System and method for a displacement measurement
AssigneeNikon Corporation
InventorEric Peter Goodwin
Life of this patent
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Abstract
System and method for profiling of a surface with lateral scanning interferometer the optical axis of which is perpendicular to the surface. In-plane scanning of the surface is carried out with increments that correspond to integer number of pixels of an employed optical detector. Determination of height profile of a region-of-interest that is incomparably larger than a FOV of the interferometer objective is performed in time reduced by at least an order of magnitude as compared to time required for the same determination by a vertical scanning interferometer.
Claims20
A method for profiling a surface, the method comprising:
- determining a height profile of the surface based on phases of light distribution, formed in reflection of light by the surface with the use of an interferometer and containing interferometric fringes that are angularly tilted with respect to a direction of an in-plane scanning of the surface, while the surface is being scanned in said direction perpendicular to an optical axis of a sample arm of the interferometer in absence of angular inclination between said optical axis and a line that is perpendicular to the surface.
A method for profiling a surface, the method comprising:
- positioning the surface perpendicularly to an optical axis of an objective in a sample arm of the interferometer;
- configuring a reference arm of the interferometer to form interferometric fringes, at an optical detector of an optical system containing said interferometer, that are tilted with respect to a chosen axis when the surface is illuminated through the sample arm;
- and
- acquiring optical data from a distribution of light formed at said optical detector and containing said interferometric fringes while the surface is being scanned along the chosen axis in a plane of the surface.
An apparatus for profiling a surface under test (SUT), the apparatus comprising:
- a beam splitter positioned to divide a light beam from a light source into a measurement light beam and a reference light beam directed along a reference axis;
- and
- a reference reflector positioned in an optical path of the reference light beam, the reference reflector being inclined with respect to the reference axis,
- said beam splitter configured to direct said measurement light beam towards the SUT to irradiate said SUT and form a reflected measurement light beam, said reflected measurement light beam passing through the beam splitter to interfere with the reference light beam upon reflection thereof from the reference reflector.
Dependencies are inferred from the claim text.