Abstract
This study investigates GaAs dry etching in capacitively coupled <TEX>$BCl_3/N_2$</TEX> plasma at a low vacuum pressure (>100 mTorr). The applied etch process parameters were a RIE chuck power ranging from <TEX>$100{\sim}200W$</TEX> on the electrodes and a <TEX>$N_2$</TEX> composition ranging from <TEX>$0{\sim}100%$</TEX> in <TEX>$BCl_3/N_2$</TEX> plasma mixtures. After the etch process, the etch rates, RMS roughness and etch selectivity of the GaAs over a photoresist was investigated. Surface profilometry and field emission-scanning electron microscopy were used to analyze the etch characteristics of the GaAs substrate. It was found that the highest etch rate of GaAs was <TEX>$0.4{\mu}m/min$</TEX> at a 20 % <TEX>$N_2$</TEX> composition in <TEX>$BCl_3/N_2$</TEX> (i.e., 16 sccm <TEX>$BCl_3/4$</TEX> sccm <TEX>$N_2$</TEX>). It was also noted that the etch rate of GaAs was <TEX>$0.22{\mu}m/min$</TEX> at 20 sccm <TEX>$BCl_3$</TEX> (100 % <TEX>$BCl_3$</TEX>). Therefore, there was a clear catalytic effect of <TEX>$N_2$</TEX> during the <TEX>$BCl_3/N_2$</TEX> plasma etching process. The RMS roughness of GaAs after etching was very low (<TEX>${\sim}3nm$</TEX>) when the percentage of <TEX>$N_2$</TEX> was 20 %. However, the surface roughness became rougher with higher percentages of <TEX>$N_2$</TEX>.
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