摘要:
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.
摘要:
An optical system includes a photolithography system, a low coherence interferometer, and a detector. The photolithography system is configured to illuminate a portion of an object with a light pattern and has a reference surface. The low coherence interferometer has a reference optical path and a measurement optical path. Light that passes along the reference optical path reflects at least once from the reference surface and light that passes along the measurement optical path reflects at least once from the object. The detector is configured to detect a low coherence interference signal including light that has passed along the reference optical path and light that has passed along the measurement optical path. The low coherence interference signal is indicative of a spatial relationship between the reference surface and the object.
摘要:
A method including comparing information derivable from a scanning interferometry signal for a first surface location of a test object to information corresponding to multiple models of the test object, wherein the multiple models are parametrized by a series of characteristics for the test object. The information corresponding to the multiple models may include information about at least one amplitude component of a transform of a scanning interferometry signal corresponding to each of the models of the test object.
摘要:
A method including comparing information derivable from a scanning interferometry signal for a first surface location of a test object to information corresponding to multiple models of the test object, wherein the multiple models are parametrized by a series of characteristics for the test object. The derivable information being compared may relate to a shape of the scanning interferometry signal for the first surface location of the test object.
摘要:
An interferometry method includes: imaging test light reflected from at least a first portion of a test surface to interfere with reference light on a camera and form an interference pattern, wherein the imaging defines a depth of focus for the light reflected from the test surface, and wherein the test light and reference light are derived from a common source; varying an optical path length difference between the test light and reference light over a range larger than the depth of focus, wherein the optical path length difference corresponds to a difference between a first optical path between the common source and the camera for the test light and a second optical path between the common source and the camera for the reference light; and maintaining the first portion of the test surface within the depth of focus as the optical path length difference is varied.
摘要:
A method including: providing a low coherence scanning interferometry data for at least one spatial location of a sample having multiple interfaces, wherein the data is collected using a low coherence scanning interferometer having an illumination geometry and an illumination frequency spectrum, and wherein the data comprises a low coherence scanning interferometry signal having multiple regions of fringe contrast corresponding to the multiple interfaces; and determining a distance between at least one pair of interfaces based on a distance between the corresponding regions of fringe contrast and information about the illumination geometry.
摘要:
An optical system includes a photolithography system, a low coherence interferometer, and a detector. The photolithography system is configured to illuminate a portion of an object with a light pattern and has a reference surface. The low coherence interferometer has a reference optical path and a measurement optical path. Light that passes along the reference optical path reflects at least once from the reference surface and light that passes along the measurement optical path reflects at least once from the object. The detector is configured to detect a low coherence interference signal including light that has passed along the reference optical path and light that has passed along the measurement optical path. The low coherence interference signal is indicative of a spatial relationship between the reference surface and the object.
摘要:
Conical surfaces (and other complex surface shapes) can be interferometrically characterized using a locally spherical measurement wavefront (e.g., spherical and aspherical wavefronts). In particular, complex surface shapes are measured relative to a measurement point datum. This is achieved by varying the radius of curvature of a virtual surface corresponding to a theoretical test surface that would reflect a measurement wavefront to produce a constant optical path length difference (e.g., zero OPD) between the measurement and reference wavefronts.
摘要:
A method including comparing information derivable from a scanning interferometry signal for a first surface location of a test object to information corresponding to multiple models of the test object, wherein the multiple models are parametrized by a series of characteristics for the test object. The derivable information being compared may relate to a shape of the scanning interferometry signal for the first surface location of the test object.
摘要:
In certain aspects, the invention features an interferometry system that utilizes coupled cavities (e.g., at least one remote cavity and a main cavity) and an extended light source. The remote cavity and the main cavity can have similar optical properties (e.g., similar numerical apertures (NA's)), allowing them to introduce offsetting, and therefore compensating, non-zero optical path differences (OPD's) between the measurement and reference beams without degrading interference fringe contrast due to source spatial coherence. In other words, for each non-zero OPD in the main cavity there exists a configuration of the remote cavity such that the total OPD between test and reference chief rays, and between test and reference marginal rays is substantially zero.