JP4742448B2 - Method and apparatus for producing silicon carbide single crystal - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a silicon carbide single crystal manufacturing method and a manufacturing apparatus capable of growing a silicon carbide single crystal with high yield and high efficiency by using a CVD method (chemical vapor phase method).
[0002]
[Prior art]
Silicon carbide is expected as a semiconductor for power devices because of its high breakdown voltage and high electron mobility. As a method for producing a silicon carbide single crystal serving as the substrate, there are generally a method called a sublimation method (improved Rayleigh method) and a CVD method. In the improved Rayleigh method, a silicon carbide raw material is inserted into a graphite crucible, and a seed crystal (substrate crystal) is mounted on the inner wall of the graphite crucible so as to face the raw material portion. And a silicon carbide single crystal is grown by heating a raw material part to 2200-2400 degreeC, generating a sublimation gas, and making it recrystallize on the seed crystal made several tens-several hundred degreeC low temperature from the raw material part.
[0003]
In this improved Rayleigh method, the silicon carbide raw material decreases as the silicon carbide single crystal grows, so there is a limit to the amount that can be grown. Even if a means for adding the raw material during the growth is taken, the sublimation gas in the crucible is added when the raw material is added during the growth because the Si / C ratio sublimates when SiC sublimates. The concentration and sublimation rate fluctuate, which hinders continuous growth of crystals with high quality.
[0004]
On the other hand, as a method for epitaxially growing silicon carbide by the CVD, for example, there is a method disclosed in JP-T-11-508531. This method is a method in which a seed crystal is arranged in a cylindrical reaction tube (susceptor), and a raw material gas containing Si or C is supplied to grow a silicon carbide single crystal on the seed crystal.
According to this method, since the reaction gas can be continuously supplied, the silicon carbide single crystal can be continuously grown for a long time as compared with the improved Rayleigh method.
[0005]
[Problems to be solved]
However, in the conventional CVD method, the crystal growth location is not limited to the seed crystal, but carbonization is also performed at an unnecessary location such as the inner peripheral surface of the reaction tube or the vicinity of the discharge port for discharging the source gas. Silicon crystals are deposited and grow. For this reason, the growth of the silicon carbide crystal at the unnecessary portion does not continue the supply of the source gas, and the growth of the silicon carbide single crystal on the seed crystal must be stopped halfway.
[0006]
As a countermeasure, for example, as shown in WO 98/14644, clogging of the exhaust port is prevented by introducing a gas (He) that does not participate in the reaction along the circumference of the reaction vessel. There is a way. However, in this method, it is inevitable that the silicon carbide single crystal (grown crystal) itself that grows on the seed crystal is etched. For this reason, the yield of the grown crystal is lowered and the productivity is lowered.
[0007]
The present invention has been made in view of such conventional problems, and suppresses deposition of a silicon carbide single crystal at an unnecessary portion other than the growth end face of the growth crystal while ensuring growth at the growth end of the growth crystal. An object of the present invention is to provide a method and an apparatus for producing a silicon carbide single crystal capable of growing a grown crystal over a long period of time.
[0008]
[Means for solving problems]
According to a first aspect of the present invention, a pedestal that supports a substrate crystal made of a silicon carbide single crystal is disposed in a reaction vessel having a cylindrical peripheral wall, and silicon containing silicon is directed toward the substrate crystal supported on the pedestal. A silicon-containing single crystal is grown on the substrate crystal by supplying a containing gas and a carbon-containing gas containing carbon, and the surplus silicon-containing gas and the carbon-containing gas pass between the pedestal and the peripheral wall. In a method for producing a silicon carbide single crystal that discharges
By discharging an etching gas having an effect of etching silicon carbide from the inside of the pedestal toward the outside, the etching gas is introduced near the outer periphery of the interface between the substrate crystal and the pedestal ,
By introducing the etching gas inward from the peripheral wall, the etching gas is introduced in the vicinity of the outer periphery of the growth end face of the growth crystal, which is a silicon carbide single crystal grown on the substrate crystal ,
The etching gas is mixed in at least two stages with respect to the surplus silicon-containing gas and the carbon-containing gas that are exhausted through the growth crystal and the peripheral wall. It exists in the manufacturing method of a crystal | crystallization (Claim 1).
[0009]
In the present invention, as described above, there are at least two locations near the outer periphery of the boundary surface between the substrate crystal and the pedestal and near the outer periphery of the growth end surface of the grown crystal that is a silicon carbide single crystal grown on the substrate crystal. The etching gas is introduced. Thereby, the deposition of the silicon carbide single crystal on the pedestal, the peripheral wall, and the exhaust system can be suppressed without almost etching the grown crystal.
[0010]
That is, the silicon-containing gas and the carbon-containing gas that have reached the growth end face of the growth crystal grow a silicon carbide single crystal on the substrate crystal or the growth end face of the growth crystal already formed thereon. The surplus gas that could not contribute to the growth of the crystal passes between the grown crystal and the peripheral wall and is exhausted.
At this time, in the present invention, the reactivity of the surplus gas can be changed in two steps by introducing the etching gas from the two places.
[0011]
First, the etching gas is introduced in the vicinity of the outer periphery of the growth end face of a grown crystal that is a silicon carbide single crystal grown on the substrate crystal. As a result, the state of the mixed gas of surplus silicon-containing gas and carbon-containing gas that still has reactivity is changed so that the degree of supersaturation approaches zero from the state where silicon and carbon are supersaturated and highly reactive. Gas works. Thereby, the mixed gas of the surplus gas and the etching gas changes to a state in which new crystal growth is suppressed and etching of the already obtained grown crystal is also suppressed.
[0012]
Next, the mixed gas passes through the side surface of the growth crystal and then mixes with the introduced etching gas in the vicinity of the outer periphery of the boundary surface between the substrate crystal and the pedestal. As a result, the above-mentioned mixed gas whose supersaturated state has already approached zero is changed to a sufficiently unsaturated state by the introduced etching gas, and also has the ability to etch silicon carbide crystals with the above-mentioned etching gas. It will be a thing. For this reason, the mixed gas at this stage reliably suppresses the growth of new silicon carbide crystals, and prevents the silicon gas from growing due to the etching power of the etching gas even if new silicon carbide crystals are to be grown and deposited. It will have.
[0013]
As described above, in the present invention, by introducing the etching gas in two stages, the supersaturation and the unsaturation of the silicon-containing gas and the carbon-containing gas can be performed in stages. Thereby, the deposition of the silicon carbide single crystal on the exhaust system can be prevented while preventing the growth crystal from being etched.
Therefore, the growth crystal can be grown for a long time.
In addition, if necessary, multi-stage etching gas introduction allows crystal growth with further excellent controllability.
[0014]
A second invention is directed to a reaction vessel having a cylindrical peripheral wall, a pedestal arranged in the reaction vessel for supporting a substrate crystal made of a silicon carbide single crystal, and the substrate crystal supported on the pedestal. Reactive gas supply means for supplying a silicon-containing gas containing silicon and a carbon-containing gas containing carbon, and passing between the pedestal and the peripheral wall to discharge excess silicon-containing gas and carbon-containing gas. In an apparatus for producing a silicon carbide single crystal having an exhaust passage,
First etching gas introduction means for introducing an etching gas effective to etch silicon carbide in the vicinity of the outer periphery of the interface between the substrate crystal and the pedestal;
Near the outer circumference of the end face of the grown silicon carbide is single crystal grown crystal on the substrate crystal, it has a second etching gas introducing means for introducing an etching gas having an effect of etching the silicon carbide,
The first etching gas introduction means has a first gas outlet that opens outward from the outer peripheral surface of the pedestal,
The second etching gas introducing means is to have a second gas injection port opening inwardly from the inner peripheral surface of the peripheral wall of the reaction vessel,
It is configured to mix the etching gas in at least two stages with respect to the surplus silicon-containing gas and the carbon-containing gas passing through the gap between the growth crystal and the peripheral wall. In a manufacturing apparatus of a silicon carbide single crystal.
[0015]
The manufacturing apparatus of the present invention has the first and second etching gas introduction means. Therefore, the etching gas can be introduced in two stages. Therefore, an excellent manufacturing method as described above can be executed, and the growth crystal of the silicon carbide single crystal can be grown for a long time.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In the first aspect of the invention , in the vicinity of the outer periphery of the boundary surface between the substrate crystal and the pedestal, the etching gas is introduced by discharging the etching gas from the inside of the pedestal toward the outside . Thereby , even when the pedestal moves, the introduction position of the etching gas can always be made constant, and a stable etching effect can be obtained.
[0017]
Further, in the vicinity of the outer periphery of the end face of the grown crystal, the etching gas is introduced by discharging the etching gas inward from the peripheral wall . Thereby , the supply of the etching gas to the outer periphery of the end face of the growth crystal can be easily adjusted according to the position of the growth end.
[0018]
Further, the etching gas is hydrogen, it is preferred halogen gas, a mixed gas containing one or more gases of hydrogen halide (claim 2). If these gases are used, the supersaturation degree of silicon and carbon in the silicon-containing gas and the carbon-containing gas can be easily adjusted, and the etching effect of the silicon carbide single crystal can be easily obtained.
[0019]
Oite to the second invention, the first etching gas introducing means includes a first gas injection port opening outwardly from the outer circumferential surface of the pedestal. As a result, an etching gas introduction path can be provided inside the pedestal, and the equipment structure for making the etching gas introduction position constant can be simplified.
[0020]
Further, the second etching gas introduction means has a second gas jet port that opens inward from the inner peripheral surface of the peripheral wall of the reaction vessel . As a result , an etching gas introduction path can be provided outside the peripheral wall, and the equipment structure for making the etching gas introduction position constant can be simplified.
[0021]
【Example】
Example 1
An embodiment relating to a method and apparatus for producing a silicon carbide single crystal of the present invention will be described with reference to FIG.
As shown in FIG. 1, the silicon carbide single crystal manufacturing apparatus 1 of this example includes a reaction vessel 2 having a cylindrical peripheral wall 20 and a substrate crystal 7 made of silicon carbide single crystal disposed in the reaction vessel 2. , A reaction gas supply means for supplying a silicon-containing gas 81 containing silicon and a carbon-containing gas 82 containing carbon toward the substrate crystal 7 supported by the pedestal 3, and the pedestal 3 And an exhaust passage 23 through which the excess silicon-containing gas and carbon-containing gas are discharged through the space between the peripheral walls 20.
[0022]
First etching gas introduction means 41 for introducing an etching gas 9 effective to etch silicon carbide in the vicinity of the outer periphery of the interface 37 between the substrate crystal 7 and the pedestal 3, and silicon carbide grown on the substrate crystal 7 Second etching gas introduction means 42 for introducing an etching gas 9 effective to etch silicon carbide is provided in the vicinity of the outer periphery of the end face 750 of the grown crystal 75 which is a single crystal.
[0023]
The first etching gas introduction means 41 of this example has a first gas ejection port 410 that opens outward from the outer peripheral surface 30 of the base 3. Then, an etching gas introduction pipe 415 is provided inside the pedestal 3 so as to communicate with the first gas ejection port 410, and an etching gas supply source (not shown) is connected thereto.
Further, the pedestal 3 is configured to rise in accordance with the growth of the growth crystal 75. Of course, the first gas outlet 410 rises with the rise of the base 3.
[0024]
Further, the second etching gas introduction means 42 of the present example has a second gas ejection port 420 that opens inward from the inner peripheral surface of the peripheral wall 20 of the reaction vessel 2. The second gas outlet 420 opens toward the outer periphery of the growth end face 750 of the growth crystal 75. An etching gas supply pipe 425 leading to the second gas jet port 420 is connected to an etching gas supply source (not shown).
[0025]
Further, in the manufacturing apparatus 1 of this example, the periphery of the reaction vessel 2 is covered with a quartz tube 15, and a heating high-frequency coil 18 is installed in a portion corresponding to the reaction vessel 2 on the outer side. . A lower lid (not shown) having a supply pipe for supplying the silicon-containing gas 81 and the carbon-containing gas 82 is provided at the lower end of the quartz tube 15, and various gases are exhausted at the upper end of the quartz tube 15. An upper lid (not shown) provided with an exhaust port is provided.
[0026]
In this example, a 4H—SiC single crystal substrate is used as the substrate crystal 7 and is arranged at the lower end of the pedestal 3. In addition, SiH ₄ gas was used as the silicon-containing gas 81, and C ₃ H ₈ was used as the carbon-containing gas 82. Then, as shown in FIG. 1, these gases 81 and 82 are introduced from below the reaction vessel 2 to grow SiC on the substrate crystal 7.
[0027]
The gas not used for growth and the H ₂ gas generated by decomposition of the raw material gas pass through the side surface of the growth crystal 75 and go to the exhaust port.
Here, the manufacturing apparatus 1 of this example includes the first etching gas introduction means 41 and the second etching means 42. Using these, the etching gas 9 is introduced from the first etching gas introduction means 41 near the outer periphery of the boundary surface 37 between the substrate crystal 7 and the pedestal 3. Further, the etching gas 9 is introduced from the second etching gas introduction means 42 in the vicinity of the outer periphery of the growth end face 750 of the growth crystal 75 which is a silicon carbide single crystal grown on the substrate crystal 7.
[0028]
As a result, the etching gas 9 is introduced from the outer peripheral direction at the growth end face level and from the pedestal at the interface level between the substrate crystal and the pedestal. Therefore, even if the pedestal 3 is moved along with the crystal growth, the relative introduction position is changed. Therefore, a steady etching gas can be introduced. The direction of introducing the etching gas may be the central axis direction (radial direction) or the tangential direction (swirl direction).
[0029]
The growth conditions in this example are as follows: substrate temperature 2000 to 2500 ° C., SiH ₄ flow rate = 50 to 800 sccm, C ₃ H ₈ flow rate = 10 to 300 sccm, Ar = 1 to 10 SLM as a carrier gas of SiH ₄ and C ₃ H ₈ , The pressure is 100 to 400 Torr, and the growth rate is 0.5 to 3 mm / h.
Further, H ₂ was used as the etching gas 9, and ₅ to 10 SLM was introduced into the second etching gas introduction means 42 and 10 to 30 SLM was introduced into the first etching gas introduction means 41.
[0030]
In this example, as a result of performing the growth for 30 hours, no large etching was observed on the side wall of the grown crystal 75, and no crystal deposition was observed even at the exhaust port, so that the crystal can be grown for a long time. I was able to confirm.
From this result, it can be seen that it is very effective to perform the two-stage etching gas introduction using the two etching gas introduction means 41 and 42 described above. The effects of the two-stage etching gas introduction are considered as follows.
[0031]
In other words, by introducing the etching gas 9 in the vicinity of the outer periphery of the growth end face 750 of the growth crystal 75 which is a silicon carbide single crystal grown on the substrate crystal 7, the surplus silicon-containing gas 81 and the carbon containing still reactive are contained. The mixed gas state of the gas 82 is high in the degree of supersaturation of silicon and carbon, and the state of supersaturation approaches zero from the state in which crystal growth proceeds. Thereby, the mixed gas of the surplus gas and the etching gas changes to a state in which new crystal growth is suppressed and etching of the already obtained grown crystal is also suppressed.
[0032]
Next, the mixed gas passes through the side surface of the growth crystal 75 and then mixes with the introduced etching gas 9 in the vicinity of the outer periphery of the boundary surface 37 between the substrate crystal 7 and the pedestal 3. As a result, the mixed gas whose supersaturated state has already approached zero is sufficiently changed to an unsaturated state by the introduced etching gas 9, and has the ability to etch silicon carbide crystals by the etching gas 9. It will also have. For this reason, the mixed gas at this stage reliably suppresses the growth of new silicon carbide crystals, and even if new silicon carbide crystals are to be deposited, the deposition of the etching gas reliably prevents the deposition.
[0033]
As described above, in this example, by introducing the etching gas 9 in the two stages, the supersaturation and the desaturation of the silicon-containing gas 81 and the carbon-containing gas 82 can be performed in stages. it can. This is considered to have prevented the silicon carbide crystal from being deposited on the exhaust system while preventing the growth crystal 75 from being etched.
[0034]
(Example 2)
In this example, a manufacturing apparatus having the same configuration as in Example 1 was used, and only the point that HCl was used as the etching gas 9 was changed.
In this case, as in the case of using H ₂ as the etching gas, no large etching was observed on the side wall of the grown crystal 75, and no crystal deposition was observed at the exhaust port. Therefore, it was confirmed that long-time growth was possible by introducing the etching gas 9 in multiple stages.
[0035]
(Comparative example)
In this comparative example, the introduction of the etching gas 9 by the first etching gas introduction unit 41 in Example 1 is stopped, the etching gas 9 is introduced only from the second etching gas introduction unit 42, and the others are the same as in Example 1. A growth experiment was conducted.
As a result, in this comparative example, SiC was deposited on the pedestal side wall as the growth time progressed, and the exhaust port began to close.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing the configuration of a silicon carbide single crystal manufacturing apparatus in Example 1. FIG.
[Explanation of symbols]
1. . . Silicon carbide single crystal manufacturing equipment,
15. . . Quartz tube,
2. . . Reaction vessel,
20. . . Wall,
3. . . pedestal,
41. . . First etching gas introduction means,
42. . . Second etching gas introduction means,
7). . . Substrate crystal (seed crystal),
81. . . Silicon-containing gas,
82. . . Carbon-containing gas,
83. . . Carrier gas,
9. . . Etching gas,

Claims (5)

A pedestal that supports a substrate crystal made of a silicon carbide single crystal is disposed in a reaction vessel having a cylindrical peripheral wall, and contains a silicon-containing gas containing silicon and carbon toward the substrate crystal supported on the pedestal. A silicon carbide single crystal that supplies a carbon-containing gas to grow a silicon carbide single crystal on the substrate crystal and passes between the pedestal and the peripheral wall to discharge excess silicon-containing gas and carbon-containing gas. In the method for producing crystals,
By discharging an etching gas having an effect of etching silicon carbide from the inside of the pedestal toward the outside, the etching gas is introduced near the outer periphery of the interface between the substrate crystal and the pedestal ,
By introducing the etching gas inward from the peripheral wall, the etching gas is introduced in the vicinity of the outer periphery of the growth end face of the growth crystal, which is a silicon carbide single crystal grown on the substrate crystal ,
The etching gas is mixed in at least two stages with respect to the surplus silicon-containing gas and the carbon-containing gas that are exhausted through the growth crystal and the peripheral wall. Crystal production method. 2. The method for producing a silicon carbide single crystal according to claim 1, wherein the etching gas is a mixed gas containing one or more of hydrogen, halogen gas, and hydrogen halide.   3. The method for producing a silicon carbide single crystal according to claim 1, wherein a direction in which the etching gas is discharged from the inside to the outside of the pedestal is an outer tangential direction.   4. The etching according to claim 1, wherein an amount of the etching gas introduced near the outer periphery of the boundary surface between the substrate crystal and the pedestal is introduced near the outer periphery of the growth end face of the grown crystal. A method for producing a silicon carbide single crystal, wherein the amount is greater than the amount of gas introduced. A reaction vessel having a cylindrical peripheral wall; a pedestal arranged in the reaction vessel for supporting a substrate crystal made of a silicon carbide single crystal; and silicon containing silicon toward the substrate crystal supported on the pedestal A carbonization gas having a reactive gas supply means for supplying a carbon-containing gas containing carbon and a gas, and an exhaust passage for discharging the excess silicon-containing gas and the carbon-containing gas through the pedestal and the peripheral wall. In silicon single crystal manufacturing equipment,
First etching gas introduction means for introducing an etching gas effective to etch silicon carbide in the vicinity of the outer periphery of the interface between the substrate crystal and the pedestal;
Near the outer circumference of the end face of the grown silicon carbide is single crystal grown crystal on the substrate crystal, it has a second etching gas introducing means for introducing an etching gas having an effect of etching the silicon carbide,
The first etching gas introduction means has a first gas outlet that opens outward from the outer peripheral surface of the pedestal,
The second etching gas introducing means is to have a second gas injection port opening inwardly from the inner peripheral surface of the peripheral wall of the reaction vessel,
It is configured to mix the etching gas in at least two stages with respect to the surplus silicon-containing gas and the carbon-containing gas passing through the gap between the growth crystal and the peripheral wall. An apparatus for producing a silicon carbide single crystal.

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