Dual-Surface Overlay Marks for Misalignment and Wafer Warpage
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Solution Overview
Problem
The semiconductor industry faces challenges in accurately measuring and correcting overlay errors in lithography operations due to asymmetric shapes of measurement structures, which complicates the precise alignment of photoresist patterns and underlying patterns, leading to potential misalignment and wafer warpage issues.
Innovation Solution
The use of dual overlay marks, one on each surface of a substrate, where the first mark generates a first overlay error indicative of misalignment and the second mark generates a second error to determine if the abnormality is caused by misalignment or warpage, allowing for precise correction and preventing inaccurate adjustments to exposure equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single overlay mark is used for measurement, then the measurement process is simple, but it cannot distinguish between misalignment and wafer warpage causing inaccurate correction
Solution Approach 1:
The overlay measurement system is segmented into two independent overlay marks: a first overlay mark for initial measurement and a second overlay mark for correction. This segmentation allows the system to distinguish between misalignment errors and wafer warpage by comparing measurements from both marks, thereby improving measurement precision without requiring a single complex mark structure.
Solution Approach 2:
The second overlay mark acts as an intermediary verification tool. By introducing this intermediate measurement point, the system can determine whether the first overlay error is caused by actual misalignment or by wafer warpage, enabling more accurate correction decisions and preventing erroneous adjustments to exposure equipment.
2Productivity
If overlay errors are corrected based on single mark measurement, then correction is quick, but inaccurate correction may occur due to inability to distinguish error sources
Solution Approach 1:
The system performs preliminary verification by measuring both the first overlay mark and the second overlay mark before making correction decisions. This preliminary action of cross-validation ensures that correction is only applied when misalignment is confirmed, preventing unnecessary adjustments and ensuring reliable correction while maintaining productivity through automated decision-making.
3Adaptability or versatility
If asymmetric measurement structures are used, then they can capture complex overlay errors, but measurement precision deteriorates due to asymmetry complications
Solution Approach 1:
The patent employs overlay marks with symmetric or homogeneous structural characteristics that simplify the measurement process. By using consistent, standardized mark structures rather than asymmetric custom designs, the system achieves higher measurement precision while maintaining the ability to capture complex overlay errors through the dual-mark verification approach.
Data Source
AI summary
A mark for overlay error measurement and overlay error measurement is provided. The mark includes a first pattern and a second pattern. The first pattern is disposed on a first surface of a substrate. The second pattern is disposed on a second surface of the substrate. The second surface of the substrate is opposite to the first surface of the substrate. The first pattern overlaps at least a portion of the second pattern, and the first pattern and the second pattern collaboratively define a first overlay error.