Implantation Profile and Buried-Channel Depth in Ion Implanted MIS Structures

Abstract

For many applications, the channel regions of MOS transistors are implanted with impurities causing counter-doping of the semiconductor. The result is the formation of a p-n junction and, under most operating conditions,a conducting channel buried at a certain depth in the semiconductor [1]. This phenomenon is reflected in the transistor characteristics by a threshold, a transconductance and a body effect differing from normal non-implanted transistors. It is the aim of this paper to describe the effects of ion implantation on the surface band bending (this alters the threshold and the body effect) and on the channel depth. They can be deduced from measurements of the body effect of implanted transistors, and they can be used to draw conclusions on the implanted impurity profile.