Process engineering of two-dimensional semiconductor field-effect transistors for post-silicon electronics

Two-dimensional (2D) layered semiconductors, such as MoS2, have been considered as promising channel materials for field-effect transistors (FETs) in the post-silicon era. Their unique properties, such as ultrathin nature, suitable bandgaps, free of dangling bonds, make them outstanding in the dimension and power consumption scaling, where the conventional silicon-based metal-oxide-semiconductor field-effect transistors (MOSFET) have encountered significant challenges to follow Moore’s Law. Using 2D semiconductors as successors to replace the channel materials in the well-established silicon technology is not an individual task. When applying these new low dimensional materials to practices, a considerable number of processes and routines come across difficulties, because the processes that have been constantly developed and improved over the last half-century are designed for the three-dimensional (3D) silicon industry. Thus, new fabrication strategies designed for the 2D semiconductor are urgently needed, before high-performance and large-scale 2D material-based FETs (2D-FETs) can be applied to the industry. Among abundant tiny but nonnegligible obstacles, the thesis focuses on scale-up, contamination control, parameters refinement, and the creation of novel dielectric materials, where novel strategies are proposed to improve electronic device performance. After an introduction of background, an inclusive literature review, and an instrument summary, the five experimental chapters present the studies on the field of materials preparation, channel isolation, contact resistance reduction, and dielectric engineering. Detailed statements of the study motivation, state-of-the-art development status, challenges, research methodologies, materials characterization and device performance characterization are also included in each experimental chapter. At the end of the thesis, all of these studies contribute to a breakthrough of MoS2-based FETs over a wafter scale, which exhibit a high ON/OFF ratio of 10^6 and steep subthreshold swings (SS) of 120 mV dec-1. These results indicate a step has moved forward to realize the practical applications of high-performance 2D-FETs