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Localized removal of the Au-Si eutectic bonding layer for the selective release of microstructures
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).ORCID iD: 0000-0001-9552-4234
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).ORCID iD: 0000-0001-8248-6670
2009 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 10, 105014-105023 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents and investigates a novel technique for the footprint and thickness-independent selective release of Au–Si eutectically bonded microstructures through the localized removal of their eutectic bond interface. The technique is based on the electrochemical removal of the gold in the eutectic layer and the selectivity is provided by patterning the eutectic layer and by proper electrical connection or isolation of the areas to be etched or removed, respectively. The gold removal results in a porous silicon layer, acting similar to standard etch holes in a subsequent sacrificial release etching. The paper presents the principle and the design requirements of the technique. First test devices were fabricated and the method successfully demonstrated. Furthermore, the paper investigates the release mechanism and the effects of different gold layouts on both the eutectic bonding and the release procedure.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2009. Vol. 19, no 10, 105014-105023 p.
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11830DOI: 10.1088/0960-1317/19/10/105014ISI: 000270133900014Scopus ID: 2-s2.0-70350630503OAI: oai:DiVA.org:kth-11830DiVA: diva2:284100
Note

QC20100729

Available from: 2010-01-04 Created: 2010-01-04 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Wafer-level heterogeneous integration of MEMS actuators
Open this publication in new window or tab >>Wafer-level heterogeneous integration of MEMS actuators
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents methods for the wafer-level integration of shape memory alloy (SMA) and electrostatic actuators to functionalize MEMS devices. The integration methods are based on heterogeneous integration, which is the integration of different materials and technologies. Background information about the actuators and the integration method is provided.

SMA microactuators offer the highest work density of all MEMS actuators, however, they are not yet a standard MEMS material, partially due to the lack of proper wafer-level integration methods. This thesis presents methods for the wafer-level heterogeneous integration of bulk SMA sheets and wires with silicon microstructures. First concepts and experiments are presented for integrating SMA actuators with knife gate microvalves, which are introduced in this thesis. These microvalves feature a gate moving out-of-plane to regulate a gas flow and first measurements indicate outstanding pneumatic performance in relation to the consumed silicon footprint area. This part of the work also includes a novel technique for the footprint and thickness independent selective release of Au-Si eutectically bonded microstructures based on localized electrochemical etching.

Electrostatic actuators are presented to functionalize MEMS crossbar switches, which are intended for the automated reconfiguration of copper-wire telecommunication networks and must allow to interconnect a number of input lines to a number of output lines in any combination desired. Following the concepts of heterogeneous integration, the device is divided into two parts which are fabricated separately and then assembled. One part contains an array of double-pole single-throw S-shaped actuator MEMS switches. The other part contains a signal line routing network which is interconnected by the switches after assembly of the two parts. The assembly is based on patterned adhesive wafer bonding and results in wafer-level encapsulation of the switch array. During operation, the switches in these arrays must be individually addressable. Instead of controlling each element with individual control lines, this thesis investigates a row/column addressing scheme to individually pull in or pull out single electrostatic actuators in the array with maximum operational reliability, determined by the statistical parameters of the pull-in and pull-out characteristics of the actuators.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xii, 78 p.
Series
Trita-EE, ISSN 1653-5146 ; 2010:002
Keyword
Microelectromechanical systems, MEMS, silicon, wafer-level, integration, heterogeneous integration, transfer integration, packaging, assembly, wafer bonding, adhesive bonding, eutectic bonding, release etching, electrochemical etching, microvalves, microactuator, Shape Memory Alloy, SMA, NITINOL, TiNi, NiTi, cold-state reset, bias spring, stress layers, crossbar switch, routing, switch, switch array, electrostatic actuator, S-shaped actuator, zipper actuator, addressing, transfer stamping, blue tape
National Category
Computer Engineering
Identifiers
urn:nbn:se:kth:diva-11833 (URN)978-91-7415-493-1 (ISBN)
Public defence
2010-02-05, Lecture Hall F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100729Available from: 2010-01-12 Created: 2010-01-04 Last updated: 2010-07-29Bibliographically approved
2. Heterogeneous Integration of Shape Memory Alloysfor High-Performance Microvalves
Open this publication in new window or tab >>Heterogeneous Integration of Shape Memory Alloysfor High-Performance Microvalves
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents methods for fabricating MicroElectroMechanical System (MEMS) actuators and high-flow gas microvalves using wafer-level integration of Shape Memory Alloys (SMAs) in the form of wires and sheets.

The work output per volume of SMA actuators exceeds that of other microactuation mechanisms, such as electrostatic, magnetic and piezoelectric actuation, by more than an order of magnitude, making SMA actuators highly promising for applications requiring high forces and large displacements. The use of SMAs in MEMS has so far been limited, partially due to a lack of cost efficient and reliable wafer-level integration approaches. This thesis presents new methods for wafer-level integration of nickel-titanium SMA sheets and wires. For SMA sheets, a technique for the integration of patterned SMA sheets to silicon wafers using gold-silicon eutectic bonding is demonstrated. A method for selective release of gold-silicon eutectically bonded microstructures by localized electrochemical etching, is also presented. For SMA wires, alignment and placement of NiTi wires is demonstrated forboth a manual approach, using specially built wire frame tools, and a semiautomatic approach, using a commercially available wire bonder. Methods for fixing wires to wafers using either polymers, nickel electroplating or mechanical silicon clamps are also shown. Nickel electroplating offers the most promising permanent fixing technique, since both a strong mechanical and good electrical connection to the wire is achieved during the same process step. Resistively heated microactuators are also fabricated by integrating prestrained SMA wires onto silicon cantilevers. These microactuators exhibit displacements that are among the highest yet reported. The actuators also feature a relatively low power consumption and high reliability during longterm cycling.

New designs for gas microvalves are presented and valves using both SMA sheets and SMA wires for actuation are fabricated. The SMA-sheet microvalve exhibits a pneumatic performance per footprint area, three times higher than that of previous microvalves. The SMA-wire-actuated microvalve also allows control of high gas flows and in addition, offers benefits of lowvoltage actuation and low overall power consumption.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. viii, 79 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:014
Keyword
Microelectromechanical systems, MEMS, silicon, wafer-level, integration, heterogeneous integration, wafer bonding, Au-Si, eutectic bonding, release etching, electrochemical etching, microvalves, microactuators, shape memory alloy, SMA, NiTinol, TiNi, NiTi, cold-state reset, bias spring, gate valves, wire bonding
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-94088 (URN)978-91-7501-304-6 (ISBN)
Public defence
2012-06-01, sal E3, Osquarsbacke 14, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120514Available from: 2012-05-14 Created: 2012-05-07 Last updated: 2012-05-14Bibliographically approved

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Stemme, Göranvan der Wijngaart, Wouter

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