Abnormal Dual Channel Formation Induced by Hydrogen Diffusion from SiN _x Interlayer Dielectric in Top Gate a-InGaZnO Transistors

This letter investigates effects of different channel dimensions in top-gate a-InGaZnO ₄ thin-film transistors with SiN _x interlayer dielectric. In narrow channel devices, hydrogen atoms in the SiN _x layer diffuse into the entire active layer, inducing a single channel. However, in wider channel devices, the diffusion distance for hydrogen atoms is insufficient to affect the whole channel, instead inducing a double channel. In addition, under hot carrier stress, narrow and wide channels exhibit different degradation behaviors, with simulations showing a strong electrical field at IGZO near the drain terminal of the main channel, which is unaffected by hydrogen.