High-performance sidewall damascened tri-gate poly-si TFTs with the strain proximity free technique and stress memorization technique

In this paper, strained channel-sidewall damascened tri-gate polycrystalline silicon thin-film transistors (SC-SWDTG TFTs) have been successfully fabricated and then demonstrated by an innovative process flow. This process flow without the use of advanced lithography processes combines the sidewall damascened technique (SWDT) and two strain techniques, namely, the strain proximity free technique (SPFT), and the stress memorization technique (SMT), in the poly-Si channels. It has some advantages: (1) the channel shapes and dimensions can be effectively controlled by the wet etching processes and the deposition thickness of the tetraethoxysilane (TEOS) oxide; (2) the source/drain (S/D) resistance can be significantly decreased by the formation of the raised S/D structures; (3) the SPFT, SMT, and the rapid thermal annealing (RTA) treatment can enhance the performance of the SC-SWDTG TFTs without the limitation of the highly scaling stress liner thickness in deep-submicron TFTs. Thus, the SC-SWDTG TFTs exhibit a steep subthreshold swing (S.S.) ∼ 110 mV/dec., an extremely small drain induced barrier lowing (DIBL) ∼12.2 mV V^-1, and a high on/off ratio ∼10⁷ (V _D = 1 V) without plasma treatments for future three-dimensional integrated circuits (3D ICs) applications.