Low bias dry etching of SiC and SiCN in ICP NF_3 discharges

摘要

A parametric study of the etching characteristics of 6H p~+ and n~+ SiC and thin film SiC_(0.8)N_(0.2) in Inductively Coupled Plasma NF_3/O_2 and NF_3/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF_3 percentage and rf chuck power reaching 3500 A centre dot min~(-1) for SiC and 7500 A centre dot min~(-1) for SiCN. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tin-oxide (ITO) masks display relatively good etch selectivity over SiC(maximum of 70:1) while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF_C/O_2 discharges, while extensive surface degradation occurs for SiCN under high NF_3:O_2 conditions. The high ion flux available in the ICP tool allows etching even at very low dc self-biases, <=-10V, leading to very low damage pattern transfer.