Method for growing single crystal silicon carbide ingot having large diameter
A method in which a carbonaceous protective film is formed on a rear surface of a single crystal SiC seed, the seed is placed in a reaction container without adhesion, and then single crystal SiC is grown from a SiC raw material on a front surface of the seed allows the seed to grow to a single crystal ingot having a large diameter since the absence of adhesion of the seed to a holder prevents the generation of warps or cracks attributed to a difference in thermal expansion coefficient between the seed and the holder during heating.
1. A process for growing a silicon carbide (SiC) single crystal ingot comprising:
(1) forming a carbonaceous protective layer on the rear side of a seed crystal of a SiC single crystal;
(2) charging a SiC raw material to a lower region of a reaction vessel and placing the seed crystal in an upper region of the reaction vessel without adhesion thereto; and
(3) growing a SiC single crystal ingot on the front side of the seed crystal from the SiC raw material,
wherein the step (1) comprises:
molding a composition that comprises a binder resin into a sheet form to prepare a protective layer;
cutting the protective layer and attaching it to the rear side of the seed crystal of a SiC single crystal by pressure thereon; and
curing and carbonizing the protective layer attached to the seed crystal to form the carbonaceous protective layer on the rear side of the seed crystal.
2. The process for growing a SiC single crystal ingot of claim 1 , wherein the composition includes in addition to the binder resin a filler, and
wherein the carbonaceous protective layer has a thickness of 5 to 1,000 μm and comprises a carbon-based filler, a metal-based filler, or a composite filler thereof in an amount of 50 to 95% by weight based on the weight of the carbonaceous protective layer.
3. The process for growing a SiC single crystal ingot of claim 1 , wherein the composition includes
a first composition and a second composition, each of which comprises the binder resin and a filler.
4. The process for growing a SiC single crystal ingot of claim 3 , wherein the first composition and the second composition are a liquid composition, the first composition has a solids content lower than that of the second composition, and
the second carbonaceous layer has an amount of a filler greater than that of the first carbonaceous layer.
5. The process for growing a SiC single crystal ingot of claim 1 , wherein in the step of preparing the protective layer, the composition is coated on both sides of a core layer composed of a fibrous material, which is then molded to a sheet form.
6. The process for growing a SiC single crystal ingot of claim 1 ,
wherein the reaction vessel is provided with a flat rack in an upper region thereof, and wherein the seed crystal is placed on the rack without adhesion thereto.
7. The process for growing a SiC single crystal ingot of claim 1 ,
wherein the reaction vessel is provided with a rack in an upper region thereof, and wherein the rack has a groove and the seed crystal is fit in the groove of the rack without adhesion thereto.
8. The process for growing a SiC single crystal ingot of claim 1 , wherein the reaction vessel is provided with a rack in an upper region thereof,
the protective layer has a diameter larger than that of the seed crystal, whereby it covers the entire rear side of the seed crystal and has a protrusion member that protrudes outward from the periphery of the seed crystal, and
the protrusion member of the protective layer is placed on the rack without adhesion thereto for placing the seed crystal.
9. The process for growing a SiC single crystal ingot of claim 1 , wherein the reaction vessel has a structure in which the upper region is open, and the reaction vessel is closed by the seed crystal placed in the upper region of the reaction vessel.