High rate etching of 4H-SiC using a SF₆/O₂ helicon plasma

The etch rate of 4H-SiC in a SF₆ helicon plasma has been investigated as a function of pressure, power injected in the source, substrate bias voltage, and distance between the substrate holder and the helicon source. The highest etch rate yet reported of 1.35 μm/min along with good uniformity on 2 in. SiC substrates was achieved when this distance was minimum. Smooth etched surfaces free of micromasking have been obtained when using a nickel mask and the selectivity SiC/Ni was found to be about 50 under high etch rate conditions. Via holes have been etched to a depth of 330 μm in 4H-SiC substrates.