Cost-effective amorphous silicon hard mask patterning sub-45nm contact trench

A cost-effective process fabricating nanoscale SiO₂ contact trench below 45nm was developed using amorphous silicon hard mask in a CCP etcher. When using both photo resist (PR) and α-Si hard mask to etch SiO₂ layer, a typical problem of sidewall bowing was observed due to polymer accumulation on both sides of mask and effect of deviated ions from normal direction. It is more favorable using simple α-Si to etch SiO₂ by an additional PR strip step. Finally, a slightly tapered contact trench has been achieved without visible sidewall bowing, which will be useful for metal filling in the trench.