ECSEL-prosjekt PowerBase Enhanced substrates and GaN pilot lines enabling compact power applications

Eltek's target was to investigate how GaN transistors could be used to raise power conversion efficiency to 98%. We tested the totempole topology for the Power Factor Correction (PFC) step because GaN allowed us to use this topology. We have never been able to use before of slow internal diode in the conventional Si MOSFET. The new totempole topology allowed us to develop and industrialize the Super High Efficiency (SHE) rectifier series with 98% effiecieny. With this product, we have reduced the power loss in rectification with 50% compared to state of the art high efficient rectifiers. The rectifiers were tested and validated under very tough conditions to identify and correct issues. We have now installed thousands 3kW SHE rectifiers with telecom operators in Asia, Africa and Russia. After 9 months of field experience, we have not received a single field failure report. Populærvitenskapelig framstilling UiO PowerBase (Enhanced substrates and GaN pilot lines enabling compact power applications) project has consolidated 39 partners from 9 countries to work jointly towards advancing current power semiconductor technologies. This includes the development of new substrate materials for power semiconductors, the improvement of manufacturing efficiency by innovative automation, the setting up of a GaN compatible chip embedding pilot line and demonstration in leading compact power application domains. A two-fold impact is expected from the project - in providing a strong European source for GaN power devices, and in contributing to compact, efficient and cost-competitive power electronic systems employing fast switching GaN devices. The project addresses several well defined objectives, among which ?Cost-effective high volume manufacture capable 300 mm technology for extreme silicon substrates? is organized as a separate work package (WP2) and delegated to a group of partners involving the University of Oslo team possessing unique expertise in point defects in silicon. The tasks assigned to UiO team primary focus on advanced chemical, electrical and optical characterization of the extreme silicon substrates employing a variety of complementary analysis techniques (SIMS, PL, FTIR, Hall-effect, CV, DLTS and ADSPEC). The measurements of critical parameters, resistivity, and oxygen content are considered as a key prerequisite for optimizing wafer fabrication. In the framework of technology transfer to 300 mm Si crystals, two extreme cases of Czochralski-grown (Cz-Si) material have been considered: i) phosphorus (P) doped ultra-low resistivity substrates aimed for use in power MOS devices, and ii) crystal defect optimized substrates with low-oxygen content aimed for use in IGBT devices (oxygen precipitates and thermal donors have detrimental effect on device operation). The material properties were analyzed both along and across these large diameter ingots with the variations monitored by establishing axial/radial distributions. In general, the ultra-low resistivity P doped 300 mm diameter Cz-grown Si wafers are found to demonstrate excellent results with high electrical activation of the P atoms at room temperature and also high electron mobility yielding a resistivity of only 1.1 m?cm (or below). The electrical conductivity is metallic like with only minor temperature dependence. Electrical and optical characterization of high resistivity and low-oxygen 300 mm diameter Cz wafers and 200 mm Float zone (Fz) control wafers, aimed for high-voltage and high-power devices, reveal the presence of carbon-oxygen defects acting as charge carrier recombination centers. This holds for both Cz and Fz types of wafers. These defects are found to limit the minority carrier lifetime in the wafers and have an adverse impact on the device performance. Overall, the combined chemical, electrical and optical studies have provided important feed-back information to other partners for optimizing the growth process of the new 300 nm Cz-wafers, and also ensured that critical material characteristics were indeed met before proceeding further with coating Si wafers with GaN and creating power components. All these activities have contributed to the ultimate success of the Powerbase project.

To expand the limits in current power semiconductor technologies the project focuses on setting up a qualified wide band gap GaN technology Pilot line, on expanding the limits of today's silicon based substrate materials for power semiconductors, improving manufacturing efficiency by innovative automation, setting up of a GaN compatible chip embedding pilot line and demonstrating innovation potential in leading compact power application domains. PowerBase is a project with a vertical supply chain involved with contributions from partners in 7 European countries. This spans expertise from raw material research, process innovation, pilot line, assembly innovation and pilot line up to various application domains representing enhanced smart systems. The supporting partners consist of market leaders in their domain, having excellent technological background, which are fully committed to achieve the very challenging project goals. There are two Norwegian partners in the project: Eltek will contribute to exploiting and testing the new GaN technologies in rectifiers for the telecom sector in Work Package 7 on Compact Power Applications. The University of Oslo (UNI Oslo) will contribute to Work Package 2 on Extreme silicon base materials for 300mm power devices. UNI Oslo will contribute with advanced spectroscopic characterization of both high-resistivity and low-resistivity Silicon base material (300 mm diameter) for analysis and control of device-performance-limiting defects/impurities with respect to carrier lifetime, doping uniformity and carrier mobility. Merk at formell prosjektstart er 01.05.2015. Av tekniske årsaker måtte startdato settes til tidligst 21.11.2015 i denne søknaden.