Circular OPC Target for Contact Hole Patterning
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Solution Overview
Problem
Conventional optical proximity correction (OPC) techniques for contact hole structures in integrated circuits face limitations in image fidelity and process window as technology nodes shrink, leading to issues like side lobe printing, missing contact holes, and pattern fidelity, especially due to the use of square OPC targets which result in corner rounding and low pass filter effects.
Innovation Solution
A method involving the generation of a substantially circular optical proximity correction target, which is segmented and biased to improve image fidelity and process window, using design data to create a mask system that retains circular features throughout the OPC process, enhancing edge transitions and reducing light diffraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional square OPC targets are used for contact hole patterning, then the OPC process can be implemented with standard methodologies, but image fidelity deteriorates and process window decreases due to corner rounding and low pass filter effects
Solution Approach 1:
The patent applies spheroidality by replacing the conventional square OPC target with a substantially circular OPC target for contact hole patterning. This curvature-based approach eliminates corner rounding issues inherent in square targets and reduces low pass filter effects, thereby improving image fidelity and process window while maintaining manufacturability through standard OPC processes.
2Productivity
If technology node size decreases for high-performance integrated circuits, then circuit performance improves, but optical proximity effects such as light diffraction and interference increasingly impact contact hole uniformity
Solution Approach 1:
The patent applies preliminary anti-action by using a circular OPC target shape that preemptively counteracts optical proximity effects before patterning. The circular geometry inherently resists light diffraction and interference patterns that plague square targets at small dimensions, proactively maintaining contact hole uniformity as technology nodes scale down to improve circuit performance.
3Shape
If square OPC targets with serifs and dimensional biasing are used, then corner rounding can be induced to print circular holes, but side lobe printing and missing contact holes occur reducing process window
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of modifying a square target to print a circular hole, it uses a circular target to directly print a circular hole. This fundamental reversal eliminates the need for serifs and dimensional biasing, thereby preventing side lobe printing and missing contact holes while maintaining pattern fidelity and contact hole circularity.
Data Source
AI summary
A method of manufacture of a mask system includes: providing design data; generating a substantially circular optical proximity correction target from the design data; biasing a segment of the substantially circular optical proximity correction target; and generating mask data based on the shape produced by biasing the segment of the substantially circular optical proximity correction target.