Metrology of Silicon Wafers through Synchrotron Section Topography and X-ray Diffraction Imaging

X-ray metrology, a nondestructive characterization technique, was used to evaluate the warpage induced in a silicon (Si) wafer on a substrate with a predefined warpage. Section topography (ST) images were recorded at a synchrotron radiation source and were validated using a laboratory-based X-ray diffraction imaging (XRDI) system. Topography images and line scans were collected from the entire wafer at multiple 90° rotations. The topography images were processed using our new custom-built image-processing user interface called MasqueTron to extract the angular offset data. The angular offset data and full width at half maximum (FWHM) data were also collected through line scans using the laboratory-based technique. All these data were the input of a methodology to produce 3-D maps of the warpage and surface dislocations. The laboratory-based results are compelling to synchrotron topography data and agree well with the optical profilometry reported in the literature. The technique has the potential to be developed further to image the warpage and cracks induced in the Si wafer inside the packaged chips under thermo-mechanical stress which is imposed on the wafer during fabrication and encapsulation during the manufacturing process. The laboratory-based imaging techniques require further development to automat imaging the warpage of the entire wafer and to reduce the scanning time from days and hours to seconds as can be done at a synchrotron radiation source. The warpage of the wafer was calculated to be 3μ m and convex in shape.