Abstract
We have studied unusual Vth shifts in the positive bias temperature instability (PBTI) and negative bias temperature instability (NBTI) of yttrium-doped HfO2 gate dielectrics. Both positive and negative stress conditions introduce shifts in opposite directions for yttrium-doped HfO2 in the low stress region. That is, a negative shift under a positive bias and a positive shift under a negative bias were observed. This is due to yttrium-related defects, with electron detrapping for PBTI and electron trapping for NBTI. Such defect formation can be suppressed by incorporating nitrogen into HfO2.