| An important subject of modern technology, where grain boundary diffusion studies are concerned, is microelectronic and optoelectronic devices. Such devices are often supplemented by multilayer thin-film structures. The long-term stability and performance of these devices can depend fundamentally on the physical integrity of the discrete thin-film structures of the device. Thin-films are often regarded as highly susceptible structures, due to their special characteristics, such as large surface-to-volume ratio, high density of structural imperfections, and the often large composition of stress gradients. Due to the inherently large grain boundary density in polycrystalline thin-films, grain boundary diffusion is the most dominant transport mechanism in thin-film structures at the relatively low temperatures of device operation. Such material conditions can lead to electrical contact failure due to grain boundary diffusion of impurities from the adjacent layers which may cause an increase of the contact resistance, loss of ohmic characteristic, loss of adhesion, and breaking or shorting of electrical contact.; Failure of electrical or optical characteristics of these devices may also occur due to intermixing (mainly by grain boundary diffusion) and compound formation between different layers. Therefore, an understanding and controlling of the grain boundary diffusion processes in thin-films is extremely important to ensure the integrity and improve the reliability of thin-film devices.; The main purpose of this dissertation is to investigate the thermal stability and interdiffusion between thin-film couples of silver and chromium on silicon. Of principle interest is how diffusion proceeds in a bimetal diffusion couple and what phases form as the diffusion proceeds. To understand such effects, nearly 15 samples were subjected to various annealing temperatures ranging from 300–900°C and annealing times of between 15–600 minutes. Full sets of analytical images and data were completed for each annealing case. Diffusion evolution and material substructures are revealed and discussed herein. The factors affecting adhesion are reviewed, and it is shown that the structure of the interfacial region is probably a controlling factor in film adhesion. Electrical characteristics are also presented to correlate material activity with device performance. |
