Displacement-Based Overlay Measurement for Lithography Proximity Effects
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Solution Overview
Problem
Current lithography techniques face challenges in accurately reproducing small feature sizes and high feature densities due to proximity effects, which can result in design flaws and reduced process windows, especially when exposure conditions deviate from nominal conditions.
Innovation Solution
The method involves obtaining an image of structures on a substrate, determining their displacement relative to a reference point, and assigning them into groups based on these displacements using a hardware computer system, allowing for the identification of defects and alignment errors, and utilizing clustering algorithms and homogeneous transformation matrices for precise mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography techniques are used to transfer patterns onto substrates, then the patterning process can be completed, but proximity effects cause inaccurate reproduction of small feature sizes and high feature densities
Solution Approach 1:
The patent applies preliminary action by performing overlay measurements and defect identifications before final pattern transfer. The system measures displacements of structures from their intended positions and identifies potential defects in advance, allowing corrections to be made before completing the patterning process, thus preventing proximity effects from compromising final pattern accuracy
Solution Approach 2:
The patent implements feedback by using metrology processes to measure actual structure positions and comparing them with intended design positions. The measured displacement information is fed back to adjust subsequent patterning operations, compensating for proximity effects and ensuring accurate reproduction of small features and high-density patterns
2Adaptability or versatility
If exposure conditions deviate from nominal conditions, then the lithography process can proceed under varying conditions, but design flaws increase and process window reduces
Solution Approach 1:
The patent applies parameter changes by measuring and tracking variations in exposure conditions and their effects on pattern formation. The system adjusts measurement and control parameters based on actual exposure conditions, allowing the process to adapt to varying conditions while maintaining reliability through real-time monitoring and compensation
3Measurement precision
If metrology processes are used to measure substrate characteristics, then process performance can be monitored and controlled, but measurement precision is required to detect small displacements
Solution Approach 1:
The patent applies segmentation by dividing the substrate into multiple regions with reference structures distributed throughout. Each reference structure is measured independently, allowing local displacement measurements that are more precise than global measurements. This segmentation enables detection of small feature displacements by comparing each local reference structure's position with its intended position
Data Source
AI summary
A method including obtaining an image of a plurality of structures on a substrate, wherein each of the plurality of structures is formed onto the substrate by transferring a corresponding pattern of a design layout; obtaining, from the image, a displacement for each of the structures with respect to a reference point for that structure; and assigning each of the structures into one of a plurality of groups based on the displacement.