Sodium passivation dependence on phosphorus concentration in tetraethylorthosilicate plasma-enhanced chemical vapor deposited phosphosilicate glasses

Mobile ions like sodium are known to cause instabilities in metal oxide semiconductor devices. Phosphosilicate glasses (P glasses) have been used as passivating layers to isolate the active devices from such contamination. In this study we have examined the effectiveness of tetraethylorthosilicate plasma-enhanced chemical vapor deposited P glasses, as the barrier to sodium diffusion, as a function of the phosphorus concentration. High-frequency capacitance versus voltage (C-V) measurements, bias-temperature measurements, C-V measurements after etch back, and current versus voltage (I-V) measurements were performed. The results of these C-V and I-V studies on P-glass samples purposely contaminated with sodium and annealed indicate that 2-4 wt % of phosphorus is sufficient to passivate successfully against sodium.