Self-aligned amorphous silicon thin film transistors with mobility above 1 cm2V-1s-1 fabricated at 300° C on clear plastic substrates

Kunigunde H. Cherenack, Alex Z. Kattamis, Bahman Hekmatshoar, James C. Sturm, Sigurd Wagner

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


We have developed a fabrication process for amorphous-silicon thin-film transistors (a-Si:H TFTs) on free-standing clear plastic substrates at temperatures up to 300°C. The 300°C fabrication process is made possible by using a unique clear plastic substrate that has a very low coefficient of thermal expansion (CTE < 10ppm/°C) and a glass transition temperature higher than 300°C. Our TFTs have a conventional inverted-staggered gate back-channel passivated geometry, which we designed to achieve two goals: accurate overlay alignment and a high effective mobility. A requirement that becomes particularly difficult to meet in the making of TFT backplanes on plastic foil at 300°C is minimizing overlay misalignment. Even though we use a substrate that has a relatively low CTE, accurately aligning the TFTs on the freeostanding, 70-micrometer thick substrate is challenging. To deal with this immediate challenge, and to continue developing processes for free-standing web substrates, we are introducing techniques for self-alignment to our TFT fabrication process. We have self-aligned the channel to the gate by exposing through the clear plastic substrate. To raise the effective mobility of our TFTs we reduced the series resistance by decreasing the thickness of the amorphous silicon layer between the source-drain contacts and the accumulation layer in the channel. The back-channel passivated structure allows us to decrease the thickness of the a-Si:H active layer down to around 20nm. These changes have enabled us to raise the effective field effect mobility on clear plastic to values above 1 cm2V-1s-1

Original languageEnglish (US)
Title of host publicationAmorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2008
PublisherMaterials Research Society
Number of pages6
ISBN (Print)9781605110363
StatePublished - 2008
Event2008 MRS Spring Meeting - San Francisco, CA, United States
Duration: Mar 25 2008Mar 28 2008

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Other2008 MRS Spring Meeting
Country/TerritoryUnited States
CitySan Francisco, CA

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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