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Amorphous IGZO TFTs and Circuits on Highly Flexible and Dimensionally Stable Kovar (Ni-Fe alloy) Metal Foils

Published online by Cambridge University Press:  22 September 2011

Shahrukh A. Khan
Affiliation:
Department of Electrical Engineering, Lehigh University, Bethlehem, PA 18015
Xiaoxiao Ma
Affiliation:
Department of Electrical Engineering, Lehigh University, Bethlehem, PA 18015
Nack Bong Choi
Affiliation:
Department of Electrical Engineering, Lehigh University, Bethlehem, PA 18015
Miltiadis Hatalis
Affiliation:
Department of Electrical Engineering, Lehigh University, Bethlehem, PA 18015
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Abstract

We have fabricated high performance amorphous IGZO TFTs and integrated circuits on flexible kovar (Ni-Fe 42 alloy) foils. Excellent dimensional stability on kovar foils is obtained by a pre-anneal process at 800°C that limits the thermal run-out to within 100ppm. After substrate annealing, Ni-Fe 42 alloy retains high yield strength and good flexibility with the re-crystallized structure containing large isotropic grains between 20-50μm. Amorphous IGZO TFTs and circuits with a staggered, bottom-gate architecture are fabricated and tested. Non-flexed TFTs have field effect mobility of 12 cm2/V.s, threshold voltage around 2 V and sub-threshold swing of 0.6 V/decade and ON/OFF current ratio exceeding 107. Under prolonged uniaxial tensile strain upto 0.8%, TFTs exhibited minimal change in performance which augers well for use of Ni-Fe foil as flexible substrates. To demonstrate the viability of oxide-based device integration, n-type pseudo logic ring oscillator circuits are also evaluated. Sub 300 ns propagation delay is confirmed at a rail-rail supply voltage of 40 V. The results suggest that device integration on such a highly flexible substrate is amenable to roll-to-roll processing of future electronics.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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References

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