Charge trap generation in LPCVD oxides under high field stressing

The degradation of low pressure chemical vapor deposited (LPCVD) oxides, prepared using silane and tetra ethyl ortho silicate (TEOS) as the source, has been investigated under high field stressing. The LPCVD oxides exhibit enhanced conductivity for the Fowler-Nordheim tunneling current, which is modeled as an effective lowering of potential barrier at the injecting electrode. The charge to breakdown (Q_bd) of LPCVD oxides depends on both the deposition chemistry and post deposition annealing condition. The change in interface-state density (ΔD_it), flatband voltage (ΔV_fb), and gate voltage (Δ|V_g|) during constant current stressing are studied to identify the degradation mechanism. We see a very good correlation between Q_bd and Δ|V_g|, indicating that the degradation in LPCVD oxides is dominated by bulk trap generation and subsequent charge trapping. We present a detailed theoretical analysis to substantiate this