Tomoyoshi Kushida

A 600 V 200 A low loss high current density trench IGBT for hybrid vehicles

We developed a new low loss high destruction immunity 600 V 200 A trench IGBT for hybrid vehicles. In order to secure high destruction immunity at high current density use caused by chip shrink, we designed a process and a cell on the basis of results of both simulation and 2.5 mm square TEGs (Test Element Groups) experimental results. A 4 um trench pitch, punch-through wafer structure, and local lifetime technology are employed. As a result, the developed IGBT shows an on-state voltage drop of 1.55 V, a fall time of 800 ns, an avalanche capability of over 1 J (at R.T.), and a short circuit immunity of over 40 us. The IGBT is fitted with both a temperature sensor and a current sensor in order to avoid chip failure.

A fast and soft recovery diode with ultra small Qrr (USQ-Diode) using local lifetime control by He ion irradiation

This paper presents an ultra small reverse recovery charge Qrr diode (USQ-Diode) for Insulated Gate Bipolar Transistor (IGBT) modules. The USQ-Diode has a thin p-layer anode with low impurity concentrations, p+ stripe anodes, and lifetime control by He ion irradiation. By employing the thin p-layer anode, the injection of holes into the n-layer as minority carriers was significantly reduced near the pn junction. By using the He ion irradiation, crystal defects for lifetime control were localized near the pn junction. With the combined effects from both the reduced injection of holes and the local lifetime control by the He ion irradiation, as compared to the conventional pn diode, the USQ-Diode realized such superior characteristics as 1/5 times smaller reverse recovery charge and 0.2 V lower forward voltage drop.

A He-irradiated IGBT with a shallow p-base and shallow FLRs

A trade-off between a low forward voltage and fast switching time is a very important characteristic for an insulated gate bipolar transistor (IGBT) that is used in applications such as inverters for motor control. A trench-IGBT has a very good trade-off but has a high cost because of the complicated structure. This study presents our new development of a 600 V planar-IGBT that has a trade-off characteristic comparable to that of a trench-IGBT. This has been realized by employing a device structure with a shallow p-base and shallow FLRs, and by using local lifetime control through He irradiation.

A 60 V BiCDMOS device technology for automotive applications

A new 60 V BiCDMOS device technology has been developed for specialized automotive applications. This technology merges a 7 V 2 /spl mu/m CMOS process and a 7 V bipolar transistor process with a 60 V DMOS process. Bipolar transistors for 18 V and 35 V are also available without any additional process steps. In addition, it includes a multithickness metal process which permits the use of a thin patterned metal layer over the signal parts for high packing density and a thick metal layer over the power parts for low voltage drop. With the availability of this multithickness metal process, chip size can be reduced.

Electrical Characteristics of AlGaAs/GaAs Heterostructures With a Pair of 2-D Electron and Hole Channels

To make power devices with lower losses and higher power capabilities, superjunctions (SJs), based on GaN, GaAs, and related materials, are attractive. It is because they have higher breakdown fields than Si and allow the use of heterostructures, where highly conductive layers of 2-D electrons and holes can be formed. As a step toward such SJ devices, we have fabricated AlGaAs/GaAs four-terminal devices in which a pair of electron/hole channels is embedded. Transport properties of electrons and holes are studied by operating the devices as FETs in which the conductance of one channel is controlled by using the other as a gate. Current-voltage and capacitance-voltage characteristics between the two channels are evaluated by operating the devices as p-n diodes. Measured characteristics are examined by comparing them with device simulations with a focus on the carrier depletion process in each channel.

Photocurrent and photoluminescence characteristics of AlGaAs/GaAs double-heterostructures with a pair of two-dimensional electron and hole channels

AlGaAs/GaAs/AlGaAs double-heterostructures having two-dimensional electron and hole channels at the respective interfaces are studied by measuring their photocurrent and photoluminescence characteristics. Under the weak photoexcitation, it is found that photo-generated electrons and holes are driven by a built-in electric field between the two channels and flow out mostly as a photocurrent to the respective electrodes, making the photoluminescence negligibly small. When the excitation reaches a certain level, some of photo-generated electrons and holes accumulate in each channel and weaken the built-in field, leading to an exponential increase in photoluminescence or the radiative recombination of electrons and holes. When the excitation gets strong, photo-generated carriers are lost mostly in the form of photoluminescence, resulting in the saturation of photocurrent. A theoretical model to explain these findings is presented. A possibility of using this type of study to clarify operating mechanisms of su...