Controllability of self-aligned four-terminal planar embedded metal double-gate low-temperature polycrystalline-silicon thin-film transistors on glass substrate

Self-aligned four-terminal n-channel (n-ch) and p-channel (p-ch) planar embedded metal double-gate polycrystalline-silicon thin-film transistors (TFTs) were fabricated on a glass substrate at a low temperature of 550 °C. This device includes a metal top gate (TG) and a metal bottom gate (BG), which are used as the drive and control gates, or vice versa. The BG was embedded in a glass substrate, and a poly-Si channel with large lateral grains was fabricated using continuous-wave laser lateral crystallization. The threshold voltage modulations under various control gate voltages (γ = ΔV_th/ΔV_CG) were nearly equal to the theoretical predictions in both the n-ch and p-ch TFTs. By using this high controllability, an E/D inverter was fabricated, and successful operation at V_dd = 2.0 V was confirmed.