System and method for finding the center of rotation of an R-theta stage
AssigneeTherma-Wave, Inc.
InventorsIlya Chizhov, Martin Ebert
Life of this patent
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Abstract
An optical inspection system and method which uses a procedure for determining an offset between a field of view and a center or rotation of an R-theta stage, or polar coordinate stage. Determining this offset allows the precise location of a site being inspected on a wafer to be determined. The system and method take advantage of the fact that in a R-theta system there can be only two positions for the R-theta stage that will position a particular site under the lens of the imaging system of the optical inspection system. By moving the stage from a first position where a particular site is positioned in the field of view, to the second position where the particular site is positioned in the field of view, the offset can be determined.
Claims21
An inspection system for inspecting samples, comprising:
- a polar coordinate stage having a chuck and a track, wherein the chuck and the track are coupled such that the chuck can be moved to different positions along the track, and wherein the chuck can be rotated about a center of rotation;
- an optical imaging system, having a field of view, which receives a probe beam reflected off a sample positioned on the chuck;
- and
- a processor system which controls the position of the chuck relative to the track, and uses first information derived from positioning a site on a sample in the field of view to determine an offset from a center of the field of view to the center of rotation of the polar coordinate stage, wherein the first information is used to determine a location of a site on a sample being inspected.
In an inspection system having a processor system and a polar coordinate stage which includes a chuck for supporting a sample, a method for determining an offset between a center of rotation of a polar coordinate stage and a center of a field of view of an imaging system, the method comprising:
- moving the chuck to a first position which is a first distance from a home position, such that a first site is positioned in the field of view;
- rotating the chuck 180 degrees and moving the chuck twice the first distance, such that the chuck is in a second position;
- adjusting the position of the chuck such that the chuck is in a third position where the first site is positioned in the field of view;
- using a ΔΘ degrees of rotation associated with adjusting the position of the chuck from the second position to the third position, and a distance ΔR associated with adjusting the position of the chuck from the second position to the third position, to determine the offset between the center of rotation of the polar coordinate stage when it is in the home position and the center of the field of view, and;
- using the offset to control the movement of the chuck to position a particular location on a wafer in the field of view.
In an inspection system having an imaging system with a field of view, and a stage which includes a chuck for supporting a sample, a method for determining an offset between a center of rotation of the stage and a center of the field of view, the method comprising:
- positioning the chuck in a first position based on a first site being positioned in the field of view;
- positioning the chuck in a second position such that the fist site is positioned in the field of view;
- determining the difference between the first position and the second position;
- and
- using the difference between the first position and the second position to calculate the offset between the center of rotation of the stage and the center of the field of view.
An inspection system for inspecting samples, comprising:
- a stage having a chuck coupled to a track, such that the chuck can be moved to different positions along the track, and rotated about a center of rotation
- an optical imaging system having a field of view;
- and
- a processor system which controls the position of the chuck relative to the track, and uses first information corresponding to an offset between a center in the field of view and the center of rotation to determine a location of a site on a wafer being inspected.
In an inspection system having a stage with a center of rotation, and an imaging system with a field of view, a method for determining a location of a site on a wafer being inspected, the method comprising:
- establishing a stage home position;
- using a processor to control the position of the stage;
- and
- using an offset between the center of rotation and a center of the field of view to determine the location of a site being inspected by the inspection system relative to the stage home position.
In an inspection system having a processor system and a stage which includes a chuck for supporting sample, a method for determining an offset between a center of rotation of a the stage and an imaging system having a center of a field of view the method comprising:
- moving a chuck of the stage to a first position which is a first distance from a home position, such that a first site on a sample is positioned in a field of view;
- moving the chuck to a second position where the first site is positioned in the field of view;
- and
- using the difference between the second position and a third position where the chuck is rotated 180 degrees from the first position and moved twice the first distance from the first position, to determine the offset.
Dependencies are inferred from the claim text.