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Novel RF MEMS Devices Enabled by Three-Dimensional Micromachining
KTH, School of Electrical Engineering (EES), Micro and Nanosystems. (RF MEMS)ORCID iD: 0000-0002-8264-3231
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents novel radio frequency microelectromechanical (RF MEMS) circuits based on the three-dimensional (3-D) micromachined coplanar transmission lines whose geometry is re-configured by integrated microelectromechanical actuators. Two types of novel RF MEMS devices are proposed. The first is a concept of MEMS capacitors tuneable in multiple discrete and well-defined steps, implemented by in-plane moving of the ground side-walls of a 3-D micromachined coplanar waveguide transmission line. The MEMS actuators are completely embedded in the ground layer of the transmission line, and fabricated using a single-mask silicon-on-insulator (SOI) RF MEMS fabrication process. The resulting device achieves low insertion loss, a very high quality factor, high reliability, high linearity and high self actuation robustness. The second type introduces two novel concepts of area efficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. The coupling is achieved by tuning both the ground and the signal line coupling, obtaining a large tuneable coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity over a very large bandwidth. This thesis also presents for the first time on RF nonlinearity analysis of complex multi-device RF MEMS circuits. Closed-form analytical formulas for the IIP3 of MEMS multi-device circuit concepts are derived. A nonlinearity analysis, based on these formulas and on  measured device parameters, is performed for different circuit concepts and compared to the simulation results of multi-device  conlinear electromechanical circuit models. The degradation of the overall circuit nonlinearity with increasing number of device stages is investigated. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a highest overall IIP3 for the whole circuit.The thesis further investigates un-patterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip inductances. The approach used is to increase the thickness of the ferromagnetic material without increasing its conductivity, by using multilayer NiFe and AlN sandwich structure. This suppresses the induced currents very effectively and at the same time increases the ferromagnetic resonance, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. The so far highest permeability values above 1 GHz for on-chip integrated un-patterned NiFe layers were achieved.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , xiii, 79 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2014:014
Keyword [en]
Microelectromechanical systems, MEMS, Radio frequency microelectromechanical systems, RF MEMS, Micromachined transmission line, Micromachining, Tuneable capacitor, Switched capacitor, Coupled-line coupler, Tuneable directional coupler, Intermodulation distortion, MEMS varactor, Two-tone IIP3 measurement, Passive components and circuits, Reliability, Magnetic materials, NiFe multilayer composite, Permeability, Permittivity, Micromachined inductors
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-143757ISBN: 978-91-7595-075-4 (print)OAI: oai:DiVA.org:kth-143757DiVA: diva2:708366
Public defence
2014-04-24, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140328

Available from: 2014-03-28 Created: 2014-03-27 Last updated: 2016-08-11Bibliographically approved
List of papers
1. Multi-Position RF MEMS Tunable Capacitors Using Laterally Moving Sidewalls of 3-D Micromachined Transmission Lines
Open this publication in new window or tab >>Multi-Position RF MEMS Tunable Capacitors Using Laterally Moving Sidewalls of 3-D Micromachined Transmission Lines
2013 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 61, no 6, 2340-2352 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel concept of RF microelectromechanical systems (MEMS) tunable capacitors based on the lateral displacement of the sidewalls of a 3-D micromachined coplanar transmission line. The tuning of a single device is achieved in multiple discrete and well-defined tuning steps by integrated multi-stage MEMS electrostatic actuators that are embedded inside the ground layer of the transmission line. Three different design concepts, including devices with up to seven discrete tuning steps up to a tuning range of 58.6 to 144.5 fF, (C-max/C-min = 2.46) have been fabricated and characterized. The highest Q factor, measured by a weakly coupled transmission-line resonator, was determined as 88 at 40 GHz and was achieved for a device concept where the mechanical suspension elements were completely de-coupled from the RF signal path. These devices have demonstrated high self-actuation robustness with self-actuation pull-in occurring at 41.5 and 47.8 dBm for mechanical spring constants of 5.8 and 27.7 N/m, respectively. Nonlinearity measurements revealed that the third-order intermodulation intercept point (IIP3) for all discrete device states is above the measurement-setup limit of 68.5 dBm for our 2.5-GHz IIP3 setup, with a dual-tone separation of 12 MHz. Based on capacitance/gap/spring measurements, the IIP3 was calculated for all states to be between 71-91 dBm. For a mechanical spring design of 5.8 N/m, the actuation and release voltages were characterized as 30.7 and 21.15 V, respectively, and the pull-in time for the actuator bouncing to drop below 8% of the gap was measured to be 140 mu s. The mechanical resonance frequencies were measured to be 5.3 and 17.2 kHz for spring constant designs of 5.8 and 27.7 N/m, respectively. Reliability characterization exceeded 1 billion cycles, even in an uncontrolled atmospheric environment, with no degradation in the pull-in/pull-out hysteresis behavior being observed over these cycling tests.

Place, publisher, year, edition, pages
IEEE Press, 2013
Keyword
RF MEMS, switched capacitor, tunable capacitor, micromachined transmission line, micromachining
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-104307 (URN)10.1109/TMTT.2013.2259499 (DOI)000319979300009 ()2-s2.0-84878800249 (Scopus ID)
Note

QC 20130710

Available from: 2012-10-31 Created: 2012-10-31 Last updated: 2017-12-07Bibliographically approved
2. High-Directivity MEMS-Tunable Directional Couplers for 10–18-GHz Broadband Applications
Open this publication in new window or tab >>High-Directivity MEMS-Tunable Directional Couplers for 10–18-GHz Broadband Applications
2013 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 61, no 9, 3236-3246 p.Article in journal (Refereed) Published
Abstract [en]

This paper reports on two novel concepts of areaefficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. Concept 1 is based on symmetrically changing the geometry of the ground coupling of each signal line, while Concept 2 is simultaneously varying both the ground coupling and the coupling between the two signal lines. This enables uniform and well predictable performance over a very large frequency range, in particular a constant coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity. For an implemented micromachined prototype 3-to-6 dB coupler based on Concept 1, the measured isolation is better than 16 dB, and the return loss and directivity are better than 10 dB over the entire bandwidth from 10 to 18 GHz. Concept 2 presents an even more significant improvement. For an implemented 10-to-20 dB prototype based on Concept 2, the measured isolation is better than 40 dB and the return loss is better than 15 dB over the entire bandwidth from 10 to 18 GHz for both states. The directivities for both states are better than 22 dB and 40 dB, respectively, over the whole frequency range. The measured data fits the simulation very well, except for higher through-port losses of the prototype devices. All devices have been implemented in an SOI RF MEMS fabrication process. Measured actuation voltages of the different actuators are lower than 35 V. Reliability tests were conducted up to 500 million cycles without device degradation.

Place, publisher, year, edition, pages
IEEE Press, 2013
Keyword
Coupled-line coupler, RF microelectromechanical systems (MEMS), micromachined transmission line, micromachining, tunable directional coupler
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-129308 (URN)10.1109/TMTT.2013.2273763 (DOI)000325655900009 ()2-s2.0-84883741451 (Scopus ID)
Note

QC 20131022

Available from: 2013-09-25 Created: 2013-09-25 Last updated: 2017-12-06Bibliographically approved
3. Analysis of Linearity Deterioration in Multidevice RF MEMS Circuits
Open this publication in new window or tab >>Analysis of Linearity Deterioration in Multidevice RF MEMS Circuits
2014 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 61, no 5, 1529-1535 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents for the first time an RF nonlinearity analysis of complex multidevice radio frequency microelectromechanical system (RF MEMS) circuits. The IIP3 of different RF MEMS multidevice tunable-circuit concepts including digital MEMS varactor banks, MEMS switched capacitor banks, distributed MEMS phase shifters, and MEMS tunable filters, is investigated. Closed-form analytical formulas for the IIP3 of MEMS multidevice circuit concepts are derived. A nonlinearity analysis, based on measured device parameters, is presented for exemplary circuits of the different concepts using a multidevice nonlinear electromechanical circuit model implemented in Agilent Advanced Design System. The results of the nonlinear electromechanical model are also compared with the calculated IIP3 using derived equations for the digital MEMS varactor bank and MEMS switched capacitor bank. The degradation of the overall circuit linearity with increasing number of device stages is also investigated, with the conclusion that the overall circuit IIP3 is reduced by half when doubling the number of stages, if proper design precautions are not taken. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a higher overall IIP3 for the whole circuit. In addition, the nonlinearity of a novel MEMS tunable capacitor concept introduced by the authors, based on an MEMS actuator with discrete tuning steps, is discussed and the IIP3 is calculated using derived analytical formulas.

Keyword
Intermodulation distortion (IMD), RF MEMS, tunable capacitor, two-tone IIP3 measurement, MEMS varactor
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-143621 (URN)10.1109/TED.2014.2312215 (DOI)000337753300046 ()2-s2.0-84899994242 (Scopus ID)
Note

QC 20140813

Available from: 2014-03-25 Created: 2014-03-25 Last updated: 2017-12-05Bibliographically approved
4. MEMS reconfigurable millimeter-wave surface for V-band rectangular-waveguide switch
Open this publication in new window or tab >>MEMS reconfigurable millimeter-wave surface for V-band rectangular-waveguide switch
Show others...
2013 (English)In: International Journal of Microwave and Wireless Technologies, ISSN 1759-0787, Vol. 5, no 3, 341-349 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents for the first time a novel concept of a microelectromechanical systems (MEMS) waveguide switch based on a reconfigurable surface, whose working principle is to block the wave propagation by short-circuiting the electrical field lines of the TE10 mode of a WR-12 rectangular waveguide. The reconfigurable surface is only 30 mu m thick and consists of up to 1260 micro-machined cantilevers and 660 contact points in the waveguide cross-section, which are moved simultaneously by integrated MEMS comb-drive actuators. Measurements of fabricated prototypes show that the devices are blocking wave propagation in the OFF-state with over 30 dB isolation for all designs, and allow for transmission of less than 0.65 dB insertion loss for the best design in the ON-state for 60-70 GHz. Furthermore, the paper investigates the integration of such microchips into WR-12 waveguides, which is facilitated by tailor-made waveguide flanges and compliant, conductive-polymer interposer sheets. It is demonstrated by reference measurements where the measured insertion loss of the switches is mainly attributed to the chip-to-waveguide assembly. For the first prototypes of this novel MEMS microwave device concept, the comb-drive actuators did not function properly due to poor fabrication yield. Therefore, for measuring the OFF-state, the devices were fixated mechanically.

Keyword
RF-MEMS and MOEMS, Passive components and circuits
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-117932 (URN)10.1017/S1759078713000378 (DOI)000321588500018 ()2-s2.0-84880249868 (Scopus ID)
Funder
EU, European Research Council, 267528
Note

QC 20130814

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2014-03-28Bibliographically approved
5. Microwave MEMS Devices Designed for Process Robustness and Operational Reliability
Open this publication in new window or tab >>Microwave MEMS Devices Designed for Process Robustness and Operational Reliability
Show others...
2011 (English)In: International Journal of Microwave and Wireless Technology, ISSN 1759-0787, Vol. 3, no 5, 547-563 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents an overview on novel microwave micro-electromechanical systems (MEMS) device concepts developed in our research group during the last 5 years, which are specifically designed for addressing some fundamental problems for reliable device operation and robustness to process parameter variation. In contrast to conventional solutions, the presented device concepts are targeted at eliminating their respective failure modes rather than reducing or controlling them. Novel concepts of MEMS phase shifters, tunable microwave surfaces, reconfigurable leaky-wave antennas, multi-stable switches, and tunable capacitors are presented, featuring the following innovative design elements: dielectric-less actuators to overcome dielectric charging; reversing active/passive functions in MEMS switch actuators to improve recovery from contact stiction; symmetrical anti-parallel metallization for full stress-control and temperature compensation of composite dielectric/metal layers for free-standing structures; monocrystalline silicon as structural material for superior mechanical performance; and eliminating thin metallic bridges for high–power handling. This paper summarizes the design, fabrication, and measurement of devices featuring these concepts, enhanced by new characterization data, and discusses them in the context of the conventional MEMS device design.

Place, publisher, year, edition, pages
Cambridge University Press and the European Microwave Association, 2011
Keyword
RF MEMS, Reliability, MEMS design, Phase shifter, Tuneable capacitor, MEMS switch
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-48388 (URN)10.1017/S1759078711000845 (DOI)000208613500007 ()2-s2.0-80455144997 (Scopus ID)
Note

Invited.

QC 20111124

Available from: 2011-11-24 Created: 2011-11-17 Last updated: 2014-03-28Bibliographically approved
6. High-Aspect-Ratio Through Silicon Vias for High-Frequency Application Fabricated by Magnetic Assembly of Gold-Coated Nickel Wires
Open this publication in new window or tab >>High-Aspect-Ratio Through Silicon Vias for High-Frequency Application Fabricated by Magnetic Assembly of Gold-Coated Nickel Wires
Show others...
2015 (English)In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 5, no 1, 21-27 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we demonstrate a novel manufacturing technology for high-aspect-ratio vertical interconnects for high-frequency applications. This novel approach is based on magnetic self-assembly of prefabricated nickel wires that are subsequently insulated with a thermosetting polymer. The high-frequency performance of the through silicon vias (TSVs) is enhanced by depositing a gold layer on the outer surface of the nickel wires and by reducing capacitive parasitics through a low-k polymer liner. As compared with conventional TSV designs, this novel concept offers a more compact design and a simpler, potentially more cost-effective manufacturing process. Moreover, this fabrication concept is very versatile and adaptable to many different applications, such as interposer, micro electromechanical systems, or millimeter wave applications. For evaluation purposes, coplanar waveguides with incorporated TSV interconnections were fabricated and characterized. The experimental results reveal a high bandwidth from dc to 86 GHz and an insertion loss of <0.53 dB per single TSV interconnection for frequencies up to 75 GHz.

Place, publisher, year, edition, pages
IEEE Press, 2015
Keyword
RF signal transmission, skin effect, through silicon via (TSV), vertical interconnection, wafer scale integration
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-160401 (URN)10.1109/TCPMT.2014.2369236 (DOI)000348123200004 ()2-s2.0-84921411485 (Scopus ID)
Funder
Swedish Research Council, 277879
Note

QC 20150224

Available from: 2015-02-24 Created: 2015-02-19 Last updated: 2017-12-04Bibliographically approved
7. Permeability Enhancement by Multilayer Ferromagnetic Composites for Magnetic-Core On-Chip Inductors
Open this publication in new window or tab >>Permeability Enhancement by Multilayer Ferromagnetic Composites for Magnetic-Core On-Chip Inductors
2014 (English)In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 24, no 10, 677-679 p.Article in journal (Refereed) Published
Abstract [en]

This letter reports about unpatterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip and interposer integrated inductances. The proposed composite structure reduces RF induced currents and thus pushes the permeability cutoff to beyond 3.7 GHz, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. To the best knowledge of the authors, we achieve the highest effective relative permeability of 28 at 1 GHz, highest ferromagnetic resonance frequency and highest inductance enhancement factor above 1 GHz ever reported for devices based on on-chip unpatterned NiFe magnetic cores. A single loop inductor is also implemented as a technology demonstrator, achieving an inductance enhancement of 4.8 and a quality factor enhancement of 4.5 at 400 MHz.

Place, publisher, year, edition, pages
IEEE Press, 2014
Keyword
Magnetic materials, microstrip, NiFe multilayer composite, permeability, permittivity, micromachined inductors
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-143665 (URN)10.1109/LMWC.2014.2341037 (DOI)000343611100009 ()2-s2.0-84907939162 (Scopus ID)
Note

QC 20141114

Available from: 2014-03-26 Created: 2014-03-26 Last updated: 2017-12-05Bibliographically approved

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