Modulating Thin Film Transistor Characteristics by Texturing the Gate Metal

Aswathi Nair,Prasenjit Bhattacharya,Sanjiv Sambandan

doi:10.1038/s41598-017-18111-5

Aswathi Nair, Prasenjit Bhattacharya + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-18111-5

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Abstract

The development of reliable, high performance integrated circuits based on thin film transistors (TFTs) is of interest for the development of flexible electronic circuits. In this work we illustrate the modulation of TFT transconductance via the texturing of the gate metal created by the addition of a conductive pattern on top of a planar gate. Texturing results in the semiconductor-insulator interface acquiring a non-planar geometry with local variations in the radius of curvature. This influences various TFT parameters such as the subthreshold slope, gate voltage at the onset of conduction, contact resistance and gate capacitance. Specific studies are performed on textures based on periodic striations oriented along different directions. Textured TFTs showed upto ±40% variation in transconductance depending on the texture orientation as compared to conventional planar gate TFTs. Analytical models are developed and compared with experiments. Gain boosting in common source amplifiers based on textured TFTs as compared to conventional TFTs is demonstrated.

Highlights

An important consideration for good circuit design is the ability to control the transconductance of the thin film transistors (TFTs)
Sambandan found that creating periodic corrugations on the gate metal and thereby influencing the metal-insulator-semiconductor stack influenced the performance of TFTs45
Rex et al found that such patterning could either enhance or degrade TFT performance depending on the geometry which in turn influenced the effective insulator capacitance[47]

Summary

Gate Metal

The development of reliable, high performance integrated circuits based on thin film transistors (TFTs) is of interest for the development of flexible electronic circuits. To achieve a small signal gain of G > 1 the layout area of the circuit will have to scale by a factor of 2G (increasing channel width of the driver and channel length of the load simultaneously) thereby reducing spatial resolution This would increase the gate-drain overlap capacitance of the drive TFT by a factor of G and increase the input Miller capacitance by a factor of G2 resulting in a stronger pole at the input. In this work we investigate the modulation of TFT transconductance by the purely geometrical approach of texturing of the gate metal resulting in non-planar metal-insulator-semiconductor stacks. This interaction between geometry and functionality has strong applications. The concept of texture based gain control in TFT voltage amplifiers is demonstrated

Results and Discussions

Conclusion

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