Quantitative electron spectroscopic imaging studies of microelectronic metallization layers

The combination of focused ion beam (FIB) sample preparation and quantitati ve electron spectroscopic imaging is an ideal toot for the investigation of layered structures used in microelectronic metallization schemes. In the p resent work, Si3N4/Cu/Si3N4/SiO2/Si and Al/TiN/Ti/SiO2/Si metallization lay ers produced by physical vapour deposition are investigated. We apply serie s of energy filtered images in the low loss region for a mapping of the sam ple thickness which makes it possible to refine the parameters of the FIB p rocess. We also show how series of energy filtered images in the core loss region can be used to obtain elemental distribution images and chemical bon ding information on these samples on a nanometre scale. For materials with a small grain size and/or a strong variation in Bragg orientation, the inte nsity distribution of the elemental map is strongly influenced by the super imposed Bragg contrast. This detrimental effect can be reduced greatly by u sing hollow cone illumination, as is demonstrated for polycrystalline Cu, O ne striking feature observed in Cu layers prepared with FIB is strong, regu larly arranged contrast variations caused by subsurface defects in the Cu g rains, We suppose that these defects are a consequence of a strong interact ion of Ga atoms from the FIB with Cu.