Approach to enhance deuterium incorporation for improved hot carrier reliability in metal-oxide-semiconductor devices

The deuterium isotope effect has been widely demonstrated to improve hot-carrier reliability in metal-oxide-semiconductor transistors. Most of the interface traps, however, may have been passivated by hydrogen before the final deuterium anneal due to the ubiquitous presence of hydrogen in modern complementary metal-oxide-semiconductor processing technology. Therefore, effective deuteration requires both deuterium diffusion to the SiO₂-Si interface and displacement of the previously bonded hydrogen. We have introduced a "prestress" process in which hydrogen is depassivated before deuterium annealing. We found that the prestressed transistors are more robust to hot-carrier stress than control transistors without the prestress. We have also found that the replacement of hydrogen with deuterium is the rate-limiting step for deuterium incorporation at the SiO₂-Si interface. With the prestress, a lower deuterium annealing temperature can be applied without compromising the reliability improvement.