JP2002362998A - Method and device for producing silicon carbide single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for producing a silicon carbide single crystal, by which deposition of the silicon carbide single crystal at inappropriate places other than the growth end surface of the growing crystal can be suppressed, and the growth of the growing crystal for a long time is possible, and a manufacturing device for the silicon carbide single crystal. SOLUTION: A pedestal 3 for supporting a substrate crystal 7 formed from a silicon carbide single crystal is placed in a reaction vessel 2 having a cylindrical peripheral wall 20. The silicon carbide single crystal is grown on the substrate crystal 7 by supplying a silicon containing gas 81, a carbon containing gas 82 and a carrier gas 83 toward the substrate crystal 7 supported by the pedestal 3, and at the same time, the excess silicon containing gas 81, the excess carbon containing gas 82 and the exess carrier gas 83 are discharged through between the pedestal 3 and the peripheral wall 20. An etching gas of etching silicon carbide is introduced to the neighborhood of the periphery of the interface 37 of the substrate crystal 7 and the pedestal 3 and the neighborhood of the periphery of growing end surface 750 of growing crystal 75 of the silicon carbide single crystal grown on the substrate crystal 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a silicon carbide single crystal which can grow a silicon carbide single crystal with high yield and high efficiency by utilizing a CVD (chemical vapor deposition) method.

[0002]

2. Description of the Related Art Silicon carbide has characteristics of high breakdown voltage and high electron mobility, and is therefore expected as a semiconductor for power devices. As a method of manufacturing 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. Then, the raw material section was changed to 2200
Sublimation gas is generated by heating to a temperature of about 2400 ° C. and recrystallized on a seed crystal cooled several tens to several hundreds degrees Celsius lower than the raw material to grow a silicon carbide single crystal.

In the improved Rayleigh method, the amount of silicon carbide raw material decreases with the growth of the silicon carbide single crystal, so that the amount that can be grown is limited. And even if a means for adding a raw material during the growth is employed, the sublimation gas in the crucible is increased when the raw material is added during the growth because the Si / C ratio sublimates at a ratio of more than 1 when the SiC is sublimated. The concentration and the sublimation rate fluctuate, which hinders continuous high-quality crystal growth.

On the other hand, as a method for epitaxially growing silicon carbide by the CVD, for example, Japanese Patent Application Laid-Open
There is a method disclosed in JP-A-508531. In this method, a seed crystal is placed in a cylindrical reaction tube (susceptor), and a source gas containing Si or C is supplied to grow a silicon carbide single crystal on the seed crystal. According to this method, the supply of the reaction gas can be performed continuously, so that the silicon carbide single crystal can be continuously grown for a long time as compared with the modified Rayleigh method.

[0005]

However, the above-mentioned conventional C
In the VD method, the silicon carbide crystal is deposited not only on the seed crystal but also on an unnecessary portion such as on the inner peripheral surface of the reaction tube or in the vicinity of the outlet for discharging the source gas. grow up. Therefore, the supply of the source gas cannot be continued due to the growth of the silicon carbide crystal at the unnecessary portion, and the growth of the silicon carbide single crystal on the seed crystal must be stopped halfway.

As a countermeasure against this, for example, WO 98/14
As disclosed in Japanese Patent No. 644, there is a method for preventing clogging of an exhaust port by introducing a gas (He) not involved in the reaction along the circumference of the reaction vessel. However, in this method, it is inevitable that the silicon carbide single crystal (grown crystal) itself grown on the seed crystal is etched. As a result, the yield of grown crystals decreases,
Productivity decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to secure the growth at the growth end of a grown crystal and to deposit a silicon carbide single crystal at an unnecessary portion other than the growth end face of the grown crystal. It is an object of the present invention to provide a method and an apparatus for manufacturing a silicon carbide single crystal, which can suppress growth and allow a grown crystal to grow for a long time.

[0008]

According to a first aspect of the present invention, a pedestal for supporting a substrate crystal made of silicon carbide single crystal is arranged in a reaction vessel having a cylindrical peripheral wall, and the pedestal is directed toward the substrate crystal supported on the pedestal. A silicon-containing gas containing silicon and a carbon-containing gas containing carbon are supplied to grow a silicon carbide single crystal on the substrate crystal, and pass through the space between the pedestal and the peripheral wall to contain the excess silicon-containing gas. In the method for producing a silicon carbide single crystal for discharging a gas and the carbon-containing gas, a growth of a growth crystal, which is a silicon carbide single crystal grown on the substrate crystal, near an outer periphery of a boundary surface between the substrate crystal and the pedestal. A method for producing a silicon carbide single crystal, characterized in that an etching gas having an effect of etching silicon carbide is introduced into the vicinity of an outer periphery of an end face.

In the present invention, as described above, at least the vicinity of the outer periphery of the boundary surface between the substrate crystal and the pedestal and the vicinity of the outer periphery of the growth end face of the silicon carbide single crystal grown on the substrate crystal. The etching gas is introduced into two places. Thereby, deposition of the silicon carbide single crystal on the pedestal, the peripheral wall, and the exhaust system can be suppressed without substantially etching the grown crystal.

That is, the silicon-containing gas and the carbon-containing gas reaching the growth end face of the grown crystal grow a silicon carbide single crystal on the growth end face of the substrate crystal or the growth crystal already formed thereon. Excess gas that has not contributed to the growth of the crystal passes through the space 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 stages by introducing the etching gas from the two locations.

First, in the vicinity of the outer periphery of the growth end face of a silicon carbide single crystal grown on the substrate crystal,
The above etching gas is introduced. Thereby, the above-mentioned etching is performed so that the state of the mixed gas of the surplus silicon-containing gas and the carbon-containing gas still reactive becomes closer to the state where the degree of supersaturation becomes zero from the state where silicon and carbon are supersaturated and highly reactive. Gas works. As a result, the mixed gas of the surplus gas and the etching gas changes to a state that suppresses new crystal growth and also suppresses etching of the already-grown grown crystal.

Next, after passing through the side surface of the grown crystal, the mixed gas is mixed with the introduced etching gas near the outer periphery of the boundary between the substrate crystal and the pedestal. Thus, the mixed gas whose supersaturated state has already approached zero is sufficiently changed to an unsaturated state by the introduced etching gas, and also has a capability of etching the silicon carbide crystal by the etching gas. It will be. Therefore, the mixed gas at this stage reliably suppresses the growth of new silicon carbide crystals,
And even if a new silicon carbide crystal grows and deposits,
It has the property of preventing the deposition by the etching power of the etching gas.

As described above, in the present invention, the introduction of the etching gas in the above-described two stages allows the supersaturation of the silicon-containing gas and the carbon-containing gas to be eliminated and desaturated to be performed in a stepwise manner. Can be. Thereby, it is possible to prevent the silicon carbide single crystal from being deposited on the exhaust system while preventing the growth crystal from being etched. Therefore, the grown crystal can be grown for a long time.
In addition, by introducing a multi-stage etching gas as needed, crystal growth with more excellent controllability can be achieved.

According to a second aspect of the present invention, there is provided a reaction vessel having a cylindrical peripheral wall, a pedestal for supporting a substrate crystal made of silicon carbide single crystal disposed in the reaction vessel, and the substrate supported on the pedestal. Reaction gas supply means for supplying a silicon-containing gas containing silicon and a carbon-containing gas containing carbon toward the crystal; and an excess of the silicon-containing gas and the carbon-containing gas which pass between the pedestal and the peripheral wall. A first etching gas for introducing an etching gas having an effect of etching silicon carbide into the vicinity of an outer periphery of a boundary surface between the substrate crystal and the pedestal in the apparatus for manufacturing a silicon carbide single crystal having an exhaust passage for discharging gas. Means and a second etching gas for introducing an etching gas having an effect of etching silicon carbide in the vicinity of the outer periphery of the end face of the grown crystal which is a silicon carbide single crystal grown on the substrate crystal. In apparatus for producing a silicon carbide single crystal and having a Ngugasu introducing means (claim 5).

The manufacturing apparatus of the present invention has the first and second etching gas introducing means. Therefore, the introduction of the etching gas can be performed in two stages. Therefore, an excellent manufacturing method can be performed as described above, and a silicon carbide single crystal can be grown for a long time.

[0016]

In the first invention (claim 1), the etching gas is discharged from the inside of the pedestal to the outside near the outer periphery of the boundary between the substrate crystal and the pedestal. It is preferable to introduce it by adding (claim 2). In this case, even when the pedestal moves, the position where the etching gas is introduced can always be kept constant, and a stable etching effect can be obtained.

Further, in the vicinity of the outer periphery of the end face of the grown crystal, it is preferable to introduce the etching gas by discharging the etching gas inward from the peripheral wall. In this case, the supply of the etching gas to the outer periphery of the end face of the grown crystal can be easily adjusted according to the position of the growth end.

It is preferable that the etching gas is a mixed gas containing one or more of hydrogen, halogen gas, and hydrogen halide. When these gases are used, the degree of supersaturation of silicon and carbon in the silicon-containing gas and the carbon-containing gas can be easily adjusted, and the effect of etching a silicon carbide single crystal can be easily obtained.

In the second invention (claim 5),
It is preferable that the first etching gas introducing means has a first gas ejection port that opens outward from an outer peripheral surface of the pedestal. Thus, the introduction path of the etching gas can be provided inside the pedestal, and the equipment structure for making the introduction position of the etching gas constant can be simplified.

Further, it is preferable that the second etching gas introducing means has a second gas ejection port which opens inward from an inner peripheral surface of the peripheral wall of the reaction vessel. . In this case, the introduction path of the etching gas can be provided outside the peripheral wall, and the equipment structure for keeping the introduction position of the etching gas constant can be simplified.

[0021]

(Embodiment 1) An embodiment of a method and apparatus for manufacturing a silicon carbide single crystal of the present invention will be described with reference to FIG. As shown in FIG. 1, a silicon carbide single crystal manufacturing apparatus 1 of the present embodiment includes a reaction vessel 2 having a cylindrical peripheral wall 20;
A pedestal 3 for supporting a substrate crystal 7 made of silicon carbide single crystal, which is arranged in the reaction vessel 2, and a silicon-containing gas 8 containing silicon toward the substrate crystal 7 supported on the pedestal 3.
A reaction gas supply means for supplying a carbon-containing gas 82 containing carbon 1 and carbon; and an exhaust passage 23 for discharging excess silicon-containing gas and carbon-containing gas passing between the pedestal 3 and the peripheral wall 20. Having.

Interface 3 between substrate crystal 7 and pedestal 3
A first etching gas introducing means 41 for introducing an etching gas 9 having an effect of etching silicon carbide in the vicinity of an outer periphery of silicon carbide 7, and an outer periphery of an end face 750 of a grown crystal 75 which is a silicon carbide single crystal grown on substrate crystal 7. In the vicinity, there is provided second etching gas introducing means 42 for introducing an etching gas 9 having an effect of etching silicon carbide.

The first etching gas introducing means 41 of this embodiment
Has a first gas ejection port 410 that opens outward from the outer peripheral surface 30 of the pedestal 3. 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 to this. The pedestal 3 is configured to rise as the growing crystal 75 grows. Then, the first gas outlet 410 rises as the pedestal 3 rises.

Further, the second etching gas introducing means 42 of this embodiment has a second gas outlet 420 which 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 (not shown) is connected to the etching gas introduction pipe 425 communicating with the second gas ejection port 420.

Further, in the manufacturing apparatus 1 of this embodiment, the periphery of the reaction vessel 2 is covered with a quartz tube 15, and a high-frequency coil 18 for heating is installed in a portion corresponding to the reaction vessel 2 outside thereof. I have. Then, the quartz tube 15
The silicon-containing gas 81 and the carbon-containing gas 82
A lower lid (not shown) equipped with a supply pipe for supplying
An upper lid (not shown) having an exhaust port for exhausting various gases is provided at the upper end of the quartz tube 15.

In this embodiment, as the substrate crystal 7,
A 4H-SiC single crystal substrate was used and disposed at the lower end of the pedestal 3. The silicon-containing gas 81 is SiH ₄
The gas used was C ₃ H ₈ as the carbon-containing gas 82. These gases 81 and 82 are introduced from below the reaction vessel 2 as shown in FIG. 1 to grow SiC on the substrate crystal 7.

The gas not used for the growth and the H ₂ gas generated by the decomposition of the source gas pass through the side surface of the grown crystal 75 and go to the exhaust port. Here, the manufacturing apparatus 1 of this example
Has the first etching gas introducing means 41 and the second etching means 42. Utilizing these, the etching gas 9 is introduced from the first etching gas introduction means 41 to the vicinity of the outer periphery of the boundary 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 to 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.

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. Does not change, and constant etching gas introduction can be performed. Note that the direction of introduction of the etching gas may be the center axis direction (radial direction) or the tangential direction (swirl direction).

The growth conditions in this embodiment are as follows.
500 ° C., SiH ₄ flow rate = 50-800 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 , pressure = 100
~ 400 Torr and the growth rate is 0.5 ~ 3mm /
h. The etching gas 9 is H ₂
The second etching gas introducing means 42 introduced 5 to 10 SLM, and the first etching gas introducing means 41 introduced 10 to 30 SLM.

In this example, as a result of 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. It was confirmed that it was possible. From this result, it is understood that it is very effective to perform the two-stage etching gas introduction using the two etching gas introduction units 41 and 42. The operation and effect of the two-stage etching gas introduction are considered as follows.

That is, by introducing the etching gas 9 into 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 state of the mixed gas of the surplus silicon-containing gas 81 and the carbon-containing gas 82, which still has reactivity, approaches a state where the supersaturation of silicon and carbon is high and crystal growth progresses, and the supersaturation is close to zero. As a result, the mixed gas of the surplus gas and the etching gas changes to a state that suppresses new crystal growth and also suppresses etching of the already-grown grown crystal.

Next, the mixed gas passes through the side surface of the growth crystal 75 and then passes through the boundary surface 3 between the substrate crystal 7 and the pedestal 3.
In the vicinity of the outer periphery of 7, the etching gas 9 is further mixed with the introduced etching gas 9. As a result, the mixed gas whose supersaturated state has already approached zero is changed to a sufficiently unsaturated state by the further introduced etching gas 9.
The etching gas 9 also has the ability to etch silicon carbide crystals. Therefore, the mixed gas at this stage surely suppresses the growth of new silicon carbide crystals and, even if new silicon carbide crystals are to be deposited, prevents the deposition by the etching power of the etching gas.

As described above, in the present embodiment, the introduction of the etching gas 9 in the above-mentioned two stages eliminates the supersaturation of the silicon-containing gas 81 and the carbon-containing gas 82, and
The desaturation can be performed stepwise. This gives
It is considered that the silicon carbide crystal could be prevented from being deposited on the exhaust system while the growth crystal 75 was prevented from being etched.

(Embodiment 2) In this embodiment, a manufacturing apparatus having the same structure as in Embodiment 1 is used, and HCl is used as an etching gas 9.
Only the point using was changed. Also in this case, as in the case where H ₂ was used as an 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-term growth was possible by introducing the etching gas 9 in multiple stages.

(Comparative Example) In this comparative example, the introduction of the etching gas 9 by the first etching gas introduction means 41 in the first embodiment is stopped, and the second etching gas introduction means 4
A growth experiment was conducted in the same manner as in Example 1 except that the etching gas 9 was introduced only from Step 2. As a result, in this comparative example, as the growth time progressed, Si
C was deposited and the exhaust port began to block.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a configuration of a silicon carbide single crystal manufacturing apparatus according to a first embodiment.

[Explanation of symbols]

 1. . . 14. an apparatus for producing a silicon carbide single crystal, . . 1. quartz tube, . . Reaction vessel, 20. . . Peripheral wall, 3. . . Pedestal, 41. . . First etching gas introduction means, 42. . . 6. second etching gas introduction means; . . 81. substrate crystal (seed crystal) . . Silicon-containing gas, 82. . . Carbon-containing gas, 83. . . 8. carrier gas; . . Etching gas,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daisuke Nakamura 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. 1-chome Inside Denso Corporation (72) Inventor Masaki Matsui 1-1-1 Showa-cho, Kariya City, Aichi Prefecture F-term (reference) 4G077 AA02 AA03 BE08 DB07 EG21 HA06 TB02 TB13 5F045 AA03 AB06 AC01 AC16 AD18 AE25 AF02 DP05 DQ04 EC02 EE12 EE13 EF02 EF04 EF08 EF20 EK02 EM10

Claims (7)

[Claims] A pedestal for supporting a substrate crystal made of silicon carbide single crystal is disposed in a reaction vessel having a cylindrical peripheral wall,
A silicon-containing gas containing silicon and a carbon-containing gas containing carbon are supplied to the substrate crystal supported on the pedestal to grow a silicon carbide single crystal on the substrate crystal. In the method for producing a silicon carbide single crystal for discharging surplus silicon-containing gas and carbon-containing gas after passing through a space between the substrate crystal and the vicinity of an outer periphery of a boundary surface between the substrate crystal and the pedestal, A method for producing a silicon carbide single crystal, characterized in that an etching gas having an effect of etching silicon carbide is introduced in the vicinity of the outer periphery of a growth end face of a grown crystal as a silicon carbide single crystal. 2. The method according to claim 1, wherein the etching gas is introduced by discharging the etching gas from the inside of the pedestal to the outside in the vicinity of the outer periphery of the boundary between the substrate crystal and the pedestal. A method for producing a silicon carbide single crystal. 3. The silicon carbide single crystal according to claim 1, wherein the etching gas is introduced by discharging the etching gas inward from the peripheral wall in the vicinity of the outer periphery of the end face of the grown crystal. Manufacturing method. 4. The method according to claim 1, wherein:
The method of manufacturing a silicon carbide single crystal, wherein the etching gas is a mixed gas containing one or more of hydrogen, halogen gas, and hydrogen halide. 5. A reaction vessel having a cylindrical peripheral wall, a pedestal disposed in the reaction vessel for supporting a substrate crystal made of a silicon carbide single crystal, and facing the substrate crystal supported on the pedestal. Reaction gas supply means for supplying a silicon-containing gas containing silicon and a carbon-containing gas containing carbon, and an exhaust gas passing between the pedestal and the peripheral wall to discharge excess silicon-containing gas and carbon-containing gas. A first etching gas introducing means for introducing an etching gas having an effect of etching silicon carbide in the vicinity of an outer periphery of a boundary surface between the substrate crystal and the pedestal; A second step of introducing an etching gas having an effect of etching silicon carbide into the vicinity of the outer periphery of an end face of the grown crystal which is a silicon carbide single crystal grown on the substrate crystal.
An apparatus for producing a silicon carbide single crystal, comprising: means for introducing an etching gas. 6. The method of manufacturing a silicon carbide single crystal according to claim 5, wherein said first etching gas introducing means has a first gas outlet opening outward from an outer peripheral surface of said pedestal. apparatus. 7. The second etching gas introducing means according to claim 5, wherein the second etching gas introducing means has a second gas jet opening which opens inward from an inner peripheral surface of the peripheral wall of the reaction vessel. An apparatus for producing a silicon carbide single crystal.