Pattern Overlay Detection Using Tangential Center Calculation
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Solution Overview
Problem
Accurately detecting the central position of a lower pattern hidden by an upper pattern is challenging due to partial exposure, which complicates the alignment of patterns at multiple levels on a substrate.
Innovation Solution
A method involving the calculation of the real center of gravity using a common tangential line, drawn by a sample pattern with a common contact point, allows for accurate determination of the lower pattern's position even when hidden, enabling precise overlay detection and alignment between upper and lower patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lower pattern is partially hidden by the upper pattern, then the visibility of the lower pattern is reduced, but the need to detect the central position of the lower pattern remains
Solution Approach 1:
A sample pattern is introduced as an intermediary element that does not interfere with the actual lower pattern. The sample pattern is drawn to have a common tangential line with the lower pattern, and its center of gravity is calculated to represent the lower pattern's center. This intermediary approach allows accurate detection without directly observing the hidden lower pattern.
Solution Approach 2:
Instead of directly detecting the hidden lower pattern, a sample pattern is created that copies the essential geometric relationship (common tangential line) with the lower pattern. The center of gravity of this sample pattern serves as a proxy for the lower pattern's center, enabling accurate detection through calculation rather than direct observation.
2Manufacturing precision
If the lower pattern is hidden by the upper pattern, then the alignment detection between upper and lower patterns becomes difficult, but proper alignment is required
Solution Approach 1:
The sample pattern acts as an intermediary that preserves the position information of the hidden lower pattern. By calculating the center of gravity of the sample pattern based on the common tangential line relationship, the position information of the lower pattern is recovered without direct observation, enabling accurate alignment detection.
Solution Approach 2:
The sample pattern is drawn in advance before the overlay detection process. This preliminary action establishes the geometric relationship (common tangential line) with the lower pattern, allowing the center position to be calculated and used for alignment detection without needing to directly observe the hidden lower pattern during the detection process.
3Measurement precision
If a sample pattern is drawn with a common tangential line, then the center of gravity can be accurately calculated, but additional processing steps are required
Solution Approach 1:
The essential geometric relationship (common tangential line) is extracted and applied to the sample pattern. By focusing only on this critical relationship rather than the entire complex pattern structure, the center of gravity can be accurately calculated using a simplified approach that reduces processing complexity while maintaining precision.
Data Source
AI summary
A method of detecting overlay of patterns includes forming a lower pattern and an upper pattern on a substrate. A sample pattern is drawn that has a common tangential line with the lower pattern. A position of a real center of gravity of the lower pattern is calculated using the common tangential line.