Laser Crystallization of Silicon Thin Films Using Photo Absorption Layer Formed by Spin Coating of Carbon Particles
- PDF / 109,949 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 88 Downloads / 178 Views
0958-L07-23
Laser Crystallization of Silicon Thin Films Using Photo Absorption Layer Formed by Spin Coating of Carbon Particles Nobuyuki Andoh1, Masato Maki1, Toshiyuki Sameshima1, and Naoki Sano2 1 Faculty of Technology, Tokyo University of Agri. and Tech., 2-24-16, Naka-cho, Koganei, Tokyo, Japan 2 Hightec Systems Corporation, Shin Yokohama No.2 Center BLDG. 7F, 3-19-5, Shin Yokohama, Kohoku-ku, Yokohama, Japan
ABSTRACT We report crystallization of amorphous silicon films 50~1400 nm thick formed on glass substrates by irradiation of an infrared semiconductor laser. Carbon particles with a mean diameter of 200 nm were uniformly coated on the silicon films as the optical absorption layer. Samples were irradiated with a 940-nm continuous wave (CW) semiconductor laser with a power of 20 W. A high optical absorbance 76.5% at 940 nm of the carbon particles layers resulted in annealing of silicon films by heat diffusion from the carbon particle layers. After removing the carbon particles layer, Raman scattering spectral measurements were carried out. A high scattering intensity and a sharp crystalline silicon phonon band were observed. The analysis of Raman spectra revealed a crystalline volume ratio almost 1.0. The analysis of the optical reflectivity spectra also revealed that the silicon films were crystallized in the whole thickness by the present method.
INTRODUCTION Polycrystalline silicon films have been applied to various kinds of devices such as thin film transistors (TFTs) and solar cells [1-3]. Laser crystallization processes using pulsed excimer laser have been widely adopted for the mass production of low temperature polycrystalline silicon (LTPS) TFTs for switching transistors of pixels and the peripheral driver circuits of liquid crystal displays (LCDs) [4-7]. However, thin silicon film has quite low optical absorbance in near infrared region. Infrared laser has not therefore been used for crystallization of silicon films. We have already reported silicon crystallization using diamond-like-carbon (DLC) films as photo-absorption layer by laser irradiation [8-12]. In this paper, we report the crystallization of silicon films by continuous-wave (CW)infrared-laser using the carbon particle layer as the photo absorption layer. We discuss the absorbance properties of carbon particle layer/a-Si:H/glass substrate structure. And we report the crystalline properties using Raman scattering spectra and the optical reflectivity spectra in the ultraviolet region.
EXPERIMENT Amorphous silicon films 50~1400 nm thick were deposited on the quartz glass substrate by a plasma enhanced chemical vapor deposition method with a mixture gas of SiH4 and H2. Carbon particles dispersed in water with concentration of 15 wt.% were then coated on the silicon films using spinner at a rotation speed of 5000 rpm. The mean diameter of carbon particle was about 200 nm. The optical transmissivity and reflectivity spectra were measured in order to estimate the optical absorbance of the carbon layer. CW semiconductor laser with a wavelengt
Data Loading...
