Thermally Stable Crystalline InGaO Channels via Optimized ALD for Advanced DRAM Applications

Oxide semiconductors have gained considerable interest as potential materials to address the challenges posed by the scaling down of dynamic random-access memory devices. High-temperature stability is critical for the application of oxide semiconductors in memory devices, as maintaining a consistent crystal structure across varying annealing temperatures is essential for overcoming high-temperature instability. In this study, we propose an optimized crystalline InGaO (IGO) film for enhanced high-temperature stability by engineering atomic layer deposition process parameters, ozone concentration, and deposition temperature. Our results indicate that high-temperature stability can be achieved through increased ozone concentrations and deposition temperatures during IGO deposition. IGO deposited at 300 °C exhibited only slight changes in the main (222) intensity when annealed at 700 °C compared to 400 °C. Furthermore, a highly c-axis aligned (222) plane was observed. The field-effect transistor with an IGO active layer deposited at 300 °C showed minimal changes in electrical parameters after annealing at 700 °C (μFE: 58.4–68.7 cm2/(V s)) and demonstrated excellent positive bias temperature stress (PBTS) stability (ΔVTH: 0.15 V) at 3 MV/cm and 95 °C. These results suggest the potential of oxide semiconductors for use in memory devices with high-temperature thermal budgets.