Enhanced MOS 1/f noise due to near-interfacial oxygen deficiency

Abstract

The 1 f noise and radiation response of MOS transistors have been compared. A strong correlation is found between the pre- and post-irradiation noise of the transistors and their threshold-voltage shifts due to radiation-induced oxide-trap charge. It is inferred that the noise is caused by a subset of the oxide traps, which is referred to as ‘border traps’. These defects are near-interfacial oxide traps which can communicate with the Si on the timescales of the measurements, and have been mistaken for interface traps in some previous work on 1 f noise and/or radiation effects on MOS devices. Comparisons of electron-paramagnetic-resonance and radiation-effects studies offer compelling evidence that radiation-induced oxide-trap charge is associated with oxygen-deficient centers (oxygen vacancies and vacancy complexes) near the Si SiO 2 interface. It is concluded that these same defects also enhance the 1 f noise of MOS transistors, which should help to resolve the long-standing debate on the origin of MOS noise. Independent estimates of radiation-induced border-trap charge densities using a dual-transistor technique that combines threshold-voltage and charge-pumping measurements agree well with 1 f noise estimates.