Resistless photochemical etching of a silicon wafer by UV laser with an H_2O_2 and HF aqueous solution

A new resistless etching method has been de-veloped for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H2O2) and hydro-gen fluoride (HF) as the activating etchants. A 193 nm ArF excimer laser and a 266 nm fourth harmonic generation Nd:YAG laser were used as the photon sources. Results showed that pattern etching has been achieved without any photoresist film. In the case of the 193 nm laser, the optimal etching appeared at a 1.3 H2O2/HF ratio, where an etchdepth of 210 nm was achieved with a fluence of 29 mJ/cm2 and shot number of 10000. At the same conditions, the etch depth with H2O2 and HF solution was three times of that by using H2O and HF mixture. In the case of the 266 nm Nd : YAG laser, the optimal etching appeared at twice ratio of H2O2/HF, where the etch depth of 420 nm was achieved witha fluence of 12 mJ/cm2 and shot number of 30000. Results showed that the etch effect of the 266 nm Nd : YAG laser was more desirable than that of the 193 nm ArF