Film-Profile Engineered InGaZnO Thin-Film Transistors with Self-Aligned Bottom Gates

We propose and demonstrate a method which combines film profile engineering (FPE) and a procedure of forming self-aligned bottom gates (SABGs) to fabricate InGaZnO thin-film transistors (TFTs). In the scheme, an ingenious etching procedure was implemented to form the final bottom gate self-aligned to the upper hardmask structure. The fabricated SABG devices show greatly reduced OFF-state leakage as compared with nonself-aligned ones, attributing to the reduction of gate-to-source/drain overlap areas which lowers both parasitic capacitance and gate leakage current. These merits benefit the operation of circuits consisted of TFTs implemented with FPE.