Capacitively Coupled Dry Etching of GaAs in BCl3/N2 Discharges at Low Vacuum Pressure

This study investigates GaAs dry etching in capacitively coupled $BCl_3/N_2$ plasma at a low vacuum pressure (>100 mTorr). The applied etch process parameters were a RIE chuck power ranging from $100{\sim}200W$ on the electrodes and a $N_2$ composition ranging from $0{\sim}100%$ in $BCl_3/N_2$ 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 $0.4{\mu}m/min$ at a 20 % $N_2$ composition in $BCl_3/N_2$ (i.e., 16 sccm $BCl_3/4$ sccm $N_2$). It was also noted that the etch rate of GaAs was $0.22{\mu}m/min$ at 20 sccm $BCl_3$ (100 % $BCl_3$). Therefore, there was a clear catalytic effect of $N_2$ during the $BCl_3/N_2$ plasma etching process. The RMS roughness of GaAs after etching was very low (${\sim}3nm$) when the percentage of $N_2$ was 20 %. However, the surface roughness became rougher with higher percentages of $N_2$.

저진공 축전 결합형 BCl3/N2 플라즈마를 이용한 GaAs의 건식 식각