High-Voltage a-IGZO TFTs With the Stair Gate-Dielectric Structure

In this work, a high-voltage amorphous In-Ga-Zn-O (a-IGZO) thin-film-transistors (TFTs) with the stair gate-dielectric at the drain side were demonstrated. The electrical properties of the proposed TFTs were comprehensively investigated. The breakdown voltage ( V
_BD
) was significantly enhanced, and the V
_BD
of over 60 V is achieved in the TFT with the stair length ( L
_stair
) of 3 μm. The TCAD simulation and emission microscope (EMMI) measurements are performed to reveal the working and breakdown mechanisms of the proposed stair gate-dielectric TFTs. The descending electron current density in the channel lowers the stair-gate TFTs' ON-current. Meanwhile, the stair-gate-dielectric region endures a strong electric field and improves the V
_BD
of the device. Finally, the exponential trade-off relationship between the V
_BD
and the ON-state resistance ( R
_ON
) was established.