JEDEC Solid State Technology Association, a standards development organization for the microelectronics industry, announced the publication of JEP173: Dynamic On-Resistance Test Method Guidelines for GaN HEMT Based Power Conversion Devices. JEDEC’s newest main committee, JC-70, Wide Bandgap Power Electronic Conversion Semiconductors, developed this new publication, JEP173, which is available for free download from the JEDEC website.
Tim McDonald, Senior Advisor to Infineon’s CoolGaNTM program and the chair of JEDEC’s JC-70.1 GaN-focused subcommittee joked about the difficulty of devising the test and measurement procedures for RDS(on). “You might ask, ‘You just measure resistance, how hard is that?’ … But its the hundreds of engineering hours, maybe even thousands that go into agreeing on the testing and measurement procedures,” commented Tim.
The JC-70 evolved from GaN Standards for Power Electronics Conversion Devices Working Group (GaNSPEC DWG).
JEP173 discusses a fundamental need of the users of GaN power FETs, namely a procedure for the consistent measurement of drain-to-source resistance in the ON-state RDS(on) that encompasses dynamic effects. These dynamic effects are characteristic of GaN power FETs, and the value of the resulting measured RDS(on) is method dependent.
According to the JEP173 document, in ON-state operation, Gallium Nitride (GaN) lateral power High Electron Mobility Transistors (HEMTs) conduct charge via a two-dimensional electron gas (2DEG). As a result of the different stress conditions that the device faces during power electronic switching, some charge may get trapped in particular regions of the transistor. This trapped charge results in a transient increase in ON-resistance when operated in a switching environment, and it is referred to as dynamic ON-resistance. An increase in dynamic ON-resistance results in higher power loss, thereby decreasing overall system efficiency.
JEP173 describes the procedures for measuring and calculating dynamic RDS(on). “JEP173 demonstrates how quickly the GaN industry came together to address this important topic and begin to establish standards across suppliers for datasheet, qualification, and test methods,” noted Stephanie Watts Butler, technology innovation architect at Texas Instruments and the chair of JC-70. “The release of JEP173 will help accelerate industry-wide adoption of GaN by ensuring consistency across the supplier base.”
Tim was also impressed with how quickly the different companies agreed on the testing and measurement procedures in the test method guidelines. “It was probably a record,” he said, comparing it to other industry guidelines which typically take many years to develop and agree upon.
The JC-70.1 subcommittee is made up of three task groups, the Reliability Group, the Testing Group, and the Datasheet parameters Group. “Strong commitment from the committee members was required to complete this work to set up universal standards to help advance the adoption of wide bandgap (WBG) power technologies,” noted Tim. “Our Task Groups are diligently making progress on other key GaN and SiC guidelines in the areas of test, reliability, and datasheets.”
The three groups work together to create guidelines for test and characterization methods, reliability & qualification procedures, and datasheet elements and parameters. In the case of dynamic RDS(on), the Reliability Group examines charge trapping and the resulting transient reduction in electron concentration. The Datasheet Group looks at how to account for the transient behavior of RDS(on) given that the standard static value of RDS(on) is insufficient. The Test Group figures out how to test and measure dynamic RDS(on) including consideration and documentation of all of the related factors that need to be set for a consistent measurement. The Test methods Group, for example, proposed to document key relevant test parameters such as applied voltage, the delay time between applied Vds and measurement, and most importantly answered the question, “How do you measure dynamic RDS(on)?”
Beyond dynamic RDS(on), JC-70.1 has other GaN failure modes and mechanisms in its planned work that includes TDDB (time dependent dielectric breakdown) and switching SOA (safe operating area).
Established in October 2017 with twenty-three member companies, JC-70 is now comprised of over fifty member companies. Global multinational corporations and technology startups from the US, Europe, Middle East, and Asia are working together to bring to the industry a set of standards for reliability, testing, and parametrics of wide bandgap power semiconductors. Committee members include industry leaders in power SiC and GaN semiconductors, as well as potential users of wide bandgap power devices, and test and measurement equipment suppliers. Technical experts from universities and national labs also contributed input into the new JEP173 guideline.
JEDEC invites interested companies worldwide to join the organization to participate in this important standardization effort. The JC-70 committee plans to hold four committee meetings in 2019, including a meeting co-located with APEC on March 18. Interested parties are encouraged to contact Emily Desjardin at [email protected].