Radio-frequency Superiority of Poly-Si TFTs with T-Shaped Gate and Air Spacers for IoT Applications

We report the first of its kind, self-organized poly-Si TFT structure of T-shaped silicided gate, air-spacers, as well as silicided source/drain in a single etching process followed by Ni self-aligned silicidation (SALICIDE) process. Process-controlled tunability of the T-shaped gate length and sidewall air-spacers have been demonstrated, enabling a practically achievable core building block for high-performance radio-frequency (RF) poly-Si TFTs. Detailed structural and electrical properties of the T-gate poly-Si TFTs were assessed using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and gate resistance, sidewall capacitance, as well as dc and RF measurements. Notably, unity-gain frequency of 12.1 GHz is recorded for our T-gate poly-Si TFTs with channel length of 96 nm.