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Heterogeneous material integration for MEMS
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.ORCID iD: 0000-0002-9820-8728
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes heterogeneous integration methods for the fabrication of microelectromechanical systems (MEMS). Most MEMS devices reuse the fabrication techniques that are found in the microelectronics integrated circuit industry. This limits the selection of materials and processes that are feasible for the realization of MEMS devices. Heterogeneous integration methods, on the other hand, consist of the separate pre-fabrication of sub-components followed by an assembly step. The pre-fabrication of subcomponents opens up for a wider selection of fabrication technologies and thus potentially better performing and more optimized devices. The first part of the thesis is focused upon an adhesive wafer-level layer transfer method to fabricate resistive microbolometer-based long-wavelength infrared focal plane arrays. This is realized by a CMOS-compatible transfer of monocrystalline silicon with epitaxially grown silicon-germanium quantum wells. Heterogeneous transfer methods are also used for the realization of filtering devices, integration of distributed small dies onto larger wafer formats and to fabricate a graphene-based pressure sensor. The filtering devices consist of very fragile nano-porous membranes that with the presented dry adhesive methods can be transferred without clogging or breaking. Pick-and-place methods for the massive transfer of small dies between different wafer formats are limited by time and die size-considerations. Our presented solution solves these problems by expanding a die array on a flexible tape, followed by adhesive wafer bonding to a target wafer. Furthermore, a gauge pressure sensor is realized by transferring a graphene monolayer grown on a copper foil to a micromachined target wafer with a silicon oxide interface layer. This device is used to extract the gauge factor of graphene. Adhesive bonding is an enabling technology for the presented heterogeneous integration techniques. A blister test method together with an experimental setup to characterize the bond energies between adhesives and bonded substrates is also presented.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xii, 87 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:039
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-129185OAI: oai:DiVA.org:kth-129185DiVA: diva2:650511
Public defence
2013-10-25, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20131003

Available from: 2013-10-03 Created: 2013-09-22 Last updated: 2013-10-04Bibliographically approved
List of papers
1. Heterogeneous 3D integration of 17 mu m pitch Si/SiGe quantum well bolometer arrays for infrared imaging systems
Open this publication in new window or tab >>Heterogeneous 3D integration of 17 mu m pitch Si/SiGe quantum well bolometer arrays for infrared imaging systems
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2013 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 4, 045017- p.Article in journal (Refereed) Published
Abstract [en]

This paper reports on the realization of 17 mu m x 17 mu m pitch bolometer arrays for uncooled infrared imagers. Microbolometer arrays have been available in primarily defense applications since the mid-1980s and are typically based on deposited thin films on top of CMOS wafers that are surface-machined into sensor pixels. This paper instead focuses on the heterogeneous integration of monocrystalline Si/SiGe quantum-well-based thermistor material in a CMOS-compliant process using adhesive wafer bonding. The high-quality monocrystalline thermistor material opens up for potentially lower noise compared to commercially available uncooled microbolometer arrays together with a competitive temperature coefficient of resistance (TCR). Characterized bolometers had a TCR of -2.9% K-1 in vacuum, measured thermal conductances around 5 x 10(-8) WK-1 and thermal time constants between 4.9 and 8.5 ms, depending on the design. Complications in the fabrication of stress-free bolometer legs and low-noise contacts are discussed and analyzed.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-106201 (URN)10.1088/0960-1317/23/4/045017 (DOI)000316299900018 ()2-s2.0-84878081474 (ScopusID)
Note

QC 20130422. Updated from submitted to published.

Available from: 2012-11-29 Created: 2012-11-29 Last updated: 2013-10-03Bibliographically approved
2. Very Large Scale Heterogeneous Integration (VLSHI) and Wafer-Level Vacuum Packaging for Infrared Bolometer Focal Plane Arrays
Open this publication in new window or tab >>Very Large Scale Heterogeneous Integration (VLSHI) and Wafer-Level Vacuum Packaging for Infrared Bolometer Focal Plane Arrays
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2013 (English)In: Infrared physics & technology, ISSN 1350-4495, Vol. 60, 251-259 p.Article in journal (Refereed) Published
Abstract [en]

Imaging in the long wavelength infrared (LWIR) range from 8 to 14 μm is an extremely useful tool for non-contact measurement and imaging of temperature in many industrial, automotive and security applications. However, the cost of the infrared (IR) imaging components has to be significantly reduced to make IR imaging a viable technology for many cost-sensitive applications. This paper demonstrates new and improved fabrication and packaging technologies for next-generation IR imaging detectors based on uncooled IR bolometer focal plane arrays. The proposed technologies include very large scale heterogeneous integration for combining high-performance, SiGe quantum-well bolometers with electronic integrated read-out circuits and CMOS compatible wafer-level vacuum packing. The fabrication and characterization of bolometers with a pitch of 25 μm × 25 μm that are arranged on read-out-wafers in arrays with 320 × 240 pixels are presented. The bolometers contain a multi-layer quantum well SiGe thermistor with a temperature coefficient of resistance of −3.0%/K. The proposed CMOS compatible wafer-level vacuum packaging technology uses Cu–Sn solid–liquid interdiffusion (SLID) bonding. The presented technologies are suitable for implementation in cost-efficient fabless business models with the potential to bring about the cost reduction needed to enable low-cost IR imaging products for industrial, security and automotive applications.

Keyword
Very large scale heterogeneous integration, Thermal imaging, MEMS, Bolometer, IR
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-106202 (URN)10.1016/j.infrared.2013.05.006 (DOI)000324004900034 ()2-s2.0-84879956633 (ScopusID)
Note

QC 20131003 Updated from Submitted to Published

Available from: 2012-11-29 Created: 2012-11-29 Last updated: 2013-11-06Bibliographically approved
3. Wafer bonding with nano-imprint resists as sacrificial adhesive for fabrication of silicon-on-integrated-circuit (SOIC) wafers in 3D integration of MEMS and ICs
Open this publication in new window or tab >>Wafer bonding with nano-imprint resists as sacrificial adhesive for fabrication of silicon-on-integrated-circuit (SOIC) wafers in 3D integration of MEMS and ICs
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2009 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, Vol. 154, no 1, 180-186 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we present the use of thermosetting nano-imprint resists in adhesive wafer bonding. The presented wafer bonding process is suitable for heterogeneous three-dimensional (3D) integration of microelectromechanical systems (MEMS) and integrated circuits (ICs). Detailed adhesive bonding process parameters are presented to achieve void-free, well-defined and uniform wafer bonding interfaces. Experiments have been performed to optimize the thickness control and uniformity of the nano-imprint resist layer in between the bonded wafers. In contrast to established polymer adhesives such as, e.g., BCB, nano-imprint resists as adhesives for wafer-to-wafer bonding are specifically suitable if the adhesive is intended as sacrificial material. This is often the case, e.g., in fabrication of silicon-on-integrated-circuit (SOIC) wafers for 3D integration of MEMS membrane structures on top of IC wafers. Such IC integrated MEMS includes. e.g., micro-mirror arrays, infrared bolometer arrays, resonators, capacitive inertial sensors, pressure sensors and microphones.

Keyword
Adhesive wafer bonding, Nano-imprint resist, Polymer, 3D IC MEMS, integration, Silicon-on-integrated-circuit, SOIC, nanoimprint lithography, polymer deformation, arrays, thermosets, design, flow
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-18753 (URN)10.1016/j.sna.2009.07.009 (DOI)000269771200028 ()2-s2.0-68849118449 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2013-10-03Bibliographically approved
4. A Comparative study of the bonding energy in adhesive wafer bonding
Open this publication in new window or tab >>A Comparative study of the bonding energy in adhesive wafer bonding
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2013 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 8, 1-7 p.Article in journal (Refereed) Published
Abstract [en]

Adhesion energies are determined for three different polymers currently used in adhesive wafer bonding of silicon wafers. The adhesion energies of the polymer off-stoichiometry thiol-ene-epoxy OSTE+ and the nano-imprint resist mr-I 9150XP are determined. The results are compared to the adhesion energies of wafers bonded with benzocyclobutene, both with and without adhesion promoter. The adhesion energies of the bonds are studied by blister tests, consisting of delaminating silicon lids bonded to silicon dies with etched circular cavities, using compressed nitrogen gas. The critical pressure needed for delamination is converted into an estimate of the bond adhesion energy. The fabrication of test dies and the evaluation method are described in detail. The mean bond energies of OSTE+ were determined to be 2.1 and 20 J m(-2) depending on the choice of the epoxy used. A mean bond energy of 1.5 J m(-2) was measured for mr-I 9150XP.

Keyword
Microfluidic Devices, SU-8, Benzocyclobutene, Level, BCB, wafer bonding, heterogeneous integration
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Nano Technology
Identifiers
urn:nbn:se:kth:diva-127487 (URN)10.1088/0960-1317/23/8/085019 (DOI)000322221100021 ()2-s2.0-84881171360 (ScopusID)
Projects
M&M
Funder
EU, European Research Council, MM 277879
Note

QC 20130902

Available from: 2013-09-02 Created: 2013-08-30 Last updated: 2015-06-26Bibliographically approved
5. Dry adhesive bonding of nanoporous inorganic membranes to microfluidic devices using the OSTE(+) dual-cure polymer
Open this publication in new window or tab >>Dry adhesive bonding of nanoporous inorganic membranes to microfluidic devices using the OSTE(+) dual-cure polymer
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2013 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 2, 025021- p.Article in journal (Refereed) Published
Abstract [en]

We present two transfer bonding schemes for incorporating fragile nanoporous inorganic membranes into microdevices. Such membranes are finding increasing use in microfluidics, due to their precisely controllable nanostructure. Both schemes rely on a novel dual-cure dry adhesive bonding method, enabled by a new polymer formulation: OSTE(+), which can form bonds at room temperature. OSTE(+) is a novel dual-cure ternary monomer system containing epoxy. After the first cure, the OSTE(+) is soft and suitable for bonding, while during the second cure it stiffens and obtains a Young's modulus of 1.2 GPa. The ability of the epoxy to react with almost any dry surface provides a very versatile fabrication method. We demonstrate the transfer bonding of porous silicon and porous alumina membranes to polymeric microfluidic chips molded into OSTE(+), and of porous alumina membranes to microstructured silicon wafers, by using the OSTE(+) as a thin bonding layer. We discuss the OSTE(+) dual-cure mechanism, describe the device fabrication and evaluate the bond strength and membrane flow properties after bonding. The membranes bonded to OSTE(+) chips delaminate at 520 kPa, and the membranes bonded to silicon delaminate at 750 kPa, well above typical maximum pressures applied to microfluidic circuits. Furthermore, no change in the membrane flow resistance was observed after bonding.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2013
Keyword
Porous-Silicon, Mass-Spectrometry, Soft Lithography, DNA
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-116596 (URN)10.1088/0960-1317/23/2/025021 (DOI)000313752800021 ()2-s2.0-84877980868 (ScopusID)
Projects
Positive
Funder
EU, FP7, Seventh Framework Programme, 257401EU, European Research Council, 277879
Note

QC 20130125

Available from: 2013-01-25 Created: 2013-01-22 Last updated: 2013-10-03Bibliographically approved
6. Batch Transfer of Radially Expanded Die Arrays for Heterogeneous Integration Using Different Wafer Sizes
Open this publication in new window or tab >>Batch Transfer of Radially Expanded Die Arrays for Heterogeneous Integration Using Different Wafer Sizes
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2012 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 21, no 5, 1077-1083 p.Article in journal (Refereed) Published
Abstract [en]

This paper reports on the realization of a novel method for batch transfer of multiple separate dies from a smaller substrate onto a larger wafer substrate by using a standard matrix expander in combination with an elastic dicing tape and adhesive wafer bonding. We demonstrate the expansion and transfer of about 30 000 dies from a 100-mm wafer format to a 200-mm wafer. Furthermore, multiple expansions of 100-mm wafers diced into 60 000 dies are evaluated to determine the position accuracy between different expansions. Fabrication, evaluation method, and results are presented.

Keyword
Stretchable electronics, flexible substrate, heterogeneous integration
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-95430 (URN)10.1109/JMEMS.2012.2203105 (DOI)000309731400010 ()2-s2.0-84867098549 (ScopusID)
Funder
EU, European Research Council, 267528
Note

QC 20121116

Available from: 2012-05-24 Created: 2012-05-24 Last updated: 2013-10-03Bibliographically approved
7. Electromechanical Piezoresistive Sensing in Suspended Graphene Membranes
Open this publication in new window or tab >>Electromechanical Piezoresistive Sensing in Suspended Graphene Membranes
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2013 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 13, no 7, 3237-3242 p.Article in journal (Refereed) Published
Abstract [en]

Monolayer graphene exhibits exceptional electronic and mechanical properties, making it a very promising material for nanoelectromechanical devices. Here, we conclusively demonstrate the piezoresistive effect in graphene in a nanoelectromechanical membrane configuration that provides direct electrical readout of pressure to strain transduction. This makes it highly relevant for an important class of nanoelectromechanical system (NEMS) transducers. This demonstration is consistent with our simulations and previously reported gauge factors and simulation values. The membrane in our experiment acts as a strain gauge independent of crystallographic orientation and allows for aggressive size scalability. When compared with conventional pressure sensors, the sensors have orders of magnitude higher sensitivity per unit area.

Keyword
Graphene, pressure sensor, piezoresistive effect, nanoelectromechanical systems (NEMS), MEMS
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-124556 (URN)10.1021/nl401352k (DOI)000321884300038 ()2-s2.0-84880160546 (ScopusID)
Funder
EU, European Research Council, 228229 277879 307311
Note

QC 20130711

Available from: 2013-07-10 Created: 2013-07-10 Last updated: 2016-06-10Bibliographically approved

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