Anomalous increase in hot-carrier-induced threshold voltage shift in n -type drain extended metal-oxide-semiconductor transistors

Anomalous increase in positive threshold voltage shift (Δ VT) in n -type drain extended metal-oxide-semiconductor (DEMOS) transistors stressed under high drain voltage and gate voltage is observed. Charge pumping data and technology computer-aided-design simulations reveal that hot-electron injection and trapping in the gate oxide above channel region is responsible for Δ VT. Enhanced impact ionization rate resulted from the presence of large amount of negative oxide charge in channel region is identified to be the main mechanism for anomalous increase in Δ VT. From the results presented in this letter, hot-carrier-induced anomalous increase in Δ VT can become a serious reliability concern in DEMOS transistors.