Effect of substrate bias on negative bias temperature instability of ultra-deep sub-micro p-channel metal--oxide--semiconductor field-effect transistors

The effect of substrate bias on the degradation during applying anegative bias temperature (NBT) stress is studied in this paper.With a smaller gate voltage stress applied, the degradation ofnegative bias temperature instability (NBTI) is enhanced, and therecomes forth an inflexion point. The degradation pace turns largerwhen the substrate bias is higher than the inflexion point. Thesubstrate hot holes can be injected into oxide and generateadditional oxide traps, inducing an inflexion phenomenon. When aconstant substrate bias stress is applied, as the gate voltagestress increases, an inflexion comes into being also. The highergate voltage causes the electrons to tunnel into the substrate fromthe poly, thereby generating the electron--hole pairs by impactionization. The holes generated by impact ionization and the holesfrom the substrate all can be accelerated to high energies by thesubstrate bias. More additional oxide traps can be produced, andcorrespondingly, the degradation is strengthened by the substratebias. The results of the alternate stress experiment show that theinterface traps generated by the hot holes cannot be annealed, whichis different from those generated by common holes.