Ageing tests on microwave integrated circuits

The study of failure mechanisms in microwave integrated circuits (m.i.c.s) provides essential information on the ageing behaviour of substrate-layer combinations. The ageing behaviour depends on the structure and the chemical composition of the substrate-layer combinations as well as on the ambient conditions. Tests on microwave properties, d.c. resistivity, adhesion as well as structure analysis are carried out before and after heat treatment. The structure analysis provides information about the initial nature of the samples and the ageing-induced structure changes. The ageing curves of tested m.i.c. metallizations are classified according to basic types of characteristics. These can be used as fingerprints characterizing the technology. It is shown that even small mechanical damage to the metal surface may cause nucleation of large defects resulting in a degradation of the structure, which shortens the life of the m.i.c.