Capacitively Coupled Dry Etching of GaAs in BCl 3 /N 2 Discharges at Low Vacuum Pressure

This study investigates GaAs dry etching in capacitively coupled BCl /N plasma at a low vacuum pressure (>100 mTorr). The applied etch process parameters were a RIE chuck power ranging from 100~200 W on the electrodes and a N composition ranging from 0~100 % in BCl /N 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 0.4 µm/min at a 20 % N composition in BCl /N (i.e., 16 sccm BCl / 4 sccm N ). It was also noted that the etch rate of GaAs was 0.22 µm/min at 20 sccm BCl (100 % BCl ). Therefore, there was a clear catalytic effect of N during the BCl /N plasma etching process. The RMS roughness of GaAs after etching was very low (~3 nm) when the percentage of N was 20 %. However, the surface roughness became rougher with higher percentages of N.