The Corrugated P-Base IGCT - a New Benchmark for Large Area SQA Scaling

Abstract

A 91 mm diameter IGCT with extraordinary Safe Operating Area (SOA) is presented in this paper. The power density at turn-off reached values as high as 700 W/cm2, which is twice the previously reported SOA limit for devices with a comparable diameter. The improvement was achieved by masking one of the p-base diffusions, giving the p-base a corrugated appearance as well as improving the gate circuit. I.' INTRODUCTIONTHE Integrated Gate Commutated Thyristor (IGCT) was first presented in the 1990s. Employing "hard drive" as a means of turning off exclusively in pnp-mode, like the IGBT, it quickly became a more attractive choice than the GTO thanks to the possibility for snubberless operation and expanded SOA. In the on state, a properly designed thyristor is equivalent to a p-i-n rectifier with infinite possibilities for optimization of the excess carrier distribution, rendering lower switching losses than for example the IGBT. The low losses together with the possibility to fit a single IGCT with a current capability of thousands of Amperes makes it one of the top choices in the very high power range, for example in highpower inverters for industry and other applications. The shortcomings of IGCT technology are the possibility for controlled turn-on and intrinsic short-circuit current limitation; these are features available in well-designed IGBTs while still missing in IGCTs. These limitations inevitably add a certain overhead to IGCT-based circuits more specifically in the form of azdl/dt choke and a clamp for excessive voltages due to the choke. This overhead accentuates the benefits of the IGCT toward the higher end of the power range compared to the IGBT. As a result, there is a perpetual pull for more potent IGCTs that is usually met by increasing the device thickness and area with the expected impact on device losses. In this paper we show a new Corrugated p-Base IGCT technology (CB-IGCT) that facilitates a power density improvement without increasing the losses.T. Wikstrom, T. Stiasny, M. Rahimo and P. Streit are with

4.5 kV Bi-mode Gate Commutated Thyristor design with High Power Technology and shallow diode-anode

“…Studies on GCTs have shown that this is due to parasitic gate inductances within the wafer being non-uniformly distributed [7], [9], [10]. Therefore, in order to reproduce the behaviour of the BGCT in dynamic conditions and in particular to assess full wafer devices in terms of the MCC, the interaction between adjoining regions in the wafer as a result to this imbalance in the gate impedance has to be taken into account.…”

“…In this work three BGCT variants are considered and analysed. The device schematics are shown in High Performance Technology has been proved effective in lifting the Maximum Controllable Current (MCC) in IGCTs [7], [8], [14], it is therefore desirable to examine the possibility of including it in the BGCT.…”

“…Nevertheless, its impact on current controllability when operating in GCT mode has not been examined. In this work we assess the impact of shallow diodeanodes in the operation of the GCT and propose the introduction of optimised High Power Technology [7], [8] (HPT+) in the GCT part. With the aid of a complex simulation model which was previously calibrated, we performed failure analysis to demonstrate that the proposed BGCT with shallow anode in the diode part and High Power Technology in the GCT part receives a step improvement in Maximum Controllable Current (MCC), a necessary requirement in devices aimed for high power applications.…”

A Robust Reverse Blocking Switching Device for High Power Direct AC/AC and Current Source Converters

“…It was experimentally verified that this different field distribution had no negative impact on cosmic ray withstand capability. This new structure was also successfully implemented in asymmetric GCT structure [3].…”

Future trends in high power devices

“…In the meantime, the scalability of IGCT has increased up to 10 kV and several kA. The maximal turnoff current of 4.5 kV IGCT has increased towards 7 kA [4] and blocking voltages at 10 kV were achieved [5]. This means that the IGCT as a single part will remain the switch with the highest power rating also in the future.…”