Effect of dopant redistribution in gate electrode on surface plasmon resonance in InGaZnO thin-film transistors

Abstract

<p> To study the effect of dopant redistribution at/near the gate-dielectric/gate-electrode interface during high-temperature processing on surface plasmon resonance in InGaZnO thin-film transistor, boron-doped Si wafers (resistivity = 0.02-0.021 omega.cm) are annealed in N2 at different temperatures (900, 1000, 1050, and 1100 ?C) to achieve lower surface doping concentrations via dopant out-diffusion and then used as the gate electrodes. Compared with the unannealed device, the devices fabricated on 900, 1050, and 1100 ?C-annealed wafers show lower carrier mobility because the reduced doping concentrations at/near their gate-dielectric/gate-electrode interfaces weaken the gate screening effect on the remote phonon scattering (RPS) of the gate dielectric on the neighboring channel electrons. However, the device annealed at 1000 ?C unexpectedly shows much lower carrier mobility. This result together with process simulation, Secondary Ion Mass Spectrometry analysis, and Fourier-transform infrared spectroscopy implies that the hole plasma at/near the surface of its p-Si gate electrode can oscillate with a frequency equal/close to the vibration frequency of the atoms in the gate dielectric, and the consequent surface plasmon resonance can greatly enhance the RPS to produce a large mobility reduction. In summary, for all the annealing temperatures, the mobility reduction caused by the lower gate-surface doping concentration indicates the larger impact of the holes at/near the gate-electrode surface than those in the gate-electrode bulk on the RPS. <br></p>