Importance

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Abstract

An apparatus (2) that performs high resolution thickness metrology on a thin film layer of a wafer (24), includes a filtered white light source that forms a collimated monochromatic light beam (19). The filtered white light source includes a halogen lamp (10), a condensing lens (12), a circular aperture (14), a collimator lens (16), and a narrow band filter wheel (18). The collimated monochromatic light beam (19) is passed through a beamsplitter (60), a second collimator lens (20), a third collimator lens (22), and a lenslet array (38), such that a corresponding array of sample points (39) on the surface of the wafer (24) are irradiated with focused monochromatic light. A reflectance pattern is formed at each sample point (39) due to coherent interactions in the monochromatic light as it is reflected within the wafer structure (24). An image of each reflectance pattern is reflected off the surface of the wafer (24) and is directed onto a detector array (31) of a charge coupled device (CCD) camera (30). Each reflectance pattern image is displayed on the CCD camera detector array (31) and captured by the CCD camera (30). Each captured image is digitized by a digitizing circuit (34) and stored by a computer (36). The computer (36) then compares this measured reflectance data to reference reflectance data already stored so as to determine the thickness of the thin film layer at each sample point (39) on the wafer (24).

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First Claim