3 is set to a temperature lower than that of the SiC raw material powder 2, so A temperature gradient is provided. At this time, the pressure in the graphite crucible 1 is set to 1.3 × 10 to 1.3 × 10 ⁴ Pa (0.1 to 100 Torr).
[0041]
Thereby, the SiC raw material powder 2 is sublimated to become a raw material gas 6 such as vapor phase species Si, SiC ₂ , Si ₂ C, etc., and reaches the SiC single crystal substrate 3. Then, SiC single crystal 4 grows on SiC single crystal substrate 3 that is at a relatively low temperature.
[0042]
At this time, since the gas 5 flows along the inner peripheral wall of the crucible body 1a, a gas fluid layer 5a of the gas 5 is formed on the wall surface serving as the flow path of the gas 5. When the flow rate of the gas 5 is set to 0.1 to 10 m / s as in the present embodiment, the gas fluid layer 5a having a thickness of about 1 to 10 mm is formed. If the flow rate of the gas 5 is slow (the flow rate is small), the thickness of the gas fluid layer 5a becomes thin or the gas fluid layer 5a is hardly formed. Can be formed.
[0043]
Therefore, the gas fluid layer 5a covers almost the entire inner wall of the crucible body 1a, the outer wall of the raw material container 1c, and the outer wall of the lid 1b, that is, the inner wall of the graphite crucible 1. Thereby, it can suppress that the raw material gas 6 which is a gaseous-phase seed | species containing Si and Si reacts with the graphite (C) which comprises the crucible 1 made from graphite. The gas fluid layer 5a having a thickness of about 1 to 10 mm is thick enough to prevent contact between the raw material gas 6 and graphite, and the raw material gas 6 and graphite are formed by this thickness of the gas fluid layer 5a. It has been confirmed that the reaction with can be almost completely prevented.
[0044]
Thereby, the fluctuation of the Si / C ratio of the raw material gas 6 in the graphite crucible 1 is suppressed, and impurities contained in the graphite fine particles and the graphite crucible 1 can be prevented from being taken into the SiC single crystal. A small number of high-quality SiC single crystals 4 can be obtained.
[0045]
In the present embodiment, since the SiC raw material powder 2 is heated after the flow rate of the gas 5 is stabilized, the raw material gas 6 and the graphite constituting the graphite crucible 1 from the beginning of the growth of the SiC single crystal 4 It is possible to suppress this reaction and more effectively suppress fluctuations in the Si / C ratio. Thereby, it is possible to grow a high-quality SiC single crystal 4 from the initial stage of growth.
[0046]
In addition, since the gap S1 serving as the outlet is wider than the gap S2 serving as the inlet of the gas 5, most of the gas 5 that has flowed in can be reliably discharged, so that the inside of the graphite crucible 1 A stable Si / C ratio can be maintained without changing the pressure.
[0047]
Furthermore, since the crucible body 1a has a cylindrical shape with no irregularities on the inner peripheral wall, the gas fluid layer 5a can be reliably formed in contact with the inner wall of the crucible body 1a.
[0048]
And since the inflow port and outflow port which can perform such a flow of gas 5 are constituted by gap S2 between crucible body 1 and raw material container 1c and gap S1 between crucible body 1a and lid material 1b, these Therefore, it is possible to provide a crystal growth apparatus having a simple structure without adding new parts.
[0049]
(Second Embodiment)
FIG. 2 shows a cross-sectional configuration of a crystal growth apparatus used in the second embodiment of the present invention. As shown in FIG. 2, in this embodiment, the shape of the crucible body 1 a is changed with respect to the first embodiment, and the crucible body has a conical shape in which the diameter of the hollow portion is widened downstream in the flow direction of the gas 5. 1a is constituted.
[0050]
Thus, if the crucible main body 1a is configured in a conical shape, the gas 5 can flow more easily, and the gas 5 can be prevented from diffusing into the growth space of the SiC single crystal 4.
[0051]
( Reference embodiment)
FIG. 3 shows a cross-sectional configuration of the crystal growth apparatus used in the reference embodiment of the present invention. As shown in FIG. 3, in the present embodiment, unlike the first embodiment, the raw material gas 6 is provided on the bottom surface portion 1d of the graphite crucible 1 instead of sublimating the SiC raw material powder 2 (see FIG. 1). It introduces from the introduction port 1e. The introduction port 1e may be formed at any location of the graphite crucible 1, but in this embodiment, the center of the bottom surface of the graphite crucible 1 so as not to interfere with the flow path of the gas 5, that is, It is formed inside the growth space surrounded by the gas 5.
[0052]
The flow rate of the raw material gas 6 introduced from the introduction port 1e is made slower than the flow rate of the gas 5. By doing so, the gas fluid layer 5a is not disturbed by the flow of the raw material gas 6.
[0053]
Thus, if the source gas 6 is introduced from the outside of the graphite crucible 1, the source gas 6 can be supplied without being depleted, so that the SiC single crystal 4 can be continuously grown.
[0054]
Further, since the introduction port 1e of the source gas 6 is provided at a position different from the inlet of the gas 5, the gas fluid layer 5a and the source gas 6 can be prevented from being mixed. Furthermore, the raw material gas 6 can be prevented from flowing out of the graphite crucible 1 together with the gas 5 by arranging the raw material gas 6 at the center of the bottom surface portion 1 d of the graphite crucible 1.
[0055]
(Other embodiments)
In each said embodiment, although the example which comprised the crucible main body 1a of the graphite crucible 1 by the cylindrical shape was given, it does not necessarily need to be a cylindrical shape. For example, it can also comprise a hollow polygonal column. In addition, when the crucible body 1a is constituted by a hexagonal column having a hollow shape, it is equal to the crystal shape of the SiC single crystal 4 to be grown. Is possible.
[0056]
【Example】
Example 1
Using the graphite crucible 1 shown in FIG. 1, a growth experiment of the SiC single crystal 4 was performed based on the manufacturing method. The gap 1b between the raw material container 1c filled with the SiC raw material powder 2 and the crucible main body 1a was set to 10 mm, and the gap S1 between the lid 1b to which the SiC single crystal substrate 3 was attached and the crucible main body 1a was set to 20 mm.
[0057]
After making the inside of the graphite crucible 1 an inert gas atmosphere and setting the pressure to about 1.3 × 10 ⁴ Pa (100 Torr), the inert gas is introduced from the gap S2 between the graphite crucible 1 and the raw material container 1c. The gas 5 constituted by was introduced at a flow rate of 1 m / S, and was caused to flow out from the gap S1 between the crucible body 1a and the lid 1b.
[0058]
After the flow rate of the gas 5 is stabilized, the temperature of the SiC raw material powder 3 is set to about 2300 ° C., and the temperature gradient at the initial stage of growth is 4 ° C./cm. I let you. The amount of growth of the obtained SiC single crystal 4 was 1.8 mm.
[0059]
The obtained SiC single crystal 4 ingot was cut and polished in the growth direction, and the cross section was observed with a microscope. As a result of observing this cross section, the generation of crystal defects that frequently occur in the early stage of growth was suppressed, and the SiC single crystal 4 was a homogeneous single crystal from the start to the end of growth.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross-sectional configuration of a crystal growth apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a cross-sectional configuration of a crystal growth apparatus according to a second embodiment of the present invention.
FIG. 3 is a diagram showing a cross-sectional configuration of a crystal growth apparatus in a reference embodiment of the present invention.
FIG. 4 is a diagram showing a cross-sectional configuration of a conventional crystal growth apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Graphite crucible, 1a ... Crucible body, 1b ... Cover material, 1c ... Raw material container,
2 ... SiC raw material powder, 3 ... SiC single crystal substrate, 4 ... SiC single crystal, 5 ... gas,
5a ... gas fluid layer, 6 ... raw material gas.

Claims (10)

By disposing a silicon carbide single crystal substrate (3) serving as a seed crystal in a graphite container (1) and supplying a silicon carbide raw material (6) sublimated to the silicon carbide single crystal substrate, the carbonization is performed. In the method for producing a silicon carbide single crystal in which a silicon carbide single crystal (4) is grown on a silicon single crystal substrate,
To the container, provided with an inlet for flowing gas from the outside of the vessel, an outlet for flow out the gas to the outside of the container is provided, after allowed to flow into the gas into the container from the inlet The gas (5) flows along the inner wall surface of the container by flowing the gas out of the container from the outlet at a flow rate of 0.1 to 10 m / s, and the gas flows on the inner wall surface. A method for producing a silicon carbide single crystal, comprising growing the silicon carbide single crystal on the silicon carbide single crystal substrate while forming a gas fluid layer (5a). Method for producing a silicon carbide single crystal according to claim 1 in which the flow rate of the gas, characterized in that after the stable, to supply the silicon carbide raw material in which the sublimed. 3. The method for producing a silicon carbide single crystal according to claim 1, wherein the gas is an inert gas, or a mixed gas of an inert gas and a dopant to be introduced into the silicon carbide single crystal. . By disposing a silicon carbide single crystal substrate (3) serving as a seed crystal in a graphite container (1) and supplying a silicon carbide raw material (6) sublimated to the silicon carbide single crystal substrate, the carbonization is performed. In a silicon carbide single crystal manufacturing apparatus for growing a silicon carbide single crystal (4) on a silicon single crystal substrate,
The container includes a cylindrical crucible body (1a) having an open top surface and a bottom surface, a lid member (1b) disposed in the crucible body (1a) and having a central portion projecting most toward the bottom surface, A cup-shaped raw material container (1c) containing the silicon carbide raw material (6), and is constituted by a first gap (S2) between the crucible body (1a) and the raw material container (1c). The gas inlet (5) from the outside of the container and the second gap (S1) between the crucible body (1a) and the lid member (1b) are configured to flow in through the inlet. An outflow port through which the gas flows out to the outside. The gas flows along the inner wall surface of the container, and a gas fluid layer (5a) is formed on the surface of the inner wall surface by the gas. Silicon carbide unit characterized by being composed of Crystal manufacturing apparatus. The said 1st clearance gap is 1-20 mm, The manufacturing apparatus of the silicon carbide single crystal of Claim 4 characterized by the above-mentioned. The said 2nd clearance gap is larger than the said 1st clearance gap, and is 50 mm or less, The manufacturing apparatus of the silicon carbide single crystal of Claim 4 or 5 characterized by the above-mentioned. The lid member is described in any one of claims 4 to 6, wherein the central portion of the silicon carbide single crystal is mounted is formed into a cross-sectional parabolic shape as to protrude the most the bottom side An apparatus for producing a silicon carbide single crystal. The apparatus for producing a silicon carbide single crystal according to any one of claims 4 to 7 , wherein the crucible body has a cylindrical shape. The apparatus for producing a silicon carbide single crystal according to any one of claims 4 to 8 , wherein the crucible main body has a conical shape extending downstream of the gas flow path. 10. The silicon carbide single crystal manufacturing apparatus according to claim 4, wherein the crucible main body forms a hollow hexagonal column.

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