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Title: Surface characterisation of semiconductor materials
Author: Hart, Linda
ISNI:       0000 0001 3541 181X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1990
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Several well-established x-ray characterisation techniques have been developed to obtain high resolution for applications where high strain sensitivity and surface sensitivity are important X-ray methods are compared with other characterisation methods and a range of x-ray techniques is reviewed. The double-axis diffractometer and its capabilities are described. Dynamical x-ray diffraction theory for distorted crystals, and the theory of diffuse scattering from randomly distributed defects are reviewed. X-ray reflectivity theory is also covered. Several complementary characterisation techniques have been developed: Double-axis diffiactometry using a four-reflection beam conditioner to measure surface scattering in the rocking-curve tails, topography using highly strain sensitive conditions at grazing incidence, with both a conventional x-ray source and synchrotron radiation, and energy dispersive reflectometry using a high-energy x-ray source. A range of samples has been characterised, including silicon wafers machined and polished under different conditions and from different manufacturers, silicon epiwafers, and ion implanted silicon. In the rocking-curve analysis, modelling and simulation were used to determine the residual surface strain-depth profiles. Silicon wafers polished using a mechanical- chemical technique were found to have a lattice expansion of 4 to 8 parts per million near the surface, decreasing linearly to zero at up to one micron depth. Topography was used to detect strains of order 10-7 in polished silicon wafers. Strains were measured at the edges of polished areas which had been etched away, enabling strain relaxation. Energy dispersive reflectometry enabled determination of surface roughness of polished silicon wafers, down to Angstrom resolution. The techniques developed can be used widely in the characterisation of semiconductor materials. Rocking-curve analysis in particular is an extremely useful tool for the assessment of wafer quality and monitoring and development of the wafer production process.
Supervisor: Not available Sponsor: Science and Engineering Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics ; TK Electrical engineering. Electronics Nuclear engineering