Query: Packaging SiC power semiconductors—Challenges, technologies and strategies

Candidate papers:

abstract: In this paper a comprehensive review on SiC power module challenges and technology approaches is given. These challenges originate from SiC specific reduced chip area, from high power and high loss density operation, from high temperature capability, from fast switching transients and from high electric field operation. New approaches based on advanced integrated cooling, low profile integrated topside bonding and low inductance architectures are outlined and discussed.
author_names: Jurgen Schuderer

Umamaheswara Vemulapati

Felix Traub
title: Packaging SiC power semiconductors Challenges, technologies and strategies
venue: 2014 IEEE Workshop on Wide Bandgap Power Devices and Applications
year: 2014

abstract: This paper reports on the fabrication technology and packaging strategy for 300V 5A Silicon Carbide Schottky diodes with a wide temperature operation range capability (between 170oC and 300oC) These diodes have been designed for harsh environment space applications such as inner Solar System exploration probes. More specifically these diodes are being tested to be the blocking diodes of the solar panels for the Bepi Colombo mission. Different endurance tests have been performed to evaluate the diode behaviour when working at high temperature and under severe thermal cycling conditions (comprised from 170oC to 285 oC) The radiation hardness capability has been also tested. It has been found that the hermeticity of the package is a key aspect to avoid electrical parameters drift. Moreover, the use of gold metallization and gold wire bonds on the anode allows reducing the diode surface and bonding degradation when compared to Al containing technology. On the backside cathode contact, the Ti/Ni/Au metallization and AuGe combination has shown a very good behaviour. As a result, the manufactured diodes demonstrated high stability for a continuous operation at 285oC. The reliability test performed included mechanical test with strong levels of vibration and shocks and constant acceleration, life test at maximum operating conditions with 1500 hours at 285oC at 5A forward current and 500 hours at 250 reverse voltage and 4000 thermal cycling from 150oC till 230oC with forward current of 0.8A for temperature over 25oC while the voltage drop was being monitored. The paper includes also a description of the setup solutions and the main lessons learnt for future testing of high power devices operating at a wide temperature range.
author_names: Demetrio Lopez

Juan Barbero

J C Moreno

Philippe Godignon

Xavier Jorda
title: SiC Schottky Diodes Reliability Testing for Bepi Colombo 6th Space Agency MOD Workshop on Wideband Gap Semiconductors and Components
year: 2012

abstract: Silicon carbide electronics technology, spurred on by the promise of higher power densities and operating temperatures, has advanced remarkably since the introduction of the first commercial substrate wafers just over a decade ago. This article reviews the use of SiC as the basis for power semiconductor devices. Devices such as Schottky diodes, bipolar junction transistors, and IGBTs are described. Also considered are SiC wafer growth material defects, packaging strategies and possible future developments.
author_names: C Mark Johnson
title: Clearing power roadblocks [SiC based power semiconductor devices]
year: 2004

abstract: This paper describes the design and verification results of two wideband class AB High Power Amplifiers (PA) encapsulated in commercial packages. Both amplifiers designed on WIN Semiconductors' 0.25 \mu$ m GaN on SiC technology. The selected GaN process features compact common source (CS) transistor layouts with individual source grounding vias. The family spans the whole X band frequency with the first design tuned between 7 11 GHz and the second design tuned between 10 12 GHz. Both designs have saturated power output greater than 25 W throughout the whole bandwidth with peak power added efficiency at 30% A multistage power combining matching strategy to achieve a tradeoff in wideband performance and power output is given. In depth discussion of the MMIC design of the PAs is supported by a discussion of the thermal management of the packages, including the PCB design and active cooling methodology, in order to present a fully functional PA family.
author_names: Onur Memioglu

Alper Karakuzulu

Adnan Gundel

Fatih Kocer

Ozlem Aydin Civi
title: Design and Implementation of an Encapsulated GaN X Band Power Amplifier Family
venue: 2018 13th European Microwave Integrated Circuits Conference (EuMIC)
year: 2018

abstract: With global drivers such as better energy consumption, energy efficiency and reduction of greenhouse gases, CO2 emission reduction has become key in every layer of the value chain. Power Electronics has definitely a role to play in these thrilling challenges. From converters down to compound semiconductors, innovation is leading to breakthrough technologies. Wide BandGap, Power Module Packaging, growth of Electric Vehicle market will game change the overall power electronic industry and supply chain. In this presentation we will review power electronics trends, from technologies to markets. INTRODUCTION The power electronics industry now deals with conversion and motion, and thus requires lighter/smaller, cheaper and more efficient systems. This evolution starts with improvements at the semiconductor level. There are four technologies which are best suited to handle new system requirements: silicon IGBT, Super Junction (SJ) MOSFETs, Gallium Nitride (GaN) and Silicon Carbide (SiC) based devices. POWER ELECTRONIC INDUSTRY 1) Last year, 2014, was a year of recovery for the power electronics market. After two tough years without seeing any growth, in 2014 the market 's size increased by 8.4% reaching $11.5B for power semiconductor devices. The outlook for the years ahead is also optimistic. Market growth will be driven by a significant increase in electric and hybrid vehicle (EV/HEV) sales, as well as the ramp up of renewable energy and more smart grid technology implementation. The market will surpass $17B by 2020, representing a compound annual growth rate (CAGR) of 6.9% for the period 2014 2020 (Figure 1) Power modules, and more precisely IGBTs, will lead this growth. Modules are expected to reach a CAGR 2014 2020 of 10.3% compared to 5.1% growth for discrete components. This growth in the demand of IGBT modules is due to their improved overall performance in terms of efficiency and thermal conductivity management. The new wide band gap device market will also drive growth, representing around 5% of the overall market by 2020, even though in terms of units their presence will still be limited. Figure 1: 2006 2020 power device market evolution 2) In this context the supply chain is evolving. The power electronics supply chain is very diverse and mostly application (and local market) dependent. European and American players will prioritize horizontal integration, keeping proven expertise in a specific level of the value chain. Therefore, partnerships and joint ventures will be preferred. This paper will review the major mergers and acquisitions of 2014, for instance International Rectifier's acquisition by Infineon, in order to understand their context and purpose. Some system manufacturers, such as Tesla or BYD, have understood the importance of developing their own power electronics and energy management systems for traction, chargers and batteries in order to offer extended addedvalue. Asian companies will prefer to expand vertically in order to be fully integrated and optimize the costs. Japanese players are already vertically integrated and involved in multiple applications simultaneously to benefit from their technologies across different markets. Chinese players are developing this vertical integration in order to create major market leaders in each application segment such as SunGrow in PV, GoldWind in wind and BYD in EV/HEV. This report focusses especially on the details of the Chinese market, which is driven by Chinese Government policies. In this changing environment, western and Japanese players need to bring high added value solutions to be able to 2 33 CS MANTECH Conference, May 18th 21st, 2015, Scottsdale, Arizona, USA compete with Chinese companies. The strategies of the main players will be presented. 3) The demand for compact products is increasing. Therefore, players are obliged to create partnerships between different industries in order to coordinate and use the synergies of integrated products to offer a smaller and higher performance solution. Several partnerships are influenced by this trend. In this direction, the concept of the power stack has recently appeared and ever more companies will take part in their development. Technologically, MOSFETs and IGBTs are and will continue to be the devices in greatest demand, covering low and medium high voltage applications respectively. New technologies have appeared in the last decade, such as Super Junction MOSFETs, which have brought the MOSFET family into higher voltage segments up to 900V, with better performance. In terms of power packaging, ongoing evolution is driven particularly by the EV/HEV industry. Figure 2: SiC and GaN device positioning among the traditional silicon based devices The charge of new wide band gap (WBG) materials is also reshaping the power electronics industry. Silicon carbide (SiC) and gallium nitride (GaN) based devices are intended for high voltage especially SiC high frequency and high temperature applications thanks to their advanced performance compared to silicon devices (Figure 2) SiC technology is more mature than GaN, and so industry segments such as the rail traction and PV inverters have already launched their WBG device systems based on it. The introduction of SiC into other high voltage segments, such as wind and high voltage direct current grids is also inevitable. But the big boost for these new markets should arrive with the implementation of SiC devices in electric cars' traction systems. GaN systems are still less present i n the market. Some consumer applications, such as laptop chargers, and just announced PV inverters are going to be the first segments incorporating GaN. Several system manufacturers are also developing further SiC and/or GaN device based prototypes and thus the next 5 years are going to be decisive for WBG devices' introduction into different markets. GAN IN POWER ELECTRONICS 1) Overall, 2020 exhibits a projected market size for devices of almost $600m, leading to approximately 580,000 x 6" wafers to be processed. Ramp up will be quite impressive starting from 2016 with approximately 80% CAGR to 2020, based upon the scenario where EV/HEV starts adopting GaN in 20182019. From 2015, Power Supply PFC segment will dominate the business until 2018 where it should represent 50% of the device sales. Automotive will then catch up. In the UPS applications, medium power segment is probably much more in line with GaN value proposition as savings at system level is demonstrated. We think GaN technology could grab up to 15% of market shares in this field in 2020. Figure 3: Estimated accessible markets, growth rate, and time to market of main GaN applications Room for extra cost in motor drive applications is very unlikely. Therefore, the incentives to implement new technologies such as GaN have to be serious and strong. Considering the possible improvement on the conversion efficiency augmented by a predictable price parity with Si solution by 2018, we do expect GaN to start being implemented in motor control by 2015 2016, at quite a slow rate, and reach about $45m revenues by 2020 (Figure 3) PV inverters has already adopted SiC technology and products are now commercially available. GaN could possibly partially displace SiC, playing with a better price positioning. However now that SiC is in place, the qualification of GaN may be more challenging. 2) Recent announcements shows the GaN industry is shaping along mergers, acquisitions and license agreements. Latest Transphorm Fujitsu agreement in addition to Furukawa IP portfolio exclusive licensing are very positive signs that GaN technology is spreading over all the value 34 CS MANTECH Conference, May 18th 21st, 2015, Scottsdale, Arizona, USA chain, reinforcing market position of leaders but also probably leaving weakest players by the wayside of the road. Reasonably speaking, we are forecasting 2014 will only generate $10m to $12m device sales. Such a moderate business will only let the strongest survive and will probably kill several early birds who will see their cash flow quickly melting. We think that real power GaN business will only decently start by 2016, exceeding the psychological threshold of $50m revenues. The key question is now: how to survive another 1.5 to 2 years? Far from being over ly pessimistic, we are afraid some entities won't cross the chiasm and will be acquired or will go bankrupt. Today power GaN business is mainly centered on low voltage DC DC converter (typically Pointof Loads POL) using available 200V rated devices. However this business only generates a few million revenues. Thanks to 600V device introduction this year, GaN will certainly grow quite fast in power supply and PFC applications where technical added value and economics are obvious. We have simulated several case studies and came to the conclusion that even though today market price for GaN devices exceeds Silicon ones, the improvement on efficiency and savings on the electricity bill can compensate this extra cost in less than 1 year for a 300W 24/7 operation power supply (data server type) Projected in 2018, the same power supply could even be cheaper than the silicon counterpart simply thanks to the reduction on passives (capacitor, self induction) cost, along with switching frequency increase. Therefore, we envision a preliminary take off of the PFC segment by 2015 along with an 80% CAGR over 20162020. Other applications such as the PV inverter and, to a lesser extent, in motor control, we see GaN starting to capture market share by 20152016. The next big thing, will unquestionably be EV and HEV segments where GaN could definitely play a role in power systems such as low voltage (14V 200 400V) DC DC converters and later on for battery chargers (on board 3.6 7.2 kW first then off board 50kW+ However, we do not see any chance for GaN to enter in the power train inverter (60kW+ before 2019 2020, due to the lack of current capabi
author_names: Hong-Ting Lin
title: 2.3 Market and Technology Trends in WBG Materials for Power Electronics Applications
year: 2015

abstract: The ongoing development of drives for city buses is marked by an increasing hybridization and electrification. A high operation time and the utilization of new drive concepts using permanent magnet synchronous machines (PMSM) require very durable power electronic and hence power semiconductor technology. First of all the article will initially explain current and future city bus drive concepts and then look at the resultant requirements on power electronics. Starting with state of the art drives it will be shown that future drive concepts using PMSM will result in new requirements for power electronics and especially on the load cycling capability of IGBT. Strategies to fulfill these requirements will be discussed in the second part. The last chapter provides an overview of promising new packaging technologies for power semiconductors. The potential thermal cycling capability of these new technologies will be estimated. Finally the potential of SiC for the lifetime of electric drives will be briefly evaluated.
author_names: Martin Helsper

Niklas Ruger
title: Requirements of hybrid and electric buses a huge challenge for power electronics
venue: 2014 16th European Conference on Power Electronics and Applications
year: 2014

abstract: The wide bandgap (WBG) devices, like gallium nitride (GaN) and silicon carbide (SiC) devices have proven to be a driving force of the development of the power conversion technology. Thanks to their distinct advantages over silicon (Si) devices including the faster switching speed and lower switching losses, WBG based power converter can adopt a higher switching frequency and pursue higher power density and higher efficiency. As a trade off of the advantages, there also exist the high frequency oriented challenges in the adoption of the GaN HEMT under research, including narrow safe gate operating area, increased switching overshoot, increased electromagnetic interference (EMI) in the gate loop and the power stages, the lack of the modules of packages for high current application, high gate oscillation under parallel operation. The dissertation is developed to addressed the all the challenges above to fully explore the potential of the GaN HEMTs. Due to the increased EMI emission in the gate loop, a small isolated capacitor in the gate driver power supply is needed to build a high impedance barrier in the loop to protect the gate driver from interference. A 2 W dual output gate driver power supply with ultra low isolation capacitor for 650 V GaN based half bridge is presented, featuring a PCB embedded transformer substrate, achieving 85% efficiency, 1.6 pF isolation capacitor with 72 W/in3 power density. The effectiveness of the EMI reduction using the proposed power supply is demonstrated. The design consideration to build a compact 650 V GaN switching cell is presented then to address the challenges in the PCB layout and the thermal management. With the switching cell, a compact 1 kW 400 Vdc three phase inverter is built and can operate with 500 kHz switching frequency. With the inverter, the high switching frequency effects on the inverter efficiency, volume, EMI emission and filter design are assessed to demonstrate the tradeoff of the adoption of high switching frequency in the motor drive application. In order to reduce the inverter CM EMI emission above 10 MHz, an active gate driver for 650 V GaN HEMT is proposed to control the dv/dt during turn on and turn off independently. With the control strategy, the penalty from the switching loss can be reduced. To build a high current power converter, paralleling devices is a normal approach. The dissertation comes up with the switching cell design using paralleled two and four 650 V GaN HEMTs with minimized and symmetric gate and power loop. The commutation between the paralleled HEMTs is analyzed, based on which the effects from the passive components on the gate oscillation are quantified. With the switching cell using paralleled GaN HEMTs, a 10 kW LLC resonant converter with the integrated litz wire transformer is designed, achieving 97.9 efficiency and 131 W/in3 power density. The design consideration to build the novel litz wire transformer operated at 400 kHz switching frequency is also presented. In all, this work focuses on providing effective solutions or guidelines to adopt the 650 V GaN HEMT in the high frequency, high power density, high efficiency power conversion and demonstrates the advance of the GaN HEMTs in the hard switched and soft switched power converters. High Frequency Oriented Design of Gallium Nitride (GaN) Based High Power Density Converters
author_names: Bingyao Sun
title: High Frequency Oriented Design of Gallium Nitride (GaN) Based High Power Density Converters
year: 2018

abstract: High temperature electronic packaging requires power switching devices, electrical components, and materials to withstand ambient temperatures approaching 300degC. In the case of the former, the electrical performance of traditional silicon based electronics are lacking at operating temperatures greater than 150degC. In the early 1990's, however, commercially available silicon on insulator technology (i.e. HTMOS appeared which led to parts designed to last at least five years at 225degC and operate to 300degC with reduced lifetime. For operating environments beyond 300degC, no other power device candidate appears on the technological horizon other than silicon carbide (SiC) Although SiC power devices are not yet commercially available, it is evident that this technology will have an impact on power electronics package design strategies required to operate in high temperature environments. The candidate materials providing the mechanical support for these electrical components must also be able to withstand this same hostile environment. Diamond and diamond like carbon (DLC) possess the unique combination of excellent thermal conduction, electrical insulation, and mechanical properties that make them candidate materials of choice for power packaging applications, especially those requiring high performance thermal management solutions. In this paper, a preliminary study of polyimide, diamond and DLC substrate technologies for high temperature, high power packaging applications is presented.
author_names: A Lostetter

Kraig J Olejniczak

Ajay P Malshe

William D Brown

A Elshabini
title: Silicon carbide power die packaging in diamond substrate multichip power module applications
year: 2001

abstract: Increase of power density and performance at simultaneously decreasing cost has always been the one way direction in power semiconductors world. It is shown that this will last also in foreseeable future, even more with new semiconductor materials. Common to old Si and new materials like SiC and GaN devices is that all of them head for higher current densities with a need for higher operating temperatures in steps up to 200 degC and above which nowadays assembly technologies still cannot cope with, mainly because of much higher load and temperature cycling capability needed. Also common development trend with all materials is to switch faster to reduce losses in the devices and thus increase current capability. It is also shown that a tremendous potential of about 7 times lower switching losses lies in this direction and what will be the challenges to assembly and system setup with respect to low inductive interconnect technology.
author_names: Gerhard Miller
title: New semiconductor technologies challenge package and system setups
venue: 2010 6th International Conference on Integrated Power Electronics Systems
year: 2010

abstract: With the current trend towards smaller and highly portable consumer electronics and other industrial applications, one area with a great demand for such miniaturization is the lighting industry. The main hinder has been the power supplies, due to their bulky energy storage components. Through the use of soft switching topologies, with the incorporation of the state of the art devices and combined control, circuits can operate at higher switching frequencies with smaller passive devices, allowing for miniaturized form factors towards added integration. Brief Description and Figures The legacy solution for LED drivers is a 2 stage structure comprised of a power factor correction rectifier with an energy storage capacitor, and a point of load DC DC converter. Conventionally, pulse widthmodulated converters are the primary candidates for the AC DC and DC DC stages, as they offer high efficiency and are easy to control. However, their operation is based on hard switching and typically run at low switching frequencies, resulting in the need for larger passives to store and process power. The work performed herein addresses some design considerations towards miniaturized LED drivers. Topologies: Resonant converters have the advantage of soft switching operation, and hence they have the potential for operation at higher frequencies, resulting in smaller passive components and overall less weight and size. Control: Through the combination of several control schemes, e.g. frequency control with burst mode control, high efficiency can be maintained across operational load range. Devices: The recent advancements in the wide band gap (WBG) devices promise many advantages over Silicon switches, in terms of lower gate charge, output capacitance, and on resistance for the same breakdown voltage, which can result in lower gating, conduction, as well as switching losses. On the other hand, integrated passive devices (IPDs) technologies show promising advancement towards a highly integrated system in the form of the PSiP and the more compact PwrSoC. Energy Storage: Today's LED drivers suffer from short lifetime due to the incorporation of electrolytic capacitors for energy storage. Through the use of active ripple port circuits, the size of the capacitor needed to filter out the double the line frequency ripple is reduced, and accordingly more robust capacitor technologies can be employed. Figure 1 shows measurement results of a class DE series resonant converter that can be incorporated for the AC DC and the DC DC stages in an LED driver. The converter operates up to 400V input and softswitching is achieved at high voltages through proper adjustment for the switching signals dead time. The scope image shows the switching node voltage (blue) and sinusoidal resonant inductor current (green) for 350V input voltage. The graphs following show the efficiency and output power for different output voltages, and illustrate how frequency modulation can be used for line/load regulation. The converter operates around 1 MHz and incorporates high voltage GaN switches and SiC diodes. Miniaturization of LED Drivers This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731466 Figure 1 Measured results for Class DE Series Resonant Converter. Key Contributions There is an increasing demand for smaller, more efficient and longer living LED drivers. Resonant softswitching topologies operating at high frequencies with combined control schemes, and incorporating wide bandgap semiconductors and integrated passive devices, in a highly integrated package can promise substantial reduction in the size, weight and cost, as well as the extended lifetime of the power converters in LED drivers (Figure 2) Figure 2 Proposed Miniaturization strategy. References [1] A. Knott et al. "Evolution of Very High Frequency Power Supplies," in IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 2, no. 3, pp. 386 394, Sept. 2014. [2] Y. Nour and A. Knott, "Module integrated GaN power stage for high switching frequency operation," 2017 IEEE 12th International Conference on Power Electronics and Drive Systems (PEDS) Honolulu, HI, 2017, pp. 848 852.
author_names: Ahmed M Ammar

Frederik Monrad Spliid

Yasser Nour

Arnold Knott
title: Miniaturization of LED Drivers
year: 2018