Asymmetrical Assist Features for Lithographic Pattern Accuracy
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Solution Overview
Problem
Current lithographic processes face challenges in accurately projecting design layouts onto substrates due to proximity effects and pattern deformation, which are not fully compensated by existing resolution enhancement techniques, leading to issues like pattern displacement error, contrast loss, and reduced process windows.
Innovation Solution
The implementation of a computer-implemented method that uses rules to determine and adjust the characteristics of assist features based on design features, patterning process characteristics, and lithographic apparatus characteristics, including spacing between edges, to create asymmetrical assist features that optimize the patterning process and reduce errors such as pattern displacement error and contrast loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If symmetrical assist features are used, then manufacturing simplicity is maintained, but pattern displacement error and contrast loss increase
Solution Approach 1:
The patent applies asymmetry by configuring assist features with different dimensions, shapes, or positions on opposite sides of a design feature. Specifically, the assist features are made asymmetrical with respect to the design feature, where at least one assist feature has a different configuration than its counterpart, thereby reducing pattern displacement error and contrast loss while maintaining manufacturing feasibility through rule-based determination.
Solution Approach 2:
The patent implements local quality by determining assist feature characteristics based on local spacing parameters. The method calculates spacing between adjacent design features and uses this local information to configure assist features differently in different regions. This allows the assist features to be optimized for specific local conditions (such as tight spacing versus loose spacing) rather than applying a uniform configuration everywhere.
2Manufacturing precision
If existing resolution enhancement techniques are used, then some pattern distortion is corrected, but pattern displacement error and contrast loss remain
Solution Approach 1:
The patent implements feedback by using a rule-based system that determines assist feature characteristics based on measured spacing parameters between design features. The method calculates the spacing, compares it against predefined rules or thresholds, and automatically adjusts the assist feature configuration accordingly. This feedback mechanism ensures that the assist features are optimally configured to compensate for proximity effects and other patterning errors, thereby improving pattern projection accuracy and enlarging the process window.
3Manufacturing precision
If asymmetrical assist features are implemented, then pattern displacement error and contrast loss are reduced, but design and manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying assist feature parameters (such as width, length, position, or shape) based on the spacing between adjacent design features. The method defines specific parameter ranges and selection rules that determine which assist feature configuration to use in different spacing conditions. This parameter-based approach allows asymmetrical assist features to be implemented in a controlled and systematic manner, making them easier to manufacture while maintaining their error-reduction benefits.
Data Source
AI summary
Several methods of reducing one or more pattern displacement errors, contrast loss, best focus shift, tilt of a Bossung curve of a portion of a design layout used in a patterning process for imaging that portion onto a substrate using a lithographic apparatus. The methods include determining or adjusting one or more characteristics of one or more assist features using the one or more rules based on one or more parameters selected from a group consisting of: one or more characteristics of one or more design features in the portion, one or more characteristics of the patterning process, one or more characteristics of the lithographic apparatus, and/or a combination selected from the foregoing.