Method and apparatus for inspecting patterned thin films using diffracted beam ellipsometry
First Claim
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1. In an optical system for inspecting an object, a method of inspecting a repeating pattern on the object, comprising the steps of:
- (a) illuminating the object with substantially monochromatic light;
(b) forming a diffracted beam from the substantially monochromatic light, the diffracted beam comprising a plurality of diffracted beam components, each having a respective polarization state;
(c) blocking at least one of the diffracted beam components;
(d) detecting the diffracted beam components that are not blocked; and
(e) determining a polarization state of the diffracted beam based on the diffracted beam components that are not blocked.
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Abstract
A method and apparatus for inspecting a repeating pattern on an object using an optical inspection system to detect variations in the pattern. The object is illuminated with substantially monochromatic light. A diffracted beam is formed. The diffracted beam has a plurality of polarization components. At least one of the polarization components of the diffracted beam is blocked. Variations in the pattern are detected as light intensity variations in the polarization components that are not blocked.
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Citations
23 Claims
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1. In an optical system for inspecting an object, a method of inspecting a repeating pattern on the object, comprising the steps of:
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(a) illuminating the object with substantially monochromatic light; (b) forming a diffracted beam from the substantially monochromatic light, the diffracted beam comprising a plurality of diffracted beam components, each having a respective polarization state; (c) blocking at least one of the diffracted beam components; (d) detecting the diffracted beam components that are not blocked; and (e) determining a polarization state of the diffracted beam based on the diffracted beam components that are not blocked. - View Dependent Claims (2, 3, 11)
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4. In an optical system for inspecting an object, a method of inspecting a repeating pattern on the object, comprising the steps of:
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(a) illuminating the object with substantially monochromatic light; (b) forming a diffracted beam from the substantially monochromatic light, the diffracted beam comprising a plurality of diffracted beam components, each having a respective polarization state, the diffracted beam having an average polarization; (c) blocking a diffracted beam component having a polarization state equal to the average polarization, to substantially null the diffracted beam; and (d) detecting the diffracted beam components that are not blocked. - View Dependent Claims (5, 6, 7, 8, 9, 10, 21)
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12. In an optical system for inspecting an object, having a source of substantially monochromatic light, an elliptical polarizer positioned between the light source and the object, light detecting means, and an analyzing polarizer positioned between the object and the light detecting means;
- a method of inspecting a repeating pattern on an object to detect variations in the pattern, comprising the steps of;
(a) illuminating the object with substantially monochromatic light from the light source, the monochromatic light including a first light component having a polarization state that is parallel to a plane of incidence of the monochromatic light and a second light component having a polarization state that is perpendicular to the plane of incidence; (b) forming, from the substantially monochromatic light, a diffracted beam that is incident upon the light detecting means, the diffracted beam comprising a plurality of diffracted beam components, each diffracted beam component having a respective polarization state; (c) adjusting at least one of the elliptical polarizer and the analyzing polarizer to block at least one of the diffracted beam components; and (d) detecting variations in the pattern as light intensity variations in the diffracted beam components that are not blocked.
- a method of inspecting a repeating pattern on an object to detect variations in the pattern, comprising the steps of;
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13. In an optical system for inspecting an object, a method of inspecting a repeating pattern on the object, comprising the steps of:
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(a) illuminating the object with substantially monochromatic light including a first light component having a polarization state that is parallel to a plane of incidence of the substantially monochromatic light and a second light component having a polarization state that is perpendicular to the plane of incidence; (b) forming a diffracted beam from the substantially monochromatic light, the diffracted beam comprising a plurality of diffracted beam components, each diffracted beam component having a respective polarization state; (c) blocking at least one of the diffracted beam components; (d) detecting the diffracted beam components that are not blocked; and (e) determining a polarization state of the diffracted beam based on the diffracted beam components that are not blocked. - View Dependent Claims (14)
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15. An optical system for inspecting an object, comprising:
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means for illuminating the object with substantially monochromatic light including a first light component having a polarization state that is parallel to a plane of incidence of the substantially monochromatic light and a second light component having a polarization state that is perpendicular to the plane of incidence; means for forming, from the substantially monochromatic light, a diffracted beam that emanates from the object, the diffracted beam comprising a plurality of diffracted beam components, each diffracted beam component having a respective polarization state, the diffracted beam having an average polarization; means for blocking a diffracted beam component that is equal in polarization to the average polarization, thereby substantially nulling the diffracted beam; and means for detecting the diffracted beam components that are not blocked. - View Dependent Claims (16, 17, 18, 19, 20, 22)
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23. In an optical system for inspecting an object, a method of inspecting a repeating pattern on the object, comprising the steps of:
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(a) illuminating the object with substantially monochromatic light; (b) forming a diffracted beam from the substantially monochromatic light, the diffracted beam comprising a plurality of diffracted beam components, each having a respective polarization state, the diffracted beam having an average polarization; (c) blocking at least one of the diffracted beam components; (d) detecting the diffracted beam components that are not blocked; (e) forming an additional diffracted beam having an additional average polarization and a plurality of additional diffracted beam components, the additional average polarization being different from the average polarization of the diffracted beam formed in step (b); (f) blocking one of the additional diffracted beam components; (g) detecting light intensity variations in the additional diffracted beam; and (h) subtracting the light detected during step (g) from the light detected during step (d), thereby to detect variations in the repeating pattern.
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Specification