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AssigneeKLA-Tencor Corporation
InventorsYung-Ho Chuang, David Shafer, Bin-Ming B. Tsai, J. Joseph Armstrong
Estimating the term…
A system for multiple mode imaging is disclosed herein. The system is a catadioptric system preferably having an NA greater than 0.9, highly corrected for low and high order monochromatic aberrations. This system uses unique illumination entrances and can collect reflected, diffracted, and scattered light over a range of angles. The system includes a catadioptric group, focusing optics group, and tube lens group. The catadioptric group includes a focusing mirror and a refractive lens/mirror element. The focusing optics group is proximate to an intermediate image, and corrects for aberrations from the catadioptric group, especially high order spherical aberration and coma. The tube lens group forms the magnified image. Different tube lens groups can be used to obtain different magnifications, such as a varifocal tube lens group to continuously change magnifications from 20 to 200×. Multiple imaging modes are possible by varying the illumination geometry and apertures at the pupil plane. Imaging modes include bright-field, full sky, ring dark-field, inverted ring dark-field, directional dark-field, double dark-field, Manhattan geometry, confocal bright-field, confocal dark-field, conoscopic, etc. Illumination can enter the catadioptric optical system using an auxiliary beamsplitter or mirror, or through the catadioptric group at any angle from 0 to 85 degrees from vertical. Multiple beams at multiple angles may be used for illumination. The high NA catadioptric system can also have a relayed pupil plane, used to select different imaging modes, providing simultaneous operation of different imaging modes, Fourier filtering, and other pupil shaping operations.
A method for providing dark field imaging, comprising the steps of:
A method of providing imaging for an object using dark field techniques, comprising:
A system for providing dark field imaging, comprising:
A method for providing an object image, comprising the steps of:
A method of imaging an object, comprising:
An optical system for imaging an object, comprising:
A system for imaging an object, comprising:
Dependencies are inferred from the claim text.
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Monitoring the printed patterns: defects, e.g. optical inspection of patterned layer for defects
Anamorphotic objectives: with variable magnification
Optical objectives specially designed for the purposes specified below: telecentric objectives or lens systems
Systems with reflecting surfaces, with or without refracting elements: catadioptric systems
Term end not estimated
1. Field of the Invention
The present invention relates generally to a method and apparatus for multiple mode imaging, and more particularly to catadioptric optical systems used for dark field imaging applications.
2. Description of the Related Art
FIG. 1 is a directional dark field system which illuminates a object using angles of incidence up to 85 degrees from normal;
FIG. 2a illustrates a side view of a double dark field design system which illuminates the object at a relatively high angles of incidence;
FIG. 2b is a top view of the double dark field system;
Referring now to FIG. 7, shown is a figure illustrating an apparatus that combines the functions of several imaging systems. This apparatus, based on a high NA catadioptric optical design, is a narrow band optical system having an NA greater than 0.90 and is highly corrected for low and high order monochromatic aberrations. The system of the present invention may have a numerical aperture of greater than 0.65. Preferably the numerical aperture is greater than 0.90. The field size preferably ranges from 0.5 to 2.0 mm.
This high NA catadioptric optical design has been optimized with emphasis on manufacturability and flexibility for a multiple mode optical inspection system. Previous catadioptric systems were primarily optimized for broad band performance. For this reason these prior systems had NAs limited to 0.90 and field sizes limited to 1 mm. Previous designs had a tendency to be highly complicated with tight manufacturing tolerances and required two glass materials, which could add considerable cost.
The high NA catadioptric optical system disclosed herein may have an NA in air up to 0.99 and a field size of greater than 1 mm. Such a system has relaxed manufacturing tolerances and only requires a single glass material. Use of a single glass material in the catadioptric system is very advantageous when the system is optimized for the spectrum below 300 nm because only a few glasses with high transmission are available.