Abstract: An interferometry method for determining information about a test object includes directing test light to the test object positioned at a plane, wherein one or more properties of the test light vary over a range of incidence angles at the plane, the properties of the test light being selected from the group consisting of the spectral content, intensity, and polarization state; subsequently combining the test light with reference light to form an interference pattern on a multi-element detector so that different regions of the detector correspond to different angles of the test light emerging from the test object, wherein the test and reference light are derived from a common source; monitoring the interference pattern using the multi-element detector while varying an optical path difference between the test light and the reference light; determining the information about the test object based on the monitored interference pattern.

Abstract: In general, in a first aspect, the invention features a system including an interferometer configured to direct test light to an overlay target and subsequently combine it with reference light to form an interference pattern, the test and reference light being derived from a common source, a multi-element detector, one or more optics to image the overlay target on the multi-element detector; and an electronic processor in communication with the multi-element detector. The overlay target includes a first pattern and a second pattern and the electronic processor is configured to determine information about the relative alignment between the first and second patterns.

Abstract: Systems are disclosed that include an interferometer configured to direct test light to an overlay test pad and subsequently combine it with reference light, the test and reference light being derived from a common source, one or more optics configured to direct at least a portion of the combined light to a multi-element detector so that different regions of the detector correspond to different illumination angles of the overlay test pad by the test light, the detector being configured to produce an interference signal based on the combined light, and an electronic processor in communication with the multi-element detector. The overlay test pad comprises a first patterned structure and a second patterned structure and the electronic processor is configured to determine information about the relative alignment between the first and second patterned structures based on the interference signal.

Abstract: A method includes fitting a function to a subset of reflectivity data comprising values for the reflectivity of a test object for different wavelengths, different scattering angles, and/or different polarization states; determining values for the function at certain wavelengths and scattering angles and/or polarization states; and determining information about the test object based on the determined values.

Abstract: A method for determining information about a test object includes combining two or more scanning interference signals to form a synthetic interference signal; analyzing the synthetic interference signal to determine information about the test object; and outputting the information about the test object. Each of the two or more scanning interference signals correspond to interference between test light and reference light as an optical path length difference between the test and reference light is scanned, wherein the test and reference light are derived from a common source. The test light scatters from the test object over a range of angles and each of the two or more scanning interferometry signals corresponds to a different scattering angle or polarization state of the test light.

Abstract: In certain aspects, interferometry methods are disclosed that include providing one or more interferometry signals for a test object, wherein the interferometry signals correspond to a sequence of optical path difference (OPD) values which are not all equally spaced from one another because of noise, providing information about the unequal spacing of the sequence of OPD values, decomposing each of the interferometry signals into a contribution from a plurality of basis functions each corresponding to a different frequency and sampled at the unequally spaced OPD values, and using information about the contribution from each of the multiple basis functions to each of the interferometry signals to determine information about the test object.

Abstract: In general, in one aspect, the invention features apparatus that includes a broadband scanning interferometry system including interferometer optics for combining test light from a test object with reference light from a reference object to form an interference pattern on a detector, wherein the test and reference light are derived from a common light source. The interferometry system further includes a scanning stage configured to scan an optical path difference (OPD) between the test and reference light from the common source to the detector and a detector system including the detector for recording the interference pattern for each of a series of OPD increments, wherein the frequency of each OPD increment defines a frame rate. The interferometer optics are configured to produce at least two monitor interferometry signals each indicative of changes in the OPD as the OPD is scanned, wherein the detector system is further configured to record the monitor interferometry signals.

Abstract: Interferometry system are disclosed that include a detector sub-system including a monitor detector, interferometer optics for combining test light from a test object with primary reference light from a first reference interface and secondary reference light from a second reference interface to form a monitor interference pattern on a monitor detector, wherein the first and second reference interfaces are mechanically fixed with respect to each other and the test light, a scanning stage configured to scan an optical path difference (OPD) between the test light and the primary and secondary reference light to the monitor detector while the detector sub-system records the monitor interference pattern for each of a series of OPD increments, and an electronic processor electronically coupled to the detector sub-system and the scanning stage, the electronic processor being configured to determine information about the OPD increments based on the detected monitor interference pattern.

Abstract: Deformations of a surface of a test object can be measured by attaching mirrors to a surface of a test object, each mirror having a reflective surface with a dimension and a radius of curvature smaller than those of the surface of the test object. Light is directed towards the mirrors and a reference surface, and interference patterns are generated using light reflected from the mirrors and the reference surface. Changes in the surface of the test object are determined based on the interference patterns.

Abstract: Systems are disclosed that include an interferometer configured to direct test light to an overlay test pad and subsequently combine it with reference light, the test and reference light being derived from a common source, one or more optics configured to direct at least a portion of the combined light to a multi-element detector so that different regions of the detector correspond to different illumination angles of the overlay test pad by the test light, the detector being configured to produce an interference signal based on the combined light, and an electronic processor in communication with the multi-element detector. The overlay test pad comprises a first patterned structure and a second patterned structure and the electronic processor is configured to determine information about the relative alignment between the first and second patterned structures based on the interference signal.

Abstract: An apparatus including: an interferometric objective comprising a beam splitter surface configured to separate input light into test light and reference light, and a reference surface configured to receive the reference light and direct it back to the beam splitter surface, which is configured to recombine the reference light with test light reflected from a test surface, the interferometric objective further comprising one or more optical elements positioned in the path of the input light and having positive or negative optical power, wherein the reference surface is curved and defines a window to pass the input light towards the beam splitter surface.

Abstract: Interferometry system are disclosed that include a detector sub-system including a monitor detector, interferometer optics for combining test light from a test object with primary reference light from a first reference interface and secondary reference light from a second reference interface to form a monitor interference pattern on a monitor detector, wherein the first and second reference interfaces are mechanically fixed with respect to each other and the test light, a scanning stage configured to scan an optical path difference (OPD) between the test light and the primary and secondary reference light to the monitor detector while the detector sub-system records the monitor interference pattern for each of a series of OPD increments, and an electronic processor electronically coupled to the detector sub-system and the scanning stage, the electronic processor being configured to determine information about the OPD increments based on the detected monitor interference pattern.

Abstract: In certain aspects, interferometry methods are disclosed that include providing one or more interferometry signals for a test object, wherein the interferometry signals correspond to a sequence of optical path difference (OPD) values which are not all equally spaced from one another because of noise, providing information about the unequal spacing of the sequence of OPD values, decomposing each of the interferometry signals into a contribution from a plurality of basis functions each corresponding to a different frequency and sampled at the unequally spaced OPD values, and using information about the contribution from each of the multiple basis functions to each of the interferometry signals to determine information about the test object.

Abstract: Apparatus include a microscope including an objective and a stage for positioning a test object relative to the objective, the stage being moveable with respect to the objective, and a sensor system, that includes a sensor light source, an interferometric sensor configured to receive light from the sensor light source, to introduce an optical path difference (OPD) between a first portion and a second portion of the light, the OPD being related to a distance between the objective lens and the stage, and to combine the first and second portions of the light to provide output light, a detector configured to detect the output light from the interferometric sensor, a fiber waveguide configured to direct light between the sensor light source, the interferometric sensor and the detector, a tunable optical cavity in a path of the light from the sensor light source and the interferometric sensor, and an electronic controller in communication with the detector, the electronic controller being configured to determine in

Abstract: In general, in one aspect, the invention features apparatus that includes a broadband scanning interferometry system including interferometer optics for combining test light from a test object with reference light from a reference object to form an interference pattern on a detector, wherein the test and reference light are derived from a common light source. The interferometry system further includes a scanning stage configured to scan an optical path difference (OPD) between the test and reference light from the common source to the detector and a detector system including the detector for recording the interference pattern for each of a series of OPD increments, wherein the frequency of each OPD increment defines a frame rate. The interferometer optics are configured to produce at least two monitor interferometry signals each indicative of changes in the OPD as the OPD is scanned, wherein the detector system is further configured to record the monitor interferometry signals.

Abstract: In general, in a first aspect, the invention features a system including an interferometer configured to direct test light to an overlay target and subsequently combine it with reference light to form an interference pattern, the test and reference light being derived from a common source, a multi-element detector, one or more optics to image the overlay target on the multi-element detector; and an electronic processor in communication with the multi-element detector. The overlay target includes a first pattern and a second pattern and the electronic processor is configured to determine information about the relative alignment between the first and second patterns.

Abstract: An apparatus including: an interferometric objective comprising a beam splitter surface configured to separate input light into test light and reference light, and a reference surface configured to receive the reference light and direct it back to the beam splitter surface, which is configured to recombine the reference light with test light reflected from a test surface, the interferometric objective further comprising one or more optical elements positioned in the path of the input light and having positive or negative optical power, wherein the reference surface is curved and defines a window to pass the input light towards the beam splitter surface.