To optimize electrical properties of the ultrathin (1.6 nm) nitride/oxide gate stacks with bottom oxide materials and post-deposition treatment

The electrical properties affected by the bottom oxide materials and the post-deposition treatment on the ultrathin (down to 1.6 nm) nitride/oxide (N/O) stacks, prepared by rapid thermal chemical vapor deposition (RTCVD) with two-step NH₃/N₂O post-deposition annealing, for deep submicrometer dual-gate MOSFETs have been studied extensively. N/O stack with NO-grown bottom oxide exhibits fewer flat-band voltage shifts and higher hole and electron mobility, but suffers from worse leakage current than that with conventional O₂-grown bottom oxide. In post-deposition treatment, increasing NH₃ nitridation temperature can effectively reduce the equivalent oxide thickness (EOT) and improve leakage current reduction rate, but it can result in worse mobility. Furthermore, the subsequent N₂O annealing eliminates the defects and offers a contrary effect on the N/O stack in comparison with the NH₃ nitridation step.