RASP: Reliability ab initio simulation package of MOSFETs based on all-state model

Abstract

As transistors continue to scale down, device reliability has become a critical concern. In order to accurately simulate defect-induced reliability degradation in MOSFET based logic, memory and power devices, we develop RASP (Reliability Ab initio Simulation Package), which implements the all-state model for reliability simulation. Unlike conventional two-state and four-state models that consider only two and four defect configurations respectively, the all-state model systematically considers all possible defect configurations in amorphous gate dielectrics and all nonradiative multiphonon (NMP) and thermal transition pathways among them. With defect parameters obtained from ab initio calculations as input, RASP enables accurate simulation of threshold voltage shifts caused by defects. Using RASP to simulate oxygen vacancies in a-SiO$_2$, we find that they are a non-negligible source of negative bias temperature instability (NBTI).

Figures (13)

• Figure 1: Defects in the MOSFET gate dielectrics and the associated carrier capture process. (a) Schematic of defects in the MOSFET gate dielectric. (b) Band diagram before and (c) after hole capture by an oxide defect.
• Figure 2: Configuration coordinate diagram and phonon wavefunction for nonradiative multiphonon transitions.
• Figure 3: Time-dependent $\chi_{HT}$(t) including non-Condon effects in the Fourier transform method.
• Figure 4: Accuracy test of the lineshape-function interpolation method. The surface shows the lineshape function obtained by interpolation as a function of $(\Delta E,\Delta Q)$, while the markers denote values computed directly. The markers lie on the interpolated surface, demonstrating the high accuracy of the interpolation method.
• Figure 5: Stable and metastable configurations of V$_\mathrm{O}^{0}$ and V$_\mathrm{O}^{+}$ formed at the selected oxygen site, and the corresponding transition pathways. In the neutral charge state, V$_\mathrm{O}^{0}$ exists four configurations, i.e., Si-dimer, left-back-projected (left-BP), right-back-projected (right-BP), and double-back-projected (double-BP), where the Si-dimer configuration is the ground-state. In the $+1$ charge state, V$_\mathrm{O}^{+}$ exhibits three configurations, i.e., left-in-plane, right-in-plane, and right-back-projected (right-BP), where the left-in-plane configuration is the ground-state. Thermal transitions occur between configurations with the same charge state and are denoted by the horizontal black lines. NMP transitions (hole capture/emission) occur between configurations of different charge states and are denoted by the red, blue, and green lines.