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 −4 C/(m 2 K), dielectric loss tan δ of less than 0.01 and a dielectric coefficient ε r of about 250 are deposited in a multitarget 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.

Performance improvements for pyroelectric infrared detectors

“…The deposition of pyroelectric thin films on a thin silicon nitride / silicon oxide membrane has the advantage of high productivity since this allows the use of silicon technology procedures in wafer bonding. Tests with PVDF 5 und PZT 5,6 have shown that this technology can be used to manufacture single-element detectors. Owing to the detector parameters obtained, this method could not gain ground in the production of detectors.…”

Materials issues in thermal modeling of thin film electrocaloric solid-state refrigerators

“…For a cell stack, only the bottom and top cells should be thermally insulated to the environment by a layer of low thermal conductivity. Here, MEMS-structures consisting of vacuum cavities [69] or highly porous materials find application. At the top and bottom surfaces, an additional heat flux divider appears which lower the cooling power of the cell by a factor of The estimations made in this work illustrate that a solid state EC refrigerator with a cooling power of up to 2 W/cm 2 can be realized using a stack of 10 single MEMS-based cells.…”

Pyroelectric Arrays Using Ceramics and Thin Films Integrated Radiation Collectors: Design Fabrication and Testing

“…Workers have employed different strategies to obtain good thermal isolation. Koehler et al [13] have evacuated and sealed the cavity under the element. Other groups [11] evacuate the whole package and use long legs supporting the active element to provide the best possible thermal isolation.…”