Microhardness of 6H- and 4H-SiC Substrates

Knoop microhardness assessments were conducted on a variety of 6H- and 4H-SiC substrates to assess any appreciable differences that may need to be considered in wafer manufacture and general application. Nitrogen-doped, vanadium-doped and unintentionally doped (UID) substrates with both on-axis and 8 degrees off-axis orientations were assessed. In general, the Knoop hardness values fell in the 2000 to 2500 kg/mm(2) range (equivalent to approximately 20 to 25 GPa). Hardness values measured in the < 1100 > crystal direction were significantly higher than in the < 11-20 > direction. Undoped and vanadium-doped samples were harder than nitrogen-doped samples. For both 6H and 4H nitrogen-doped samples, the hardness was as much as 10% higher for 8 degrees offcut wafers than for on-axis.