Achieving ultralow contact resistance and reducing residual hydrogen by surface doping

The proposed hypothesis suggests that a 30s hydrogen (H) plasma duration deposits a lower concentration of H as compared to the residual H in IGZO, thus restricting the diffusion of plasma deposited H towards IGZO and retaining it at the Mo/IGZO interface. [Display omitted] •Residual hydrogen (H) neither acts as a donor nor as a defect passivator in IGZO.•Hypothesis suggests that H applied by 30 s H plasma remains solely on the surface.•Surface H increases electron concentration at the Mo/IGZO interface.•Excess H leads to increased defects and Mo oxidation, raising IGZO resistances. Indium gallium zinc oxide (IGZO)-based materials and devices hold a significant position in integrated circuit manufacturing industries, yet challenges persist in controlling residual hydrogen and managing high source/drain contact resistance. Our proposed hypothesis not only targets the control of residual hydrogen through out-diffusion but also offers an opportunity for surface doping of IGZO, promising a substantial reduction in contact resistance. Interestingly, a 30 s hydrogen plasma deposition resulted in a lower hydrogen concentration compared to the residual hydrogen in IGZO, leading to increased carrier density at the interface. The higher carrier density, coupled with metallization-induced band bending at the interface, significantly lowers the Schottky barrier height and density of states, thereby facilitating sophisticated electron transport between molybdenum and IGZO. To the best of our knowledge, this study represents the first substantial reduction in residual hydrogen from IGZO films (initially deposited at 1020 cm−3, reduced to 1019 cm−3), while achieving ultralow specific contact resistivity (2.47 × 10-9 Ω•cm2) and sheet resistance (177.67 Ω/□). Our hypothesis introduces a novel strategy to reduce contact resistance in electronic devices.