imec's own October show

Monday 17th October 2011

In a flurry of embargoed publicity, imec, Europe's top semiconductor research laboratory unveiled a 'personalised' IEDM of a low power ECG patch; high quality EUV sensors for nextgen litho; chip-integrated ultra low-power impulse-radio ultra-wideband (IR-UWB); extremely high speed HBTs; and a CMOS poly-SiGe piezo resistive pressure sensor. Nothing as yet on graphene, but a lecture on 2D graphene for nano electronics: from lab to foundry suggests that like III-Vs, graphene will inevitably takes its place in the one-time silicon-only imec portfolio.

The body ECG patch
Imec and Holst Centre's  innovative body patch integrates an ultra-low power electrocardiogram (ECG) chip and a Bluetooth Low Energy (BLE) radio. This fuses power-efficient electronics and standardized communication, opening new perspectives for long-term monitoring the heart in health, wellness and medical applications.  The system integrates components from imec and Holst Centre’s Human++ R&D program and is designed in collaboration with Danish-based DELTA and integrated in DELTA’s ePatch platform.

The ECG patch measures up to 3 lead ECG signals, tissue-contact impedance and includes a 3D-accelerometer for physical activity monitoring. Processed and analysed locally, data, relevant events and information are transmitted through Bluetooth Low Energy.

The patch is capable of monitoring, processing and communication on minimal energy. Computing and transmitting heart rate, the entire system consumes280µA at 2.1V, running continuously for one month on a 200mAh Li-Po battery. Transmitting accelerometer data (at 32Hz) on top of the heart rate, power consumption remains below 1mA in continuous operation, giving about 1 week of autonomy.

At the heart of the patch is an ECG System-On-Chip (SoC), and mixed signal ASIC. Custom designed to provide ECG monitoring and high processing power at an extremely low energy consumption. Next to monitoring 1- to 3-lead ECG, the ECG SoC also monitors the contact impedance, providing real-time information on the electrode contact quality. This can be used to evaluate the quality of the ECG measurement and to filter motion artifacts.

The ECG SoC has been designed to run algorithms for motion artifact reduction (based on adaptive filtering or principal component analysis) and beat-to-beat heart rate computation (based on discrete or continuous wavelet transforms).

It has additional computation power to run application-specific algorithms such as epileptic seizure detection, energy expenditure estimation or arrhythmia monitoring. The built-in 12-bit ADC is capable of adaptive sampling QRS waves at high frequency, and the other waves at a lower frequency – achieving compression ratios of up to 5.

The BLE link adds a standardised plug-and-play communication gateway to mobile devices such as smartphones and tablets. Smartphones and tablets enabled with Bluetooth 4 have been announced for next year, a gateway for your social heart.

EUV sensors for ASML’s next-gen lithography tools
(Left: Wafer with EUV sensor dies, produced on imec’s 200mm CMORE line.)

Imec successfully qualified a chipset consisting of custom high-quality EUV sensor dies. Already in November, ASML will install its state-of-the-art 193nm immersion litho tool, NXT1950i system.

Imec will also be able to further accelerate its world-renowned work on EUV lithography with the installation of the production ready EUV litho system NXE:3300B, the successor of ASML’s NXE:3100 preproduction tool that had been installed at imec in Spring 2011. This includes the suite of ASML’s computational lithography tools and the advanced metrology platform ASML Yieldstar S200.

Imec's 5-year  agreement with ASML that enables imec and its partners in imec’s advanced IC technology scaling program, to stay at the forefront of next generation technologies. The close interaction in imec’s world-leading semiconductor ecosystem, provides ASML - from its future industry clients - crucial feedback on essential specifications to optimize their next-generation lithography tools.

Building on 25 years of experience, and by combining the most advanced lithography tools and skills from imec, ASML, Zeiss and imec’s global semiconductor ecosystem, we now represent the largest litho expertise centre in the world.

"ASML's close partnership with imec has given our joint customers early insights and learning into the capabilities of new chip manufacturing solutions, paving the way for their technology leadership and commercial success. We're pleased to commit to the next level of collaboration as we transition to EUV technology and so enter the next decade of shrink technologies," said Martin van den Brink, ASML's chief products and technology officer.

The CMORE toolbox has a wide variety of device technologies on 200mm (CMOS, Si-photonics, MEMS, image sensors, packaging) as well as design, testing and reliability. Next to these EUV sensors, imec CMORE is developing several other customer chip solutions. They include technology from all imec’s strategic areas as bio-sensing, energy-power management, high-end specialty imaging, and photolitho among others.

Impulse radio ultra-wideband
Chip-integrated ultralow-power impulse-radio ultra-wideband (IR-UWB ) solution for use in the worldwide available 6-10GHz band. The radio delivers high-quality communication for battery-operated mobile and sensing applications. It operates fade-resilient and interference-free.

With its first ultralow-power integrated solution for the 6-10GHz band, imec and Holst Centre now make UWB communication available for battery-operated applications in the area of personal area networks and positioning sensors worldwide. Examples are short-range video streaming or around-the-body audio streaming (e.g. between a headset and a smartphone).

When using the UWB radio for the wireless streaming of audio between for example a smartphone and an earpiece, the battery lifetime of the smartphone will increase by over 3x compared to a conventional Bluetooth-based solution, and the earpiece will have a battery lifetime increase of over 5x. In contrast to the Bluetooth communication, the UWB radio will not suffer from interference from other wireless technologies that operate in the same location and in the same frequency band.

IR-UWB communication is especially suited for short-range (20m) comS and positioning sensors. The large bandwidth improves fade resilience, resulting in communication reliability especially contrasted to narrowband solutions, which tend to lose signals in surroundings with reflective surfaces and multi-path propagation.

Spreading information over a wide bandwidth decreases the power spectral density, reducing other system interference and lowering the interception probability. IR-UWB suits positioning sensors; the reflection of the wide-band signal allows for centimeter-ranging positioning accuracy. 

Imec and Holst Centre’s solution is a transmitter delivering 13dBm peak power, average power consumtion 3.3mW. The receiver front-end shows -88dBm sensitivity at 1Mbps. A digital synchronisation algorithm enables real-time duty cycling,giving mean power consumption of 3mW. A DCO with 100ppm frequency accuracy and a baseband frequency tracking algorithm ensure coherent reception. And a 75dB link budget with a data rate of 1Mbps is achieved.

Multi-mode digital TV receiver & reconfigurable processor
Imec has developed a reconfigurable receiver for highly diversified digital video broadcasting standards (DVB-T, ISDB-T and ATSC). The receiver is realized using algorithm-architecture co-optimisation of imec’s reconfigurable processor ADRES. The solution combines better area efficiency than reference dedicated ASICs with state-of-the-art performance. The optimisations were realized in the context of Panasonic's partnership in imec's green radio research program.

Digital broadcasting products can be hampered by the many different regional standards that have been adopted world-wide. Due to the ultimate programmability, software-defined radio (SDR) solutions are becoming more and more attractive. Reconfigurable processor-based implementations allow saving on design-cost and time-to-market. However, SDR baseband solutions are traditionally reported to come with an area penalty when compared to ASIC counterparts. As area efficiency is one of the most important factors to determin final cost of commercial chipsets, competitive area efficiency is crucial for SDR baseband solutions.

The instantiation of imec’s Architecture for Dynamically Reconfigurable Embedded Systems (ADRES) processor was optimised by combining innovative algorithms (highly parallel implementation, software optimisations) with architecture improvements (optimized intrinsics, exploration towards leaner instance), yielding a drastically smaller silicon area than ASIC counterparts of considered broadcasting standards.

On top of its area efficiency, the baseband processor proves to be highly flexible, supporting not only Digital TV standards (ATSC, ISDB-T, DVB-T) but other wireless communication standards: both an IEEE 802.11n inner receiver and a cat-4 LTE receiver can run real time on the same architecture.

Antoine Dejonghe, manager reconfigurable radio at imec: “We are delighted with these results, realized through our collaboration with Panasonic, that clearly prove the relevance and advantage of SDR baseband as a cost-efficient and flexible solution for consumer electronics

New avenues for imaging and wireless communications
Imec realized a fT/fMAX 245GHz/450GHz SiGe:C heterojunction bipolar transistor (HBT) device, a key enabler for future high-volume millimeter-wave low-power circuits to be used in automotive radar applications. These HBT devices also pave the way to silicon-based millimeter wave circuits penetrating the so-called THz gap, enabling enhanced imaging systems for security, medical and scientific apps.

The extremely high-speed devices have a fully self-aligned architecture by self-alignment of the emitter, base and collector region, and implement an optimized collector doping profile.

Compared to III-V HBT devices, SiGe:C HBTs combine high-density and low-cost integration, making them suitable for consumer applications. Such high-speed devices can open new application areas, work at very high frequencies with lower power dissipation, or applications which require a reduced impact of process, voltage and temperature variations at lower frequencies for circuit reliability.

To achieve the ultra high-speed requirements, state-of-the-art SiGe:C HBTs need further up-scaling of the device performance. Thin sub-collector doping profiles are generally believed to be mandatory for this up-scaling. Usually, the collector dopants are introduced in the beginning of the processing and thus exposed to the complete thermal budget of the process flow.

This complicates the accurate positioning of the buried collector. By in-situ arsenic doping during the simultaneous growth of the sub-collector pedestal and the SiGe:C base, imec introduced both a thin, well controlled, lowly doped collector region close to the base and a sharp transition to the highly doped collector without further complicating the process.

This resulted in a considerable increase of the overall HBT device performance: Peak fMAX values above 450GHz are obtained on devices with a high early voltage, a BVCEO of 1.7V and a sharp transition from the saturation to the active region in the IC-VCE output curve. Despite the aggressive scaling of the sub-collector doping profile, the collector-base capacitance values did not increase much. Moreover, the current gain is well defined, with an average around 400 and the emitter-base tunnel current, visible at low VBE values, is limited as well.

The results were realized within the framework of the European joint research project DOTFIVE which aims at developing SiGe:C HBT devices that operate at 500 GHz at room temperature.lications.

CMOS poly-SiGe MEMS piezoresistive pressure sensor
Imec has achieved an integrated poly-SiGe-based piezoresistive pressure sensor directly fabricated above 0.13µm copper (Cu) -backend CMOS technology,  the first integrated poly-SiGe pressure sensor directly fabricated above its readout circuit and also the first time that a poly-SiGe MEMS device is processed on top of Cu-backend CMOS.

Cross-section SEM picture of the integrated sensor. Bottom, the two Cu metal lines of the CMOS circuit. Above, MEMS layers (poly-SiGe membrane, piezoresistors, oxide sealing layer, metal interconnects) are visible.

Polycrystalline SiGe has emerged as a promising MEMS structural material since it provides the desired mechanical properties at lower temperatures compared to poly-Si, allowing the post-processing on top of CMOS. The MEMS-last approach is the most interesting  for CMOS-MEMS monolithic integration with smaller die areas, enabling integrating the MEMS without introducing any changes in standard foundry CMOS processes.

Compared to alternative technologies, as using the CMOS top interconnect layers to fabricate the MEMS device, poly-SiGe offers a more generic, flexible technology for above CMOS integration, thanks to the fact  MEMS fabrication can be completely decoupled from the CMOS fabrication. 
Imec has already proved the poly-SiGe poteontial for MEMS above-aluminum-backend CMOS integration.

However, aggressive interconnect scaling has led to the replacement of the traditional aluminum metallization by copper metallization, due to its lower resistivity and improved reliability. Results now broaden applications of poly-SiGe to MEMS integration with the advanced CMOS technology nodes.

Our integrated sensor (imec fully fabricated) includes a surface-micromachined piezoresistive pressure sensor, a poly-SiGe membrane, four poly-SiGe piezoresistors, an instrumentation amplifier fabricated using 0.13 mm standard CMOS with Cu-inter connects (2metal layers), oxide dielectric and tungsten-filled vias.

To enable CMOS integration, the maximum processing temperature of the complete sensor, including the poly-SiGe piezoresistors, is kept below 455ºC. An appropriate passivation layer is included to protect the electronic circuit from aggressive etch/deposition steps needed to fabricate MEMS devices.

The CMOS circuit showed no significant deterioration after the MEMS processing. Despite low processing temperature, the poly-SiGe piezoresistive sensor alone (250x250µm2 membrane) shows a sensitivity of around 2.5 mV/V/bar. The integrated sensor (same sensor + Cu-based CMOS amplifier underneath) showed a sensitivity of about 158 mV/V/bar, ~64 times higher than the stand-alone sensor.

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