Physical vapor transport growth system for simultaneously growing more than one SiC single crystal and method of growing
The present invention relates to a configuration and in particular a physical vapor transport growth system for simultaneously growing more than one silicon carbide (SiC) bulk crystal. Furthermore, the invention relates to a method for producing such a bulk SiC crystal. A physical vapor transport growth system for simultaneously growing more than one SiC single crystal boule comprises a crucible containing two growth compartments for arranging at least one SiC seed crystal in each of them, and a source material compartment for containing a SiC source material, wherein said source material compartment is arranged symmetrically between said growth compartments and is separated from each of the growth compartments by a gas permeable porous membrane.
1. A physical vapor transport growth system for simultaneously growing more than one silicon carbide single crystal boule, said system comprising:
a crucible containing two growth compartments for arranging at least one silicon carbide seed crystal in each of them, and a source material compartment for containing a silicon carbide source material;
wherein said source material compartment is arranged symmetrically between said growth compartments and is separated from each of the growth compartments by gas permeable porous membranes, at least one of the gas permeable porous membranes having a cross-sectional geometry with a step forming a terrace.
2. The system according to claim 1 , wherein the gas permeable porous membranes comprise graphite, tantalum carbide, or tantalum.
3. The system according to claim 1 , wherein said source material compartment is formed to receive silicon carbide powder.
4. The system according to claim 1 , wherein the gas permeable porous membranes have a density of 0.8 g·cm-3 to 1.6 g·cm-3.
5. The system according to claim 4 , wherein the gas permeable porous membranes have a density of 1.2 g·cm-3.
6. The system according to claim 1 , wherein the gas permeable porous membranes have a thickness of 1 mm to 5 mm.
7. The system according to claim 6 , wherein the gas permeable porous membranes have a thickness of 2 mm.
8. The system according to claim 1 , wherein at least one of the gas permeable porous membranes has a plateau-shaped inner region which is arranged in a distance from a plane in which the seed crystal is arranged, which is larger than the distance of a peripheral region of the membrane from said plane.
9. The system according to claim 1 , wherein the outer diameter of the gas permeable porous membranes measure no more than 120% of an outer diameter of said silicon carbide seed crystals.
10. The system according to claim 9 , wherein the surface of the gas permeable porous membranes are more than twice the surface of the seed crystals.
11. The system according to claim 1 , wherein the distance between the two seed crystals is between 250 mm to 350 mm.
12. The system according to claim 1 , wherein the distance between the two seed crystals is 300 mm.
13. A method for simultaneously growing at least two silicon carbide singe crystal boules in a physical vapor transport growth system, the method comprising the steps of:
arranging a silicon carbide powder source material in a source material compartment;
arranging at least one silicon carbide seed crystal within each of two growth compartments, wherein said source material compartment is arranged symmetrically between said growth compartments and is separated from each of the growth compartments by gas permeable porous membranes, at least one of the gas permeable porous membranes having a cross-sectional geometry with a step forming a terrace; and
applying an elevated temperature which has profile being symmetric with respect to a longitudinal axis of the physical vapor transport growth system.
14. The method according to claim 13 , wherein the temperature difference between the centre of the source material compartment and a surface of the silicon carbide seed crystals is between 100 K to 300 K.
15. The method according to claim 13 , wherein the temperature difference between the centre of the source material compartment and a surface of the silicon carbide seed crystals is 200 K.
16. The method according to claim 13 , wherein a longitudinal middle axis of the system is oriented in a vertical direction, so that in one of the growth compartments, a silicon carbide single crystal grows against the direction of gravity, and in the other of the growth compartments, a silicon carbide single crystal grows in the direction of gravity.
17. The method according to claim 13 , wherein a longitudinal middle axis of the system is oriented in horizontal direction, so that the single crystals in both growth compartments grow in a direction across to the direction of gravity.