Wave Front Phase Imaging of Wafer Warpage : Advanced new metrology technique for blank incoming wafers

We present a new wafer metrology technique, Wave Front Phase Imaging (WFPI), for high speed measurement of wafer geometry including shape, flatness, nanotopography and even sub nm features found in roughness. WFPI acquires data of the entire wafer using a single image snapshot that provides depth data for every single pixel. The number of topography data points for the entire wafer will be proportional to the number of pixels in the image sensor. Sub nanometer depth resolution is achieved by using 2 cameras with optics that image the entire wafer, with the exact same field of view, at different conjugation planes. Monochromatic uncoherent light is illuminating the wafer and lateral resolution is determined by the lenses used for a specific field of view and the number of pixels offered by the image sensor. We show that WFPI can see warp and bow on a 2 inch wafer in addition to clearly resolving polishing artifacts in the roughness regime with dimensions well below the wavelength of the light.