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Standard solutions and devices are compared to a 60 V MOSFET with monolithic Schottky diode as evaluated in SMPS and motor control environments.

BY FILIPPO SCRIMIZZI and FILADELFO FUSILLO, STMicroelectronics, Stradale Primosole 50, Catania, Italy

On synchronous rectification and in bridge configuration, RDSon and Qg are not the only requirements for power MOSFETs. In fact, the dynamic behavior of intrinsic body-drain diode also plays an important role in the overall MOSFET performances. The forward voltage drop (VF,diode) of a body-drain diode impacts the device losses during freewheeling periods (when the device is in off-state and the current flows from source to drain through the intrinsic diode); the reverse recovery charge (Qrr) affects not only the device losses during the reverse recovery process but also the switching behavior, as the voltage spike across the MOSFET increases with Qrr. So, low VFD and Qrr diodes, like Schottky, can improve overall device performance, especially when mounted in bridge topologies or used as synchronous rectifiers—especially at high switching frequency and for long diode conduction times. In this article, we compare standard solutions and devices to a 60 V MOSFET with monolithic Schottky diode as evaluated in SMPS and motor control environments.

Intrinsic MOSFET body-drain diode and Schottky features

In FIGURE 1, the typical symbol for an N-channel Power MOSFET is depicted. The intrinsic body-drain diode is formed by the p-body and n–drift regions and is shown in parallel to the MOSFET channel.

Screen Shot 2016-05-11 at 12.08.52 PM

 

Once a Power MOSFET is selected, the integral body diode is fixed by silicon characteristic and device design. As the intrinsic body diode is paralleled to the device channel, it is important to analyze its static and dynamic behavior, especially in applications where the body diode conducts. So, maximum blocking voltage and forward current have to be considered in reverse and forward bias, while, when the diode turns-off after conducting, it is important to investigate the reverse recovery process (FIGURE 2). When the diode goes from forward to reverse bias, the current doesn’t reduce to zero immediately, as the charge stored during on-state has to be removed. So, at t = t0, the diode commutation process starts, and the current reduces with a constant and slope (-a), fixed only by the external inductances and the supply voltage. The diode is forward biased until t1, while from t1 to t2, the voltage drop across the diode increases, reaching the supply voltage with the maximum reverse current at t=t2. The time interval (t3-t0) is defined as reverse recovery time (trr) while the area between negative current and zero line is the reverse recovery charge (Qrr).The current slope during tB is linked mainly to device design and silicon characteristics.

Screen Shot 2016-05-11 at 12.08.59 PM

The classification of soft and snap recovery is based on the softness factor: Screen Shot 2016-05-11 at 12.09.58 PMthis parameter can be important in many applications. The higher the softness factor, the softer the recovery. In fact, if tB region is very short, the effect of quick current change with the circuit intrinsic inductances can produce undesired voltage overshoot and ringing. This voltage spike could exceed the device breakdown voltage: moreover, EMI performances worsen. As shown in Fig. 2, during diode recovery, high currents and reverse voltage can produce instantaneous power dissipation, reducing the system efficiency. Moreover, in bridge topologies, the maximum reverse recovery current of a Low Side device adds to the High Side current, increasing its power dissipation up to maximum ratings. In switching applications, like bridge topologies, buck converters, or synchronous rectification, body diodes are used as freewheeling elements. In these cases, reverse recovery charge (Qrr) reduction can help maximize system efficiency and limit possible voltage spike and switching noise at turn-off. One strategy to reach this target to integrate a Schottky diode in the MOSFET structure. A Schottky diode is realized by an electrical contact between a thin film of metal and a semiconductor region. As the current is mainly due to majority carriers, Schottky diode has lower stored charge, and consequently, it can be switched from forward to reverse bias faster than a silicon device. An additional advantage is its lower forward voltage drop (≈0.3 V) than Si diodes, meaning that a Schottky diode has lower losses during the on state.

Embedding the Schottky diode in a 60V power MOSFET is the right device choice when Qrr and VF,diode have to be optimized to enhance the overall system performance. In FIGURE 3, the main electrical parameters of standard and integrated Schottky devices (same BVDSS and die size) are reported.

Screen Shot 2016-05-11 at 12.09.06 PM

Benefits of Mono Schottky in a power management environment

In a synchronous buck converter (FIGURE 4), a power MOSFET with integrated Schottky diode can be mounted as a Low Side device (S2) to enhance the overall converter performance.

Screen Shot 2016-05-11 at 12.09.13 PM

In fact, Low Side body diode conduction losses (Pdiode,cond) and reverse recovery losses (PQrr) are strictly related to the diode forward voltage drop (VF,diode) and its reverse recovery charge (Qrr):

Screen Shot 2016-05-11 at 12.09.20 PM

As shown in (1) and (2), these losses increase with the switching frequency, the converter input voltage, and the output current. Moreover, the dead time, when both FETs are off and the current flows in the Low Side body diode, seriously affects the diode conduction losses: with long dead times, a low diode forward voltage drop helps to minimize its conduction losses, therefore increasing the efficiency. In FIGURE 5, the efficiency in a 60W, 48V – 12V, 250 kHz synchronous buck converter is depicted.

Screen Shot 2016-05-11 at 12.09.26 PM

Now, considering isolated power converters’ environment, when the output power increases and the dead time values are high, the right secondary side synchronous rectifier should have not only RDSon as low as possible to reduce conduction losses, but also optimized body diode behavior (in terms of Qrr and VF,diode) in order to reduce diode losses (as reported in (1) and (2)) and to minimize possible voltage spikes during turn-off transient. The 60V standard MOSFET and one with Schottky integrated devices are compared in a 500W digital power supply, formed by two power stages: power factor corrector and an LLC with synchronous rectification. The maximum output current is 42 A, while the switching frequency at full load is 80 kHz, and the dead time is 1μs. The efficiency curves are compared in FIGURE 6.

Screen Shot 2016-05-11 at 12.09.32 PM

In both topologies, the 60 V plus Schottky device shows higher efficiency in the entire current range, an improvement in overall system performance.

Switching behavior improvement in bridge topologies

In bridge topologies, reverse recovery process occurs at the end of the freewheeling period of the Low Side device (Q2 in FIGURE 7), before the High Side (Q1 in Fig. 7) starts conducting. The resulting recovery current adds to the High Side current (as previously explained). Together with the extra-current on the High Side device, the Low Side reverse recovery and its commutation from Vds ≈ 0 V to Vdc can produce spurious bouncing on the Low Side gate- source voltage, due to induced charging of Low Side Ciss (input capacitance) via Crss (Miller capacitance).

Screen Shot 2016-05-11 at 12.09.38 PM

As a consequence, the induced voltage on Q2 gate could turn-on the device, worsening system robustness and efficiency. A Low Side device, in bridge configuration, should have soft commutation, without dangerous voltage spikes and high frequency ringing across drain and source. This switching behavior can be achieved using power MOSFETs with integrated Schottky diode as Low Side devices. In fact, the lower reverse recovery charge (Qrr) has a direct impact on the overshoot value. In fact, the higher the Qrr, the higher the overshoot. Lower values for Vds overshoot and ringing reduce the spurious voltage bouncing on the Low Side gate, limiting the potential risk for a shoot-through event. Furthermore, soft recovery enhances overall EMI performances, as the switching noise is reduced. In FIGURE 8 are shown the High Side turn-on waveforms for standard and embedded Schottky devices; purple trace (left graph) and green trace (right graph) are Low Side gate-source voltages. The device with Schottky diode shows a strong reduction of Low Side spurious bouncing.

Screen Shot 2016-05-11 at 12.09.47 PM

Summary

In many applications (synchronous rectification for indus- trial and telecom SMPS, DC-AC inverter, motor drives), choosing the right MOSFET means not only considering RDSon and Qg but also evaluating the static and dynamic behavior of the intrinsic body-drain diode. A 60V “F7” power MOSFET with integrated Schottky diode ensures optimized performances in efficiency and commutation when a soft reverse recovery with low Qrr is required. Furthermore, the low VF,diode value achieves higher efficiency when long freewheeling periods or dead-times are present in the application.

References

1. “Fundamental of Power Semiconductor Devices”, B.J.Baliga – 2008, Springer Science

Worldwide semiconductor capital spending is projected to decline 2 percent in 2016, to $62.8 billion, according to Gartner, Inc. (see Table 1). This is up from the estimated 4.7 percent decline in Gartner’s previous quarterly forecast.

“While the first quarter 2016 forecast has improved from a projected decline of 4.7 percent in the previous quarter’s forecast, the 2 percent decline in the market for 2016 is still bleak,” said David Christensen, senior research analyst at Gartner. “Excess inventory and weak demand for PCs, tablets, and mobile products continue to plague the semiconductor industry, resulting in a slow growth rate that began in late 2015 and is continuing into 2016.”

Table 1

Worldwide Semiconductor Capital Spending and Equipment Spending Forecast, 2015-2018 (Millions of Dollars)

2015

2016

2017

2018

Semiconductor Capital Spending ($M)

64,062.9

62,795.3

65,528.5

70,009.5

Growth (%)

-0.8

-2.0

4.4

6.8

Wafer-Level Manufacturing Equipment ($M)

33,248.1

32,642.0

34,897.6

37,641.1

Growth (%)

-1.1

-1.8

6.9

7.9

Wafer Fab Equipment ($M)

31,485.4

30,841.9

32,930.3

35,443.4

Growth (%)

-1.3

-2.0

6.8

7.6

Wafer-Level Packaging and Assembly Equipment ($M)

1,762.7

1,800.2

1,967.3

2,197.7

Growth (%)

4.1

2.1

9.3

11.7

Source: Gartner (May 2016)

“The slowdown in the devices market has driven semiconductor producers to be conservative with their capital spending plans,” said Mr. Christensen. “This year, leading semiconductor manufacturers are responding to anticipated weak demand from semiconductors and preparing for new growth in leading-edge technologies in 2017.”

In addition, the aggressive pursuit of semiconductor manufacturing capability by the Chinese government is an issue that cannot be ignored by the semiconductor manufacturing industry. In the last year, there has been consolidation and merger and acquisition (M&A) activity with specific offers from various Chinese-based entities, indicating the aggressiveness of the Chinese. This will dramatically affect the competitive landscape of global semiconductor manufacturing in the next few years, as China is now a major market for semiconductor usage and manufacturing.

Looking forward, the market is expected to return to growth in 2017. Increased demand for 10 nanometer (nm) and 3D NAND process development in memory and logic/foundry will drive overall spending to grow 4.4 percent in 2017.

This research is produced by Gartner’s Semiconductor Manufacturing program. This research program, which is part of the overall semiconductor research group, provides a comprehensive view of the entire semiconductor industry, from manufacturing to device and application market trends. Additional analysis on the outlook for the semiconductor market can be found at “Forecast Analysis: Capital Spending and Semiconductor Manufacturing Equipment, Worldwide, 1Q16.”

By Lara Chamness, Industry Research and Statistics, SEMI

North America has a long and rich history of semiconductor manufacturing and innovation. As home to device manufacturers such as Intel, Texas Instruments, Micron, GLOBALFOUNDRIES, NXP (Freescale), Fairchild, Avago, Qorvo, Microchip, ON Semiconductor, significant operations of Samsung, and leading fabless companies such as Qualcomm, Broadcom, NVIDIA, AMD, Apple, Marvell, and Xilinx, North America continues to play an important role in advanced semiconductor manufacturing and in device and system design. SEMI’s Fab Forecast shows that North America accounts for 14 percent of Worldwide Installed Fab capacity (excluding discretes).

Source: SEMI (www.semi.org)

In terms of revenues, IC Insights recently announced, that companies headquartered in the United States continue to capture the bulk of IDM and Fabless IC Sales.

  • U.S. companies account for 51 percent of IDM Companies IC Sales in 2015
  • U.S. companies account for 62 percent of Fabless Companies IC Sales in 2015

Due to the presence of leading device manufacturers, North America represents a significant portion of the new equipment market, annual spending on average over the past five years has been in excess of $7 billion. Spending for new equipment is expected to be approach $6 billion this year.

Source: SEMI/SEAJ; Forecast, SEMI (www.semi.org)

With such a large installed fab base, North America also claims a significant portion of the wafer fab materials market.  Comparing global fab capacity to global wafer fab market share, North America represents 18 percent of the Wafer Fab Materials market compared to 14 percent of global fab capacity. This is due to the advanced device manufacturing that occurs in the region, which requires more process steps and advanced materials which fetch higher average selling prices.

Regional Wafer Fab Materials Markets

Source: SEMI (www.semi.org)

The equipment market is expected to increase about 10 percent in North America this year due to sizable investments by GLOBALFOUNDRIES, Intel and Samsung, while the Wafer Fab Materials Market is expected to remain flat this year relative to last year. As companies like Apple, Intel, Qualcomm continue to innovate, North America will remain an essential force in both device and systems design and in semiconductor manufacturing.

Plan to attend the SEMI/Gartner Market Symposium at SEMICON West 2016 on Monday, July 11, for an update on the semiconductor market outlook.

LED Taiwan, the most influential LED exhibition in Taiwan, is organized by SEMI and the Taiwan External Trade Development Council (TAITRA). Opening at TWTC Nangang Exhibition Hall in Taipei on April 13-16, the four-day event features theme pavilions, industry forums, TechSTAGE and academic paper presentations. The Taiwan International Lighting Show (TiLS) is co-located. With 748 booths and 238 exhibitors demonstrating the local LED supply chains’ R&D capabilities, LED Taiwan is expected to attract over 16,000 visitors from Taiwan and internationally.

Research firm Strategies Unlimited estimates that the global LED packaging market had US$15.6 billion revenue in 2014. The market is expected to grow to US$22 billion by 2019, 45 percent from lighting applications. However, as the price of white LEDs continues to fall, new applications are regarded as the key to higher earnings. Prospects of niche-market applications like IR LED and UV LED look good, while automotive LED lights are becoming another important market with greater demand for high-power chips.

Five theme pavilions to fully demonstrate a complete LED industry chain

To satisfy the market’s demand for LED in an era of IoT, LED Taiwan 2016 will add three new pavilions — LED Components, Smart Lighting Technology, and Power Device — to the two existing pavilions High-Brightness LED and Sapphire. Leading players in the areas of LED equipment, materials, components and packaging ─ like Aurora Optoelectronics, Cree, Epileds, GlobalWafers, Han’s Laser, Lextar, an alliance of sapphire processing companies organized by the Metal Industries Research & Development Centre, Rapitech, Rubicon and Wei Min Industrial ─ will all showcase their products in the exhibition to help local and foreign visitors understand the structure, manufacturing processes and technologies of Taiwan’s LED industry.

Event to feature the results of innovation in five areas

To enable innovation and bring more energy to the local LED industry, TechSTAGE will be held as part of this year’s LED Taiwan event, showcasing Taiwan’s LED R&D capability in the areas of LED

Manufacturing Equipment & Materials, Power Device Technology, Sapphire Processing Technology & Application, LED Advanced Technologies, and Smart Lighting & Automobile Lighting.

Seeking more possibilities with innovative materials and power devices

As awareness about energy conservation increases around the world and the market seeks better profits and opportunities, more companies are investing in power device R&D and production. This has prompted LED Taiwan to focus on the hot topic of power devices this year, and in addition to a special pavilion for the segment, the event will also organize a forum for vendors to discuss and understand trends and development concerning this technology.

International forums to explore key issues in the industry

As the LED market is gradually maturing, companies in the industry are aggressively seeking new applications and “blue ocean” strategies. In addition to visible LED applications in back-lit display, mobile phones, lighting equipment and cars, more companies have invested in the development and production of invisible LEDs. While demand continues to diversify with a focus on custom-made applications, the ability to find new opportunities in this trend, improving competitiveness and innovation, will be the key to future success. The LED Taiwan 2016 Executive Summit will discuss future trends by exploring innovation, LED lighting/non-lighting opportunities, current challenges and strategies in the market. The IR and UV Summit will focus on IR and UV LED applications in wearable devices, medical appliances and measuring equipment in a bid to help participants get a quick grasp of latest trends around the world.

Integration of resources helps boost local LED industry’s global presence

LED Taiwan is made possible with the collaboration and resources from influential organizations in the industry, including SEMI, TAITRA, the Taiwan Lighting Fixture Export Association and the Taiwan Optoelectronic Semiconductor Industry Association. Each year, foreign buyers and leading manufacturers are invited to the exposition where various business matching events, VIP luncheons and banquet meetings are arranged to help Taiwan vendors expand connections and secure business opportunities by interacting with the elite members of foreign industrial and academic circles.

“SEMI has many connections and resources in the area of LED manufacturing, and by working with the Taiwan Lighting Fixture Export Association and TAITRA, we are able to organize LED Taiwan and TiLS at the same time, ” said Terry Tsao, president of SEMI Taiwan. “In addition to showing the world the robust ecosystem of Taiwan’s LED industry and attracting more foreign buyers, we also hope that innovative technologies and academic papers announced in the forums will help integrate industrial and academic resources. We want to create more opportunities for the LED industry and make Taiwan’s outstanding R&D capabilities visible to the world.”

LED Taiwan is the most influential LED exposition in Taiwan, showcasing LED production equipment & materials, epi wafers, crystals, packaging, modules, etc., as well as related technologies and manufacturing solutions. The Taiwan International Lighting Show is co-located at LED Taiwan as a multi-purpose event facilitating technology exchanges and procurement in the areas of LED and lighting. LED Taiwan was inaugurated in 2010, and in 2015, the event attracted buyers from over 68 countries and created more than US$13 million of business.

For more information on LED Taiwan, please visit: www.ledtaiwan.org/en/

Becoming crystal clear


April 6, 2016

Using state-of-the-art theoretical methods, UCSB researchers have identified a specific type of defect in the atomic structure of a light-emitting diode (LED) that results in less efficient performance. The characterization of these point defects could result in the fabrication of even more efficient, longer lasting LED lighting.

“Techniques are available to assess whether such defects are present in the LED materials and they can be used to improve the quality of the material,” said materials professor Chris Van de Walle, whose research group carried out the work.

In the world of high-efficiency solid-state lighting, not all LEDs are alike. As the technology is utilized in a more diverse array of applications — including search and rescue, water purification and safety illumination, in addition to their many residential, industrial and decorative uses — reliability and efficiency are top priorities. Performance, in turn, is heavily reliant on the quality of the semiconductor material at the atomic level.

“In an LED, electrons are injected from one side, holes from the other,” explained Van de Walle. As they travel across the crystal lattice of the semiconductor — in this case gallium-nitride-based material — the meeting of electrons and holes (the absence of electrons) is what is responsible for the light that is emitted by the diode: As electron meets hole, it transitions to a lower state of energy, releasing a photon along the way.

Occasionally, however, the charge carriers meet and do not emit light, resulting in the so-called Shockley-Read-Hall (SRH) recombination. According to the researchers, the charge carriers are captured at defects in the lattice where they combine, but without emitting light.

The defects identified involve complexes of gallium vacancies with oxygen and hydrogen. “These defects had been previously observed in nitride semiconductors, but until now, their detrimental effects were not understood,” explained lead author Cyrus Dreyer, who performed many of the calculations on the paper.

“It was the combination of the intuition that we have developed over many years of studying point defects with these new theoretical capabilities that enabled this breakthrough,” said Van de Walle, who credits co-author Audrius Alkauskas with the development of a theoretical formalism necessary to calculate the rate at which defects capture electrons and holes.

The method lends itself to future work identifying other defects and mechanisms by which SRH recombination occurs, said Van de Walle.

“These gallium vacancy complexes are surely not the only defects that are detrimental,” he said. “Now that we have the methodology in place, we are actively investigating other potential defects to assess their impact on nonradiative recombination.”

Gartner, Inc. has highlighted the top 10 Internet of Things (IoT) technologies that should be on every organization’s radar through the next two years.

“The IoT demands an extensive range of new technologies and skills that many organizations have yet to master,” said Nick Jones, vice president and distinguished analyst at Gartner. “A recurring theme in the IoT space is the immaturity of technologies and services and of the vendors providing them. Architecting for this immaturity and managing the risk it creates will be a key challenge for organizations exploiting the IoT. In many technology areas, lack of skills will also pose significant challenges.”

The technologies and principles of IoT will have a very broad impact on organizations, affecting business strategy, risk management and a wide range of technical areas such as architecture and network design. The top 10 IoT technologies for 2017 and 2018 are:

IoT Security

The IoT introduces a wide range of new security risks and challenges to the IoT devices themselves, their platforms and operating systems, their communications, and even the systems to which they’re connected. Security technologies will be required to protect IoT devices and platforms from both information attacks and physical tampering, to encrypt their communications, and to address new challenges such as impersonating “things” or denial-of-sleep attacks that drain batteries. IoT security will be complicated by the fact that many “things” use simple processors and operating systems that may not support sophisticated security approaches.

“Experienced IoT security specialists are scarce, and security solutions are currently fragmented and involve multiple vendors,” said Mr. Jones. “New threats will emerge through 2021 as hackers find new ways to attack IoT devices and protocols, so long-lived “things” may need updatable hardware and software to adapt during their life span.”

IoT Analytics

IoT business models will exploit the information collected by “things” in many ways — for example, to understand customer behavior, to deliver services, to improve products, and to identify and intercept business moments. However, IoT demands new analytic approaches. New analytic tools and algorithms are needed now, but as data volumes increase through 2021, the needs of the IoT may diverge further from traditional analytics.

IoT Device (Thing) Management

Long-lived nontrivial “things” will require management and monitoring. This includes device monitoring, firmware and software updates, diagnostics, crash analysis and reporting, physical management, and security management. The IoT also brings new problems of scale to the management task. Tools must be capable of managing and monitoring thousands and perhaps even millions of devices.

Low-Power, Short-Range IoT Networks

Selecting a wireless network for an IoT device involves balancing many conflicting requirements, such as range, battery life, bandwidth, density, endpoint cost and operational cost. Low-power, short-range networks will dominate wireless IoT connectivity through 2025, far outnumbering connections using wide-area IoT networks. However, commercial and technical trade-offs mean that many solutions will coexist, with no single dominant winner and clusters emerging around certain technologies, applications and vendor ecosystems.

Low-Power, Wide-Area Networks

Traditional cellular networks don’t deliver a good combination of technical features and operational cost for those IoT applications that need wide-area coverage combined with relatively low bandwidth, good battery life, low hardware and operating cost, and high connection density. The long-term goal of a wide-area IoT network is to deliver data rates from hundreds of bits per second (bps) to tens of kilobits per second (kbps) with nationwide coverage, a battery life of up to 10 years, an endpoint hardware cost of around $5, and support for hundreds of thousands of devices connected to a base station or its equivalent. The first low-power wide-area networks (LPWANs) were based on proprietary technologies, but in the long term emerging standards such as Narrowband IoT (NB-IoT) will likely dominate this space.

IoT Processors

The processors and architectures used by IoT devices define many of their capabilities, such as whether they are capable of strong security and encryption, power consumption, whether they are sophisticated enough to support an operating system, updatable firmware, and embedded device management agents. As with all hardware design, there are complex trade-offs between features, hardware cost, software cost, software upgradability and so on. As a result, understanding the implications of processor choices will demand deep technical skills.

IoT Operating Systems

Traditional operating systems (OSs) such as Windows and iOS were not designed for IoT applications. They consume too much power, need fast processors, and in some cases, lack features such as guaranteed real-time response. They also have too large a memory footprint for small devices and may not support the chips that IoT developers use. Consequently, a wide range of IoT-specific operating systems has been developed to suit many different hardware footprints and feature needs.

Event Stream Processing

Some IoT applications will generate extremely high data rates that must be analyzed in real time. Systems creating tens of thousands of events per second are common, and millions of events per second can occur in some telecom and telemetry situations. To address such requirements, distributed stream computing platforms (DSCPs) have emerged. They typically use parallel architectures to process very high-rate data streams to perform tasks such as real-time analytics and pattern identification.

IoT Platforms

IoT platforms bundle many of the infrastructure components of an IoT system into a single product. The services provided by such platforms fall into three main categories: (1) low-level device control and operations such as communications, device monitoring and management, security, and firmware updates; (2) IoT data acquisition, transformation and management; and (3) IoT application development, including event-driven logic, application programming, visualization, analytics and adapters to connect to enterprise systems.

IoT Standards and Ecosystems

Although ecosystems and standards aren’t precisely technologies, most eventually materialize as application programming interfaces (APIs). Standards and their associated APIs will be essential because IoT devices will need to interoperate and communicate, and many IoT business models will rely on sharing data between multiple devices and organizations.

Many IoT ecosystems will emerge, and commercial and technical battles between these ecosystems will dominate areas such as the smart home, the smart city and healthcare. Organizations creating products may have to develop variants to support multiple standards or ecosystems and be prepared to update products during their life span as the standards evolve and new standards and related APIs emerge.

More detailed analysis is available for Gartner clients in the report “Top 10 IoT Technologies for 2017 and 2018.” This report is part of the Gartner Special Report “The Internet of Things“, which looks at the necessary steps to building and rolling out an IoT strategy.

With just a tiny tweak, researchers at Kyushu University greatly increased the device lifetime of organic light-emitting diodes (OLEDs) that use a recently developed class of molecules to convert electricity into light with the potential for increased efficiency at a lower cost in future displays and lighting.

Using the OLED structure in this schematic, researchers were able to delay the degradation in brightness of an OLED with the TADF emitter 4CzIPN by eight to sixteen times. Credit: Daniel Ping-Kuen Tsang and William John Potscavage Jr.

Using the OLED structure in this schematic, researchers were able to delay the degradation in brightness of an OLED with the TADF emitter 4CzIPN by eight to sixteen times. Credit: Daniel Ping-Kuen Tsang and William John Potscavage Jr.

The easily implemented modifications can also potentially increase the lifetime of OLEDs currently used in smartphone displays and large-screen televisions.

Typical OLEDs consist of multiple layers of organic films with various functions. At the core of an OLED is an organic molecule that emits light when a negatively charged electron and a positively charged hole, which can be thought of as a missing electron, meet on the molecule.

Until recently, the light-emitting molecules were either fluorescent materials, which can be low cost but can only use about 25% of electrical charges, or phosphorescent materials, which can harvest 100% of charges but include an expensive metal such as platinum or iridium.

Researchers at Kyushu University’s Center for Organic Photonic and Electronics Research (OPERA) changed this in 2012 with the demonstration of efficient emitters based on a process called thermally activated delayed fluorescence (TADF).

Through clever molecular design, these TADF materials can convert nearly all of the electrical charges to light without the expensive metal used in phosphorescent materials, making both high efficiency and low cost possible.

However, OLEDs under constant operation degrade and become dimmer over time regardless of the emitting material.

Devices that degrade slowly are key for practical applications, and concerns remained that the lifetime of early TADF devices was still on the short side.

But with the leap in lifetime reported in a paper published online March 1, 2016, in Scientific Reports, many of those concerns can now be put to rest.

“While our initial TADF devices lost 5% of their brightness after only 85 hours,” said postdoctoral researcher Daniel Tsang, lead author on the study, “we have now extended that more than eight times just by making a simple modification to the device structure.”

The newly developed modification was to put two extremely thin (1-3 nm) layers of the lithium-containing molecule Liq on each side of the hole blocking layer, which brings electrons to the TADF material, the green emitter 4CzIPN in this case, while preventing holes from exiting the device before contributing to emission.

The devices will last even longer in practical applications because the tests are performed at extreme brightnesses to accelerate the degradation.

Applying additional optimizations that have been previously reported, the 5% drop was further delayed to longer than 1,300 hours, over 16 times that of the initial devices.

“What we are finding is that the TADF materials themselves can be very stable, making them really promising for future displays and lighting,” said Professor Chihaya Adachi, director of OPERA.

The benefits of the Liq layers are not limited to TADF-based OLEDs as the researchers also found an improvement using a similar device structure with a phosphorescent emitter.

Though still trying to completely unravel the degradation mechanism, the researchers found that devices with the Liq layers contain a much lower number of traps, a type of defect that can capture and hold a charge, preventing it from moving freely in the device.

These defects were observed by measuring tiny electrical currents created when charges that were frozen in the traps at extremely cold temperatures escape by receiving a jolt of thermal energy as the device is heated, a process called thermally stimulated current.

Having charges stuck in these traps may increase the chance for interactions with other charges and electrical excitations that can destroy the molecules and lead to degradation.

One of the next major challenges for TADF is stable and efficient blue emitting materials, which are necessary for full color displays and are also still difficult using phosphorescence.

“With the continued development of new materials and device structures,” said Prof. Adachi, “we think that TADF has the potential to solve the challenge of efficient and stable blue emission.”

Worldwide silicon wafer area shipments increased 3 percent in 2015 when compared to 2014 area shipments according to the SEMI Silicon Manufacturers Group (SMG) in its year-end analysis of the silicon wafer industry. However, worldwide silicon revenues decreased by 6 percent in 2015 compared to 2014.

Silicon wafer area shipments in 2015 totaled 10,434 million square inches (MSI), up from the previous market high of 10,098 million square inches shipped during 2014. Revenues totaled $7.2 billion down from $7.6 billion posted in 2014. “Semiconductor silicon shipment levels remained strong throughout most of the year, resulting in record volume shipments,” said Dr. Volker Braetsch, chairman SEMI SMG and senior vice oresident of Siltronic AG. “The strength in shipments was not enough to compensate headwinds from further price decline and some exchange rate impact; silicon revenues for the year decreased yet again and are significantly below their market high set in 2007.”

Annual Silicon* Industry Trends

2007

2008

2009

2010

2011

2012

2013

2014

2015
Area Shipments (MSI)

8,661

8,137

6,707

9,370

9,043

9,031

9,067

10,098

10,434
Revenues ($B)

12.1

11.4

6.7

9.7

9.9

8.7

7.5

7.6

7.2

*Shipments are for semiconductor applications only and do not include solar applications

Silicon wafers are the fundamental building material for semiconductors, which in turn, are vital components of virtually all electronics goods, including computers, telecommunications products, and consumer electronics. The highly engineered thin round disks are produced in various diameters (from one inch to 12 inches) and serve as the substrate material on which most semiconductor devices or “chips” are fabricated.

All data cited in this release is inclusive of polished silicon wafers, including virgin test wafers and epitaxial silicon wafers, as well as non-polished silicon wafers shipped by the wafer manufacturers to the end-users.

The Silicon Manufacturers Group acts as an independent special interest group within SEMI and is open to SEMI members involved in manufacturing polycrystalline silicon, monocrystalline silicon or silicon wafers (e.g., as cut, polished, epi, etc.). The purpose of the group is to facilitate collective efforts on issues related to the silicon industry including the development of market information and statistics about the silicon industry and the semiconductor market.

The health of the IC industry is increasingly tied to the health of the worldwide economy. Rarely can there be strong IC market growth without at least a “good” worldwide economy to support it. Consequently, IC Insights expects annual global IC market growth rates to closely track the performance of worldwide GDP growth. In the recently released The McClean Report 2016, IC Insights forecasts 2.7% global GDP growth for 2016, only marginally ahead of what is considered to be the recession threshold of 2.5% growth.

Figure 1 puts the worldwide electronics and semiconductor industries into perspective. The top figure, worldwide GDP, represents all global economic activity. Essentially, the worldwide total available market (TAM) for business (i.e., GDP) was $78.4 trillion in 2015.

In many areas of the world, local economies have slowed. For example, economic growth in China slipped below 7% in 2015. China, which is the leading market for personal computers, digital TVs, smartphones, new commercial aircraft, and automobiles, is forecast to lose more economic momentum in 2016. Its GDP is forecast to increase 6.3% in 2016, which continues a slide in that country’s annual GDP growth rate that started in 2010.

While the U.S. economy is far from perfect, it is currently one of the most significant positive driving forces in the worldwide economy. The U.S. accounted for 22% of worldwide GDP in 2015. U.S. GDP is forecast to grow 2.5% in 2016. Given its size and strength, the U.S. economy greatly influences overall global GDP growth. An improving employment picture and the low price of oil are factors that should positively impact the U.S. economy in 2016.

Other noteworthy industry highlights from the 2016 edition of The McClean Report include the following:

• Global semiconductor sales decreased 1% in 2015 but are forecast to grow 4% in 2016. IC Insights expects the worldwide IC market to increase 4% in 2016, and sales of optoelectronics, sensors, and discrete (OSD) devices collectively to register 5% growth.

Figure 1

Figure 1

• Total semiconductor unit shipments (including IC and OSD devices) reached almost 840-billion units in 2015 and are expected to exceed one trillion units in 2018. After increasing 4% in 2015, IC unit shipments are forecast to grow 5% in 2016. Analog devices are forecast to account for 53% of total IC unit shipments in 2016.

• A stable IC pricing environment is expected through 2020 due in part to fewer suppliers in various IC markets (i.e., DRAM, MPU, etc.), lower capital spending as a percent of sales, and no significant new IC manufacturers entering the market in the future (the surge of Chinese IC companies that entered the market in the early 2000’s is assumed to be the last large group of newcomers.

• Semiconductor industry capital spending grew to $65.9 billion in 2015. IC Insights forecasts semiconductor capital spending will decrease 1% in 2016. Spending on flash memory and within the foundry segment is forecast to increase in 2016 but spending for all other market segments, including DRAM, is expected to decline. Semiconductor capital spending as a percent of sales is forecast to remain in the mid- to high-teens range through 2020. IC Insights believes spending at this level will not lead to an industry-wide overcapacity during the forecast period.

• Semiconductor R&D spending increased 1% in 2015 to new record high of $56.4 billion. Intel dedicated $12.1 billion to R&D in 2015 (24.0% of sales) to remain the largest semiconductor R&D spender in 2015. R&D spending at TSMC, the industry’s biggest pure-play foundry rose 10% in 2015, ranking it 5th among top R&D spenders. TSMC joined the group of top-10 R&D spenders for the first time in 2010, giving an indication of just how important TSMC and other pure-play foundries have become to the IC industry with continuing technological progress.

Further trends and analysis relating to the IC market are covered in the main 400-plus page 2016 edition of The McClean Report.

The Semiconductor Industry Association (SIA) today announced the global semiconductor industry posted sales totaling $335.2 billion in 2015, a slight decrease of 0.2 percent compared to the 2014 total, which was the industry’s highest-ever sales total. Global sales for the month of December 2015 reached $27.6 billion, down 4.4 percent compared to the previous month and 5.2 percent lower than sales from December 2014. Fourth quarter sales of $82.9 billion were 5.2 percent lower than the total of $87.4 billionfrom the fourth quarter of 2014. All monthly sales numbers are compiled by the World Semiconductor Trade Statistics (WSTS) organization and represent a three-month moving average.

“Despite formidable headwinds, the global semiconductor industry posted solid sales in 2015, although falling just short of the record total from 2014,” said John Neuffer, president and CEO, Semiconductor Industry Association. “Factors that limited more robust sales in 2015 include softening demand, the strength of the dollar, and normal market trends and cyclicality. In spite of these challenges, modest market growth is projected for 2016.”

Several semiconductor product segments stood out in 2015. Logic was the largest semiconductor category by sales with $90.8 billionin 2015, or 27 percent of the total semiconductor market. Memory ($77.2 billion) and micro-ICs ($61.3 billion) – a category that includes microprocessors – rounded out the top three segments in terms of total sales. Optoelectronics was the fastest growing segment, increasing 11.3 percent in 2015. Other product segments that posted increased sales in 2015 include sensors and actuators, which reached $8.8 billion in sales for a 3.7 percent annual increase, NAND flash memory ($28.8 billion/2.2 percent increase), and analog ($45.2 billion/1.9 percent increase).

Regionally, annual sales increased 7.7 percent in China, leading all regional markets. All other regional markets – the Americas (-0.8 percent), Europe (-8.5 percent), Japan (-10.7 percent), and Asia Pacific/All Other (-0.2 percent) – saw decreased sales compared to 2014.

“The semiconductor industry is critically important to the U.S. economy and our global competitiveness,” continued Neuffer. “We urge Congress to enact polices in 2016 that promote innovation and growth. One such initiative is the Trans-Pacific Partnership (TPP), a landmark agreement that would tear down myriad barriers to trade with countries in the Asia-Pacific. The TPP is good for the semiconductor industry, the tech sector, the American economy, and the global economy. Congress should approve it.”

December 2015

Billions

Month-to-Month Sales                               

Market

Last Month

Current Month

% Change

Americas

6.07

5.75

-5.2%

Europe

2.93

2.77

-5.7%

Japan

2.68

2.57

-4.1%

China

8.67

8.45

-2.5%

Asia Pacific/All Other

8.53

8.08

-5.3%

Total

28.88

27.62

-4.4%

Year-to-Year Sales                          

Market

Last Year

Current Month

% Change

Americas

6.73

5.75

-14.5%

Europe

3.01

2.77

-7.9%

Japan

2.80

2.57

-8.1%

China

8.03

8.45

5.2%

Asia Pacific/All Other

8.57

8.08

-5.7%

Total

29.13

27.62

-5.2%

Three-Month-Moving Average Sales

Market

Jul/Aug/Sep

Oct/Nov/Dec

% Change

Americas

5.82

5.75

-1.2%

Europe

2.87

2.77

-3.6%

Japan

2.69

2.57

-4.3%

China

8.45

8.45

0.0%

Asia Pacific/All Other

8.58

8.08

-5.8%

Total

28.41

27.62

-2.8%