Overlay Mark Asymmetric Portion Detection and Exclusion
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Solution Overview
Problem
Existing methods for measuring overlays in semiconductor manufacturing are prone to errors due to asymmetric portions in overlay marks, which can cause misalignment and incorrect correction of layers.
Innovation Solution
A method is developed to detect and exclude asymmetric portions by forming virtual overlay marks with varying sizes and positions, comparing their information with actual overlay marks, and using this information to accurately measure the overlay while accounting for the asymmetric parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If overlay marks with asymmetric portions are used in semiconductor manufacturing, then the layers can be formed and aligned, but measurement errors occur and layer correction becomes inaccurate
Solution Approach 1:
The patent extracts and removes the asymmetric portion from the overlay mark model. By identifying the asymmetric portion through comparison with a symmetric reference model and excluding it from measurements, the system eliminates the source of measurement error while preserving the functional alignment capabilities of the overlay mark.
Solution Approach 2:
The patent intentionally introduces asymmetric portions into virtual overlay marks with varying degrees and positions of asymmetry. This allows the system to train recognition algorithms to identify and compensate for asymmetric portions in actual overlay marks, transforming the harmful asymmetric feature into a detectable and correctable characteristic.
2Adaptability or versatility
If asymmetric portions are present in overlay marks, then the marks can be formed with practical manufacturing variations, but the center point shifts causing measurement errors
Solution Approach 1:
The patent implements a feedback mechanism where the measured overlay information is compared with expected values, and the difference (error) is used to correct subsequent measurements. The system continuously refines its understanding of asymmetric portion locations and their effects, using this feedback to improve measurement accuracy over time.
Solution Approach 2:
The patent changes the parameters of virtual overlay marks by varying the size, position, and degree of asymmetric portions. This creates a comprehensive training set that allows the system to adapt to different manufacturing variations and accurately identify asymmetric portions across the full range of expected practical variations.
3Measurement precision
If virtual overlay marks with multiple asymmetric portions are created for detection, then asymmetric portion identification improves, but the process complexity increases
Solution Approach 1:
The patent segments the overlay mark into symmetric and asymmetric portions. By separating these components conceptually and measuring only the symmetric portion, the system achieves accurate overlay measurement while simplifying the analysis process. The asymmetric portion is identified and excluded rather than processed in detail.
Solution Approach 2:
The patent creates virtual copies of overlay marks with controlled asymmetric portions based on a reference symmetric model. These virtual copies serve as training data and comparison references, allowing the system to learn asymmetric portion patterns without requiring complex physical fabrication and measurement of each variant.
Data Source
AI summary
A method of detecting an asymmetric portion of an overlay mark includes forming a plurality of virtual overlay marks having a plurality of virtual asymmetric portions. The virtual asymmetric portions may have different sizes with respect to a reference model profile of a reference overlay mark. Virtual information with respect to each virtual overlay mark may be obtained. The virtual information of the virtual overlay marks may be compared with actual information of an actual overlay mark to identify virtual information of the virtual overlay mark corresponding to the actual information of the actual overlay mark. Thus, measuring the overlay of the actual overlay mark may be performed under than the actual asymmetric portion may be excluded from the actual overlay mark, so that the overlay may be accurately measured. As a result, errors may not be generated in a correcting process to a layer using the accurate overlay.