Improved Reliability of Short-Channel IGZO TFTs With Hydrogen Scavenger Gate Metal

In this work, we propose a novel molybdenum–titanium (MoTi) gate metal technique as a hydrogen scavenger to enhance the bias temperature instability (BTI) stability of ultra-scaled IGZO thin-film transistors (TFTs). By performing temperature- and electrical-field-dependent measurements, the hydrogen (H) migration mechanisms under elevated-temperature BTI stress are identified for the first time: only H diffusion dominates in NBTI while both diffusion and drift contribute in PBTI. Based on this observation, the MoTi gate metal is introduced to function as an effective H scavenger, mitigating H diffusion toward the IGZO channel. By this design, the fabricated 100 nm IGZO TFTs with MoTi gates achieve record-low threshold voltage shift ( $\Delta \bf { V}_{\mathbf {\textit {TH}}}$ ) per oxide electric field (E ${}_{\mathbf {\textit {OX}}}$ ) of 20 mV $\cdot$ cm/MV and 7.2 mV $\cdot$ cm/MV under 125 C PBTI and NBTI stress, respectively, among all the reported sub-100nm oxide TFTs so far.