Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology
The integration of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with plastic substrates enables emerging technologies such as flexible organic light emitting diode (OLED) displays. Current a-Si fabrication processes, however, create residual thin film stress that affects the...
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ndltd-LACETR-oai-collectionscanada.gc.ca-OWTU.10012-56722014-06-18T03:51:13Z Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology Pathirane, Minoli thin-film transistor overlay alignment stress compensation The integration of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with plastic substrates enables emerging technologies such as flexible organic light emitting diode (OLED) displays. Current a-Si fabrication processes, however, create residual thin film stress that affects the underlying flexible substrate due to its high mismatch in the coefficient of thermal expansion resulting in a dimensional instability for fabricating TFTs on large area flexible substrates. The motivation of this thesis is to reduce this non-uniformity and improve fabrication throughput of bottom-gated inverted-staggered a-Si:H TFTs on flexible substrates. This thesis therefore encompasses the study of overlay misalignment on TFTs over 3 inch flexible substrates and investigates the electrical characteristics of the TFTs fabricated on plastic platforms. To reduce overlay misalignment of TFTs fabricated on flexible substrates, a plastic-on-carrier lamination process has been developed. The technique comprises of a polyimide tape to attach a 125 um-thick poly-ethylene-napthalate (PEN) flexible substrate to a rigid carrier. This process has been used to minimize stress induced strain of the PEN substrate during the fabrication process; strain, which has been observed after processing a-Si:H TFTs on free-standing substrates. This technique would in turn assist in fabricating uniform stacked-layers as required for a-Si:H TFT fabrication on the PEN substrates. Overlay misalignment is measured after each of the 5 consecutive lithographic steps at 4 corner-most edges of the PEN substrates using a standard optical microscope. Results have shown an overlay misalignment reduction from 21 um to 2 um on average based on the TFTs fabricated on free-standing flexible substrates while ensuring a centre alignment accuracy of +/- 0.5 um. Post fabrication adhesive removal to separate the PEN substrate from the rigid carrier has been accomplished by sample immersion in acetone. The results present a significant increase in fabrication throughput by reducing lithographic overlay misalignment such that the resolution of large-area flexible electronics would be enhanced. Electrical characteristics show the average performance of a-Si:H TFTs with an ON/OFF current ratio of 10^8, field effect mobility of ~0.8 cm^2/Vs, and gate leakage current of 10^-13 A. 2010-12-20T16:32:51Z 2010-12-20T16:32:51Z 2010-12-20T16:32:51Z 2010 2014-11-06T00:21:30Z Thesis or Dissertation http://hdl.handle.net/10012/5672 en |
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thin-film transistor overlay alignment stress compensation |
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thin-film transistor overlay alignment stress compensation Pathirane, Minoli Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology |
description |
The integration of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with plastic substrates enables emerging technologies such as flexible organic light emitting diode (OLED) displays. Current a-Si fabrication processes, however, create residual thin film stress that affects the underlying flexible substrate due to its high mismatch in the coefficient of thermal expansion resulting in a dimensional instability for fabricating TFTs on large area flexible substrates. The motivation of this thesis is to reduce this non-uniformity and improve fabrication throughput of bottom-gated inverted-staggered a-Si:H TFTs on flexible substrates. This thesis therefore encompasses the study of overlay misalignment on TFTs over 3 inch flexible substrates and investigates the electrical characteristics of the TFTs fabricated on plastic platforms.
To reduce overlay misalignment of TFTs fabricated on flexible substrates, a plastic-on-carrier lamination process has been developed. The technique comprises of a polyimide tape to attach a 125 um-thick poly-ethylene-napthalate (PEN) flexible substrate to a rigid carrier. This process has been used to minimize stress induced strain of the PEN substrate during the fabrication process; strain, which has been observed after processing a-Si:H TFTs on free-standing substrates. This technique would in turn assist in fabricating uniform stacked-layers as required for a-Si:H TFT fabrication on the PEN substrates. Overlay misalignment is measured after each of the 5 consecutive lithographic steps at 4 corner-most edges of the PEN substrates using a standard optical microscope. Results have shown an overlay misalignment reduction from 21 um to 2 um on average based on the TFTs fabricated on free-standing flexible substrates while ensuring a centre alignment accuracy of +/- 0.5 um. Post fabrication adhesive removal to separate the PEN substrate from the rigid carrier has been accomplished by sample immersion in acetone. The results present a significant increase in fabrication throughput by reducing lithographic overlay misalignment such that the resolution of large-area flexible electronics would be enhanced. Electrical characteristics show the average performance of a-Si:H TFTs with an ON/OFF current ratio of 10^8, field effect mobility of ~0.8 cm^2/Vs, and gate leakage current of 10^-13 A. |
author |
Pathirane, Minoli |
author_facet |
Pathirane, Minoli |
author_sort |
Pathirane, Minoli |
title |
Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology |
title_short |
Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology |
title_full |
Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology |
title_fullStr |
Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology |
title_full_unstemmed |
Improved Overlay Alignment of Thin-film Transistors and their Electrical Behaviour for Flexible Display Technology |
title_sort |
improved overlay alignment of thin-film transistors and their electrical behaviour for flexible display technology |
publishDate |
2010 |
url |
http://hdl.handle.net/10012/5672 |
work_keys_str_mv |
AT pathiraneminoli improvedoverlayalignmentofthinfilmtransistorsandtheirelectricalbehaviourforflexibledisplaytechnology |
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1716670090896736256 |