Comprehensive investigation on CF4/O2-plasma treating the interfaces of stacked gate dielectric in MoS2 transistors

Abstract

CF4/O2-plasma is used to treat the interfaces of gate stacks (MoS2/Al2O3/ ZrO2/p+-Si), and its effects on the electrical performance of the few-layered MoS2 transistors have been investigated. Experimental results show that excellent electrical properties have been achieved for the MoS2 transistors with CF4/O2-plasma treated stacked gate dielectric, especially for the F-treated ZrO2 device: high mobility of 53.7 cm2/Vs, small subthreshold swing of 117 mV/dec and high on/off ratio of 2.7 × 107. The involved main mechanisms lie in the facts that: (i) the MoS2/dielectric interface is improved through the F- passivation on the oxygen vacancies in the dielectric, decreasing the dangling bonds and surface roughness of the dielectric; (ii) the dielectric constant (k) of the gate stack dielectric is increased because of suppressed growth of low-k Zr-silicate interlayer and improved dielectric quality by forming ZrF and AlF bonds; (iii) CF4/O2-plasma treatment on the ZrO2 surface can result in F incorporation in both ZrO2 and Al2O3, thus giving the best passivation effects on oxygen vacancies and oxide traps near/at the MoS2/dielectric interface. These results indicate that CF4/O2-plasma treatment is an effective way for improving the bulk and interface qualities of gate dielectrics and thus the electrical properties of MoS2 FETs.