Method for silicon carbide crystal growth by reacting elemental silicon vapor with a porous carbon solid source material
View Patent ↗In a method for growing bulk SiC single crystals using chemical vapor transport, wherein silicon acts as a chemical transport agent for carbon, a growth crucible is charged with a solid carbon source material and a SiC single crystal seed disposed therein in spaced relationship. A halosilane gas, such as SiCl 4 and a reducing gas, such as H 2 , are introduced into the crucible via separate inlets and mix in the crucible interior. The crucible is heated in a manner that encourages chemical reaction between the halosilane gas and the reducing gas leading to the chemical reduction of the halosilane gas to elemental silicon (Si) vapor. The produced Si vapor is transported to the solid carbon source material where it reacts with the solid carbon source material yielding volatile Si-bearing and C-bearing molecules. The produced Si-bearing and C-bearing vapors are transported to the SiC single crystal seed and precipitate on the SiC single crystal seed causing growth of a SiC single crystal on the SiC single crystal seed.
1. A method for SiC crystal growth by chemical vapor transport with silicon comprising:
(a) providing a SiC growth system that includes a silicon carbide seed crystal and solid carbon source material positioned in spaced relation;
(b) heating the SiC growth system and introducing into the SiC growth system a gaseous halosilane and a reducing gas, wherein the gaseous halosilane and the reducing gas react in the SiC growth system yielding elemental silicon vapor;
(c) reacting the elemental silicon vapor of step (b) with the solid carbon source material of step (a) yielding silicon-bearing and carbon-bearing vapors;
(d) transporting the silicon-bearing and carbon-bearing vapors of step (c) to the SiC seed of step (a); and
(e) precipitating the silicon-bearing and carbon-bearing vapors of step (c) on the SiC seed of step (a) to grow the silicon carbide single crystal, wherein:
the solid carbon source material is comprised of porous carbon in a form of one or more of pellets, spheres, and granules having at least one of the following:
a mean grain size of between 0.5 mm and 6 mm;
a density between 0.4 g/cm 3 and 1.0 g/cm 3 ; and
a surface area between 200 m 2 /g and 2000 m 2 /g.
2. The method of claim 1 , wherein the halosilane gas and the reducing gas are separately introduced into the SiC growth system.
3. The method of claim 1 , wherein reaction between the gaseous halosilane and the reducing gas of step (b) occurs in a reaction zone that exists on a side of the solid carbon source material opposite the silicon carbide seed crystal.
4. The method of claim 1 , wherein the SiC growth system is heated such that a temperature gradient forms where the silicon carbide seed crystal is at a lower temperature than the solid carbon source material.
5. The method of claim 1 , wherein:
the SiC growth system includes a growth crucible;
all of the solid carbon source material is positioned in spaced relation between the ends of the growth crucible; and
the silicon carbide seed crystal is positioned on one end of the growth crucible.
6. The method of claim 5 , wherein:
the growth crucible includes one or more gas inlets for introducing the gaseous halosilane and the reducing gas into an end of the growth crucible opposite the silicon carbide seed crystal; and
the growth crucible includes one or more gas outlets.
7. The method of claim 6 , wherein gaseous byproducts of steps (b, c and e) exit the growth crucible via the one or more gas outlets.
8. The method of claim 5 , wherein:
the growth crucible includes a perforated plate supporting all of the solid carbon source material in spaced relation to an end of the growth crucible opposite the silicon carbide seed crystal; and
the space between the perforated plate and the end of the growth crucible opposite the silicon carbide seed crystal defines a reaction zone where step (b) occurs.
9. The method of claim 8 , wherein heating occurs such that a temperature gradient forms where the silicon carbide seed crystal is at a lower temperature than the carbon source material.
10. The method of claim 8 , wherein the growth crucible and the perforated plate are made from a material that is substantially stable against erosion by Si vapor at SiC crystal growth temperatures.
11. The method of claim 10 , wherein the growth crucible and the perforated plate are made from graphite.
12. The method of claim 1 , wherein:
the reducing gas is hydrogen;
the halosilane gas is SiCl 4 ; or
the reducing gas is hydrogen and the halosilane gas is SiCl 4.
13. The method of claim 1 , wherein the silicon carbide seed crystal is a 4H, 6H, or 3C polytype.
14. The method of claim 1 , further including introducing a nitrogen containing gas into the SiC growth system to grow an n-type silicon carbide single crystal.
15. The method of claim 1 , further including introducing a gaseous aluminum precursor into the SiC growth system to grow a p-type silicon carbide single crystal.
16. The method of claim 1 , further including introducing a gaseous vanadium precursor into the SiC growth system to grow a vanadium-doped, semi-insulating silicon carbide single crystal.