Pyroelectric Thin Film Presence Detector Arrays with Micromachined Pixels

Abstract

Lately, pyroelectric thin film detectors gain in significance in the field of presence detection. In the paper, different variants of Pb(ZrTi)O 3 based detector arrays with 8 to 256 pixels are introduced. The sensing elements are arranged on thin micromachined SiO 2 /Si 3 N 4 membranes [1-4] as mechanical supporting structure with both low thermal mass and low heat conductivity into the substrate to achieve a high detectivity. For shaping these membrane structures, the most promising technology is micromachining, either from back or from surface of the silicon substrate. Self-polarized PZT thin films with a pyroelectric coefficient p up to 2.1 * 10 m 4 C/(m 2 K), dielectric loss tan i of less than 0.01 and a dielectric coefficient l r of about 250 are deposited in a multi-target sputtering process at comparatively low substrate temperatures of about 520°C. In the paper, presence detectors using thin film pyroelectric IR detector arrays as well as detector design, detector simulation, detector manufacturing and detector characteristics are discussed. In addition, pyroelectric material investigations and preparation of micromachined structures in combination with the back-end process of the pyroelectric active capacitor structure are presented.