Tag Archives: letter-leds-tech

A research team led by UCLA scientists and engineers has developed a method to make new kinds of artificial “superlattices” — materials comprised of alternating layers of ultra-thin “two-dimensional” sheets, which are only one or a few atoms thick. Unlike current state-of-the art superlattices, in which alternating layers have similar atomic structures, and thus similar electronic properties, these alternating layers can have radically different structures, properties and functions, something not previously available.

This is an artist's concept of two kinds of monolayer atomic crystal molecular superlattices. On the left, molybdenum disulfide with layers of ammonium molecules, on the right, black phosphorus with layers of ammonium molecules. Credit: UCLA Samueli Engineering

This is an artist’s concept of two kinds of monolayer atomic crystal molecular superlattices. On the left, molybdenum disulfide with layers of ammonium molecules, on the right, black phosphorus with layers of ammonium molecules. Credit: UCLA Samueli Engineering

For example, while one layer of this new kind of superlattice can allow a fast flow of electrons through it, the other type of layer can act as an insulator. This design confines the electronic and optical properties to single active layers, and prevents them from interfering with other insulating layers.

Such superlattices can form the basis for improved and new classes of electronic and optoelectronic devices. Applications include superfast and ultra-efficient semiconductors for transistors in computers and smart devices, and advanced LEDs and lasers.

Compared with the conventional layer-by-layer assembly or growth approach currently used to create 2D superlattices, the new UCLA-led process to manufacture superlattices from 2D materials is much faster and more efficient. Most importantly, the new method easily yields superlattices with tens, hundreds or even thousands of alternating layers, which is not yet possible with other approaches.

This new class of superlattices alternates 2D atomic crystal sheets that are interspaced with molecules of varying shapes and sizes. In effect, this molecular layer becomes the second “sheet” because it is held in place by “van der Waals” forces, weak electrostatic forces to keep otherwise neutral molecules “attached” to each other. These new superlattices are called “monolayer atomic crystal molecular superlattices.”

The study, published in Nature, was led by Xiangfeng Duan, UCLA professor of chemistry and biochemistry, and Yu Huang, UCLA professor of materials science and engineering at the UCLA Samueli School of Engineering.

“Traditional semiconductor superlattices can usually only be made from materials with highly similar lattice symmetry, normally with rather similar electronic structures,” Huang said. “For the first time, we have created stable superlattice structures with radically different layers, yet nearly perfect atomic-molecular arrangements within each layer. This new class of superlattice structures has tailorable electronic properties for potential technological applications and further scientific studies.”

One current method to build a superlattice is to manually stack the ultrathin layers one on top of the other. But this is labor-intensive. In addition, since the flake-like sheets are fragile, it takes a long time to build because many sheets will break during the placement process. The other method is to grow one new layer on top of the other, using a process called “chemical vapor deposition.” But since that means different conditions, such as heat, pressure or chemical environments, are needed to grow each layer, the process could result in altering or breaking the layer underneath. This method is also labor-intensive with low yield rates.

The new method to create monolayer atomic crystal molecular superlattices uses a process called “electrochemical intercalation,” in which a negative voltage is applied. This injects negatively charged electrons into the 2D material. Then, this attracts positively charged ammonium molecules into the spaces between the atomic layers. Those ammonium molecules automatically assemble into new layers in the ordered crystal structure, creating a superlattice.

“Think of a two-dimensional material as a stack of playing cards,” Duan said. “Then imagine that we can cause a large pile of nearby plastic beads to insert themselves, in perfect order, sandwiching between each card. That’s the analogous idea, but with a crystal of 2D material and ammonium molecules.”

The researchers first demonstrated the new technique using black phosphorus as a base 2D atomic crystal material. Using the negative voltage, positively charged ammonium ions were attracted into the base material, and inserted themselves between the layered atomic phosphorous sheets.”

Following that success, the team inserted different types of ammonium molecules with various sizes and symmetries into a series of 2D materials to create a broad class of superlattices. They found that they could tailor the structures of the resulting monolayer atomic crystal molecular superlattices, which had a diverse range of desirable electronic and optical properties.”The resulting materials could be useful for making faster transistors that consume less power, or for creating efficient light-emitting devices,” Duan said.

Samsung Electronics Co., Ltd. today announced that it has achieved the industry’s highest light efficacies for its fillet-enhanced chip-scale package (FEC) LED lineup – LM101B, LH181B and LH231B.

Initially chip-scale package (CSP) LEDs had not been widely used in mainstream LED lighting markets due to relatively lower efficacy levels compared to conventional LED packages. However, the newly upgraded, efficacy-leading FECs can be applied to most mainstream LED lighting environments, including ambient, downlight, spotlight, high bay, canopy and street lighting applications.

“Since introducing CSP technology to the industry in 2014, we have put extensive effort into advancing the performance levels and design flexibility of every one of our CSP LEDs,” said Yoonjoon Choi, Vice President of the LED Business Team at Samsung Electronics. “Samsung will continue to bolster its competitive edge in CSP technology, enabling the widest variety of luminaire designs with exceptional performance, reliability and cost benefits for lighting manufacturers worldwide.”

The enhanced FEC LEDs are based on Samsung’s most up-to-date CSP technology which builds TiO2 (Titanium dioxide) walls around the side surfaces of the chip to direct light output upwards. The technology provides considerably higher light efficacy than conventional CSP LEDs while offering greater flexibility for luminaire designers. Moreover, dramatically reduced cross-talk between neighboring packages allows each package to be placed in close proximity to one another.

Building on these advancements, the revamped FEC LED packages achieve the industry’s highest light efficacy levels, to suit an even wider range of lighting applications. The mid-power CSP, LM101B, features an increased efficacy of 205 lm/W (65mA, CRI 80+, 5000K), which is the highest among 1W-class, mid-power CSP LEDs. The 3W-class LH181B provides the highest light efficacy in its class with 190lm/W (350mA, CRI 70+, 5000K), which represents a more than 10-percent enhancement over the previous version. The 5W-class LH231B package continues to offer 170lm/W (700mA, CRI 70+, 5000K), the industry’s highest efficacy for the 5W class.

With Samsung FEC’s small form factor and reduced cross-talk, the LM101B is particularly well suited for spotlighting applications where packages can be densely placed within a small light-emitting surface area. Samsung also made the LM101B much simpler to mount compared to other mid-power CSP LEDs, by modifying the electrode pad.

In addition, the LH181B operates at a maximum current of 1.4A (Amps), making it an ideal component for high-power LED luminaires requiring superior lumen density.

The Samsung FEC lineup, now in mass production, is available in a full range of color temperature (CCT) and color rendering index (CRI) options.

A crystal method

January 31, 2018

From Mother Nature to our must-have devices, we’re surrounded by crystals. Those courtesy of the former, such as ice and snow, can form spontaneously and symmetrically. But the silicon-based or gallium nitride crystals found in LEDs and other electronics require a bit of coaxing to attain their ideal shapes and alignments.

At UC Santa Barbara, researchers have now unlocked another piece of the theoretical puzzle that governs the growth of crystals — a development that may save time and energy in the many processes that require crystal formation.

“The way most industrial processes are designed today is by doing an exhaustively large number of experiments to find out how crystals grow and at what rate they grow under different conditions,” said UCSB chemical engineer Michael Doherty, an author of a paper that appears in the Proceedings of the National Academy of Sciences. Snowflakes, for instance, form differently as they fall, depending on variable conditions such as temperature and humidity, hence the widely held belief that no two are alike. After determining the optimal conditions for the growth of the crystal of choice, Doherty added equipment must be designed and calibrated to provide a consistent growing environment.

However, by pooling decades of expertise, Doherty, along with UCSB colleague Baron Peters and former graduate student Mark Joswiak (now at Dow Chemical) have developed a computational method to help predict growth rates for ionic crystals under different circumstances. Using a relatively simple crystal — sodium chloride (NaCl, more familiarly known as table salt) — in water, the researchers laid the groundwork for the analysis of more complex crystals.

Ionic crystals may appear to the naked eye — and even under some magnification — to consist of perfectly smooth and even faces. But look more closely and you’ll often find they actually contain surface features that influence their ability to grow, and the larger shapes that they take.

“There are dislocations and around the dislocations there are spirals, and around the spirals there are edges, and around the edges there are kinks,” Peters said, “and every level requires a theory to describe the number of those features and the rates at which they change.” At the smallest scale, ions in solution cannot readily attach to the growing crystal because water molecules that solvate (interact with) the ions are not readily dislodged, he said. With so many processes occurring at so many scales, it’s easy to see how difficult it can be to predict a crystal’s growth.

“The largest challenge was applying the various techniques and methods to a new problem — examining ion attachment and detachment at surface kink sites, where there is a lack of symmetry coupled with strong ion-water interactions,” Joswiak said. “However, as we encountered problems and found solutions, we gained additional insight on the processes, the role of water molecules and differences between sodium and chloride ions.”

Among their insights: Ion size matters. The researchers found that due to its size, the larger chloride ion (Cl-) prevents water from accessing kink sites during detachment, limiting the overall rate of sodium chloride dissolution in water.

“You have to find a special coordinate system that can reveal those special solvent rearrangements that create an opening for the ion to slip through the solvent cage and lock onto the kink site,” Peters said. “We demonstrated that at least for sodium chloride we can finally give a concrete answer.”

This proof-of-concept development is the result of the Doherty Group’s expertise with crystallization processes coupled with the Peters Group’s expertise in “rare events” — relatively infrequent and short-lived but highly significant phenomena (such as reactions) that fundamentally change the state of the system. Using a method called transition path sampling, the researchers were able to understand the events leading up to the transition state. The strategy and mechanistic insights from the work on sodium chloride provides a blueprint for predicting growth rates in materials synthesis, pharmaceuticals and biomineralization.

For the first time an international research group has revealed the core mechanism that limits the indium (In) content in indium gallium nitride ((In, Ga)N) thin films – the key material for blue light emitting diodes (LED). Increasing the In content in InGaN quantum wells is the common approach to shift the emission of III-Nitride based LEDs towards the green and, in particular, red part of the optical spectrum, necessary for the modern RGB devices. The new findings answer the long-standing research question: why does this classical approach fail, when we try to obtain efficient InGaN-based green and red LEDs?

This is a scanning transmission electron microscopy image of the atomic ordering in (In, Ga)N monolayer: single atomic column, containing only indium (In) atoms (shown by higher intensity on the image), followed by two, containing only gallium (Ga) atoms. Credit: IKZ Berlin

This is a scanning transmission electron microscopy image of the atomic ordering in (In, Ga)N monolayer: single atomic column, containing only indium (In) atoms (shown by higher intensity on the image), followed by two, containing only gallium (Ga) atoms. Credit: IKZ Berlin

Despite the progress in the field of green LEDs and lasers, the researchers could not overcome the limit of 30% of indium content in the films. The reason for that was unclear up to now: is it a problem of finding the right growth conditions or rather a fundamental effect that cannot be overcome? Now, an international team from Germany, Poland and China has shed new light on this question and revealed the mechanism responsible for that limitation.

In their work the scientists tried to push the indium content to the limit by growing single atomic layers of InN on GaN. However, independent on growth conditions, indium concentrations have never exceeded 25% – 30% – a clear sign of a fundamentally limiting mechanism. The researchers used advanced characterization methods, such as atomic resolution transmission electron microscope (TEM) and in-situ reflection high-energy electron diffraction (RHEED), and discovered that, as soon as the indium content reaches around 25 %, the atoms within the (In, Ga)N monolayer arrange in a regular pattern – single atomic column of In alternates with two atomic columns of Ga atoms. Comprehensive theoretical calculations revealed that the atomic ordering is induced by a particular surface reconstruction: indium atoms are bonded with four neighboring atoms, instead of expected three. This creates stronger bonds between indium and nitrogen atoms, which, on one hand, allows to use higher temperatures during the growth and provides material with better quality. On the other hand, the ordering sets the limit of the In content of 25%, which cannot be overcome under realistic growth conditions.

“Apparently, a technological bottleneck hampers all the attempts to shift the emission from the green towards the yellow and the red regions of the spectra. Therefore, new original pathways are urgently required to overcome these fundamental limitations,” states Dr. Tobias Schulz, scientist at the Leibniz-Institut fuer Kristallzuechtung; “for example, growth of InGaN films on high quality InGaN pseudo-substrates that would reduce the strain in the growing layer.”

However, the discovery of ordering may help to overcome well known limitations of the InGaN material system: localization of charge carriers due to fluctuations in the chemical composition of the alloy. Growing stable ordered (In, Ga)N alloys with the fixed composition at high temperatures could thus improve the optical properties of devices.

Littelfuse, Inc. today introduced four new series of 1200V silicon carbide (SiC) Schottky Diodes from its GEN2 product family, which was originally released in May 2017.

The LSIC2SD120A08 Series, LSIC2SD120A15 Series, and LSIC2SD120A20 Series offer current ratings of 8A, 15A ,20A, respectively and are provided in the popular TO-220-2L package. Additionally, the LSIC2SD120C08 Series offers a current rating of 8A in a TO-252-2L package. The merged p-n Schottky (MPS) device architecture of the GEN2 SiC Schottky Diodes enhances surge capability and reduces leakage current. Replacing standard silicon bipolar power diodes with the new GEN2 SiC Schottky Diodes allows circuit designers to reduce switching losses dramatically, accommodate large surge currents without thermal runaway, and operate at junction temperatures as high as 175°C. This allows for substantial increases in power electronics system efficiency and robustness.

Typical applications for these new GEN2 SiC Schottky Diodes include:

  • Active power factor correction (PFC).
  • Buck or boost stages in DC-DC converters.
  • Free-wheeling diodes in inverter stages.
  • High-frequency output rectification.

The markets they can serve include industrial power supplies, solar energy, industrial motor drives, welding and plasma cutting, EV charging stations, inductive cooking fields and many others.

“The latest GEN2 SiC Schottky Diodes are ideal solutions for circuit designers who need to reduce switching losses, accommodate large surge currents without thermal runaway, and operate at higher junction temperatures,” said Michael Ketterer, Global Product Marketing Manager, Power Semiconductors at Littelfuse. “They expand the component options available to circuit designers striving to improve the efficiency, reliability, and thermal management of the latest power electronics systems.”

LSIC2SD120A08 Series, LSIC2SD120A15 Series, and LSIC2SD120A20 Series GEN2 1200V SiC Schottky Diodes are available in TO-220-2L packages in tubes in quantities of 1,000. Meanwhile,LSIC2SD120C08 Series GEN2 1200V SiC Schottky Diodes are available in TO-252-2L package in tape and reel in quantities of 2,500.  Sample requests may be placed through authorized Littelfuse distributors worldwide.

A discovery by an international team of researchers from Princeton University, the Georgia Institute of Technology and Humboldt University in Berlin points the way to more widespread use of an advanced technology generally known as organic electronics.

The research, published in the journal Nature Materials, focused on organic semiconductors, a class of materials prized for their applications in emerging technologies such as flexible electronics, solar energy conversion, and high-quality color displays for smartphones and televisions. In the short term, the advancement could particularly help with organic light-emitting diodes that operate at high energy to emit colors such as green and blue.

Researchers used ultraviolet light to excite molecules in a semiconductor, triggering reactions that split up and activated a dopant. Credit: Princeton University / Jing Wang and Xin Lin

Researchers used ultraviolet light to excite molecules in a semiconductor, triggering reactions that split up and activated a dopant. Credit: Princeton University / Jing Wang and Xin Lin

“Organic semiconductors are ideal materials for the fabrication of mechanically flexible devices with energy-saving, low-temperature processes,” said Xin Lin, a doctoral student and a member of the Princeton research team. “One of their major disadvantages has been their relatively poor electrical conductivity. In some applications, this can lead to difficulties and inefficient devices. We are working to improve the electrical properties of organic semiconductors.”

Semiconductors, typically made of silicon, are the foundation of modern electronics because engineers can take advantage of their unique properties to control electrical currents. Among many applications, semiconductor devices are used for computing, signal amplification, and switching. They are used in energy-saving devices such as light-emitting diodes and devices that convert energy such as solar cells.

Essential to these functionalities is a process called doping, in which the semiconductor’s chemical makeup is modified by adding a small amount of chemicals or impurities. By carefully choosing the type and amount of dopant, researchers can alter semiconductors’ electronic structure and electrical behavior in a variety of ways.

In their Nature Materials paper, the researchers have described a new approach for greatly increasing the conductivity of organic semiconductors, formed of carbon-based molecules rather than silicon atoms. The dopant, a ruthenium-containing compound, was a reducing agent, which means it added electrons to the organic semiconductor as part of the doping process. The addition of the electrons was the key to increasing the semiconductor’s conductivity. The compound belongs to a newly-introduced class of dopants called dimeric organometallic dopants. Unlike many other powerful reducing agents, these dopants are stable when exposed to air but still work as strong electron donors both in solution and solid state.

Georgia Tech’s Seth Marder, a Regents Professor in the School of Chemistry and Biochemistry, and Stephen Barlow, a research scientist in the school, led the development of the new dopant. They called the ruthenium compound a “hyper-reducing dopant.”

They said it was unusual, not only in its combination of electron donation strength and air stability but also in its ability to work with a class of organic semiconductors that have previously been very difficult to dope. In studies conducted at Princeton, the researchers found that the new dopant increased the conductivity of these semiconductors by about a million times.

The ruthenium compound was a dimer, meaning it consisted of two identical molecules, or monomers, connected by a chemical bond.  As is, the compound proved relatively stable and, when added to these difficult-to-dope semiconductors, it did not react and remained in its equilibrium state. That posed a problem because to increase the conductivity of the organic semiconductor, the ruthenium dimer needed to split and release its two identical monomers.

Princeton’s Lin, the study’s lead author, said the researchers looked for different ways to break up the ruthenium dimer and activate the doping. Eventually, he and Berthold Wegner, a visiting graduate student from the group of Norbert Koch at Humboldt University, took a hint from how photosynthetic systems work. They irradiated the system with ultraviolet light, which excited molecules in the semiconductor and initiated the reaction. Under exposure to the light, the dimers were able to dope the semiconductor, leading to a roughly 100,000 times increase in the conductivity.

After that, the researchers made an interesting observation.

“Once the light was turned off, one might naively expect the reverse reaction to occur and the increased conductivity to disappear,” said Georgia Tech’s Marder, who is also associate director of the Center for Organic Photonics and Electronics (COPE) at Georgia Tech. “However, this was not the case.”

The researchers found that the ruthenium monomers remained isolated in the semiconductor, increasing conductivity, even though thermodynamics should have returned the molecules to their original configuration as dimers. Antoine Kahn, a Princeton professor who led the research team, said the physical layout of the molecules inside the doped semiconductor provides a likely answer to this puzzle. The hypothesis is that the monomers are scattered in the semiconductor in such a way that it was very difficult for them to return to their original configuration and re-form the ruthenium dimer. To recombine, he said, the monomers would have to have faced in the correct orientation, but in the mixture, they remained askew. So, even though thermodynamics showed that dimers should reform, most never snapped back together.

“The question is why aren’t these things moving back together into equilibrium,” said Kahn, who is Stephen C. Macaleer ’63 Professor in Engineering and Applied Science. “The answer is they are kinetically trapped.”

In fact, the researchers observed the doped semiconductor for over a year and found very little decrease in the electrical conductivity. Also, by observing the material in light-emitting diodes fabricated by the group of Barry Rand, an assistant professor of electrical engineering at Princeton and the Andlinger Center for Energy and the Environment, the researchers discovered that doping was continuously re-activated by the light produced by the device.

“The light activates the system more, which leads to more light production and more activation until the system is fully activated, said Marder, who is Georgia Power Chair in Energy Efficiency. “This alone is a novel and surprising observation.”

The paper was co-authored by Kyung Min Lee, Michael A. Fusella, and Fengyu Zhang, of Princeton, and Karttikay Moudgil of Georgia Tech. Research was funded by the National Science Foundation (grants DMR-1506097, DMR-1305247), the Department of Energy’s Energy Efficiency & Renewable Energy Solid-State Lighting program (award DE-EE0006672) and the DoE’s Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (award DE-SC0012458), the Deutsche Forschungsgemeinschaft (project SFB 951) and the Helmholtz Energy-Alliance Hybrid Photovoltaics project.

An international team of researchers from ETH Zurich, IBM Research Zurich, Empa and four American research institutions have found the explanation for why a class of nanocrystals that has been intensively studied in recent years shines in such incredibly bright colours. The nanocrystals contain caesium lead halide compounds that are arranged in a perovskite lattice structure.

Three years ago, Maksym Kovalenko, a professor at ETH Zurich and Empa, succeeded in creating nanocrystals – or quantum dots, as they are also known – from this semiconductor material. “These tiny crystals have proved to be extremely bright and fast emitting light sources, brighter and faster than any other type of quantum dot studied so far,” says Kovalenko. By varying the composition of the chemical elements and the size of the nanoparticles, he also succeeded in producing a variety of nanocrystals that light up in the colours of the whole visible spectrum. These quantum dots are thus also being treated as components for future light-emitting diodes and displays.

In a study published in the most recent edition of the scientific journal Nature, the international research team examined these nanocrystals individually and in great detail. The scientists were able to confirm that the nanocrystals emit light extremely quickly. Previously-studied quantum dots typically emit light around 20 nanoseconds after being excited when at room temperature, which is already very quick. “However, caesium lead halide quantum dots emit light at room temperature after just one nanosecond,” explains Michael Becker, first author of the study. He is a doctoral student at ETH Zurich and is carrying out his doctoral project at IBM Research.

A cesium lead bromide nanocrystal under the electron microscope (crystal width: 14 nanometer). Individual atoms are visible as points. Credit: ETH Zurich / Empa / Maksym Kovalenko

A cesium lead bromide nanocrystal under the electron microscope (crystal width: 14 nanometer). Individual atoms are visible as points. Credit: ETH Zurich / Empa / Maksym Kovalenko

Electron-hole pair in an excited energy state

Understanding why caesium lead halide quantum dots are not only fast but also very bright entails diving into the world of individual atoms, light particles (photons) and electrons. “You can use a photon to excite semiconductor nanocrystals so that an electron leaves its original place in the crystal lattice, leaving behind a hole,” explains David Norris, Professor of Materials Engineering at ETH Zurich. The result is an electron-hole pair in an excited energy state. If the electron-hole pair reverts to its energy ground state, light is emitted.

Under certain conditions, different excited energy states are possible; in many materials, the most likely of these states is called a dark one. “In such a dark state, the electron hole pair cannot revert to its energy ground state immediately and therefore the light emission is suppressed and occurs delayed. This limits the brightness”, says Rainer Mahrt, a scientist at IBM Research.

No dark state

The researchers were able to show that the caesium lead halide quantum dots differ from other quantum dots: their most likely excited energy state is not a dark state. Excited electron-hole pairs are much more likely to find themselves in a state in which they can emit light immediately. “This is the reason that they shine so brightly,” says Norris.

The researchers came to this conclusion using their new experimental data and with the help of theoretical work led by Alexander Efros, a theoretical physicist at the Naval Research Laboratory in Washington. He is a pioneer in quantum dot research and, 35 years ago, was among the first scientists to explain how traditional semiconductor quantum dots function.

Great news for data transmission

As the examined caesium lead halide quantum dots are not only bright but also inexpensive to produce they could be applied in television displays, with efforts being undertaken by several companies, in Switzerland and world-wide. “Also, as these quantum dots can rapidly emit photons, they are of particular interest for use in optical communication within data centres and supercomputers, where fast, small and efficient components are central,” says Mahrt. Another future application could be the optical simulation of quantum systems which is of great importance to fundamental research and materials science.

ETH professor Norris is also interested in using the new knowledge for the development of new materials. “As we now understand why these quantum dots are so bright, we can also think about engineering other materials with similar or even better properties,” he says.

By Inna Skvortsova, SEMI

Electromagnetic interference (EMI) is an increasingly important topic across the global electronics manufacturing supply chain.  Progressively smaller geometries of ICs, lower supply voltages, and higher data rates all make devices and processes more vulnerable to EMI. Electrical noise, EMI-induced signal generated by equipment, and factors such as power line transients affect manufacturing processes, from wafer handling to wire bonding to PCB assembly and test, causing millions of dollars in losses to the industry. Furthermore, conducted emission capable of causing electrical overstress (EOS) can damage sensitive semiconductor devices.  Intel consistently names EOS as the “number one source of damage to IC components.” (Intel® Manufacturing Enabling Guide 2001, 2010, 2016).

While EMC (Electromagnetic Compatibility) standards, such as the European EMC Directive and FCC Testing and Certification, etc. provide limits on allowed emission levels of equipment, once the equipment is installed along with other tools, the EMI levels in actual operating environments can be substantially different and therefore impact the equipment operation, performance, and reliability. For example, (i) Occasional transients induce “extra” pulses in rotary feedback of the servo motor which in time contributes to robotic arm’s erroneous position eventually damaging the wafer; (ii) Combination of high-frequency noise from servo motors and switched mode power supplies in the tool creates difference in voltage between the bonding wire/funnel and the device which causes high current and eventual electrical overstress to the devices; (iii) Wafer probe test provides inconsistent results due to high level of EMI on the wafer chuck caused by a combination of several servo motors in the wafer handler.  Field cases like these illustrate the gap between EMC test requirements and real-life EMI tolerance levels and its impact on semiconductor manufacturing and handling.

EMI on AC power lines

EMI on AC power lines

New standard, SEMI E176-1017, Guide to Assess and Minimize Electromagnetic Interference (EMI) in a Semiconductor Manufacturing Environment, developed by the NA Chapter of the Global Metrics Technical Committee bridges this gap. Targeted to IC manufacturers and anyone handling semiconductor devices, such as PCB assembly and integration of electronic devices, SEMI E176 is a practical guide as well as an educational document. SEMI E176 provides a concise summary of EMI origins, EMI propagation, measurement techniques and recommendations on mitigation of undesirable electromagnetic emission to enable equipment co-existence and proper operation as well as reduction of EOS in its intended usage environment. Specifically, E176 provides recommended levels for different types of EMI based on IC geometries.

“SEMI E176 is likely the only active Standard in the entire industry providing recommendations on both acceptable levels of EMI in manufacturing environments and the means of achieving and maintaining these numbers,” said Vladimir Kraz, co-Chair of the NA Metrics Technical Committee and president of OnFILTER, Inc. “E176 is also unique because it is not limited just to semiconductor manufacturing, but has application across other industries.  Back-end assembly and test, as well as PCB assembly are just as affected by EMI and can benefit from SEMI E176 implementation as there are strong similarities between handling of semiconductor devices in IC manufacturing and in PCB assemblies and prevention of defects is often shared between IC and PCBA manufacturers.”

The newly published SEMI E176 and recently updated SEMI E33-0217, Guide for Semiconductor Manufacturing Equipment Electromagnetic Compatibility (EMC),provide complete documentation for establishing and maintaining low EMI levels in the manufacturing environment.

Undesirable emission has operational, liability and regulatory consequences.  Taming it is a challenging task and requires a comprehensive approach that starts from proper system design practices and ends with developing EMI expertise in the field.  The new SEMI 176 provides practical guidance on reducing EMI to the levels necessary for effective high yield semiconductor manufacturing today and in the future.

SEMI Standards development activities take place throughout the year in all major manufacturing regions. To get involved, join the SEMI International Standards Program at: www.semi.org/standardsmembership.


Texas Instruments (TI) (NASDAQ: TXN) today introduced the first 3-channel high-side linear automotive light-emitting diode (LED) controller without internal MOSFETs which gives designers greater flexibility for their lighting designs. The TPS92830-Q1’s novel architecture enables higher power and better thermal dissipation than conventional LED controllers, and are particularly beneficial for automotive LED lighting applications that require high performance and reliability.

Conventional LED drivers integrate the MOSFET, which limits designers’ ability to customize features. With that type of driver, designers often must make significant design modifications to achieve the desired system performance. The TPS92830-Q1 LED controller’s flexible on-board features give designers the freedom to select the best MOSFET for their system requirements. With this new approach, designers can more quickly and efficiently optimize their lighting power designs for automotive system requirements and desired dimming features.

Key features and benefits

  • Flexibility: The on-chip pulse-width modulation (PWM) generator or PWM input enables flexible dimming. Designers can use either the analog control or PWM to manage an output current of more than 150 mA per channel, to power automotive rear combination lamps and daytime running lights.
  • Improved thermal dissipation: By pairing the LED controller with an external MOSFET, the designer can achieve the required high power output while distributing the power across the controller and MOSFET to avoid system overheating. By retaining linear architecture, the TPS92830-Q1 provides improved electromagnetic interference (EMI) and electromagnetic compatibility (EMC) performance.
  • Greater system reliability: Advanced protection and built-in open and short detection features help designers meet original equipment manufacturer (OEM) system reliability requirements. The output current derating feature protects the external MOSFET under high voltage conditions to ensure system reliability.

The TPS92830-Q1 expands TI’s extensive portfolio of LED drivers, design tools and technical resources that help designers implement innovative automotive lighting features.

Researchers at the University of Liverpool have made a discovery that could improve the conductivity of a type of glass coating which is used on items such as touch screens, solar cells and energy efficient windows.

Coatings are applied to the glass of these items to make them electrically conductive whilst also allowing light through. Fluorine doped tin dioxide is one of the materials used in commercial low cost glass coatings as it is able to simultaneously allow light through and conduct electrical charge but it turns out that tin dioxide has as yet untapped potential for improved performance.

Compensating acceptor fluorine interstitials (light green) dramatically reduce electronic performance of tin dioxide transparent conducting glass coatings doped with fluorine atoms (dark green). Credit: University of Liverpool

Compensating acceptor fluorine interstitials (light green) dramatically reduce electronic performance of tin dioxide transparent conducting glass coatings doped with fluorine atoms (dark green). Credit: University of Liverpool

In a paper published in the journal Advanced Functional Materials, physicists identify the factor that has been limiting the conductivity of fluorine doped tin dioxide, which should be highly conductive because fluorine atoms substituted on oxygen lattice sites are each expected to give an additional free electron for conduction.

The scientists report, using a combination of experimental and theoretical data, that for every two fluorine atoms that give an additional free electron, another one occupies a normally unoccupied lattice position in the tin dioxide crystal structure.

Each so-called “interstitial” fluorine atom captures one of the free electrons and thereby becomes negatively charged. This reduces the electron density by half and also results in increased scattering of the remaining free electrons. These combine to limit the conductivity of fluorine doped tin dioxide compared with what would otherwise be possible.

PhD student Jack Swallow, from the University’s Department of Physics and the Stephenson Institute for Renewable Energy, said: “Identifying the factor that has been limiting the conductivity of fluorine doped tin dioxide is an important discovery and could lead to coatings with improved transparency and up to five times higher conductivity, reducing cost and enhancing performance in a myriad of applications from touch screens, LEDs, photovoltaic cells and energy efficient windows.”

The researchers now intend to address the challenge of finding alternative novel dopants that avoid these inherent drawbacks.