Cambridge Microelectronics Ltd Public Funding

Advanced GaN Device Technology Development project (DANCE) will aim to develop a vertical GaN device rated at 1.2kV. A suitable package for 1.2kV GaN will also be developed within the project and devices tested for reliability. GaN power devices offer very higher-frequency operation and reduced power dissipation enabling more efficient system performance while having a smaller form factor and reduced weight. There are currently no 1.2kV GaN MOSFET devices available on the market. The only commercial GaN power devices available today are lateral high electron mobility transistors (HEMTs) built on AlGaN/GaN/Si wafers where hetero-epitaxy limits their breakdown capability to ~650V and leads to long term reliability and dynamic on-state (Rdson) problems. The 1.2kV GaN MOSFET development proposed here will use GaN-on-GaN substrate which use homo-epitaxy allowing development of reliable GaN power devices with much higher voltages. Partners from the UK (SPTS, Camutronics, CSAC) and Taiwan (ITRI, Innolux) will collaborate closely on both front-end and back-end activities and will cover all steps needed to form a reliable 12kV GaN solution: epi-growth and process development (SPTS, ITRI), device design optimization (Camutronics, ITRI), wafer processing (SPTS, ITRI), testing (Camutronics, ITRI) and package development and reliability testing (CSAC, Innolux, ITRI). Novel processing techniques for forming U-shaped trenches will be developed which are needed to reduce electric field at the trench bottom. In addition to this, a suitable deep trench etch recipe will also be developed which is needed for the termination area of the die. Crucially, reliable gate oxides also need to be developed. In terms of epi growth, processing partners from the UK and Taiwan will work jointly on developing epi layers which are sufficiently thick for 1.2kV devices and low in defects needed for high current devices. In parallel with device development, partners from the UK and Taiwan will develop assembly techniques suitable for 1.2kV devices using new interconnection recipes, bumping and 3D printing. Fabricated devices will be assembled into developed packages and tested for reliability to ensure they can be used in the applications.

The project "Pre-packaged Power Devices for PCB Embedded Power Electronics" (P3EP) develops a UK supply chain for PCB-embedded power systems with Gallium Nitride (GaN) devices. The P3EP supply chain will allow PEMD manufacturers to build converters with the highest power densities and it will allow UK power semiconductor companies to enter these markets. Wide bandgap power devices such as GaN offer extremely high switching speeds and the possibility to significantly reduce system size. But this can only be exploited with new packaging and module construction methods which increase thermal transfer and reduced parasitic effects. The emerging technology of embedding power devices into the PCB has proven to be the most advanced way to achieve this goal. P3EP develops the complete supply chain in the UK. The P3EP manufacturing chain is based on GaN pre-packages. Pre-packages have major advantages over bare dies because they allow production testing, characterisation, and reliability qualification. This improves yield, cost, and time-to-market for the PEMD system. Further, pre-packages use materials with optimised compatibility with the chip and enable much-simplified embedding into the system-PCB. The P3EP supply chain comprises: • GaN power semiconductor supplier and Cu chip metallisation • Production capability for GaN pre-packages. This includes pre-packages with single or multiple GaN devices as well as half-bridge arrangements with integrated driver. • Manufacturing of power-system PCBs by embedding tested GaN pre-packages followed by traditional assembly into a full converter. • Set up the digital toolchain for the customisation of pre-packages and embedded power sub-systems for a large variety of power electronic applications. • Set up the supply chain for characterisation of electrical, thermal and reliability performance of device, pre-package, and embedded subsystems. All these embedded manufacturing capabilities can be simply adapted to facilitate testing, characterisation and embedding of other power semiconductor technologies such as Silicon or Silicon Carbide. Power systems with embedded WBG devices based on the P3EP supply chain will deliver improvements in the weight, volume, efficiency, and power density of the converter. These aspects are particularly important for automotive and more-electric aerospace applications, the early adopters of the technology. While there are world-leading electronics manufacturing capabilities in the UK, there is currently no manufacturing line for assembling embedded power electronics. Project P3EP will close this cap enabling the UK PEMD industry to deliver smaller, lighter, more reliable solutions in power electronics for a wide range of markets.

Awaiting Public Project Summary

ASIT (Advanced Silicon Carbide Technology) is a £1M industry-led collaboration between Microsemi Semiconductor Ltd (a Microchip Company), eDrive engineering Services Ltd, Cambridge Microelectronics Ltd, the Compound Semiconductor Applications Catapult and tier 1 end user hofer power train UK Ltd. Inner-city air quality is a significant and growing challenge for governments across Europe, leading to 9,400 deaths per-year in London alone[1]. Zero-emissions vehicles will help reduce this number ASIT supports the Department for Transport 'Road to Zero' strategy by addressing the $64Billion global electric vehicle power inverter market. By going against conventional invertor construction and using technology transfer from healthcare (electronics), we are developing a highly advanced integrated 100kW power module. Using the latest generation Silicon Carbide (SiC) MOSFET technology combined with advanced laminated packaging techniques from healthcare, we are designing an power inverter that is small enough to be mounted directly onto or into the electric motor offering significant weight and space saving over conventional product. The impact of this weight/space saving is a notable improvement vehicle range (km/recharge) and will help to reduce the public condition of "range anxiety". Range anxiety is a major to public perception issue and hence and obstacle Electric Vehicle take up.

Within this project we will develop a 3.3kV/1.8kA Reverse Conducting IGBT (RC-IGBT) devices to replace separate IGBT and Diode chips currently used in modules for rail transportation, wind power generation and High Voltage Direct Current (HVDC) transmission. Compared with the state-of-the-art IGBT-based modules, the RC-IGBT module will deliver higher output current, lower thermal resistance while ensuring twice as long power cycling lifetime. We will develop and optimise RC-IGBT devices primarily for electric drives for trains which will ensure reliable, more energy efficient and environmentally friendly operation of trains and facilitate growth of the rail network and more efficient transportation of people and goods, a key enabler for urbanisation. Modules with developed 3.3kV RC-IGBTs can also be used in wind turbines and HVDC transmission network and further extended to 1.2kV and 1.7kV voltages and used for electric vehicles and solar PV systems. Thus, the developed RC-IGBT technology will make a significant contribution in solving energy and transportation challenges facing both rural and urban populations in China in an energy-efficient, sustainable manner.

TRASiCA will demonstrate the gains in performance and system lifetime that can be brought about in the traction industry by integrating silicon carbide (SiC) power device technology into existing systems. A ‘hybrid SiC’ power module incorporating SiC power diodes with state-of-the-art Si trench IGBTs will be produced for Dynex Semiconductor’s customer Fertagus, and the performance benchmarked on the train network in Lisbon, Portugal, against the current silicon state-of-the-art. The SiC diodes used within this project represent a significant innovative step, given that devices of the required high current and high voltage (>50A, 3.3 kV) are not available on the market. Therefore, the diodes used within the module will be designed within Cambridge Microelctronics (Camutronics), and fabricated at Warwick University, so that they are specifically tailored for the application they serve. This will come after an exhaustive feasibility study that will compare the suitability of many SiC diode technologies for the target application.

Within the DepLaH project we will develop an advanced 1000V rated lateral depletion MOSFET (normally “on” device) and use it to build an application demonstrator for implantable medical device which will have significantly longer lifetime and lower energy consumption than existing solutions. For the first time we will design and fabricate 1000V rated depletion MOSFETs (depMOS), design a new application circuit based on depMOS approach and build an application demonstrator. The new circuit will consume less battery power thus increasing the product lifetime and reducing frequency of replacement surgery. The circuit optimised for depMOS will require fewer components compared to the existing solutions which use enhancement (normally “off”) MOSFETs which will improve medical product reliability and reduce its size making it more comfortable for patients.

Within the CoLPACK project we will develop an advanced Chip-On-Board (COB) packaging technique suitable for 3D PCB stacking and realisation of more compact size-sensitive electronic products in medical applications, LED lighting and portable consumer electronics. For the first time we will assemble lateral ultra-high voltage (UHV) IGBT dies directly onto the application PCB using flip-chip technique. Proprietary lateral >800V IGBTs with compelling area and switching advantages over competitive solutions have been recently developed by Cambridge Microelectronics. By using a lateral IGBT, where all terminals are on the front side of the die, UHV bondwires (used to contact UHV terminal which is on the back-side of the vertical IGBT die) will be eliminated from the PCB assembly. This is the first time bare UHV devices will be used for flip-chip, COB assembly and 3D PCB stacking.

Hafren will develop novel lateral MOS-based high voltage (HV) devices (Vbr>1kV) to replace oversized and inefficient vertical MOSFETs in a range of applications including medical, consumer electronics (AC/DC converters) and LED drivers where high blocking voltage and low current drive is required. When compared to vertical MOSFETs, these lateral devices will be 6 times smaller with up to 10 times lower capacitance and extremely low leakage currents (<100nA @125C). This will significantly reduce power losses in the system, reduce cost and system footprint resulting in a compelling product. Lateral devices will be based on CMOS technology permitting monolithic integration with other external components (diodes, gate drivers, protection circuits), enabling realisation of more compact lower cost solutions with improved efficiency. The lateral design with all terminals on one side of the die will enable simpler product assembly process, leading to cheaper and more reliable end products. Novel flip-chip solutions for Chip-on-Board assembly of lateral HV devices will also be developed, which will, coupled with 6 times smaller MOSFETs enable further product miniaturisation.

Power electronics is an integral part of our lives – every stage of electrical energy conversion from the point of generation (including renewable sources such as wind, solar, etc.), through transmission to the point of consumption (including industrial and automotive applications, household appliances and consumer electronics) is controlled by power electronics. Global energy demand and corresponding CO2 emissions are predicted to increase by more than 50% in the next 25 years. A sensible solution to addressing growing energy consumption requirements is not by creating more - but by wasting less. This can only be achieved if new technologies are deployed to dramatically increase energy efficiency of power electronics applications. Power devices are at the heart of power electronics systems: innovative device designs which require less silicon area and operate with lower power losses act as main enablers for procurement of more efficient energy conversion solutions. We will develop a new class of ultra-compact high voltage power devices - Smart Lateral Insulated Gate Bipolar Transistors (Smart LIGBTs). These devices will have 3 to 5 times smaller chip area and 3 to 10 times faster switching than other lateral bipolar devices realised in bulk Si. Such devices will enable more energy efficient system performance including lower stand-by losses, presently responsible for around 10% of total electricity bill. Fabrication is based on standard CMOS steps which will ensure low cost, high yield, fast development and efficient implementation in a range of power electronics products. Reduced device area and lateral geometry will enable integration of additional intelligence and peripheral components on the same chip and use of smaller, more compact packages for higher power applications. This will result in further miniaturisation of products such as portable power supplies for mobile phones, tablets and laptops as well as more efficient, compact drivers for LED lighting.