LOWER PLASMA-INDUCED DAMAGE IN SIO2/SI AT LOWER TEMPERATURES

We found that the radiation damage induced in a SiO2/Si system during plasma processing depends strongly on the specimen temperature. The surfaces of the SiO2 have been exposed to a microwave plasma at different temperatures and the resultant damage has been evaluated by capacitance-voltage (C-V) measurements. The flatband voltage shift (ΔVFB) for the specimen exposed to the plasma at 126 K has been found to be only 1/3 of that at 300 K. In case of vacuum ultraviolet photon irradiation through a thin Al film, the ΔVFB for the irradiation at 126 K has been only 1/5 of that at 300 K. It is believed that this lower plasma-induced damage at the lower temperature is due to the small mobility of hole in SiO2 at lower temperatures. Plasma etching at low temperature has the advantage of low damage generation in the SiO 2/Si structures.