Characterization of NBTI-induced positive charges in 16 nm FinFET

Negative Bias Temperature Instability (NBTI) is one of the most critical reliability problems in nano-scale p-MOSFETs. The NBTI-induced positive charges cause threshold voltage shifts, hence degrading the performance of the device. However, the characteristics of the positive charges (PC) in FinFET devices are currently not well-understood. In this work, a numerical simulation using an energy profiling technique on a 3D FinFET structure suggests that the positive charges are sensitive to energy level and differ considerably over the energy range, in agreement with the published measurements. The PCs which are distributed below, within and above the energy bandgap are known as as-grown hole traps (AHT), cyclic positive charges (CPC) and antineutralization positive charges (ANPC) respectively. The AHTs are found to be insensitive to stress time and temperature; the CPCs can saturate at longer stress time and higher stress temperatures; while the ANPCs do not saturate. The CPC density peak is found to be at E_f- E_v ~ 1 eV, in quantitative agreement with published measurements from Hf-based p-MOSFET. The fin width is found to have observable effect on the location of the PC density peak along the energy range, hence robust optimization of the fin width is crucial for better immunity against NBTI.