News

# Advanced Materials to Lead Power Electronics Tech in 2013

December 26, 2012 by Jeff Shepard

Silicon-carbide (SiC) and gallium-nitride (GaN) will be challenged by new contenders in the coming year. That's not to say that SiC and GaN power devices will not gain increasing market adoption, they will. But other semiconductor materials such as aluminum-nitride (AlN), gallium-arsenide (GaAs), advanced thin-film magnetic materials, and more, will emerge as the "next big things" in 2013. The emergence of more new materials will be accompanied by the emergence of "new" companies such as Sarda Technologies, HexaTech, Inc ., Ferric Semiconductor, and others.

Sarda is focused on the development of advanced power switches for portable devices. Sarda will come out of stealth mode when they present a paper at the IEEE Applied Power Electronics Conference in March. The paper will be titled, "The gFETT Switch: A New Low-Voltage High-Speed GaAs HEMT for Switching Applications," the authors are Robert White, Anthony Marini and Greg Miller.

Based in Durham, North Carolina, Sarda is focused on reducing power loss in <20V dc-dc voltage converters. Sarda's technology results from the use of GaAs to enable a radical reimaging of the basic field effect transistor geometry and enables the switches used in converters to achieve ultra-low power loss and very-high switching frequencies. The Sarda team is led by semiconductor industry veterans Bob Conner and Jim Vorhaus, both of whom have significant Fortune 500 company and startup experience.

In February of last year, TriQuint Semiconductor announced that its Foundry Services division was supporting Sarda to bring a new line of high-efficiency converter switches to the global marketplace. This support will allow Sarda to utilize TriQuint's foundry line for the development and production of their product.

In March, Sarda received its first equity funding from IDEA Fund Partners, a venture capital firm providing seed and early stage financing to technology companies throughout the Southeast and Mid-Atlantic regions. Sarda had previously been awarded an NC IDEA grant in the Spring of 2011, receiving funds to assist in the patenting of its technology. During the grant process, Sarda created an advisory board that included NC IDEA Venture Advisor and IDEA Fund Partners Managing General Partner, John Cambier. Sarda is only the fifth NC IDEA grant recipient that has attracted investment from IDEA Fund Partners.

While Sarda is focused on low-voltage power conversion for portable devices, HexaTech is targeting very-high-voltage power switches for emerging applications in the smart grid. Last month, HexaTech, received a $2.2 million award from the U.S. Department of Energy Advanced Research Projects Agency — Energy (ARPA-E) that will enable the development of a new power semiconductor technology for the modernization of the electrical power grid. HexaTech's aluminum-nitride (AlN) technology was identified by the Department of Energy as having the potential to be a transformational, breakthrough technology with significant technical promise, potentially 10X better performance than comparable silicon-carbide devices. Using very low-dislocation-density single-crystal AlN substrates, HexaTech will develop novel doping schemes and contact metals for AlN/AlGaN with high Al content. For power systems and grid-scale power conversion applications, high-efficiency AlN-based power devices are expected to offer a significant reduction in size, weight, and cooling. Dr. Baxter Moody, Director of Engineering, said, "This contract marks the beginning of a technological leap in device performance and efficiency for power semiconductors. The development will enable a significant step toward producing 20 kV AlN-based Schottky diodes (SBD, JBSD) and transistors (JFET, MOSFET). The ARPA-E contract has opened the door for the material development and research to demonstrate AlN high-voltage, high-efficiency power conversion capability." Power semiconductor devices at this level are not currently available on the market. Experimental devices based on silicon carbide (SiC) technology are currently being developed. Compared to SiC technology, it is expected that Aluminum Nitride will enable power electronics with a 10X improvement in performance. Based on the wide bandgap material properties of AlN, the critical field is 6X larger, the on resistance will be lower, and the resulting power device area will be smaller for a comparable power level. This is expected to be a transformational technology that will revolutionize the power distribution grid. In contrast with HexaTech and Sarda which are both developing advanced power semiconductors based on new materials,Ferric Semiconductor was founded by a team of engineers and materials scientists out of Columbia University, with the goal to develop integrated inductors in CMOS technology for use in advanced on-chip voltage regulators. The company's objective is to commercialize power converters utilizing inductors with precisely engineered laminations of high-permeability magnetic material. This is expected to enable a significant improvement in power converter current density and subsequently enable power supplies for microprocessors and systems on chip (SoCs) to be down converted in the same package, or even on the same die. This new class of integrated voltage regulators (IVRs) will provide as much as 20% reduction in total power consumption for digital ICs by reducing resistive losses and enabling improved power management techniques. Voltage regulators utilizing integrated magnetic thin-film inductors are expected to have cost and performance advantages over the other voltage regulator products that are commercially available. Therefore this technology is expected to have a sizeable impact on the$10 billion worldwide voltage regulator market. Furthermore, the integration of magnetic materials with CMOS will facilitate advances in other magnetic based systems, such as magnetic filters, sensors and imagers. Likewise, the experience gained from commercializing a magnetic material process module with CMOS technology will lower the technological barriers for other forms of heterogeneous integration.

Enpirion, Inc. has also developed a new magnetic alloy, which enables the miniaturization of passive magnetic components and their assimilation with integrated circuits at wafer level. So-called wafer level magnetics (WLM) present a leap in traditional technology, which will take magnetic components from their 3-dimensional discrete shape to a planar 2-dimensional thin-film form that can be deposited with standard wafer processes on top of CMOS wafers.

Enpirion developed a turnkey process module, which features low cost of ownership plating equipment to deposit FCA on 6 inch or 8 inch wafers. The technology has been successfully transferred and embedded in a volume wafer production facility earlier this year, where Enpirion is producing the world's lowest cost, noise sensitive, low power POL dc-dc converters, the 1 Amp EL711 and the 1,5 Amp EL712, the industry's first Power System-on-Chips based on electroplated wafer level magnetics.

Enpirion's WLM technology is fully qualified for full-scale mass production in a high volume foundry and enables the industry's first ever Power System-on-Chips based on electroplated wafer level magnetics. Developed with a view to achieving monolithic Power System-on-Chips, the WLM technology can be easily transferred to other micro-magnetic applications, for example micro-transformers for signal isolation, micro-electromagnets for life sciences, integrated magnetic sensors for navigation and PMICs for portable consumer applications.

"Increasing the switching frequency allows the use of smaller inductors utilizing electroplated WLM materials that can be post-CMOS processed. We developed an amorphous Fe-Co based alloy called FCA, which is capable of operating at frequencies higher than 20MHz with minimal attenuation of magnetic properties," explains Dr. Trifon Liakopoulos, Director of MEMS technology and Enpirion's co-founder. "With wafer electroplating methods, it is possible to cost-effectively deposit photo-lithographically defined FCA magnetic cores on silicon wafers."

FCA has high resistivity, low coercivity and maintains high effective permeability at frequencies higher than 20MHz. FCA's high magnetic saturation makes it suitable for use as single or multiple layers in power circuits, where it is compatible with flip-chip, wire-bonding and solder re-flow packaging methods.

Also striving to achieve the ultimate in miniaturization of dc-dc converters, Renesas had adopted a wafer-level chip size package to achieve POL devices that can supply large amounts of current in a compact form factor making it possible to reduce the IC's internal wiring resistance and package wiring resistance to an absolute minimum. For example, in the RAA207701GBM, which has a maximum rated current of 10A, the package size is an extremely small 2.7 x 3.4 mm, which corresponds to a roughly 75 percent reduction in package size compared to earlier Renesas SiP POL products. Furthermore the thermal resistance from the package surface to the chip junction area is an extremely low 1Ω/W, allowing a high thermal dissipation design when used with a heat sink and air flow.

In these new POLs, Renesas is reacting to two changes in POL market. The first is the requirement for reduced power consumption to achieve an energy-saving society, and the second is the increasing diversity in supply voltages required by increasingly highly functional semiconductor products such as microcontrollers (MCUs) and SoC devices.

To satisfy the first requirement, the new RAA20770X devices perform high-efficiency power conversion during normal load and - typically 90 percent of the time - also execute the frequent transitions to low-power mode quickly. As a result, they reduce overall system power consumption and help enable an energy-efficient society.

To satisfy the second requirement, although mounting area is spreading according to electric source increasing, the RAA20770X devices achieve a size reduction of about 75 percent compared to earlier Renesas products, featuring an ultra-miniature wafer-level chip size package that is essentially the same size as the chip itself. Furthermore, since no wired connections are required within the package, resistance in the wiring is reduced, which contributes to more efficient voltage conversion. The RAA20770X Series represents the first devices with this level of integration in this small a package size.

These and other advanced power conversion materials, devices and technologies will be discussed at the first-annual Darnell Energy Summit (DES '13) to be hosted September 9-13 in Dallas, Texas. DES '13 will be a combined event featuring the Tenth Darnell Power Forum (DPF '13) plus the Fifth Green Building Power Forum (GBPF '13) plus the Fourth Smart Grid Electronics Forum (SGEF '13). With a single registration, delegates can attend any sessions of interest during these simultaneous leading-edge events. You can find details here.