Passivation of interface-states in large-area Si devices using hydrogen implantation

We have found that in the large-scale transistor structures, where gate oxide thickness of 6 nm and below is used, the standard post-metallization (forming gas) annealing leaves a large number of Si/SiO₂ interface states unpassivated, with a lower limit of N/sub it/=5e11 cm/sup -2/. This may be due to the limited range of hydrogen (H) diffusion through the thin gate oxide and its ensuing inability to reach beyond the edges of the devices with a channel length larger than 3.0 μm. We have shown that hydrogen ion implantation can successfully remove the residual interface state by placing the hydrogen uniformly throughout the area of a large device. Remarkable improvements in all the device characteristics, including capacitance and current versus voltage and the transistor threshold behavior as a function of the channel length, was achieved by hydrogen implantation and anneal as a final processing step.