Effects of Annealing Atmosphere on the Characteristics and Optical Properties of SiON Films Prepared Plasma Enhanced Che
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Effects of Annealing Atmosphere on the Characteristics and Optical Properties of SiON Films Prepared Plasma Enhanced Chemical Vapor Deposition Ki-Jun Yun, Dong-Ryeol Jung, Sung-Kil Hong, Jong-Ha Moon, Jin-Hyeok Kim Center for Photonic Materials and Devices Department of Materials Science and Engineering, Chonnam National University 300 Yongbong-Dong, Puk-Gu, Kwangju 500-757, South Korea ABSTRACT SiON thin films were deposited by plasma-enhanced chemical vapor deposition method at 350 oC using N2O/SiH4 gas mixtures as precursors. As-deposited SiON films were annealed in different gas atmospheres (air, N2, and O2) and at different annealing temperatures (800 oC ~ 1100 oC). Effects of annealing atmosphere on the Si-O, Si-N, Si-H, and N-H bonding characteristics in SiON films and their structural and optical properties have been investigated. Cross-sectional and planar microstructures were characterized by scanning electron microscopy and atomic force microscopy, and crystallinity was investigated by X-ray diffraction. Chemical bonding characteristics and optical properties SiON films were studied using fourier transform infrared spectroscopy and prism coupler. Xray diffractions showed no evidence of any crystals in all SiON films. The deposition rate strongly depended on the processing parameters such as radio frequency (rf) power, N2O/SiH4 flow ratio, and SiH4 flow rate. Deposition rate increased as N2O/SiH4 flow ratio increased and SiH4 flow rate increased. It was possible to obtain SiON films with surface roughness of about 1 nm and a high deposition rate of about 4 µm/h when the processing parameters were optimized as rf power of 200 W, N2O/SiH4 flow ratio of 3, SiH4 flow rate of 100 sccm. It was observed that the intensity and the shift of the Si-O stretch and Si-N peaks depended on the annealing atmosphere as well as the annealing temperature. The intensity of Si-O peaks increased in the samples annealed in oxygen atmosphere, but it decreased in the samples annealed in nitrogen atmosphere. The intensity of Si-N peak decreased in the samples annealed in oxygen atmosphere, but it increased in the samples annealed in nitrogen atmosphere. The position of Si-O peaks shifted from 1030 nm to 1140 nm in the samples annealed both in oxygen and in nitrogen atmosphere. It was also observed that the intensities of Si-H (~2250 cm-1) and N-H (~3550 cm-1) peaks decreased apparently as the annealing temperature increased in all annealed samples.
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INTRODUCTION Planar optical waveguides have been received great interest in the fields of optical communication applications for many years by many companies and universities [1,2]. In the planar optical waveguide, the optically guiding core layer is sandwiched between a lower and an upper cladding layer. Generally, doping with Ge, P, or Ti is done to increase the refractive index of the core layer relative to the cladding layers. The relative difference of the refractive index between the core and the cladding layers is called “index contrast” and is an important par
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