Microstructural studies of sputter-deposited TiN ceramic films

Abstract

A transmission electron microscopy study was undertaken to characterize the microstructures of TiN thin films that were sputter-deposited onto Cu-Be, alumina and glass substrates. There were no substantial microstructural differences observed among the films; the average grain size was 150 nm and the grains were surrounded by growth defect voids which are characteristic of Type-T microstructures. For comparison, the microstructure of TiN that was directly deposited onto carbon-coated TEM grids was also characterized. These films also contained grain-boundary voids, although the average grain size was only 15 nm. A prominent feature of the films deposited on the three substrates was the presence of intragranular microcracks which were usually associated with grain-boundary cusps or facets. These cusps were observed to lie on {220} planes with arrays of microcracks emanating from them with a periodicity of approximately 10 nm. It was speculated that due to the extremely high residual stress in these films, these cusps act as stress raisers that promote the formation of the microcracks.