Inductively coupled plasma etching of Ge-doped boron-phosphosilicate glass for planar lightwave circuit devices

Abstract

Boron-phosphosilicate glass films were deposited on silicon wafers using H 2/O 2 flame hydrolysis deposition. GeO 2 was doped up to 12 wt% for core layer. Boron and phosphorus contents were varied up to 24 and 2.4 wt%, respectively. Doping level was controlled by changing the flow rate of gaseous chemicals. The layers were patterned and then etched using inductively coupled plasma to form optical waveguides. Cr and CF 4 were used as the etch mask and the reactive gas, respectively. The effect of germanium on the etch rate is small. The etch rate of the 24 wt% boron-doped layer was larger by about 10%, compared to the 12 wt% boron-doped layer. The etch rate, selectivity and plasma-induced surface damage were affected by chamber pressure, gas flow rate, capacitively coupled power and inductively coupled power. DC bias voltage between electrode and plasma in the process chamber was the parameter which has the largest effect in controlling the etch results. DC bias voltage could be effectively controlled by capacitively coupled power and inductively coupled power.