Challenges and solutions for high-energy testing

This article originally appeared in the Nov'23 magazine issue of Electronic Specifier Design – see ES's Magazine Archives for more featured publications.

With many global OEMs and governments investing in the electrification of vehicles, demand for power ICs needed to manufacture EVs is also rising. Companies like CREA, a subsidiary of Advantest, are facilitating this major shift in the automotive industry, supplying vital power semiconductor test equipment to chipmakers around the world.

Although the global semiconductor market is currently experiencing a slowdown, the automotive sector maintains steady growth fuelled by the demand for EVs. What used to be a niche market is now rapidly expanding to the mainstream, and companies that supply power IC technology must increase production volume to meet growing demand. Earlier this year, CREA leased a new building to expand production capacity and keep up with ongoing business growth.

Higher capacity is needed for CREA to produce test equipment for a wide variety of power semiconductors, including insulated-gate bipolar transistors (IGBT) and silicon carbide (SiC) and gallium nitride (GaN) semiconductors. SiC has proven superior to traditional IGBTs due to its higher thermal conductivity and ability to tolerate high voltages, ultimately offering higher switching speeds. SIC enables engineers to maintain high-power capabilities in systems that are lighter in weight than traditional IGBTs. Wide-bandgap technology such as SiC is the key to developing more efficient advanced battery systems that will enable new EVs to go farther and faster.

Addressing high-power test requirement

SiC brings its own unique manufacturing challenges, necessitating a thorough testing process to detect defects. Two types of tests are used for power devices: static and dynamic. Static test simply tests the device when it is ON or OFF. Dynamic test is much more challenging, as it tests the device during the transition from ON to OFF or OFF to ON, during which there is an instantaneous voltage change with an extremely high current and high voltage. The combination results in massive power levels that can reach kiloamp/kilovolt capacity. For high power, parasitic factors such as inductance and capacitance play an important role in the measurement and can potentially create conditions that may damage the tester.

Testing high-powered SiC devices requires highly refined, specialised test equipment. CREA’s low-stray-inductance and probe card interface (PCI) technology enables engineers to minimise parasitic values. This allows the performance of specialised tests needed to ensure reliability and quality, facilitating the development of efficient batteries for new EVs.

Bare-die test benefits

To meet customer demands for lower cost, CREA is expanding its bare-die test capabilities. Package test is simpler, but if a single switch malfunctions, the entire package must be disposed of. Bare-die test is more cost-efficient and creates less waste – the only challenge is that a probe card is needed to perform the test. Probe cards are fragile, and the high amount of energy generated during dynamic test can break the probe card and damage the tester itself. CREA’s PCI technology monitors each probe needle for abnormal current distributions, shutting off the tester when such an abnormality is detected to prevent damage. CREA also developed a chamber for bare-die test that moderates temperature by controlling airflow to prevent sparking that can occur while working with high voltages, ultimately reducing the threat of harm to the ATE. The company’s unique PCI and chamber technology improves the quality of bare-die test and ensures the safety of the equipment. Bare-die test utilising the PCI and thermal control technology holds the key to expanding dynamic test to the wafer level.

Another challenge with SiC technology is that it is still maturing. As noted earlier, SiC technology provides many benefits over traditional IGBT technology, including superior thermal dissipation, tolerance for high current and high voltage, and smaller size. However, while many major semiconductor companies are investing in R&D to support SiC technology, SiC is very different from silicon wafer technology. It requires completely different equipment and the automated tools that factories currently have are designed for silicon wafers and will not work with SiC. Because SiC is a maturing technology, production yields are low. This creates a significant opportunity for test companies to deliver SiC-optimised test equipment. CREA continues to refine its power IC testing technology to increase yield and help customers maintain sustainable business models that can keep up with rising demand.

Conclusion

The power IC business is evolving fast, fuelled by major investments from the global semiconductor community. CREA’s patented LSI and PCI technology provides specialised testing solutions for power ICs found in hybrid and EV automotive engines. These solutions will accelerate the shift from 400V to 800V batteries, accommodating the testing specs needed to develop cutting-edge EV technology.