YBaCuO uncooled microbolometer IRFPA

Abstract

Because the semiconducting YBaCuO films which are fabricated by sputtering have a temperature coefficient of resistance (TCR) over 3%/K at room temperature, they are considered to be candidates for bolometer materials of uncooled infrared (IR) detectors. There is a problem, however, in that the resistivity of the films is over 10 (Omega) cm, which is two orders of magnitude higher than that of conventional VO<SUB>X</SUB> bolometer films. To decrease the resistance of the bolometers, we researched sputtering conditions of the YBaCuO films and combined them with comb-shaped electrodes. When the YBaCuO film was deposited on these electrodes by RF magnetron sputtering at room temperature in an atmosphere of 2% O<SUB>2</SUB> and 98% Ar, it showed a resistivity of 90 &Omega;cm and a TCR of -3.2%/K; ultimately the YBaCuO bolometer resistance became 82 k(Omega) using the comb-shaped electrodes. The YBaCuO bolometer detector that contains an infrared absorbing membrane achieved a high fill factor of 90% and high infrared absorptance of 79%. Moreover, the detector showed a thermal conductance of 1.3x10<SUP>-7</SUP> W/K and a responsivity of 6.8x10<SUP>5</SUP> V/W in a vacuum. The YBaCuO microbolometer FPA which we have developed has an array format of 320x240 pixels and a pixel pitch of 40 &mu;m. The FPA showed a noise equivalent temperature difference (NETD) of 0.08 K with a prototype camera and f/1.0 optics.