Mitsuhiko Kitagawa

A 4500 V injection enhanced insulated gate bipolar transistor (IEGT) operating in a mode similar to a thyristor

This paper proposes a new MOS-gate transistor structure (IEGT) for the first time, that realizes enhanced electron injection so that the carrier distribution takes a form similar to that of a thyristor and a low forward voltage drop is attained even for 4500 V devices. A developed simple analytical one dimensional model can predict a sufficiently accurate current voltage curve and clarifies a new design criterion for IEGT operation. A fabricated 4500 V IEGT realized a 2.5 V forward voltage drop at 100 A/cm/sup 2/. The IEGT had a current density over ten times that of conventional trench gate IGBT at 2.5 V forward voltage drop. An operation mode of IEGT has been theoretically and experimentally confirmed.<<ETX>>

6000-V gate turn-off thyristors (GTOs) with n-buffer and new anode short structure

6000-V gate-turn-off thyristors (GTOs) were developed for high-power inverters and choppers. In order to attain a high blocking voltage simultaneously with low turn-on and turn-off losses, a combination of an n-buffer layer and a cylindrical anode short structure was implemented. A 500- mu m n-base width, achieved by the n-buffer structure, can decrease turn-on loss to approximately 2/3 that of a conventional anode short structure. The proposed structure is effective in sweeping away excess carriers during turn-off transient without increasing the on-state voltage very much. An average anode current of 200 A can be continuously switched at a 900-Hz operational frequency by a 33-mm-diameter device. A simultaneous diffusion process for p-base and n-buffer layers was proposed and implemented to realize the newly developed device structure. >

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.

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.

A trench-gate injection enhanced lateral IEGT on SOI

This paper reports, for the first time, that lateral IGBTs with an injection enhanced multiple trench gate structure (LIEGT) on SOI successfully achieved both a low forward voltage drop and a high switching speed. The current density of LIEGTs with two trench gates is more than twice as large as that of conventional lateral IGBTs on a 10 /spl mu/m SOI. Closely spaced deep trench gates result in carrier storage under the trench gates and enhance lateral carrier flow. Although the switching speed of 10 /spl mu/m SOI LIEGTs is as fast as that of LIGBTs, its switching loss can be reduced. Thus, the electrical characteristics of lateral trench gate IEGTs on SOI are quite good.

DESIGN CRITERION AND OPERATION MECHANISM FOR 4.5 KV INJECTION ENHANCED GATE TRANSISTOR

This paper investigates the injection enhancement effect of a trench gate structure for a metal oxide semiconductor (MOS) controlled power transistor called an injection enhanced gate transistor (IEGT). By virtue of the enhancement in effective electron injection efficiency, 4.5 kV IEGTs attain a thyristor-like carrier profile during the on-state, and hence achieve the same low on-state voltage drop as that of thyristors. The operation mode of the IEGT was studied using a two-dimensional numerical simulation, and verified by device fabrication. It was confirmed that the proposed novel trench gate geometry acts as an injection enhancer by restricting the hole diffusion current which flows from the n-type high-resistance base layer to the cathode electrode. It is shown for the first time that the effective electron injection efficiency of the n-ch insulated gate bipolar transistor increases to nearly 1. It is also shown that the new trench gate structure effectively decreases the forward voltage drop without degradation of turn-off capability.

Injection Efficiency Enhancement in Dynamic Trench Gate Emitter (DTGE) for 4500 V MOS Gate Transistor (IEGT)

The injection enhancement effect of trench gate structure is investigated. The blocking voltage range in which a novel trenched gate emitter structure effectively reduces forward voltage drop is shown for the first time, by developing an analytical 1-dimensional model. It is shown that the emitter structure is not only more effective for high voltage devices such as the 4500 V devices, but also the emitter structure effectively decreases the forward voltage drop of several hundred blocking voltage devices, especially above 500 V, without degradation of turn-off capability. B-1-1

Study of 4.5 kV MOS-power device with injection-enhanced trench gate structure

We propose two new MOS-power device structures, which realize lower on-state voltage than previously proposed injection-enhanced gate transistors (IEGTs). One is an improved IEGT (or IEGN), and the other is a MOS-controlled diode (or IEGD). Using 2-D numerical simulations, it has been confirmed that the IEGN and the IEGD realize a lower on-state voltage drop than the conventional IEGT, retaining MOS gate drivability. This means that the injection-enhanced gate structure improves the effective electron injection efficiency not only for transistor structures, but also for devices with a low-injection efficiency emitter. It has also been confirmed that the 4.5 kV IEGN and IEGD can operate under the same circuit conditions as a 4.5 kV GTO-thyristor.

High-Voltage Emitter Short Diode (ESD)

We report the effects of emitter short structures, ESD(a) and ESD(b), as well as the effect of a very shallow emitter, on the reverse recovery characteristics for 4 kV high-voltage diodes. It was found that a diode with a shallow p-emitter and emitter short structures attains half the reverse recovery current I rr, compared to conventional punch-through p-i-n diodes. ESD has a further advantage in that the leakage current is as low as that of conventional p-n junction diodes, even at 125° C. ESD structures with a fine n+ and p+ short structure attain no parasitic effect, even at a current density of 100 A/cm2 and di/ dt of -1000 A/µs.

Ultra low Cout/spl times/Ron photo-relay using depleted drift layer in thin film SOI

In this paper, we propose a new concept of a MOSFET switch for small-outline photo-relays. By applying the concept of depleted drift layer to the thin film SOI MOSFET, the developed photo-relay switch has achieved the lowest Cout/spl times/Ron (product of output capacitance and on-state resistance) of 1.87 pF/spl Omega/ for 26.5V device and 4 pF/spl Omega/ for 43V device, respectively. These values are the lowest ever reported. The packaged photo-relays achieved low off-state leakage current and low output pin capacitance, being sufficient to be used 2-3 MHz frequency range measuring instrument.