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The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition.

Wang ZY, Zhang RJ, Lu HL, Chen X, Sun Y, Zhang Y, Wei YF, Xu JP, Wang SY, Zheng YX, Chen LY - Nanoscale Res Lett (2015)

Bottom Line: The surface topography investigated by atomic force microscopy (AFM) revealed that the samples were smooth and crack-free.It is found that the refractive index of Al2O3 thin films decrease with increasing film thickness and the changing trend revised after annealing.A thickness transition is also found by transmission electron microscopy (TEM) and SE after 900°C annealing.

View Article: PubMed Central - PubMed

Affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.

ABSTRACT
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°C annealing.

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The schematic of optical model used in SE fitting for Al2O3thin films.
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Fig1: The schematic of optical model used in SE fitting for Al2O3thin films.

Mentions: Considering the Si substrate always have a native oxide layer [21], the ellipsometric spectra were collected for the Si substrate with oxide layer and ALD-Al2O3 thin film, respectively. The RMS roughness obtained from AFM helps determining the thickness of roughness layer. So the optical model used in SE fitting is Si substrate/SiO2 layer/Al2O3 layer/surface roughness/air ambient, as shown in Figure 1. The dispersion model of Al2O3 used in SE fitting is Cauchy model [22].Figure 1


The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition.

Wang ZY, Zhang RJ, Lu HL, Chen X, Sun Y, Zhang Y, Wei YF, Xu JP, Wang SY, Zheng YX, Chen LY - Nanoscale Res Lett (2015)

The schematic of optical model used in SE fitting for Al2O3thin films.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384924&req=5

Fig1: The schematic of optical model used in SE fitting for Al2O3thin films.
Mentions: Considering the Si substrate always have a native oxide layer [21], the ellipsometric spectra were collected for the Si substrate with oxide layer and ALD-Al2O3 thin film, respectively. The RMS roughness obtained from AFM helps determining the thickness of roughness layer. So the optical model used in SE fitting is Si substrate/SiO2 layer/Al2O3 layer/surface roughness/air ambient, as shown in Figure 1. The dispersion model of Al2O3 used in SE fitting is Cauchy model [22].Figure 1

Bottom Line: The surface topography investigated by atomic force microscopy (AFM) revealed that the samples were smooth and crack-free.It is found that the refractive index of Al2O3 thin films decrease with increasing film thickness and the changing trend revised after annealing.A thickness transition is also found by transmission electron microscopy (TEM) and SE after 900°C annealing.

View Article: PubMed Central - PubMed

Affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.

ABSTRACT
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°C annealing.

No MeSH data available.


Related in: MedlinePlus