Thermal stability of selective chemical vapor deposited tungsten contact and effects of in situ N2 plasma treatment

Abstract

This work investigates the thermal stability of Al/W/p+-n junction diodes, in which the W contact was filled using selective chemical vapor deposition to a thickness of about 450 nm and served as diffusion barrier between the Al and the Si substrate. The effects of in situ N2 plasma treatment on the barrier effectiveness were also investigated. The Al/W(450 nm)/p+-n junction diodes can sustain a 30 min furnace annealing up to 575 °C. With an in situ N2 plasma treatment on the W surface caused a thin layer of WNx to form on the W surface, and the nitrified layer of WNx/W acting as barrier between the Al and the Si substrate effectively suppressed WAl12 formation at elevated temperatures, resulting in a significant barrier improvement. N2 plasma treatment at 100 W for 300 s enabled the Al/WNx/W(450 nm)/p+-n junction diodes to sustain thermal annealing at temperatures up to 625 °C without degradation of electrical characteristics.