Structure and Robustness Optimization of Fast High Power Diodes
von Zheng ZhiCurrently, freewheeling diodes are essential power devices used in converter applications. The most commonly used converters, „Voltage Source Converters“ utilize either IGBTs or IEGTs as the active-switches. Both of these need to be matched with high-performance freewheeling diodes. With a new generation of high-performance freewheeling diodes, not only can the reverse recovery losses be minimized, but also robustness can be increased. Therefore, there is an increasing demand for high power high voltage diodes. The requirements are for low losses and rugged performance during even under the fastest switching conditions. This work describes a detailed investigation to optimize the reverse recovery behaviour of 4.5 kV Press-Pack diodes under different current commutation slopes up to 15 kA/? s. Controlled axial lifetime and appropriate field stop (FS) profiles were investigated in order to obtain soft recovery behaviour at 10% to 200% of rated current. Phosphorus diffusion and proton implantation were employed in order to discover an appropriate process for manufacturing the field stop structure. Besides, the contributions of varied lifetime adjustments at the anode side of the diode have been analyzed and explained using measurements and simulations. Another diode cathode structure with a deeply diffused cathode, which intends for further reduced base width and improved robustness against cosmic rays is introduced.
Power devices often require decades of trouble-free operation. When cosmic radiation was identified in the early 1990s as the cause of spontaneous silicon power device failures, the potential failure mechanisms were investigated in numerous experimental and numerical studies. This work aims to investigate iii the failure mechanisms in simulation, to use high voltage (> 4.5 kV) devices where no detailed studies are available, to compare the influence of different cathode structures and to provide the possibility of optimization.
A deep doped cathode in the diode was suggested as a structure optimization for achieving high ruggedness against cosmic ray failures. Three different deep cathode structures of a high-power diode were investigated: deep diffused cathode, cathode with strong and weak n-buffer, respectively. The influence of those cathode structures on dynamic electrical behaviours during cosmic ray events was investigated.
Power devices often require decades of trouble-free operation. When cosmic radiation was identified in the early 1990s as the cause of spontaneous silicon power device failures, the potential failure mechanisms were investigated in numerous experimental and numerical studies. This work aims to investigate iii the failure mechanisms in simulation, to use high voltage (> 4.5 kV) devices where no detailed studies are available, to compare the influence of different cathode structures and to provide the possibility of optimization.
A deep doped cathode in the diode was suggested as a structure optimization for achieving high ruggedness against cosmic ray failures. Three different deep cathode structures of a high-power diode were investigated: deep diffused cathode, cathode with strong and weak n-buffer, respectively. The influence of those cathode structures on dynamic electrical behaviours during cosmic ray events was investigated.