Punch-through IGBTs Research Articles

Accelerated Degradation of IGBTs Due to High Gate Voltage at Various Temperature Environments

In this study, degradation phenomena due to gate bias stress at elevated temperature for the reliability test of punch-through IGBTs, which are widely used in DC circuit systems for automotive applications, were investigated. For the reliability tests of various temperatures, 4000 times temperature cycle stress was applied in IGBTs between −40°C and 200°C to accelerate the degradation process using the wide range temperature. And the delamination of the passivation layer and the metal layer in IGBTs was observed using the scan acoustic microscopy. In addition, the positive bias stress with 48 V at elevated temperature of 150°C for 60 min was applied to the gate, the threshold voltage increased up to 6.07 V due to charge trapping at gate oxide. We also compared the recovery of the devices, but the IGBTs that stressed with high DC field and elevated temperature slowed down the recovery process after 24 hours without reverse voltage. This work was focused to find the device recovery considering real conditions. Therefore, the various temperature stress and high electric field stress are important in the reliability test for IGBTs, it was reported the IGBT degradation process and failure symptoms using the accelerated and various reliability tests.

Numerical study of destruction phenomena for punch-through IGBTs under unclamped inductive switching

In this paper, a numerical description of the ruggedness of punch-through (PT) IGBTs under the unclamped inductive switching (UIS) has been proposed using two-dimensional (2D) simulations with the calibration to experimental results. The UIS capability is an important design factor of device structures for the purpose of screening defects produced during the wafer process. The local hot spot due to the current filament three-dimensionally (3D) distributed over the chip area requires 3D simulations to reproduce the current density of the filament and its behavior leading to the device destruction; however, it is difficult to simulate such a large area with an appropriate mesh size and a boundary condition. To provide a possible solution of this technical issue, 2D simulations using large scale multi-cell structures with the increased current density has been proposed to reproduce experimental results without resorting to 3D simulations. With this approach, not only destructive phenomena including the UIS ruggedness and the latch-up failure mode have been reproduced, but also the device internal state leading to the destruction has been revealed. The spatial distribution of the electric potential and the lateral electric field during the UIS condition is shown to be a key role determining the current filament width and the UIS ruggedness. Besides, the high frequency oscillation of the collector voltage during the UIS observed by experiments has been analyzed and has found to be related with the hopping motion of the current filament from a cell to its neighboring cell of the device.

New generation of 3.3kV IGBTs with monolitically integrated voltage and current sensors

Although IGBT modules are widely used as power semiconductor switch in many high power applications, there are still reliability problems related to the current unbalance between paralleled IGBTs that may destroy the whole module and, eventually, the power system. Indeed, short-circuit and overvoltage events can also destroy some of the IGBTs of the power module. In this sense, the instantaneous monitoring of the anode current and voltage values and the use of a more intelligent gate driver able to work with the signals of each particular IGBT of the module would enhance its operating lifetime. In this sense, the paper describes the design, optimization, fabrication and basic performances of 3.3kV-50A punch-through IGBTs for traction and tap changer applications where anode current and voltage sensors are monolithically integrated within the IGBT core.

Simulation of High-Voltage Injection-Enhanced 4H-SiC N-Channel IGBTs with Forward Drop Approaching that of a PiN Junction Rectifier

For SiC devices capable of blocking very high voltages (>4kV), it becomes imperative to use bipolar devices because of unacceptably large on-state losses of unipolar devices. The IGBT offers the potential for high current density operation and ease of turn off using a MOS gate structure. In this work, 15kV 4H-SiC n-channel UMOS PT (Punch Through) IGBTs with injection enhancement effect near the top emitter and transparent pemitter structure at the collector have been demonstrated to have a forward drop approaching that of a PiN junction rectifier. With proper design, a PiN-like carrier distribution in the drift region can be achieved, which allows a better trade-off between collector-emitter saturation voltage (VCE(sat)) and turn-off loss (Eoff) than conventional SiC UMOS IGBTs.

Investigation of IGBT turn-on failure under high applied voltage operation

In this paper, a new failure mode of punch-through type insulated gate bipolar transistors (PT-IGBTs) at short circuit condition under high voltage operation has been presented. After turning on the IGBTs, this failure mode is characterized as an abrupt destruction mode that takes place several microseconds later under higher collector voltage short circuit conditions. The destruction mechanism of the IGBTs has been investigated using a 2-D and a 3-D device simulation. It is found that the hole-current caused by dynamic avalanche generation at the peripheral region of the device leads to concentrate on a certain point such as the emitter contact edge of the active cells. Subsequently the IGBTs plunge into destruction. This hole-current aggregation depends on geometrical structure of the active cells close to the device peripherals where a parasitic PMOS is formed. The generated hole-current path is varied by the gate voltage and this effect results in degradation of the short circuit capabilities depending on the gate voltages. This model has been evaluated experimentally by making punch-through type IGBTs with a rating current of 200A and the IGBTs have shown enough short circuit capabilities. These devices have successfully been adopted as power devices of invertors for a new hybrid vehicle.

Investigation of the power dissipation during IGBT turn-off using a new physics-based IGBT compact model

New compact models of the IGBTs (both non-punch through IGBT (NPTIGBT) and punch-through IGBT (PTIGBT)) are presented in this paper. The models are implemented in the SABER circuit simulator and used for a study of IGBT anode current and voltage characteristics during a device turn-off (clamped inductive load circuit with gate controlled turn-off), since these parts of the transient characteristics essentially predict the power dissipation ( V× I) inside the device. It is shown that PTIGBTs are faster than NPTIGBTs, this becoming more apparent at higher clamp voltages.

Electrothermal simulations in punchthrough and nonpunchthrough IGBT's

The performance of 1200 V punchthrough (PT) and nonpunchthrough (NPT) insulated gate bipolar transistors (IGBT's) is studied in detail under unclamped inductive switching (UIS) and short circuit (SC) conditions. The need for a good physics based simulator to carry out a reliability study is pointed out in the paper. Using such a finite element-based device and circuit simulator it is shown that NPT-IGBT's show a much better performance than PT-IGBTs under UIS condition. It is also shown that an NPT device has a better short circuit withstanding capability than a PT device due to the structural differences between the two devices. As there is a huge power loss within the device during these operating conditions, device self-heating is expected to have a significant impact on device characteristics. Electrothermal simulations are used to study device self-heating and it is shown that it significantly influences device performance under SC operation whereas self-heating influences the UIS performance of only the PT device with little effect on the NPT device. The study is validated by an experimental study of short circuit failure of PT IGBTs.

Investigation of the short-circuit performance of an IGBT

This paper reports the internal dynamics of insulated gate bipolar transistors (IGBT's) under short-circuit switching conditions. Short-circuit performance of IGBT's has been studied in detail with the aid of extensive measurements and numerical simulations. An advanced two-dimensional (2-D) mixed device and circuit simulator that incorporates the self-heating mechanism has been employed to examine IGBT behavior under short-circuit stress. Latch-up free punchthrough IGBT has been examined. It is shown that hot-spot generation due to current crowding and impact ionization is the cause of breakdown of an IGBT under short-circuit switching.

Power losses in PWM-VSI inverter using NPT or PT IGBT devices

This paper investigates the power losses for two different IGBT technologies (nonpunch through and punch through) for use in PWM-VSI inverters in order to choose the right device technology for a given application. A loss model of the inverter is developed based on experimental determination of the power losses. The loss model is used on two different modulation strategies which are a sine wave with a third harmonic added and a 60/spl deg/-PWM modulation where only two inverter legs are active at the same time. The two IGBT technologies are characterized on an advanced measurement system which is described. The total power losses in the inverter are estimated by simulation at different conditions and it is concluded that the nonpunch through (NPT) technology is most useful for higher switching frequencies, while the punch through (PT) technology is especially useful at lower switching frequencies and high load currents. It is also concluded that the 60/spl deg/-PWM modulation has the lowest power losses and the power losses are almost independent of phase angle cos(/spl phi/) for normal motor operation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A 2000 V non-punchthrough IGBT with high ruggedness

The inherently great ruggedness of a 2000 V non-punchthrough IGBT is demonstrated by operating the device under short-circuit conditions up to 1800 V and nearly 600 A cm −2. Even switching an inductive load without using a freewheeling diode at a current density of 350 A cm −2 is not destructive for the device. An explanation for the principally greater ruggedness of the non-punchthrough device (in comparison with the punchthrough IGBT) is given by a 1-D computer simulation, which leads to a fundamental understanding of the physics of the device.