Focusing control mechanism, and inspection apparatus using same
First Claim
1. A focusing control mechanism for focusing an objective lens when observing an object under inspection using the objective lens, the mechanism comprising:
- a distance sensor provided in a fixed geometric relation to the objective lens;
a storage means for storing data representing the shape of a convex or concave pattern of the object under inspection and data representing a spatial sensitivity distribution of the distance sensor;
means for moving either or both of the objective lens and object under inspection relatively in direction towards or away from each other; and
means for controlling the operation of the moving means;
the controlling means calculating, based on the data representing the shape of convex or concave pattern of the object under inspection and data representing the spatial sensitivity distribution of the distance sensor, both stored in the storage means, a deviation of the shape of a convex or concave pattern recognized by the distance sensor from the real shape of convex or concave pattern, to provide a correction value, compensating for an output from the distance sensor with the correction value to determine a target moving distance, and controlling the operation of the moving means according to the target moving distance.
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Accused Products
Abstract
To properly focus an ultraviolet objective lens by the use of a distance sensor even when inspecting an object having a larger step than the focal depth of the objective lens, a difference between the real shape of a convex or concave pattern in each of dies formed on a semiconductor wafer 100 to be inspected and the shape (false shape) of a convex or concave pattern the distance sensor 8 recognizes, is calculated as a correction value C2 intended for use to compensate for an influence of the step in the die. The output from the distance sensor 8 is compensated with the correction value C2 to determine an accurate target moving distance, and an inspection stage 2 is driven accordingly to the target moving distance to automatically focus the ultraviolet objective lens.
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Citations
7 Claims
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1. A focusing control mechanism for focusing an objective lens when observing an object under inspection using the objective lens, the mechanism comprising:
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a distance sensor provided in a fixed geometric relation to the objective lens;
a storage means for storing data representing the shape of a convex or concave pattern of the object under inspection and data representing a spatial sensitivity distribution of the distance sensor;
means for moving either or both of the objective lens and object under inspection relatively in direction towards or away from each other; and
means for controlling the operation of the moving means;
the controlling means calculating, based on the data representing the shape of convex or concave pattern of the object under inspection and data representing the spatial sensitivity distribution of the distance sensor, both stored in the storage means, a deviation of the shape of a convex or concave pattern recognized by the distance sensor from the real shape of convex or concave pattern, to provide a correction value, compensating for an output from the distance sensor with the correction value to determine a target moving distance, and controlling the operation of the moving means according to the target moving distance. - View Dependent Claims (2, 3)
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4. An inspection apparatus comprising:
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an illuminating means for illuminating an object under inspection with an illumination light converged by an objective lens;
an imaging means for imaging the object under inspection;
illuminated by the illuminating means;
an inspecting means for processing an image picked up by the imaging means to inspect the object under inspection;
a distance sensor provided in a fixed geometric relation to the objective lens;
a storage means for storing data representing the shape of a convex or concave pattern of the object under inspection and data representing a spatial sensitivity distribution of the distance sensor;
means for moving either or both of the objective lens and object under inspection relatively in direction towards or away from each other; and
means for controlling the operation of the moving means;
the controlling means calculating, based on the data representing the shape of convex or concave pattern of the object under inspection and data representing the spatial sensitivity distribution of the distance sensor, both stored in the storage means, a deviation of the shape of a convex or concave pattern recognized by the distance sensor from the real shape of convex or concave pattern, to provide a correction value, compensating for an output from the distance sensor with the correction value to determine a target moving distance, and controlling the operation of the moving means according to the target moving distance. - View Dependent Claims (5, 6, 7)
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Specification