Low-Voltage Thin Film Transistors

“Thin-film oxide semiconductors are regarded as the most profound breakthrough in the electronics industry since silicon transistors. Here is a revolutionary route for manufacturing low-voltage Thin Film Transistors at reduced cost and higher yield”


Background

Flexible, wearable electronic devices will offer new opportunities for improved connectivity, smart objects and healthcare. The fulfilment of such devices is contingent upon reducing the power consumption of the electronics so that the device is easily powered by a battery. However, reducing the power consumption of thin-film transistors – one of the fundamental components of flexible electronics – while maintaining high yields and low costs has proved difficult.

A research team at The University of Manchester has developed a method to produce such low voltage semiconductors using a solid-state electrolyte dielectric deposited by sputtering. The high capacitance of the dielectric – a result of ionic conduction – allows for low voltage device operation. While other techniques reduce the dielectric thickness to achieve high capacitance – sacrificing the quality of the insulating behaviour – the ionic conduction in the solid-state electrolyte enables thick dielectric layers to maintain high capacitance and thus low voltage operation.

The Benefits

  • The ability to operate at lower voltage and lower noise levels than conventional TFTs.
  • Lower production costs and higher yields, making larger displays and sensors more economical.
  • Lower operating voltages allows displays and sensors to operate for longer on battery operation.
  • Lower noise expands the range over which these sensors can operate.
  • Inherent flexibility allows use in wearable and other flexible applications.
  • Highly uniform pinhole-free dielectric (low leakage current).
  • High sensitivity to pH and humidity for sensing purposes.
  • Compatible with current industry processing techniques.
  • Highly transparent.
  • Room temperature deposition, compatible with flexible substrates.


The Technology

The invention is a method for manufacturing Thin Film Transistors operating at less than 1 V. This technology offers a means of producing low voltage devices at reduced cost and improved yield using existing processes and will find application in several fields, including displays, sensors and wearables. The technology is particularly suitable for large-area manufacturing of thin-film electronics.


Figure 1: Transfer curve of TFT with a sputtered SiO2 dielectric demonstrating 1 V operation. Device structure inset.

The solid-state electrolyte is a sputtered SiO2 layer with the following properties:

Transmittance: ≥ 90% for visible wavelengths (200 nm thick SiO2 layer)
Capacitance per unit area: 0.45 μF cm−2 at 20 Hz; 0.2 μF cm−2 at 1 kHz

Typical device performance:

On/Off current ratio: > 105
Subthreshold swing: < 90 mV/dec
Cut-off frequency: fT = 4 kHz at VD = 0.1 V
fT = 64 kHz at VD = 1 V

Opportunity

UMIP is seeking interest from companies operating in relevant sectors for discussions about collaboration and licensing.

 

UMIP Contact

Commercial enquiries about TFTs should quote Opportunity No. 20160170 and be addressed to:

Simon Clarke, IP Development and Partnering Manager
UMIP, Core Technology Facility, 46 Grafton Street, Manchester M13 9NT
E: simon.clarke@umip.com / T: 44 (0) 161 306 8510

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