Implementation of Fully Self-Aligned Homojunction Double-Gate a-IGZO TFTs

A simple method of fabricating fully self-aligned double-gate (SADG) homojunction a-IGZO TFTs is proposed and experimentally demonstrated for the first time. The self-alignment between the bottom- and top-gates is realized with one backside-illuminated photolithographic step; and that between the source/drain regions and the two gates is formed by both argon plasma treatment and hydrogen doping. The resulting overlap between the gate and source/drain regions is about 0.3 μm. Excellent symmetry between bidirectional transfer characteristics in the fabricated SADG TFTs is observed. Moreover, the dynamic threshold voltage operation is well demonstrated, and the driving capability, electrical stress effects under tied and separate gate biases are investigated.