Abstract: A system and method are provided for obtaining mapping profiles of transparent objects having a plurality of reflective surfaces. The object, the surfaces of which are to be mapped, is placed in an unequal path interferometer including a reference surface located a predetermined distance from the object. Coherent light is supplied in the interferometer from a tunable source; and multiple optical interferograms for each of the plurality of reflective surfaces are simultaneously recorded. These interferograms are simultaneously extracted through the use of a dynamically generated weighted least-square fitting technique; which separates interferograms from a set of superimposed interferograms to obtain a given interferogram for any one of the surfaces, free from errors resulting from the existence of the other interferograms.

Abstract: A method and apparatus to linearize the phase shifts produced by the wavelength-varying driving mechanism of an interferometer used in phase shift interferometry for the measurement of multiple reflective surfaces first calibrates a sequence of physical values used as the input to the driving mechanism to produce a known linear or a known constant phase shift increment between any two adjacent interferograms. The calibration process, in essence, involves the determination of the sequence of physical values, such as the voltage change with respect to the time, through the process of iteration. This sequence then is used as an input to the phase shift driving mechanism for ongoing operation of the system, thereby compensating for non-linear characteristics of the system.

Abstract: The present invention consists of a technique and device for measuring the thickness variation and shape of wafers or other polished opaque plates. A combination of two improved phase-shifting Fizeau interferometers is used to simultaneously measure the single-sided distance maps between each side of the wafer and the corresponding reference flat, with the thickness variation and shape being calculated from these data. Provisions are made to determine and eliminate the shape and tilt of the reference surfaces, and also to facilitate the correct overlay of the two single-sided measurements for the calculation of thickness variation and shape.

Abstract: A device is disclosed for supporting semiconductor wafers or other polished, opaque plates for processing or metrology in a vertical orientation, where the wafer loading and unloading occurs in a horizontal orientation. The device consists of a pallet designed with an opening such that both sides of the wafer are exposed. The wafer is loaded into the pallet to rest on three fixed rest members extending a short distance into the opening. Moving clamp members on the frame are located for movement toward or away from the corresponding rest members. Two cylindrical rest pins are located on axes parallel to the central axis of the opening to permit the wafer to rest under the force of gravity on the rest pins when the frame is rotated to its vertical position. Special provisions are made to minimize the effects of mechanical vibration of the wafer while insuring a robust physical restraint of the wafer within the apparatus without inducing mechanical stresses which could influence the shape of the wafer.

Abstract: A device is disclosed for supporting semiconductor wafers or other polished, opaque plates for processing or metrology in a vertical orientation, where the wafer loading and unloading occurs in a horizontal orientation. The device consists of a pallet designed with an opening such that both sides of the wafer are exposed. The wafer is loaded into the pallet to rest on three fixed rest members extending a short distance into the opening. Moving clamp members on the frame are located for movement toward or away from the corresponding rest members. Two cylindrical rest pins are located on axes parallel to the central axis of the opening to permit the wafer to rest under the force of gravity on the rest pins when the frame is rotated to its vertical position. Special provisions are made to minimize the effects of mechanical vibration of the wafer while insuring a robust physical restraint of the wafer within the apparatus without inducing mechanical stresses which could influence the shape of the wafer.

Abstract: The present invention consists of a technique and device for measuring the thickness variation and shape of wafers or other polished opaque plates. A combination of two improved phase-shifting Fizeau interferometers is used to simultaneously measure the single-sided distance maps between each side of the wafer and the corresponding reference flat, with the thickness variation and shape being calculated from these data. Provisions are made to determine and eliminate the shape and tilt of the reference surfaces, and also to facilitate the correct overlay of the two single-sided measurements for the calculation of thickness variation and shape.

Abstract: A method and apparatus to linearize the phase shifts produced by the wavelength-varying driving mechanism of an interferometer used in phase shift interferometry for the measurement of multiple reflective surfaces first calibrates a sequence of physical values used as the input to the driving mechanism to produce a known linear or a known constant phase shift increment between any two adjacent interferograms. The calibration process, in essence, involves the determination of the sequence of physical values, such as the voltage change with respect to the time, through the process of iteration. This sequence then is used as an input to the phase shift driving mechanism for ongoing operation of the system, thereby compensating for non-linear characteristics of the system.

Abstract: A system and method are provided for obtaining mapping profiles of transparent objects having a plurality of reflective surfaces. The object, the surfaces of which are to be mapped, is placed in an unequal path interferometer including a reference surface located a predetermined distance from the object. Coherent light is supplied in the interferometer from a tunable source; and multiple optical interferograms for each of the plurality of reflective surfaces are simultaneously recorded. These interferograms are simultaneously extracted through the use of a dynamically generated weighted least-square fitting technique, which separates interferograms from a set of superimposed interferograms to obtain a given interferogram for any one of the surfaces, free from errors resulting from the existence of the other interferograms.

Abstract: The absolute interferometric measurement of the shape of either flat, or spherical surfaces is achieved by incorporating a Fizeau-interferometer and a test piece holder capable of several degrees of freedom of movement relative to the reference position in the interferometer. A data acquisition and processing technique inter-compares three test parts in various combinations. Full surface absolute maps for each of the test pieces are determined using at least two different rotational positions of one test-piece to yield rotationally sheared maps of that surface. An optimized numerical reconstruction algorithm employing linear filtering and superposition of different angular shear spectra in the angular frequency domain is employed. The method does not require any assumptions about the surfaces under test; and it has low error propagation, even in the case of high spatial resolution.

Abstract: A low coherent noise interferometer system incorporates an improved low spatial coherence source obtained from a laser light source which supplies a beam of light through a beam-shaping lens to the first one of a set of two cascaded diffusers. One of the diffusers is dynamically changing, provided by a rotating ground glass disk. The diffusers then supply light to an interferometer of a two-beam interferometer configuration, such as Fizeau, Twyman-Green or Mach-Zehnder. In one embodiment, the first diffuser is the rotating ground glass diffuser and the second diffuser is a multi-mode optical fiber. The exit face of the fiber represents the spatially incoherent extended light source for the interferometer. The laser, the motor for driving the first diffuser and the diffusers themselves all are mounted on a separate base from the base on which the interferometer is mounted.

Abstract: An interferometer particularly suitable for testing the flatness of transparent plano-parallel test pieces employs an extended spatially non-coherent light source. The source is directed to a first beam splitter at an angle of incidence other than normal; and the beam is split into first and second spatially non-coherent divergent wavefronts. A reference surface reflects the first wavefront and a surface under test reflects the second wavefront. A second beam splitter receives and recombines the first and second reflected spatially non-coherent wavefronts; and an interference detector is located to receive the combined reflected wavefronts to produce the interferogram. The distance traveled by the wavefronts from the first beam splitter to the detector is equal, and the optical characteristics of the light path traveled by both wavefronts is the same.

Abstract: A sheet flatness measuring system consists of a frame carrying a structured illumination system for producing illumination beneath the frame in a periodic pattern of opaque and illuminated lines. A flat base or table, having a surface parallel to the structured illumination system, is placed beneath the structured illumination system to be illuminated by it. A sheet of reflective or semi-reflective material, the flatness of which is to be measured, is placed on the table. The reflection of the structured illumination is viewed from the sheet a by video camera, typically mounted in a central location above the center of the table on which the sheet is placed. The structured illumination pattern is moved to different positions, and multiple video images are digitized and compared in a computer to calculate the local slope at each point or pixel in the image of the sheet viewed by the camera.