Dark field imaging defect inspection system for repetitive pattern integrated circuits
First Claim
1. A method of locating defects on a surface having a repetitive pattern comprising the steps of:
- a) illuminating the surface with a beam of monochrome light at an angle with respect to the surface of the wafer of between 8 degrees and a predetermined maximum angle;
b) capturing any light which is scattered from the surface at angles greater than the predetermined maximum angle;
c) spatially filtering the captured light to attenuate spatial frequencies corresponding to the repetitive pattern relative to spatial frequencies corresponding to the defects;
d) focusing the spatially filtered light into an image, wherein images of the defects are accentuated relative to the image of the repetitive pattern.
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Accused Products
Abstract
An optical inspection system for patterned semiconductor wafers generates a dark field image of the wafer by applying a collimated beam of monochrome light at an incident angle with respect to the surface of the wafer of between 8° and a maximum angle defined by the numerical aperture of the imaging system and collecting the light which is scattered at angles approximately normal to the surface of the wafer and within the numerical aperture of the imaging system. In addition, the incident light is at an angle of 45° in the surface plane of the wafer with respect to the rectangular lines which predominate in the pattern. Before forming the dark field image, the collected light is passed through a Fourier transform filter which substantially attenuates spatial frequency components corresponding to the pattern. In the resultant dark field image, defects in the pattern and contaminating particles are accentuated relative to the pattern features.
189 Citations
16 Claims
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1. A method of locating defects on a surface having a repetitive pattern comprising the steps of:
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a) illuminating the surface with a beam of monochrome light at an angle with respect to the surface of the wafer of between 8 degrees and a predetermined maximum angle; b) capturing any light which is scattered from the surface at angles greater than the predetermined maximum angle; c) spatially filtering the captured light to attenuate spatial frequencies corresponding to the repetitive pattern relative to spatial frequencies corresponding to the defects; d) focusing the spatially filtered light into an image, wherein images of the defects are accentuated relative to the image of the repetitive pattern. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus which may be used to locate defects on a surface having a repetitive pattern comprising:
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a) illuminating means for illuminating the surface with at least one beam of monochrome light at a desired angle with respect to the surface of the wafer of between 8 degrees and a predetermined maximum angle; b) lens means positioned with an optical axis normal to the surface for capturing light which is scattered from the surface at angles within the numerical aperture of the lens means, wherein the numerical aperture of the lens means defines said predetermined maximum angle; c) filtering means for spatially filtering the captured light to attenuate spatial frequencies corresponding to the repetitive pattern relative to spatial frequencies corresponding to the defects; and d) imaging means for focusing the spatially filtered light into an image, wherein images of the defects are accentuated relative to the image of the repetitive pattern. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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14. A method of locating defects on a surface having a repetitive pattern comprising the steps of:
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a) illuminating the surface with a beam of monochrome light at an angle of between 8 and 45 degrees with respect to the surface; b) capturing any light which is scattered from the surface at angles between 45 degrees and 90 degrees; c) spatially filtering the captured light to attenuate spatial frequencies corresponding to the repetitive pattern relative to spatial frequencies corresponding to the defects; d) focusing the spatially filtered light into an image, wherein components of the image representing the defects on the surface are accentuated relative to components of the image representing the repetitive pattern. - View Dependent Claims (15, 16)
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Specification