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AlN Thin Film Electroacoustic Devices
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Electronics.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recently, the enormous growth in personal communications systems (PCS), satellite communication and various other forms of wireless data communication has made analogue frequency control a key issue as the operation frequency increases to the low/medium GHz range. Surface acoustic wave (SAW) and bulk acoustic wave (BAW) electroacoustic devices are widely used today in a variety of applications both in consumer electronics as well as in specialized scientific and military equipment where frequency control is required. Conventional piezoelectric materials such as quartz, LiNbO3 and LiTaO3 suffer from a variety of limitations and in particular medium to low SAW/BAW velocity as well as being incompatible with the IC technology. Thin piezoelectric films offer the great flexibility of choosing at will the substrate/film combination, thus making use of the electroacoustic properties of non-piezoelectric substrates, which widens greatly the choice of fabrication materials and opens the way for integration of the traditionally incompatible electroacoustic and IC technologies.

This thesis focuses on the synthesis and characterization of novel thin film materials for electroacoustic applications. A prime choice of material is thin piezoelectric AlN films which have been grown using both RF and pulsed-DC reactive sputter deposition on a variety of substrate materials. A unique synthesis process has been developed allowing the deposition of high quality AlN films at room temperature, which increases greatly the process versatility. The films are fully c-axis oriented with a 1.6° FWHM value of the rocking curve of the AlN-(002) peak. Complete process flows for the fabrication of both SAW and BAW devices have been developed. Electroacoustic characterization of 2 GHz BAW resonators yielded an electromechanical coupling coefficient (kt²) of 6.5%, Q-value of 600 and a longitudinal velocity of 11350 m/s. AlN thin films based SAW resonators on SiO2/Si yielded a SAW velocity of around 5000 m/s and a piezoelectric coupling coefficient (K²) of around 0.3%. Finally, AlN on polycrystalline diamond 1 GHz SAW resonators exhibited an extremely high SAW velocity of 11800 m/s, a piezoelectric coupling coefficient (K²) of 1% and a Q-value of 500.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2003. , p. 67
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 817
Keywords [en]
Electrical engineering
Keywords [sv]
Elektroteknik, elektronik och fotonik
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
URN: urn:nbn:se:uu:diva-3359ISBN: 91-554-5557-3 (print)OAI: oai:DiVA.org:uu-3359DiVA, id: diva2:162491
Public defence
2003-04-16, Häggsalen, Ångströmlaboratoriet, Uppsala, 09:30
Opponent
Supervisors
Available from: 2003-03-25 Created: 2003-03-25Bibliographically approved

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