Molecular-beam study of the plasma-surface kinetics of silicon dioxide andphotoresist etching with chlorine

The plasma-surface kinetics of silicon dioxide and photoresist etching in c hlorine were measured by beam scattering in which the Ar+, Cl, and Cl-2 bea ms were independently controlled at fluxes comparable to a high-density pla sma etching process. The etching was characterized as a function of Ar+ ion energy, ion flux, chlorine-to-ion flux ratio, and the ion impingement angl e. Molecular chlorine did not enhance the etching of silicon dioxide, but a tomic chlorine enhanced the etching of oxide by a factor of 4 at flux ratio s around 100. The ion energy dependence for oxide was a linear function of (E-ion(1/2) - E-th(1/2)), where the threshold energy E-th was found to be a pproximately 40 eV. The oxide angular dependence showed a maximum etching y ield at similar to 60 degrees off-normal ion incident angle, indicating tha t physical sputtering is the rate limiting mechanism. Angular resolved x-ra y photoelectron spectroscopy analysis suggests that ion bombardment sputter s oxygen and allows atomic chlorine to bond to silicon. The etching of chlo rinated silicon is assumed to be enhanced by subsequent ion bombardment in a manner similar to ion enhanced polysilicon etching with chlorine. The ang ular dependence of photoresist etching exhibited a maximum at similar to 60 degrees off-normal ion incident angle, indicating that sputtering is the i mportant etching mechanism. (C) 2001 American Vacuum Society.