Improvement by Channel Recess of Contact Resistance and Gate Control in Large-Scale Spin-Coated MoS2 MOSFETs
Kuanchen Xiong, Lei Li, Roderick J Marstell, Asher Madjar, Nicholas C Strandwitz, James CM Hwang, Zhaoyang Lin, Yu Huang, Xiangfeng Duan, Alexander Göritz, Matthias Wietstruck, Mehmet Kaynak
IEEE Electron Device Letters 39, 1453-1456 (2018)
Solution-processed 2-D materials, being low temperature, low cost, and scalable, are attractive for future-generation thin-film and flexible transistors. However, it is challenging to dispense solution-processed 2-D material into a thin and continuous channel for effective and uniform gate control. In addition, a thick channel under the source and drain contacts is required to increase the transfer length and decrease the edge contact resistance. To overcome such a dilemma and to obtain the optimum combination of effective gate control and low contact resistance, channel recess was demonstrated for the first time on MoS 2 , so that the channel is thin in the gate region but thick in the source and drain regions. Specifically, channel recess by CHF 3 /O 2 dry etching up to 60 s was performed on submicron buried-gate MOSFETs fabricated on 20-nm-thick spin-coated MoS 2 . It was found that the channel recess improved the current on/off ratio by 3 orders of magnitude while maintaining approximately the same contact resistance and peak transconductance as that of a uniformly 20-nm-thick channel. The resulted performance was among the best of all solution-processed MoS 2 MOSFETs. The same channel recess technique can be used to improve the performance of MOSFETs made of other solution-processed 2-D materials.