Towards Two Dimensional Micro-Raman Analysis of Semiconductor Materials and Devices
Raman scattering spectroscopy has already proved to be a valuable technique for the nondestructive analysis of strain, composition, periods and layer thicknesses in semiconductor superlattices and epitaxial layers. There is now the need to extend the technique to electronic and optoelectronic device structures, and indeed to be able to make such measurements on individual devices. This latter requirement demands the capability of analysing with a spatial resolution of the order of one micrometer. Micro-Raman scattering techniques have recently become available, and these are capable of yielding the necessary spatial resolution.
For device related applications the requirement is often not simply for point analyses, but for areal distributions of material properties. In particular, measurements on cross sections through device structures may be required. At the British Telecom Research Laboratories we have been working towards the development of a Micro-Raman scattering system that will be capable of producing such two dimensional information on a microscopic scale.
The progress achieved to date will be reported, and some preliminary results reporting the use of the system to map out the strain around dislocations in a semiconductor will be presented. Also included will be an account of some of the problems encountered, and an assessment made of their likely effect on the realisation of the goal.