Hideo Matsuda

Pressure contact assembly technology of high power devices

The paper describes pressure contact technology applied to high power semiconductor devices. Specific application to multiple chip assembly, particularly IGBT chips, is dealt with, and improved reliability characteristics are demonstrated.

Analysis of GTO failure mode during DC voltage blocking

GTOs suddenly failed without any leakage current increase before the failure event, during DC voltage blocking. From various experiments and the analysis, we have come to the inference that the GTO failure was caused by cosmic-rays at sea level. The failure rate of the improved GTOs decreases by more than one order.

High turn-off current capability of parallel-connected 4.5 kV trench IEGT

An injection enhancement IGBT (IEGT) is a high-power switching device that realizes low saturation voltage by the injection enhancement effect (IE-effect). The experimental results obtained by the IE-effect are presented. The trench IEGTs with 6- and 12-/spl mu/m trench depth were compared with a planar IEGT. These experimental results show that the trench IEGT has a better trade-off relation between saturation voltage and turn-off loss than the planar IEGT. Moreover, the trench IEGT with 12-/spl mu/m trench depth has a better trade-off relation than that with 6-/spl mu/m trench depth. These results prove clearly that the IE-effect improves the trade-off relation. Turn-off characteristics of parallel-connected 4.5 kV trench IEGTs are discussed. The influence of the gate circuit parameters on a turn-off current balance was examined in order to realize high turn-off current capability. It is concluded that the reduction of the gate parasitic inductance is important for uniform turn-off operation. At optimum gate circuit condition, it is shown that the maximum turn-off current increases in proportion to the number of IEGT chips. As a result, a 1300-A turn-off current capability was obtained using nine parallel-connected IEGT chips in an inductive load circuit and without any snubber circuits. In conclusion, the IEGT has a good prospect of replacing the gate turn-off thyristor (GTO) for high-voltage applications, such as motor controls for traction, industrial motor drives, and so on.

High turn-off current capability of parallel-connected 4.5 kV trench-IEGTs

The turn-off characteristics of parallel-connected 4.5 kV trench injection enhanced gate transistors (IEGTs) are discussed. The influence of the gate circuit parameters on turn-off current balance was examined in order to realize high turn-off current capability. It is concluded that the reduction of the gate parasitic inductance is important for uniform turn-off operation. At the optimum gate circuit condition, it is shown that the maximum turn-off current increases in proportion to the number of IEGT chips. As a result, a 1300 A turn-off current capability at T/sub j/=100/spl deg/C is realized using nine parallel-connected IEGT chips in an inductive load circuit and without a snubber circuit.

Aspects of the Conductivity Modulation Enhancement Effect in a 4500 V Planar Metal Oxide Semiconductor Device and Its Electrical Characteristics

A new high-power (4500 V) planar metal oxide semiconductor (MOS) device is fabricated and its properties are evaluated. It has low forward voltage drop and a large reverse bias safe operating area (RBSOA), and allows easy MOS control. These properties are superior to those of the conventional insulated gate bipolar transistor (IGBT) and the gate turn-off thyristor (GTO). This is due to the conductivity modulation enhancement effect resulting from an extremely wide gate electrode, which increases the hole storage and the electron injection. At the same time, the junction field effect transistor (JFET) resistance effect does not affect the forward voltage drop. The rate of increase of the off-state voltage (dVD/dt) during the turn-off process affects RBSOA markedly, therefore, it is important to set the gate resistance to an appropriate value. The press pack device that includes 20 chips of this device and 10 fast recovery diode chips can turn off a current of 1200 A at 3600 V DC voltage supply without a snubber circuit.

A highly reliable press packed IGBT

A newly developed press packed reverse conducting IGBT (RCIGBT), the ST1000EX21, having ratings of 2500 V and 1000 A, has successfully been introduced in high-reliability application areas. A multiple-chip press packed RCIGBT structure, containing IGBT chips and fast recovery diode (FRD) chips, has been achieved by using basic experimental results and a stress analysis using the finite element structure analysis program ABAQUS. Excellent electrical characteristics, especially a robust turn-off capability, such as Ic = 5000 A, Vcp = 2800 V at Tj = 125 °C, have been obtained. High reliability, withstanding a thermal cycling (fatigue) test of more than 50,000 cycles and a high-temperature voltage blocking test for 2000 hours, has been confirmed. The device is now available and is being successfully used for transportation systems and other applications that require high reliability and long-term stability. Voltage and current ratings in IGBTs and IEGTs (Injection Enhanced Gate Transistors) will be raised in the future.

Fusion of Paramecia by Means of Altered Electrofusion

We succeeded in fusion of paramecia by means of altered electrofusion. Some of the fused cells exhibited life activity and were able to perform several cell divisions. A daughter cell produced by the cell division was a singlet or a doublet and was able to proliferate its clones by repeating mitosis similar to the normal cell. On the other hand, a host fused cell showed distinct discrepancy in its form with elapsed time, according to the subtle difference of the contact between the original cells at the electrofusion.