超高真空退火處理原子層沉積氧化釔/砷化鎵-電性及介面特性研究

Abstract

In this experiment, ALD-Y2O3 was in-situ grown on freshly grown GaAs epi-layer, after GaAs wafer was transferred from MBE chamber via UHV modules. Epitaxial growth of ALD-Y2O3 was confirmed by Reflection High Energy Electron Diffraction (RHEED). Post deposition UHV-annealing process was carried out in an arsenic-free MBE chamber to attain a better interfacial quality. An ALD-Al2O3 film acted as a protecting layer against moisture from atmosphere. Systematic ex-situ annealing processes on the samples in He ambient showing that excellent C-V characteristics were preserved up to 930oC. Furthermore, different trends of C-V characteristics were observed between the He and N2 annealing at 900 oC. C-V and QSCV characteristics show lower frequency dispersion at accumulation and depletion region for the nitrogen annealing samples than the helium annealing samples. N-type MOSCAPs exhibited a small frequency dispersion of 10% in accumulation region after a 300oC 20min and 900oC 60s ex-situ annealing in nitrogen ambient and a post metallization annealing of 400oC 5min in forming gas environment. Furthermore, Dit spectrum extracted from QSCV method showed no peak profile near midgap, and Dit was given about 8×1011 eV-1cm-2 near midgap. Dit of 3×1011 eV-1cm-2 at around 1eV above valence band maximum was measured by conductance method. The high thermal stability and low interface trap density attained in this experiment make ALD-Al2O3/Y2O3/GaAs a promising candidate for application of next generation inversion channel MOSFETs.