Category Archives: LED Packaging and Testing

For the first time, researchers have created light-emitting diodes (LEDs) on lightweight flexible metal foil.

Engineers at The Ohio State University are developing the foil based LEDs for portable ultraviolet (UV) lights that soldiers and others can use to purify drinking water and sterilize medical equipment.

Nanowires were grown on titanium foil at The Ohio State University. CREDIT: Image by Brelon J. May, courtesy of The Ohio State University.

Nanowires were grown on titanium foil at The Ohio State University. Credit: Image by Brelon J. May, courtesy of The Ohio State University.

In the journal Applied Physics Letters, the researchers describe how they designed the LEDs to shine in the high-energy “deep” end of the UV spectrum. The university will license the technology to industry for further development.

Deep UV light is already used by the military, humanitarian organizations and industry for applications ranging from detection of biological agents to curing plastics, explained Roberto Myers, associate professor of materials science and engineering at Ohio State.

The problem is that conventional deep-UV lamps are too heavy to easily carry around.

“Right now, if you want to make deep ultraviolet light, you’ve got to use mercury lamps,” said Myers, who is also an associate professor of electrical and computer engineering. “Mercury is toxic and the lamps are bulky and electrically inefficient. LEDs, on the other hand, are really efficient, so if we could make UV LEDs that are safe and portable and cheap, we could make safe drinking water wherever we need it.”

He noted that other research groups have fabricated deep-UV LEDs at the laboratory scale, but only by using extremely pure, rigid single-crystal semiconductors as substrates–a strategy that imposes an enormous cost barrier for industry.

Foil-based nanotechnology could enable large-scale production of a lighter, cheaper and more environmentally friendly deep-UV LED. But Myers and materials science doctoral student Brelon J. May hope that their technology will do something more: turn a niche research field known as nanophotonics into a viable industry.

“People always said that nanophotonics will never be commercially important, because you can’t scale them up. Well, now we can. We can make a sheet of them if we want,” Myers said. “That means we can consider nanophotonics for large-scale manufacturing.”

In part, this new development relies on a well-established semiconductor growth technique known as molecular beam epitaxy, in which vaporized elemental materials settle on a surface and self-organize into layers or nanostructures. The Ohio State researchers used this technique to grow a carpet of tightly packed aluminum gallium nitride wires on pieces of metal foil such as titanium and tantalum.

The individual wires measure about 200 nanometers tall and about 20-50 nanometers in diameter–thousands of times narrower than a human hair and invisible to the naked eye.

In laboratory tests, the nanowires grown on metal foils lit up nearly as brightly as those manufactured on the more expensive and less flexible single-crystal silicon.

The researchers are working to make the nanowire LEDs even brighter, and will next try to grow the wires on foils made from more common metals, including steel and aluminum.

Using cutting-edge first-principles calculations, researchers at the University of California, Santa Barbara (UCSB) have demonstrated the mechanism by which transition metal impurities – iron in particular – can act as nonradiative recombination centers in nitride semiconductors. The work highlights that such impurities can have a detrimental impact on the efficiency of light-emitting diodes (LEDs) based on gallium nitride or indium gallium nitride.

This is a schematic illustration of Shockley-Read-Hall (SRH) recombination due to iron in GaN. Iron is a deep acceptor with a defect level (black line) close to the GaN conduction band (green). The charge density corresponding to this localized level is illustrated in the middle of the figure. Conventional SRH recombination (left) would proceed via electron capture from the conduction band into the defect level, but the overall rate would be limited by slow capture of holes because the defect level is far from the valence band (blue). The presence of excited states enhances the hole capture rate (right) such that the overall SRH recombination process becomes very efficient. Credit: Sonia Fernandez

This is a schematic illustration of Shockley-Read-Hall (SRH) recombination due to iron in GaN. Iron is a deep acceptor with a defect level (black line) close to the GaN conduction band (green). The charge density corresponding to this localized level is illustrated in the middle of the figure. Conventional SRH recombination (left) would proceed via electron capture from the conduction band into the defect level, but the overall rate would be limited by slow capture of holes because the defect level is far from the valence band (blue). The presence of excited states enhances the hole capture rate (right) such that the overall SRH recombination process becomes very efficient. Credit: Sonia Fernandez

For LEDs, high-purity material is essential to lighting technology, such as residential and commercial solid-state lighting, adaptive lighting for automobiles, and displays for mobile devices. Imperfections at the atomic scale can limit the performance of LEDs through a process known as Shockley-Read-Hall recombination. The operation of an LED relies on the radiative recombination of electrons and holes, which results in the emission of photons. Defects or impurities can act as a source of nonradiative recombination and prevent the emission of light, lowering the LED efficiency.

The UCSB researchers, in collaboration with researchers from Rutgers University, the University of Vienna, the KTH Royal Institute of Technology in Sweden and the Center for Physical Sciences and Technology in Lithuania, have identified that iron, even at concentrations less than parts-per-million, can be highly detrimental.

Transition metal impurities such as iron have long been known to severely impact devices based on traditional semiconductors such as silicon and gallium arsenide, leading these impurities to be referred to as “killer centers.” It is therefore surprising that little attention has been devoted to understanding the role of transition metals in recombination dynamics in GaN.

“A naïve application of Shockley-Read-Hall theory, based on an inspection of defect levels within the band gap, would lead one to conclude that iron in GaN would be harmless,” explained Dr. Darshana Wickramaratne, lead author on the paper. “However, our work shows that excited states of the impurity play a key role in turning it into a killer center.”

The UCSB scientists identified a recombination pathway by which iron can lead to severe efficiency loss. Sophisticated first-principles calculations were essential to identify and understand the role of the excited states in the recombination process.

“Taking these excited states into account completely changes the picture,” emphasized Dr. Audrius Alkauskas, another member of the research team. “We strongly suspect that such excited states play a key role in other recombination phenomena, opening up new avenues for research.”

The results highlight that strict control over growth and processing is required to prevent the unintentional introduction of transition metal impurities. Sources of iron contamination include the stainless steel reactors that are used in some growth techniques for nitride semiconductors.

“Increasing the efficiency of light emission is a key goal for the solid-state lighting industry,” said UCSB Materials Professor Chris Van de Walle, who led the research team. “Our work focuses attention on the detrimental impact of transition metals and the importance of suppressing their incorporation.”

What is your China strategy?


October 30, 2016

This article was originally posted on SemiMD.com and was featured in the October 2016 issue of Solid State Technology.

By Dave Lammers, Contributing Editor

Equipment vendors have a lot on their plates now, with memory customers pushing 3D NAND, foundries advancing to the 7 nm node, and 200mm fabs clamoring to come up with hard-to-find tools.

China, which has renewed its investments in displays, packaging, and both 200mm and 300mm front-end fab capacity, is another challenge.

“All the managers in my company are scrambling to adjust their budgets so they can support China. I can tell you people are booking lots of flights to Shanghai,” said one engineer at a major equipment supplier.

Bill McClean, president of IC Insights (Scottsdale, AZ), said China is fast becoming a center for 3D NAND production, as several companies expand production in China. Intel is converting its Dalian, China fab partly to 3D NAND, and Toshiba might very well make a deal in China to build a 3D NAND fab there, he said.

“China could be the 3D NAND capital of the world,” McClean said at The ConFab conference in Las Vegas. While the U.S. government limits exports of leading-edge technologies on national security concerns, 3D NAND relies more on overlay and etch techniques at relaxed (40nm) design rules, he noted.

“Since the 3D NAND makers are not pushing feature sizes, it doesn’t raise red flags like if Chinese companies wanted FinFET technology. That is when the alarms go off,” McClean said.

However, McClean said the 3D NAND market is not immune to the oversupply issues that now face the DRAM makers. “I’ve seen this rodeo before,” McClean said.

China’s domestic IC market is slightly more than $100 billion, McClean said, while chip production in China was about $13 billion last year, representing just under 5 percent of worldwide production (Figure 1).

The difference between consumption and domestic production, referred to as the delta, is made up by imports. “This 13 percent (from domestic suppliers) drives the Chinese government crazy. Yes, they will close that gap a little bit, but not to the extent that they think,” McClean told The ConFab audience in mid-June.

Robert Maire, who consulted for SMIC on its initial public offering in the United States, spoke at length about China at the SEMI Advanced Semiconductor Manufacturing Conference (ASMC) in Saratoga Springs, N.Y. Amid the mergers and acquisition frenzy of last year, China managed to pull off the acquisitions of CMOS image sensor vendor Omnivision, memory maker ISSI, the RF business of NXP, Pericom Semiconductor, and Mattson Technology. (McClean said he believes that if the Omnivision acquisition were attempted in today’s more China-wary environment that Washington would block the deal).

Maire, principal at Semiconductor Advisors (New York), said China is far behind in its domestic semiconductor production equipment business. “If China has 14nm production capacity, but buys all of its equipment from abroad, it doesn’t really help them that much. China is getting started in equipment, but it has a lot of catching up to do.”

Scott Foster, a partner in market intelligence firm TAP Japan (Tokyo), said China must have an international scope in the equipment sector if it hopes to compete with the likes of Applied, Lam, and other well-established vendors. A few of Japan’s equipment suppliers are succeeding while operating in relatively narrow niches, but overall, competing globally is a challenge for mid-sized Japanese equipment companies. “If this is what is happening to Japanese equipment vendors, what chance do Chinese companies have?” Foster said.

Packaging may prove to be key

Skeptics of China’s prospects might take a long look at China’s success in packaging, an area where China is succeeding, in part by acquisitions of Asia-based companies, notably STATS ChipPAC (Singapore), which was acquired by Jiangsu Changjiang Electronics Technology Co. (JCET) last year. Separately, SMIC and JCET formed a joint venture to focus on chip scale packaging, wafer bumping, and fan-out wafer level packaging. The packaging joint venture is located 90 minutes from Shanghai, said Sonny Hui, senior vice president of worldwide marketing at SMIC.

Jim Walker, the packaging analyst at market research firm Gartner, said China-based packaging is now valued at nearly half (43 percent) of all worldwide packaging value by IDMs and OSATs. While the packaging industry overall is dealing with price pressures, the advent of wafer level packaging, and other forms of multi-chip integration, bodes well for the higher end of the back-end industry.

“As the semiconductor industry matures and Moore’s Law scaling slows, multi-chip integration via packaging is providing system vendors with a faster time-to-market, and a lower-cost means, of solving system-level challenges,” Walker said.

Packaging multiple chips in a module is likely to play a key role in the Internet of Things (IoT) markets, Walker said. Automotive, medical, home, and consumer solutions are all “heavily reliant on packaging,” he said.

Sam Wang, a Gartner analyst who focuses on foundries, pointed out at Semicon West that China’s semiconductor industry faces continued challenges in a hotly contested foundry market. Few China-based foundries have enjoyed the strong growth that SMIC has demonstrated, he said. (SMIC has been “running at very high utilizations, and we are working very hard to solve the problem,” said SMIC’s Hui.)

While SMIC has enjoyed double-digit growth for several years, the five second-tier Chinese foundries – — Shanghai Huahong Grace, CSMC, HuaLi, XMC, and ASMC — saw declining revenues year-over-year in 2015. Overall, China-based foundries accounted for just 7.8 percent of total worldwide foundry capacity last year, and the overall growth rate by Chinese foundries “is way below the expectations of the Chinese government,” Wang said.

China-based companies are focusing partly on MEMS and other devices made on 200mm wafers, including analog, sensors, and power. SMIC’s Hui said “most of our customers don’t see much benefit to migrate to 12-inch. 200mm still has a lot of potential; just consider the hundreds of products still made on 180nm technology, which was developed 20 years ago. Many customers still see that as a sweet spot.”

Foster, who has three decades of tech-watching experience from his base in Tokyo, said the 200mm wafer fabs being built in China will make products that “do not need the gigantic scale” required of Intel, TSMC, Samsung and Toshiba. Figure 2, courtesy of SEMI, shows the seventeen 200mm wafer fabs/lines that are expected begin operation in 2015 to 2019. Six of the seventeen will be in China.

“After decades of trying, China has found a market-based strategy: building scale and experience from the bottom up. In the long run, this is likely to be far more effective than going out to buy foreign companies,” Foster said.

Display is another area China is counting on. In an Aug. 18 conference call following a strong quarter, Applied Materials chief financial officer Bob Halliday told analysts: “In display, we recorded record orders of $803 million with more than half coming from projects in China.”

The Applied CFO also said, “Just listening to the Chinese government, they’re in this for a long-term and their interest in investing in the semiconductor industry is probably only going to increase.”

Kateeva turns to China funds

China is often lumped together with other Asian nations as a country that has a government-led, me-too, follower mentality. But increasingly, China is either proving innovative itself, or able to quickly adopt innovations from the West.

At the Innovation Forum at Semicon West, Conor Madigan, co-founder of ink jet printer startup Kateeva (Newark, Calif.) spoke about the readiness of Chinese venture capital funds to step in where Silicon Valley-based VCs were overly hesitant. China proved a more receptive place to raise money than the United States, though the early establishment of the M.I.T. spinout did come from U.S. based sources.

After its initial development effort, Kateeva figured it needed more than $100 million to accomplish its goals. After making the rounds to raise funds in the United States without success, Kateeva turned to China, where five different funds eventually became investors.

Asked why Chinese investors were willing to back Kateeva when funds in the United States and other Asian countries were reluctant, Madigan pointed to a confluence of factors.

The Chinese government had identified OLED displays as a focus of its Five Year Plan. The follow-on economic plan further identified inkjet technology as a critical technology. Investors in China favor companies which can provide the equipment for products, such as OLEDs, which have the government’s blessing and financial support. That government support reduced the investment risks in ways that are not readily seen in Japan or the United States, he said.

Madigan had studied OLEDs as an undergraduate at Princeton University, and then studied under an M.I.T. professor who had developed ink jet technology for large formats.

Though an early goal was to use large-format inkjet to deposit the RGB materials in OLEDs, the Kateeva team learned that its YieldJet system could be adapted to solve a more urgent problem: thin film encapsulation (TFE). It “pivoted” on the advice of an early customer, which fortunately already had developed the “ink” which under UV light would form a uniform encapsulation layer for the large OLED substrates required for TVs and other large display applications.

Two display companies in China identified Kateeva as a strategic partner, which allowed Kateeva to raise money from private Chinese VC funds, rather than taking money from regional government funds which might have asked Kateeva to locate its manufacturing operations in their local area.

Madigan also pointed to the tendency of U.S.-based venture capital funds to favor software companies over manufacturing-focused opportunities. As VCs make money in software-related startups, the funds gradually have more partners and investors which favor software because that is what they are familiar with.

VC fund managers with backgrounds in software “want to invest in the space that they understand. In the United States, that often means software, because you pick companies in the space that you understand.”

LED remains the dominant sapphire application in 2016. Overall, rates of usage in smartwatches have been disappointing and have decreased below 2015 levels. In parallel, smartphone display screen opportunities haven’t taken off. Within the highly competitive sapphire industry, players are chasing any opportunity to survive and optimize their cost structure. Prices seem to have reached bottom and stabilized after a rough ride over the last 12 months. After a dip in the second half of 2015, LED substrate demand has been growing strongly through 2016 and is now at record high levels, even triggering a limited shortage of high-quality 4″ materials and wafers. According to Yole Développement (Yole), the worldwide quarterly sapphire wafer consumption for LEDs has reached 28.5 million of TIE (Q3, 2016).

In its new report, Sapphire Market 2016: Substrates & Consumer Electronics Applications (September 2016, Yole Développement), Yole, the More than Moore market research and strategy consulting company, has analyzed the sapphire industry’s latest technology and market trends. Yole used a dedicated methodology based on both top-to-bottom and bottom-up approaches that included interviews across the entire value chain and a strong knowledge of the industry to review the status and prospects of sapphire technologies for LEDs, camera lenses, and fingerprint reader covers, as well as smartwatch and smartphone displays.

Once again this year, the consulting company collaborated with CIOE to present a powerful program at the International Forum on Sapphire Market & Technologies, 2nd edition (Shenzhen, China – Sept. 6 & 7, 2016 – Agenda). Sapphire industry leaders attended the conference and discussed the latest innovations and market challenges.

What is the status of the sapphire industry? After the 2014 crash, the episode with Apple, and GTAT’s bankruptcy, are there still some survivors? What are their today’s strategies? Beyond existing applications, could we expect emerging applications? Yole’s analysts offer you an overview of the current sapphire industry and announce 2017 trends.

The LED sector still has the highest demand for sapphire. However, Yole’s analysts confirm: the expected volumes cannot sustain the one hundred or so sapphire producers currently competing in the industry. As a consequence, some sapphire companies are leaving the most commoditized markets and shifting their development strategies toward niche markets with higher added-value such as medical, industrial, and military applications. Other business opportunities could materialize, including microLED arrays and other consumer applications. Meanwhile, lower quality production is being dumped on a large grey market serving a multitude of applications including optical, mechanical, industrial, watches, etc.

In Shenzhen, China, at the beginning of September, more than 100 executives gathered and discussed the sapphire industry’s status. With an impressive program including 18 presentations, multiple debates and networking sessions, the sapphire industry’s future was defined and analyzed by sapphire leaders. Yole and its partner CIOE collected good feedback from attendees and are already thinking about a 2017 session.

During this Forum, many relevant and exciting presentations took place, mainly focused on optimizing costs and identifying new markets. Dr. Eric Virey from Yole highlighted the sapphire industry, its latest technical and market trends with a special focus on emerging applications. (See Dr. Eric Virey presentation – 2nd Int. Forum on Sapphire Market & Technologies).

In the same session, leading sapphire manufacturers Monocrystal and Aurora Sapphire also reviewed their insights as key sapphire market players:

•  Mikhail Berest, VP of Sales at Monocrystal, detailed Monocrystal strategies: “The market is challenging not only for sapphire producers, but also for our customers. Our major focus is to strongly support our customers during this market storm by providing them with the highest quality product at a competitive price. We make this possible because Monocrystal’s sapphire is industry-leading due to its low internal stress and low etch pit density. This translates into longer LED lifetime and narrow wavelength distribution on our customers’ side…” (Full discussion on i-micronews, compound semi. news)

•  Xinhong Yang, VP & Technology Director, Aurora Sapphire, presented the latest technology innovations. He also focused his presentation on the future of the sapphire industry.

•  On the application side, Unionlight’s CTO, Huang XiaoWei, discussed military applications of sapphire in the last sapphire Forum session.

Reducing costs and improving quality were major topics discussed at the Forum. Fujian Jing’an Optoelectronics highlighted the importance of subsurface damages. Edouard Brunet, R&D Manager Grains & Powders Asia, Saint-Gobain High Performance Materials, introduced a 1-step polishing process with significant potential for cost reductions. Bernard Jones, VP of Technology & Product Development at Fametec, showed an innovative growth technology for large diameter LED wafers, and Ivan Orlov, Scientific Visual’s CEO, triggered extensive discussions after his presentation on automated ingot inspection and mapping equipment and standardization proposals.

“Once again, the International Forum on Sapphire Market & technologies brought together many players”,comments Jean-Christophe Eloy, President & CEO, Yole Développement. “It showed that in the difficult market environment we’ve experienced since late 2015, the industry needs to gather and exchange information in order to optimize ownership costs and enable new applications.”
Yole & CIOE’s sapphire Forum provided a great platform to stimulate discussion and new ideas with extensive networking opportunities for people and companies to find new partners for the next stage.

“The International Forum on Sapphire Market and Technologies is the key industry event for the main sapphire makers,” asserts Oleg Kachalov, CEO of Monocrystal.“For Monocrystal, it is a chance to meet long-term partners and experts and reach our customers with our new developments, which will allow them to strengthen their position in the LED market.”

“I was impressed by the quality of content presented at Yole & CIOE’s sapphire Forum 2016, which provided not only trend analysis but also deep insights”, says Margaret Connolly, VP of UBM Asia. “The event was well attended by the industry’s key decision makers. The collaboration between CIOE and Yole has been quite successful as the teams are committed to the common objective which is to support long term technology development and innovations. I look forward to attending the 2017 edition in Shenzhen.” UBM owns 100% of eMedia Asia, the majority owner of the annual CIOE.

What can we expect for 2017 and the years after?

Massive adoption of sapphire in display screens now seems unlikely. Many companies have partially or completely exited the industry over the last 12 months. Independent crystal growers in Korea such as DK-Aztek, OCI, and Unid LED have all stopped their sapphire activities. Historical players in Taiwan such as Tera-Xtal, Crystal Applied Technology or Procrystal appear to be on the verge of bankruptcy and U.S. leader Rubicon recently shut down its facility in Malaysia and exited the LED wafer market to refocus on the optical, industrial, and defense markets. But key players are still investing.

So, is there still hope for 2017? To answer that question, both Yole and CIOE are already working on a new sapphire Forum in 2017 in Shenzhen, China. Agenda & registration will be available soon. Stay tuned!

Samsung Electronics Co., Ltd. today announced a new line-up of chip scale package (CSP) LED modules for spotlights and downlights that features color tunability and increased design compatibility.

LED_Image

“Our new CSP LED modules provide an optimal solution for lighting manufacturers who seek highly compatible and reliable LED components,” said Jacob Tarn, Executive Vice President, LED Business Team at Samsung Electronics. “Samsung will continue to strengthen its CSP technology leadership and spearhead new innovations in LED component technology to bring greater value to our customers.”

The new LED modules are Samsung’s first to incorporate CSP technology, which bring a wide range of lighting benefits such as significantly reducing the size of a conventional LED package. The combination of advanced flip chip and phosphor coating technology eliminates metal wires and plastic molds to enable more compact designs when manufacturing LED modules and fixtures.

In addition to their size advantage, Samsung’s new CSP LED modules deliver further characteristics that furnish seamless tunable color. A color-tunable LED module requires twice the number of LED packages in cool and warm temperature, which work in combination on the same board to create a range of tunable colors. In contrast to conventional plastic-molded LED packages that inevitably increase the size of the modules, Samsung’s ultra-compact chip scale LED packages allow the module size to remain unchanged.

Samsung’s new CSP LED modules are available in two form factors (19x19mm or 28x28mm) and are designed following Zhaga specifications, making them highly convenient in assembling. The modules also provide high-quality lighting in diverse beam angle options – spot, medium, wide – for improved compatibility with the optical solutions of Samsung’s partners. The new modules are based on CSP LED packages that have successfully completed 9,000 hours of LM-80 testing, a level of proven performance that reduces the time to market for lighting manufacturers.

Samsung is now sampling six models of the new CSP LED module in CRI 80 and 90 with varying lumen output, size and CCT specifications. The full line-up includes:

 Power

Form Factor 

Model

 Consumption

Lumen

(mm)

CCT
CO10 9.4 1050 lm 19×19 2700/3000/3500/4000K
CO20 18.3 2060 lm 19×19
CO30 27.4 3090 lm 28×28
CO40 36.5 4120 lm 28×28
TO10 9.2-9.8 1060 / 1150 lm 28×28

Color tunable between
2700K~5000K
TO20 17.7-18.4 1970 / 2190 lm 28×28

* Based on CRI 80

Many LED failures are the result of voids or other gap-type anomalies that block heat flow from the die.

BY TOM ADAMS, Sonoscan,Inc., Elk Grove, IL

A few years ago, the only commercial class of LED devices – HB-LEDs – was typically manufactured for applications requiring high reliability. The goal in most applications was to have few field failures, or at least few early-term field failures. Most HB-LED appliances were consequently fairly expensive.

Recently, however, the world of commercial LEDs has split into two parts: High power LEDs, which continue the tradition of reliability and high brightness in appli- cations that require those characteristics, and mid power LEDs, which fill less demanding roles and tend to have lower initial costs. The principle behind mid power LEDS is that consumers will accept a somewhat higher failure rate in appliances having relatively large numbers of LEDs. The gradual loss of light output is balanced by the lower replacement cost.

Recent work has also shed light on the typical mechanisms of failure in both types of LEDs. Most failures in LEDs generally are related to power supply problems, but many failures are the result of voids or other gap-type anomalies that block heat flow from the die. Not surprisingly, there is good correlation between the total voided area beneath the die and the LED’s junction temperature.
Acoustic micro imaging, usually in an automated format, is widely used to ensure LED quality, but with some changes to accommodate the new lower-price market. LEDs can be inspected acoustically in wafer form, as singulated devices before lens placement, and after lens placement by pulsing ultrasound into the heat sink at the bottom of the device (in failure analysis, they may also be inspected by grinding down much of the lens and pulsing ultrasound from above).

The primary change is that singulated mid power LEDs destined for lower-priced applications often need less intensive acoustic inspection. A percentage of such LEDs may be placed in trays and scanned by a system such as one of Sonoscan’s C-SAM® tools, but this done as a non-destructive monitoring step to ensure that large numbers of defective devices are not slipping through rather than as 100% inspection to remove all defective devices. High power LEDs, however, may require 100% acoustic inspection.

The chief structural concerns in both midpower LEDs and high power LEDs are defects that are capable of blocking heat flow from the die. At a much lower power level, the situation is similar to that of IGBT modules, where heat from the die must reach a heat sink below the die to be dissipated. IGBTs generate far more heat than LEDs, but like IGBT modules both LED classes must dissipate heat downward. The lens above the LED is a very poor thermal transmitter.

In some designs the LED may be attached directly to the metal heat sink by a layer of solder. More often there is some type of printed circuit board between the die and the heat sink, with a thermal interface material (solder, grease, epoxy or an adhesive) between the die and the printed circuit board and between the printed circuit board and the heat sink.

Gap-type defects anywhere along the path from the die top the heat sink are the chief targets of acoustic imaging at these depths. A delamination or void as thin as 200Å will reflect virtually all of the ultrasound that strikes it; it is also a very efficient blocker of heat. The various gap-type defects have various somewhat overlapping names: a delamination suggests an interface that was once bonded but was somehow pulled apart; a void suggests a flattened (probably) air bubble; a non-bond suggests two surfaces that should have been bonded but never were, perhaps because of contamination of one of the surfaces. The actual etiology of a gap-type defect may more likely be revealed by knowledge of the processes used in packaging the LED than in observing the defect’s structure.

FIGURE 1 is a high-resolution acoustic image of the solder layer between the substrate and the heat sink of an LED. The transducer of the acoustic microimaging tool traveled back and forth just above this wafer at a speed that can exceed 1 m/s. Each second the transducer repeated its pulse-echo function thousands of times, pulsing ultra- sound into the wafer and receiving the return echoes from material interfaces – homogeneous materials generate no echoes. The amplitude of each echo is recorded, and will determine the pixel color for that x-y location. Most material interfaces are between two solids, reflect roughly 20% to 80% of the ultrasound, and in monochrome images produce dark gray to light gray pixels.

Screen Shot 2017-04-21 at 9.49.46 AM

In the polychromatic color map used here, only in the white areas is the solder bonded to both the substrate and the heat sink. Red regions are not bonded, and thus contain an air gap and reflect virtually all of the ultrasound. More than half of the intended contact area is not bonded, a situation that might be acceptable for a mid power LED, but not for a high power LED. If the non-bonded area grows in size — as they tend to do after thermal cycling — this LED may overheat and fail. If it is a mid power LED assembly, though, the failure of some units may have been anticipated and overall performance may remain within acceptable limits.

When ultrasound and heat encounter the interface between a solid and a void, they react in somewhat different ways. A pulse of ultrasound is almost entirely reflected, with no change in its velocity. Essentially none of the pulse crosses the interface. Heat too is reflected, but also retarded. None of the heat crosses the the gap by conduction, although some heat may cross the gap by convection if the gap is filled with air. If the heat is reflected into a heat-retentive material, that material will heat up.

FIGURE 2 is the acoustic image of a single high power LED from which most of the lens above the die has been ground away to permit a less distorted acoustic view of the die and the die substrate. There is still some distortion caused by the remaining lens material; the die is actually rectangular, for example. But the critical depth – the interface between the lens and the die substrate – is clearly visible. In the color map used here, red indicates the very high reflection from a gap-type defect or delam- ination, in this case the interface between a solid (the lens) and the air in the gap. Like the red regions in Fig. 1, this delamination reflects nearly 100% of the ultra- sound. What this image reveals, then, is that the lens is separated from the substrate by a gap. In itself, this delamination is relatively unimportant as a blocker of heat, because it lies beside and not below the die. But gaps such as this one tend to grow when exposed to thermal cycling; if this gap grows, it is likely to expand under the die and block significant heat. It if grows large enough, it can cause the die to overheat and fail.

Screen Shot 2017-04-21 at 9.49.52 AM

Both high power and mid power LEDs are also imaged acoustically in wafer form in order to find widespread defects as early as possible. FIGURE 3 shows one depth in one region of an HB-LED wafer. The circular or oval white areas formed as follows: at one point in the placing of layers on the wafer, small elongate structures broke free and moved away from their original positions. When the next layer was put down, these structures prevented some points on the layer from reaching the intended depth and thus caused a rounded air-filled void to form. The void is white where there is an interface between the air and the solid layer above. During later handling, smaller particles moved around in the free space of the void until they became trapped under the lower “ceiling” near the edge of the void. These particles form a broken ring around the particle that created the void. They are dark because the interface is between the solid “ceiling” and the solid particle.

Screen Shot 2017-04-21 at 9.49.59 AM

Solid State Technology announced today that its premier semiconductor manufacturing conference and networking event, The ConFab, will be held at the iconic Hotel del Coronado in San Diego on May 14-17, 2017. A 30% increase in attendance in 2016 with a similar uplift expected in 2017, makes the venue an ideal meeting location as The ConFab continues to expand.

    

For more than 12 years, The ConFab, an invitation-only executive conference, has been the destination for key industry influencers and decision-makers to connect and collaborate on critical issues.

“The semiconductor industry is maturing, yet opportunities abound,” said Pete Singer, Editor-in-Chief of Solid State Technology and Conference Chair of The ConFab. “The Internet of Things (IoT) is exploding, which will result in a demand for “things” such as sensors and actuators, as well as cloud computing. 5G is also coming and will be the key technology for access to the cloud.”

The ConFab is the best place to seek a deeper understanding on these and other important issues, offering a unique blend of market insights, technology forecasts and strategic assessments of the challenges and opportunities facing semiconductor manufacturers. “In changing times, it’s critical for people to get together in a relaxed setting, learn what’s new, connect with old friends, make new acquaintances and find new business opportunities,” Singer added.

Dave Mount

David Mount

Solid State Technology is also pleased to announce the addition of David J. Mount to The ConFab team as marketing and business development manager. Mount has a rich history in the semiconductor manufacturing equipment business and will be instrumental in guiding continued growth, and expanding into new high growth areas.

Mainstream semiconductor technology will remain the central focus of The ConFab, and the conference will be expanded with additional speakers, panelists, and VIP attendees that will participate from other fast growing and emerging areas. These include biomedical, automotive, IoT, MEMS, LEDs, displays, thin film batteries, photonics and advanced packaging. From both the device maker and the equipment supplier perspective, The ConFab 2017 is a must-attend networking conference for business leaders.

The ConFab conference program is guided by a stellar Advisory Board, with high level representatives from GLOBALFOUNDRIES, Texas Instruments, TSMC, Cisco, Samsung, Intel, Lam Research, KLA-Tencor, ASE, NVIDIA, the Fab Owners Association and elsewhere.

Details on the invitation-only conference are at: www.theconfab.com. For sponsorship inquiries, contact Kerry Hoffman at [email protected]. For details on attending as a guest or qualifying as a VIP, contact Sally Bixby at [email protected].

By Zvi Or-Bach, President & CEO, MonolithIC 3D Inc.

As we have predicted two and a half years back, the industry is bifurcating, and just a few products pursue scaling to 7nm while the majority of designs stay on 28nm or older nodes.

Our March 2014 blog Moore’s Law has stopped at 28nm has recently been re-confirmed. At the time we wrote: “From this point on we will still be able to double the amount of transistors in a single device but not at lower cost. And, for most applications, the cost will actually go up.” This reconfirmation can be found in the following IBS cost analysis table slide, presented at the early Sept FD-SOI event in Shanghai.

Gate costs continue to rise each generation for FinFETs, IBS predicts.

Gate costs continue to rise each generation for FinFETs, IBS predicts.

As reported by EE Times – Chip Process War Heats Up, and quoting Handel Jones of IBS “28nm node is likely to be the biggest process of all through 2025”.

IBS prediction was seconded by “Samsung executive showed a foil saying it believes 28nm will have the lowest cost per transistor of any node.” The following chart was presented by Samsung at the recent SEMICON West (2016).

Zvi 2

And even Intel has given up on its “every two years” but still claims it can keep reducing transistor cost. Yet Intel’s underwhelming successes as a foundry suggests otherwise. We have discussed it in a blog titled Intel — The Litmus Test, and it was essentially repeated by SemiWiki’s Apple will NEVER use Intel Custom Foundry!

This discussion seems academic now, as the actual engineering costs of devices in advanced nodes have shown themselves to be too expensive for much of the industry. Consequently, and as predicted, the industry is bifurcating, with a few products pursuing scaling to 7nm while the majority of designs use 28nm or older nodes.

The following chart derived from TSMC quarterly earnings reports was published last week by Ed Sperling in the blog Stepping Back From Scaling:

Zvi 3

Yes, the 50-year march of Moore’s Law has ended, and the industry is now facing a new reality.

This is good news for innovation, as a diversity of choices helps support new ideas and new technologies such as 3D NAND, FDSOI, MEMS and others. These technologies will enable new markets and products such as the emerging market of IoT.

A good opportunity to learn more about these new scaling technologies is the IEEE S3S ’16, to be held in the Hyatt Regency San Francisco Airport, October 10th thru 13th, 2016. It starts with 3D and FDSOI tutorials, the emerging technologies for the IC future. CEA Leti is scheduled to give an update on their CoolCube program, Qualcomm will present some of their work on monolithic 3D, and three leading researchers from an imec, MIT, and Korea university collaboration will present their work on advanced monolithic 3D integration technologies. Many other authors will discuss their work on monolithic 3DIC and its ecosystem, in addition to tracks focused on SOI, sub-VT and dedicated sessions on IoT.

“Promising” and “remarkable” are two words U.S. Department of Energy’s Ames Laboratory scientist Javier Vela uses to describe recent research results on organolead mixed-halide perovskites.

Perovskites are optically active, semiconducting compounds that are known to display intriguing electronic, light-emitting and chemical properties. Over the last few years, lead-halide perovskites have become one of the most promising semiconductors for solar cells due to their low cost, easier processability and high power conversion efficiencies. Photovoltaics made of these materials now reach power conversion efficiencies of more than 20 percent.

Vela’s research has focused on mixed-halide perovskites. Halides are simple and abundant, negatively charged compounds, such as iodide, bromide and chloride. Mixed-halide perovskites are of interest over single-halide perovskites for a variety of reasons. Mixed-halide perovskites appear to benefit from enhanced thermal and moisture stability, which makes them degrade less quickly than single-halide perovskites, Vela said. He added they can be fine-tuned to absorb sunlight at specific wavelengths, which makes them useful for tandem solar cells and many other applications, including light emitting diodes (LEDs).Using these compounds, scientists can control the color and efficiency of such energy conversion devices.

Speculating that these enhancements had something to do with the internal structure of mixed-halide perovskites, Vela, who is also an associate professor of chemistry at Iowa State University (ISU), worked with scientists with expertise in solid-state nuclear magnetic resonance (NMR) at both Ames Laboratory and ISU. NMR is an analytical chemistry technique that provides scientists with physical, chemical, structural and electronic information about complex samples.

“Our basic question was what it is about these materials in terms of their chemistry, composition, and structure that can affect their behavior,” said Vela.

Scientists found that depending on how the material is made there can be significant nonstoichiometric impurities or “dopants” permeating the material, which could significantly affect the material’s chemistry, moisture stability and transport properties.

The answers came via the combination of the use of optical absorption spectroscopy, powder X-ray diffraction and for the first time, the advanced probing capabilities of lead solid-state NMR.

“We were only able to see these dopants, along with other semicrystalline impurities, through the use of lead solid-state NMR,” said Vela.

Another major discovery scientists made was that solid state synthesis is far superior to solution-phase synthesis in making mixed-halide perovskites. According to Vela, the advanced spectroscopy and materials capabilities of Ames Laboratory and ISU were critical in understanding how various synthetic procedures affect the true composition, speciation, stability and optoelectronic properties of these materials.

“We found you can make clean mixed halide perovskites without semi-crystalline impurities if you make them in the absence of a solvent,” Vela said.

According to Vela, the significance of their findings is multifold and they are only beginning to grasp the implications of those findings.

“One obvious implication is that our understanding of the amazing opto-electronic properties of these semiconductors was incomplete,” said Vela. “We’re dealing with a compound that is not inherently as simple as people thought.”

The research is further discussed in a paper, “Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites,” authored by Vela, Bryan A. Rosales, Long Men, Sarah D. Cady, Michael P. Hanrahan, and Aaron J. Rossini; and published online in Chemistry Materials. The work was supported by DOE’s Office of Science.

Global growth in the number of “things” connected to the Internet continues to significantly outpace the addition of human users to the World Wide Web. New connections to the “Internet of Things” are now increasing by more than 6x the number of people being added to the “Internet of Humans” each year. Despite the increasing number of connections, IC Insights has trimmed back its semiconductor forecast for Internet of Things system functions over the next four years by about $1.9 billion, mostly because of lower sales projections for connected cities applications (such as smart electric meters and infrastructure). Total IoT semiconductor sales are still expected to rise 19% in 2016 to $18.4 billion, as shown in Figure 1, but the updated forecast first presented in the Update to the 2016 IC Market Drivers Report reduces the market’s compound annual growth rate between 2014 and 2019 to 19.9% compared to the original CAGR of 21.1%. Semiconductor sales for IoT system functions are now expected to reach $29.6 billion in 2019 versus the previous projection of $31.1 billion in the final year of the forecast.

Figure 1

Figure 1

The most significant changes in the new outlook are that semiconductor revenues for connected cities applications are projected to grow by a CAGR of 12.9% between 2014 and 2019 (down from 15.5% in the original forecast) while the connected vehicles segment is expected to rise by a CAGR of 36.7% (up from 31.2% in the previous projection). IoT semiconductor sales for connected cities are now forecast to reach $15.7 billion in 2019 while the chip market for connected vehicle functions is expected to be $1.7 billion in 2019, up from the previous forecast of $1.4 billion.

For 2016, revenues of IoT semiconductors used in connected cities applications are expected to rise 15% to about $11.4 billion while the connected vehicle category is projected to climb 66% to $787 million this year.

Sales of IoT semiconductors for wearable systems have also increased slightly in the forecast period compared to the original projection.  Sales of semiconductors for wearable IoT systems are now expected to grow 22% to about $2.2 billion in 2016 after surging 421% in 2015 to nearly $1.8 billion following Apple’s entry into the smartwatch market in 2Q15.  The semiconductor market for wearable IoT applications is expected to be nearly $3.9 billion in 2019.  Meanwhile, the forecast for IoT semiconductors in connected homes and the Industrial Internet categories remains unchanged.  The connected homes segment is still expected to grow 26% in 2016 to about $545 million, and the Industrial Internet chip market is forecast to increase 22% to nearly $3.5 billion.  The semiconductor forecast for IoT connections in the Industrial Internet is still expected to grow by a CAGR of 25.7% to nearly $7.3 billion in 2019 from $2.3 billion in 2014.