Optimizing Length Scalability of InGaZnO Thin‐Film Transistors through Lateral Carrier Profile Engineering and Negative ΔL Extension Structure

Abstract

The lateral carrier profile of amorphous indium gallium zinc oxide (IGZO) thin‐film transistors (TFTs) plays a significant role in determining the effective channel length (Leff) and length scalability even when the physical gate length (Lg) is the same. Especially, devices with high carrier concentration that have a high mobility of 14.54 cm2 V·s−1 suffer from severe short channel effects at Lg = 1 µm due to the reduced Leff. The current work proposes a systematic methodology for optimizing length scalability for a given Lg that involves engineering of the lateral carrier profile. Unique lateral carrier profiles are extracted using contour maps of ΔL and RSD as a function of carrier profile parameters, and they are validated by comparing the measured Leff, drain‐to‐source resistance, and current‐voltage characteristics with the results of simulations using the extracted carrier profiles. Further, to overcome the trade‐off between enhanced mobility and degraded VT roll‐off that occurs with increasing carrier concentration, an IGZO TFT with gate‐insulator shoulders is fabricated to structurally form negative ΔL and physically increase Leff, while also obtaining a high carrier concentration, ultimately achieving both optimal electrical performance, with mobility of 17.50 cm2 V·s−1, and complete control of the electrostatic integrity of the gate.