Novel buffer engineering: A concept for fast switching and low loss operation of planar IGBT
Introduction
The insulated gate bipolar transistor (IGBT) is a promising device for power electronics applications [1], [2], [3], [4], [5] and, therefore, the demand on reducing power loss and increasing operation frequency is rapidly increased. Power loss and operating frequency of the IGBT are decided by the tail-current which occurs when the device is turned off. The major cause of the tail-current is the accumulation of minority carriers in the n− drift region in the device. Minority carriers are injected from the collector during on-state and reduce the resistance of the drift region due to the conductivity modulation effect. The tail-current of the IGBT can be suppressed by reducing the minority carrier lifetime in the n− drift region of IGBT, which is achieved by electron or neutron irradiation [6], [7]. But this is expensive and damageable.
In this paper, we proposed a new buffer structure for the PT-IGBT which employs a three-step, gradually changing doping n+ structure. Although, the application of such structure to a power diode for fast switch has been reported [8], [9], [10], this is a new proposal of the application of three-step, gradually changing doping structure to the IGBT. Results of two dimensional device simulations demonstrate the proposed IGBT has a better trade-off between on-state voltage and turn-off time, a larger forward blocking voltage and a faster switching speed than the conventional device.
Section snippets
Device structure and operation
Fig. 1(a) and (b) shows the schematic cross-sectional views of the conventional and proposed device structure, respectively. The structure of the proposed device is almost the same as that of the conventional IGBT, except for the buffer layer employing a three-step, gradually changing doping n+ structure. Buffer region (N1-N2-N3) is still 10 μm and W1, W2, W3 is 3, 3 and 4 μm, respectively. The three-step doping concentration increases in the buffer region from the n− drift region boundary to the
Device performance
Numerical simulations were performed using the 2D device simulator MEDICI. This simulator performs calculations of the 2D plane structure per unit width (1 μm) in the perpendicular direction. Effective width of the device is an independent parameter. The vertical axis is the collector current flowing through the device area of 30 μm(width)×1 μm(depth). In the actual device, the unit cell shown in Fig. 1 is arrayed. Therefore, when we assume the devices turn on if the collector current density
Discussions and conclusions
Now concerning the disadvantages of IGBT, the major penalty paid by this hybridization of MOS and bipolar properties, is the slower switching of the IGBT compared to that of the power MOSFET. Nevertheless, an interesting feature of IGBT is that its turn-off time can be decreased by using a three-step, gradually changing doping n+ buffer layer at the expenditure of an increase in forward voltage drop. This unique capability endows the IGBT with the valuable opportunity of trading off between
Acknowledgements
The current work is supported by a grant from the National High Technology Research and Development Program of China (863 Program) (2003AA834025) and funded by the national natural science foundation of China (10474076).
References (10)
- et al.
Si/SiGe heterojunction collector for low loss operation of trench IGBT
Applied Surface Science
(2004) - et al.
An insulated gate bipolar transistor employing the plugged n+ anode
Microelectronics Reliability
(1999) - et al.
Electrothermal simulations in PT and NPT IGBTs
IEEE Transactions on Electron Devices
(1998) - et al.
Imputity profile effects of buffer layer on PT-IGBT characteristics
IEEE Transactions on Electron Devices
(2003) - et al.
Zero voltage switching behavior of punchthrough and nonpunchthrough insulated gate bipolar transistors
IEEE Transactions on Electron Devices
(1998)
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2006, Solid-State ElectronicsCitation Excerpt :Nowadays, it is finding widespread applications in uninterruptible power supplies, industrial motor drives and domestic and automotive electronics, preferably at medium and higher voltages (0.6–6.5 kV) and in the low and medium frequency (0.1–100 kHz) [1–4]. There has been a significant compromise to optimize the conduction and switching losses of the IGBT, however recently, many approaches for improving the turn-off speed of the IGBT have been reported [5–8], but they cause the on-state voltage drop to increase considerably due to reduced conductivity modulation effect. In order to satisfy both low on-state voltage drop and high switching speed, the trade-off relation between the switching speed and on-state voltage drop should be decoupled.
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