1. Si MOSFET

Power MOSFET applications fall into three types: driving loads such as DC motors, solenoid valves and LEDs; protection circuits such as reverse polarity and overcurrent protection; and DC/DC conversion circuits in power modules such as buck, boost and SEPIC.

Automotive MOSFETs fall into two main categories. The first is low voltage MOSFETs rated 40 to 100 V, used in 12 V and 48 V vehicle low voltage electrical systems, generally with a trench gate structure. Trench gates themselves continue to be innovated and iterated, the most representative being the split gate or shielded gate trench (SGT) structure, now widely used in low voltage MOSFETs by Infineon OptiMOS and onsemi, while NXP has introduced superjunction technology into low voltage trench MOS with its new Trench 9 superjunction technology to minimise on resistance and power loss.

The second category is high voltage MOSFETs rated 500 to 800 V, used mainly in on-board chargers, DC/DC converters and other applications added by electrified models. These generally use superjunction technology, which reduces on resistance while raising switching frequency, balancing response speed against power loss.

MOSFET characteristics

2. Market size of Si MOSFET

Yole forecasts that by 2025 the global market for power semiconductor discrete devices and modules will reach 7.6 billion and 11.3 billion US dollars respectively. According to the China Industry Information Network, the IGBT market in mainland China was expected to reach 29.08 billion yuan in 2023, up 11.6 percent year on year. According to a report on the current state of China's semiconductor device industry with in-depth analysis and future investment forecasts, the MOSFET market in mainland China was expected to reach 39.62 billion yuan in 2023, or 5.66 billion US dollars at an exchange rate of 7, up 4.8 percent year on year. Less than 30 percent of that is used in the automotive industry. The top five suppliers together hold more than 60 percent of the market, and the automotive MOSFET market is essentially monopolised by foreign companies.

The ten largest MOSFET suppliers by revenue worldwide are still mainly European, American and Japanese companies. Infineon leads the global power MOSFET market by a wide margin with a 29.7 percent share. Infineon and onsemi together account for 37.4 percent, and the top ten together account for 78.2 percent of revenue.

Automotive applications, namely electric vehicles and charging piles, take the largest share of MOSFET demand at 33 percent, with electric vehicles at 25 percent and charging piles at 8 percent. By voltage class, low voltage MOSFETs of 0 to 40 V will account for 39 percent of demand by 2026, medium voltage of 41 to 400 V for 26 percent, and high voltage of 600 V and above, widely used in 220 V systems, for 35 percent. Meanwhile the market penetration of SiC MOSFETs and GaN MOSFETs is gradually increasing.

The low voltage MOSFET market is relatively mature, and international suppliers have begun developing high voltage devices such as superjunction MOS, IGBT and SiC MOS to capture new growth opportunities. Given the slowing pace of low voltage MOS iteration, domestic suppliers are expected to narrow the gap with foreign companies and achieve import substitution. Domestic power MOSFET companies currently serve consumer and industrial applications more than automotive, and have little experience in automotive supply chain support, especially lacking support from downstream tier one automotive electronics suppliers. Against the background of a severe chip shortage in the automotive industry, cooperation across the upstream and downstream supply chain needs to be strengthened to develop a domestic device supply chain.

3. Development of domestic power chips

(1) Overall status. In the field of automotive motor controllers, the product lines of domestic brand tier one suppliers cover 25 to 260 kW, using power devices including Si MOSFET, IGBT, SiC MOSFET and GaN FET, in packages ranging from discrete devices such as the TO-263 package for MOSFETs and TO-247 for IGBTs to half bridge and three phase full bridge packages. Domestic silicon based IGBT and MOSFET power devices are relatively mature in die fabrication, packaging and testing, have largely achieved import substitution and offer a significant cost advantage.

Power devices for A00 class models are divided by battery voltage into two ranges, 100 to 180 V and 200 to 450 V. In A0 and A00 class products, system cost requirements are strict, so the power unit is often built from multiple power devices in parallel as well as from modules, raising power density while reducing cost.

· In the 100 to 180 V range, operating voltage is relatively low and current high, often above 350 Arms, so MOSFETs are connected in parallel, typically 8 to 14 devices. StarPower and Silan Microelectronics have both launched and validated such products. Silan's SVGP157R2NSTR in a TO-263-2L package, rated 150 V and 100 A, is used in a 30 kW A00 class vehicle inverter with eight devices in parallel delivering 375 Arms.

· In the 200 to 450 V range, voltage is relatively high, so single IGBTs in TO-247 packages are usually connected in parallel as the main drive power unit, with devices rated 600 V and above 120 A. Domestic suppliers including Silan Microelectronics and StarPower already have volume products in this application. StarPower's DG120X07T2, a 120 A and 600 V die, is used in a 35 kW three-in-one unit and matches international suppliers in stray parameter control, output current capability and consistency.

IGBT modules are also a mainstream option for A0 class vehicles. Compared with parallel single devices, IGBT modules offer higher integration and reduce the risk of shortened life caused by parameter mismatch, though system structural design is less flexible. Module products are mature in automotive applications and are also the main field for domestic chips and modules. StarPower's localised 650 V and 400 A IGBT module GD400FFX65P3S is used in Great Wall Motor's ORA Cat series and the Renault Dacia Spring Electric.

Power devices for A class vehicles generally operate at 240 to 450 V, usually using IGBT modules with a current capability of 600 to 800 A. Domestic suppliers such as CRRC Semiconductor and StarPower have launched cost effective products and achieved volume application; Changan Automobile, for example, has adopted StarPower's P6 package 820 A and 650 V IGBT module as a localised replacement.

Main drive applications for B class and larger vehicles fall into two routes: 400 V systems and 800 V systems.

· In 400 V systems, maximum operating voltage is generally below 500 V and current is high. Based on current mature IGBT dies with improved packaging and cooling, these systems still meet some product requirements, and domestic power chips still have a role. Prototypes of GaN FET based motor controllers, DC/DC converters and on-board chargers have also been completed with good performance indicators. GaN devices typically withstand 650 to 950 V and can therefore be used on 400 V platforms, and because they have low losses and are manufactured with processes similar to conventional silicon, they have good market prospects.

· In 800 V systems, modules must withstand 1200 V or more while delivering above 400 Arms, which conventional IGBT modules may not achieve. Vehicle makers and tier one suppliers therefore replace IGBTs with third generation wide bandgap devices. The SiC suppliers able to produce in volume are still mainly foreign companies such as Infineon, Rohm, ST and Wolfspeed. No domestic supplier yet has a SiC MOSFET die formally applicable to main drive inverters. CRRC Semiconductor, Sanan Optoelectronics and China Electronics Technology Group continue to develop SiC MOSFET dies and have launched first generation products. The SiC MOSFET module MD63HTO120P6HE, rated 1200 V and 6.3 mΩ and based on the WM1A025120B die rated 1200 V and 25 mΩ developed by CETC with StarPower, was expected to reach volume production in main drive inverters in 2023 and 2024 through product iteration.

(2) Progress of chips into vehicles. StarPower's self-developed, volume produced IGBT dies for new energy vehicles mainly comprise the 650 V, 750 V and 1200 V series, with single die current ratings covering 150 A, 200 A and 270 A. The dies use the latest generation trench gate field stop structure, offering low loss, high power density and high junction temperature. Based on these dies the company has developed a full series of automotive IGBT modules covering motor controllers from 30 kW to 200 kW, now widely used in A00, A0, A and B class vehicles and successfully replacing imported products in volume. The company's automotive-grade IGBT modules entered volume application in the new energy vehicle industry in 2012; by the end of 2022 cumulative vehicle installations had exceeded 2 million, including 200,000 in 2020 and more than 600,000 in 2021, with full year 2022 installations expected to exceed 1 million.

StarPower began developing automotive silicon carbide modules in 2015. After years of work it has mastered key processes such as silver sintering and copper wire bonding for silicon carbide module packaging and achieved small volume production. It has won next generation silicon carbide controller projects from several domestic and international vehicle makers and tier one customers, and its silicon carbide modules have entered volume application in on-board charging. The company now offers a full series of silicon carbide modules covering 750 V, 900 V and 1200 V and 100 A to 800 A.

BYD Semiconductor, a subsidiary of BYD, is the largest automotive-grade IGBT supplier in China, with an integrated full industry chain including chip design, wafer fabrication, packaging and testing and downstream applications. According to STAR Market Daily, BYD's automotive-grade IGBT is now in its fifth generation and its silicon carbide MOSFET in its third, with its own SiC production line under construction. The four wheel drive version of BYD's flagship Han EV was the first domestic model to carry SiC MOSFET modules in volume. BYD plans for its electric vehicles to switch fully to silicon carbide power semiconductors by 2023, improving overall vehicle performance by a further 10 percent.

CRRC Times Semiconductor, a subsidiary of CRRC Times Electric, mainly produces high power thyristors, IGCTs, IGBTs and SiC devices and their assemblies. Operating in IDM mode and focused on rail transit, high voltage transmission and distribution and new energy markets, it is advancing new energy vehicle component projects including integrated systems of controllers, motors, IGBTs and sensors. Its power devices serve rail transit, new energy vehicles and photovoltaic inverters. IGBTs cover 750 V to 6500 V and SiC devices cover 650 V to 1700 V, with 700 V and 3300 V hybrid SiC traction converters and 3300 V full SiC traction converters already in volume application.

The power semiconductor division of Shanghai Belling focuses on MOSFETs and IGBTs. Its low and medium voltage MOS products cover 20 V to 100 V and serve industrial control, motor drives, new energy and automotive peripheral applications. Its medium and high voltage MOS series covers 150 V to 1500 V and serves industrial control, communication power supplies and power grids. IGBTs cover 400 V to 1200 V with both discrete and module development and production capability, including specialised products such as the automotive-grade ignition IGBT BLG3040.

4. AEC-Q101 qualification required for automotive Si MOSFETs

AEC-Q101 applies to discrete semiconductor devices. Its full title is Failure Mechanism Based Stress Test Qualification for Discrete Semiconductors, and it is commonly called the stress test standard for discrete semiconductors. The current Revision E was published on 1 March 2021.

AEC-Q101 defines the minimum stress test requirements and reference test conditions for discrete semiconductor components. Its purpose is to determine whether a device can pass stress testing in application and be regarded as providing a certain level of quality and reliability.

AEC-Q101 is divided by wafer fab technology and mainly covers MOS, IGBT, diodes, transistors, voltage regulator diodes, TVS, thyristors and similar devices.

1. AEC-Q101 product validation flow

2. AEC-Q101 test groups

Parameter testing: performance, appearance, parameter verification, physical dimensions, thermal resistance, avalanche capability, short circuit reliability, dielectric integrity and similar.

Environmental stress testing: stress tests performed according to military electronic device environmental standards and general automotive electronic environmental standards, such as high temperature reverse bias, high temperature gate bias, temperature cycling, pressure cooker, HAST, high temperature high humidity reverse bias, high temperature high humidity operating, intermittent operational life, power temperature cycling, constant acceleration, vibration, shock and hermeticity.

Process quality assessment: process quality assessment of the component covering packaging, subsequent electronic assembly processes and use reliability, such as ESD, DPA, terminal strength, solvent resistance, resistance to soldering heat, solderability, wire pull and shear, die push, and lead-free testing.

3. NTEK testing capability against AEC-Q101 requirements

About NTEK

NTEK Group was founded in 2009 and is headquartered in Shenzhen. The group provides quality research and technical services covering R&D verification, inspection and testing, failure analysis, simulation and market access for intelligent connected vehicles, electronic communications and new energy.

NTEK has extensive experience in automotive-grade electronic certification and has helped more than 100 companies pass AEC-Q series certification. Driven by the need of vehicle makers to localise automotive-grade components and supported by the domestic semiconductor industry, NTEK provides comprehensive testing and certification services, applying AEC-Q automotive standards to control the safety and quality of automotive components, supporting the growth of domestic automotive-grade components and adding new momentum to the intelligent vehicle safety system.