Study of a Negative Threshold Voltage Shift in Positive Bias Temperature Instability and a Positive Threshold Voltage Shift the Negative Bias Temperature Instability of Yttrium-Doped HfO2 Gate Dielectrics

We have studied unusual $V_{\text{th}}$ shifts in the positive bias temperature instability (PBTI) and negative bias temperature instability (NBTI) of yttrium-doped HfO 2 gate dielectrics. Both positive and negative stress conditions introduce shifts in opposite directions for yttrium-doped HfO 2 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 HfO 2 .