Edge effects in glass-passivated collector-base junctions of high-voltage transistors

A study of edge effects in glass-passivated collector-base junctions of multiepitaxial transistors is carried out by means of a two-dimensional finite element simulation of the electric field in reverse-biased junctions. The influence, on the field distribution, due to the geometrical parameters and the presence of both charges within dielectrics and equipotential rings over the external surfaces is carefully examined. An HV structure suitable for stable and reliable operation is established. The finite-element model is shown to be a powerful tool in the development of correct design criteria for very complex structures, aiming towards the achievement of a good compromise between performance and silicon consumption.