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Structure Sensitive Hydrogenation Effects in Polysilicon High Voltage thin Film Transistors

Published online by Cambridge University Press:  15 February 2011

F.J. Clough ,
Y.Z. Xu ,
E.M. Sankara Narayanan  and
R. Cross
F.J. Clough
Affiliation:
Emerging Technologies Research Centre, Department of Electrical and Electronic Engineering, De Montfort University, Leicester UK, fjclough@dmu.ac.uk.
Y.Z. Xu
Affiliation:
Emerging Technologies Research Centre, Department of Electrical and Electronic Engineering, De Montfort University, Leicester UK, fjclough@dmu.ac.uk.
E.M. Sankara Narayanan
Affiliation:
Emerging Technologies Research Centre, Department of Electrical and Electronic Engineering, De Montfort University, Leicester UK, fjclough@dmu.ac.uk.
R. Cross
Affiliation:
Emerging Technologies Research Centre, Department of Electrical and Electronic Engineering, De Montfort University, Leicester UK, fjclough@dmu.ac.uk.
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Abstract

Hydrogen passivation of grain boundary and in-grain defects is a key process step in the fabrication of high quality poly-Si TFTs. The sensitivity of the hydrogenation process to device geometry is therefore an important consideration. The effects of rf-plasma hydrogenation on the operating performance of a range of self-aligned and offset drain (Loff = 5 to 40 μm) poly-Si TFT configurations is reported. The hydrogenation of offset drain structures results in a predictable increase in the pre-threshold slope and a reduction in the device threshold voltage. However, extended hydrogenation (up to 12 h) can result in a significant reduction in the device drive current (by up to 2 orders). A similar effect is observed in metal field plate HVTFTs in which some portion of the offset region is un-modulated by the additional electrode. The on state conduction in the offset region is examined as a function of hydrogenation time, temperature and planar electric field. The increase in the on resistance is attributed to a reduction in the poly-Si defect density, which moderates carrier transport through the offset region.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 635
Copyright
Copyright © Materials Research Society 1999

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