ROLE OF OXYGEN IN POLY-SI ETCHING BY CL-2 O-2 PLASMAS/

The increase in poly-Si etch rate at low O-2 concentration (1-5%) in C l-2/O-2 plasmas was investigated using optical emission spectroscopy ( OES) and X-ray photoelectron spectroscopy (XPS). The OES spectrum indi cates that the Cl(837.5 nm) intensities increase at low O-2 concentrat ion during the poly-Si etching but the dissociation of Cl-2 is not pro moted by the addition of O-2 to Cl-2 SiCl (287 nm) intensities decreas e in the range of O-2 concentration where poly-Si etch rate increases. The result of XPS shows that by increasing O-2 concentration from 0% to 3%, the amount of Cl and O adsorbed onto poly-Si surface decreases and increases, respectively. In Cl-2/O-2 plasmas, a cause of the poly- Si etch rate increase may be that oxygen atoms adsorb more easily on t he poly-Si surface than chlorine atoms, and this weakens the Si-Si bac k bonds.