Better Pressure Sensing in a Different Mode

IME researchers have described a pressure sensor that exploits nanowire field-effect transistor principles in the subthreshold mode. Compared to its inversion operation mode, the device exhibited 1000x enhancement in signal-to-noise ratio (S/N) and 4x increased pressure sensitivity in subthreshold mode, suitable for miniature low power pressure sensors.

Reference:

Pushpapraj Singh et. al., “Gate-bias controlled sensitivity and signal-to-noise ratio enhancement in nanowire FET pressure sensor," J. Micromech. Microeng., Vol 21, 105007, 2011

FUSI: Gateway to Integration

IME researchers have designed and developed an integration scheme with a Ni fully silicided (FUSI) gate on a vertical nanowire-based metal-oxide-semiconductor field-effect transistors (MOSFET). The scheme enables nanowire devices to be incorporated into circuits as the threshold voltage (V_T) can now be tuned independently. The scheme also favours further scaling down and could be applied to produce multiple V_T devices in logic circuits under the same doping conditions.

Reference:

Z. X. Chen et. al., "Realization of Ni fully silicided gate on vertical Si nanowire MOSFETs for adjusting threshold voltage (V_T)," IEEE Electron Device Letters, Vol 32, Pg 1495 - 1497, 2011

Telecommunications: Perfecting Plastic

IME researchers have developed a pluggable large core step index plastic optical fibre (POF) for high data transmission in ultra short reach networks. The new POF uses tapered fibre tips as built-in conditioners, which together with the insertion of plug-in modules, enables transmission of 2.5 Gb/s of data – 17x faster transmission rate than conventional large core step-index POF technology. Compared to multimodal glass fibre solutions used in today’s telecom short range networks, IME’s POF offers faster data rate, increased flexibility and reduced maintenance costs for ultra short reach networks.

Reference:

J. Chandrappan et. al., “A Pluggable Large Core Step Index Plastic Optical Fiber with Built-In Mode Conditioners for Gigabit Ultra Short Reach Networks," IEEE Transactions on Advanced Packaging, Vol 33, Pg 868 - 875, 2010

Junctionless SONOS Memory: Seamless Storage

IME researchers have developed a novel SONOS memory for next generation ultra-high density memory applications. Compared to conventional planar SONOS memory cell, the absence of a junction in the cell is much more amenable to device miniaturisation as the fabrication complexity and cost are significantly reduced. The junctionless SONOS memory exhibited high on/off ratio, full memory functionality with high read/write speed and excellent reliability performance.

Reference:

Y. Sun et. al., “Junctionless Vertical-Si-Nanowire-Channel-Based SONOS Memory with 2-bit Storage per Cell," IEEE Electron Device Letters, Vol 32, Pg 725 - 727, 2011

Thermoelectric Power Generator: A Cool Chip

IME researchers have developed and demonstrated a Si nanowire based thermoelectric generator (TEG) for site-specific cooling applications. Conventional TEGs are based on bulk materials that are expensive, and are not amenable to scaling and integration with conventional electronics. Not only is the proposed TEG CMOS-compatible and scalable, it enables ready integration onto a chip level. The integrated chip size TEG could be used in miniature medical devices and high performance computing units for temperature control purpose.

Reference:

Y. Li et. al., "Chip-level Thermoelectric Power Generators Based on High-density Silicon Nanowire Array Prepared with Top-down CMOS Technology," IEEE Electron Device Letters, Vol 32, Pg 674 - 676, 2011

Optical and Electrical Interconnect: Linking Up

IME researchers have developed an integrated optical carrier with low coupling loss and good alignment tolerance for high-speed photonics applications. The proposed carrier is fabricated by a novel self alignment approach, which is straight-forward and uses standard commercially available components. Optical carriers made with conventional alignment approaches require complex process development that is time-consuming and costly. The proposed carrier exhibited a misalignment assembly tolerance of +40µm (for decrement of 0.5 dB) - competitive with that made by conventional alignment approaches but is simpler and less costly to implement.

Reference:

Teck Guan Lim et. al., "Integrated Optical Carrier for Optical/Electrical Interconnect," IEEE Transactions on Components, Packaging and Manufacturing Technology, Vol 1, Pg 125 - 132, 2011

Microfluidics for Encapsulation: Pinball Style

IME researchers have developed a novel microfluidics technique which uses micropillars to generate and encapsulate polyelectrolyte microcapsules. With the proposed technique, the deposition of three bi-layers of polyelectrolytes was demonstrated in less than 3 minutes, significantly faster than conventional bulky methods that take up to several hours. The set-up is simple in design, scalable and uses a fraction of the chemical consumption required. The new technique is suitable for biomedical and food processing applications involving drug encapsulation and food emulsification, respectively.

Reference:

Chaitanya Kantak et. al., "A 'microfluidic pinball' for on-chip generation of Layer-by-Layer polyelectrolyte microcapsules," Lab Chip, Vol 11, Pg 1030 - 1035, 2011

Heart Monitoring On-the-Go

IME researchers have developed a real-time multifunctional integrated electrocardiogram (ECG) signal processing scheme. The proposed design is implemented on application-specific integrated circuits (ASIC) with 0.18 μm CMOS technology. The use of a simple generic signal processing algorithm enables the integration of multiple functions without sacrificing power consumption (29 μW) and compactability (3mm²). These desirable features are highly suitable for wearable ECG applications for long-term cardiac monitoring.

Reference:

Xin Liu et. al., "Multiple Functional ECG Signal Processing for Wearable Applications of Long-term Cardiac Monitoring," IEEE Transactions on Biomedical Engineering, Vol 58, No. 2, Pg 380 - 389, 2011

Biosensors: Spotting Abdominal Lesions

IME researchers have developed a novel wireless tagging module for precise location marking in capsule endoscopy. The module comprises a thermo-mechanical actuator and a biocompatible radio opaque micro tag. Ex vivo animal experiments demonstrated that the embedded tags could be picked up by x-ray imaging to enable precise location of problem areas in the gastrointestinal (GI) tract. The proposed module is expected to greatly improve surgical treatment outcome for patients.

Photonics: Double Twist

IME researchers have developed a silicon waveguide based tranverse electrical (TE) mode converter to mitigate against polarization in waveguides - a major roadblock in manufacturing. The proposed converter is designed to convert optical signals between a horizontal and a vertical waveguide (and vice-versa); it also serves as a critical component to realise IME's polarity diversity scheme. The converter demonstrated good polarization extinction ratio of 17 dB at 5 µm transition length and an insertion loss of less than 2dB. Compared to reported polarization diversity schemes using mode-coupling-based rotators, the proposed scheme (with the converter) is more fabrication-friendly as it exhibits higher dimensional tolerance.

Solar Cells: Pillars of Light

IME researchers have investigated and modeled the impact of key factors on the electrical performance of Si nanopillar array surface textured thin-film based solar cells. Conventional solar cells are made from expensive high quality bulk Si wafer to attain high power conversion efficiency (PCE). Results from this study validated the use of nanopillar arrays as a viable light trapping scheme using low-grade Si thin-films to make efficient and low-cost solar cells that can reach 18% in PCE (vs 10.5% reported in Si thin-film based solar cells). Findings from this work provide a practical guideline to design high-efficiency SiNP-textured thin-film solar cells.

Biosensors: A Handy Kit

IME researchers have developed a silicon-based microfluidic system that can be deployed as a portable, point-of-care diagnostic tool for fast and accurate screening of infectious diseases. The system consists of a microfluidic polymerase chain reaction (PCR) module and a silicon nanowire (SiNW) – based detection module. The proposed system can detect 20 fg/µL of H1N1 virus in 10 µL sample - 50% less sample volume than conventional PCR-based lab tests. Unlike existing test kits, the multiplexing feature of the proposed system gives the test differentiating power to tell apart H1N1 virus from other strains of influenza A virus, thereby reducing the likelihood of false negative results. The proposed system is potentially more cost-friendly to produce as complex optical components and alignment are not required.

Microtechnology: An Alignment Assignment

IME researchers have developed a novel two-wafer approach for integrating optical microelectromechanical system (MEMS) devices and photonics devices on a silicon substrate. The difficulty in aligning these two types of devices co-axially limits the conventional one-wafer approach for integration. With the two-wafer approach, two partially processed wafers are bonded first, followed by additional processing steps. In doing so, the respective optical axis of the MEMS and optical devices can align on the same plane with high precision – optical coupling loss controlled to <3 dB from 7 dB. The proposed technique can be applied to hybrid integration of silicon photonics integrated circuits and optical MEMS components with reconfiguration functions on silicon substrate.

Biosensors: Hormonal Attractions

IME researchers have developed a highly sensitive silicon nanowire-based biosensor used for studying the interactions between human estrogen receptor (ER) proteins and estrogen response elements. The ER-functionalized silicon nanowire biosensor can determine estrogen-response elements at low concentration of 10 fM - 10000 times more sensitive than conventional Gel Mobility Assay Method. The highly sensitive biosensor can pick up subtle differences in ER-DNA binding affinities, making it possible to glean new insights to ER-mediated gene expression for breast cancer. IME's new biosensor is expected to be a valuable tool for elucidating the complex metabolic pathways leading to estrogen-dependent breast cancer, paving the way for new cancer treatments.

Photonics: A More Sensitive Device

IME researchers have developed a CMOS-compatible scheme for realising surface plasmon polariton (SPPs) in a waveguide Ge-on-SOI photodetector. The proposed photodetector uses Ge as the light absorbing layer and Al grating structure in the CMOS fabrication process. The SPP augments the interaction between light and the Ge layer, while the grating structure excited SPPs and delays light propagation properties. The resulting photodetector exhibits 3x higher transverse magnetic mode responsivity than that of transverse electric modes - demonstrating that an additional dimension can be used to improve performance in waveguide photodetectors. The photodetector can be applied in wavelength division multiplex networks for high speed data communication.

Microtechnology: Miniature Magnetic Switches

IME researchers have developed a novel passive magnetostatic microelectromechanical (MEMS) switch that is fabricated by micromachining technology. The switch is composed of an electroplated Ni₈₀Fe₂₀ plate that is supported by a pair of torsion bars. The patterning of the Ni₈₀Fe₂₀ plate into long and narrow strips confers sensitivity to the device, while the novel device structure and micromachining technology enable smaller device footprint (4 mm² vs >12 mm² ), better shock resistance (>500 g vs 50 g), and lower fabrication cost - compared to conventional reed switches. The switch also exhibits high sensitivity, low contact resistance and good reliability. The proposed switch has the potential to replace conventional reed switches in portable electronics, such as laptops, cellular phones and hearing aids.

Photonics: Better Optical Fibre Networks

IME researchers have developed a new passive optical network (PON) configuration and a novel silicon photonic transceiver architecture for optical network unit (ONU). The new configuration enables significant reduction of the ONU transceiver size, integration of functions on a silicon chip and requires only one centralized light source. This work demonstrates the feasibility of mass manufacturing monolithic silicon ONU transceivers using low cost CMOS processes, thus speeding up silicon photonics for practical network deployment.

Optics: Mastering Bandwidth

IME researchers have developed a micromachined injection-locked laser (ILL), which provides tunable discrete wavelengths and improved spectral purity for wavelength division multiplexing (WDM) optical access network. The MEMS platform adopted in the proposed ILL permits high compactness, fast tuning speed, pro-batch fabrication and ready integration into circuits. When compared to conventional lasers made with high quality optical components, the proposed MEMS ILL is significantly smaller by 5 million times and is characterized by improved laser performance: narrower line-width - by 42 %; higher side mode suppression ratio - by 30 dB; higher output power - by 32%; faster tuning speed - by 1000 x. With the merits of small size, low power consumption and low fabrication cost, the MEMS ILL would find potential applications in advanced optical communications e.g. all-optical switching, high speed data communications and reconfigurable optical networks. The MEMS ILL is also promising for use in atomic watches to enable highly precise and accurate time keeping.

Microfluidics: A Thousand Captures at a Time

IME researchers have developed a silicon-based device for use in drug discovery. The device has demonstrated simultaneous capture of 12 individual cells - 12x higher throughput than conventional patch clamping. The device could be scaled up to allow 1152 cell-recordings at the same time. With automation, the proposed device has the potential to dramatically shorten drug development cycle for rapid screening of drug candidates.

Silicon Nanowires: Pressure Sensors Get a Boost

IME researchers have reported for the first time interesting piezoresistive behaviours exhibited by nanowires. The study was carried out by embedding the nanowires in a cantilever and measuring their piezoresistance when mechanical stress and a transverse electric field were applied. The electric field dramatically augments the electromechanical response by up to 2 orders of magnitude, generating giant piezoresistance in the nanowires. The demonstration of the capability to electrically control piezoresistance in nanowires holds great promise for a new family of electromechanical sensors with tuneable sensitivity for use in miniaturised medical devices that can be tailored for a wide range of functionalities.

Microfabrication: The Power of Heat

IME researchers have developed a compact energy-harvesting device that generates electricity from a temperature gradient. The proposed device is made with polysilicon and CMOS-compatible processes, making it cost-viable to fabricate in large volumes. With a 5K temperature difference, this device can generate 1.3 µW power output, enough to power a digital wrist watch indefinitely. The proposed device is ideal for wireless wearable health applications and implanted medical devices as they eradicate exorbitant battery replacement costs.

Photonics: Silicon Steps Up

IME researchers have designed and fabricated a high performance wavelength division multiplexing (WDM) receiver with 32 channels using silicon photonics technology. Each channel is capable of operating at a data rate of at least 10 Gbps, giving the WDM receiver an aggregate data rate of 320 Gbps, thereby addressing the data transmission demand in optics communication. The chip area attained from this work is about 100-fold smaller than that of externally-packaged photodetector with traditionally-assembled components. This first demonstration indicates the feasibility and potential of manufacturing low cost, ultra-compact silicon WDM receivers for terabit data communications. Other potential applications for the WDM receiver include photodetectors, as well as optical sensors with multiplexing capabilities, paving the way for inexpensive bandwidth on demand.

Microfluidics: A Step in the Right Direction

IME researchers have designed and fabricated a range of silicon-based microfluidic devices to generate droplets of tunable size and emulsion characteristics. By introducing different step profiles and surface characteristics into the microfluidic devices, the team seeks to understand the complex droplet formation process that plays a defining role in a variety of applications. Insights from this study would form the basis for designing microfluidic devices that could produce different types of droplets precisely and consistently every single time.

Silicon Photonics: A New Twist on Light

IME researchers have developed a highly efficient and compact wideband silicon-waveguide-based polarization rotator to enhance the performance of Si photonic circuits. For high index-contrast waveguides, fabrication error of just a couple of nanometers would result in undesirable birefringence, which is a major roadblock to manufacturing. Small core silicon-waveguide based Si photonics are particularly susceptible to the effects of polarization. The IME-developed rotator allows different launching conditions that would enable new designs of polarization splitter and rotator. The proposed rotator is expected to accelerate the adoption of emerging Si photonics technology into mainstream optoelectronics applications.

Silicon Photonics: Brought Into Line

IME researchers have developed a MEMS platform with integrated functions of ultra fine optical alignment and positional locking. IME’s on-chip alignment platform provides optimum light coupling from laser diode to a small core Si waveguide with performance of <1dB/facet and <+/-1um alignment precision, respectively. The proposed work is expected to replace costly conventional alignment equipment, with potential utilization in hybrid integrated Si photonics, as well as applications that consist of LD-ball lens-Si-waveguide coupling system.

Wireless Networks: Radios Go Wide

IME researchers have developed a low power fully integrated ultra wide bandwidth (UWB) solution to support both communication and localization applications. With the in-built RF transceiver and digital PHY in the UWB system-on-chip (SoC), a smaller device footprint can be attained. The low power consumption, energy efficiency (TX 0.92nJ/b and RX 5.3nJ/b) and maximum spectrum usage are among the most notable features of the proposed UWB SoC system.

A*STAR IME Develops Silicon-based 135 GHz Circuit Technology For Future Generation Wireless Communications

Researchers from A*STAR Institute of Microelectronics (IME) are exploiting high radio frequency to develop future high speed wireless communication products. Using silicon-based materials, the team have successfully realised high speed chips that can wirelessly communicate data at a rate of 10 Gbps on 135 GHz band - more than 100 times faster than present day Wi-Fi[1].

Semiconductor Processing: Stress Management

IME researchers have designed, fabricated and calibrated piezoresistive stress sensors to measure the amount of mechanical stress and distribution caused by the wafer thinning process. This data will be important to guide future 3-D TSV process development to enhance survivability of the ultra-thin wafers during wafer thinning, handling and further processing. To the best of the authors' knowledge, this is the first report of an in-depth stress profile study on ultra-thin wafers.

A*STAR IME Heralds Personalised Therapy For Cancer Patients With Faster And Cheaper Test

Researchers from A*STAR Institute of Microelectronics (IME) Bioelectronics programme are developing a cost-effective and a more rapid  way to help physicians assess the effectiveness of treatments to cancer patients.  IME’s research will allow more frequent tracking of a patient’s response to the prescribed treatment, enabling the physician to better tailor dosages for radiation and/or chemotherapy - treatments that can be plagued with discomfort and serious side effects. The new device measures the level of circulating tumour cells (CTCs) in whole blood and it is expected to speed up the sample-to-answer process by more than 50%.

A New Era In Cardiac Health diagnostics With Silicon-based Integrated System