A novel self-aligned etch stopper structure with lower photo leakage for AMLCD applications

We introduce a novel self-aligned etch stopper, sidewall-contact a-Si:H TFT (ESSC-TFT) which allow us to reduce the photo leakage current by the island-in structure. This ESSC-TFT design reduces the volume of a-Si film, the active region can totally be shielded by the gate metal resulting in the prevention from direct back light illumination. With the sidewall-contact, the hole current is reduced due to the smaller contact area, and we expect the source, drain parasitic intrinsic resistance of a-Si can be also lessened by the ESSC-TFT structure. Although the defects between etched a-Si and n⁺ a-Si film may degrade the on current, the ESSC-TFT still exhibits higher on-off ratio than the one in traditional ES-TFT structure.