Cocktail Precursor Approach for Homogeneous ALD InGaO Film Growth Overcoming Limits of Mobility–Reliability Trade-Off in Oxide Semiconductors

Abstract

Crystalline indium gallium oxide (IGO) semiconductors have attracted considerable attention as promising channel materials for high-performance field-effect transistors (FETs) because of their excellent thermal stability and high field-effect mobility. In this study, we report a cocktail precursor strategy based on a 3:1 molar mixture of an In precursor (DMITN) and a Ga precursor (DMGTN) for uniform and efficient atomic layer deposition (ALD) of multicomponent oxide thin films. Thermal analyses confirmed the homogeneous behavior and thermal stability of the cocktail precursor. ALD growth characterization demonstrated self-limiting surface reactions and increased deposition efficiency compared with the conventional supercycle process. The resulting IGO films deposited using the cocktail precursor exhibited a homogeneous cation distribution throughout the bulk region, leading to improved crystallographic alignment after annealing at 400 °C. Structural analyses revealed a strong out-of-plane orientation along the cubic (222) plane, which contributed to reduced oxygen-related defects and suppressed subgap state density. Compared to IGO films grown via the supercycle method, the cocktail precursor-derived IGO channel FET exhibited a 28% increase in field-effect mobility (61.8 cm2/V·s), lower trap densities, and superior stability under positive-bias temperature stress (2 MV/cm at 60 °C for 1 h). Excellent reproducibility was also confirmed across the entire 4-inch wafer. These results demonstrate that the cocktail precursor approach provides a promising solution for overcoming the mobility–reliability trade-off in oxide semiconductors by enabling compositionally homogeneous and structurally well-ordered films. This approach is suitable for high-performance oxide semiconductor devices.