Power Device and Thermal Metrology

Makers of power semiconductor devices want their products to handle higher voltages and boast better efficiencies. Goods and services that benefit from these advancements are power converters for computers, electric cars, alternate/clean power generation, and high power transmission and distribution. New semiconductor materials and devices to address these needs are rapidly being developed, but with these new materials and devices come new requirements for characterizing the performance and reliability of the resulting fabricated devices. At NIST, the Power Device and Thermal Metrology project is developing new electrical and thermal measurement methods, and the equipment to make those measurements. Their work has and will continue to play a major role in the growth of the power semiconductor and power electronics industries.

Switch-mode power conversion, using power semiconductor devices and other passive power electronic components, provides the means to convert power from one voltage to another, to convert between direct current (DC) and alternating current (AC) power, and to control motion by delivering electrical power to motor winding or mechanical actuators. As power semiconductor technology has evolved from slow low-voltage low-power devices to today’s fast high-voltage high-power devices, switch mode power conversion has become pervasive and essential in all electrical and electronic equipment except for in the most extreme conditions such as very high voltage, high temperature, and cost sensitive products.

NIST has provided the theoretical foundation, measurement methods, and equipment that led to the development and rapid adoption of the most widely used power semiconductor device known as the Insulated Gate Bipolar Transistor (IGBT). As the IGBT has reached its fundamental limits, NIST work has focused on devices made with new wide-band-gap semiconductor materials such as Silicon-Carbide (SiC) that are beginning to replace conventional devices made with Silicon. Power semiconductor devices made with SiC enable operation at higher voltages, higher speeds, and higher temperatures. These new devices are necessary to meet the nation’s energy and defense priorities.

For example, energy independence, increased capacity and stability of the power grid, and zero-emission carbon-neutral power generation for electricity and transportation are urgent national priorities. Achieving these priorities requires incorporating alternate/clean energy sources, such as solar, wind and clean coal fuel cell generators. However, these power sources produce low voltage unregulated DC power or AC power that is not synchronized with the power grid. High-megawatt power conditioning systems (PCS) are thus required to enable efficient and reliable operation of the power sources and to provide the high voltage regulated/synchronized AC power meeting requirements for power grid connectivity. NIST is leading U.S. Department of Energy efforts to determine the technologies that must be developed to meet the PCS goals for power generation and the power grid. For example, NIST has identified a way to substantially reduce cost and improve the performance and efficiency of high-megawatt PCSs.

Advanced PCS technologies are also required to meet the nation’s defense priorities such as more electric combat aircraft, advanced naval ship power distribution systems, and secure power grids for army main and forward bases.  NIST is also playing a major role in a U.S. Defense Advanced Research Projects Agency (DARPA) program that is spearheading the development of high-voltage, high-frequency (HV-HF) SiC technology. NIST is the lead metrology development and deliverable evaluation laboratory for this program and has played a major role by providing the data, theoretical models, and analysis necessary to develop the HV-HF power semiconductor device modules and switch mode power conversion system. The goal of this program is to develop a switch mode power conversion system for future naval aircraft carrier power distribution that will providing transformational improvements in control, functionality, efficiency, and weight.

Plug-in hybrid and electric propulsion vehicles are important approaches to meeting our nation’s energy and transportation priorities, by transitioning personal vehicles from petroleum-based combustion engines to alternate non-petroleum-based energy sources. To address these needs, NIST is working with the U.S. Department of Energy to establish the metrology, data, and analysis required to advance power conditioning system technologies in these vehicles.

The Power Device and Thermal Management project is addressing a wide range of key issues from methods to monitor material degradation in SiC power semiconductor devices to methods to avoid development of hot spots in microprocessors.  The project has pioneering electrical and thermal measurement methods for HV-HF devices and advanced thermal metrology for high-density integrated circuits and has transferred these measurement systems to industry.