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December 10, 2010 – Fujitsu Labs says it has developed a hybrid device that harvests energy and generates electricity from either heat or light, resulting in an economical device with potential use in sensor networks and medical technologies.

The technology, unveiled at this week’s IEEE International Electron Devices Meeting (IEDM 2010), addresses a key application sweetspot for such technology. Energy harvesting — converting energy from the surrounding environment to electricity, using anything from light, vibration, heat, even radio waves — removes the need for electrical wiring, power cords, and batteries, which could not only enable use of sensors in new applications and regions but also improve their use (and lower their costs) in existing ones.

The problem, though, is that energy harvesting can only put out a fraction of the power that batteries can, so more powerful devices need to be made. And since some types of devices may not work in some ambient environments (e.g. light or vibration), energy harvesting systems put together several types of these devices utilize multiple forms of external energy (e.g. heat and light, or light and vibrations). An ideal device, then, would combine the ability to convert multiple energy types.

Enter Fujitsu Labs, which says its single device can capture energy from either light or heat (the most typical forms of ambient energy), by connecting two types of semiconductor materials (P-type and N-type semiconductors) that can function as a photovoltaic cell or thermoelectric generator (Figure 1). It also can be manufactured from inexpensive organic materials to keep production costs low.

Figure 1: Single device featuring operation in both photovoltaic mode (left) and thermoelectric mode (right). (Source: Fujitsu Labs)

The technology doubles the energy-capture potential by using both ambient heat and light. In medical fields, for instance, sensors could monitor conditions such as body temperature, blood pressure, and heartbeats without batteries or electrical wiring; if neither energy source is sufficient to power the sensor, it can tap and utilize both sources. Another application: environmental sensing in remote areas for weather forecasting, where battery replacement or electric lines are problematic.

Fujitsu says it will continue to improve the hybrid device’s performance toward planned commercialization around 2015.

Figure 2: Prototype hybrid generating device manufactured
on flexible substrate. (Source: Fujitsu Labs)

 

December 10, 2010 – Fujitsu Labs says it has developed a hybrid device that harvests energy and generates electricity from either heat or light, resulting in an economical device with potential use in sensor networks and medical technologies.

The technology, unveiled at this week’s IEEE International Electron Devices Meeting (IEDM 2010), addresses a key application sweetspot for such technology. Energy harvesting — converting energy from the surrounding environment to electricity, using anything from light, vibration, heat, even radio waves — removes the need for electrical wiring, power cords, and batteries, which could not only enable use of sensors in new applications and regions but also improve their use (and lower their costs) in existing ones.

The problem, though, is that energy harvesting can only put out a fraction of the power that batteries can, so more powerful devices need to be made. And since some types of devices may not work in some ambient environments (e.g. light or vibration), energy harvesting systems put together several types of these devices utilize multiple forms of external energy (e.g. heat and light, or light and vibrations). An ideal device, then, would combine the ability to convert multiple energy types.

Enter Fujitsu Labs, which says its single device can capture energy from either light or heat (the most typical forms of ambient energy), by connecting two types of semiconductor materials (P-type and N-type semiconductors) that can function as a photovoltaic cell or thermoelectric generator (Figure 1). It also can be manufactured from inexpensive organic materials to keep production costs low.

Figure 1: Single device featuring operation in both photovoltaic mode (left) and thermoelectric mode (right). (Source: Fujitsu Labs)

The technology doubles the energy-capture potential by using both ambient heat and light. In medical fields, for instance, sensors could monitor conditions such as body temperature, blood pressure, and heartbeats without batteries or electrical wiring; if neither energy source is sufficient to power the sensor, it can tap and utilize both sources. Another application: environmental sensing in remote areas for weather forecasting, where battery replacement or electric lines are problematic.

Fujitsu says it will continue to improve the hybrid device’s performance toward planned commercialization around 2015.

Figure 2: Prototype hybrid generating device manufactured
on flexible substrate. (Source: Fujitsu Labs)

 

by Michael A. Fury, Techcet Group

December 9, 2010 – The second day of the IDTechEx combined Printed Electronics USA 2010 and Photovoltaics USA 2010 expanded from three parallel tracks to four, adding one degree of difficulty to covering the talks of interest. (Still, this was a cakewalk compared to covering an ECS or MRS meeting…I just wonder how long it will stay that way!)

Mike O’Reilly of Optomec described their ink atomizer system for printing inks up to 1000 cP viscosity and several microns thick, much more than can be done by inkjet. One application is a 3D stacked chip interconnect scheme that prints 10μm lines at a 30μm pitch. This sounds like the interconnect scheme developed by Vertical Circuits Inc., a Scotts Valley startup. The Optomec print nozzle delivers atomized ink focused by a shroud gas, so a 150μm nozzle can print 30μm traces that are 6μm tall.

Click to EnlargeJoshua Windmiller of UC San Diego talked about textile printed biosensors in the UCSD nanoengineering program. These flexible sensors are screen printed down to 100μm features on fabrics that contact the skin. Active elements include, for example, glucose oxidase in a graphite electrode on a Nafion film. Flexing the substrate exposes more active enzyme, thus enhancing the sensitivity of the sensor. The combined requirements of skin contact and flexing make the elastic waist band of underwear the obvious location for these sensors. Another example shown was a disposable wipe for high-sensitivity detection of explosives using a Gore-TEX substrate. These were not intended for use with underwear — the market consists of only one individual.

Heliovolt boasts the highest efficiency for CIGS PV at 11.5% peak, with a volume production average of >10%, noted company CEO Billy Stanbery. The material is the result of a CRADA (cooperative R&D agreement) with NREL, and is due to the exceptionally large grain size they are able to produce.

David Icke of MC10 has integrated off-the-shelf components with flexible substrates to product a class of stretchable electronics that are highly conformal. One application is a brain overlay sensor array that is 13-25μm thick. (Do not try this at home!) Other applications paper-based medical diagnostics and sensing devices.

Stan Farnsworth at NovaCentrix talked again this year about their Pulse Forge equipment that enables flash annealing of metals on plastic substrates without delamination or deformation. Tools have been shipped to labs and pilot lines, and products manufactured with the process will start to ship in 2011. In conjunction with their equipment, NovaCentrix developed a copper ink called Metalor, which is printed as copper oxide with a reducing agent. It is a screen printing paste that sells for $75/kg, making it an attractive alternative to silver paste. The reduced copper is mesoporous but still quite conductive.

Tony Killard of the Biomedical Diagnostics Institute at Dublin City University is developing a family of biosensors with screen printed materials with the intention of migrating them to inkjet systems. Demonstrated components include sensors for NH3, urea, glucose, and cholesterol. The goal is to combine several sensors into what he calls a "smart integrated miniaturized sensor system" that includes heterogeneous integration of the sensors with a display, power, electronics and communications.

Erik Garnett of Stanford described their advanced nanostructured PV that combines Si and OPV into a single cell for greater conversion efficiency. The Si substrate is processed to form vertical Si nanowire arrays for light trapping; this surface exhibits absorption 70× greater than Si with conventional surface roughening. The gaps between the Si fingers are then filled with PEDOT for the OPV component. The vertical nanowire arrays are formed by coating the Si surface with a self-assembled monolayer of uniform SiO2 spheres which act as a plasma etch mask. After Si etching, the SiO2 is removed with HF, leaving the free-standing forest of Si pillars.

Davor Sutija of Thin Film Electronics showed a family of printed rewritable permanent memory devices using a ferroelectric polymer ink that was originally co-developed with Intel. The devices are fully R2R printable, with a single roll holding 3.6M memory devices with 20 bits each. It takes 50μsec and 20μC charge to set/reset the bits. The first commercial products are for games, in the form of their Toy Development Kit now available. In October 2010 they formed an alliance with PARC for 128-bit EPC memories with bipolar transistors. In 24-30 months they expect to have system products with 1000-5000 transistors.

Warren Jackson at HP is working on ZnSnO-channel transistors for R2R production on flexible substrates. The entire device film stack is blanket deposited on the roll, including a thick photoresist top layer. The thick resist is then patterned by a 3D roller stamp, which allows regions to selectively remove the layers down to the gate for contact. They are building 7×7cm display devices as a yield learning vehicle, using the eyeball as a rapid inexpensive tester.

Stephan Kirchmeyer at Heraeus Clevios (HC Stark Clevios GmbH) is using PEDOT-PSS as an ITO replacement for OPV, achieving 100Ω/square at 90% transparency. They are also working on materials for OLED that can serve as an ITO replacement for hole injection.

Shiv Chiruvolu of NanoGram talked about their 5-10nm Si particle inks, available in both n+ and p+. The different formulations can be applied by spin coating or screen printing. Inkjet is still in development, though already achieving 70μm lines at 100μm pitch. For TFT applications, they use low temperature laser sintering <180°C on a polycarbonate substrate. The company was acquired by Teijin in July 2010.

For the final stretch of the conference, all of the attendees were brought back to a single track. However, one room provided adequate capacity for the die-hards whereas the conference opening was 3× as large.

John Knight of PARC talked about fostering the PE product development infrastructure through their collaboration with Soligie. There is a gap between PE R&D and product realization/commercialization, which this alliance intends to bridge. There is also a gap between PE R&D and materials & process & equipment suppliers, which PARC intends to bridge. The objective of this PARC-Soligie alliance is to provide one stop shopping for PE product designers, a service that does not exist elsewhere.

Jani-Mikael Kuusisto of VTT Technical Research Center of Finland described their government-funded strategic initiative to foster R&D for product development and pilot production of several technologies, including PE. Successful programs include Orion Diagnostica and PrintoCent.

Peter Harrop of event organizer IDTechEx provided the last hurrah, looking forward to PE in 2010-2020. This market is expected to be $300B in <20 years. This is not unreasonable, considering that a good portion of PE will be directed toward consumer goods, itself a whopping $3T market. "The driver is to modernize print, not electronicsm," he said.

On both days of the conference, the schedule included an extended lunch break that allowed time for the exhibit floor, networking, and supplier seminars. This is a good arrangement that returns value to the supplier effort and expense of exhibiting.

The conference concluded on Dec.3 with five more short courses. The topics were:

  • Displays and lighting
  • Creating new products with PE
  • Flexible substrates, transparent conductors, and barriers for flexible electronics
  • RFID and its progress toward being printed
  • Energy harvesting and storage for small electronic devices

 

Michael A. Fury, Ph.D, is senior technology analyst at Techcet Group, LLC, P.O. Box 29, Del Mar, CA 92014; e-mail [email protected].

(December 9, 2010) — Panasonic, core partner within imec’s Human++ program, and imec presented at the International Electron Devices Meeting (IEDM) in San Francisco various critical components of a biomedical lab-on-chip sensor enabling fast detection of Single Nucleotide Polymorphisms (SNPs) in DNA, such as a miniaturized pump for on-chip generation of high pressures, a micropillar filter optimized for DNA separation achieving record resolution, and a SNP detector allowing on-chip detection using very small sample volumes.

A SNP is a single nucleotide replacement in a DNA sequence that can result in different reaction by people to pathogens and medicines. Detection of these SNPs is increasingly important with the move towards more personalized healthcare.

Existing methods to detect SNPs require many sample processing steps in dedicated medical tools at medical laboratories. Such tests are labor-intensive, time-consuming and expensive. Moreover, large blood samples are needed. A lab-on-chip device can bring advantages to the patient and the healthcare system. Such devices enable fast, easy-to-use, cost-effective test methods which can be performed at regular times in a doctor’s office or even near the patient’s bed. This is very interesting for point-of-care applications such as personalized medicine.

By combining advanced micro-electronic fabrication processes with heterogeneous integration, imec and Panasonic aim to realize a state-of-the-art microfluidic device for SNP detection. In order to do this, advanced microfluidic components have been fabricated and optimized, such as a miniaturized pump for on-chip generation of high pressure, a micropillar filter optimized for DNA separation achieving world-record resolution, and a SNP detector allowing on-chip detection using very small sample volumes.

The entrance unit of the SNP detection system samples very small volumes of blood. This entrance unit features a miniaturized high-pressure pump based on an advanced conductive polymer actuator. After optimization, the actuator generates high pressures (up to 3MPa) at low voltage (~1.5V). The high pressure is essential to generate a fluid flow through the next unit of the SNP detection system. The on-chip low voltage operation is important because it opens the path to autonomy and portability of the lab-on-chip device.

Next, the DNA separation unit featuring an advanced micro-pillar array filter was developed. This deep-UV patterned silicon pillar array was realized using advanced MEMS technology. It consists of many micron-scale pillars, being typically 20µm high and with 1-2µm inter-pillar distance. The pillar array is used for DNA separation based on ion-pair reversed-phase (IR-RP) liquid chromatography. Imec and the VUB (Vrije Universiteit Brussel), a scientific partner of imec, optimized the pillar-based IR-RP liquid chromatography technique for DNA separation. This resulted in the first miniaturized on-chip system that enables fast and highly selective separation of short, double stranded DNA strands which only differ 50 base pairs in length. The resolution of the system is the highest in the world and proves the potential to handle 5 SNPs at the same time in the final SNP detection system.

The other functional units of the SNP detector are a unit for DNA extraction and polymerase chain reaction (PCR) using heaters and temperature sensors, and a SNP detection unit based on electrochemical sensors. The miniaturization of these sensors was of crucial importance, since the minimum required sensor volume determines the blood sampling volume needed for the SNP detection, and hence the dimensions of all components of the device. Scientists of Panasonic and imec demonstrated SNP detection capabilities using on-chip sensors handling a volume as small as 0.5µL.

Imec’s Human++ program provides a multidisciplinary R&D platform for industrial partners to collaborate on finding industry-relevant solutions for future healthcare and wellness needs by combining nanoelectronics and biotechnology into heterogeneous systems for diagnosis and therapy. Human++ partners build on imec’s 25 years of expertise in micro- and nanoelectronics and expertise in several healthcare-relevant domains.

More MEMS news from Panasonic and imec at IEDM here.

Imec performs world-leading research in nanoelectronics. Further information on imec can be found at www.imec.be.

Panasonic Corporation is a worldwide leader in the development and manufacture of electronic products for a wide range of consumer, business, and industrial needs.

The Vrije Universiteit Brussel (VUB) offers a quality education to more than 9000 students and hosts more than 150 research teams working on its campuses, and is one of the biggest centres of knowledge in the capital of Europe.

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(December 9, 2010) — The MiQro Innovation Collaborative Centre (MICC; Bromont, QC, Canada) will receive a $14.1 million grant as part of the Canadian government’s Centres of Excellence for Commercialization and Research (CECR) program. This new grant, to be paid to the MICC over five years, is in addition to $83 million from the Canadian government and $95 million from the Quebec government announced in 2009.

The investment is part of a $61.1 million program that establishes the MICC as one of five new Centres of Excellence. It is intended to accelerate and increase the MICC’s level of contribution to the Canadian and global semiconductor industries. The grant will be used to attract top researchers and add resources at the centre to support the process of translating leading-edge research into practical, commercializable industry solutions.

DALSA (Waterloo, ON, Canada) is one of the founding partners in the MICC along with IBM Canada and the Université de Sherbrooke. The MICC will house equipment for 200mm-based microelectromechanical systems (MEMS) and 3D wafer level packaging (WLP), as well as advanced technologies associated with the assembly and packaging of silicon chips.

For more information, contact DALSA at http://www.dalsa.com/

December 8, 2010 — Reno-based Altair Nanotechnologies, Inc. (Altairnano) (NASDAQ: ALTI) (NASDAQ: ALTID), has been selected by Inversiones Energéticas, S.A. de C.V. (INE), one of El Salvador’s largest electric utilities, to provide a turn-key 10 MW lithium-titanate based battery system, dubbed "ALTI-ESS," for frequency control. Energy storage solutions such as this help utilities balance power generation and load over short periods.

Under the proposed agreement, Altairnano will have responsibility for site preparation, system installation, training, final testing and commissioning of the total solution. The system will be located at INE’s Talnique power station site.

"Altairnano’s ALTI-ESS advanced battery system provides an economical solution for managing voltage and frequency fluctuations, because of its ability to rapidly absorb energy from the grid, and just as quickly discharge energy back into the grid," stated Terry Copeland, Altairnano President and Chief Executive Officer.

According to Altairnano, the nano-structured lithium titanate in the cell of the battery produces distinctive performance attributes, including extremely fast charge and discharge rates, the high round-trip efficiencies, long cycle life, safety, and ability to operate under diverse environmental and extreme temperature conditions.
Altairnano’s lithium titanate technology is also unique because it lacks a solid electrolyte interface (SEI), as shown. The SEI is a “film” on the anode that is an internal resistor that limits power output and generates heat build-up in a standard lithium-ion battery. Therefore, the lack of an SEI allows the lithium titanate battery to work efficiently in extreme temperatures and significantly reduces thermal runaway risk. In short, by removing the highly reactive graphite from the system design, and instead using nano-structured lithium titanate materials as the negative electrode material, no significant interaction takes place with the electrolyte.

The battery’s operating temperature range also is wider than that of other technologies: from -40°C to 55°C (-40°F to 131°F). This capability virtually eliminates the need for supplemental heating when the battery is used in low temperature environments and reduces or eliminates cooling requirements for high temperature operation.

Conventional lithium ion batteries can typically be charged about 1,000 times before they are considered no longer useful. In laboratory testing, the Altairnano energy storage and battery systems have achieved over 25,000 charge and discharge cycles at rates up to 40 times greater than common batteries, and still retain up to 80% of initial charge capacity.

Altairnano also claims its energy storage and battery systems deliver power per unit weight and unit volume several times greater than conventional lithium-ion batteries. Cell measurements performed with high power cell designs indicate specific power as high 4000 W/Kg and power density over 7,500 W/litre. By using nano-structured lithium titanate as the negative electrode material, the formation of an SEI, an electrochemical property that impedes the removal of lithium, which is the first step in power production, is eliminated.

December 8, 2010 — Reno-based Altair Nanotechnologies, Inc. (Altairnano) (NASDAQ: ALTI) (NASDAQ: ALTID), has been selected by Inversiones Energéticas, S.A. de C.V. (INE), one of El Salvador’s largest electric utilities, to provide a turn-key 10 MW lithium-titanate based battery system, dubbed "ALTI-ESS," for frequency control. Energy storage solutions such as this help utilities balance power generation and load over short periods.

Under the proposed agreement, Altairnano will have responsibility for site preparation, system installation, training, final testing and commissioning of the total solution. The system will be located at INE’s Talnique power station site.

"Altairnano’s ALTI-ESS advanced battery system provides an economical solution for managing voltage and frequency fluctuations, because of its ability to rapidly absorb energy from the grid, and just as quickly discharge energy back into the grid," stated Terry Copeland, Altairnano President and Chief Executive Officer.

According to Altairnano, the nano-structured lithium titanate in the cell of the battery produces distinctive performance attributes, including extremely fast charge and discharge rates, the high round-trip efficiencies, long cycle life, safety, and ability to operate under diverse environmental and extreme temperature conditions.
Altairnano’s lithium titanate technology is also unique because it lacks a solid electrolyte interface (SEI), as shown. The SEI is a “film” on the anode that is an internal resistor that limits power output and generates heat build-up in a standard lithium-ion battery. Therefore, the lack of an SEI allows the lithium titanate battery to work efficiently in extreme temperatures and significantly reduces thermal runaway risk. In short, by removing the highly reactive graphite from the system design, and instead using nano-structured lithium titanate materials as the negative electrode material, no significant interaction takes place with the electrolyte.

The battery’s operating temperature range also is wider than that of other technologies: from -40°C to 55°C (-40°F to 131°F). This capability virtually eliminates the need for supplemental heating when the battery is used in low temperature environments and reduces or eliminates cooling requirements for high temperature operation.

Conventional lithium ion batteries can typically be charged about 1,000 times before they are considered no longer useful. In laboratory testing, the Altairnano energy storage and battery systems have achieved over 25,000 charge and discharge cycles at rates up to 40 times greater than common batteries, and still retain up to 80% of initial charge capacity.

Altairnano also claims its energy storage and battery systems deliver power per unit weight and unit volume several times greater than conventional lithium-ion batteries. Cell measurements performed with high power cell designs indicate specific power as high 4000 W/Kg and power density over 7,500 W/litre. By using nano-structured lithium titanate as the negative electrode material, the formation of an SEI, an electrochemical property that impedes the removal of lithium, which is the first step in power production, is eliminated.

(December 8, 2010) — Given their outstanding mechanical and electrical properties, carbon nanotubes (CNTs) are attractive building blocks for next-generation nanoelectromechanical system (NEMS) devices, including high-performance sensors, logic devices, and memory elements. Researchers at Northwestern University, the Center for Integrated Nanotechnologies at Sandia and Los Alamos National Laboratories, and Binghamton University have found a way to dramatically improve the reliability of carbon nanotube-based nanoelectromechanical systems.

Previously, manufacturing challenges associated with creating well-ordered arrays of individual carbon nanotubes and the nanotube-devices’ prevalent failure modes have prevented any large-scale commercial use. The new results are published in the journal Small.

"Depending on their geometry, these devices have a tendency to stick shut, burn or fracture after only a few cycles," said Horacio Espinosa, James N. and Nancy J. Professor in the McCormick School of Engineering at Northwestern University. "This significantly limits any practical application of such nano devices. Our discovery may be a key to advancing carbon nanotube-based nanoelectromechanical systems from laboratory-scale demonstrations to viable and attractive alternatives to many of our current microelectronic devices." Read more about MEMS manufacturing, packaging, and more here.

To date, carbon nanotube-based nanoelectromechanical devices have ubiquitously used metal, thin-film electrodes. The Northwestern University group in collaboration with SANDIA investigators replaced these electrodes with electrodes made from diamond-like carbon (an electrically-conductive and mechanical robust material), which suppressed the onset of failure. This enabled them to demonstrate the first example of nanoelectromechanical devices constructed from individual CNTs switching reliably over numerous cycles and apply this functionality to memory elements that store binary states.

The team used a carbon nanotube-based nanoelectromechanical switch as a platform to study failure modes and investigate potential solutions. "This represents a significant step in the maturation of carbon nanotube-based device technology," Espinosa said.

"This switch shares operating principles, and thus failure modes, with numerous reported devices," said Owen Loh, a graduate student in Espinosa’s lab. "In this way, we hope the results will be broadly applicable."

First, the team conducted a parametric study of the design space of devices using conventional metal electrodes. This enabled identification of the point of onset of the various failure modes within the design space and highlighted the highly limited region in which the devices would function reliably without failure. They then used computational models to explain the underlying mechanisms for the experimentally-observed modes of failure.

"Using these models, we can replicate the geometry of the devices tested and ultimately explain why they fail," said Xiaoding Wei, a post-doctoral fellow in Espinosa’s lab.

The team then demonstrated that using alternative electrode materials like diamond-like carbon could greatly improve the reliability of these devices. They repeated a similar parametric study using diamond-like carbon electrodes rather than metal thin films and found a dramatic improvement in device robustness. This enabled reliable switching of the carbon nanotube-based devices through numerous cycles, as well as application to the volatile storage of binary "0" and "1" states.

Other co-authors of the paper include Changhong Ke and John Sullivan.

This work was supported by the Army Research Office and National Science Foundation, and was performed in part at the Center for Integrated Nanotechnologies, a U.S. Department of Energy facility at Los Alamos National laboratory and Sandia National Laboratories, and in part at the Center for Nanoscale Materials.

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(December 8, 2010 – PRNewswire) — Audax Medical Inc., a privately held medical device company specializing in the development of osteobiologics, has entered into a comprehensive license agreement with Brown University, acquiring exclusive rights to a proprietary osteobiologic nanotechnology. The biomaterial, Arxis, is being developed for use in multiple clinical applications for the regeneration of diseased bone, cartilage, and other soft tissues. 

Figure. Twin-based linker molecules, top left, self-assemble into six-molecule rings. Stacked in a tube shape, the rings of molecules not only provide a new scaffold for bone growth, but can also store growth factors and helpful drugs inside. Credit: Websterlab/Brown University

An additional research agreement has been completed with the Brown University School of Engineering and Department of Orthopedics to further support clinical development of the technology. The technology will be used to expand Audax Medical’s regenerative osteobiologics and soft tissue platforms.

Under the terms of the agreement, Audax Medical has obtained exclusive license to a platform of intellectual property and technologies co-developed by Thomas Webster, Brown professor of engineering, addressing the treatment of degenerative bone and soft tissues.

The Arxis biomaterial consists of organic nanomolecules that have the potential to meet an array of clinical needs. The implantable material can incorporate varying growth agents that allow its end characteristics to be customized for multiple clinical and regenerative indications throughout the musculoskeletal system.

More information about the science behind the technology, including pictures and video, can be found at http://today.brown.edu/articles/2010/11/audax.

Audax Medical Inc. is a privately held medical device company developing treatment of degenerative bone and musculoskeletal tissue by promoting the growth of natural bone and tissue. For more information visit, www.audaxmed.com

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December 7, 2010 – At this week’s IEDM 2010 in San Francisco, IMEC and Panasonic are revealing a SiGe thin-film packaged SOI-based MEMS resonator with the industry’s highest-recorded quality factor ("Q factor") — i.e., the ratio of energy stored vs. energy dissipated during a cycle.

MEMS resonators’ desirability vs. traditional resonators (quartz crystals, piezoelectrics) include miniaturization, better frequency stability, integration with CMOS, use of standard IC packaging, and ideally lower costs — but they also tend to have a lower Q factor and high bias voltage. (A higher Q factor means lower energy dissipation, thus oscillations persist longer.) Panasonic and IMEC addressed this in two ways:

— Applying a torsional vibration mode (Figure 1), enabling low anchor losses and lower squeeze film damping (vs. flexural mode resonators).

— Vacuum-encapsulating it in a thin-film package (Figure 2): 4μm thick SiGe film, realized with monolithic fabrication process with the MEMS.

Click to Enlarge
Figure 1: Illustration of the torsional vibration mode. (Source: IMEC)

The result: a record-high Q factor: 220,000 at 20MHz resonant frequency (f • Q product of 4.3 × 1012Hz).

A narrow 130nm gap between the beam/drive and sense electrodes enables a low bias voltage (1.8Vdc), eliminating the need for a charge pump in the oscillator circuit. Sacrificial layer etching through a microcrystalline SiGe layer minimizes deposition of sealing material inside the cavity, so etching holes can be better lined up with the beam surface.

IMEC and Panasonic built the device through IMEC’s CMORE service.

Click to Enlarge
Figure 2: SEM of a cross-sectional structure of the
developed packaged MEMS resonator. (Source: IMEC)