Finite element simulation-based prediction of CMOS-compatible pyroelectric material in MEMS IR detectors

Abstract

Aluminum nitride (AlN) and zinc oxide (ZnO) have immensely drawn the interest of researchers as lead-free and CMOS-compatible materials for pyroelectric applications to replace the existing hazardous materials, namely lead zirconate titanate (PZT), lithium niobate (LiNbO3), and lithium tantalate (LiTaO3) in infrared (IR) detectors applications. This article uses the finite element method (FEM) to conduct a systemic investigation of a micro-electromechanical system (MEMS)-based pyroelectric IR detector using AlN or ZnO as the sensing material. The IR detector is designed over a 1 μm thin silicon dioxide diaphragm with a trapezoidal-shaped cavity of 300 μm depth in the silicon substrate to lower the detector's thermal mass and to increase the rate of change of temperature (dT/dt). The thickness and area of the pyroelectric layer were varied in the ranges of 0.5 to 5 μm and 0.16 to 3.24 mm2, respectively. The studies indicate that the AlN-based IR detector shows better performance than that of ZnO, with dT/dt ∼ 15.65 K/s, voltage responsivity (Rv) ∼ 62.52 V/W, noise equivalent power (NEP) ∼ 4.41 ×10−8 W/√Hz and specific detectivity (D*) ∼ 9.06 × 105 cm√Hz/W for a 0.16 mm2 area and 5 μm thick sensing layer.