JP3658832B2 - Silicon carbide single crystal manufacturing apparatus and silicon carbide single crystal manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for producing a silicon carbide single crystal that keeps the polymorph of a silicon carbide single crystal ingot grown on a silicon carbide single crystal substrate (seed crystal) constant, and the polymorph of the silicon carbide single crystal ingot is a 4H type. Or it is related with the manufacturing method of the silicon carbide single crystal which can be grown to 6H type.
[0002]
[Prior art]
Conventionally, for example, a silicon carbide single crystal substrate has been manufactured as a semiconductor substrate used in a high-voltage high-power semiconductor device such as a high-voltage power transistor or a high-voltage diode. Known methods for producing this silicon carbide single crystal substrate include the Atchison method, the Rayleigh method, the sublimation recrystallization method (improved Rayleigh method), and the like. Among these, as a method for manufacturing a semiconductor substrate, a sublimation recrystallization method that is advantageous for growing a large-area, high-quality silicon carbide single crystal crystal is mainly employed.
[0003]
This sublimation recrystallization method is disclosed in Japanese Patent Publication No. 63-57400. A silicon carbide raw material powder 2 placed in a graphite crucible 1 is heated and sublimated with an induction coil 7, and the graphite crucible 1 In this method, silicon carbide single crystal 4 is grown on the surface of silicon carbide seed crystal 3 made of silicon carbide single crystal arranged to face the surface of silicon carbide raw material powder 2. By this method, the obtained silicon carbide single crystal 4 is supplied as a large-area and polymorph-controlled substrate suitable for use in a semiconductor substrate.
[0004]
Further, if necessary, a silicon carbide single crystal layer having a conductivity type or a carrier concentration different from that of the substrate is grown on the silicon carbide single crystal substrate by liquid phase epitaxial method (LPE) or vapor phase epitaxial method (CVD). Thus, a semiconductor element manufacturing substrate is manufactured.
[0005]
Silicon carbide has many polymorphs with different crystal structures, and is divided into α-type and β-type. Of these, the α type has a crystal structure belonging to the hexagonal system and the rhombohedral system, and the hexagonal system generally has a 6H type, 4H type, and the like due to the difference in the number of periods of atomic plane stacking. There is what is called. Similarly, there are rhombohedral crystal systems called 15R type and 21R type.
The β type has a crystal structure belonging to a cubic system, and only the 3C type exists.
[0006]
[Problems to be solved by the invention]
In the prior art described above, the electrical characteristics of the silicon carbide single crystal substrate vary depending on these polymorphs, and the polymorph type of the silicon carbide single crystal substrate is selected according to the type of semiconductor device to be manufactured. In particular, a silicon carbide single crystal substrate having an α type (6H type, 4H type) polymorph is suitable for improving the characteristics of a semiconductor device for high voltage and high power, and an α type polymorph having a large diameter and a high quality. It is desired that a silicon carbide single crystal substrate having a large amount is supplied at a low cost.
[0007]
However, Japanese Patent Publication No. 6-39360 discloses a 6H type or a 4H type by limiting the plane orientation and plane polarity of the silicon carbide single crystal and limiting the growth conditions of the silicon carbide single crystal, that is, the temperature, temperature gradient, and growth rate. In this method, a silicon carbide single crystal having a desired crystal structure can be produced, but all of the silicon carbide single crystal ingots in the growth plane and in the growth direction are identical. It is difficult to shape.
[0008]
Further, even in the growth method disclosed in Japanese Patent Laid-Open No. 2-48495, it is difficult to make all the silicon carbide single crystal ingots in the growth plane and the growth direction into the same polymorph.
[0009]
Therefore, the silicon carbide single crystal ingot grown by the conventional technique has a problem that 6H type, 4H type, 15R type and 3C type polymorphs are mixed in the growth plane and the growth direction.
[0010]
Accordingly, an object of the present invention is to provide a silicon carbide single crystal manufacturing apparatus and a 4H type or 6H type silicon carbide single crystal manufacturing method for efficiently manufacturing a silicon carbide single crystal ingot having the same polymorph. To do.
[0011]
[Means for Solving the Problems]
With the above configuration,
(1) In a silicon carbide single crystal manufacturing apparatus in which a silicon carbide raw material powder is heated and sublimated in an inert gas atmosphere to grow a silicon carbide single crystal, the silicon carbide raw material is charged and sublimated from the silicon carbide raw material by heating. A crucible that generates gas and has an opening formed in the center of the bottom; a support shaft that can be inserted into the opening from the outside into the crucible; and a shielding plate provided on the top of the support shaft; An upper lid mounted on the upper part of the crucible above the shielding plate, and attached to the crucible and a silicon carbide single crystal substrate (seed crystal) having a temperature slightly lower than that of the shielding plate, facing the shielding plate in parallel. And an apparatus for manufacturing a silicon carbide single crystal, which includes a vertical drive device that enables the support shaft and the shielding plate to move up and down simultaneously.
[0012]
Therefore, according to the item (1), during the growth of the silicon carbide single crystal, the shielding plate always faces the silicon carbide single crystal growth surface at a constant interval, and the temperature difference between the crystal growth surface and the shielding plate is kept constant. Therefore, the temperature of the crystal growth surface is uniformly maintained at a constant temperature, and a silicon carbide single crystal ingot having the same polymorph can be efficiently manufactured.
[0013]
(2) Provided is an apparatus for producing a silicon carbide single crystal in which the vertical drive device described in (1) above drives the shield plate and the support shaft at a speed of 0.1 to 1.5 mm / h. Therefore, according to the item (2), a silicon carbide single crystal ingot having the same polymorph can be efficiently produced.
[0014]
(3) The silicon carbide single crystal manufacturing apparatus according to (1) described above is arranged in parallel with a silicon carbide single crystal plane grown on a silicon carbide single crystal substrate placed in the crucible. Provided is a method for producing a silicon carbide single crystal in which a silicon carbide single crystal is grown while being moved so as to maintain a constant distance from a shielding plate.
[0015]
Therefore, according to the item (3), the distance between the shielding plate and the surface of the silicon carbide single crystal ingot grown on the silicon carbide single crystal substrate (seed crystal) is kept constant during the growth of the silicon carbide single crystal ingot. Thus, the temperature change of the growth surface is eliminated, and a silicon carbide single crystal ingot having the same polymorph can be efficiently manufactured.
[0016]
(4) 4H type silicon carbide by setting the plane orientation of the silicon carbide single crystal substrate surface to (0001) carbon plane and the distance between the shielding plate and the silicon carbide single crystal surface to 0.2 to 15 mm. The method for producing a silicon carbide single crystal as described in (3) above, wherein the single crystal is grown.
[0017]
Therefore, according to the item (4), a 4H type silicon carbide single crystal ingot can be efficiently manufactured.
(5) The plane orientation of the silicon carbide single crystal substrate surface and (0001) coal sober, and, by the 15~50mm the distance between the shielding plate and the surface of single-crystal silicon carbide, 6H-type silicon carbide single crystal A method for producing a silicon carbide single crystal as described in (3) above is provided.
[0018]
Therefore, according to the item (5), a 6H type silicon carbide single crystal ingot can be efficiently manufactured.
(6) The plane orientation of the silicon carbide single crystal substrate surface and (0001) silicofluoride sober, and, by the distance between the shielding plate and the silicon carbide single crystal surface and 0.2～50Mm, 6H-type silicon carbide The method for producing a silicon carbide single crystal as described in (3) above, wherein the single crystal is grown.
[0019]
Therefore, according to the item (6), a 6H-type silicon carbide single crystal ingot can be efficiently manufactured.
(7) In the method of growing the silicon carbide single crystal,
The silicon carbide single crystal according to (3), wherein the silicon carbide raw material temperature is 2300 ° C. to 2350 ° C., the silicon carbide single crystal substrate temperature is 2200 ° C. to 2300 ° C., and the pressure in the crystal manufacturing apparatus is 0.1 to 10 Torr. A manufacturing method is provided.
[0020]
Therefore, according to the item (7), in the method of growing a silicon carbide single crystal, the silicon carbide raw material temperature is set to 2300 ° C. to 2350 ° C., the silicon carbide single crystal substrate temperature is set to 2200 ° C. to 2300 ° C. By setting the pressure to 0.1 to 10 Torr, it is possible to efficiently produce a silicon carbide single crystal ingot having the same polymorph and a high growth rate.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 illustrates a cross-sectional view of a silicon carbide single crystal manufacturing apparatus as an embodiment according to the present invention.
[0022]
This silicon carbide single crystal manufacturing apparatus 13 includes a graphite crucible 1 having a bottom filled with silicon carbide raw material powder 2 in a donut shape, and an opening 12 formed in the center of the bottom, and the center of the graphite crucible 1 A support shaft 10 that can be inserted into the graphite crucible 1 from the outside through an opening 12 provided in the section, a shielding plate 9 disposed on the top of the support shaft 10, and above the shielding plate 9. A graphite product that is mounted on the upper portion of the graphite crucible 1 and can be attached to a substantially central portion of a silicon carbide single crystal substrate (seed crystal) 3 that maintains a temperature slightly lower than the temperature of the graphite crucible 1 and the shielding plate 9. Inductive heating of the upper lid 5, the support shaft 10 and the shielding plate 9 at the same time, the vertical drive device 11 capable of fine movement in the vertical direction at a drive speed of 0.1 to 1.5 mm / h, and the graphite crucible 1. Induction coil 7 and graphite crucible 1 covering the outside and heat shielding And a vacuum vessel 8 that accommodates all of these members, and further attached to the side of the vacuum vessel 8 and a vacuum exhaust device that can exhaust the inside of the vacuum vessel 8 to a high vacuum (not shown). An inert gas introduction pipe is provided.
[0023]
Next, FIG. 2 shows a configuration example of the vertical drive device 11 and its operation will be described in detail.
In the vertical drive device 11, the CPU 21 centrally manages each component and controls the moving distance and moving speed of the support shaft 10. As the mechanism for driving the spindle rod 10 up and down, two systems are provided, one of which is for driving the shielding plate 9 up and down during the growth of the single crystal. The other is a system capable of finely driving 1.5 mm / h, and the other is for adjusting the position of the shielding plate 9 to the initial setting position. The spindle 10 is driven at a high speed of 1 to 10 mm / sec. It is a system that can be driven. Each system will be briefly described.
[0024]
The fine movement drive system controls the control device 20 based on predetermined execution items instructed by the CPU 21 and is transmitted to the drive device 19 composed of, for example, a servo motor. The drive device 19 drives the gear 16 to rotate. The power accompanying the rotation of the gear 16 is transmitted to the lifting device 22 to drive the support shaft 10 up and down.
[0025]
On the other hand, in the high-speed drive system, similarly to the former, the control device 20 is controlled based on the execution item instructed by the CPU 21 and transmitted to the drive device 18 composed of, for example, a servo motor. The gear 17 is rotated by driving of the driving device 18. The power accompanying the rotation of the gear 17 is transmitted to the lifting device 23 to drive the support shaft 10 up and down.
[0026]
Detection of the moving distance and moving speed of the spindle 10 at the time of driving is detected by the position detectors 14 and 15, and the control device 20 is based on the detected information, and the fine driving driving device 19 and the high speed driving driving device. 18 is controlled.
[0027]
As a method for adjusting the position of the shielding plate 9 shown in FIG. 1, the thickness of the seed crystal 3 is measured by a length measuring device (for example, a micrometer). The measured result is input to the CPU 21. Further, the distance between the shielding plate 9 and the surface of the seed crystal 3 is input to the CPU 21. Thereafter, by executing the execution item, the control device 20 controls the high-speed drive mechanism system, rotates the gear 17 to the drive device 18, and lifts and lowers the support device 10 so that the spindle 10 faces the seed crystal 3. The position of the shielding plate 9 is adjusted by driving in the direction while confirming the moving distance by the position detector 14.
[0028]
FIG. 3 is a diagram showing a position adjustment value of the shielding plate 9 for growing the 4H type and 6H type silicon carbide single crystals. Shielding plate 9 is a disk made of graphite and having a diameter larger than that of silicon carbide single crystal substrate (seed crystal) 3.
[0029]
Next, the growth of a silicon carbide single crystal using such a silicon carbide single crystal manufacturing apparatus 13 will be described.
First, the doughnut-shaped space of the graphite crucible 1 is filled with an amount of silicon carbide raw material powder 2 corresponding to the growth time. For example, in the case of growth for 5 hours, about 100 g is filled. In this embodiment, this silicon carbide raw material powder 2 is used by heat-treating in advance in a vacuum at 1800 to 2000 ° C. having an average particle diameter of 500 μm that is commercially available as an abrasive. Of course, it is not limited to this.
[0030]
Next, a silicon carbide single crystal substrate (seed crystal) 3 is attached to a substantially central portion of the graphite upper lid 5. The plane orientation of the seed crystal 3 is a (0001) carbon plane. The graphite upper lid 5 is placed on the upper part of the graphite crucible 1 so that the attached seed crystal 3 faces the silicon carbide powder 2.
[0031]
And the upper part of the heat insulating material 6 is attached, and the inside of the vacuum vessel 8 is evacuated by a vacuum evacuation device (not shown) to a high vacuum of 1 × 10 ⁻³ to 10 ⁻⁴ Torr. It is desirable that the ultimate vacuum in the present embodiment is as high as possible. Thereafter, argon gas is introduced into the vacuum vessel 8 to form an argon gas atmosphere, the graphite crucible 1 is heated by the induction coil 7, the temperature of the graphite crucible 1 is set to 2300 to 2350 ° C., and the silicon carbide raw material powder 2 To sublimation temperature.
[0032]
The temperature of the seed crystal 3 at this time is lower than the temperature of the silicon carbide raw material powder 2 by 50 to 150 ° C. due to the relative positional relationship between the graphite crucible 1 and the induction coil 7, and is 2200 to 2300 ° C. . However, when the temperature of the silicon carbide raw material powder 2 is higher than 2350 ° C., the amount of sublimation of the raw material increases, so that the growth rate increases and polycrystallization becomes easy. On the other hand, when the temperature is lower than 2300 ° C., the amount of sublimation of the raw material is reduced, so that the growth rate is reduced and the productivity is deteriorated.
[0033]
And after the temperature of the silicon carbide raw material powder 2 and the seed crystal 3 is stabilized, the vacuum vessel 8 is decompressed by a vacuum exhaust device (not shown). Sublimation starts from the silicon carbide raw material powder 2 under reduced pressure, and crystal growth starts.
[0034]
At this time, the pressure at which the degree of vacuum is reduced to 0.1 to 10 Torr is defined as the growth pressure. During crystal growth, argon gas is flowed at 10 liters / min, and the pressure is controlled by adjusting a valve of an evacuation device (not shown). Here, when the pressure is higher than 10 Torr, the sublimation amount of the raw material is small, the growth rate is low, and the productivity is deteriorated. On the other hand, when the pressure is lower than 0.1 Torr, the amount of sublimation of the raw material is large, the growth rate is increased, and polycrystallization is facilitated.
[0035]
Then, the gas sublimated from the silicon carbide raw material powder 2 reaches the seed crystal 3 using the temperature difference from the seed crystal 3 as a driving force, and crystal growth proceeds.
Next, simultaneously with the start of crystal growth, the support shaft 10 and the shielding plate 9 disposed on the uppermost portion of the support shaft 10 are simultaneously connected to the seed crystal 3 by the vertical drive device 11 at a speed equivalent to the crystal growth speed. By driving in the opposite direction, crystals are grown while keeping the distance between the shielding plate 9 and the growth surface of the silicon carbide single crystal ingot 4 constant.
[0036]
The crystal growth rate depends on the growth conditions such as the temperature of the silicon carbide raw material powder 2, the temperature of the silicon carbide single crystal substrate (seed crystal) 3, the pressure in the crystal manufacturing apparatus, and the distance between the shielding plate 9 and the silicon carbide single crystal ingot 4. However, the relationship between the crystal growth rate and these growth conditions is obtained in advance by a growth experiment, and information on these growth conditions is stored in the CPU 21.
[0037]
Next, when the growth conditions are input to the CPU 21, the CPU 21 calculates the crystal growth rate. Based on the control signal from the CPU 21 based on the calculated crystal growth rate, the control device 20 controls the drive device 19. By driving the driving device 19, the gear 16 is rotated and transmitted to the lifting device 22 to drive the support shaft 10 in a direction facing the seed crystal 3. That is, the fine movement drive mechanism system is operated. As for the moving speed at that time, detection signals from the position detector 14 and the position detector 15 are transmitted to the control device 20, and the operation of the driving device 19 is controlled.
[0038]
The reason why the crystal polymorph changes during crystal growth is estimated as follows. The crystal polymorph changes depending on, for example, the temperature of the silicon carbide raw material powder 2, the temperature of the seed crystal 3 disposed at the substantially central portion of the graphite upper lid 5, and the temperature of the shielding plate 9 disposed at the uppermost portion of the support shaft 10. . In particular, the polymorph is greatly influenced by the temperature difference between the seed crystal 3 and the shielding plate 9. When the shielding plate 9 is fixed, the growth surface of the silicon carbide single crystal ingot 4 approaches the shielding plate 9 together with the growth during the single crystal growth, and the growth surface of the silicon carbide single crystal ingot 4 and the shielding plate 9 The distance of changes.
[0039]
If the distance changes, the temperature of the growth surface of silicon carbide single crystal ingot 4 and the temperature difference between the growth surface of silicon carbide single crystal ingot 4 and shielding plate 9 change. If the temperature of the growth surface of the silicon carbide single crystal ingot 4 and the temperature difference change, the polymorph changes.
[0040]
Therefore, the method described above during crystal growth, that is, during the crystal growth, the distance between the shielding plate 9 and the growth surface of the silicon carbide single crystal ingot 4 is always kept constant, so that the growth surface of the silicon carbide single crystal ingot 4 is maintained. As a result, the temperature of the growth surface is kept constant and the polymorph of the silicon carbide single crystal ingot 4 can be grown constantly.
[0041]
In the present embodiment, the plane orientation of the surface of the seed crystal 3 is a (0001) carbon plane, and the distance between the shielding plate 9 and the surface of the silicon carbide single crystal ingot 4 is kept constant at 0.2 to 15 mm.
[0042]
And after making it grow over 5 hours, while introducing argon gas into the vacuum vessel 8, the electric power supply to the induction coil 7 is stopped, temperature is lowered | hung, and it complete | finishes growth.
The silicon carbide single crystal ingot 4 is removed from the graphite upper lid 5, and the obtained crystal is sliced and formed on a semiconductor substrate. When the polymorph of this semiconductor substrate was measured by Raman spectroscopy, it was a 4H uniform polymorph both in the substrate plane and in the substrate cross-sectional direction. This semiconductor substrate is suitable for a semiconductor device such as a high power vertical MOSFET, a pn diode, and a Schottky diode.
[0043]
In the present embodiment, a silicon carbide single crystal that makes a polymorph constant is produced by an up-and-down drive device 11 that simultaneously drives an up-and-down drive of a support shaft 10 and a shielding plate 9 disposed on the uppermost portion of the support shaft 10. However, even when the shielding plate 9 is fixed and the seed crystal 3 side is driven up and down by the up-and-down driving device 11, it is considered that the polymorph can be made equal. That is, if the distance between the shielding plate 9 and the surface of the silicon carbide single crystal ingot 4 according to the present invention is kept constant during crystal growth, the polymorph can be made constant.
[0044]
Next, a modified example of the above-described embodiment will be described.
In the above-described embodiment, the surface orientation of the seed crystal 3 is a (0001) carbon plane, and the distance between the shielding plate 9 and the surface of the silicon carbide single crystal ingot 4 is 0.2 to 15 mm. A 6H type silicon carbide single crystal ingot can be grown by changing the distance to 15 to 50 mm.
[0045]
Further, the surface orientation of the seed crystal 3 is a (0001) silicon surface, and the distance between the shielding plate 9 and the surface of the silicon carbide single crystal ingot 4 is 0.2 to 50 mm, so that 6H type silicon carbide is obtained. Single crystal ingots can be grown.
[0046]
【The invention's effect】
As described above in detail, according to the present invention, the polymorphism in the growth plane and in the growth direction of the silicon carbide single crystal grown on the silicon carbide substrate (seed crystal) can always be made constant.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a silicon carbide single crystal manufacturing apparatus as an embodiment according to the present invention.
FIG. 2 is a diagram illustrating a configuration example of a vertical driving device illustrated in FIG.
FIG. 3 is a diagram showing a position adjustment value of a shielding plate for growing 4H-type and 6H-type silicon carbide single crystals.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Graphite crucible 2 ... Silicon carbide raw material powder 3 ... Silicon carbide single crystal substrate (seed crystal)
4 ... Silicon carbide single crystal ingot 5 ... Graphite top cover 6 ... Heat insulating material 7 ... Insulating coil 8 ... Vacuum vessel 9 ... Shield plate 10 ... Spindle shaft 11 ... Vertical drive device (servo motor)
DESCRIPTION OF SYMBOLS 12 ... Hole 13 ... Silicon carbide single crystal manufacturing apparatus 14, 15 ... Position detector 16, 17 ... Gear,
18, 19 ... Drive device (servo motor)
20 ... Control device 21 ... CPU
22, 23 ... Lifting device (rack & pinion)

Claims (7)

In a silicon carbide single crystal manufacturing apparatus for heating and sublimating a silicon carbide raw material powder in an inert gas atmosphere to grow a silicon carbide single crystal,
A crucible filled with the silicon carbide raw material and generating a sublimation gas from the silicon carbide raw material by heating;
A support shaft that can be inserted into the crucible from the outside in the central hole;
A silicon carbide single crystal substrate that is placed on the upper part of the crucible above the shielding plate and that can be maintained at a temperature lower than the temperature of the crucible and the shielding plate. An upper lid that can be mounted in parallel with the shielding plate;
An up-and-down drive device capable of simultaneously moving up and down the support shaft and the shielding plate;
An apparatus for producing a silicon carbide single crystal, comprising: 2. The silicon carbide single crystal manufacturing apparatus according to claim 1, wherein the vertical driving device drives the shielding plate and the support shaft vertically at a speed of 0.1 to 1.5 mm / h. 3. In the manufacturing method of the silicon carbide single crystal by the manufacturing apparatus of the silicon carbide single crystal of Claim 1,
While moving so that the distance between the silicon carbide single crystal surface grown on the silicon carbide single crystal substrate placed in the crucible and the shielding plate facing in parallel is kept constant, the silicon carbide single crystal A method for producing a silicon carbide single crystal, characterized in that a silicon carbide single crystal is grown without temperature change of a growth surface. By setting the plane orientation of the silicon carbide single crystal substrate surface to a (0001) carbon plane and the distance between the shielding plate and the silicon carbide single crystal surface to 0.2 to 15 mm, a 4H type silicon carbide single crystal is obtained. 4. The method for producing a silicon carbide single crystal according to claim 3, wherein the growth is performed. A 6H type silicon carbide single crystal is grown by setting the plane orientation of the silicon carbide single crystal substrate surface to a (0001) carbon plane and the distance between the shielding plate and the silicon carbide single crystal surface to 15 to 50 mm. The method for producing a silicon carbide single crystal according to claim 3. By setting the plane orientation of the silicon carbide single crystal substrate surface to a (0001) silicon surface and the distance between the shielding plate and the silicon carbide single crystal surface to 0.2 to 50 mm, a 6H type silicon carbide single crystal is obtained. 4. The method for producing a silicon carbide single crystal according to claim 3, wherein the growth is performed. In the method of growing the silicon carbide single crystal,
The silicon carbide raw material temperature is 2300 ° C to 2350 ° C, the silicon carbide single crystal substrate temperature is 2200 ° C to 2300 ° C, and the pressure in the crystal manufacturing apparatus is 0.1 to 10 Torr. A method for producing a silicon carbide single crystal.

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