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Laser Crystallized Polysilicon TFT'S Using LPCVD, PECVD and PVD Silicon Channel Materials-A Comparative Study

Published online by Cambridge University Press:  15 February 2011

R.T. Fulks ,
J. B. Boyce ,
J. Ho ,
G. A. Davis  and
V. Aebi
R.T. Fulks
Affiliation:
Xerox Palo Alto Research Center, Electronic Materials Laboratory, Palo Alto, CA 94304
J. B. Boyce
Affiliation:
Xerox Palo Alto Research Center, Electronic Materials Laboratory, Palo Alto, CA 94304
J. Ho
Affiliation:
Xerox Palo Alto Research Center, Electronic Materials Laboratory, Palo Alto, CA 94304
G. A. Davis
Affiliation:
Intevac Corporation, 3550 Basset Street, Santa Clara, CA 95054
V. Aebi
Affiliation:
Intevac Corporation, 3550 Basset Street, Santa Clara, CA 95054
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Abstract

In this work polysilicon TFI's were fabricated by excimer laser crystallization of active channel silicon which was deposited by three different methods: I) LPCVD at 550 °C; 2) PECVD at 225 °C; and 3) PVD at room temperature. CMOS devices were produced with the same low temperature (less than 600 °C) top gate process and the laser anneal condition was optimized for the material type and thickness. For PECVD material a pre-anneal step of 450 °C for 1 hour was required before crystallization to avoid bubbling and ablation due to hydrogen evolution, but no such anneal was required for either LPCVD or PVD material due to their low hydrogen and Ar content. For 50 nm films, laser energy densities were typically in the range of 300-400 miJ/cm2. Excellent device results were obtained for both LPCVD and PECVD material with n-channel field effect mobilities greater than 100 cm2/Vs and on/off ratios greater than 108 at 5 V drain bias. Good results were also obtained for PVD films that can be further improved by optimizing deposition and anneal conditions. In moving toward very low temperature polysilicon processing (less than 230 °C) both PECVD and PVD channel films appear to be viable candidates.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 623
Copyright
Copyright © Materials Research Society 1999

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