An estimation of inversion-layer EOT influenced by quantum effects for sub-20nm MOSFETs

In this work, we investigate the quantum effects of the inversion layer for sub-20 nm MOSFETs. In ITRS reports, inversion-layer EOTs are calculated by using an analytical program: MASTAR. In the program, the electrostatic potentials in the inversion-layer are estimated by using a triangular quantum well approximation. We evaluate an accuracy of the approximation and estimate the inversion-layer EOTs. In order to estimate the inversion-layer EOTs, we use a Schrödinger/Poisson (S/P) model which solves the Schrödinger and Poison equations self-consistently. Test devices are low standby power (LSTP) and low operating power (LOP) bulk MOSFETs down to 18 nm. It is found that inversion-layer EOTs using MASTAR are 4.0 - 6.3% thinner than those using S/P model. The results indicate that MASTAR underestimates the inversion-layer EOT for sub-20 nm MOSFETs.