Drive Current improvement in vertical MOSFETS using hydrogen anneal

This paper reports a study of the effect of a hydrogen anneal after silicon pillar etch on the electrical characteristics of surround-gate vertical MOSFETs. Electrical results on 120 nm, n-channel, surround-gate vertical MOSFETs show that the hydrogen anneal gives rise to a 30% improvement in drive current in comparison to transistors without the hydrogen anneal. This improved performance is obtained even though a sacrificial oxidation was performed prior to the hydrogen anneal to smooth the pillar sidewall. The hydrogen anneal has little effect on the values of sub-threshold slope and DIBL, with excellent values of 79mV/decade and 45mV/V respectively being achieved. The results are explained by an improved mobility due to a reduction in surface roughness on the silicon pillar sidewall and a gate oxide thinning by the hydrogen anneal.