Interference Mapping Lithography Assist Feature Optimization
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Solution Overview
Problem
Current photolithography techniques face challenges in optimizing the placement and sizing of assist features to maximize Depth of Focus (DOF) and Exposure Latitude (EL) due to the limitations of human inspection and lack of systematic methods for determining optimal locations and sizes of assist features, especially for microscopic features like contact holes.
Innovation Solution
The method of Interference Mapping Lithography (IML) optimizes the placement and sizing of assist features by generating an interference map, modifying it to maximize intensity for resolvable features, and selecting discrete mask transmissions to minimize sidelobe printing, thereby enhancing DOF and EL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If human inspection and rule-based placement methods are used to determine assist feature locations and sizes, then the process is simple to implement, but the Depth of Focus and Exposure Latitude cannot be maximized due to limitations in human inspection capability
Solution Approach 1:
The patent replaces human inspection and rule-based placement with an automated computational system that uses interference map generation and optimization algorithms to determine assist feature locations and sizes, thereby achieving superior DOF and EL optimization without human limitation
Solution Approach 2:
The system varies multiple parameters including assist feature size, location, and mask transmission values to optimize the interference pattern and maximize DOF and EL, moving from fixed rule-based parameters to dynamically optimized parameters
2Illumination intensity
If assist features are placed to maximize peak intensity, then Exposure Latitude improves, but sidelobe printing may occur
Solution Approach 1:
The optimization algorithm adjusts mask transmission parameters and assist feature dimensions to achieve the desired peak intensity while suppressing sidelobe formation, demonstrating parameter optimization to balance competing requirements
Solution Approach 2:
The system uses the generated interference map as feedback to iteratively optimize assist feature parameters, adjusting the placement and sizing based on the observed intensity distribution to maximize peak intensity while minimizing sidelobe printing
3Productivity
If rule-based placement methods are used for assist features, then the process is fast to execute, but chip-level optimization cannot be achieved
Solution Approach 1:
The system performs automated self-optimization across the entire chip by generating interference maps and computing optimal assist feature configurations without requiring external human intervention or iterative manual adjustments
Solution Approach 2:
The interference map is generated in advance to predict and optimize the aerial image formation, allowing assist features to be placed at optimal locations before actual lithography, thereby achieving chip-level optimization efficiently
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
IML significantly increases peak intensity and achieves optimized exposure latitude and depth of focus by strategically placing assist features, outperforming conventional methods and allowing for efficient chip-level optimization in a fraction of the time required by rule-based placement.
Implementation Method 1
areas where the intensity is greater than zero represent a location where light will interfere constructively with the desired feature/pattern, while areas where the intensity is less than zero represent a location where light will interfere destructively
Data Source
AI summary
Disclosed concepts include a method of, and program product for, optimizing an illumination profile of a pattern to be formed in a surface of a substrate relative to a given mask. Steps include mathematically representing resolvable feature(s) from the given mask, generating an interference map representation from the previous step, modifying the interference map representation to maximize intensity corresponding to the resolvable features, and determining assist feature size(s) such that intensity side lobes do not print.