Grazing incidence interferometer and method
AssigneeZygo Corporation
InventorPeter de Groot
Life of this patent
Estimating the term…
Abstract
A two-beam interferometer illuminates a sample surface with light at grazing incidence angles for the purpose of analyzing a surface characteristic such as surface topography. The interferometer includes a diffractive-optic beam splitter, which separates an incoming light beam into measurement and reference beams and a diffractive-optic beam combiner, which produces an output beam by interfering portions of the reference beam with reflected portions of the measurement beam. Those portions of the reference wavefront and the measurement wavefront that interfere originate from substantially the same portion of the initial illumination wavefront.
Claims88
A two-beam grazing incidence interferometer for analyzing a surface of a sample, comprising:
- a diffractive-optic beam splitter to use amplitude division to separate at least a portion of an initial wavefront generated by a light source into a reference wavefront and a measurement wavefront;
- a diffractive-optic beam combiner located to generate an output wavefront by interfering portions of the reference wavefront with portions of the measurement wavefront, the portions of the measurement wavefront having undergone a reflection from the sample surface only once and at a grazing angle, the interfering portions of the reference and the measurement wavefronts originating from substantially the same portions of the initial illumination wavefront.
A two-beam grazing incidence interferometer for analyzing a surface of a sample, comprising:
- a birefringent beam splitter for separating an initial wavefront produced by a light source into reference and measurement wavefronts;
- and
- a birefringent beam combiner, located to generate an output wavefront by interfering corresponding portions of the reference and the measurement wavefronts, the portions of the measurement wavefront being reflected off the sample surface only once and at a grazing angle, each pair of corresponding portions of the reference and the measurement wavefronts originating from substantially the same portion of the initial illumination wavefront.
A method for performing interferometry with light reflected off a sample at a grazing angle, said method comprising:
- splitting an incoming wavefront into first and second beams;
- reflecting portions of the second beam off of the sample surface at a grazing angle;
- and
- intefering portions of the first beam with the portions of the second beam by combining the portions of the first and second beams which have the relative wavefront relation of the two beams leaving the splitter.
An interferometer to analyze light reflected from a sample surface at a grazing angle, said interferometer comprising:
- an optical element to form first and second beams by respectively reflecting and transmitting portions of an incoming beam;
- at least one reflector to redirect a portion of the second beam back towards the optical element which combines the first beam and the reflected back portion of the second beam without a relative wavefront inversion, the portion of the second beam having reflected off the sample surface only once before being combined with the first beam at the optical element.
Dependencies are inferred from the claim text.