Tsutomu Hosoda

600 V JEDEC-qualified highly reliable GaN HEMTs on Si substrates

In this paper, we demonstrate 600 V highly reliable GaN high electron mobility transistors (HEMTs) on Si substrates. GaN on Si technologies are most important for the mass-production at the Si-LSI manufacturing facility. High breakdown voltage over 1500 V was confirmed with stable dynamic on-resistance (RON) using cascode configuration package. These GaN HEMT on Si based cascode packages have passed the qualification based on the standards of the Joint Electron Devices Engineering Council (JEDEC) (1-5) for the first time. High voltage acceleration test was performed up to 1150 V. Even considering most conservative failure mechanism, mean time to failure (MTTF) of over 1×107 hours at 600 V was predicted at 80°C. Additional conclusion is that conventional packages such as TO-220 are still suitable for high speed circuit application without using a specific gate driver. Ultimately GaN will significantly reduce conversion losses endemic in all areas of electricity conversion, ranging from power supplies to PV inverters to motion control to electric vehicles, enabling consumers, utilities and governments to contribute towards a more energy efficient world.

Effects of line size on thermal stress in aluminum conductors

The authors evaluate the aspect ratio dependence of thermal stress distribution in passivated aluminum conductors on line width and thickness as directly determined using X-ray stress measurement. Measured stresses are compared with the results of analytical and numerical simulations. It was found that they differ significantly. This difference is ascribable to the dependence of the yield stress on the line width and thickness. The yield stress increases with decreasing width and thickness. The dependence of aluminum lifetime on the width and thickness of aluminum conductors was also evaluated. This dependence is discussed with a diffusional void growth model. The experimentally obtained lifetime is well described by this model with directly measured stress.<<ETX>>

Commercialization and reliability of 600 V GaN power switches

The reliability of 600 V GaN power switches, fabricated in a silicon CMOS foundry, has been demonstrated. JEDEC qualification of cascode packages and the long term reliability of GaN power switches has been estimated for the first and shown to be greater than a million hours. Excellent switched/dynamic on-resistance up to 1000 V and breakdown voltage over 1500 V indicate the suitability of these devices for switching up to 480 V. Detailed data of high temperature reverse bias (HTRB) test is shown. High temperature DC stress test and high voltage off-state stress tests also corroborate the high reliability of these devices. This suite of initial, JEDEC & accelerated stress tests show that GaN-on-silicon power switches are ready for many commercial and industrial applications, would significantly reduce switching losses and system size and will impact all areas of electricity conversion, ranging from tablet chargers to photovoltaic inverters and electric vehicles.

Effects of copper and titanium addition to aluminum interconnects on electro- and stress-migration open circuit failures

Electromigration (EM) lifetimes are determined for pure Al, Al-0.1-wt.% Cu, Al-0.15-wt.% Ti, and Al-0.1-wt.% Cu-0.15-wt.% Ti as a function of the line width. The addition of 0.15-wt.% Ti improves the EM resistance, in which the lifetime increases with decreasing linewidth. The lifetimes of Al-0.1-wt.% Cu are similar to pure Al. The stress migration (SM) open failures are also evaluated. The Ti addition has a deteriorating effect on SM. The Cu addition, however, substantially improves the SM resistance. The simultaneous addition of Cu and Ti improves both EM and SM resistances. >

2.5-kW power supply unit with semi-bridgeless PFC designed for GaN-HEMT

Wide-gap semiconductors such as SiC and GaN have seen widespread increase in interest as promising materials for use in next-generation power devices. In this paper, we present a 2.5-kW power supply unit (PSU) designed for ICT systems with engineering samples of Fujitsu Semiconductor Ltd. (FSL) s GaN-HEMTs installed in the power factor collection (PFC) circuit. A new PFC circuit specially designed for GaN-HEMT is proposed: a semi-bridgeless design with a synchronous rectification return line. The bridgeless architecture is suitable for high-power and high-efficiency PSUs, and the synchronous rectification is designed to maximize the GaN-HEMT performance. As the GaN-HEMT does not have a body diode, the return current mainly flows through the return diodes in conventional semi-bridgeless PFCs. By applying synchronous rectifiers instead of return diodes, energy loss in the return line can be reduced to about 1/10. In our experiments, a maximum PSU efficiency of 94.3% was obtained with 230-V AC input and 12-V DC output.