Time evolution of V/sub TH/ distribution under BT stress in ultra-thin gate oxides

In this paper, time evolutions of threshold voltage (V/sub TH/) in p-MOSFETs have been investigated and discussed from the viewpoint of a statistical distribution. No change in the dispersion of the V/sub TH/ distribution under bias temperature (BT) stress was observed, whereas average values of V/sub TH/ monotonically increased. On the other hand, the V/sub TH/ distribution was remarkably deteriorated after soft breakdown progression of gate oxides.