Electron injection studies of radiation induced positive charge in MOS devices

Abstract

Avalanche injection and internal Photoemission techniques have been used to study the capture of electrons by positive charges introduced into the oxide layers of MOS capacitors. These two techniques have been used to study the positive charge in Al gate and poly-Si gate capacitors. The electron capture crosssection of this charge has been found to depend on the composition of the interface; positive charge at the Si interface tends to have a coulombic electron capture crosssection (∽4×10-13cm2), while that at the aluminum interface has a non-coulombic electron capture crosssection (=10-14cm2). The location of the positive charge induced by radiation under positive or negative bias has been determined in a completely nondestructive manner by photocurrent-voltage experiments. It has been found that under a positive irradiation bias, positive space charge accumulates within ∽50 Å of the Si-SiCU interface, while under a negative bias, the space charge is within ∽50 Å of the Al-SiO2 interface. In both cases there is evidence for some charge at the other interface introduced by the irradiation. Copyright © 1976 by The Institute of Electrical and Electronics Engineers, Inc.