Chiara Corvasce

Thin-Wafer Silicon IGBT With Advanced Laser Annealing and Sintering Process

A novel insulated gate bipolar transistor (IGBT) featuring thin-wafer processing and a combined dopant activation laser annealing and contact metal laser sintering is presented. The device concept includes a new back-side boron anode (collector) activation process by laser annealing through a titanium layer to enhance the absorption of the deposited energy from the laser beam. This technology enables improved activation control of the anode injection efficiency for thin-wafer-based IGBTs rated normally below 1700 V. The IGBT concept will therefore be provided with a wider range of performance options on the loss technology curve when compared to state-of-the-art devices processed with conventional activation techniques.

Field Shielded Anode (FSA) concept enabling higher temperature operation of fast recovery diodes

In this paper, we introduce the Field Shielded Anode (FSA) concept that enables higher temperature operation of fast recovery diodes with planar junction termination. Conventional diodes utilizing local lifetime control principles show excellent dynamic properties at the expense of a higher leakage current, which is generated during reverse blocking when the space charge region penetrates into the zone containing the radiation defects. In contrast to this, the FSA concept spatially separates the space charge region from the zone with the radiation defects. The ruggedness of conventional diodes can be exceeded with the new FSA concept, while the leakage current is reduced by a factor of ∼4. This was achieved using a special junction extension introduced between the active area and the guard-ring termination. The design parameters and their influence on the softness and the safe-operating area are presented.

The next generation high voltage IGBT modules utilizing Enhanced-Trench ET-IGBTs and Field Charge Extraction FCE-Diodes

In this paper, we present the next generation of IGBT modules employing the latest Enhanced Trench ET-IGBT and Field Charge Extraction FCE fast diode devices. Such technologies enable high power IGBT modules to be capable of providing higher level of electrical performance in terms of low losses, good controllability, high robustness and soft diode reverse recovery. The first prototype dual modules with the new chip technologies rated at 300A and 3300V were fabricated and tested. The paper will present in detail the ET-IGBT and FCE diode concepts, the full static and dynamic electrical test results and their impact for achieving higher levels of performance in future power electronics applications.

Demonstration of an enhanced trench Bimode Insulated Gate Transistor ET-BIGT

In this paper, a 3300V Bimode Insulated Gate Transistor BIGT chip utilizing an Enhanced Trench MOS cell is demonstrated. The paper provides an insight into the ET-BIGT device design along with the static and dynamic electrical results obtained from the first manufactured prototypes. The combined advantages of a low loss Enhanced Trench cell concept and BIGT chip integration sets a new milestone for delivering higher output power for the next generation BIGT power modules.

Short circuit behavior of the Bi-mode Insulated Gate Transistor (BIGT)

The BIGT is a Reverse Conducting IGBT device which combines functionality of a high power IGBT and fast diode on a single chip. In this paper, an investigation of the IGBT mode short circuit performance of the BIGT is carried out. The behavior of the BIGT under IGBT mode short circuit conditions is illustrated by measurements on a 3.3kV 1500A HiPak1 module and then supported by circuit and detailed device physics simulations. The short circuit conditions of type II and type III are discussed, with the variations introduced due to the gate control of the BIGT when operated in reverse conducting mode. Comparison to standard IGBTs with Soft-Punch-Through (SPT) technology in a HiPak2 module is also provided.

The influence of humidity on the high voltage blocking reliability of power IGBT modules and means of protection

Abstract High voltage IGBT modules are used in high power applications including traction, industrial drives, grid systems and renewables such as in wind-power generation and conversion. Many of these applications are subject to harsh environmental conditions and in particular when the inverter cabinets do not shield the power electronics, including the IGBT modules, from such conditions. As an example, IGBT modules can be exposed to severe humidity levels. In this paper we investigate the influence of the combination of humidity and high voltage on the blocking reliability of 6.5 kV IGBT and diode devices. An improved testing approach High Voltage, High Humidity, High Temperature reverse biased (THBHV-DC) when compared to classical THB is applied to assess the robustness of different termination designs and passivation stacks. Full description of the failure mode and of its correlation to the humidity induced electrical field modifications is also provided. This analysis offers an insight on the design and testing aspects which are of key importance to the development of environmentally robust high power IGBTs.

Improving the Short-Circuit Reliability in IGBTs: How to Mitigate Oscillations

In this paper, the oscillation mechanism limiting the ruggedness of insulated gate bipolar transistors (IGBTs) is investigated through both circuit and device analysis. The work presented here is based on a time-domain approach for two different IGBT cell structures (i.e., trench-gate and planar), illustrating the two-dimensional effects during one oscillation cycle. It has been found that the gate capacitance varies according to the strength of the electric field near the emitter, which in turn leads to charge-storage effects associated with low carrier velocity. For the first time, it has been discovered that a parametric oscillation takes place during the short circuit in IGBTs, whose time-varying element is the Miller capacitance, which is involved in the amplification mechanism. This hypothesis has been validated through simulations and its mitigation is possible by increasing the electric field at the emitter of the IGBT with the purpose of counteracting the Kirk effect.

An advanced bimode insulated gate transistor BIGT with low diode conduction losses under a positive gate bias

Despite the previously reported benefits of High Voltage Reverse Conducting RC-IGBT concepts such as the BIGT, the main obstacle for adopting them in mainstream applications is the dependency of the diode conduction losses on the applied gate voltage polarity. In most applications, adaptations are required at both control and gate drive levels for providing lower diode conduction losses. The paper investigates this particular issue with respect to the device design. With the aid of both simulation and experimental results, an advanced low loss BIGT, which can operate efficiently under all gate bias conditions is proposed.

Extraction of dynamic avalanche during IGBT turn off

Abstract When IGBTs are switched with high dV/dt at high currents, dynamic avalanche occurs. Under certain conditions, this phenomenon is known to potentially degrade certain IGBT architectures. An investigation of the possible degradation of our planar IGBTs was started. This paper presents a method to extract the current (and consequently charge and energy) due to dynamic avalanche from measured turn off waveforms. The method is checked with TCAD simulations and applied to an accelerated stress test on two different device designs.

Next Generation IGBT and Package Technologies for High Voltage Applications

In this paper, we will present an overview of the latest results covering both Insulated Gate Bipolar Transistor (IGBT) and packaging technologies intended for demanding high-power applications. We will present the recently developed press pack module rated at 4500 V and 3000 A utilizing an advanced reverse conducting RC-IGBT for hard switching application, which together with the improved module layout yields the most powerful IGBT-based device up to date. For applications that require isolated modules, we will show our new dual IGBT module rated up to 3.3 kV and 450 A. The module layout was optimized to allow highly scalable converter designs with overall low stray inductances. This opens up new possibilities to further reduce losses due to the fact that the devices can be made thinner than today’s limits for achieving lower switching losses with soft performance. We will show the latest results from the enhanced trench IGBT-cell development and give an outlook for the power levels that can be achieved by combining the new cell with the RC-IGBT concept.