Lithography Calibration via Overlay Error Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithographic apparatus calibration methods disrupt productivity and are costly, as they require significant downtime and resource-intensive processes to maintain accuracy and correct for overlay errors, especially after interruptions in operation.
Innovation Solution
A method involving a calibration substrate with first and second marks, where the patterning system applies the second marks over the first marks while varying operating parameters, allowing for overlay measurements to calculate apparatus-specific calibration data, enabling continuous operation and reduced downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional calibration methods are used to correct overlay errors and maintain accuracy, then manufacturing precision is improved, but productivity deteriorates due to significant downtime and operational interruptions
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements on a dedicated calibration substrate before production runs. The calibration substrate contains pre-formed first marks that serve as reference targets, allowing the system to pre-determine apparatus-specific deviations and establish correction data before actual production begins. This eliminates the need to interrupt production for calibration activities.
Solution Approach 2:
The patent introduces a calibration substrate as an intermediary element between the lithographic apparatus and production substrates. This calibration substrate carries first marks that are used to measure overlay errors and determine apparatus-specific deviations. By using this intermediary calibration medium, the system can obtain calibration data without exposing production substrates to measurement processes that would cause downtime.
2Manufacturing precision
If detailed calibration with multiple parameter variations is performed to improve accuracy, then manufacturing precision is improved, but loss of time increases due to repeated substrate processing
Solution Approach 1:
The calibration substrate is prepared in advance with first marks formed by a reference lithographic apparatus. These pre-formed marks serve as stable reference targets that eliminate the need to repeatedly process production substrates for calibration purposes. The preliminary formation of these reference marks enables subsequent calibration measurements to be performed quickly without extensive substrate processing cycles.
Solution Approach 2:
The patent uses a copying approach where first marks are formed on the calibration substrate by a reference lithographic apparatus, creating a replica or copy of the desired pattern. These copied marks serve as reference targets for measuring overlay errors. By using these copied reference marks instead of repeatedly processing original production substrates, the system achieves accurate calibration without time-consuming repeated processing.
3Manufacturing precision
If calibration is performed after interruptions in operation to maintain reliability, then manufacturing precision is improved, but productivity deteriorates due to operational downtime
Solution Approach 1:
The system performs preliminary calibration measurements on the calibration substrate before production interruptions occur or at the resumption point. The calibration substrate with pre-formed first marks allows for quick determination of apparatus-specific deviations that may have developed during the interruption. This preliminary calibration action ensures accuracy is restored without requiring extended downtime.
Solution Approach 2:
The calibration substrate serves as an intermediary that enables rapid calibration checks after operational interruptions. By using this dedicated calibration medium with reference first marks, the system can quickly measure overlay errors and update correction data without needing to process production substrates. This intermediary approach minimizes the impact of calibration activities on production continuity.
Data Source
AI summary
A lithography tool is calibrated using a calibration substrate having a set of first marks distributed across its surface in a known pattern. The tool is operated to apply a pattern comprising a plurality of second marks at various positions on the substrate, each second mark overlying one of the first marks and being subject to an overlay error dependent on an apparatus-specific deviation. The second marks are applied by multiple exposures while the substrate remains loaded in the tool. An operating parameter of the apparatus is varied between the exposures. An overlay error is measured and used to calculate parameter-specific, apparatus-specific calibration data based on knowledge of the parameter variation used for each exposure.