Manufacturing optimization for Silicon Trench rectifiers using NiPt salicide

Abstract

The purpose of this study was to provide a low cost manufacturing solution for Silicon Trench based Schottky rectifiers utilizing NiPt alloy composition that produces multiple barrier heights and provide designers the option to easily adjust the barrier height (BH) for rectifier designs. Higher temperatures needed to obtain larger barrier heights are generally unfavorable for trench-based Schottky rectifiers. The silicides in trench rectifiers are separated by relativity small distances with nonreactive material (such as silicon oxide) and with high energy anneals and the silicon from the substrate will migrate creating a Ni(Pt)Si bridge between adjacent silicides. Additional issues arise from thicker Ni(Pt)Si growth near the gate oxide interface causing localized high silicon stress. Both these issues cause device performance issues such as increased diode leakage. Most common industry solution is to change the %Pt in the Ni alloy thus modulating the BH. A low cost solution is to use one NiPt alloy to meet multiple BH needs by changing the anneal conditions and adding a Ti “Cap” to the NiPt film.