Circuits and AMOLED display with self-aligned a-IGZO TFTs on polyimide foil

M. Nag, A. Bhoolokam, S. Smout, M. Willegems, R. Muller, K. Myny, S. Schols, M. Ameys, J. Genoe, T.H. Ke, P. Vicca, T.H. Ellis, B. Cobb, A. Kumar, J.L. van der Steen, G. Gelinck, Y. Fukui, K. Obata, G. Groeseneken, P. HeremansS. Steudel

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Abstract

A process to make self-aligned top-gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) on polyimide foil is presented. The source/drain (S/D) region's parasitic resistance reduced during the SiN interlayer deposition step. The sheet resistivity of S/D region after exposure to SiN interlayer deposition decreased to 1.5 kΩ/□. TFTs show field-effect mobility of 12.0 cm2/(V.s), sub-threshold slope of 0.5 V/decade, and current ratio (ION/OFF) of >107. The threshold voltage shifts of the TFTs were 0.5 V in positive (+1.0 MV/cm) bias direction and 1.5 V in negative (-1.0 MV/cm) bias direction after extended stressing time of 104 s. We achieve a stage-delay of ~19.6 ns at VDD = 20 V measured in a 41-stage ring oscillator. A top-emitting quarter-quarter-video-graphics-array active-matrix organic light-emitting diode display with 85 ppi (pixels per inch) resolution has been realized using only five lithographic mask steps. For operation at 6 V supply voltage (VDD), the brightness of the display exceeds 150 cd/m2. A process to make self-aligned top-gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) is presented. TFTs show field-effect mobility of 12.0 cm2/(V.s), sub-threshold slope of 0.5 V/decade, and current ratio (ION/OFF) of over 107. In applications, a 41-stage ring oscillator with a stage-delay of ~19.6 ns (at VDD = 20 V) and a top-emitting quarter-quarter-video-graphics-array (QQVGA) active-matrix organic light-emitting diode (AMOLED) display with 85 ppi (pixels per inch) resolution using five lithographic mask steps have been realized on a polyimide foil.

Original languageEnglish
Pages (from-to)509-517
Number of pages9
JournalJournal of the Society for Information Display
Volume22
Issue number10
DOIs
Publication statusPublished - 1 Oct 2014
Externally publishedYes

Keywords

  • a-IGZO
  • display technology
  • metal oxide
  • polyimide foil
  • self-aligned
  • TFT

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