First Demonstration of High-Performance Three-Tier IGZO Channels Gate-All-Around Thin-Film Transistors With Novel Metal Interlayer Contact

For the first time, highly integrated IGZO transistors suitable for back-end-of-line (BEOL) integration are demonstrated, leveraging an in-situ ozone interfacial layer (IL) treatment before HfO2 deposition. The ozone-treated gate-all-around (GAA) devices achieve an outstanding subthreshold swing (S.S.) of 64 mV/dec at L = 150 nm, approaching the theoretical limit, and exhibit an Ion/Ioff ratio exceeding 1:44 × 108. The ozone IL treatment significantly reduces oxygen vacancy (VO) concentration, enhancing channel integrity, electrostatic control, reliability, scalability, and subthreshold swing precision. This metal interlayer significantly reduces source/drain contact resistance, resulting in a 2:3× performance enhancement for three-tier devices compared to single-tier counterparts. These combined advancements underscore the potential of IGZO GAA structures for next-generation high-performance semiconductor applications.