Abstract
We present a simple, accurate open-circuit sensitivity model based on both analytically calculated lumped and empirically extracted lumped-parameters that enables a capacitive acoustic sensor to be efficiently characterized in the frequency domain at the wafer level. Our mixed model is mainly composed of two key strategies: the approximately linearized electric-field method (ALEM) and the open- and short-calibration method (OSCM). Analytical ALEM can separate the intrinsic capacitance from the capacitance of the acoustic sensor itself, while empirical OSCM, on the basis of one additional test sample excluding the membrane, can extract the capacitance value of the active part from the entire sensor chip. FEM simulation verified the validity of the model within an error range of 2% in the unit cell. Dynamic open-circuit sensitivity is modelled from lumped parameters based on the equivalent electrical circuit, leading to a modelled resonance frequency under a bias condition. Thus, eliminating a complex read-out integrated circuit (ROIC) integration process, this mixed model not only simplifies the characterization process, but also improves the accuracy of the sensitivity because it considers the fringing field effect between the diaphragm and each etching hole in the back plate.
Highlights
Micro-electromechanical systems (MEMS) microphones have been technologically competitive based on the maturity of mass production technology
We present an efficient dynamic open-circuit sensitivity model mainly composed of both analytical approximately linearized electric-field method (ALEM)-based [9,15] and empirical open- and short-calibration method (OSCM)-based parameters [19] at the wafer level for a capacitive MEMS acoustic sensor
We demonstrated an electrical equivalent circuit-based dynamic open-circuit sensitivity model, which is based on both analytical ALEM-based and empirical OSCM-based parameters for a capacitive
Summary
Micro-electromechanical systems (MEMS) microphones have been technologically competitive based on the maturity of mass production technology. If the intrinsic capacitance in a capacitive-type acoustic sensor can be clearly modeled at the wafer level, the open-circuit sensitivity can be assessed without an ROIC connection in the frequency domain. Such studies have not been investigated in depth because of the complexity of parasitic capacitance modeling. We present an efficient dynamic open-circuit sensitivity model mainly composed of both analytical ALEM-based [9,15] and empirical OSCM-based parameters [19] at the wafer level for a capacitive MEMS acoustic sensor. The dynamic open-circuit sensitivity is evaluated from both theoretical and empirical parameters
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