Category Archives: Flexible Displays

The flexible and printed electronics community reports encouraging progress in the materials and process ecosystem needed for commercial production — and an increasingly realistic focus on applications that best capitalize on the technology’s strengths. Best near-term prospects now look to be sturdy light-weight displays, smart sensor systems, and flexible and large area biomedical sensors and imagers.

Improving technology for everything from barrier films to roll-to-roll in-line testing may mean printed or flexible electronics will start to see some more significant commercial applications in the next few years. Judging from the reported status of sturdy lightweight displays, smart-enough sensor tags, and medical sensors and imagers at FlexTech Alliance’s annual conference last week in Phoenix, suppliers are increasingly targeting higher-value applications that can’t easily be made in other ways.

Light-weight, Rugged Displays

“This industry is starting to become reality,” asserted Plastic Logic CEO Indro Mukerjee, “We’ve moved from a science project to an industrial process, and have created a value chain with partners to make the business possible.”  He has moved the flexible display company away from marketing its own e-reader to supplying its electrophoretic display on flexible backplane module to a wide range of new users, now working with partners making outdoor signs, watches, automobiles, smart cards, and industrial indicators. He’s also promoting the company’s flexible TFT backplane for use in other markets, and aggressively pursuing LCD makers to transfer the production process for scaling. “The technology frontier business is not for the faint hearted,” he noted. “We’re going for it at Plastic Logic.” 

Growing into Major Markets: Will Take Time

Flexible and transparent displays will be the next big thing in displays, and will start to see real growth after 2015, to account for 19 percent of the display market by 2020, projected Sweta Dash, IHS senior director, Display Research and Strategy. She noted that Samsung and LG planned to start production, to some degree at least, of displays on unbreakable substrates this year for smart phones and tablets, targeting lighter weight and better durability.  IDTechEx senior technology analyst Harry Zervos figured only 1 percent of the large OLED display market would be either printed or flexible by 2018, but 12-14 percent would be so within ten years.  Though the same technologies will help the cost and performance of OLED lighting and organic PV, these applications, however, still seem a little further from significant commercial products. In five years, IDTechEx projects OLED lighting to reach a ~$120 million market, with flexible batteries, logic and memory, and solar all in the $50-$60 million range. 

Most of these flexible products still need better flexible barrier films to extend their useful lifetimes, and new transparent conductors to replace brittle ITO. Barrier films appear to remain problematic, but progressing. The sector has big hopes for lower cost ALD films, and Beneq Oy reported progress on cross flow technology for batch processing, with capacity to coat 35 2G-sized sheets with 50nm of Al2O3 in three minutes.  It has also scaled up a roll-to-roll (R2R) system, by separating the precursor gases by space instead of time, for coating several meters per minute. Best results for its 25nm Al2O3 barrier are 10-4g/m2/day. Vitriflex CEO and founder Ravi Prasad said its mixed-oxide thin-film stack with a novel top seal made by low-cost R2R sputtering on polymer film had been tested at independent labs at better than the industry target 10-5 g/m2/d. Sean Garner, Corning Inc. research associate, reported good results from initial runs of common material stacks on its rolls of 50-100nm flexible glass at pilot and research R2R printed electronics facilities. Wire grids and possibly silver nano wires appear to look like the best options for ITO replacement. 

Integrating Components into Flexible Systems

Beyond the display market, the major enabler for other printed applications is the ability to efficiently integrate various separate components into useful systems, and here Thin Film Electronics and its partners now target smart sensor tags, roll-to-roll printed in large volumes. The key market for printed electronics will not be large area devices that need very good yields, but instead simple devices in very large numbers, argued Thin Film CEO Davor Sutija. 

The company and its partners aim at  the ~$1.4 billion time and temperature sensor market, with tags potentially combining printed memory from Thin Film, organic logic from PARC, a printed thermistor from PST Sensors, and an electrochromic display from Acreo. Thin Film is also partnering with major packaging supplier Bemis to develop and market such smart packaging applications.  A more developed commercial product version of the current proof-of-concept demonstrator is targeted for 2014.

Shippers currently use simple color-changing tags to indicate if perishable shipments have gotten too hot or too cold in transit, but the information is limited and the color doesn’t last long. Simple printed systems of sensors plus memory and some 500-1,000 transistors of logic could be R2R printed at high volumes to record and display more usefully precise information than current alarm tags or data loggers, at lower cost than silicon. Similar simple tags for smart objects to store small amounts of actionable information could also be used for things like dynamic price displays, pharmaceuticals or logistics. Sutija optimistically projects smart sensor tags will be a 60 million unit market by 2014, and reach some 2 billion units by 2016, worth some $300 million — suggesting a ~$0.15 per tag price at those volumes. 

The company’s well established memory technology uses a ferroelectric polymer sandwiched between top and bottom electrodes that changes and maintains its state of capacitance when pulsed.  It has also developed much of the manufacturing infrastructure as well, including a  high-speed R2R step-and-go electrical test system based on a print web handling tool, and a hard scratch UV varnish coating to protect the memory, with a key flexible layer underneath to minimize the mechanical stress. 

Another approach to integrating components into flexible systems is to attach silicon chips to the flexible substrate, which could be easier if the chips were flexible. American Semiconductor and TowerJazz are currently qualifying a commercial foundry process for flexible silicon-on polymer CMOS, which will offer multi-project wafer runs to ease development. American Semiconductor CEO Doug Hackler said characterization of first wafers shows no shift in transistor performance of the flexible wafers, and that in fact removing the handle layer of the SOI wafer appeared to reduce parasitic capacitance and improve performance for RF devices.  It’s currently working on systems using the flexible chips in a smart conformable antenna with the Air Force Research Lab, and a flexible smart card with security card supplier ASI.

Flexible Medical Devices with Hybrid Approaches

Research efforts are targeting medical applications that require flexibility to comfortably wear on the body or wrap around it for measurement, such as MRI coils, or better collect data from inside it, via catheters or endoscopes or pills but that often need to be integrated with silicon-quality processing or communications.  FlexTech announced it was awarded a $5 million grant for a Nano-Bio Manufacturing Consortium, sponsored by the U.S. Air Force Research Lab, to bring together the diversity of players needed for cooperative R&D to develop a common manufacturing platform for microfluidics on flexible substrates for wearable sensors for monitoring human response, integrating wireless communication with hybrid electronics manufacturing.

MC10 is launching its first product, an impact monitoring device developed and marketed with Reebok, for inside a sports helmet to indicate when the wearer has had a high impact to the head, reported R&D VP Kevin Dowling. The company is also testing attaching its flexible sensors to catheter balloons, for interventional devices than can be inflated once inside the body. For example, these could be used to measure atrial fibrillation, to determine if an ablation treatment worked, or to send back a fuller map of electrical data from the beating heart than possible from one or two electrodes.  MC10’s approach is not to print the electronics, but to embed thinned silicon die with flexible wire connections in rugged polymer to make its flexible systems.  The chips are under-etched, released, and then transferred to the mold substrate, using transfer tools for the thinned die the company developed in house.

MC10, and a host of other researchers, with both hybrid systems and fully printed ones, are also working on measuring a wide range of vital signs with flexible skin patches or other units adhered to the skin, for condition monitoring, often sending the data to a smart phone for analysis. Ana Arias of the University of California at Berkeley showed good results with a flexible finger sensor to measure blood oxygenation with red and IR sources and detectors, and also printed MRI coils on flexible substrates that could wrap conformably around different sized people and body parts to get better images more quickly.  GE Global Research’s work on medical monitoring for the U.S. Army aims to print the sensors and conditioning electronics, but then use silicon for the high-speed communications. Electronic systems engineer and PI Jeff Ashe noted that a major challenge was how to efficiently assemble the silicon die with the printed the components, as assembly could account for almost half the total cost of the system. The solution: printing a magnetic layer on the chips and then shaking them over film with a patterned magnetic template underneath, so the chips quickly stick to the desired magnetic sites.

By far the most commercially advanced results were from Body Media, which is extending its sensor patch and armband, and sensor fusion and monitoring software, to more applications. Though the company puts its sensors in a flexible patch for trial purposes, and some need a flexible wire in flexible armbands, the core of the system is more conventional MEMS and other rigid sensors in a watch-like unit to measure activity, heart rate, galvanic skin response, and even ECG from the upper arm. The company has gotten good traction so far for weight loss, thanks in part to enthusiastic publicity from users on “The Biggest Loser” TV show, but CEO Ivo Stivoric sees opportunity in combining the rich activity and stress information from the system with other outside information on, say, glucose levels or cardiac data to aid in better managing other medical conditions. The company is looking for partners with the domain expertise to apply the sensor and software solution to other applications.  

Solution or Vapor Processing? On Flexible or Rigid Substrates? Printed Features or Attached Silicon Die?

All these systems have to navigate a complex system of tradeoffs between potentially disruptive and low-cost solution processing, flexible substrates, and organic materials— and the better performance possible with more established vacuum processes, rigid substrates, and conventional silicon devices.  IDTechEx’s Zervos predicted as much as a $20 billion market for “predominantly printed” electronics in a decade, but only a little over half of that would actually be made on flexible substrates, as developments in laser lift off, other peel-off technologies, and even thinned silicon wafers may allow more easily controlled processing on rigid substrates for making flexible products. 

Though OLED displays are now all vacuum coated on rigid substrates, producers are moving to solution printing the first, hole-side layer that is the thickest and uses expensive materials to save time and cost, and will likely gradually move to eventually printing more or even possibly all of the layers on rigid substrates, but area volumes will never be high enough for roll-to-roll printing on flexible substrate to make sense, argued NOVALED CSO Jan Blochwitz-Nimoth.  For large area OLED displays for TVs, the fine metal masking now used for depositing and patterning the red, green and blue OLED layers will be hard to scale up to 8G-sized substrates, so inkjet or nozzle printing could be the alternative. But that’s a big change to introduce on such a large scale, so producers are also looking at vapor processes like small mask scanning, laser induced thermal imaging, and using white OLED with a color filter instead. OLED lighting, on the other hand, could go to either R2R vacuum coating, or to adding some printed layers on rigid substrates to reduce costs in high-volume production. Blochwitz-Nimoth also noted that improved high deposition rates at low temperature from Aixtron’s new source could mean OLED lighting would not need solution processing after all.  OPV, in contrast, needs the high area volumes that only make sense to do with R2R, either all vacuum as NOVALED is starting pilot testing, or with printed hole-side layers. 

Supposedly low-cost printed electronics may often not actually be the lowest cost solution, argued David Miller from Arizona State University. He estimated that with appropriate performance, printing on flex in current low-volume R&D/pilot-type lines actually costs some $29/cm2, compared to ~$7/cm2 for CMOS and ~$0.05/cm2 for displays, though the comparison between research-level and production-level process costs is of course "apples to oranges." Still, for small die, it could make most sense to just attach a rigid or thinned silicon device to the flexible system. At moderate and high area volumes, however, printed TFTs should become significantly cheaper than silicon, so printed technologies may likely have the advantage for large area displays, and large area sensing arrays for things like optical imagers, x-rays and radiation detectors.  High-intensity computation and high-speed communication could then be added by conventional CMOS chips on the periphery.

SEMICON West has become a forum for the latest solutions and technologies for flexible electronics manufacturing of interest to the semiconductor/display world.  Now in its fifth year, the Printed and Plastic Electronics forum, organized by FlexTech, brings together manufacturers, developers, equipment and materials suppliers, and other solution providers.  FlexTech will also offer a workshop on transparent conductor technology developments.

Exhibiting Opportunities Available 

Companies are invited to exhibit at SEMICON West. If you have plastic and printed electronics technologies or solutions, exhibit in the Extreme Electronics zone. Close proximity to the presentation stage plus focused attendee marketing ensures high visibility with visitors focused on and interested in plastic electronics technologies. Great opportunities are still available — learn more about exhibiting at SEMICON West and Extreme Electronics! 

SEMICON West 2013 visitor registration opens March 18.

Corning, Apple’s glass supplier, announced yesterday that it will probably take at least three years before companies start making flexible displays using its new Willow flexible glass material.

Speaking with Bloomberg, Corning president James Clappin says that products with flexible displays are likely still three years out, adding that it’s now busy making "a lot of effort" to teach what it describes as "very big name" companies how to fully use the product. The glass has been rolled out as companies, such as Google, are considering launching wearable computers.

Clappin told reporters that companies have yet to come up with products that take advantage of Willow glass. The glass can be rolled up like a newspaper, allowing companies to make curved or flexible displays. Clappin believes people are not accustomed to glass you roll up.

Willow glass may be used in some simple products this year, said Clappin. Examples of these products could be thin films behind some touch panels or a flexible barrier for solar panels.

Corning said they have sent out samples of the flexible glass to makers of phones, tablets and TVs in June. Corning CFO, James Flaws, at the time said that the company hoped it would be available in consumer products this year.

advanced electronics packagingEngineered Material Systems, a global supplier of electronic materials for circuit assembly applications, debuts its DB-1568-1 low-temperature cure die attach adhesive for attaching semiconductor die in temperature-sensitive devices. Applications include smart cards, camera modules, flex circuits and more.

The DB-1568-1 is more than 90 percent cured after 30 minutes at 80°C, but has a dispensing work life greater than 48 hours (measured as a 25 percent increase in viscosity), while maintaining optimized rheology for stencil printing and excellent damp heat resistance and conductivity stability. DB-1568-1 features extreme flexibility that is ideal for flexible applications with high peel strength to withstand the stresses induced in flexible electronics and display applications. Also, this material can be fast cured at elevated temperatures (1 minute @ 180°C).

DB-1568-1 is the latest addition to Engineered Material Systems’ extensive line of electronic materials for semiconductor, circuit assembly, photovoltaic, printer head, camera module, disk drive and photonic applications.

FlexTech Alliance, a developer of the flexible and printed electronics industry supply chain, announced today that Dr. Keith Rollins has been elected chairman of the Governing Board.  Dr. Rollins has more than 30 years of experience in the advanced materials and specialty chemical industries, and currently serves as Chief Innovation Officer at DuPont Teijin Films US Ltd.  He will serve a two year term, succeeding Dr. John Batey, formerly of Qualcomm MEMS Technologies, Inc., who was the consortium’s chairman since 2011.  

As FlexTech Alliance chairman, Rollins will lead the governing board and all FlexTech Alliance stakeholders to further the organization’s development, continue to build membership, and increase its value through the provision of quality business and technical services.  The chairman’s role is to guide the board as it oversees the consortium’s decisions on policy, program content, and disposition of funds available for sponsoring technology-related research and development projects. 

“We are grateful for John’s Batey’s leadership over the past two years and now warmly welcome Keith Rollins as our new chairman,” said FlexTech Alliance President Michael Ciesinski. “Keith has a tremendous background in emerging technology and in assessing new business opportunities.  Previously, he led the U.K.’s Plastic Electronics Strategy Group, which produced an outstanding report on the opportunities presented by this industry.  With an impressive technical background and an extensive set of business contacts, Keith is well-positioned to strengthen FlexTech’s worldwide outreach.”

Over the last few years, Dr. Rollins has focused on technology development, strategic planning and business development in the displays and flexible electronics industries. Currently, his focus is on the development and widespread use of the DuPont Teijin Films range of polyester PET and PEN materials in flexible displays and electronics applications. Dr. Rollins received his Bachelor of Technology degree with honors in Applied Chemistry in 1979 and his Doctorate in Catalysis Chemistry in 1985 from Brunel University in London, UK.

“Successful deployment of flexible, printed electronics requires a multi-disciplinary approach, spanning materials development to electronics fabrication to conventional printing techniques,” explained Dr. Rollins. “FlexTech Alliance plays a pivotal role in bringing these diverse industries together.  I am honored to represent the industry and look forward to expanding FlexTech’s programs and services.”

Stretched-out clothing might not be a great practice for laundry day, but in the case of microprocessor manufacture, stretching out the atomic structure of the silicon in the critical components of a device can be a good way to increase a processor’s performance.

Creating "stretched" semiconductors with larger spaces between silicon atoms, commonly referred to as "strained silicon," allows electrons to move more easily through the material. Historically, the semiconductor industry has used strained silicon to squeeze a bit more efficiency and performance out of the conventional microprocessors that power the desktop and laptop computers we use each day.

However, manufacturers’ inability to introduce strained silicon into flexible electronics has limited their theoretical speed and power to, at most, approximately 15GHz. Thanks to a new production process being pioneered by University of Wisconsin-Madison engineers, that cap could be lifted.

Professor develops flexible electronics"This new design is still pretty conservative," says Zhenqiang (Jack) Ma, a professor of electrical and computer engineering. "If we were more aggressive, it could get up to 30 or 40GHz, easily."

Ma and his collaborators reported their new process in Nature Scientific Reports on Feb. 18, 2013.

Ma endeavored to address a paradox for straining and doping silicon electronics built on a flexible substrate. The straining process is similar to stretching out a t-shirt: the researchers pull a layer of silicon over a layer of atomically larger silicon germanium alloy, which stretches out the silicon and forces spaces between atoms to widen. This allows electrons to flow between atoms more freely, moving through the material with ease-just as a t-shirt stretched over a dummy will have more space between threads, allowing it to breathe.

The problem comes during the doping process. This necessary step in semiconductor manufacturing introduces impurities that provide electrons that ultimately flow through the circuit. Doping a stand-alone sheet of strained silicon is like ironing a decal onto a stretched t-shirt. Just as an ironed-on design cracks when the t-shirt is stretched and unstretched, the act of doping distorts the flexible free-standing silicon sheet, limiting its stability and usefulness as a material for integrated circuits.

Ma believes that using the material to design next-generation flexible circuits will yield flexible electronics that offer much higher clock speeds at a fraction of the energy cost.

"We needed to dope this material in a way that the lattice structure within would not be distorted, allowing for silicon that is both strained and doped," says Ma.

The solution is akin to dying a pattern into the fabric of a shirt, rather than ironing it on after the fact. Ma and his UW-Madison collaborators — Max Lagally, the Erwin W. Mueller Professor and Bascom Professor of Surface Science and Materials Science and Engineering; and Paul Voyles, an associate professor of materials science and engineering — have developed a process through which they dope a layer of silicon, then grow a layer of silicon germanium on top of the silicon, then grow a final layer of silicon over that. Now, the doping pattern stretches along with the silicon.

"The structure is maintained, and the doping is still there," says Ma.

The researchers call the new structure a "constrained sharing structure." Ma believes that using the material to design next-generation flexible circuits will yield flexible electronics that offer much higher clock speeds at a fraction of the energy cost.

The next step will be to realize processors, radio frequency amplifiers, and other components that would benefit from being built on flexible materials, but previously have required more advanced processors to be feasible. "We can continue to increase the speed and refine the use of the chips in a wide array of components," says Ma. "At this point, the only limit is the lithography equipment used to make the high-speed devices."

Imagers

Since 2010, there has been growth beyond expectations in the adoption of mobile devices, such as smart phones and tablets, which has called for larger volumes of CMOS image sensor chips to be produced. The resolution and miniaturization races are ongoing, and performance metrics are also becoming more stringent. In addition to the conventional pixel shrinkage, a “more than Moore” trend is increasingly evident. Resolutions of over 20 Mpixels are commercially available for mobile devices employing enhanced small-size pixels. Thanks to the innovative readout and ADC architectures embedded at the column and chip levels, data rates approaching 50Gb/s and a noise floor below single electron have been demonstrated. In addition to the conventional applications, ultra-low-power vision sensors, 3D, high-speed, and multispectral imaging are the front-running emerging technologies.

Back-side Illumination (BSI) is now the mainstream technology for high-volume, high-performance mobile applications, 1.12μm BSI pixels are available, and the industry is potentially moving towards 0.9μm pixel pitch and below. Additional innovative technologies outside of the traditional scaling include advanced 3D stacking of a specialized image sensor layer on top of deep-submicron digital CMOS (65nm 1P7M) using through silicon vias (TSVs) and micro-bumps. The importance of digital-signal-processing technology in cameras continues to grow in order to mitigate sensor imperfections and noise, and to compensate for optical limitations. The level of sensor computation is increasing to thousands of operations-per pixel, requiring high-performance and low-power digital-signal-processing solutions. In parallel with these efforts is a trend throughout the image sensor industry toward higher levels of integration to reduce system costs.

Ultra-low-power vision sensors are being reported in which more programmability and computation is performed at the pixel level in order to extract scene information such as object features and motion.

Lightfield/plenoptic commercial cameras, which have been available since 2010, are now gaining popularity and are being marketed for 3D imaging and/or all-in-focus 2D imaging. On-chip stereoscopic vision has been demonstrated through digital micro lenses (DML), paving the way to next-generation passive 3D imaging for mobile and entertainment applications, e.g. through gesture control user interfaces.

Significant R&D effort is being spent on active 3D imaging time-of-flight (TOF) applications to support requirements from autonomous driving, gaming, and industrial applications, addressing open challenges like background light immunity, higher spatial resolution, and longer distance range. Deep-submicron CMOS single-photon avalanche diodes (SPADs) have been developed by several groups using different technology nodes. They are now capable of meeting the requirements for high resolution, high timing accuracy by employing highly parallel time-to-digital-converters (TDCs) and small pixel pitch with better fill factor.

Ultra-high-speed image sensors for scientific imaging applications with up to 20Mfps acquisition speed have been demonstrated.

Multispectral imaging is gaining a lot of interest from the image sensor community: several research groups have demonstrated fully CMOS room-temperature THz image sensors, and a hybrid sensor capable of simultaneous visible, IR, and THz detection has been reported.

The share of CCDs continues to shrink in machine vision, compact DSC and security applications. Only for high-end digital cameras for astronomy and medical imaging do CCDs still maintain a significant market share.

Sensors & MEMS

A 4×4 array of sensing cells, developed by Dr. Peng Peng of Seagate Technology, from Flexible Microtactile Sensor for Normal and Shear Elasticity (IEEE Transactions on Industrial Electronics)

MEMS inertial sensors are finding widespread use in consumer applications to provide enhanced user interfaces, localization, and image stabilization. Accelerometers and gyroscopes are being combined with 3D magnetic-field sensors to form nine-degree-of-freedom devices, and pressure sensors will eventually add a 10th degree. The power consumption of such devices is becoming sufficiently low for the sensor to be on all the time, enhancing indoor navigation. There have been further advances in heterogeneous integration of MEMS with interface circuits in supporting increased performance, larger sensor arrays, reduced noise sensitivity, reduced size, and lower costs.

To address the stringent requirements of automotive, industrial, mobile, and scientific application, MEMS inertial sensors, pressure sensors and microphones are becoming more robust against electromagnetic interference (EMI), packaging parasitics, process voltage temperature (PVT) variations, humidity, and vibration.

Sensor interfaces achieve increasingly high resolution and dynamic range while maintaining or improving power or energy efficiency. This is achieved through techniques such as zooming, non-uniform quantization, and compensation for baseline values.

New calibration approaches, such as voltage calibration, are being adopted for BJT-based temperature sensors to reduce cost. In addition to thermal management applications (prevention of overheating in microprocessors and SoCs), temperature sensors are also increasingly co-integrated with other sensors (e.g. humidity, pressure, and current sensors) and MEMS resonators for cross-sensitivity compensation. Alternative temperature-sensing concepts find their way into applications with specific requirements not easily addressed by BJTs: thermal diffusivity-based sensing for high-temperature applications; thermistor-based and Q-based concepts for in-situ temperature sensing of MEMS devices and for ultra-low voltage operation.

MEMS oscillators continue to improve; phase noise is now low enough for demanding RF applications, 12kHz-to-20MHz integrated jitter is now below 0.5ps, and frequency accuracy is now better than 0.5ppm. Consumer applications are adopting new low-power and low-cost oscillators.

Biomedical

There have been continuous achievements in the area of ICs for neural and biopotential interfacing technologies. Spatial resolution of neural monitoring devices is being reduced utilizing the benefits of CMOS technology. IC providers are increasing their component offerings towards miniaturization of portable medical devices.

Telemedicine and remote-monitoring applications are expanding with support from IC manufacturing companies. The applications of such systems are not limited to services targeted for elderly or chronically ill patients; for example there are several technologies developed to enhance the way clinical trials are conducted by monitoring patient adherence and by improving data collection. Low power WiFi, and Bluetooth-low-energy is emerging as a standard wireless connection between portable communication services and wearable technology.

Smart biomolecular sensing is another major trend that marries solid-state and biochemical worlds together with the ultimate goal of enabling a more predictive and preventative medicine. With the help of the accuracy and parallelism enabled by CMOS technology, time, cost, and error rate of DNA sequencing may be significantly improved. Direct electronic readout may relax the need for complex biochemical assays. Similar trends are becoming increasingly evident in the space of proteomics and sample preparation.

Even for medical imaging, there is a trend from hospital imaging toward point-of-care and portable devices. A key example is in the space of portable high-resolution ultrasounds in which larger scientific imaging setups are being integrated onto the sensor by process technology (e.g. integrated spectral filters, CMUT). Another example is in the space of molecular imaging. The advent of silicon photomultipliers (SiPM) providing a solid-state alternative to PMTs enable the realization of PET scanners compatible with MRI, opening the way to new frontiers in the field of cancer diagnostics. More recently, SiPMs realized within deep-submicron CMOS technologies have allowed the integration at pixel- and chip-level of extra features, e.g. multiple timestamp extraction, allowing in perspective a dramatic reduction of the system cost.

Displays

The desire to put much higher-resolution and higher-definition displays into mobile applications is one of the display technology trends, and it is now opening a Full HD smartphone era.  440ppi high-definition displays are expected, even for 5-inch display sizes. Low-temperature polysilicon (LTPS) technology seems to have more merits over a-Si TFT technology. But a-Si TFT and oxide TFT technologies supported by compensating driver systems are being prepared to compete with it. Very-large-size LCD TVs over 84 inches, and UD (3840×2160) resolution are now the leading entertainment systems. 55-inch AMOLED TVs with Full HD resolution are also opening new opportunities in consumer applications.

As touch-screen displays for mobile devices become increasingly thin, capacitive touch sensors move closer to the display. The resulting in-cell touch displays come with reduced signal levels due to increased parasitics, and increased interference from the display and switched-mode chargers. Noise immunity is improved by adopting noise filtering and new signal modulation approaches.

This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid-State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.

large area flexible displaysTechnology directions in the field of large-area and low-temperature electronics focuses on lowering the cost-per-unit-area, instead of increasing the number of functions-per-unit-area that is accomplished in crystalline Si technology according to the well-known Moore’s law.

A clear breakthrough in research for large area electronics in the last decade has been the development of thin-filmtransistor, or TFT processes with an extremely low temperature budget of (<150°C) enabling manufacturing of flexible and inexpensive substrates like plastic films and paper.

The materials used for these developments have for a long time been carbon-based organic molecules like pentacene with properties of p-type semiconductors. More recently, air-stable organic n-type semiconductors and amorphous metal oxides, which are also n-type semiconductors, have emerged. The most popular metal oxide semiconductor is amorphous Indium Gallium Zinc Oxide, or IGZO, but variants exist, such as Zinc Oxide, Zinc Tin Oxide, and so on. The mobility of n- and p-type organic semiconductors has reached values exceeding 10 cm2Vs, which is already at par or exceeding the performance of amorphous silicon. Amorphous metal oxide transistors have typical charge carrier mobility of 10 to 20 cm2/Vs. Operational stability of all semiconductor materials has greatly improved, and should be sufficient to enable commercial applications, especially in combination with large-area compatible barrier layers to seal the transistor stack.

In the state-of-the-art p-type only, n-type only and complementary technologies are available. For the latter, all-organic implementations have been shown, but also hybrid solutions, featuring the integration of p-type organic with n-type oxide TFTs. Most TFTs are still manufactured with technologies from display-lines, using subtractive methods based on lithography. However, there is a clear emphasis on the development of technologies that could provide higher production throughput, based on different technologies borrowed from the graphic printing world like screen and inkjet printing. The feature sizes and spread of characteristics of printed TFT technologies are still larger than those made by lithography, but there is clear progress in the field.

The prime application for these TFT families are backplanes for active-matrix displays, including in particular flexible displays. Organic TFTs are well-suited for electronic paper-type displays, whereas oxide TFTs are targeting OLED displays. Furthermore, these thin-film transistors on foil are well-suited for integration with temperature or chemical sensors, pressure-sensitive foils, photodiode arrays, antennas, sheets capable of distributing RF power to appliances, energy scavenging devices, and so on, which will lead to hybrid integrated systems on foil. Early demonstrations include smart labels, smart shop shelves, smart medical patches, etc. They are enabled by a continuous progress in the complexity of analog TFT circuits targeting the interface with sensors and actuators, to modulate, amplify and convert analog signals as well as progress in digital TFT circuits and non-volatile memory to process and store information.

In line with this trend, ISSCC 2013 features three papers representing the latest state-of-the-art of organic thin-film transistor circuits. A front-end amplifier array for EMG measurement is demonstrated for the first time with organic electronics in paper 6.4. Transistor mismatch and power consumption of the amplifier are reduced by 92% and 56%, respectively, by selecting and connecting the transistors trough a post-inkjet printing. Papers 6.5 and 6.6 present advances in analog-to-digital converters for sensing applications. Papers 6.5 demonstrates the first ADC that integrates on the same chips resistors and printed n and p-type transistors. The ADC achieves an SNDR of 19.6dB, SNR of 25.7dB and BW of 2Hz. In Papers 6.6, an ADC made only with p-type transistors is presented that has the highest linearity without calibration and that is 14 times smaller than previous works using the same technology.

This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid-State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.

A new report from IHS Displaybank examined a total of 483 patents on roll-to-roll processing technologies, focusing on 32 that were flexible, OLED-related. 43 flexible OLED-related roll-to-roll application technologies and 23 roll-to-roll patents by SiPix were also selected for an analysis. 

A flexible display is considered as the next-generation display that is bendable and rollable without damage, by using a paper-thin and flexible substrate. The flexible display market is projected to lead the market growth by creating a new display market as well as by replacing the current display market. In addition, when producing flexible displays, if a large-area and low-cost technology based on the roll -to-roll process is realized, new demands with such as indoor/outdoor advertising and various decorative purposes are expected to be created.

The roll-to-roll process is a foundation to mass produce flexible electronics applications at low cost. It is a greatly demanded technology in the related-product manufacturing industry. The technology at the present level allows high speed printing, but the ink viscosity and the resolution vary depending on the printing method, and the equipment research on the device manufacturing process has not yet conducted enough.

The report contains the application trend and in-depth analysis of key patents on the roll-to-roll processing technology.

Looking at the application trend of 483 patents on roll-to-roll processing technology, the number of applications has continuously increased since mid 2000s, and many were applied in the U.S. Major applicants include 3M Innovative Properties, SiPix Imaging, Fuji Film, and General Electric. Amid vigorous developments of roll-to-roll processing technologies, competition among companies in the U.S., Japan, and South Korea gets increasingly fierce.

Roll-to-roll Processing Technology Patent Application Trends by Year/Country

 

Source: Displaybank, “Key Patent Analysis—Flexible Roll-to-roll Processing Technology”

Of a total of 483 roll-to-roll processing technology patents, 23 flexible OLED-related U.S. published/issued patents and 9 international patents were extracted as key patents. In-depth analyses were conducted on the 32 key patents after divided into the roll-to-roll manufacturing processing technology and apparatus technology. The key patent analysis includes key patent status, technology development map, and abstract.

January 22, 2013 – Reports are circling around Apple’s supply chain of a potential shift in the company’s display strategy for its future iPhones and iPads — moving back to LCDs and away from touch panels — but a drastic realignment of its supply chain is probably not likely, observes DisplaySearch.

Calvin Hsieh, senior analyst at DisplaySearch, cites a report from China that Innolux has delivered "touch on display" samples for the iPhone, another China report that Innolux and AU Optronics have provided "one-glass solution" (OGS) samples for the iPad Mini, and his firm’s own analysis that the iPhone 5 uses in-cell touch technology but the iPad mini uses a glass/film dual ITO (GF2, or DITO) structure. With both those processes struggling to attain good yields, could Apple end up changing its display technology adoption midstream?

TOD is a proprietary on-cell touch technology developed by Innolux in which the sensor is located on the upper glass (the color filter substrate) beneath the top polarizer. On-cell touch combines both LCD and touch so it must meet Apple’s LCD display requirements; Hsieh notes, adding that Innolux accounted for less than 10% of iPhone 4 display shipments (3.5-in, 960×640). "If Apple were to adopt TOD, it would very likely request that Innolux share its technology, structure or even patents with Apple’s other LCD suppliers in order to ensure adequate supply," he writes," and Apple also probably would want to take over the controller IC and algorithm from any Innolux partners (e.g. Synaptics). Apple already owns DITO patents, he adds.

The OGS display technology is an even more complex problem, Hsieh points out. OGS integrates the touch ITO sensor circuits into the cover glass, via two possible methods: a piece type such as "touch on lens" (TOL) or a sheet type, each accomplished with a different process. Either way the X-Y sensor patterns are on the same side of the substrate, so it’s called a "SITO" structure or "G2." Touch panel maker TPK owns patents for the piece-type OGS method, and claim they have key SITO patents as well and are suing Nokia and Chinese panel maker O-film, Hsieh notes; whether the aforementioned Innolux-AUO partnership could produce the technology given the TPK patents is unclear, he says.

There’s more to Apple use of OGS display if it chooses that route. Sheet-type OGS has a compressive cover-glass strength of 500-6600 Mpa; Corning’s IOX-FS and Gorilla glass have 600-700 Mpa for smartphone sizes and cannot be used in sheet type, Hsieh says. Piece type has the higher CS value but are difficult to mask-stamp and align under lithography, and throughput may be low.

Among iPhone 5 panel suppliers only LG Display offers everything from in-cell touch LCD to cover glass lamination (consigned by Apple), Hsieh notes. Other in-cell touch LCD makers Japan Display and Sharp rely on partners for the cover glass. If Innolux and AUO continue with their OGS partnership, they have a choice:

  • An integrated offering of LCD, OGS sheet patterning (cover glass with SITO sensor), and lamination let Apple specify the IOX-FS glass sheet with compressive strength of Gorilla 1; "In this scenario, LG Display will never give up and must be one of the suppliers," he notes.

  • Integrate the LCD, OGS piece-type sensor patterning, and lamination, using consigned cover glass pieces from other finishers (e.g. Lens One). The challenge here is expanding tools, throughput, and yield for piece-type patterning, to be acceptable for the iPhone’s >100M unit base.

All that is somewhat speculation, though, because long-term Apple touch supplier TPK already "has excellent OGS sheet and piece-type technology, and high lamination yield rates," and is unlikely to simply hand over that business to new entrants. "Although AUO and Innolux have advantages as LCD makers and can shorten the supply chain by producing LCD and touch at the same time, TPK has strength in OGS integration from sensor patterning, cover glass finishing (for sheet type), to module lamination," Hsieh writes. "Thus, there is a good chance that TPK will once again be a key touch supplier to Apple if it decides to change touch structures."

January 22, 2012 – The Fraunhofer Institute for Applied Polymer Research (IAP) in Potsdam-Golm and fab/cleanroom developer MBRAUN have commissioned a new "near industrial-scale" pilot line for organic light-emitting diodes (OLEDs) and organic solar cells.

The 15m-long pilot line, dubbed the Pilot Plant for Solution-based Processes for Organic Electronics at Fraunhofer IAP’s Application Center for Innovative Polymer Technologies, was commissioned during a two-day workshop last week (Jan. 15-16) entitled "Solution-based Organic Electronics: From Materials to Technology."

Showing the new ability to extend of previous laboratory-scale work, part of the ceremony apparently included showing a 1:20 scale bus shelter (10cm high), designed by a joint project of IAP and fdesign and funded by the Federal Ministry of Research. The mini-shelter is solar powered with partially transparent organic solar cells integrated into the roof and sidewall; OLEDs display the schedule or give light signals when a bus arrives. The Potsdam Fraunhofer Institute developed the OLEDs as well as the organic solar cells.

"The model shows that organic electronics has great design potential for energy-saving, intelligent lighting control and information systems," stated Armin Wedel, division director at Fraunhofer IAP. "To apply these technologies to life-size street furniture, the new pilot line now offers the possibility to realize organic electronic components under near-industrial conditions — a crucial prerequisite for the later transfer into commercial products."

Martin Reinelt, CEO of MBRAUN, added his hope that such partnerships can "strengthen the German research landscape in order to compete successfully with American and Asian research institutions. We also want to demonstrate the performance of German plant manufacturing."