IGBT modules robustness during turn-off commutation

The behaviour in terms of robustness during turn-off of power IGBT modules is presented. The experimental characterisation is aimed to identify the main limits during turn-off in power IGBT modules in typical hard switching applications. In this paper an experimental characterization of high power IGBT modules at output currents beyond RBSOA, at high junction temperatures and under different driving conditions is presented. Several devices of different generations, current and voltage ratings have been considered. The experimental characterisation has been performed by means of a non-destructive experimental set-up where IGBT modules are switched in presence of a protection circuit that is able to prevent device failure at the occurrence of any possible instable behaviour. The experimental analysis confirms the very good robustness of high power IGBT modules which can withstand large current overstress well beyond the declared RBSOA limits even at temperatures larger than those one declared by manufacturers. A comparison between IGBT device generation is also presented.     

Instable mechanisms during unclamped operation of high power IGBT modules

The behaviour in terms of robustness during unclamped operations of power IGBT modules is presented. The experimental characterization is aimed to identify the main instable phenomena during unclamped turn-off in power IGBT modules. Several devices of different generations, current and voltage ratings have been analyzed. Thanks to a non-destructive experimental set-up, it is possible to observe instable phenomena without causing the damage of the device under test. In this paper, it is shown that the destructive conditions during unclamped operations are preceded by precursors on the gate side which indicate instable phenomena taking place inside the device. The dependence of the destructive phenomenon on the driver conditions are widely and exhaustively analyzed.     

Transient temperature measurements and modeling of IGBT's undershort circuit

This paper discusses the estimation of possible device destruction inside power converters in order to predict failures by means of simulation. The study of insulated gate bipolar transistor (IGBT) thermal destruction under short circuits is investigated. An easy experimental method is presented to estimate the temperature decay in the device from the saturation current response at low gate-to-source voltage during the cooling phase. A comparison with other classical experimental methods is given. Three one-dimensional thermal models are also studied: the first is a thermal equivalent circuit represented by series of resistance-capacitance cells; the second treats the discretized heat-diffusion equation; and the third is an analytical model developed by building an internal approximation of the heat-diffusion problem. It is shown that the critical temperature of the device just before destruction is larger than the intrinsic temperature, which is the temperature at which the semiconductor becomes intrinsic. The estimated critical temperature is above 1050 K, so it is much higher than the intrinsic temperature (~550 K). The latter value is underestimated when multidimensional phenomena are not taken into account. The study is completed by results showing the threshold voltage and the saturation current degradation when the IGBT is submitted to a stress (repetitive short circuit)     

The high frequency behaviour of high voltage and current IGBT modules

Sharp voltage gradients act as a stimulus for high power IGBT modules, which can exhibit a potentially instable high frequency behaviour. In fact, they can act as a radio frequency amplifier and, in particular operating conditions, the interaction between the device and the control or the external circuit can cause self-sustaining oscillations or the enhancement of the unevenness in current distribution inside a power module thus having a significant impact on the reliability of the power converter. Moreover, this RF amplification worsen the generated EMI (Electro Magnetic Interference). This paper presents an extensive experimental investigation about the high frequency behaviour of IGBT high power modules. The measurements were performed by means of an original experimental set-up that was specifically conceived and constructed. The data are analysed with the help of a theoretical small signal model which is able to describe RF behaviour of high power IGBT modules.     

Theoretical and numerical comparison between DMOS and trenchtechnologies for insulated gate bipolar transistors

An accurate and comprehensive comparison between DMOS and Trench technologies for Insulated Gate Bipolar Transistors (IGBT) is presented. The study is performed using extensive two-dimensional numerical simulations and fundamental physical modeling. Various phenomena such as the influence of the channel density on the forward voltage drop and the effect of the channel mobility degradation on the on-state characteristics have been the object of controversial studies. The analysis performed here describes rigorously these phenomena and accounts for new physical effects such as the channel length modulation and PIN diode carrier dynamics. It is concluded that at relatively high voltage and high current densities (>100 A/cm²) an optimally designed Trench IGBT results in significant theoretical advantages over its conventional DMOS variant, mainly due to an increased packing density, PIN diode effect, reduced latch-up current density and elimination of the JFET effect     

A novel high performance insulated gate bipolar transistor

For the first time, a new concept of LDE-IGBT (local drift-region enhanced IGBT) is proposed and verified by two-dimensional (2D) device-circuit mixed simulations. The structure of the proposed device is almost identical to that of the conventional IGBT, except for an additional n⁺ plugged region under the gate contact. The proposed device exhibits larger maximum operating current, meaning higher current capability, which is expected for high-power operation. The simulation results indicate the LDE-IGBT can obtain a low on-state voltage drop with negligible increase of turn-off time due to lower sensitivity of turn-off time to the novel structure. Therefore, the trade-off relation between on-state voltage and turn-off time is improved and decoupled efficiently. Finally, the effects of three novel structure parameters on the on-state voltage are demonstrated in detail.     

功率MOS器件的结构与性能

电力电子器件的结构决定其性能,而器件的性能又决定电路的性能。根据此原理,本文分析比较了近十年来十种实用的具有新型的功率MOS器件的结构与性能特点,包括：NPT－IGBT、PT－IGBT、SDB－IGBT、Trench MOSFET、Trench IGBT、Cool MOSFET、BiMOSFET、HV－IGBT、HS－IGBT、RB－IGBT。     

Optimisation of the number of IGBT devices in a series-parallel string

High-power semiconductor switches can be realised by connecting existing devices in series and parallel. The number of devices in series depends on the operating voltage of an application and the individual device voltage rating. For a given application, the use of higher voltage rated IGBTs leads to a fewer number of devices and vice versa. The total power loss of the series string equals to the sum of individual IGBT power losses and total loss increases with the increase in operating frequency. The level of increase in power loss depends on the device characteristics. For high current operation, the minimum number of devices depends on the current rating of individual device. In this paper, series IGBT string of six 1.2 kV, four 1.7 kV, two 3.3 kV and a single 6.5 kV IGBTs are simulated for a 4.5 kV/100 A application and power losses are analysed for different frequencies and duty cycles. This power loss analysis is extended for commercial IGBTs to compare the simulation results. The number of devices for minimum power loss depends on operating frequencies and power savings are significant both at low and high frequencies. In addition to the power losses, the other important issues in optimising the number of IGBTs are described in this paper. When IGBT modules are connected in parallel the principle of derating is applied to obtained reliable operation. This is explained with some examples.     

Fast power cycling protocols implemented in an automated test bench dedicated to IGBT module ageing

This paper presents fast test protocols for ageing IGBT modules in power cycling conditions, and a monitoring device that tracks the on-state voltage V_CE and junction temperature T_J of IGBTs during ageing test operations. This device is implemented in an ageing test bench described in previous papers, but which has since been modified to perform fast power cycling tests.The fast test protocols described here use the thermal variations imposed on IGBT modules by a test bench operating under Pulse Width Modulation conditions. This test bench reaches the maximal values of power cycling frequencies attainable with a given module packaging in order to optimize test duration.The measurement device monitors V_CE throughout the ageing test that is needed to detect possible degradations of wire bonds and/or emitter metallization. This requires identifying small V_CE variations (a few dozen mV). In addition, the thermal swing amplitude of power cycling must be adjusted to achieve a given ageing protocol. This requires measuring junction temperature evolution on a power cycle, which is carried out by means of V_CE measurement at a low current level (100 mA).Experimental results demonstrate the flexibility of this test bench with respect to various power cycling conditions, as well as the feasibility of the proposed on-line monitoring methods.     

The injection efficiency controlled IGBT

An IGBT structure in which the anode injection efficiency changes with current density, the injection efficiency controlled IGBT (EEC-IGBT), is proposed. The anode injection efficiency of the IEC-IGBT is controlled via a current sensor inherent in its structure. Anode injection efficiency is strongly enhanced at low device current density and significantly reduced at high device current density. This enables the device to have a low on-state voltage drop (V_on) and superior safe operation area (SOA), making it very suitable for high-power applications. Simulation results based on 3.3 KV DMOS NPT devices indicate the on-state voltage drop of the IEC-IGBT is reduced by 0.6 V (20%) and the short-circuit SOA (SCSOA) is improved by several times compared to the conventional IGBT     

An IGBT DC subcircuit model with non-destructive parameters extraction and comparison with measurements

This paper proposed and optimized an IGBT subcircuit model which is fully spice compatible. Based on analytical equation describing the semiconductor device physics, the model parameters are extracted accurately via measured data without devices destruction. The IGBT n⁻ layer conductivity modulated resistor is effectively modeled as a voltage controlled resistor. The proposed model can be used to accurately predict the IGBT output I–V characteristics, and low current gain etc. The simulation results are verified by comparison with measurement results and found to be in good agreement. The average error is within 8% which is better than previously reported results of semi-mathematical models.     

Some observation dealing with the failures of IGBT transistors in high power converters

The explosion strength of high power IGBT modules is one of the important parameters that may decide on converter equipment reliability in extreme circumstances. The explosion strength of a device is represented by the peak value of the collector current (so called “peak case nonrupture current”) that cannot be exceeded. Some main IGBT failure mechanisms under service conditions are discussed. Test methods and experimental results on device case explosion strength are presented. Experiences concerning starting, tests and service of high IGBT converters are given. Preliminary load tests with rapidly changing current values are useful for newly fabricated IGBT converters.     

Power cycling test and failure analysis of molded Intelligent Power IGBT Module under different temperature swing durations

Molded IGBT modules are widely used in low power motor drive applications due to their advantage like compactness, low cost, and high reliability. Thermo-mechanical stress is generally the main cause of degradation of IGBT modules and thus much research has been performed to investigate the effect of temperature stresses on IGBT modules such as temperature swing and steady-state temperature. The temperature swing duration is also an important factor from a real application point of view, but there is a still lack of quantitative study. In this paper, the impact of temperature swing duration on the lifetime of 600 V, 30 A, 3-phase molded Intelligent Power Modules (IPM) and their failure mechanisms are investigated. The study is based on the accelerated power cycling test results of 36 samples under 6 different conditions and tests are performed under realistic electrical conditions by an advanced power cycling test setup. The results show that the temperature swing duration has a significant effect on the lifetime of IGBT modules. Longer temperature swing duration leads to the smaller number of cycles to failure. Further, it also shows that the bond-wire crack is the main failure mechanism of the tested IGBT modules.     

Zero-Current Soft-Switching Performance of 1200-V PT Clustered Insulated Gate Bipolar Transistor

Zero-current soft-switching performance of a 1200-V, 20-A punch-through (PT) clustered insulated gate bipolar transistor (CIGBT) is evaluated in this paper. Turn-on over-voltage transients have been witnessed in 2D numerical simulations and experimental results. These have been shown to be influenced by circuit parameters and internal device structure. Conductivity modulation lag within the device is found to be dependant upon dI/dt; however, this alone does not explain the significant over-voltages at turn-on. The device structure is found to influence the magnitude of such voltage peaks. By optimization of the structure, over-voltages can be minimized, resulting in a significant improvement in losses compared to an IGBT. The current bump associated with zero-current turn-off has been analyzed under various dV/dt values and is influenced by circuit capacitance, switching timings, and carrier lifetime. Internal dynamics of the CIGBT have been analyzed to give an insight into the performance under zero-current switching (ZCS). ZCS tests at 600 V, 20 A have shown that the CIGBT performs well with respect to a commercial IGBT of the same rating. Dynamic saturation voltage of the CIGBT has been shown to be 15% lower at room temperatures to that of an equivalent IGBT.     

A new vertical IGBT structure with a monolithic over-current,over-voltage, and over-temperature sensing and protecting circuit

A new 600 V vertical Insulated Gate Bipolar Transistor (IGBT) structure with monolithically integrated over-current, over-voltage, and over-temperature sensing and protecting functions has been developed to exploit an extremely excellent trade-off characteristic between an on-state voltage drop and turn-off time for the first time. This device can be easily made by the conventional IGBT fabrication process. An accurate and a real-time device temperature detection, as well as a high withstand capability against over-current and over-voltage conditions (short circuit immunity of 30 μsec, clamped collector voltage of 640 V), have been achieved. Furthermore, an excellent trade-off characteristic of 1.40 V as an on-state voltage drop and of 0.18 μsec as a fall time is also obtained     

一种新结构IGBT——内透明集电极IGBT的仿真研究

本文首次对新近提出的一种新结构的IGBT——内透明集电极IGBT进行了器件性能的仿真。这种IGBT是在传统非透明集电极IGBT结构基础上,通过在集电区内距离集电结很近处设置一个高复合层的方法,使器件在物理上实现了集电极对电子的透明,同时又避免了低压透明集电极IGBT制造过程中超薄片操作的技术难题。论文重点对器件的温度特性和关断特性进行了仿真研究,并与现行PT-IGBT和FS-IGBT进行了比较。仿真结果表明,通过合理调整内透明集电极IGBT的参数组合,可以使其具有通态压降正温度系数的同时,又具有较快的关断速度,实现透明集电极IGBT的优良性能。     

The robustness of series-connected high power IGBT modules

The behaviour in terms of robustness of series-connected high power IGBT modules is presented, arranged in a topology which ensures voltage balance on IGBT’s and diodes by means of a simple auxiliary circuit applied directly on the high power devices, which are used in hard switching mode. Analyses in terms of IGBT and diode SOA (safe operating area), collector to emitter voltage gradient and short circuit condition are reported as well as an extended experimental characterisation. Both analyses confirm superior switching rating and system reliability, by using two series-connected IGBT in substitution of a single module, same current and double voltage rated. Moreover, thanks the auxiliary circuit presence, the robustness of total system is maintained also in extreme operating conditions.     

High channel density dual operation mode MOS-controlled thyristorwith superior current saturation capability

A 1200-V dual operation mode MCT with low on state voltage drop, high turn-off current and superior current saturation capability has been developed. The dual operation mode MCT overcomes the tradeoff between the on-state voltage drop and the current saturation capability of the conventional IGBT operation by working in a thyristor mode in the on state and in an IGBT mode during the switching transient. This letter reports the device development and demonstrates how the dual operation mode MCT can be beneficial in switching circuit applications     

A 2D physically based compact model for advanced power bipolar devices

A two-dimensional (2D) physical compact model for advanced power bipolar devices such as Injection Enhanced Gate Transistor (IEGT) or Trench IGBT is presented in this paper. In order to model the complex 2D nature of these devices, the ambipolar diffusion equation has been solved simultaneously for different boundary conditions associated with different areas of the device. The IEGT compact model has been incorporated into the SABER simulator and tested in standard double-pulse switching test circuit. The compact model has been established to model a 4500 V-1500 A flat pack TOSHIBA IEGT.