Sputtering of self-polarized PZT films for IR-detector arrays

Within a 3-year project a pyroelectric detector array based on a tetragonal Pb(Zr,Ti)O₃ (PZT) thin film on a silicon substrate was developed. Compositions of about 25-30% Zr showed best properties for the application in pyroelectric sensing systems. For the film deposition, planar multi target sputtering from 3 metallic targets in a reactive Ar/O₂ mixture is used. The advantage of this method is that the perovskite phase can be grown down to relatively low substrate temperatures of about 500°C, a strong self polarization for compositions Zr/(Zr+Ti)<0.3 and a convenient control of the stoichiometry simply by varying the power supplied to the individual targets. The developed chip has (11×6) elements, his overall size is (8×4,7) mm². The array pixels of 280×280 μm ² have a noise equivalent power NEP of less than 0.7 nW at 1 Hz. The achieved specific detectivity D^* at a modulation frequency of 10 Hz is 3·10⁸ cm·Hz^1/2/W