Film-profile-engineered ZnO thin-film transistor with gate/drain offset for high-voltage operation

Abstract

We report the design and fabrication of ZnO thin-film transistors (TFTs) configured with designed gate-to-drain (G/D)-offset structures and an auxiliary gate (AG) in a film-profile engineering (FPE) approach for back-end-of-line high-voltage (HV) operation. The breakdown voltage (V-BD) of fabricated FPE TFTs is significantly enhanced from 23 to 90 V by changing the G/D-offset length from -0.3 to 0.5 mu m, whereas there is a corresponding decrease in the on-state current and transconductance (G(m)). To boost the on-state current, an AG biased in the range of 0-5 V is designed to effectively modulate the resistivity of the G/D-offset region and improve G(m) by a factor of 2 while keeping V-BD of 65-70 V nearly unchanged. Output characteristics with drain voltage as high as 60 V have been demonstrated, evidencing the promising potential of the ZnO TFTs for HV device applications. (C) 2019 The Japan Society of Applied Physics