Optical flat

Abstract: A triple-axis X-ray spectrometer has been used to examine the reflectivity and surface scattering from silicon wafers with various thicknesses of oxide surface layers (from 10 to 100 AA). The X-ray techniques provide accurate information on the thickness of the surface oxide layer, the electron density of the roughness of both the surface interface and the substrate to layer interface. The use of a triple-axis spectrometer has two important advantages over the more conventional X-ray reflectivity techniques. It allows accurate reflectivity measurements to be carried out on samples which are, macroscopically, far from flat, such as semiconductor wafers in preparation for device fabrication. It also enables the intensity of the specularly reflected X-ray beam to be measured without contamination from the appreciable small-angle scattering which can occur from a microscopically rough surface. To illustrate this point, reflectivity measurements from a high-quality glass optical flat are also described.

Abstract: An optically focusing X-ray diffraction camera is used to obtain low angle diffraction photographs. Focusing is accomplished by total external reflection either by one elastically bent optical flat to form a line focus, or by two crossed flats to form a point focus. The beam is partially monochromatized and its intensity is high. Spacings greater than 600 A have been resolved.

Abstract: A method for the absolute calibration of a flat optical surface is described. An algorithm which utilizes the orthogonal properties of the Zernike polynomials was used on interferometric data to fabricate and certify three 10-inch Zerodur reference flats to λ/100 peak-to-valley quality.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: Complex aspheric optical surfaces may be made reliably and relatively rapidly by a method in which one surface of a relatively thick glass block is ground and polished to the desired aspheric surface, which may be tested in a system including master optics of the remaining components. This master die block may then be used to generate reverse die plates by drawing thin glass blanks against the configured surface thereof and polishing to an optical flat. These reverse die plates are then mounted on a base die block and deformable glass blanks are drawn against the configured surface thereof and the opposite surface polished to an optical flat. Upon removal, the glass blanks assume a curvature identical to the original aspheric surface of the master die block.