Abstract: Laser induced wet etching into n Si in the dilute HF:H2O(1:20) by an Ar+ laser at room temperature is reported.Smooth etch features with Gaussian shape that depends on doping level of Si were observed.The laser etch rate is influenced by the incident power.For the HF/Si system,the etching is thought to take place photoelectrochemically with holes and electrons generated by the incident illumination of the laser beam.The result is explained reasonably by the mode of electrodless etching under the laser illumination in an electrochemical cell.