Excess Oxygen Modulation Through Channel Thickness Scaling and Annealing Ambient for AlOx-Passivated Ultrathin InOx FETs

The role of excess oxygen in oxide-semiconductor channel in electrical and bias instability characteristics of AlOx-passivated ultrathin InOx FETs fabricated by plasma-enhanced atomic layer deposition is systematically studied with different channel thickness. The acceptor-like traps induced from excess oxygen, incorporated during deposition process or oxidizing annealing, degrades the instability in ultra-thin 1.8 nm InOx. Although annealing in N2 ambient can relieve the excess oxygen issue in a thin channel, it will lead to hump behavior due to the generation of inhomogeneous channel in a thicker InOx channel. While mobility increases in AlOx/InOx FETs after N2 annealing, a reduction is observed after O2 annealing at a same channel thickness due to a stronger scattering from traps. Afterall, it is still considered that using a thicker channel of 2.6 nm annealed by O2 ambient will be a better strategy for applying InOx channel into BEOL-transistors, from the perspective of Vth value (-1.2 V), mobility (32.1 cm2/Vs) and PBS instability (48 mV for 1-hour).