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Shear mode AlN thin film electro-acoustic resonant sensor operation in viscous media
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
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2007 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 123, no 1, 466-473 p.Article in journal (Refereed) Published
Abstract [en]

A shear mode thin film bulk acoustic resonator (FBAR) operating in liquid media together with a microfluidic transport system is presented. The resonator has been fabricated utilizing a recently developed reactive sputter-deposition process for AlN thin films with inclined c-axis relative to the surface normal with a mean tilt of around 30°. The resonator has a resonance frequency of around 1.2 GHz and a Q value in water of around 150. Sensor operation in water and glycerol solutions is characterized. Theoretical analysis of the sensor operation under viscous load as well as of the sensitivity and stability in general is presented. The theoretical predictions are compared with experimental measurements. The results demonstrate clearly the potential of FBAR biosensors for the fabrication of highly sensitive low cost biosensors, bioanalytical tools as well as for liquid sensing in general.

Place, publisher, year, edition, pages
2007. Vol. 123, no 1, 466-473 p.
Keyword [en]
AlN, Biosensor, FBAR, Quasi-shear polarized acoustic wave, Thickness mode resonator, Tilted films
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-10554DOI: 10.1016/j.snb.2006.09.028ISI: 000246171200068OAI: oai:DiVA.org:uu-10554DiVA: diva2:38322
Projects
WISENET
Available from: 2007-04-04 Created: 2007-04-04 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Thin Film Electroacoustic Devices for Biosensor Applications
Open this publication in new window or tab >>Thin Film Electroacoustic Devices for Biosensor Applications
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biosensors are today important devices within various application areas.

In this thesis a new type of label-free biosensor device is studied, which is fabricated using the same processes used for the fabrication of integrated circuits. This enables tighter integration and further sensors/biosensor miniaturization. The device is a so-called Thin Film Bulk Acoustic Resonator (FBAR). Within this thesis a low temperature reactive sputtering process for growing AlN thin films with a c-axis inclination of 20-30o has been developed. This enables shear mode FBAR fabrication suitable for in-liquid operation, essential for biosensor applications. Shear mode FBARs were fabricated operating at frequencies above 1GHz exhibiting Q values of 100-200 in water and electromechanical coupling factors kt2 of about 1.8%. This made it possible to move the thickness excited shear mode sensing of biological layers into a new sensing regime using substantially higher operation frequencies than the conventionally used quartz crystal microbalance (QCM) operating at 5-20MHz. Measured noise levels of shear mode FBARs in contact with water showed the resolution to be in the range 0.3ng/cm2 to 7.5ng/cm2. This demonstrated the FBAR resolution without any averaging or additional stabilization measures already to be in the same range as the conventional QCM (5ng/cm2), suggesting that FBARs may be a competitive and low cost alternative to QCM. The linear thickness limit for sensing of biomolecular layers was concluded to be larger than the thickness of the majority of the molecular systems envisaged for FBAR biosensor applications. A temperature compensated shear mode FBAR composite structure was demonstrated with retained coupling factor and Q-value by utilizing the second mode of operation. Understanding has been gained on the sensor operation as well as on how the design parameters influence its performance. Specifically, sensitivity amplification utilizing low acoustic impedance layers in the FBAR structure has been demonstrated and explained. Further, temperature compensated Lamb mode (FPAR) devices were also studied and demonstrated with optimized electromechanical couplings.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 96 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 609
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:uu:diva-89424 (URN)978-91-554-7432-4 (ISBN)
Public defence
2009-03-27, Å2005, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Projects
wisenet
Available from: 2009-03-06 Created: 2009-02-13 Last updated: 2011-01-17Bibliographically approved
2. Advanced Thin Film Electroacoustic Devices
Open this publication in new window or tab >>Advanced Thin Film Electroacoustic Devices
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Avancerade Elektroakustiska Tunnfilmskomponenter
Abstract [en]

The explosive development of the telecom industry and in particular wireless and mobile communications in recent years has lead to a rapid development of new component and fabrication technologies to continually satisfy the mutually exclusive requirements for better performance and miniaturization on the one hand and low cost on the other. A fundamental element in radio communications is time and frequency control, which in turn is achieved by high performance electro-acoustic components made on piezoelectric single crystalline substrates. The latter, however, reach their practical limits in terms of performance and cost as the frequency of operation reaches the microwave range. Thus, the thin film electro-acoustic technology, which uses thin piezoelectric films instead, has been recently developed to alleviate these deficiencies.

This thesis explores and addresses a number of issues related to thin film synthesis on the one hand as well as component design and fabrication on other. Specifically, the growth of highly c-axis textured AlN thin films has been studied and optimized for achieving high device performance. Perhaps, one of the biggest achievements of the work is the development of a unique process for the deposition of AlN films with a mean c-axis tilt, which is of vital importance for the fabrication of resonators operating in contact with liquids, i.e. biochemical sensors. This opens the way for the development of a whole range of sensors and bio-analytical tools. Further, high frequency Lamb wave resonators have been designed, fabricated and evaluated. Performance enhancement of FBAR devices is also addressed, e.g. spurious mode suppression, temperature compensation, etc. It has been demonstrated, that even without temperature compensation, shear mode resonators operating in a liquid still exhibit an excellent performance in terms of Q (200) and coupling (~1.8%) at 1.2 GHz, resulting in a mass resolution better than 2 ng cm-2 in water, which excels that of today’s quartz sensors.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 84 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 280
Keyword
Technology, aluminum nitride, FBAR, shear mode resonator, lamb wave devices, liquid sensor, biosensor, temperature compensation, reactive sputtering, TEKNIKVETENSKAP
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-7672 (URN)978-91-554-6819-4 (ISBN)
Public defence
2007-03-30, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2007-03-08 Created: 2007-03-08 Last updated: 2010-02-18Bibliographically approved
3. Reactive Sputter Deposition of Functional Thin Films
Open this publication in new window or tab >>Reactive Sputter Deposition of Functional Thin Films
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin film technology is of great significance for a variety of products, such as electronics, anti-reflective or hard coatings, sensors, solar cells, etc. This thesis concerns the synthesis of thin functional films, reactive magnetron sputter deposition process as such and the physical and functional characterization of the thin films synthesized. Characteristic for reactive sputtering processes is the hysteresis due to the target poisoning. One particular finding in this work is the elimination of the hysteresis by means of a mixed nitrogen/oxygen processing environment for dual sputtering of Alumina-Zirconia thin films. For a constant moderate flow of nitrogen, the hysteresis could be eliminated without significant incorporation of nitrogen in the films. It is concluded that optimum processing conditions for films of a desired composition can readily be estimated by modeling. The work on reactively sputtered SiO2–TiO2 thin films provides guidelines as to the choice of process parameters in view of the application in mind, by demonstrating that it is possible to tune the refractive index by using single composite Six/TiO2 targets with the right composition and operating in a suitable oxygen flow range. The influence of the target composition on the sputter yield is studied for reactively sputtered titanium oxide films. It is shown that by using sub-stoichiometric targets with the right composition and operating in the proper oxygen flow range, it is possible to increase the sputter rate and still obtain stoichiometric coatings. Wurtzite aluminum nitride (w-AlN) thin films are of great interest for electro-acoustic applications and their properties have in recent years been extensively studied. One way to tailor material properties is to vary the composition by adding other elements. Within this thesis (Al,B)N films of the wurtzite structure and a strong c-axis texture have been grown by reactive sputter deposition. Nanoindentation experiments show that the films have nanoindentation hardness in excess of 30 GPa, which is as hard as commercially available hard coatings such as TiN. Electrical properties of w-(Al,B)N thin films were investigated. W-(Al,B)N thin films are found to have a dielectric strength of ~3×106 V/cm, a relatively high k-value around 12 and conduction mechanisms similar to those of AlN. These results serve as basis for further research and applications of w-(Al,B)N thin films. An AlN thin film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR) together with a microfluidic transport system have been fabricated. The fabrication process is IC compatible and uses reactive sputtering to deposit piezoelectric AlN thin films with a non-zero mean inclination of the c-axis, which allows in-liquid operation through the excitation of the shear mode. The results on IC-compatibility, Q-values, operation frequency and resolution illustrate the potential of this technology for highly sensitive low-cost micro-biosensor systems for applications in, e.g. point-of-care testing.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 945
Keyword
thin film, reactive sputtering, coating, resonator, sensor, FBAR, SMR, aluminum nitride, (Al, B)N
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-175666 (URN)978-91-554-8403-3 (ISBN)
Public defence
2012-09-21, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2012-08-17 Created: 2012-06-11 Last updated: 2013-01-22

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Wingqvist, GunillaBjurström, JohanLiljeholm, LinaYantchev, VentsislavKatardjiev, Ilia

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