Silicon Carbide Wafer Machining by Using a Single Filament Plasma at Atmospheric Pressure

SiC wafers were etched using a filament plasma of He:NF3:O-2 (helium:nitrogen trifluoride:oxygen) mixed gas at atmospheric pressure. When 0.5-2 sccm of NF3 was mixed to 2 slm of He filament plasma, the etch depth and etch rate increased, but there was little change in the etch width as the NF3 mixing amount increased. The increment of the NF3 mixing also suppressed the surface roughening of plasma etching. The addition of O-2 to the He-NF3 filament plasma slightly increased the SiC wafer etch rate. When the NF3 mixing amount was 2 sccm, the roughness of the etched surface increased sharply by O-2 addition. On the contrary, the NF3 mixing amount was 1 sccm; the addition of O-2 reduced the roughness more than that of the pristine. The roughness of the pristine SiC wafer specimens is in the range of Ra 0.7-0.8 nm. After 30 min of etching on a 6 mm by 6 mm square area, the roughness of the etched surface reduced to Ra 0.587 nm, while the etch rate was 2.74 mu m/h with a He:NF3:O-2 of 2:1:3 (slm:sccm:sccm) filament plasma and 3 mm/s speed of raster scan etch of the optimized roughening suppression etching recipe.

Automated summary

The study showed that the addition of NF3 in the He:NF3:O-2 mixed gas plasma increased the etch depth and rate of SiC wafers while suppressing surface roughening. The introduction of O-2 had a varying effect on the surface roughness, depending on the amount of NF3 mixed in the plasma.