Fabrication Challenges for Realization of Wet Etching Based Comb Type Capacitive Microaccelerometer Structure

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Fabrication Challenges for Realization of Wet Etching Based Comb Type Capacitive Microaccelerometer Structure Powered By Docstoc
					                   Sensors & Transducers Journal, Vol. 111, Issue 12, December 2009, pp. 18-24


                                                       Sensors & Transducers
                                                                                           ISSN 1726-5479
                                                                                            © 2009 by IFSA
                                                                               http://www.sensorsportal.com




  Fabrication Challenges for Realization of Wet Etching Based
     Comb Type Capacitive Microaccelerometer Structure
    Shankar DUTTA, R. PAL, P. KUMAR, O. P. HOODA, J. SINGH, Shaveta,
              G. SAXENA, P. DATTA and 1R. CHATTERJEE
           Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi -110054, India
                   1
                     Physics Dept., IIT Delhi, Hauz Khas, New Delhi -110016, India
                             Tel.: +91-1123971743, fax: +91-1123913609
                                    E-mail: shankardutta77@gmail.com


    Received: 23 October 2009 /Accepted: 22 December 2009 /Published: 30 December 2009


Abstract: The current paper presents fabrication of wet etching based comb-type microaccelerometer
structure consisting of 47 interdigitated fingers attached to a large proof mass, which is suspended by
two narrow torsional beams. Silicon (< 110 >, p-type) was oxidized and the microaccelerometer
structure was patterned by photolithography. Desired device thickness was achieved by combination of
wet anisotropic etching of 15μm depth and formation of 12μm thick p++ etch stop layer. Pits of 15μm
were formed in Pyrex glass and metallic lines with bonding pads were formed by UHV Ti-Au
metallization and pattern plating (Au). Patterned glass and silicon wafers were aligned and anodically
bonded; whereas, the metallic lines and the microaccelerometer anchors are eutectically bonded.
Finally, the suspended comb-type device structure consisting of two torsional beams of 5μm width and
interdigitated comb fingers of 10μm width is achieved by Dissolve Wafer Process (DWP). The paper
highlights the fabrication challenges faced during the realization of the comb-type structure.
Copyright © 2009 IFSA.

Keywords: Comb-type accelerometer, Capacitive sensing, Wet etching, Dissolve Wafer Process
(DWP)



1. Introduction
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DOCUMENT INFO
Description: The current paper presents fabrication of wet etching based comb-type microaccelerometer structure consisting of 47 interdigitated fingers attached to a large proof mass, which is suspended by two narrow torsional beams. Silicon (, p-type) was oxidized and the microaccelerometer structure was patterned by photolithography. Desired device thickness was achieved by combination of wet anisotropic etching of 15m depth and formation of 12m thick P^sup ++^ etch stop layer. Pits of 15m were formed in Pyrex glass and metallic lines with bonding pads were formed by UHV Ti-Au metallization and pattern plating (Au). Patterned glass and silicon wafers were aligned and anodically bonded; whereas, the metallic lines and the microaccelerometer anchors are eutectically bonded. Finally, the suspended comb-type device structure consisting of two torsional beams of 5m width and interdigitated comb fingers of 10m width is achieved by Dissolve Wafer Process (DWP). The paper highlights the fabrication challenges faced during the realization of the comb-type structure. [PUBLICATION ABSTRACT]
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