Issues of contact etching and pre-treatment in Schottky contact

Abstract

This paper reports on the process dependence of contact resistance of silicide/n+ Si and silicide/p+ Si contact. Three processes such as contact etching, Si treatment and pre-treatment are investigated with contact resistance point of view. Only silicide/p+ Si contact resistance has been changed as etching time of contact increases while silicide/n+ Si contact resistance has been regularly maintained. We have modeled that fluorine used in contact etching can scavenge or deactivate boron in p+ Si, resulting in degradation of silicide/p+ Si contact resistance. In order to confirm the model, two different gases (hydro carbon fluoride/carbon fluoride) during Si treatment right after contact etching were applied. As a result, the silicide/p+ Si contact resistance was increased in carbon fluoride case, which has higher fluorine ratio to carbon than hydro carbon fluoride case. It is also observed that the silicide/p+ Si contact resistance was increased proportionally with time of fluorine-based pre-treatment before silicide formation.