A Novel 3D Encapsulation Structure Based on Subwavelength Structure and Inserted Pyrex Glass for RF MEMS Infrared Detectors

Abstract

A novel wafer-level three-dimensional (3D) encapsulation structure was designed for radio-frequency microelectromechanical system (RF MEMS) infrared detectors and investigated by using the finite element method (FEM) simulation. A subwavelength structure with a circular array of coaxial apertures was designed to obtain an extraordinary optical transmission (EOT) on top of a silicon substrate. For perpendicular incident light, a maximum transmission of 56% can be achieved in the long-wave infrared (LWIR) region and the transmission bandwidth covered almost the full LWIR region. Moreover, the maximum transmission could be further promoted with an increase in the incident angle. The vertical silicon vias, insulated by inserted Pyrex glass, were used to generate electrical contacts. With the optimized structure parameters, a feed-through level lower than −82 dB, and a transmission coefficient of one single via of more than −0.032 dB were obtained at a frequency from 0 to 2 GHz, which contributed to the low-loss transmission of the RF signals. Due to the matched thermal expansion coefficients (TECs) between silicon and Pyrex glass, the proposed via structure has excellent thermal reliability. Moreover, its thermal stress is much less than that of a conventional through-silicon via (TSV) structure. These calculated results demonstrate that the proposed 3D encapsulation structure shows enormous potential in RF MEMS infrared detector applications.