Lithographic Apparatus Warp Correction via Alignment Sensor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithographic processes face challenges in correcting overlay errors and focus issues due to residual non-flatness of substrates, which are not adequately addressed by existing alignment models and metrology systems, especially in high-volume manufacturing where additional measurements are costly and impact throughput.
Innovation Solution
A lithographic apparatus that uses alignment and height sensors to measure positional deviations and substrate shape, inferring warp-induced characteristics to apply corrections to pattern positioning and focusing, thereby mitigating residual unflatness effects without requiring additional measurement overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alignment marks and metrology targets are placed at higher spatial density to increase measurement frequency, then overlay correction accuracy is improved, but throughput of the lithographic process decreases and functional device area is reduced
Solution Approach 1:
The patent extracts the measurement function from dedicated alignment marks and metrology targets, and relocates it to the existing alignment sensor that measures alignment marks during normal patterning operations. This allows overlay information to be obtained as a byproduct of existing operations, avoiding the need for additional measurement infrastructure that would reduce throughput and functional area.
Solution Approach 2:
The alignment sensor is made multi-functional by using it for both its original purpose of measuring alignment marks during patterning operations and the additional purpose of measuring overlay information. This eliminates the need for separate metrology targets and measurement operations, thereby maintaining throughput while improving overlay correction accuracy.
2Manufacturing precision
If higher order alignment models are applied to correct non-linear distortions, then overlay error is reduced, but the complexity of the alignment model increases and requires higher spatial density of position measurements
Solution Approach 1:
The patent implements a feedback mechanism where alignment information obtained during patterning operations is fed back to a metrology system. This feedback loop allows the system to measure and correct overlay errors using existing operational data, avoiding the need for complex higher-order models while still achieving accurate overlay correction through iterative measurement and adjustment.
3Manufacturing precision
If additional metrology measurements are performed to characterize substrate warp, then residual non-flatness correction is improved, but measurement cost increases and throughput is reduced
Solution Approach 1:
The patent performs preliminary characterization of substrate warp effects during normal patterning operations by measuring alignment marks before the actual patterning begins. This preliminary measurement captures the warp-induced distortions in advance, allowing corrections to be applied during patterning without requiring separate, time-consuming metrology measurements afterward.
Solution Approach 2:
The system uses its existing alignment sensing capability to serve the additional purpose of characterizing substrate warp and measuring overlay information. The alignment sensor serves itself by providing dual functionality, eliminating the need for separate metrology equipment and reducing overall measurement time and cost.
Data Source
AI summary
A lithographic process includes clamping a substrate onto a substrate support, measuring positions across the clamped substrate, and applying a pattern to the clamped substrate using the positions measured. A correction is applied to the positioning of the applied pattern in localized regions of the substrate, based on recognition of a warp-induced characteristic in the positions measured across the substrate. The correction may be generated by inferring one or more shape characteristics of the warped substrate using the measured positions and other information. Based on the one or more inferred shape characteristics, a clamping model is applied to simulate deformation of the warped substrate in response to clamping. A correction is calculated based on the simulated deformation.