Physical damage and contamination by magnetized inductively coupled plasmas and effects of various cleaning and annealing methods

Effects of various cleaning and annealing methods on the removal of the residue and physical damage remaining on the exposed silicon surface after the oxide overetching by C4F8 magnetized inductively coupled plasmas were studied. X-ray photoelectron spectroscopy, current-voltage characteristics of Au Schottky diodes, and high resolution transmission electron microscopy were used. The formation of Co silicide was also studied using x-ray diffraction, four-point probe, and Rutherford backscattering spectrometry to investigate the effectiveness of the cleaning and annealing methods on the residue and damage removal. Thicker than 65 Angstrom of polymer and thicker than 40 Angstrom of physical damage remained on the silicon surface etched by C4F8 magnetized inductively coupled plasmas. Among the investigated cleaning methods, SF6/O-2 soft cleaning was the most effective in removing the residue. SF6/O-2 soft cleaning was also the more effective method in removing the physical damage compared to the annealing methods used in the experiment. Stable Co silicide was formed on the silicon surface after O-2 plasma cleaning followed by HF dipping or SF6/O-2 soft cleaning. Sheet resistances measured on these silicides were close to those of the silicide formed on the clean control silicon surface. Surface residue not the physical damage appeared to affect the formation of Co silicides, and fluorine rich residue appears to prevent the formation of stable silicide more compared to carbon rich residue. (C) 1997 American Vacuum Society.