Effects of low-energy backsurface gettering on the properties of low-frequency excess noise in NH3 and N2O nitrided MOSFETs

Nitridation of the gate dielectric for n-channel Si MOSFETs is carried out by rapid thermal annealing in either NH₃ or N₂O followed by low-energy Ar⁺ gettering. The effects on flicker noise are characterized over a wide range of temperatures and biases. The gettering time ranged from from 10 to 40 minutes for NH₃ nitrided devices and 10 and 20 minutes for N ₂O nitrided devices. The noise power spectra for devices with different gettering times are compared to the ungettered devices which serve as the control. It is found that, for both types of devices, flicker noise is reduced by backsurface gettering for short gettering times. A rebound in the noise magnitude is observed for long gettering times. Investigation of the temperature dependence of the noise power spectra indicates that the low-frequency noise arises from thermal activation of carriers to traps at the Si-SiO₂ interface. Backsurface gettering results in a modification of the energy distribution of the interface traps, probably due to stress relaxation at the Si-SiO₂ interface