Low temperature etching of silylated resist in oxygen plasma generated by an electron cyclotron resonance source

Dry development of silylated resist has been studied using an O₂ plasma generated by a multipolar electron cyclotron resonance source. Etch rate, uniformity, selectivity, and profile were investigated as a function of process parameters including microwave power, RF power, flow rate, sample area, pressure, temperature, and gas addition. It was found that etch rate increases as microwave and/or RF power increase. Vertical etch profile was obtained by using low pressure (3 mTorr) and 50 W RF power. As the area of the samples was increased from 1 to 81 cm², the etch rate decreased from 0.85 to 0.6 μm/min at a flow of 10 sccm O₂ but remained constant at 0. 9 μm/min with 100 sccm O₂. Etch rate was independent of temperature and decreased with the addition of N₂or CF₄. Etch uniformity was within ±3% across a 150 mm wafer for most etch conditions. The selectivity of the silylated layer over the photoresist degraded from 445 to 14 as RF power was increased from 25 to 100 W. Residue-free surface and vertical profile have been obtained with features as small as 0.1 μm.