SYNCHROTRON-RADIATION-EXCITED ETCHING OF SIC

Photochemical etching of an a-SiC film has been investigated using synchrotron radiation (SR) in the presence of the reactive species generated in a microwave discharge (MW) of a mixture of SF6 and Ar gases. High area selectivity between the SR-irradiated region and the nonirradiated region was obtained in this etching system. To determine the origin of area selectivity, the following etching experiments and observation of the surface have been carried out. The dependence of etching depth on pre-exposure time (t(e)) and on the SR dose was studied. To investigate the surface condition, Auger electron spectra (AES) and total electron yield (TEY) spectra were observed. The dependence of the etching depth on t(e) and SR dose suggests that a layer is formed on the surface of a-SiC at the beginning of etching. The TEY data show that the surface layer, especially in the SR nonirradiated region, becomes carbon-rich during etching. AES also suggest that carbon exists on the surface in the nonirradiated region more than that of the irradiated one. Therefore, the surface layer may prevent the etching reaction because it does not react easily with the reactive species generated in MW without SR irradiation.