OPC Approximation Layer for IC Design Convergence
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Solution Overview
Problem
Current optical proximity correction (OPC) procedures face limitations in degrees of freedom, leading to poor convergence and difficulties in achieving optimal solutions for complex integrated chip (IC) designs, particularly due to the perpendicular movement of edges which can result in unwanted negative polygons and off-target litho contours.
Innovation Solution
The method involves generating an approximation design layer from the original IC design layer, modifying it to remove features that cause OPC problems, and performing OPC on this layer, allowing for greater degrees of freedom by replacing angled edges with vertical and horizontal edges, and selectively moving distinct edges to mitigate optical proximity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If OPC procedure is performed on original design layer with perpendicular edge movement, then optical proximity effects are corrected, but convergence is poor and unwanted negative polygons are formed
Solution Approach 1:
The patent applies preliminary action by performing approximation before the main OPC procedure. The original design layer is first approximated to create an intermediate layer with simplified geometry (removing angled edges, merging collinear edges). This preliminary transformation eliminates features that cause convergence problems in subsequent OPC iterations, allowing the main correction procedure to converge reliably while still achieving the desired manufacturing precision.
2Manufacturing precision
If perpendicular edge movement is used in OPC, then optical proximity correction is achieved, but degrees of freedom are limited
Solution Approach 1:
The patent applies dimensionality change by transforming the problem from direct perpendicular edge movement in the original coordinate system to edge approximation and movement in an intermediate approximation space. By changing the dimension of the solution space (from operating directly on original polygons to operating on approximated polygons), the method gains additional degrees of freedom in how edges can be adjusted to achieve optical proximity correction.
3Measurement precision
If OPC is performed on original design layer, then design accuracy is maintained, but unwanted negative polygons and off-target litho contours occur
Solution Approach 1:
The patent applies the extraction principle by removing problematic geometric features from the design layer before performing OPC. Specifically, angled edges that cause negative polygon formation are extracted and replaced with approximated edges having angles of 0, 90, or 180 degrees. This extraction of harmful geometric features eliminates the root cause of negative polygon generation while preserving the essential design geometry for accurate lithography.
4Ease of manufacture
If traditional OPC method is used, then process is simple, but convergence and fidelity are poor
Solution Approach 1:
The patent applies segmentation by dividing the OPC process into distinct stages: (1) approximation stage where the original design layer is transformed into an approximated layer with simplified geometry, and (2) correction stage where standard OPC is performed on the approximated layer. This segmentation allows each stage to be optimized independently - the approximation stage eliminates convergence problems, while the correction stage achieves high fidelity, resulting in overall better manufacturing precision without significantly complicating the manufacturing process.
Data Source
AI summary
The present disclosure relates to a method of performing an optical proximity correction (OPC) procedure that provides for a high degree of freedom by using an approximation design layer. In some embodiments, the method is performed by forming an integrated chip (IC) design having an original design layer with one or more original design shapes. An approximation design layer, which is different from the original design layer, is generated from the original design layer. The approximation design layer is a design layer that has been adjusted to remove features that may cause optical proximity correction (OPC) problems. An optical proximity correction (OPC) procedure is then performed on the approximation design layer. By performing the OPC procedure on the approximation design layer rather than on the original design layer, characteristics of the OPC procedure can be improved.