Integrated Magnetic Sensing of Electrostatically Actuated Thin-Film Microbridges
- PDF / 223,537 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 72 Downloads / 165 Views
Integrated Magnetic Sensing of Electrostatically Actuated Thin-Film Microbridges J. Gaspar1,2, Haohua Li1,3, P.P. Freitas1,3, V. Chu1 and J.P. Conde2 1 Instituto de Engenharia de Sistemas e Computadores - Microsistemas e Nanotecnologias (INESC MN), Rua Alves Redol 9, 1000-029 Lisbon, Portugal 2 Department of Materials Engineering, Instituto Superior Técnico (IST), Av. Rovisco Pais, 1049001 Lisbon, Portugal 3 Physics Department, Instituto Superior Técnico (IST), Av. Rovisco Pais, 1049-001 Lisbon, Portugal
ABSTRACT Bilayer microbridges of aluminum and hydrogenated amorphous silicon are fabricated using thin film technology and surface micromachining at low temperatures on glass substrates. The microstructure is electrostatically actuated by applying a voltage between the bridge and a metal gate counter electrode placed beneath it. The movement is measured with a precision close to 0.1 Å by sensing the magnetic field of a permanent magnet, deposited and patterned on top of the microbridge, with an integrated spin valve magnetic sensor. The deflection of the bridge is at the same time monitored using an optical setup. The deflection of the structures is studied as a function of the driving applied gate voltage and bridge length and experimental results are analyzed with an electromechanical model.
INTRODUCTION Microelectromechanical systems (MEMS) use planar microelectronics fabrication techniques to produce three-dimensional structures, which have both electronic and mechanical functionality. Thus, MEMS technology allows the integration of mechanical actuation with sensing and control electronics, all integrated in a common technology [1]. Currently, most MEMS are made by bulk micromachining of crystalline silicon (c-Si) substrates or by surface micromachining of low-stress, high temperature polysilicon on a c-Si wafer substrate [2]. Thin film MEMS aims to exploit the advantages of thin film technology in the fabrication of MEMS on large area substrates such as glass and plastic. Because of the low temperature processing of most thin film processes, essentially any substrate can be used. Examples of thin film MEMS based-devices are silicon resonators on glass and plastic substrates [3] and bolometer arrays on silicon nitride/amorphous silicon/silicon nitride bridges [4]. Previous applications of magnetics to MEMS have been reported for actuators and detectors [5,6]. Magnetoresistive sensors [7] fabricated using thin film technology, such as spin valves (SV), are widely used as read heads in hard disk systems, in digital or analog position and speed sensors, and in current monitoring devices [8,9] and could be integrated in MEMS devices for sensing applications. This paper shows that is possible to monitor on chip the movement of thin film MEMS structures by using integrated SV magnetic sensors. This paper reports on the fabrication and characterization of electrostatically actuated thin film microbridges [10] with an integrated magnetic position sensing system. Applying an AC U3.7.1 Downloaded from https://www.cambri
Data Loading...
