Improving the Performance of Nanowires Polycrystalline Silicon Twin Thin-Film Transistors Nonvolatile Memory by NH3 Plasma Passivation

Abstract

This study investigates the performance improvement of the polycrystalline silicon nanowires twin thin-film transistors nonvolatile memory (poly-Si NWs twin-TFT NVM) by NH3 and H2 plasma treatment. The NWs twin-TFT NVM exhibits superior gate control because its tri-gate structure provides a large memory window (ΔVth) and high program/erase (P/E) efficiency. Additionally, the proposed twin-TFT NVM scheme has effective NH3 and H2 plasma passivation efficiency due to its split nanowire channels structure. As for characteristics of transistors, passivation by both NH3 and H2 plasma increases the mobility and the Ion/Ioff ratio. Moreover, as for characteristics of NVM, they increase ΔVth, P/E speed and improve the reliability of the devices. Comparing channel hot electron (CHE) injection and Fowler–Nordheim (FN) tunneling programming mechanisms reveals that the device with NH3 plasma passivation can significantly enhance the program speed. This ability is attributed to passivation of the defects in both the grain boundaries of the poly-Si channel and the Si/SiO2 interface by hydrogen and nitrogen radicals, respectively. As for reliability results, the NH3 plasma-passivated NVM device has memory windows of 1.7 and 3.8 V after 103 P/E cycles and for ten years of data storage, respectively.