Impact of negative-bias temperature instability on the lifetime of single-gate CMOS structures with ultrathin (4-6 nm) gate oxides

The lifetime of ultrathin gate oxides under low-field stress conditions has been studied on the basis of empirical acceleration equations for negative-bias temperature instability (NBTI) up to 5000 hours for 4.2-to-30-nm-thick oxides of metal-oxide-silicon (MOS) structures. The derived lifetime, the maximum acceptable oxide field, and the maximum acceptable operating voltage are found to be strongly dependent on the reliability specification. Since the number of interface traps induced by NBTI is inversely proportional to the oxide thickness. this instability becomes an important factor limiting the lifetime of single-gate CMOS structures with ultrathin gate oxides.