Oxygen Content and Bias Influence on Amorphous InGaZnO TFT-Based Temperature Sensor Performance

Abstract

A temperature (T) sensor based on an amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) is demonstrated and its performance is analyzed quantitatively. The performance analysis includes the influences of the gateto-source bias (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> ) and oxygen content in IGZO on the mobility (μ), threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ), and drain-to-source current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> ) of TFTs. The linearity and sensitivity of the sensor are found to improve with decreasing oxygen content and increasing VGS, because ∂I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> /∂T is quantitatively-dominated by μ and (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> - VT) rather than by ∂μ/∂T and -∂V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> /∂T. This indicates that the IGZO TFT has great potential as a temperature sensor in terms of immunity in device/process variation. A sensitivity of 125 nA/K with 1.55 K resolution over a temperature range of 303-373 K was successfully demonstrated in low oxygen and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> = 9 V conditions.