Mobility and Threshold Voltage Co‐Optimization of IGZO Field‐Effect Transistor with Ideal Subthreshold Swing through Atomic Layer Growth Control

ABSTRACT IGZO has been identified as a promising channel material for next‐generation memory integration. Although extensive studies have been carried out to optimize the electric transport properties, the trade‐off between mobility and threshold voltage remains to be challenging. Furthermore, the subthreshold swing often degrades at more positive threshold voltages. Atomic layer deposition (ALD) offers the unique capability to control the layer composition and element arrangement at the atomic level with additional tunability from supercycle growth conditions at different temperatures. This work employs a supercycle thermal ALD method for IGZO deposition and systematically investigates the influence of deposition temperatures and compositions on the electrical characteristics of IGZO FETs. The results reveal that increasing the deposition temperature enhances the surface reactions of metal precursors, reducing carbon residues substantially in the IGZO channel, with the M‐O peak proportion reaching 89.8% at 300°C and oxygen‐related impurities decreasing to 4.1%. Furthermore, as the In2O3 sub‐cycle varies from 5 to 1, the ratio of oxygen vacancies decreases from 21.0% to 8.6%, with a widely tunable threshold voltage from −2 to +2.3 V. It should be noted that the mobility with the most positive threshold voltage of 2.3 V still exceeds 15 cm2 V−1 s−1. Furthermore, the subthreshold slope of the optimized transistors keeps under 65 mV dec−1 for the entire range of threshold voltages and can reach the ideal value of 60 mV dec−1 for Vth near 0.5 V. This work provides valuable insights into co‐optimizing mobility and Vth while keeping low SS by tuning the ALD growth parameters for IGZO.