Refined electrical analysis of two charge states transition characteristic of “borderless” silicon nitride

In this paper we evaluate the electrical properties of silicon nitride so called “borderless nitride” deposited by PECVD process in the pre metal dielectric stack. Thus metal/silicon nitride/semiconductor structures have been analysed by an original electrical characterization based on C(V) and I(V) hysteresises. The objective is to understand how this material, initially introduced as etch stop layer and contaminant diffusion barrier, can impact active device performances. It appears that silicon nitride contains a huge defect quantity characterized in a non steady state and strongly influenced by maximum voltage applied. These charges can be balanced between either positive and negative states and are suspected to be K centers defects existing under two paramagnetic states K+ and K−. In addition, a RF power variation of SiH4/NH3 ratio, giving refractive indexes from 1.94 to 2.77, have shown that flatband voltage shift decreases with [Si]/[N] ratio whereas leakage current increases.