Focus finding and alignment using a split linear mask
AssigneeCanon Kabushiki Kaisha
InventorsMatthew R. Arnison, Tuan Quang Pham
Life of this patent
Estimating the term…
Abstract
A method of determining a focus parameter for aligning a water in an exposure tool within a measurement tolerance required for the exposure tool, the exposure tool using a lens system for alignment. A test chart is provided having a sharp auto-correlation associated with the wafer. An image of the test chart is captured using a lens pupil mask having at least two phase ramps that are non-parallel. The captured image of the test charge is auto-correlated to determine the position of the test chart relative to a focal position of the lens system. The focus parameter for alignment of the wafer is determined using the determined position of the test chart, whereby the focus parameter is determined within the measurement tolerance required by the exposure tool.
Claims18
A method of determining a focus parameter for aligning a wafer in an exposure tool within a measurement tolerance required for the exposure tool, the exposure tool using a lens system for alignment, said method comprising the steps of:
- (a) providing a test chart associated with the wafer, the test chart having a sharp auto-correlation;
- (b) capturing, using a lens pupil mask, an image of the test chart, the lens pupil mask having at least two phase ramps that are non-parallel;
- (c) auto-correlating the captured image of the test chart to determine the position of the test chart relative to a focal position of the lens system;
- and
- (d) determining the focus parameter for alignment of the wafer using the determined position of the test chart, whereby the focus parameter is determined within the measurement tolerance required by the exposure tool.
A method of focusing a lens system for an exposure tool to align a wafer within a measurement tolerance required for the exposure tool, said method comprising the steps of:
- (a) providing a test chart associated with the wafer, the test chart having a sharp auto-correlation;
- (b) capturing, using a lens pupil mask, an image of the test chart, the lens pupil mask having at least two phase ramps that are non-parallel;
- (c) auto-correlating the captured image of the test chart to determine the position of the test chart relative to a focal position of the lens system;
- and
- (d) focusing the lens system to align the wafer using the determined position of the test chart, whereby the wafer is aligned within the measurement tolerance required by the exposure tool.
A non-transitory computer readable storage medium having a computer program recorded thereon, the program being executable in a computer apparatus to determine a focus parameter for aligning a wafer in an exposure tool within a measurement tolerance required for the exposure tool, the exposure tool using a lens system for alignment, the program comprising:
- a code for providing a test chart associated with the wafer, the test chart having a sharp auto-correlation;
- a code for capturing, using a lens pupil mask, an image of the provided test chart associated with the wafer, the lens pupil mask having at least two phase ramps that are non-parallel;
- a code for auto-correlating the captured image of the test chart to determine the position of the test chart relative to a focal position of the lens system;
- and
- a code for determining the focus parameter for alignment of the wafer using the determined position of the test chart, whereby the focus parameter is determined within the measurement tolerance required by the exposure tool.
An exposure tool arrangement having a lens system for alignment of a wafer in an exposure tool, said arrangement comprising:
- a test chart associated with the wafer, the test chart having a sharp auto-correlation;
- a lens pupil mask having at least two non-parallel phase ramps;
- an image sensor configured for capturing, using the lens pupil mask, an image of the test chart;
- and
- a computer configured for:
- (i) auto-correlating the captured image of the test chart to determine the position of the test chart relative to a focal position of the lens system;
- and
- (ii) determining a focus parameter of the lens system for alignment of the wafer using the determined position of the test chart, whereby the focus parameter is determined within a measurement tolerance required by the exposure tool.
A method of determining a focus parameter for aligning a wafer in an exposure tool within a measurement tolerance required for the exposure tool, the exposure tool using a lens system for alignment, said method comprising:
- providing a test chart associated with the wafer, the test chart having a sharp auto-correlation, a high spatial frequency bandwidth, and rotational diversity;
- capturing, using a lens pupil mask, an image of the test chart, the lens pupil mask having at least two phase ramps that are non-parallel;
- determining the position of the test chart relative to a focal position of the lens system;
- and
- determining the focus parameter for alignment of the wafer using the determined position of the test chart, whereby the focus parameter is determined within the measurement tolerance required by the exposure tool.
Dependencies are inferred from the claim text.