Micro-machined Pyroelectric Infrared Detector Based on Sol-gel Derived Pb(Zr_(0.3)Ti_(0.7)O_3/PbTiO_3 Multilayer Thin Films

摘要

A sol-gel derived Pb(Zr_(0.3)Ti_(0.7)O_3/PbTiO_3 (PZT/PT) multilayer thin film structure has been studied for the application of infrared detection. Compared to the pure Pb(Zr_(0.3)Ti_(0.7))O_3 (PZT) thin film deposited by the same process, the multilayer thin film shows a lower dielectric constant and similar pyroelectric coefficient and dielectric loss. The detectivity figures of merit for the PZT/PT and PT thin films are 20.3 * 10~(-6) Pa-1/2 and 18.7 * 10~(-6) Pa~(-1/2), and values of voltage response figures of merit are 0.038 m~2/C and 0.028 m~2/C, respectively. The results show that the multilayer PZT/PT film is a better choice for pyroelectric infrared detection. Pyroelectric infrared detectors have been successfully developed based on the multilayer PZT/PT thin film. A silicon bulk-machined thermal isolation structure has been applied to reduce thermal loss from the sensing thin film to the Si substrate. To evaluate the detector performance and to aid in the thermal structure design, finite element analysis (FEA) of the detector in terms of heat transfer has been carried out by using a software package "ANSYS". The detector response has been characterized by a modified Chynoweth system. At 7 Hz, the dynamic pyroelectric voltage responsivity is measured to be 108 V/W (in rms) with the sensing element size of 240 * 360 μm~2. The measured results are consistent with the simulated results.