Characterization of flicker noise in N2O and NH3 nitrided MOSFETs due to low-energy Ar+ backsurface gettering

Abstract

Nitridation of gate dielectric in n-channel Si-MOSFETs was performed by rapid thermal annealing in either NH3 or N2O. Following the nitridation process the devices were subjected to low-energy Ar+ gettering at 550 eV. The gettering time ranged from 10 to 40 minutes. Flicker noise across the conduction channels was characterized over a wide range of temperatures and biases. It was found that flicker noise was reduced by backsurface gettering for short gettering times for both types of device Rebounds in the noise magnitudes are observed for long gettering times. Investigation of the temperature dependences of the noise power spectra indicates that the low-frequency noise originated from thermal activation of carriers to traps at the Si-SiO2 interface. Backsurface gettering led to modifications in the energy distribution of the interface traps. The phenomenon is attributed to stress relaxation at the Si-SiO2 interface. Our data show that short gettering times resulted in reductions in the Si-SiO2 interface states and long gettering times led to increases in the concentration of the interface states.