Test vendors face new challenges in serving power semiconductor market

The latest generation of high power semiconductor devices demands that test instrumentation vendors deliver solutions capable of characterizing significantly higher rated voltages and peak currents than ever. As I mentioned in my last post, many power device manufacturers are turning to compound semiconductor materials like silicon carbide (SiC) and gallium nitride (GaN) to create high power semiconductor devices. These newer devices typically are significantly smaller than their silicon equivalents and have much higher power density, better high temperature performance, higher frequency response, and lower ON resistance, all of which add up to greater operating efficiency. These devices typically are far less leaky than silicon, which poses still another challenge for test suppliers—integrating higher current measurement sensitivity with higher voltage sourcing capability in the same solution.
Compound semiconductor technologies are less technically mature than silicon technology, which complicates designing and characterizing devices based on these materials, as well as characterization as part of quality assurance, failure analysis, and process monitoring. These challenges and the higher cost of the materials themselves make compound semiconductor devices more expensive than silicon. That puts pressure on the cost of test, especially final test. As a result, power semiconductor OEMs are searching for ways to balance developing and producing devices that operate at higher power levels and with lower leakage levels with testing these devices cost-effectively.

The once relatively slow rate of change in the power semiconductor industry meant that existing equipment types largely met these manufacturers' test requirements for a number of years. As a result, test instrument OEMs often had little motivation to develop more capable solutions; some even allowed their solutions to go obsolete. However, power semi OEMs have realized that the T&M instrumentation they relied on for so long is no longer capable of meeting their product development requirements. Today, device OEMs are searching for new approaches to high power semi material and device testing, including the use of instruments with integrated sourcing and measurement capabilities, like source measurement units (SMUs). Essentially, SMUs are fast-response, read-back voltage and current sources with high accuracy measurement capabilities, all tightly integrated in a single enclosure.

Although early SMUs lacked the dynamic range essential to characterizing high power semi devices, newer models can deliver the higher levels of power and low-level current sensitivity needed to test these devices accurately in R&D, FA, and QA applications, as well as the speed necessary for cost-effective production test. For example, Keithley’s new Model 2657A High Power System SourceMeter® instrument is designed for use across multiple departments within an organization. This offers the added benefit of measurement correlation at various stages throughout the commercialization process, which helps resolve problems faster and enables quicker time to market.

The next generation of power semiconductor devices represents some significant test challenges for device OEMs and test vendors alike. The test vendors who will ultimately serve this industry best will be those who deliver the best combination of power, performance, and cost-effectiveness available.