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9 - Packaging
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- By Harrie A. C. Tilmans, Interuniversity Microelectronics Center (IMEC), Anne Jourdain, Interuniversity Microelectronics Center (IMEC), Piet De Moor, Interuniversity Microelectronics Center (IMEC)
- Edited by Stepan Lucyszyn, Imperial College of Science, Technology and Medicine, London
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- Book:
- Advanced RF MEMS
- Published online:
- 05 February 2014
- Print publication:
- 19 August 2010, pp 232-270
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Summary
Introduction
MEMS devices, unlike conventional ICs, contain movable fragile parts that must be packaged in a clean and stable environment. The package or encapsulation should not only offer protection to the MEMS during operation but also during fabrication. The specific ambient (i.e. gas composition and pressure) of the package housing depends on the type of RF MEMS. For instance, switches are preferably housed in an inert ambient (e.g. dry nitrogen) at, or slightly below, atmospheric pressure. The same applies to RF MEMS variable capacitors and tuneable inductors. Micromechanical resonators, on the other hand, require a high level of vacuum (e.g. ambient pressure <1 Pa) to attain high-frequency stability and to have sufficiently low damping at resonance. Practically, all MEMS are adversely affected by corrosive ambients like moisture. To ensure stability of the MEMS, the package must offer hermetic (or near-hermetic) seals. Sealing and encapsulation are crucial to provide the required reliability of the packaged devices.
Essentially, two approaches for device encapsulation can be defined. Encapsulation can be accomplished using conventional 1-level ceramic (e.g. LTCC), AlN or metal canister (usually abbreviated to ‘can’) packages [1]. The 1-level package consists of the chip’s capsule and associated leads for interconnecting the chip to the outside world [1]. For ceramic packages, encapsulation can be achieved by soldering or brazing a ceramic cap or lid to a metal sealing ring on the substrate, thus defining the cavity housing of the MEMS device [1–4]. Metal hermetic packages are commonly welded, soldered or brazed [1, 4, 5]. Cavity formation during 1-level packaging is an established method and allows a certain flexibility with respect to the composition of sealing gas and pressure, but ceramic or metal packages are expensive. The high cost of 1-level packaging is viable for telecommunications base stations, satellites and defence systems, but not for high-volume applications like mobile phone handsets. Furthermore, 1-level packaging poses technological complications – mainly due to handling of the MEMS after their release. For instance, the standard wafer sawing or the injection moulding process of plastic packages cannot be used, because it may destroy or contaminate the released MEMS device. Once the wafer is diced, the MEMS chips must be handled in an extremely clean environment, because cleaning in a liquid is no longer possible at this stage. All this suggests that packaging is preferably carried out during wafer processing, prior to die singulation.
13 - Industry roadmap for RF MEMS
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- By Jérémie Bouchaud, Wicht Technologie Consulting (WTC), Roberto Sorrentino, University of Perugia, Bernardo Knoblich, Wicht Technologie Consulting (WTC), Harrie A. C. Tilmans, Interuniversity Microelectronics Center (IMEC), Fabio Coccetti, Centre National de la Recherche Scientifique - Laboratoire d’Analyse et d’Architecture des Systèmes (CNRS-LAAS)
- Edited by Stepan Lucyszyn, Imperial College of Science, Technology and Medicine, London
-
- Book:
- Advanced RF MEMS
- Published online:
- 05 February 2014
- Print publication:
- 19 August 2010, pp 359-403
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Summary
Introduction
This chapter aims at provide a medium-term perspective for the future developments of RF MEMS technology up to 2020. This work is essentially based on the final report delivered by the EU-funded FP6 project Applied Research Roadmap for RF Micro/nano Systems Opportunities (ARRRO), a Coordinated Action whose aim was “to assess the current status and develop a vision of the future requirements for RF MEMS and RF NEMS technology, products and applications”. The roadmap described here is uniquely based on approximately 80 interviews with industrial companies (either developing or assessing the potential use of RF MEMS). Unlike other studies, which are based on data gained from the open literature, the findings presented here paint a more realistic future roadmap, from an industrial perspective.
Unlike ARRRO's report, which essentially refers to RF MEMS in the broad sense of RF microsystems technology (MST), only RF MEMS devices with movable parts are considered here. Having said this, reference is occasionally made to fixed micromachined devices (e.g. inductors), BAW and micromechanical resonators. With this in mind, a comprehensive roadmap in graphical form for RF MST components is shown in Fig. 13.1.
Pulsed DC Sputtered Aluminum Nitride: A Novel Approach To Control Stress And C-axis Orientation
- Philippe Soussan, Kathy O'Donnell, Jan D'Haen, Geert Vanhoyland, Eric Beyne, Harrie A. C. Tilmans
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- Journal:
- MRS Online Proceedings Library Archive / Volume 833 / 2004
- Published online by Cambridge University Press:
- 01 February 2011, G2.2
- Print publication:
- 2004
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This paper reports on a novel low temperature sputter deposition of AlN on an Al substrate, yielding films with stresses and crystalline orientation comparable to those of films deposited on Pt. The study focuses on the importance of the initial film growth step on both the stress and crystalline orientation of the film. The AlN layer is deposited using Pulsed DC (250 kHz, 90% duty cycle) magnetron reactive sputtering (93% N2, 7% Ar) using an Al target. The substrates are 150mm Si wafers with an aluminum seed layer (100 nm). The thickness of the AlN films is ≈2.5μm with uniformity across the wafer of 0.4%. The films were deposited in 4 passes of 0.625μm each to avoid overheating of the substrate. The influence of the substrate bias (0 V, 80 V and 120V) and argon pre-sputtering of the aluminum substrate been investigated. The film stress, and to a smaller extent the crystalline orientation, were mainly driven by the properties of the film deposited during the first pass. The bias is useful at the beginning of the film growth for stress control. This study suggests that it is beneficial not to use bias during the entire film deposition. With this approach, it was possible to deposit c-axis oriented AlN layers on Al with a FWHM of the rocking curve of 1.63° and low stress (<300MPa).
RF-MEMS: Materials and technology, integration and packaging
- Harrie A. C. Tilmans
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- Journal:
- MRS Online Proceedings Library Archive / Volume 783 / 2003
- Published online by Cambridge University Press:
- 01 February 2011, B6.6
- Print publication:
- 2003
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MEMS technology is rapidly emerging as an enabling technology to yield a new generation of highperformance RF-MEMS passives, like switches, tunable capacitors, high-Q resonators and tunable filters. This paper presents the progress in RF-MEMS device and package development with focus on relevant technology and material issues. The importance of wafer-level or 0-level packaging of the RF-MEMS devices is elucidated. Examples of 1-level packaging, e.g., chip-on-board or plastic molded 1-level package, are briefly described. The paper concludes in stipulating how integration of RF-MEMS passives with other passives (as inductors, LC filters, SAW devices) and active circuitry (RFICs) can lead to so-called “RF-MEMS system-in-a-package (RF-MEMS-SiP)” modules. The evolution of the RF-MEMS-SiP technology is illustrated using IMEC's microwave multi-layer thin film MCM-D technology.