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Electro-Acoustic and Electronic Applications Utilizing Thin Film Aluminium Nitride
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
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. , p. 77
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 643
Keywords [en]
AlN, FBAR, FPAR, CMP, SOI, Nickel Silicide, Wafer Bonding
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
URN: urn:nbn:se:uu:diva-100957ISBN: 978-91-554-7522-2 (print)OAI: oai:DiVA.org:uu-100957DiVA, id: diva2:211728
Public defence
2009-05-22, Siegbahnsalen, The Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Projects
wisenetAvailable from: 2009-04-29 Created: 2009-04-14 Last updated: 2011-01-17Bibliographically approved
List of papers
1. Buried electrode electroacoustic technology for the fabrication of thin film based resonant components
Open this publication in new window or tab >>Buried electrode electroacoustic technology for the fabrication of thin film based resonant components
2006 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 9, p. 1869-1874Article 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.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-88219 (URN)10.1088/0960-1317/16/9/016 (DOI)000239774600035 ()
Projects
SSF ICTEA
Available from: 2009-01-26 Created: 2009-01-26 Last updated: 2017-12-14Bibliographically approved
2. Solidly mounted thin film electro-acoustic resonator utilizing a conductive Bragg reflector
Open this publication in new window or tab >>Solidly mounted thin film electro-acoustic resonator utilizing a conductive Bragg reflector
2008 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 141, no 2, p. 598-602Article in journal (Refereed) Published
Abstract [en]

A new design of a solidly mounted resonator (SMR) that utilizes an all-metal Bragg reflector eliminating thus the need for a bottom electrode is proposed. In this configuration, the role of the bottom electrode is taken by the Bragg reflector rendering the resonator “combined electrode-Bragg reflector SMR”. The main advantages of the proposed design are the substantially reduced electrode resistance (and hence higher Q), the utilization of the full piezoelectric coupling at high frequencies as well as expected improvement in power handling capabilities due to lower dissipation and improved heat conductivity. Resonators with the classical and the new design have been fabricated and evaluated. The measurements indicate that indeed the resonators with the new design demonstrate improved performance.

Keywords
Micromachined acoustic resonator, AlN, Bragg reflector, Equivalent circuit
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-13019 (URN)10.1016/j.sna.2007.09.002 (DOI)000253734900048 ()
Projects
WISENETICTEA (SSF)
Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2017-12-11Bibliographically approved
3. Q-degradation and Crosstalk in BAW Sensor Arrays Operating in Conductive Liquid Media
Open this publication in new window or tab >>Q-degradation and Crosstalk in BAW Sensor Arrays Operating in Conductive Liquid Media
(English)In: IEEE Sensors Journal, ISSN 1530-437XArticle in journal (Refereed) Submitted
Keywords
Bulk acoustic wave devices, biomedical transducers, aluminumnitride, crosstalk
Identifiers
urn:nbn:se:uu:diva-100392 (URN)
Available from: 2009-03-31 Created: 2009-03-31 Last updated: 2009-04-03Bibliographically approved
4. Thick NiSi Electrodes for AlN Electroacoustic Applications
Open this publication in new window or tab >>Thick NiSi Electrodes for AlN Electroacoustic Applications
Show others...
2009 (English)In: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 12, no 5, p. H182-H184Article in journal (Refereed) Published
Abstract [en]

Theuse of thick NiSi electrodes in electroacoustic resonators allows front-endintegration with integrated circuit technology. Problems are identified in theformation of thick nickel silicide (NiSi) electrodes via a singledeposition of Ni onto blank Si wafers. An alternative fabricationprocess based on the deposition and silicidation of a multilayerfilm is presented. The films were found to have lowresistivity and smooth surfaces, with the layered structure preserved evenafter silicidation. Textured piezoelectric films of (002) wurtzite AlN demonstrateda diffraction-peak width that narrows to 3.5° when deposited ona thick 10 pair NiSi film.

Place, publisher, year, edition, pages
The Electrochemical Society, 2009
Keywords
acoustoelectric devices, aluminium compounds, electrodes, nickel alloys, piezoelectric thin films, resonators, silicon alloys, sputter deposition
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-99095 (URN)10.1149/1.3093099 (DOI)000264283100027 ()
Projects
SSF ICTEA
Available from: 2009-03-06 Created: 2009-03-06 Last updated: 2017-12-13
5. Thick silicides synthesised with smooth surface for integrated TFBAR applications
Open this publication in new window or tab >>Thick silicides synthesised with smooth surface for integrated TFBAR applications
Show others...
(English)Article in journal (Refereed) Submitted
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-100393 (URN)
Available from: 2009-03-31 Created: 2009-03-31 Last updated: 2013-11-21
6. Comparing XPS and ToF-ERDA measurement of high-k dielectric materials
Open this publication in new window or tab >>Comparing XPS and ToF-ERDA measurement of high-k dielectric materials
2007 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-12732 (URN)
Conference
17th International Vacuum Conference (IVC-17), 13th International Conference on Surface science (ICSS-13), International Conference on Nanoscience and Technology 2007 (ICN+T 2007) Stockholm, Sweden, July 2-6 (2007) publ in Journal of Physics: Conference Series
Available from: 2008-01-11 Created: 2008-01-11 Last updated: 2016-04-11Bibliographically approved
7. Improved Properties of AlON/4H-SiC Interface for Passivation Studies
Open this publication in new window or tab >>Improved Properties of AlON/4H-SiC Interface for Passivation Studies
Show others...
2009 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 600-603, p. 763-766Article in journal (Refereed) Published
Abstract [en]

Aluminium oxynitride (AlON) films of variable composition were grown by reactive sputter deposition in a N2/O2 ambient at room temperature and studied for device passivation. The films were deposited on Si and 4H-SiC substrates as well as on SiC PiN diodes. The AlON/SiO2/SiC stack provided superior interface properties compared to the AlON/SiC structure. Samples with 8% oxygen content, in the AlON film, and subjected to a UV exposure prior to deposition, exhibited the smallest net positive interface charge. A large net negative interface charge was observed for samples with 10% oxygen content and for the samples with 8% oxygen content and subjected to a RCA1 surface clean, prior to deposition. Diodes passivated with AlON films demonstrated reduced leakage current compared to as-processed diodes.

Place, publisher, year, edition, pages
Switzerland: Trans Tech Publications, 2009
Keywords
SiC, AlN, passivation, leakage currents
National Category
Engineering and Technology
Research subject
Electronics
Identifiers
urn:nbn:se:uu:diva-100955 (URN)10.4028/www.scientific.net/MSF.600-603.763 (DOI)
Projects
WISENET
Available from: 2009-04-14 Created: 2009-04-14 Last updated: 2017-12-13Bibliographically approved
8. Hydrophilic Wafer Bond Fabrication and Thermal Characterisation of new SOI Incorporating Buried Aluminium Nitride Insulator
Open this publication in new window or tab >>Hydrophilic Wafer Bond Fabrication and Thermal Characterisation of new SOI Incorporating Buried Aluminium Nitride Insulator
(English)Manuscript (Other (popular science, discussion, etc.))
Abstract [en]

Due to self heating effects of applications requiring high power dissipation in commercial SOI the need for alternative buried insulators such as aluminium nitride (AlN) is paramount. Here AlN films have been reactively sputtered with the smooth surfaces required for hydrophilic bonding. A bonding layer of amorphous silicon, -Si, has been sequentially sputtered with a surface roughness of 0.3 nm. A method of channelling the desorbed water and trapped gasses is presented with bond strength around 1.2 J/m2. Successful transfer of a silicon device layer is demonstrated onto a buried AlN insulator with a sheet resistance similar to original commercial specification. Electrical and thermal devices are fabricated in the device silicon using standard commercial MOS fabrication techniques. A thermal resistance of 47.5 K/W and 97 K/W is extracted for the new buried AlN insulator and commercial SOI, respectively. Thermal barriers hindering the full thermal properties of buried AlN are identified and solutions recommended

Keywords
SOI, AlN, Wafer bonding, self heating, hydrophilic
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:uu:diva-100956 (URN)
Available from: 2009-04-14 Created: 2009-04-14 Last updated: 2010-01-14

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