Stability Behavior of Self-Aligned Coplanar a-IGZO Thin Film Transistors Fabricated by Deep Ultraviolet Irradiation

We fabricated self-aligned coplanar amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs and defined the source/drain region using deep ultraviolet (DUV) irradiation. For our TFTs, source/drain region were well defined to designed dimensions and contact resistance was low value. The electrical properties of the device show field-effect mobility (μFE) of 13.2 cm2/Vs, subthreshold swing (S/S) of 0.32 V/decade, threshold voltage (Vth) of 3.2 V, and on/off ratio of 8.8 × 108, respectively. In addition, the reduced channel length (ΔL) and width-normalized contact resistance (RSDW) were 1.08 μm and 87.5 Ω cm, respectively. Stability behavior of self-aligned coplanar a-IGZO TFT fabricated by DUV irradiation was investigated under negative bias stress (NBS), negative bias illumination stress (NBIS), positive bias stress (PBS), and positive bias temperature stress (PBTS). After the stress under NBS, NBIS, PBS, and PBTS, the Δ Vthvalues of −0.3 V, −0.8 V, 1.2 V, and 1.3 V were measured, respectively. Additionally, the electrical characteristics of the n+ doping region by DUV irradiation were not degraded under any of the stress conditions.