HTRB & THB Reliability Improvement Using Capping Layer in Power Discrete Trench Devices

In power discrete trench devices, the introduction of a TEOS capping layer in the PMD stack greatly alleviates the HTRB and THB reliability marginality problem. The failure mechanisms of HTRB Vth drift and THB Idss drift are inadequate proton (H
⁺
) gettering sites in the PMD bulk and moisture accumulation on the PMD surface, respectively. Utilization of a capping layer in the PMD stack enables the PMD surface to be free of Phosphorus (P) which is responsible for moisture build-up and hence THB failure, and at the same time keeping the PMD bulk with high level of P concentration for more H
⁺
gettering sites and hence better HTRB performance.