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US 5,355,306 AGranted
Alignment system and method of alignment by symmetrical and asymmetrical analysis
AssigneeMotorola, Inc.
InventorWhitson G. Waldo, III
Life of this patent
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Abstract
An alignment signal is analyzed asymmetrically using any means of artificial intelligence or similar logic to apply empirical or theoretical offsets to signal position calculations based on the unique signal shapes of the different signals collected. A database of signal shapes and correlated offsets is used to improve subsequent alignment steps. For example, a case-based reasoning method can be used.
Claims11
A method of alignment, comprising the steps of:
- providing a lithographic tool;
- illuminating a target with a light generated from the lithographic tool;
- collecting an amount of light diffracted off the target to obtain a signal having positional information about the target;
- processing the signal to obtain a symmetrical analysis of the signal;
- processing the signal to obtain an asymmetrical analysis of the signal;
- calculating a correction based on a combination of the symmetrical analysis and the asymmetrical analysis;
- and
- actuating the lithographic tool according to the correction.
5 more elements
A method of alignment, comprising the steps of:
- providing a lithographic tool;
- illuminating a target with a light generated from the lithographic tool;
- collecting an amount of light diffracted off the target to obtain a signal having positional information about the target;
- symmetrically processing the signal;
- asymmetrically processing the signal by using a case-based method;
- calculating a correction based on a combination of the symmetrical processing and the asymmetrical processing;
- and
- actuating the lithographic tool according to the correction.
5 more elements
An alignment system, comprising:
- a lithographic tool;
- a means for processing a signal to obtain a symmetrical analysis of the signal coupled to the lithographic tool;
- a means for processing the signal to obtain an asymmetrical analysis of the signal coupled to the lithographic tool;
- a means for calculating a total correction based on a combination of the symmetrical analysis and the asymmetrical analysis coupled to the lithographic tool;
- and
- a means for actuating the lithographic tool according to the total correction.
3 more elements
Dependencies are inferred from the claim text.