Pyroelectric devices based on sputtered PZT thin films

Abstract

After a short description of thermal conditions in a pyroelectric sensor, substantial requirements to pyroelectric thin film and sensor design are derived from the theoretical basics. A planar multi-target sputtering process is used to deposit PZT thin films for application in pyroelectric IR sensors. The self-polarized PZT are characterized by a pyroelectric coefficient p of 2-10−4 Cm−2K−1, a dielectric constant [Sgrave] of 300 and a dielectric loss tan δ of 0.01. These material properties, including a low tensile stress of the sensor layer stack of + 110 Mpa, as well as standard microelectronic technologies make the films suitable for the use in pyroelectric sensor arrays. Fabricated singleelement sensors have a specific detectivity D* (500K, 10 Hz) of 3.108 cmHz1/2W−1. An 11×6 array sensor has been developed for motion detection. The array pixels with a sensitive area of 0.0784 mm2 have a noise equivalent power NEP of less than 0.7 nW at 1 Hz.