Emerging process technologies for fabricating sub-micron and nanoscale semiconductor devices and novel multilayer materials all require extremely precise control of growth at surfaces. In situ, non-destructive, real-time monitoring and characterisation of surfaces under growth conditions are needed for further progress in this area, with atomic scale resolution. The main aim of this project is to demonstrate the use of new epioptic techniques for in situ growth monitoring and non-destructive characterisation, for MOVPE, MBE and MOMBE growth in dedicated III-V reactors.
New techniques for determining the properties of materials used in information technology devices are being developed. Light is used as both probe and signal (epioptics), with extremely high spatial resolution. In contrast to existing techniques, epioptics can be used in situ, while growing crystalline material, in all environments.
So far 3 major results have been obtained. Growth of III-V epitaxial layers in an atmospheric pressure metal organic vapour phase epitaxy (MOVPE) reactor has been monitored in real time, with submonolayer resolution, using reflection anisotropy spectroscopy (RAS). The number of single atomic layers grown is simply determined by counting the number of oscillations in the RAS signal.
Growth of II-VI epitaxial layers has been monitored, in situ and in real time, using Raman spectroscopy, with submonolayer resolution and evidence of chemical reactivity at the II-VI, III-V interface has been obtained.
A combination of linear optical theory and experiment has resolved a long standing controversy on the nature of the dimer structure on the surface of silicon(001).
APPROACH AND METHODS
EPIOPTIC (3177) showed that new optical techniques have great potential in the area of emerging process technologies: monolayer sensitivity, in situ monitoring of semiconductor growth and complimentary information from different epioptic techniques have been demonstrated on model systems.
In EASI new epioptic techniques for in situ growth monitoring and non-destructive characterisation for MOVPE, MBE and MOMBE III-V growth reactors. In addition, a preliminary assessment of epioptic probes for ultra-clean silicon processing diagnostics will be made. An improved understanding of the origins of the epioptic response from surfaces and interfaces will be sought by studying examples of silicide, III-V and II-VI interfaces in detail, with strong theoretical and conventional surface diagnostics back-up. Six main epioptic techniques will be used: reflectance anisotropy and reflectance difference spectroscopies, spectroscopic ellipsometry, optical second harmonic generation, Raman scattering and photoreflectance. An interdisciplinary team has been assembled to produce a vertically integrated structure: theoretical and experimental physicists, materials scientists, crystal growers and materials analysts.
EASI has already demonstrated the feasibility of using optical probes to monitor growth of thin-film IT materials with submonolayer resolution in situ and under all growth conditions. Implementing these new characterisation techniques should result in improved materials and higher yields for the fabrication of future IT semiconductor devices.
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