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A Semi-Insulating Layer for Novel High Voltage Polysilicon Thin Film Transistors

Published online by Cambridge University Press:  15 February 2011

F. J. Clough ,
Y. Chen ,
A. O. Brown ,
E. M. Sankara Narayanan  and
W. I. Milne
F. J. Clough
Affiliation:
Engineering Department, University of Cambridge, Cambridge CB2 1PZ, UK
Y. Chen
Affiliation:
Engineering Department, University of Cambridge, Cambridge CB2 1PZ, UK
A. O. Brown
Affiliation:
Engineering Department, University of Cambridge, Cambridge CB2 1PZ, UK
E. M. Sankara Narayanan
Affiliation:
Emerging Technologies Centre, De Montfort University, Leicester LEI 9BH, UK
W. I. Milne
Affiliation:
Engineering Department, University of Cambridge, Cambridge CB2 1PZ, UK
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Abstract

This work describes the deposition and characterisation of semi-insulating oxygen-doped silicon films for the development of high voltage polycrystalline silicon (poly-Si) circuitry on glass. The performance of a novel poly-Si High Voltage Thin Film Transistor (HVTFT) structure, incorporating a layer of semi-insulating material, has been investigated using a two dimensional device simulator. The semi-insulating layer increases the operating voltage of the HVTFT structure by linearising the potential distribution in the device offset region.

A glass compatible semi-insulating layer, suitable for HVTFT applications, has been deposited by the Plasma Enhanced Chemical Vapour Deposition (PECVD) technique from silane (SiH4), nitrous oxide (N2O) and helium (He) gas mixtures. The as-deposited films are furnace annealed at 600°C which is the maximum process temperature. By varying the N2O/SiH4 ratio the conductivity of the annealed films can be accurately controlled up to a maximum of around 10−7 Ω−1.cm−1 Helium dilution of the reactant gases improves both film uniformity and reproducibility. Raman analysis shows the as-deposited and annealed films to be completely amorphous. A model for the microstructure of these Semi-Insulating Amorphous Oxygen-Doped Silicon (SIAOS) films is proposed to explain the observed physical and electrical properties.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 377: Symposium A – Amorphous Silicon Technology 1995 , 1995 , 731
Copyright
Copyright © Materials Research Society 1995

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References

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