Observation of reduced poly-gate depletion effect for poly-Si0.8Ge0.2-gated NMOS devices

Abstract

Poly-Si0.8Ge0.2 and poly-Si gate n-channel metal oxide semiconductor capacitors with very thin gate oxides were fabricated. Poly-gate depletion effects (PDE) in these devices were analyzed. Lower sheet resistance, higher dopant activation rate, higher active dopant concentration near the poly/SiO2 interface, and, therefore, improved PDE were found in phosphorus-implanted poly-Si0.8Ge0.2 gate as compared to poly-Si gate devices. As a result, poly-Si0.8Ge0.2 gale devices provide more inversion charge and therefore potentially provide higher current drive in metal oxide semiconductor transistors.