The Characterization of Molybdenum/silicon Soft X-Ray Multilayers by Raman Spectroscopy and Other Techniques

Mo/Si multilayer mirrors provide to date the highest reflectivity for soft x-rays in the range of 13 to 15 nm. It has potential applications for soft x-ray lithography. This dissertation has characterized the annealing behaviors of Mo/Si multilayers by Raman spectroscopy and other correlated characterization techniques. The first part of the dissertation shows how the Raman spectroscopy system is improved by using a CCD detector. Several algorithms have been developed to eliminate the cosmic noise which is unique to this kind of detector. With this high quantum efficiency detector, we can study very low -light-level Raman spectroscopy with much faster data acquisition speed. The major accomplishment of the research reported here is the characterization of the annealing behavior of Mo/Si multilayers. Two peaks, located at 323 and 438 cm^{-1}, have been observed both in polycrystalline molybdenum silicide powder and one-hour 1000^circC annealed Mo/Si multilayers. This indicates that silicide has been formed at interfaces and is detectable, which provides the foundation for further studies. After high temperature annealing, in addition to the formation of silicide interfaces, the amorphous Si layers have crystallized. At this stage, the layer structure has been completely destroyed and the roughness of the interfaces and the surface have been increased. Both of these conditions will degrade the performance of the multilayer system. Further annealing studies show that the crystallization of Si layers and the formation of silicide through interdiffusion proceed concurrently during the annealing process.