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Intrinsic and Doped m c-Si:H TFT Layers using 13.56 MHz PECVD at 250°C

Published online by Cambridge University Press:  21 March 2011

Czang-Ho Lee ,
Denis Striakhilev  and
Arokia Nathan
Czang-Ho Lee
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
Denis Striakhilev
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
Arokia Nathan
Affiliation:
Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
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Abstract

Undoped and n+ hydrogenated microcrystalline silicon (μc-Si:H) films for thin film transistors (TFTs) were deposited at a temperature of 250°C with 99 ∼ 99.6 % hydrogen dilution of silane by standard 13.56 MHz plasma enhanced chemical vapor deposition (PECVD). High crystallinity m c-Si:H films were achieved at 99.6 % hydrogen dilution and at low rf power. An undoped 80 nm thick m c-Si:H film showed a dark conductivity of the order of 10−7 S/cm, the photosensitivity of an order of 102, and a crystalline volume fraction of 80 %. However, a 60 nm thick n+ μc-Si:H film deposited using a seed layer showed a high dark conductivity of 35 S/cm and a crystalline volume fraction of 60 %. Using n+ μc-Si:H films as drain and source contact layers in a-Si:H TFTs provides substantial performance improvement over n+ a-Si:H contacts. Finally, fully μ c-Si:H TFTs incorporating intrinsic m c-Si:H films as channel layers and n+ μc-Si:H films as contact layers have been fabricated and characterized. These TFTs exhibit a low threshold voltage and a field effect mobility of 0.85 cm2/Vs, and are far more stable under gate bias stress than a-Si:H TFTs.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 808: Symposium A – Amorphous and Nanocrystaline Silicon Science and Technology-2004 , 2004 , A4.14
Copyright
Copyright © Materials Research Society 2004

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References

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