Interface state energy distribution and Pb defects at Si(110)/SiO2 interfaces: Comparison to (111) and (100) silicon orientations

Abstract

Traps at the (110)Si/SiO2 interface are investigated by combining electrical methods with electron spin resonance (ESR) measurements, and the results are compared to the well studied (100) and (111)Si/SiO2 interfaces. At all three Si crystal faces, the interface trap density Dit as function of energy E in the Si band gap exhibits two peaks at about 0.25 and 0.85 eV above the Si valence band, found to be well correlated with Pb(0) centers (Si3≡Si• defects). By comparing capacitance-voltage (CV) curves at 300 and 77 K of both n- and p-type samples, the Pb(0) defects are confirmed to be amphoteric. Effective passivation of interface traps by H2 annealing suggests that Pb0 defects are responsible for most of interface traps observed in (110)Si/SiO2. The truly amphoteric behavior, implying that one Pb0 defect delivers two interface trap levels, was observed for the (100) and (111)Si faces but not for the (110) face. The estimated interface trap density Nit at the (110)Si/SiO2 interface oxidized at 930 °C is (6.7±0.5)×1012, while the Pb0 density as determined by ESR is about (6±1)×1012 cm−2. Lowering of the oxidation temperature leads to further reduction in the electrically active Pb0 centers fraction at the (110)Si/SiO2 interface.