Experimental Observations of the Redistribution of Implanted Nitrogen at the Si-SiO 2 Interface During RTA Processing

The redistribution of nitrogen from silicon to the Si-SiO 2 interface due to thermal processing is investigated by Secondary Ion Mass Spectroscopy (SIMS) using Metal-Oxide-Semiconductor (MOS) capacitors. SIMS profiles of implanted atomic nitrogen concentration indicate a significant redistribution of the nitrogen, from the silicon to the oxide layer in response to variations of the steady state time and temperature parameters of Rapid Thermal Anneal (RTA) processing. RTA treatment, in N 2 ambient, over a temperature range of 750°C - 1100°C, results in a measured increase of the integrated nitrogen peak at the interface. High Frequency Capacitance Voltage (HFCV) measurements of an implanted (N/ 5 × 10 14 cm 2 /s / 26keV) and annealed (900°C / 10s) sample is compared with a control (without N implant) sample to determine the relative nitrogen abundance at the interface. This value corresponds to the increase in fixed oxide charge Q that produces a negative shift in the flat band voltage Vo under negative gate bias conditions.