Fabrication of a New Pyroelectric Infrared Sensor Using MgO Surface Micromachining

Abstract
A new La-modified PbTiO3 (PLT) pyroelectric infrared sensor with a microcavity has been successfully fabricated by MgO surface micromachining. A microcavity under the sensing element is formed by etching the front surface of the substrate in order to improve the thermal properties. To precisely control the fabrication of a microcavity, process conditions were investigated in detail. As the concentration in phosphoric acid decreased and Pt diffusion into MgO substrate increased, the side etch rate of the MgO substrate increased from 1.9 to 3.4 µm/min at 80°C. The sizes of the fabricated sensor, sensing area, and etching holes were 1×2 mm2, 200×240 µm2, and 60×120 µm2, respectively. Pyroelectric coefficients of 4.0×10-8C/cm2 K were obtained.