Journal
NANOSCALE RESEARCH LETTERS
Volume 10, Issue -, Pages -Publisher
SPRINGEROPEN
DOI: 10.1186/s11671-015-0757-y
Keywords
ALD; Al2O3 thin film; Optical properties; Spectroscopic ellipsometry
Funding
- National Natural Science Foundation of China [11174058, 61275160, 11374055, 61427815]
- No. 2 National Science and Technology Major Project of China [2011ZX02109-004]
- STCSM project of China [12XD1420600]
- Key Laboratory of infrared imaging materials and detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences
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The aluminum oxide (Al2O3) thin films with various thicknesses under 50 nm were deposited by atomic layer deposition (ALD) on silicon substrate. The surface topography investigated by atomic force microscopy (AFM) revealed that the samples were smooth and crack-free. The ellipsometric spectra of Al2O3 thin films were measured and analyzed before and after annealing in nitrogen condition in the wavelength range from 250 to 1,000 nm, respectively. The refractive index of Al2O3 thin films was described by Cauchy model and the ellipsometric spectra data were fitted to a five-medium model consisting of Si substrate/SiO2 layer/Al2O3 layer/surface roughness/air ambient structure. It is found that the refractive index of Al2O3 thin films decrease with increasing film thickness and the changing trend revised after annealing. The phenomenon is believed to arise from the mechanical stress in ALD-Al2O3 thin films. A thickness transition is also found by transmission electron microscopy (TEM) and SE after 900 degrees C annealing.
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