A thermosensitive electromechanical model for detecting biological particles

Miniature electromechanical systems form a class of bioMEMS that can provide appropriate sensitivity. In this research, a thermo-electro-mechanical model is presented to detect biological particles in the microscale. Identification in the model is based on analyzing pull-in instability parameters and frequency shifts. Here, governing equations are derived via the extended Hamilton’s principle. The coupled effects of system parameters such as surface layer energy, electric field correction, and material properties are incorporated in this thermosensitive model. Afterward, the accuracy of the present model and obtained results are validated with experimental, analytical, and numerical data for several cases. Performing a parametric study reveals that mechanical properties of biosensors can significantly affect the detection sensitivity of actuated ultra-small detectors and should be taken into account. Furthermore, it is shown that the number or dimension of deposited particles on the sensing zone can be estimated by investigating the changes in the threshold voltage, electrode deflection, and frequency shifts. The present analysis is likely to provide pertinent guidelines to design thermal switches and miniature detectors with the desired performance. The developed biosensor is more appropriate to detect and characterize viruses in samples with different temperatures

Materials issues in the processing, the operation and the reliability of MEMS

In this article materials issues that arise during the processing and operation of micro-electro mechanical systems devices (MEMS), and their impact on the functionality and reliability, are discussed. The article starts with the example of an RF-MEMS switch process flow, indicating how and why certain materials are chosen. Then two specific MEMS materials issues, e.g. stiction and stress, are covered. Finally, the so-called 'zero-level' packaging of MEMS as well as the effect packaging can have on the device and its operation will be reviewed. © 2004 Elsevier B.V. All rights reserved.status: publishe

A new characterization method for electrostatically actuated resonant MEMS: Determination of the mechanical resonance frequency, quality factor and dielectric charging

In this paper, a novel technique to characterize MEMS is described. The technique is based on electric admittance measurements of electrostatically actuated MEMS. It is capable of determining a number of characteristic parameters such as the unbiased (or true mechanical) resonance frequency, the unbiased quality factor and the residual voltage associated with dielectric charging. These parameters are extracted from the admittance measurements in a two-step computation procedure. They may serve as monitors of both mechanical and electrical changes in tested devices, which makes this technique an excellent tool for reliability assessment of various types of electrostatically driven MEMS. (C) 2008 Elsevier B.V. All rights reserved.status: publishe

Wafer-level thin film vacuum packages for MEMS using nanoporous anodic alumina membranes

This paper reports on a wafer-level thin film vacuum packaging technology for MEMS. It is based on the fabrication of freestanding porous anodic alumina membranes of a typical thickness of 2 to 3 μm, featuring cylindrical nanopores that are a mere 15-20 nm in diameter (aspect ratio >100). The fabrication process involves in situ perforation of the thin AlOₓ barrier layer present at the bottom of the nanoporous membranes. For the present paper, a silicon oxide sacrificial layer and a vapor-phase HF release etch through the pores are utilized. The thin film packages are next sealed with a 4 μm-thick PECVD nitride layer. Strong and “air-tight” thin film packages are obtained this way. Negligible impact on the RF transmission losses (up to 67 GHz) is observed. A basic assessment of the package hermeticity based on the cap deflection method is also presented.status: publishe

Wafer scale fabrication of miniature vacuum packages for MEMS/NEMS using thin membranes of nanoporous alumina

poster + abstractstatus: publishe

MEMS packaging and reliability: An undividable couple

This paper reviews various approaches to package MEMS, illustrated mainly with examples from imec. Wafer-level or 0-level packaging is mostly dealt with. The role the package plays in achieving the required performance and reliability characteristics is elucidated. Package requirements, such as hermeticity and strength, are named, discussed and illustrated with examples. Considerations of reliability testing are presented. It is made conceivable that vacuum maintenance of tiny MEMS packages is a dominant reliability issue, something not at all obvious to achieve. © 2012 Elsevier Ltd. All rights reserved.status: publishe