Method for laser-assisted silicon etching using halocarbon ambients

摘要

An etching process allows a selective single-step patterning of silicon devices in a noncorrosive environment. The etching of silicon relies on a maskless laser-assisted technique in a gaseous halocarbon ambient, such as the gaseous chlorofluorocarbons, dichlorodifluoromethane and chloropentafluoroethane. Laser-assisted photothermal chemical etching reactions on silicon occur in these ambients when the incident fluence from an excimer laser at 248 nm exceeds the melt threshold (approximately 0.75 J/cm2). When incident fluence exceeds the ablation threshold (approximately 2.2 J/cm2) an undesirable, increased surface roughness is observed. Etch rates as large as approximately 15 angstroms per pulse are attained within predetermined processing windows. This provides a means for thin membrane formation in silicon, rapid etches and processing of packaged devices or partially fabricated dies. The reduction in processing steps as compared to conventional wet chemical etches provides improvements in yield, reliability and cost.