Apparatus for producing silicon carbide crystal
An apparatus for producing silicon carbide crystal is provided and includes a composite structure formed by a plurality of graphite layers and silicon carbide seed crystals, wherein a density or thickness of each layer of graphite is gradually adjusted to reduce a difference of a thermal expansion coefficient and Young's modulus between the graphite layers and silicon carbide. The composite structure can be stabilized on a top portion or an upper cover of a crucible made of graphite, thereby preventing the silicon carbide crystal from falling off.
1 . An apparatus for producing silicon carbide crystal, comprising:
a crucible comprising a top portion and a bottom portion, wherein the bottom portion comprising silicon carbide powder;
an upper cover positioned on the top portion and defining a reaction space with the crucible; and
a composite structure comprising a plurality of graphite layers and a silicon carbide seed crystal, wherein the silicon carbide seed crystal is positioned inside the upper cover through the graphite layers, edges of the graphite layers comprise a thread structure, and the thread structure is fixed to the upper cover.
2 . The apparatus for producing silicon carbide crystal of claim 1 , wherein the graphite layers, the silicon carbide seed crystal, and the upper cover are bonded with each other by an adhesive having a carbon content of 1-40 wt %.
3 . The apparatus for producing silicon carbide crystal of claim 2 , wherein the carbon content of the adhesive gradually increases in a direction from the upper cover to the silicon carbide seed crystal.
4 . The apparatus for producing silicon carbide crystal of claim 1 further comprises a supporting member disposed on the top portion and inside the upper cover, thereby fixing the composite structure.
5 . The apparatus for producing silicon carbide crystal of claim 4 , wherein edges of the graphite layers are bonded to the supporting member by an adhesive having a carbon content of 1-40 wt %.
6 . The apparatus for producing silicon carbide crystal of claim 4 , wherein edges of the graphite layers comprise a thread structure, wherein the thread structure is fixed to the supporting member.
7 . The apparatus for producing silicon carbide crystal of claim 1 , wherein among the graphite layers, an area of the graphite layer contacting the upper cover is greater than that of the other graphite layers.
8 . The apparatus for producing silicon carbide crystal of claim 1 , wherein among the graphite layers, a thermal expansion coefficient of the graphite layer contacting the silicon carbide seed crystal is greater than that of the other graphite layers and is approximate to a thermal expansion coefficient of the silicon carbide seed crystal.
9 . The apparatus for producing silicon carbide crystal of claim 1 , wherein the crucible is made of graphite.