Self-Aligned Via Awareness in Optical Proximity Correction
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Solution Overview
Problem
The complexity of semiconductor device manufacturing, particularly in self-aligned via (SAV) processes, leads to yield and reliability concerns due to sloped via sidewalls and the need for additional design space, as existing optical proximity correction (OPC) methods fail to effectively avoid encroachment on lower metal layers without incurring an intolerable real estate penalty.
Innovation Solution
A model-based approach is introduced to the OPC methodology, which identifies non-SAV edges and lower metal structures within a critical distance, using a distance constraint to redefine the mask solution and relocate non-SAV edges away from the lower metal, thereby avoiding encroachment and improving edge placement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional OPC methods are used in SAV processes, then via patterning can be achieved, but encroachment on lower metal layers occurs and additional design space is required
Solution Approach 1:
The patent applies preliminary action by incorporating self-aligned via awareness into the OPC methodology before mask fabrication. The system identifies non-SAV edges and lower metal structures within critical distances, and proactively redefines the mask solution to relocate non-SAV edges away from lower metal structures, preventing encroachment issues before they occur during manufacturing.
Solution Approach 2:
The patent changes parameters by introducing a distance constraint as an additional parameter in the OPC objective function. This constraint evaluates the distance between non-SAV edges and lower metal structures, and modifies the mask solution parameters to satisfy the minimum distance requirement, thereby improving via placement accuracy and preventing encroachment on lower metal layers.
2Reliability
If via sidewalls are spaced away from upper metal layer edges, then slope issues are avoided, but design space increases
Solution Approach 1:
The patent applies local quality by differentiating between SAV edges and non-SAV edges in the via pattern. The OPC methodology applies different constraints locally: SAV edges are allowed to be close to upper metal layer edges for compact design, while non-SAV edges are constrained to maintain minimum distance from lower metal structures. This localized differentiation achieves reliable via sidewalls without uniformly increasing design space.
3Area of stationary object
If non-SAV edges are located close to lower metal layers, then design space is minimized, but encroachment and electrical short risks increase
Solution Approach 1:
The patent implements feedback by evaluating the distance between non-SAV edges and lower metal structures as part of the OPC objective function. The system continuously monitors this distance constraint during the OPC iteration process and provides feedback to adjust the mask solution, ensuring that non-SAV edges are relocated away from lower metal structures when encroachment risks are detected, thereby preventing electrical shorts while minimizing design space.
Data Source
AI summary
A method of providing self-aligned via (SAV) awareness in optical proximity correction (OPC) includes identifying non-SAV edges, identifying any lower metal structure that is within a critical distance from the non-SAV edges, and defining replacement non-SAV edges proximate to the lower metal structure using a distance constraint that is evaluated as part of the OPC objective function to redefine the mask solution and relocate at least one non-SAV edge away from the lower metal structure.