Ken Matsushita

Low gate charge 30 V n-channel LDMOS for DC-DC converters

We have developed low on-resistance and low feedback gate charge 30 V n-channel LDMOS for MHz switching DC-DC converter applications. The feature of the device is that it has achieved a high avalanche capability of more than 20 amperes together with Ron/spl dot/Qqd value of 10 m/spl Omega/nC, which is the lowest, ever reported for 30 V devices. A low gate resistance of 0.4 /spl Omega/ was achieved by two layer metal electrodes. These features are desirable for MHz switching frequency DC-DC converters to obtain higher efficiency. Good avalanche capability of 20 amperes is achieved under unclamped inductive switching (UIS) condition.

4500 V IEGTs having switching characteristics superior to GTO

In this paper, the authors report, for the first time, an exact prediction of the turn-off characteristics of 4500 V IEGTs and compare the results with those for GTOs. The prediction was made by means of device simulation and trial fabrication of IEGTs. The turn-off power loss of the 4500 V IEGT with a 17 /spl mu/m deep trench gate is predicted to be less than that of the 4500 V GTO-thyristor. It was found that the IEGTs with 4 /spl mu/m deep and wide trench gate can attain a small on-state voltage drop, which is the same level as that of the IEGT with 17 /spl mu/m deep and narrow trench gate. The on-state voltage drop of the fabricated IEGT with the 4 /spl mu/m deep trench gate is 4.5 V at 50 A/cm/sup 2/. Although the device design of the fabricated IEGT was not optimized, the observed turn-off characteristics were in good agreement with the simulated results. It has been numerically confirmed that the 4500 V IEGT can realize a smaller turn-off loss than a 4500 V GTO-thyristor under a typical application circuit. It was, thus, confirmed that IEGTs can replace GTOs without degradation of switching frequency.

Theoretical investigations on IGBT snubberless, self-clamped drain voltage switching-off operation under a large inductive load

The authors describe the results of numerical investigations of IGBT (insulated-gate bipolar transistor) snubberless switching-off operation under a large inductive load (the so-called sustaining mode operation). A simulation of this kind has not previously been performed because it involves severe convergence problems. However, the authors have successfully analyzed this phenomenon by using a device simulator TONADDE2C which implements a rapid device/circuit solving algorithm. All of the electron current is found to be supplied by impact ionization during the sustaining mode; the drain voltage is self-clamped at the sustaining voltage by electrons, owing to impact ionization. The sustaining voltage is considered to be a function of the p-n-p transistor part of the common-base current drain and the structure parameters, and it can be controlled by the carrier lifetime through the former.<<ETX>>

High voltage (4kV) emitter short type diode (ESD)

This paper reports for the first time, the effects of emitter short structures, ESD(a), ESD(b)(see Fig.l), as well as the effect of a very shallow emitter on the reverse recovery characteristics for 4kV high voltage diodes. It was found that a diode with a shallow p-emitter and emitter short structures attains half of the reverse recovery current Irr, compared to conventional punch-through type p-i-n diode. It was also found that ESD has a further advantage, in that the leakage current is as low as conventional p-n junction diodes, even at 125 E. ESD structures with a fine n+ and p+ short structure attains no parasitic effect, even at current density 100 A/& and di/dt -1000 A/&/ps conditions.

Blocking voltage design consideration for deep trench MOS gate high power devices

This paper describes, for the first time, the possibility of realizing a deep trench gate device with high blocking voltage. For a trench gate device with 4.5 kV blocking voltage, the influence of the trench gate geometrical parameters on the breakdown voltage is analyzed using the two-dimensional breakdown voltage simulator TONADDE II B. The breakdown voltage decreases as the p-base width increases. On the other hand, the breakdown voltage increases as the trench gate width increases. The breakdown voltage is independent of the trench gate depth from the p-n junction in the region from 8 to 20 /spl mu/m. Assuming that the trench gate width is 1 /spl mu/m, the maximum p-base width to realize 4.5 kV blocking voltage is about 6 /spl mu/m. Therefore, it is concluded that a 4.5 kV blocking voltage of a deep trench gate device is attainable by the present process technology.

4.5 kV high-speed and rugged planar diode with novel carrier distribution control

This paper reports on the development of a 4.5 kV diode with superior reverse recovery characteristics and ruggedness. The carrier distribution of the diode is controlled by the new p-emitter structure and the optimized local lifetime control on anode and cathode sides. Maximum reverse recovery current 35% lower and tail time 50% smaller than those of a conventional p-i-n diode have been obtained. The diode has excellent ruggedness, being able to withstand 300 A/cm/sup 2/-3500 V recovery at 500 A//spl mu/s/cm/sup 2/ di/dt.

Tail-current-less 4.5 kV switching device realizing high frequency operation

Tail-current-less 4.5 kV switching is investigated in this work. A device design to obtain tail-current-less switching has been theoretically attained by a detailed analysis concerning stored carrier behavior in n-base during turn-off. A local lifetime control technique has been used to obtain tail-current-less switching. The switching characteristics of the device which applied local lifetime control technique have been simulated by using a simple local lifetime control model. The fabricated device has realized a tail-current-less turn-off switching with peak current of 30 A/cm/sup 2/ and supplied voltage of 2250 V.