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The Kinetics of Removal of Defects in a-Si:H TFTs Made with PECVD Oxide Gate Insulator Material

Published online by Cambridge University Press:  16 February 2011

P. N. Morgan ,
W. I. Milne ,
S. C. Deane  and
M. J. Powell
P. N. Morgan
Affiliation:
Engineering Department, Cambridge University, Cambridge CB2 1PZ, UK
W. I. Milne
Affiliation:
Engineering Department, Cambridge University, Cambridge CB2 1PZ, UK
S. C. Deane
Affiliation:
Philips Research Labs., Redhill, Surrey RH1 5HA, UK.
M. J. Powell
Affiliation:
Engineering Department, Cambridge University, Cambridge CB2 1PZ, UK
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Abstract

AMorphous silicon thin film transistors may be manufactured using a variety of gate insulator Materials. The sign and magnitude of the fixed charge, Qf, in the gate insulator material determines the as-deposited density of states in the a-Si:H as predicted by the defect pool Model [1]. For the case of PECVD nitride Qf is positive giving rise to a defect peak in the lower part of the bandgap. In thermal oxide, which has small negative Qf the states are in the upper part of the bandgap. Using the technique of low temperature bias stress or high temperature bias anneal it is possible to create further defects in the bandgap on top of those already present, facilitating the study of upper (Dh) and lower (De) gap states. In a previous work we studied the removal kinetics of such defects using TSDR (Thermally Stimulated Defect Removal) in both PECVD nitride and thermal oxide devices [2]. Here we repeat the experiments on thin film transistors made with PECVD helium diluted oxide as the gate insulator Material. PECVD helium diluted oxide is interesting as its Qf May be varied during Manufacture. Thus TFTs with characteristics similar to either thermal oxide or PECVD nitride can be obtained.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 336: Symposium A – Amorphous Silicon Technology - 1994 , 1994 , 811
Copyright
Copyright © Materials Research Society 1994

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References

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