Highly C-axis Aligned ALD-InGaO Channel Improving Mobility and Thermal Stability for Next-Generation 3D Memory Devices

Abstract

A way to obtain highly ordered and thermally stable crystalline In–Ga–O (IGO) thin films is reported by atomic layer deposition with novel bulky dimethyl[N-(tert-butyl)−2-methoxy-2-methylpropan-1-amine] gallium precursor. The optimal cation composition for IGO (In:Ga = 4:1 at%) shows a pronounced alignment along the high c-axis with cubic (222) orientation at a relatively low annealing temperature of 400 °C. Moreover, the crystallinity and oxygen-related defects persist even at elevated annealing temperatures of 700 °C. Owing to its well-aligned crystallinity, the optimal IGO thin film transistor demonstrates extremely high field-effect mobility (µFE) and remarkable thermal stability at high temperatures of 700 °C (µFE: 96.0 → 128.2 cm2 V−1s−1). Also, process-wise, its excellent step coverage (side: 96%, bottom: 100%), compositional uniformity in a 40:1 aspect ratio structure, superior crystal growth in vertical structures, and excellent reproducibility make it a promising candidate for application as a channel in next-generation 3D memory devices.