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Buried electrode electroacoustic technology for the fabrication of thin film based resonant components
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. (Fasta tillståndets elektronik)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. (Fasta tillståndets elektronik)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. (Fasta tillståndets elektronik)
2006 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 9, 1869-1874 p.Article in journal (Refereed) Published
Abstract [en]

A fabrication process for thin film electroacoustic devices utilizing buriedelectrodes is presented. A one-step lithography process has been developedto bury electrodes resulting in a planarized surface. The proposedtechnology is expected to bring about a number of benefits concerning theperformance of a variety of thin film electroacoustic devices. With respectto thin film plate acoustic resonators (FPAR), burying the reflectorelectrodes results in improved reflectivity and potentially lowersusceptibility to acousto-migration effects. It is also shown that employingthe proposed technology for the fabrication of both thin film bulk acousticresonators (FBAR) and thin film solidity mounted bulk acoustic resonators(SBAR) eliminates certain macro-structural defects in the piezoelectric filmwhich is a prerequisite for substantially improved device performance andhigher power handling capability. The buried electrode electroacoustic (EA)technology is demonstrated for a thin aluminium nitride (AlN) piezoelectricfilm with electrodes of both molybdenum (Mo) and tungsten (W). The latterhave been primarily chosen because of their high electroacoustic materialquality. Thin film resonant structures produced by this technology arecharacterized and their features are discussed.

Place, publisher, year, edition, pages
2006. Vol. 16, no 9, 1869-1874 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-88219DOI: 10.1088/0960-1317/16/9/016ISI: 000239774600035OAI: oai:DiVA.org:uu-88219DiVA: diva2:139719
Projects
SSF ICTEA
Available from: 2009-01-26 Created: 2009-01-26 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Electro-Acoustic and Electronic Applications Utilizing Thin Film Aluminium Nitride
Open this publication in new window or tab >>Electro-Acoustic and Electronic Applications Utilizing Thin Film Aluminium Nitride
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years there has been a huge increase in the growth of communication systems such as mobile phones, wireless local area networks (WLAN), satellite navigation and various other forms of wireless data communication that have made analogue frequency control a key issue. The increase in frequency spectrum crowding and the increase of frequency into microwave region, along with the need for minimisation and capacity improvement, has shown the need for the development of high performance, miniature, on-chip filters operating in the low to medium GHz frequency range. This has hastened the need for alternatives to ceramic resonators due to their limits in device size and performance, which in turn, has led to development of the thin film electro-acoustics industry with surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters now fabricated in their millions. Further, this new technology opens the way for integrating the traditionally incompatible integrated circuit (IC) and electro-acoustic (EA) technologies, bringing about substantial economic and performance benefits.

In this thesis the compatibility of aluminium nitride (AlN) to IC fabrication is explored as a means for furthering integration issues. Various issues have been explored where either tailoring thin film bulk acoustic resonator (FBAR) design, such as development of an improved solidly mounted resonator (SMR) technology, and use of IC technology, such as chemical mechanical polishing (CMP) or nickel silicide (NiSi), has made improvements beneficial for resonator fabrication or enabled IC integration. The former has resulted in major improvements to Quality factor, power handling and encapsulation respectively. The later has provided alternative methods to reduce electro- or acoustomigration, reduced device size, for plate waves, supplied novel low acoustic impedance material for high power applications and alternative electrodes for use in high temperature sensors.

Another method to enhance integration by using the piezoelectric material, AlN, in the IC side has also been explored. Here methods for analysing AlN film contamination and stoichiometry have been used for analysis of AlN as a high-k dielectric material. This has even brought benefits in knowledge of film composition for use as a passivation material with SiC substrates, investigated in high power high frequency applications. Lastly AlN has been used as a buried insulator material for new silicon-on-insulator substrates (SOI) for increased heat conduction. These new substrates have been analysed with further development for improved performance indicated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 643
Keyword
AlN, FBAR, FPAR, CMP, SOI, Nickel Silicide, Wafer Bonding
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:uu:diva-100957 (URN)978-91-554-7522-2 (ISBN)
Public defence
2009-05-22, Siegbahnsalen, The Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Projects
wisenet
Available from: 2009-04-29 Created: 2009-04-14 Last updated: 2011-01-17Bibliographically approved

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