Abstract: an apparatus including: a support structure; a stage configured to move relative to the support structure; a first reflection surface carried by one of the support structure and the stage; and a first interferometry system. The first interferometry system is configured to direct a first measurement beam to contact the first reflection surface and monitor changes in the position and orientation of the stage relative to the support structure along multiple degrees of freedom using the first measurement beam and no other measurement beam that contacts the first reflection surface. For example, the first measurement beam can define a first measurement axis and the multiple degrees of freedom can include at least two of: distance along the first measurement axis, pitch about the first measurement axis, and yaw about the first measurement axis.

Abstract: In general, in one aspect, the invention features a method that includes monitoring a position of a stage along a first measurement axis and a second measurement axis of a multi-axis interferometry system and determining a position of the stage with respect to another degree of freedom based on the monitored positions along the first and second axes and predetermined information about how the measurement axes deviate from being parallel to one another.

Abstract: A method of using an interferometric confocal microscope to measure features of a trench or via in a substrate, wherein the interferometric confocal microscope produces a measurement beam, the method involving: focusing the measurement beam at a selected location at or near the bottom of the trench or via to excite one or more guided-wave modes within the trench or via; measuring properties of a return measurement beam that is produced when the measurement beam is focused at the selected location, wherein the return measurement beam includes a component corresponding to a radiated field from the one or more guided-wave modes that are excited within the trench; and determining the features of the trench or via from the measured properties of the return measurement beam.

Abstract: Spatial filtering of beams in interferometry systems is used to reduce a displacement of the beams from an optical path corresponding to the path of the beams in an optimally-aligned system. By reducing beam displacement from the optical path, the system reduces the magnitude of beam shears and associated non-cyclic errors in linear and angular displacements measured by the interferometry systems.

Abstract: An interferometric system including: an interferometer that directs a measurement beam at an object point to produce a return measurement beam, focuses the return measurement beam to an image point in an image plane, and mixes the return measurement beam with a reference beam at the image point to form a mixed beam; a beam combining layer located at the image plane which is responsive to the mixed beam and produces an optical beam therefrom, wherein the layer comprises a thin film with an array of transmissive openings formed therein and further comprises a fluorescent material associated with each of the openings of the array of openings; a detector that is responsive to the optical beam from the beam combining layer; and an imaging system that directs the optical beam from the beam combining layer onto the detector.

Abstract: A method of detecting non-uniform ellipsometric properties of a substrate surface wherein the non-uniform ellipsometric properties are characterized by a characteristic dimension, the method involving: generating an input beam for illuminating a spot at a selected location on or in the substrate that has a size L that is substantially larger than the characteristic dimension; deriving a measurement beam and a reference beam from the input beam; directing the measurement beam onto the substrate as an incident measurement beam that illuminates the spot at that selected location to produce a scattered measurement beam; for each orientation of a plurality of different orientations of the reference beam relative to the scattered measurement beam, interfering the scattered measurement beam with the reference beam to produce a corresponding interference beam, wherein each of the different orientations of the reference beam is selected to produce a peak sensitivity for a portion of the scattered measurement beam that

Abstract: The invention features a system and method for reducing the contribution of cyclic errors to an interferometric position measurement of a movable stage. An initial interferometric position measurement of the stage is averaged with at least one additional measurement corresponding to a displacement(s) of the stage from its initial position. The displacements are selected to reduce the overall cyclic error contribution to an average position measurement. As a result, the average position of the stage can be measured more accurately than any of its individual positions. The average position can be used to more accurately determine the average position of an alignment mark on a wafer carried by the stage. Furthermore, the averaging described above can be applied to additional interferometric measurement axes.

Abstract: In general, in one aspect, the invention features an interferometer assembly for use in a lithography tool used for fabricating integrated circuits on a wafer, wherein the lithography tool includes a support structure and a stage for positioning the wafer relative to the support structure, the interferometer assembly including an interferometer configured to direct a measurement beam between the stage and the support structure and combine the measurement beam with another beam to form an output beam which includes a phase related to a position of the stage relative to the support structure, wherein the interferometer is mechanically secured to the lithography tool through an interferometer surface selected to cause the phase of the output beam to be insensitive to thermal changes of the interferometer over a range of temperatures.

Abstract: In one aspect, the invention features an angle-measuring interferometry system that includes an interferometer which during operation directs a measurement beam to contact a measurement object, the interferometer comprising a beam steering assembly having a beam steering element positioned to contact and direct the measurement beam and an electronic positioning system to selectively orient the beam steering element within the interferometer. The angle-measuring interferometry system also includes an angle measurement system which during operation calculates a change in angular orientation of the measurement object based on a measurement signal derived from the measurement beam, wherein the measurement signal is derived from at least one interferometric signal produced by combining at least a portion of the measurement beam with a second beam after the measurement beam contacts the measurement object.

Abstract: Spatial filtering of beams in interferometry systems is used to reduce a displacement of the beams from an optical path corresponding to the path of the beams in an optimally-aligned system. By reducing beam displacement from the optical path, the system reduces the magnitude of beam shears and associated non-cyclic errors in linear and angular displacements measured by the interferometry systems.

Abstract: Interferometric apparatus and methods by which the local surface characteristics of photolithographic mirrors or the like may be interferometrically measured in-situ to provide correction signals for enhanced distance and angular measurement accuracy. Surface characterizations along one or multiple datum lines in one or more directions may be made by measuring the angular changes in beams reflected off the surfaces during scanning operations to determine local slope and then integrating the slope to arrive at surface topology. The mirrors may be mounted either on the photolithographic stages or off the photolithographic stages on a reference frame.

Abstract: An interferometry system includes: i) a first polarizing beam splitter which during operation separates an input beam into a measurement beam and a reference beam; ii) a beam steering element positioned to direct the measurement beam, and not the reference beam, the measurement beam contacting the beam steering element; iii) an interferometer positioned to receive at least a portion of the measurement beam and direct it to a measurement object, which reflects it to define a return measurement beam, and wherein the interferometer is further positioned to receive at least a portion of the reference beam and direct it to a reference object, which reflects it to define a return reference beam; and (iv) an electronic control circuit coupled to the beam steering element. During operation the control circuit adjusts the orientation of the beam steering element in response to changes in the angular orientation of the measurement object.

Abstract: Spatial filtering of beams in interferometry systems is used to reduce a displacement of the beams from an optical path corresponding to the path of the beams in an optimally-aligned system. By reducing beam displacement from the optical path, the system reduces the magnitude of beam shears and associated non-cyclic errors in linear and angular displacements measured by the interferometry systems.

Abstract: In one aspect, the invention features a method, including using an interferometer in an interferometry system to produce an output beam comprising a phase related to an optical path difference between a path of a first beam and a path of a second beam, wherein the first beam contacts a measurement object at a first location and the first or second beam contacts the measurement object at a second location, and wherein the first and second locations are different, providing precalibrated information that accounts for contributions to the optical path difference caused by a deviation of the path of the first or second beam from a nominal beam path due to an imperfection of the measurement object at the first location and due to an imperfection of the measurement object at the second location, and determining a position of the measurement object with respect to at least one degree of freedom based on information derived from the output beam and the precalibrated information.

Abstract: Beam shear can be reduced in an interferometric system by conditioning an input beam prior to directing the input beam to an interferometer. Accordingly, apparatus and methods for conditioning an interferometer input beam are disclosed.

Abstract: A multiple source array for illuminating an object including: a reflective mask having an array of spatially separated apertures; at least one optic positioned relative to the mask to form an optical cavity with the mask; and a source providing electromagnetic radiation to the optical cavity to resonantly excite a mode supported by the optical cavity, wherein during operation a portion of the electromagnetic radiation built-up in the cavity leaks through the mask apertures towards the object.

Abstract: Methods and system for compensating for effects of changes and variations of gas refractivity in a measurement and/or reference beam path of an interferometer are disclosed.

Abstract: In general, in one aspect, the invention features a method, including interferometrically measuring first and second optical path lengths to a measurement object along respective first and second paths, wherein the measurement of the optical path lengths includes directing first and second measurement beams to reflect from the measurement object, measuring propagation directions of the first and second measurement beams, compensating the first measured optical path length for time-varying optical properties of gas in the first path based on the first and second measured optical path lengths and the first and second measured propagation directions.

Abstract: A light source for a spectroscopy unit that measures tissue includes a block for engaging tissue and a light source. The block is formed of translucent material. The light source is positioned in close proximity to the block either directly or through use of a light fiber. The light source produces light at a single wavelength or small range of wavelengths shorter than the desired range of wavelengths to be produced by the light source for the spectroscopy unit. A luminescent material is placed in the light path between light source and the tissue to produce the desired wavelength of light when pumped by the light source.

Abstract: A multi-axis interferometer includes a mounting block with first and second polarizing beam-splitter cubes contacting first and second faces of the mounting block. A beam-distribution system contacts a third face of the mounting block. The beam-distribution system is thus placed in optical communication with the first polarizing beam-splitter cube and the second polarizing beam-splitter cube.