BROAD-PULSED GA ION-BEAM-ASSISTED ETCHING OF SI WITH CL2

The characteristics of ion-beam-assisted etching (IBAE) of Si with Cl2 have been investigated using a broad-pulsed Ga ion beam, with several parameters such as Cl2 gas flux, ion beam dwell time, sample temperature, and beam diameter. A simple adsorption model where the density of the adsorbed Cl2 molecules mainly rules the etching yield, can explain the trend of the process in a short dwell-time region of less than 1 ms, and etching parameters are determined. However in a longer dwell-time region of more than 10 ms, the experiment showed several times higher etching yield than the prediction using the simple model with a 2.2-mum-diam beam. The etching model with consideration Of Cl2 surface diffusion can explain this difference in etching yield and shows good agreement with the experiment throughout the entire region of dwell time. A diffusion coefficient of 8.0 X 10(-6) cm2/s at room temperature was obtained by fitting theoretical curves in the experiment.