Silicon carbide substrate, semiconductor device, wiring substrate, and silicon carbide manufacturing method
A silicon carbide substrate has a high-frequency loss equal to or less than 2.0 dB/mm at 20 GHz is effective to mount and operate electronic components. The silicon carbide substrate is heated at 2000° C. or more to be reduced to the high-frequency loss equal to 2.0 dB/mm or less at 20 GHz. Moreover, manufacturing the silicon carbide substrate by CVD without flowing nitrogen into a heater enables the high-frequency loss to be reduced to 2.0 dB/mm or less.
1. A silicon carbide substrate manufacturing method comprising:
preparing a preliminary silicon carbide substrate that is formed by chemical vapor deposition (CVD) and that has an RF loss higher than 2 dB/mm at a frequency of 20 GHz, when the RF loss is represented by an operation transmission matrix (S21) of signal passage characteristics; and
heating the preliminary CVDed silicon carbide substrate in a noble gas atmosphere at a temperature between 2000° C. and 2300° C. to reduce the RF loss equal to or less than 2 dB/mm; and
wherein:
the preliminary CVDed silicon substrate is heated under a nitrogen atmosphere to a temperature lower than 2000° C. and then heated to a temperature between 2000° C. and 2300° C. under the noble gas atmosphere.
2. The silicon carbide substrate manufacturing method claimed in claim 1 , wherein the CVD is performed by the use of a CVD apparatus having a heater unit and the preliminary CVDed silicon carbide substrate is formed by the CVD in a state of flowing nitrogen into the heater unit or without flowing nitrogen into the heater unit.
3. The silicon carbide substrate manufacturing method claimed in claim 1 , wherein the preliminary CVDed silicon carbide substrate is heated to a temperature of 800° C. which is lower than 2000° C. and then heated to the temperature between 2000° C. and 2300° C.