Lithography Alignment Correction via Surface Slope Measurement
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Solution Overview
Problem
The non-planar topography of semiconductor wafers, resulting from processes like film deposition and chemical mechanical polishing, negatively affects alignment accuracy in lithography processes, leading to increased residual overlay errors.
Innovation Solution
The exposure apparatus measures surface slopes on the wafer using a leveling measurement system and corrects alignment measurements with calculated proportional constants, enabling precise alignment and reduced residual overlay errors by adjusting the position of the wafer relative to the photo mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alignment measurement is performed without considering surface topology, then the alignment process is simple and fast, but residual overlay errors increase due to non-planar wafer surfaces
Solution Approach 1:
The patent measures the surface slope of the wafer before performing alignment measurement. By obtaining surface topology information in advance, the system can predict and correct alignment errors caused by non-planar surfaces, thereby improving alignment accuracy without adding complex real-time correction mechanisms during the exposure process
Solution Approach 2:
The patent implements a feedback mechanism where surface slope measurements are used to calculate proportional constants that correct alignment measurement results. The corrected alignment data is then used for pattern exposure, creating a closed-loop system that continuously improves alignment precision by compensating for surface topology effects
2Manufacturing precision
If surface slope measurement and alignment correction are implemented, then residual overlay errors are reduced by 10% to 50%, but the processing time and system complexity increase
Solution Approach 1:
The patent changes the measurement parameters by incorporating surface slope data into the alignment measurement process. By using proportional constants derived from surface topology, the system achieves 10% to 50% reduction in residual overlay errors while maintaining efficient processing through mathematical correction rather than physical repositioning
Data Source
AI summary
In a method for fabricating a resist pattern, a substrate coated with a photo resist is loaded on a stage of an exposure apparatus. Underlying patterns are fabricated on the substrate. A surface slope of an exposure area on the substrate is measured. An alignment measurement is performed by detecting an alignment pattern formed in the underlying patterns. An alignment measurement result is corrected based on the measured surface slope. The substrate is aligned to a photo mask by using the corrected alignment measurement result. The photo resist is exposed to radiation passing through the photo mask to form patterns.