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 A of polymer and thicker than 40 Å of physical damage remained on the silicon surface etched by C₄F₈ magnetized inductively coupled plasmas. Among the investigated cleaning methods, SF₆/O₂ soft cleaning was the most effective in removing the residue. SF₆/O₂ 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 O₂ plasma cleaning followed by HF dipping or SF₆/O₂ soft cleaning. Sheet resistances measured on these suicides were close to those of the suicide formed on the clean control silicon surface. Surface residue not the physical damage appeared to affect the formation of Co suicides, and fluorine rich residue appears to prevent the formation of stable suicide more compared to carbon rich residue.