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Wafer-Scale Manufacturing of Bulk Shape-Memory-Alloy Microactuators Based on Adhesive Bonding of Titanium-Nickel Sheets to Structured Silicon Wafers
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).ORCID iD: 0000-0001-6443-878X
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 microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 18, no 6, 1309-1317 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a concept for the wafer-scale manufacturing of microactuators based on the adhesive bonding of bulk shape-memory-alloy (SMA) sheets to silicon microstructures. Wafer-scale integration of a cold-state deformation mechanism is provided by the deposition of stressed films onto the SMA sheet. A concept for heating of the SMA by Joule heating through a resistive heater layer is presented. Critical fabrication issues were investigated, including the cold-state deformation, the bonding scheme and related stresses, and the titanium-nickel (TiNi) sheet patterning. Novel methods for the transfer stamping of adhesive and for the handling of the thin TiNi sheets were developed, based on the use of standard dicing blue tape. First demonstrator TiNi cantilevers, wafer-level adhesively bonded on a microstructured silicon substrate, were successfully fabricated and evaluated. Intrinsically stressed silicon dioxide and silicon nitride were deposited using plasma-enhanced chemical vapor deposition to deform the cantilevers in the cold state. Tip deflections for 2.5-mm-long cantilevers in cold/hot state of 250/70 and 125/28 mu m were obtained using silicon dioxide and silicon nitride, respectively. The bond strength proved to be stronger than the force created by the 2.5-mm-long TiNi cantilever and showed no degradation after more than 700 temperature cycles. The shape-memory behavior of the TiNi is maintained during the integration process.

Place, publisher, year, edition, pages
2009. Vol. 18, no 6, 1309-1317 p.
Keyword [en]
National Category
Nano Technology
URN: urn:nbn:se:kth:diva-11828DOI: 10.1109/jmems.2009.2035368ISI: 000272318900016ScopusID: 2-s2.0-71549169015OAI: diva2:284096


Available from: 2010-01-04 Created: 2010-01-04 Last updated: 2015-09-30Bibliographically 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.
Trita-EE, ISSN 1653-5146 ; 2010:002
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
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)
QC20100729Available from: 2010-01-12 Created: 2010-01-04 Last updated: 2010-07-29Bibliographically approved

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