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Processing and On-Wafer Test of Ferroelectric Film Microwave Varactors
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies. Ferroelectric materials usually have high dielectric constant, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used to fabricate capacitors for electronic industry because of their high dielectric constant, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure and used for electrically tunable microwave integrated circuits. It is an important task to sinter highly tunable and low loss ferroelectrics, fabricate and test the properties of microwave ferroelectric components.

This thesis shows experimental results on growth, crystalline and microwave properties of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), and AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering techniques from stoichiometric high density ceramic NKN, ATN, ATO, ANO and BST targets onto LaAlO3 (LAO), Al2O3 (r-cut sapphire), Nd:YAlO3 single crystals and amorphous glass substrates. Advanced X-ray diffraction examinations showed NKN, ATN, BST films on LAO substrates grow epitaxially, whereas films on r-cut sapphire were found to be preferentially (00l) oriented.

Coplanar waveguide 2 µm finger gap interdigital capacitor (CPWIDC) structures were fabricated by photolithography process and metal lift-off technique. On-wafer tests up to 40 GHz were performed to characterize microwave properties of the ferromagnetic film CPWIDC devices. The measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field was applied to planar capacitors to measure tunability. Original de-embedding technique has been developed to calculate capacitance, loss tan δ, and tunability of varactors from the measured S-parameters.

NKN film interdigital capacitors on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ~ 0.13, K-factor = tunability/tan δ from 152% @ 10GHz to 46% @ 40GHz. The ATN/sapphire CPWIDCs showed the lowest dispersion ~ 4.3% in whole frequency range from 1 to 40 GHz, voltage tunability 4.7% @ 20GHz and 200 kV/cm, lowest loss tangent ~ 0.068 @ 20GHz, K-factor = tunability/tan δ ranged from 124% @ 10GHz to 35% @ 40GHz.

BST film CPWIDCs on sapphire showed frequency about 17%, the highest voltage tunability ~ 22.2%, loss tangent ~ 0.137 @ 20GHz, and K-factor = 281% @ 10GHz to 95% @ 40GHz.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , x, 74 p.
Series
Trita-ICT/MAP, 2006:3
Keyword [en]
: ferroelectrics, sodium potassium niobates, silver tantalite niobate, barium strontium titanate, thin films, pulsed laser deposition, rf magnetron sputtering, coplanar waveguide, photolithography
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4226OAI: oai:DiVA.org:kth-4226DiVA: diva2:11335
Public defence
2006-12-15, Sal D, KTH-Forum, Isafjordsg. 39, Kista, 10:00 (English)
Opponent
Supervisors
Note
QC 20100906Available from: 2008-12-23 Created: 2008-12-23 Last updated: 2010-09-06Bibliographically approved
List of papers
1. Processing and on-wafer test of ferroelectric film microwave varactors
Open this publication in new window or tab >>Processing and on-wafer test of ferroelectric film microwave varactors
2006 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Applied physics letters, Vol. 88, no 19, 192905- p.Article in journal (Refereed) Published
Abstract [en]

We present comparative characteristics of microwave variable capacitors (varactors) fabricated on Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), and Ba0.5Sr0.5TiO3 (BST) ferroelectric films grown by rf-magnetron sputtering (NKN) and pulsed laser deposition (ATN and BST) techniques on the sapphire. Two port 2 mu m finger gap coplanar waveguide interdigital capacitors (CPWIDCs) were defined on ferroelectric films surface by photolithographic lift-off technique. Deembedding method was employed to extract properties of CPWIDC from the S parameters measured in microwave range up to 40 GHz. BST films on sapphire substrates show superior tunability of 26% (20 GHz, 200 kV/cm), whereas ATN films possess the lowest tan delta=0.06 at 20 GHz and extremely low dispersion of 4.3% in a whole frequency range of 45 MHz-40 GHz.

Keyword
Capacitors, spectra
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6578 (URN)10.1063/1.2202748 (DOI)000237477400070 ()2-s2.0-33646710366 (Scopus ID)
Note
QC 20100906Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2011-11-08Bibliographically approved
2. Microwave properties of AgTa0.5Nb0.5O3 thin film varactors on various substrates
Open this publication in new window or tab >>Microwave properties of AgTa0.5Nb0.5O3 thin film varactors on various substrates
2007 (English)In: 2006 15TH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS, New York: IEEE , 2007, 363-366 p.Conference paper, Published paper (Refereed)
Abstract [en]

400nm thick AgTa0.5Nb0.5O3 (ATN) films have been sintered by pulsed laser deposition technique on LaAlO3 (001), sapphire (Al2O3-01 (1) under bar2, r-cut) single crystal substrates and Coming 7059 Glass. Photolithography and metal lift-off technique were used to fabricate tunable Coplanar Waveguide Interdigital Capacitors (CPWIDCs). On-wafer test of varactors was performed with microwave network analyzer and G-S-G microwave probe. ATN/LaAlO3 capacitors demonstrated the highest tunability (similar to 5.8%@20GHz), ATN/Glass showed the best flat dispersion (similar to 3.9%) and ATN/ Al2O3 showed the lowest loss tangent (similar to 0.06@20GHz) in the microwave range from 1 to 40 GHz.

Place, publisher, year, edition, pages
New York: IEEE, 2007
Series
IEEE International Symposium on Applications of Ferroelectrics, ISSN 1099-4734
Keyword
Ceramic thin film, Coplanar waveguides, Scattering parameters, Voltage tunable devices
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6579 (URN)000262360900088 ()978-1-4244-1331-7 (ISBN)
Conference
15th IEEE International Symposium on Applications of Ferroelectrics Sunset Beach, NC, JUL 30-AUG 03, 2006 IEEE
Note
QC 20100906Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2011-04-04Bibliographically approved
3. Buried tantalate-niobate microwave varactors
Open this publication in new window or tab >>Buried tantalate-niobate microwave varactors
2007 (English)In: 2006 15TH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS, 2007, 347-350 p.Conference paper, Published paper (Refereed)
Abstract [en]

We present characteristics of microwave variable capacitors (varactors) buried in 2.5 mu m thick AgTa0.5Nb0.5O3 (ATN) film pulsed laser deposited on sapphire single crystal. 2 gm gap interdigital capacitors (IDC) were fabricated by photolithographic, dry etching and lift-off processes. For comparison, similar IDCs were also defined on top of ATN film. Capacitance and loss tangent have been determined using a modified de-embedding technique in the microwave range 25 MHz - 40 GHz. Buried structures show higher values of capacitance and tunability, keeping the same level of losses compared to standard topped devices and resulting in an increased K-factor = tunability/tan delta. Experimental results are explained within equivalent circuit model. Besides the increased performance, the new design avoids the need of a successive planarization step, which could be required in an integration process.

Series
IEEE International Symposium on Applications of Ferroelectrics, ISSN 1099-4734
Keyword
Silver-tantalate-niobate, voltage tunability, buried interdigital capacitors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6580 (URN)10.1109/ISAF.2006.4387902 (DOI)000262360900084 ()978-1-4244-1331-7 (ISBN)
Conference
15th IEEE International Symposium on Applications of Ferroelectrics Sunset Beach, NC, JUL 30-AUG 03, 2006
Note
QC 20100906Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2011-04-04Bibliographically approved
4. AgTaO3 and AgNbO3 thin films by pulsed laser deposition
Open this publication in new window or tab >>AgTaO3 and AgNbO3 thin films by pulsed laser deposition
2006 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, 615-618 p.Article in journal (Refereed) Published
Abstract [en]

Silver tantalate AgTaO3 (ATO) and silver niobate AgNbO3 (ANO) films have been grown on to the LaAlO3 (001) and sapphire Al2O3 (0112, r-cut) single crystals by pulsed laser deposition technique from stoichiometric ATO and ANO targets. X-ray diffraction study revealed epitaxial quality of ATO and ANO films on the LaAlO3 (00 1) Whereas on the sapphire r-cut substrate they are preferential (I 10) and (00 1) oriented. To characterize microwave films properties in the range from I to 40 GHz, coplanar line interdigital capacitors were fabricated by photolithography and lift-off technique. ANO film capacitors show superior properties: frequency dispersion was as low as 13%, voltage tunability (40 V, 200 kV/ cm) was about 4.6% at 20 GHz, loss tangent similar to 0.106 at 20 GHz, K-factor-tunability/tan delta from 49% @ 10 GHz to 33% at 40 GHz.

Keyword
ferroelectric ceramics, pulsed laser deposition, epitaxial silver tantalate niobate films, coplanar waveguides, voltage tunable microwave devices, scattering parameters measuremen
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6581 (URN)10.1016/j.tsf.2005.12.213 (DOI)000241220600056 ()2-s2.0-33748754029 (Scopus ID)
Note
QC 20100827Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2011-09-28Bibliographically approved
5. Niobate-tantalate thin films microwave varactors
Open this publication in new window or tab >>Niobate-tantalate thin films microwave varactors
2006 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Thin solid films, Vol. 515, no 2, 619-622 p.Article in journal (Refereed) Published
Abstract [en]

We present comparative characteristics of microwave variable capacitors (varactors) fabricated on Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN) and Ba0.5Sr0.5TiO3 (BST) ferroclectric films sintered by pulsed laser deposition technique. Two port 2 mu m finger gap coplanar waveguide interdigital capacitive (CPWIDC) structures were defined on ferroelectric films surface by a standard lift off technique. Results of the microwave on-wafer tests performed in frequency range 1 to 40 GHz have been examined with a de-embedding technique to extract device characteristics from the measured S-parameters. The frequency dispersion of capacitance was 37%, 4.3%, and 17%; the voltage tunability (200 kV/cm) 22%, 4.7%, and 22% at 20 GHz; loss tangent similar to 0.23, 0.068, and 0.137 at 20 GHz for NKN/Nd:YAlO3, ATN/Al2O3, and BST/Al2O3 films capacitors.

Keyword
ferroelectric ceramics, pulsed laser deposition, epitaxial films, pottasium sodium niobate, silver tantalate niobate, barium strontium titanate, coplanar waveguides, voltage tunable microwave devices, scattering parameters measurement
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6582 (URN)10.1016/j.tsf.2005.12.212 (DOI)000241220600057 ()2-s2.0-33748755445 (Scopus ID)
Note
QC 20100906Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2011-09-28Bibliographically approved
6. AgTa0.5Nb0.5O3 thin film coplanar waveguide microwave capacitors
Open this publication in new window or tab >>AgTa0.5Nb0.5O3 thin film coplanar waveguide microwave capacitors
2005 (English)In: Integrated Ferroelectrics, ISSN 1058-4587, Vol. 77, 13-20 p.Article in journal (Refereed) Published
Abstract [en]

400 nm thick AgTa0.5Nb0.5O3 (ATN) films have been prepared by pulsed laser depositiontechnique on LaAlO3 (001) and sapphire (Al2O3-0112, r -cut) single crystal substrates.Comprehensive X-ray diffraction analysis showed epitaxial quality of ATN/LaAlO3films and preferentially (001) orientation of ATN/Al2O3 films. Voltage tunable microwavecapacitors were fabricated by lift-off technique on the surface of ferroelectricfilms. Microwave on-wafer tests were performed in the range from 1 to 40 GHz. Frequencydispersion is about 4.3%, voltage tunability is 4.7% @ 20 GHz and 200 kV/cm,loss tangent ∼0.068 @ 20 GHz, K-factor=tunability/tanδ is ranged from 124% @10 GHz to 35% @ 40 GHz.

Keyword
Coplanar waveguide, microwave on-wafer test, photolithography, pulsed laser deposition, scatering parameter measurements, ferroelectric thin films, silver tantalate niobates, voltage tunable device
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6583 (URN)10.1080/10584580500413624 (DOI)000234386100003 ()2-s2.0-33645505627 (Scopus ID)
Note
QC 20100906Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-12-07Bibliographically approved
7. Na0.5K0.5NbO3 film microwave varactors
Open this publication in new window or tab >>Na0.5K0.5NbO3 film microwave varactors
2004 (English)In: Integrated Ferroelectrics, ISSN 1058-4587, Vol. 66, 291-300 p.Article in journal (Refereed) Published
Abstract [en]

Na0.5K0.5NbO3 (NKN) and Pb(Zr 0.53Ti0.47)O3 (PZT) films have been grown by rf-magnetron sputtering and pulsed laser deposition techniques, correspondingly, on sapphire (Al2O3-0112, r-cut), quartz (Y + 36°-cut) and YAlO3 + 1%Nd(Nd:YAlO3-001) single crystal substrates with Interdigital Capacitor (IDC) of Coplanar Waveguide (CPW) structure. Photolithography and metal lift-off technique was used for processing of the tunable microwave capacitor. Microwave network analyzer with G-S-G Picoprobe and probe station performed microsvave measurement with external DC bias. NKN film interdigital capacitors on Nd:YAlO3 show superior performance in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40 V, 200 kV/cm) was about 29%, loss tangent ∼0.13, K-factor from 152% @10 GHz to 46% @40 GHz, voltage independent Cp was about 230 fF, tan δp changes from 0.14 @ 10 GHz to 0.36 @40 GHz, real and imaginary part of interconnect impedance increases with frequency from 0.13 Ω@ 10 GHz to 0.50 Ω @40 GHz and from 1.9 Ω@10 GHz to 5.9 Ω @40 GHz respectively.

Keyword
Coplanar waveguide, Interdigital capacitor, Network analysis, Pulsed laser deposition, rf-magnetron sputtering, Thin ferroelectric NKN films
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6584 (URN)10.1080/10584580490895752 (DOI)000226089700031 ()2-s2.0-33646699867 (Scopus ID)
Note
QC 20100906Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-12-07Bibliographically approved

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