With the increased focus on efforts to protect the global environment, power semiconductors, which are the main power electronics products, are becoming increasingly important. Using 6th-generation IGBT V-Series technology, Fuji Electric has developed and commercialized high voltage, large capacity power modules that are capable of operating at high temperatures. As post-silicon technology for the next generation, we are pursuing the development of devices that utilize wide band gap semiconductor material and the development of superjunction MOSFETs. Additionally, MOSFETs designed for applications in outer space and used in the Japanese experimental module known as“Kibo” attain high reliability and low loss, while ICs designed for use in power supply control achieve low noise and energy savings. Exhaust system pressure sensors for use in automobiles and control ICs for use in hybrid vehicles have been newly commercialized.

Systems for popular hybrid vehicles are increasingly required to provide higher system output while havng a smaller size. In response, IGBT and diode chips are requested to support higher current densities and double-sided cooling structures. Fuji Electric has developed a chip which is constructed such that a Ni-plating electrode is formed on its surface electrodes. 2nd-generation IGBT chips feature an optimized surface trench cell structure, and employ a new field stop structure. Diode chips incorporate an optimized anode layer structure and utilize FZ wafers to improve forward characteristics and improve chip reliability. These improvements make it possible to reduce IGBT and diode chip sizes, increase system output, and facilitate miniaturization.

The Fi009 has been developed as a dedicated IC for driving IGBTs used in the power conversion systems of gasoline hybrid vehicles. This IC integrates a 15 V drive for IGBTs and protective functions (for overheat, overcurrent, supply voltage drop and soft shutdown) into a single chip using fine process rules to achieve greater versatility than conventional chips. This IC contributes to the stable operation and prevention of burnout of IGBTs at the time of abnormality, and to systems miniaturization. The package is a lead-free compliant SSOP-20, It ensures high reliability which is withstanding temperatures of up to 175 ˚C.

Fuji Electric has developed a 3.3 kV-1.2 kA IGBT module in response to market needs for inverters suitable for industrial and vehicle applications. The package of the newly developed module incorporates IGBT high-power module technology. Compared to previous modules, internal inductance has been reduced by 33% and the current flow to chips on each isolation substrates shows good uniformity. Power cycle tests were implemented with this module, and sufficient durability was verified. 3.3 kV-1.5 kA and 3.3 kV-0.8 kA IGBT modules are also being developed to expand the product lineup.

The market for power supplies, used in medical applications such as MRI and X-ray equipment and in welding and plasma cutting equipment, has expanded in recent years. The switching frequency of these devices is in the range of 20 to 50 kHz. High-speed IGBT modules have been developed for use at this high switching frequency. Lower switching loss has been achieved by controlling the doping level of the p-layer on the rear face of the IGBT chip, shrinking the cell pitch interval on the front face, and optimizing the trade-off relation of the FWD chip. Also, the use of a package that provides improved heat dissipating characteristics helps to suppress the temperature rise of the chip and enables high-speed switching.

Fuji Electric is developing a series of products that use the latest generation “V-Series” IGBTs. V-Series IGBT modules realize lower chip loss and improved package heat dissipation to achieve a smaller IGBT module size and higher power density. The chip and package characteristics have also been improved to enhance reliability and guarantee the maximum temperature of 175 ˚C. For these high power density and highly reliable V-Series IGBTs, Fuji Electric has developed new packages, such as a large capacity 2-in-1 package and a small sized PIM (Power Integrated Module) package. The product lineup will be expanded up to 1,700 V.

Fuji Electric has developed a series of intelligent power modules for industrial applications, known as V-Series IPMs. This product combines high-performance 6th-generation V-chip technology for the IPMs with a new control IC to realize lower loss and a smaller package size. The short-circuit protection function was made to operate at faster speeds and the trade-off relation between conduction loss and short-circuit withstand capability was improved to reduce switching loss. Additionally, the new control IC and the package were optimized to reduce turnon loss and improve radiation noise characteristics. In addition to the conventional protection functions, a new function that outputs different alarm pulse widths for each alarm factor is also provided. Ground-fault protection can also be provided even in a small package.

600 V-class superjunction (SJ) MOSFETs (package: TO-220) with a maximum on-resistance of 0.16 Ω have been fabricated by using multiepitaxial growth technology which has an excellent capability for controlling the doping concentration. By optimizing the doping concentration in the SJ structure, the fabricated SJ-MOSFET achieves an approximate 70 % reduction in specific on-resistance compared to that of a conventional MOSFET“SuperFAP-E³.”This is the industry’s highest level of specific on-resistance, and its value exceeds the theoretical limit for conventional MOSFETs. The avalanche withstand capability of the fabricated SJ-MOSFET has been also improved over the rated current by optimizing the doping profile of the SJ structure in the depth direction and the thickness and resistivity of the n-buffer layer.

We have developed highly reliable and radiation-hardened power MOSFETs for use in outer space applications in satellites and space stations. The largest difference between these newly developed Rad-Hard Power MOSFETs and general-use MOSFETs is that they have excellent durability against high energy charged particles and ionizing radiation. To provide increased durability, electrical characteristics had been sacrificed in the past. With this device, however, to provide durability against high energy charged particles, a drift diffusion model was modified so as to enable simulation of the mechanism. A power MOSFET designed for use in outer space applications and having the world’s top level performance is realized by providing a thick epitaxial layer with low specific resistance as a countermeasure to ensure durability against SEB (single event burn-out).

In response to requests for switching power supplies that are smaller in size, have lower loss and higher efficiency and support high temperature operation, we improved the types of barrier metals and the fabrication methods available for high-voltage Schottky barrier diodes (SBD). We developed a 100 V, 120 V, 150 V and 200 V series of ultra-low I_R SBDs that achieve an I_R of less than 1/10th that of conventional SBDs while preventing an increase in V_F. The risk of thermal runaway due to increased reverse loss during high temperature operation is a weakness of SBDs, but this risk has been mitigated. Guaranteed operation at junction temperatures of up to 175 ˚C enables stable operation to be achieved in high temperature environments, and miniaturization of the heatsink enables smaller size and higher density packaging to be realized.

In recent years, requests for lower power consumption and for harmonic regulation have intensified for all electrical products. To meet the United States Environmental Protection Agency’s EPA5.0 standard, which became effective as of July 2009, it is necessary to improve the light load performance of an IC in a power supply. Fuji Electric has been developing switching mode power supply control ICs. These ICs contain an internal start-up element which is effective for reducing the power consumption. In this paper, we introduce Fuji Electric’s FA5592 series of current mode PWM-ICs that comply with the EPA5.0 standard. This series features an internal 750 V start-up element, improved frequency- lowering performance when operating under light load conditions, lower EMI noise, and enhanced protection functions.

Power supply units are requested to be smaller in size, consume less standby power, and provide higher efficiency and improved safety. In response to such requests, Fuji Electric has developed an 8-pin voltage mode PWM controller, the main features of which include a maximum power supply voltage rating of 35 V, a low standby power function, a control system power maintenance function for operation at light loads, hiccup function at overload, and a constant current droop function. Because the current drooping characteristic can be obtained with a few external parts, this IC can be used in power supplies for various applications, such as a power supply connected to batteries or other load requiring a constant current characteristic.

With the widespread use of switching converters, harmonic currents have become a problem. As a countermeasure, PFC (Power Factor Collection) circuits are used widely. PFC circuits are strongly requested to be highly efficiency, have a small size, and recently, to have low noise and a low cost. We have developed new continuous current mode PFC-ICs“ FA5610/FA5611” that are housed in a SOP-8 small package and achieve low-noise and high-efficiency operation through our propriety method for distributing switching frequency, and that incorporate measures against noise at startup and during load fluctuations, and measures against output voltage drooping during load fluctuations to improve the ease of use.

Exhaust gas regulations for motor vehicles are becoming stricter year-after-year, and as internal combustion engines are being made more efficient and their exhaust gas reduced, there is increased demand for pressure sensing in the exhaust systems of diesel engine vehicles. Applying a single-chip semiconductor pressure sensor fabricated by a CMOS process, which has been successfully used for manifold pressure measurement, Fuji Electric has developed an exhaust system pressure sensor capable of withstanding an exhaust gas environment containing corrosive substances. The newly developed sensor, in a DIN standard SO₂ gas test, exhibited the ability to withstand corrosion that is more than 2.5 times greater than that of conventional sensors, and is suitable for use in absolute pressure sensing and relative pressure sensing applications.

In power conversion systems that use IGBT modules, the thermal conductivity of the thermal compound utilized is as low as possible. As a result, the compound thickness affects the IGBT chip temperature. This paper describes the effects of the hardness of components and the ingredients of the compound on the spreading ability of the compound and the distribution of stress when tightening with screws. Additionally, in consideration of the stress distribution, we have proposed a metal mask pattern for applying the compound as thinly as possible. As a result, the compound can be applied at approximately 1/3rd the thickness of the conventional application technique.