Excimer Laser-Assisted Etching of Silicon Using Chloropentafluoroethane

Abstract

ABSTRACTLaser-assisted photothermal chemical reactions have been observed with silicon in a chloropentafluoroethane ambient using a KrF* laser at 248 nm. Etching occurs onlyif the incident fluence exceeds the melt threshold (∼0.75 J/cm2, with the melt duration determined by observing the change in silicon reflectance at 633 nm. Above the ablation threshold (∼2.2 J/cm2) increased surface roughness is observed. Etch rates -7 Å/pulse have been measured using both stylus profilometer and SEM cross-sectional techniques. The etch rate dependence on incident fluence, ambient pressure, doping concentration, crystal orientation and substrate temperature have been examined suggesting an adsorption limited thermal process. This process allows single step patterning of silicon devices in a non-corrosive environment.