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Synthesis of Thin Piezoelectric AlN Films in View of Sensors and Telecom Applications
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. University of Campinas, Brazil (UNICAMP). (Thin Films)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The requirements of the consumer market on high frequency devices have been more and more demanding over the last decades. Thus, a continuing enhancement of the devices’ performance is required in order to meet these demands. In a macro view, changing the design of the device can result in an improvement of its performance. In a micro view, the physical properties of the device materials have a strong influence on its final performance. In the case of high frequency devices based on piezoelectric materials, a natural way to improve their performance is through the improvement of the properties of the piezoelectric layer. The piezoelectric material studied in this work is AlN, which is an outstanding material among other piezoelectric materials due to its unique combination of material properties.

This thesis presents results from experimental studies on the synthesis of AlN thin films in view of telecom, microelectronic and sensor applications. The main objective of the thesis is to custom design the functional properties of AlN to best suit these for the specific application in mind. This is achieved through careful control of the crystallographic structure and texture as well as film composition.

The piezoelectric properties of AlN films were enhanced by doping with Sc. Films with different Sc concentrations were fabricated and analyzed, and the coupling coefficient (kt2) was enhanced a factor of two by adding 15% of Sc to the AlN films. The enhancement of kt2 is of interest since it can contribute to a more relaxed design of high frequency devices. Further, in order to obtain better deposition control of c-axis tilted AlN films, a new experimental setup were proposed. When this novel setup was used, films with well-defined thicknesses and tilt uniformity were achieved. Films with such characteristics are very favorable to use in sensors based on electroacoustic devices operating in viscous media. Studies were also performed in order to obtain c-axis oriented AlN films deposited directly on Si substrates at reduced temperatures. The deposition technique used was HiPIMS, and the results indicated significant improvements in the film texture when comparing to the conventional Pulsed DC deposition process.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 83 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1160
Keyword [en]
Aluminum nitride, reactive sputtering, c-axis oriented films, tilted films, electroacoustic devices, piezoelectric materials, Aluminum Scandium Nitride, HiPIMS, high-k dielectric
National Category
Other Materials Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
URN: urn:nbn:se:uu:diva-229588ISBN: 978-91-554-8995-3 (print)OAI: oai:DiVA.org:uu-229588DiVA: diva2:737097
Public defence
2014-09-24, Conference Room, FEEC, UNICAMP, Av. Albert Einstein, 400 / Cidade Universitária Zeferino Vaz / Distrito Barão Geraldo, Campinas, Brazil, 14:30 (English)
Opponent
Supervisors
Available from: 2014-09-01 Created: 2014-08-11 Last updated: 2014-09-08
List of papers
1. Thin AlN films deposited by reactive HiPIMS and Pulsed DC sputtering: a comparative study
Open this publication in new window or tab >>Thin AlN films deposited by reactive HiPIMS and Pulsed DC sputtering: a comparative study
(English)Manuscript (preprint) (Other academic)
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-229587 (URN)
Available from: 2014-08-11 Created: 2014-08-11 Last updated: 2014-09-08
2. Efficient RF voltage transformer with bandpass filter characteristics
Open this publication in new window or tab >>Efficient RF voltage transformer with bandpass filter characteristics
2013 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 49, no 3, 198-199 p.Article in journal (Refereed) Published
Abstract [en]

A microwave bandpassfilter with a large ratio between the output andthe input impedance has been designed and fabricated. Consequently,it functions both as a voltage transformer and a bandpassfilter, or trans-filter for brevity. It represents a two-port micro-acoustic resonatoremploying Lamb waves in a thin piezoelectric AlNfilm grown ontoa Si carrier substrate with a centre frequency of around 887 MHz.The transfilter has a transformer ratio of 10 and a voltage efficiencyof over 80%. The component has a small size ( < 0.5 mm2) and isshown to sustain power levels of 250 mW. It can be used in avariety of cases where both voltage amplification and frequencyfilter-ing are required. Examples include: charge pumps in RFID tags,energy scavenging, remotely triggered switches, wake-up radios inwireless networks, stand-by units in home electronics etc.

Place, publisher, year, edition, pages
iet, 2013
Keyword
wireless, Lamb wave, trasnformer, RF
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-185262 (URN)10.1049/el.2012.3982 (DOI)000318542500023 ()
Projects
WiSENET and VR granted "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications "
Funder
VinnovaSwedish Research Council, 2009-5056
Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved
3. Preparation and characterization of high-k aluminium nitride (AlN) thin film for sensor and integrated circuits applications
Open this publication in new window or tab >>Preparation and characterization of high-k aluminium nitride (AlN) thin film for sensor and integrated circuits applications
Show others...
2012 (English)In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, no 6, 1454-1457 p.Article in journal (Refereed) Published
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:uu:diva-222608 (URN)10.1002/pssc.201100461 (DOI)
Note

Special Issue: 13th International Conference on the Formation of Semiconductor Interfaces (ICFSI-13)

Available from: 2014-04-11 Created: 2014-04-11 Last updated: 2017-12-05Bibliographically approved
4. Aluminum scandium nitride thin-film bulk acoustic resonators for wide band applications
Open this publication in new window or tab >>Aluminum scandium nitride thin-film bulk acoustic resonators for wide band applications
2011 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 1, 23-26 p.Article in journal (Refereed) Published
Abstract [en]

Piezoelectric c-textured Al(1-x)ScxN thin films, where the Sc relative concentration, x, varies in the range 0-0.15 have been studied in view of radio frequency (RF) electro-acoustic applications. Thin film bulk acoustic wave resonators (FBARs) employing these films were fabricated and characterized as a function of the Sc concentration for the first time. The measured electromechanical coupling is found to increase by as much as 100% in the above concentration range. The results from this work underline the potential of the c-textured Al(1-x)ScxN based FBARs for wide band RF applications.

Keyword
Thin film devices, Composite thin films, Acoustic microwave devices
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-156876 (URN)10.1016/j.vacuum.2011.03.026 (DOI)000295312300005 ()
Projects
WISENET
Funder
VINNOVA
Available from: 2011-08-10 Created: 2011-08-10 Last updated: 2017-12-08Bibliographically approved
5. Synthesis of c-tilted AlN films with a good tilt and thickness uniformity
Open this publication in new window or tab >>Synthesis of c-tilted AlN films with a good tilt and thickness uniformity
Show others...
2011 (English)In: Proceedings of IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM, New York, USA, 2011, 1238-1241 p.Conference paper, Published paper (Refereed)
Abstract [en]

This communication describes a method for the deposition of thin piezoelectric AlN films with an inclined c-axis relative to the surface normal. Further, the tilt over the wafer is sufficiently uniform and exhibits a planar symmetry as well as good thickness uniformity. Careful control of both the nucleation and growth stages is needed to obtain tilted films with excellent quality. Thus in the nucleation state, it is argued that two independent mechanisms, namely seed layer texture and/or surface roughness, are mainly responsible for the subsequent titled growth. To achieve the latter, however, a certain directionality of the deposition flux is also necessary. The directionality of the deposition flux is achieved through the use of an array of linear magnetrons tilted under a certain angle with respect to the substrate normal.

Place, publisher, year, edition, pages
New York, USA: , 2011
Keyword
AlN, c-axis tilt, piezoelectric, shear waves
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-189952 (URN)000309918400287 ()978-1-4577-1252-4 (ISBN)
Conference
IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), 18-21 October, 2011, Orlando, FL, USA
Projects
WISENET
Funder
Vinnova
Available from: 2013-01-05 Created: 2013-01-05 Last updated: 2015-01-07
6. Electrical characterization and morphological properties of AlN films prepared by dc reactive magnetron sputtering
Open this publication in new window or tab >>Electrical characterization and morphological properties of AlN films prepared by dc reactive magnetron sputtering
2011 (English)In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 88, no 5, 802-806 p.Article in journal, Meeting abstract (Refereed) Published
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:uu:diva-222603 (URN)10.1016/j.mee.2010.06.045 (DOI)
Conference
The 2010 International workshop on “Materials for Advanced Metallization” - MAM 2010
Available from: 2014-04-11 Created: 2014-04-11 Last updated: 2017-12-05Bibliographically approved

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