Model calculations on a bipolar transistor emitter interconnection with different contact shapes

An emitter interconnection including the tungsten-filled contacts of a bipolar transistor was investigated for Al/Si/Cu and copper as metallization material. The dependence of local heating and maximum mass flux divergence on the length of the contacts and the distance between the contacts as well as the length of the metallization between the interconnect and the first contact was determined by finite element simulations. Out of the simulations the optimized geometry was determined. It is shown that copper compared to aluminum as metallization material can lead to a higher reliability of power elements. The optimization of the metallization and contact geometry can avoid high mass flux divergences and leads to a higher reliability.