Effect of high-temperature H2-anneals on the slow-trapping instability of MOS structures

It is shown that the slow-trapping instability upon negative bias-temperature aging of MOS structures (poly-Si and Al-gate) can be significantly reduced by a high temperature (800–900°C) H₂-anneal prior to Al metallization. Additional data are presented on the effects of high (700–900°C) and low temperature (450°C) H₂ annealing of MOS structures containing n-(111) Si, dry HCl oxide and B-doped poly-Si. The midgap N_ss (range: 8×10¹¹ to 1.5×10¹⁰ cm^?2 eV^?1) is reduced by both high and low temperature H₂ anneals whereas the Q_ss (range: 7×10¹¹ to 1×10¹¹ cm^?2 eV^?1) is reduced mainly by the high-temperature H₂-anneals. Presence of B near the interface is believed to cause an abnormal voltage asymmetry of the slow-trapping drift, i.e. ΔV_FB(-BT) < ΔV_FB(+BT). These effects are discussed in the light of Deal's model of the structure of the Si/SiO₂ interface.