Over Tenfold Increase in Contact Resistance with Scaling of MoS2 FETs: Multidimensional Constraints from Contact Length Reduction

Abstract

Two-dimensional semiconductors such as MoS2, a representative member of the transition metal dichalcogenides (TMDCs) family, possess an extremely thin atomic structure, enabling fully depleted operation in channels in MoS2 field-effect transistors (FETs) compared to silicon, thereby suppressing short-channel effects and offering significant potential for channel length scaling. However, the contact resistance (RC) does not decrease as the contact length (LC) is reduced during the scaling down of MoS2 FETs; instead, it continues to increase at shorter Lc. This phenomenon exacerbates power consumption and degrades electrical performance of MoS2 FETs at smaller scales. Thus, investigating the origin of the RC mutation and exploring the factors of scaling constraints are critical for the introduction of MoS2 FETs in integrated circuits. In this paper, we introduce a misaligned contact strategy that enables the attainment of short LC without imposing stringent requirements on photolithography resolution. Employing this strategy, we find an over tenfold increase in RC at shorter LC for MoS2 FETs. This result is directly linked to the LC being shorter than the transfer length (LT), preventing complete carrier injection into MoS2. Consequently, our findings establish the critical role of LT in MoS2 FET miniaturization and conduct multidimensional analyses of scaling constraints.