Silicon carbide substrate and method of growing SiC single crystal boules
The present invention relates to a silicon carbide (SiC) substrate with improved mechanical and electrical characteristics. Furthermore, the invention relates to a method for producing a bulk SiC crystal in a physical vapor transport growth system. The silicon carbide substrate comprises an inner region ( 102 ) which constitutes at least 30% of a total surface area of said substrate ( 100 ), a ring shaped peripheral region ( 104 ) radially surrounding the inner region ( 102 ), wherein a mean concentration of a dopant in the inner region ( 102 ) differs by at maximum 5·10 18 cm −3 , preferably 1·10 18 cm −3 , from the mean concentration of this dopant in the peripheral region ( 104 ).
1. Method of growing at least one SiC single crystal boule ( 108 , 109 ) in a physical vapor transport growth system, the method comprising the steps of:
arranging an SiC powder source material ( 114 ) in a source material compartment ( 116 ),
arranging at least one SiC seed crystal within a growth compartment ( 118 , 119 ), wherein said source material compartment ( 116 ) is connected to said growth compartment ( 118 , 119 ) for providing sublimated gaseous components to the growth compartment ( 118 , 119 ),
applying an elevated temperature for generating the sublimated gaseous components that generate an SiC growth phase at the SiC seed crystal, so that an SiC volume single crystal boule ( 108 , 109 ) is formed at the SiC seed crystal,
wherein the at least one growth compartment ( 118 , 119 ) comprises a dopant source and/or a dopant sink for controlling a dopant concentration in a radial direction with reference to a longitudinal axis of the single crystal boule ( 108 , 109 ) during the growth of the single crystal boule.
2. Method according to claim 1 , wherein said dopant comprises nitrogen.
3. Method according to claim 2 , wherein a peripheral region of the growing boule ( 108 , 109 ) is flushed with nitrogen and/or ammonia gas.
4. Method according to claim 1 , wherein the SiC powder source material comprises a dopant enriched material ( 126 ) in a region opposite to a peripheral region of the seed crystal.
5. Method according to claim 1 , wherein the step of arranging the SiC powder source material in the source material compartment comprises filling in a dopant enriched SiC powder source material ( 126 ) and covering a central region of an interface between the source material compartment ( 116 ) and the growth compartment ( 118 , 119 ) with a getter material.
6. Method according to claim 1 , wherein at least one SiC seed crystal is arranged within each of two growth compartments ( 118 , 119 ), wherein said source material compartment ( 116 ) is arranged symmetrically between the two growth compartments ( 118 , 119 ) and is separated from each of the growth compartments by a gas permeable porous membrane.