Etch Rate Acceleration of SiO2 during Wet Treatment after Gate Etching

The etch rate of SiO2 during HF wet treatment was accelerated after gate etching. This was caused by a formation of a damaged layer on the SiO2 surface induced by the exposure to plasma. X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and atomic force microscopy (AFM) analysis established that the damaged layer includes three types of “damage”: disordering, bromine contamination and surface roughening. It was found that vacuum ultraviolet rays (VUV) contributed to the disordering of the SiO2 network. The damaged layer has a weaker binding energy and greater roughening that enable more extensive contact with the HF etchant, making it more susceptible to etching.