OPC Correction Using NILS and MEEF Optimization
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Solution Overview
Problem
Conventional optical proximity correction (OPC) methods do not adequately consider the lithography process window, resulting in deficiencies in the mask layout despite achieving good conformity in pattern exposure.
Innovation Solution
The method involves establishing an OPC model and performing corrections by defining target and dissection points based on pre-target and pre-dissection points, using normalized image log slope (NILS) and mask error enhancement factor (MEEF) to optimize image quality and process window, allowing for flexible segment corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional OPC methods use fixed target points and constant correction amounts based on experience, then the ADI profile passes through the target points with good conformity, but the lithography process window is not optimized and deficiencies remain in the mask layout
Solution Approach 1:
The patent performs preliminary actions by calculating multiple pre-target points and pre-dissection points before the actual OPC correction. These preliminary points are evaluated using image quality metrics (NILS and MEEF) to determine the optimal target点和 dissection points that will maximize the lithography process window while maintaining pattern conformity.
Solution Approach 2:
The patent changes the parameters of target points and dissection points from fixed, experience-based values to optimized values determined by image quality metrics. Specifically, it adjusts the positions of target points and dissection points based on NILS (normalized image log slope) and MEEF (mask error enhancement factor) calculations, and modifies the correction amounts dynamically rather than using constant values.
2Ease of manufacture
If the distance from target point to dissection point is kept constant and segments are fixed, then the correction process is simple, but the image quality and lithography process window are not optimized
Solution Approach 1:
The patent introduces dynamics by making the distances between target points and dissection points variable rather than constant. The positions of these points are adjusted dynamically based on image quality evaluations (NILS and MEEF), allowing the correction process to adapt to different pattern features and optimize both image quality and lithography process window.
3Manufacturing precision
If only ADI profile passing through target points is concerned, then the pattern conformity is achieved, but the lithography process window and image quality stability are compromised
Solution Approach 1:
The patent implements feedback by using image quality metrics (NILS and MEEF) to evaluate the effectiveness of different target point and dissection point configurations. This feedback loop allows the system to iteratively adjust the positions of these points and the correction amounts to achieve both pattern conformity and optimized lithography process window, thereby improving image quality stability.
Data Source
AI summary
An optical proximity correction method is disclosed, comprising establishing an optical proximity correction (OPC) model, and performing an OPC correction step to correct segments of a layout pattern. The OPC correction comprises the step of defining an edge of the layout pattern neighboring a hot-spot location on a mask to locate a target point and a dissection point. The step of locating the target point and the dissection point includes setting a plurality of pre-target points and pre-dissection points, and electing a target point and a dissection point for correcting the segments of the layout pattern from the pre-target points and pre-dissection points according to image quality of the pre-target points and pre-dissection points.