Neutral E' centers in microwave downstream plasma-enhanced chemical-vapor-deposited silicon dioxide

Abstract

We have utilized electron spin resonance and capacitance versus voltage measurements to study E' centers generated by the photoemission of electrons into silicon dioxide films prepared by plasma-enhanced chemical vapor deposition (PECVD). The oxides were deposited on crystalline silicon substrates downstream from a microwave discharge. The E' center is an unpaired electron in a nonbonding sp3 hybrid orbital on a silicon bonded to three oxygen atoms. In conventional thermal SiO2 films on silicon, E' centers are the dominant deep hole traps. However, the E' centers generated in the PECVD oxides are generated by electron injection into the oxide and are almost certainly electrically neutral. Our results unequivocally demonstrate fundamental differences in the point defects in thermally grown SiO2 on silicon and PECVD oxides.