Vol. 78, No. 1, January 2023

MORI Seiichi

KAWAGUCHI Yusuke / IKEDA Sadao / YAMAMOTO Kotaro / NABA Takayuki

To address the pressing issue of global warming, Japan and many other countries are aiming to realize carbon neutrality by 2050 by achieving net zero emissions of greenhouse gases, which are considered to be the predominant cause of global climate change.

The Toshiba Group is developing and continuously improving the performance of a broad range of device and material products that improve the energy efficiency of various systems in order to reduce carbon dioxide (CO₂) emissions. Through these efforts, we are contributing to the achievement of carbon neutrality by 2050.

KAGANOI Keisuke / SUZUKI Miwako / KANEKO Atsushi / SHIMAMURA Shinya

Data centers and communication base stations have recently become one of the largest consumers of electric power as a result of the ongoing increases in the volume of data communication and storage capacity. Reduction of the power consumption of power devices in the power supplies of such facilities is therefore an issue of vital importance in the context of achieving carbon neutrality.

Toshiba Electronic Devices & Storage Corporation is engaged in activities to realize loss reduction in power metal-oxide-semiconductor field-effect transistor (MOSFET) products. Reduction of the reverse recovery loss is essential in order to reduce the total loss of power MOSFETs. We have now released a 150 V power MOSFET fabricated using the U-MOSX-H process and a 650 V power MOSFET fabricated using the DTMOSVI process. In addition to improvements in the conventional methods for achieving smaller on-resistance (R_on) and smaller gate charge, these devices provide a substantial improvement in reverse recovery characteristics, achieved by the optimization of lifetime control techniques, in order to enhance the efficiency of power supplies used in data centers and communication base stations.

IWAKAJI Yoko / GEJO Ryohei / YAMAKAWA Yuji / SAKANO Tatsunori

In recent years, insulated gate bipolar transistors (IGBTs) have become widely used in a variety of products ranging from home appliances to power conversion equipment as high-voltage and low-loss power devices.

In order to achieve a carbon neutral society, Toshiba Electronic Devices & Storage Corporation has been developing multigate control techniques for IGBTs with the aim of further reducing their total power loss. Multigate control makes it possible to drastically reduce switching losses while keeping conduction losses low. From the results of experiments using prototype devices, we have confirmed that multigate control achieves reductions in turn-off loss (E_off) and turn-on loss (E_on) by 27% and 50%, respectively, in the case of 1 200 V-class IGBTs, as well as reductions in E_off, E_on, and reverse recovery loss (E_rr) by 24%, 18%, and 32%, respectively, in the case of 4 500 V-class reverse-conducting injection-enhanced gate transistors (RC-IEGTs), compared with the conventional single-gate controlled devices of each type.

FURUKAWA Masaru / SHIMIZU Yasuhiro / KOBAYASHI Masakazu

Although silicon carbide (SiC) holds promise as a key semiconductor material for realizing power metal-oxide-semiconductor field-effect transistors (MOSFETs) with higher voltage and lower loss compared with Si MOSFETs, problems regarding the reliability of SiC MOSFETs are a critical issue.

Toshiba Electronic Devices & Storage Corporation has responded to this situation by developing SiC MOSFETs in which reliability is improved by means of an embedded Schottky barrier diode (SBD). However, the embedded SBD reduces the area available for the functioning of the MOSFET, thereby degrading the performance of SBD-embedded SiC MOSFETs. To resolve this issue, we have now developed third-generation SBD-embedded SiC MOSFETs that succeed in achieving a balance between improvement of reliability and reduction of switching loss due to the adoption of a newly designed device structure.

KANIE Sozo

Technology computer-aided design (TCAD) simulators for silicon carbide (SiC) power semiconductors have not yet been sufficiently developed compared with those for silicon (Si) power semiconductors. For example, the behaviors of carbon vacancies (VC), which are well known as detrimental point defects in SiC, in fabrication processes including impurity ion implantation and activation annealing are not yet modeled in commercial TCAD simulators. In addition, although models respectively simulating the behavior of VC in the relatively low-temperature oxidation process and in the ultrahigh-temperature activation annealing process have been proposed, they have been unable to reproduce each other’s experimental results.

Toshiba Electronic Devices & Storage Corporation has responded to this situation by developing a universal simulation model to predict the behaviors of interstitial carbon (Ci) and VC in SiC over a wide temperature range. By taking the capture and release of Ci due to defects in the SiC substrate into account, we have confirmed that the results calculated by this model are in good agreement with the results obtained experimentally.

HAYASHI Tsuneyuki / TODA Shuji / WADA Hiroshi / TAKAHASHI Yuichi

It is necessary for electronic equipment to provide reduced power consumption, increased power density, and improved power source efficiency toward the achievement of carbon neutrality.

The Toshiba Group has developed the TCK42xG series N-channel metal-oxide-semiconductor field-effect transistor (MOSFET) gate driver integrated circuits (ICs), which realize both compactness and low switching loss, focusing on load switching circuits for power management blocks. The TCK42xG series ensures low switching loss even in 100 W-class power supplies by incorporating our proprietary control mechanism for efficient MOSFET operation while reducing power consumption. In addition, with its ultracompact package, the TCK42xG series makes it possible for electronic equipment to be downsized.

WATANABE Hiroki / SAKAGUCHI Shoichi

In line with the changes taking place in energy policies accompanying the worldwide movement toward decarbonization to tackle the issue of climate change, the electrification of various systems for automobiles aimed at enhancing their environmental performance, as typified by the electrification of automobile power sources with the advent of electrified vehicles (xEVs), has recently been expanding in the automobile industry. The installation of electric motors, as key components supporting such electrification, has consequently been rapidly increasing. This, in turn, has given rise to the need for the electronic control units (ECUs) that drive such motors to be more compact and lightweight and to provide higher efficiency.

Under these circumstances, Toshiba Electronic Devices & Storage Corporation is developing the SmartMCD™ series integrated motor control drivers (MCDs) equipped with a built-in microprocessor fabricated employing an analog process using a fifth-generation platform for mixed-signal integrated circuits (ICs). The SmartMCD™ series makes it possible to efficiently drive electric motors while reducing the size and weight of the ECU board, with all of the necessary functions integrated in one chip.

ITO Kazuyuki / KIKUCHI Takuo / ODA Tatsuhiro / NISHIGUCHI Toshifumi

The Toshiba Group has developed a simulation technique to predict on-resistance (R_on) in trench type silicon (Si) power metal-oxide-semiconductor field-effect transistors (MOSFETs), based on the results of estimation of the membrane stresses inside the device obtained using the measured wafer warpage values and multiscale stress analysis.

We have applied this technique to a prototype device, and confirmed that it can predict the stress distribution of the Si substrate adjacent to the trench with a margin of error of within 10% and the R_on with a margin of error of within 3%. Furthermore, we have also calculated the stress distribution in each manufacturing process and clarified the processes in which stress control is important so as to realize a design with the appropriate R_on. This technique is expected to reduce backtracking in device development, leading to improvements in design efficiency.

TAKAYANAGI Yoshiyuki / YAMAJI Yuto

The improvement of work efficiency at manufacturing sites is essential in order to enhance productivity, operating rates, and safety. On the other hand, methods to visually analyze business operations using images captured by handheld cameras often lead to decreased efficiency due to the considerable time required to manually check such images.

Toshiba Lighting & Technology Corporation has been supplying camera-equipped lighting fixtures that can be installed simply by replacing existing lighting fixtures. In addition, we have now developed a video analysis system that can analyze images captured by these camera-equipped lighting fixtures via a cloud system, applying a proprietary human detection artificial intelligence (AI) technology to process images from the ceiling viewpoint. This system enables users to efficiently promote various improvement activities at manufacturing sites, including safety management, analysis of workflow lines, and visualization of the time required for each operation, or so-called takt time.