Manfred Pfaffenlehner

The CIBH Diode - Great Improvement for Ruggedness and Softness of High Voltage Diodes

The concept of controlled injection of backside holes (CIBH) is a novel and path breaking method for the optimization of the electrical characteristics of diodes. Buried p-doped layers at the cathode side of the diode inject holes in the base region during reverse recovery. Due to this injection the snap-off of the diode can be suppressed effectively. The main intention of this paper is to take advantage of the CIBH concept for designing a fast switching 3.3 kV diode with low Vf, low switching losses, high ruggedness and strongly improved softness. A new promising effect of the CIBH design, which we call DSDM (dynamic self damping mode), further increases the soft reverse recovery behavior and results in a nearly snap-off free diode characteristic.

1700 V-IGBT3: field stop technology with optimized trench structure

The IGBT3 technology, which combines a specific trench cell and the field stop concept, was first introduced for devices with 1200 V blocking voltage. It is now transferred to higher blocking voltage ratings. A new series of 1700 V devices is introduced, which compared with conventional NPT (= non punch through) devices has greatly reduced static and dynamic losses and preserves the well known ruggedness of NPT devices. With this new 1700 V chip generation a new product line of modules with up to 50% higher current capability in the same housing is available.

trend setting for the high power applications in industry and traction

The surge current ruggedness of free-wheeling diodes can be improved by implementing the SPEED concept (Self-adjusting P Emitter Efficiency Diode). Experiments show that the switching ruggedness of such a diode is worse than that of a conventional diode. Simulations indicate that during diode turn-off filaments are pinned at the cathode side. These filaments can be avoided by implementing CIBH (Controlled Injection of Backside Holes). It turns out that a necessary additional measure is to fully embed the p+-areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths and current crowding at the anode side. Combining these measures, the appearance of current filaments with an extremely high current density and their pinning to a certain area in the device during the turn-off period can be avoided.

Optimization of diodes using the SPEED concept and CIBH

Hydrogen-related donors can be formed by using only a moderate thermal budget, so that this process can be used to create field-stop layers in thin power devices. The electrical characteristics of 1200 V IGBTs and diodes provided with such field-stop layers are presented and compared with the characteristics of conventionally processed devices. Moreover, tailoring the field-stop distribution by multi-energy proton implantations offers new opportunities for optimizing the performance of power devices.

Tailoring of field-stop layers in power devices by hydrogen-related donor formation

Electrical characterization results (e.g. softness, cosmic ray hardness, surge current) of a novel freewheeling diode with reduced thickness and copper metallization are shown.

Novel emitter controlled diode with copper metallization in ultrathin wafer technology: Setting a performance benchmark

The surge-current ruggedness of free-wheeling diodes can be improved by implementing the self-adjusting p emitter efficiency diode concept (SPEED). Simulations indicate that the switching ruggedness is reduced because of the occurrence of cathode-side filaments during reverse-recovery. Experiments confirm the weak switching performance of such a diode in comparison to a conventional diode. By implementing the controlled injection of backside holes concept cathode-side filaments can be suppressed. However, this measure is not sufficient to regain the switching ruggedness of a conventional diode. It is also necessary to fully embed the p + -areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths at the p + p-junction and pinning of anode-side filaments. However, anode-side adjustments for improving the switching ruggedness can reduce the benefit of the SPEED concept regarding the surge-current capability.