Field enhancement of omega-shaped-gated poly-Si TFT SONOS memory fabricated by a simple sidewall spacer formation

Abstract

A novel omega-shaped-gated (Omega-Gate) poly-Si thin-film-transistor (TFT) silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory devices fabricated with a simple process have been proposed for the first time. The Omega-Gate structure inherently covered two sharp corners manufactured simply via a side-wall spacer formation. Due to the sharp corner geometry, the local electric fields across the tunneling oxide could be enhanced effectively, thus improving the memory performance. Based on this field enhanced scheme, the Omega-Gate TFT SONOS revealed excellent program/erase (P/E) efficiency and larger memory window as compared to the conventional planar (CP) counterparts. In addition, owing to the better gate controllability, the Omega-Gate TFT SONOS also exhibited superior transistor performance with a much higher on-current, smaller threshold voltage, and steeper subthreshold swing. Therefore, such an Omega-Gate TFT SONOS memory is very promising for the embedded flash on the system-on-panel applications. (C) 2010 Elsevier Ltd. All rights reserved.