Low temperature crystallization of amorphous silicon using an excimer laser |
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Authors: | R Z Bachrach K Winer J B Boyce S E Ready R I Johnson G B Anderson |
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Affiliation: | (1) Xerox Palo Alto Research Center, 3333 Coyote Hill Road, 94304 Palo Alto, CA |
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Abstract: | Low temperature processing is a prerequisite for compatible technologies involving combined a-Si and poly-silicon devices
or for fabricating these devices on glass substrates. This paper describes excimer-laser-induced crystallization of thin amorphous
silicon films deposited by plasma CVD (a-Si:H) and LPCVD (a-Si). The intense, pulsed UV produced by the laser is highly absorbed
by the thin amorphous material, but the average temperature is compatible with low temperature processing. The process produces
crystallites whose structure and electrical characteristics vary according to starting material and laser scan parameters.
The crystallized films have been principally characterized using x-ray diffraction, TEM, and transport measurements. The results
indicate that crystallites nucleate in the surface region and are randomly oriented. The degree of crystallization near the
surface increases as the doping level and/or deposited laser energy density is increased. The crystallite size increases with
a power law dependence on deposited energy, while the conductivity increases exponentially above threshold for unintentionally
doped PECVD films. The magnitude of the Hall mobility of the highly crystallized samples is increased by two orders of magnitude
over that of the amorphous starting material. |
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Keywords: | Low temperature processing a-Si excimer laser |
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