Radio frequency bias power effect on surface roughness of silicon carbide plasma etching

Control of surface roughness of silicon carbide (SiC) is to maintain or improve the electrical stability of high-power devices. The bias power plays an important role in determining the surface roughness. The surface roughness of SiC films etched in a C2F6 inductively coupled plasma is investigated in two ways: a variation in the bias power at fixed plasma conditions; and a shift in process parameters including radio frequency (rf) source power, pressure, O2 fraction, and gap between the wafer and plasma source. The surface roughness was measured by an atomic force microscopy (AFM). Parameter-induced DC bias was also correlated to the surface roughness. Under high pressure, the surface roughness was strongly correlated to the bias power-induced DC bias for the variation in the source power or the gap. Depending on the pressure, a significant discrepancy in the roughness behavior was observed at fixed or varying plasma conditions. Parameter interactions of practical importance were observed near the plasma source or in the presence of O2 fraction at low pressure. For variations in only the source power, the DC bias was strongly correlated to the surface roughness without regard to the pressure.