Optimisation of Schottky electrode geometry

Abstract

The geometry of the Schottky contact electrode is important in the design of Schottky power diodes. This work focuses on the optimum shape of the Schottky contact geometry and uses finite element modeling to determine the effects of the shape on electrical characteristics of a diode. The investigation considers the typical situation where the contact is smaller than the substrate area. Simulations were run with different shapes ranging from perfect square to perfect circle with the size of the diode substrate (die) and the distance between the edge of the diode and edge of the Schottky contact as a constant. The different models were examined and compared with magnitude the occurrence of the maximum current density (for a particular output current) and hence the breakdown regions at current density approaching the critical value for breakdown (most likely destruction of a diode) due to high current density. There as an optimum geometry determined for the highest current that the given diode substrate could deliver. The results clearly show that the optimum geometry for the Schottky contact should be neither perfect square nor perfect circle, but an exact geometry in between. This optimum geometry gives the optimum distribution of current density around the edge of the Schottky contact. Investigation is done using Synopsys TCAD. The forward and reverse bias situations were investigated to optimize the electrode geometry.