Interfaces and Thin Films for Microelectronics: Composition and Chemistry as a Function of Depth

Chemical and physical analyses of materials interfaces are important technological fields, but difficult scientific challenges. The analysis is difficult scientifically because an interface may consist of as little as 2 monolayers, corresponding to 3 x 10 sup 15 atoms/cm sup 2, or a mere 5 x 10 sup -9 moles/cm sup 2. In addition to the practical difficulty of detecting such a small amount of material, one would like to be able to understand the bonding, ordering and intermixing of the atoms (if any), as well as the evolution of the interface. All of these issues are important, because it is at the interfaces between materials where issues like adhesion, delamination, electron or hole injection, and interface traps become important. In this review, we describe how surface analytical techniques, in particular x-ray photoelectron spectroscopy, can be extended to analyze interfaces. The focus of the discussion in this review will be on issues related to microelectronics, although the techniques described herein certainly can be applied to other technological classes of problems.