Positive/negative BT instability in scaled N/P-MOSFETs and MOSCs

The paper reports on the newly analyzed BT instability that can threaten scaled CMOS devices. During the development of 1.8V technology with surface-channel PMOSFETs, a large PMOS negative bias instability is found. The instability resembles the reported NBTI, but three different modes are found through detailed analyses: PMOS degrades under both stress polarities (p+, p-), and NMOS degrades slowly and only under negative V_G (n-). Through the detailed analysis of MOSFET and MOSC degradation, positive fixed charges are not found, and it is confirmed that the generation of donor surface states is common to all three modes of degradation. In PMOSFETs, the Fermi level, E_F is low in the device operation, and positively charged donor states cause large V_T shifts. In NMOSFETs, since E_F is high in the device operation, the donor states are mostly neutral, and only minor V_T shift results