Illumination Light Source Shape Optimization for Lithography
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Solution Overview
Problem
Conventional methods for optimizing illumination light sources in projection exposure apparatuses face challenges in achieving high resolution and accurate pattern transfer due to deviations in light source intensity distribution, leading to suboptimal image-forming performance and optical proximity effect errors, especially with complex illumination patterns.
Innovation Solution
A method that optimizes the shape of the illumination light source by setting it to match a target shape obtained through calculation, evaluating image-forming performance, and iteratively adjusting the light source shape based on detection results to ensure deviation within acceptable ranges, using spatial light modulators and polynomial modulation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light source intensity distribution is set to achieve high resolution through conventional methods, then the resolution may be improved, but deviations occur leading to suboptimal image-forming performance and optical proximity effect errors
Solution Approach 1:
The patent implements an iterative optimization process where the light source shape is adjusted based on detected deviations from target pattern dimensions. The system measures actual pattern dimensions, compares them to target values, and modifies the light source intensity distribution accordingly to minimize optical proximity effects and achieve both high resolution and accurate image formation
Solution Approach 2:
The patent systematically varies parameters of the light source intensity distribution (such as angular coordinates, radial coordinates, and intensity values at different regions) to optimize both resolution and pattern fidelity. By changing these parameters iteratively based on feedback, the system achieves optimal balance between resolution and manufacturing precision
2Manufacturing precision
If a complex illumination pattern is used to improve pattern transfer accuracy, then image-forming performance may be improved, but the system complexity and difficulty of optimization increase
Solution Approach 1:
The patent divides the light source intensity distribution into multiple discrete regions or zones (such as annular regions or angular sectors), allowing independent optimization of each segment. This segmentation simplifies the control of complex illumination patterns by breaking them down into manageable components that can be adjusted individually to achieve accurate pattern transfer
Solution Approach 2:
The patent employs dynamic adjustment of light source parameters during the optimization process, allowing the illumination pattern to adapt and evolve based on detected performance metrics. The system dynamically modifies intensity distribution parameters to achieve optimal pattern transfer accuracy without requiring permanently fixed complex configurations
Data Source
AI summary
Disclosed is a light source optimizing method wherein: a light source shape obtained as the result of SMO is set as a target, the SMO being an optimizing calculation method for optimizing a mask pattern and illumination light source, a spatial light modulator is controlled such that a deviation from the target is within an acceptable range, and the shape of the illumination light source is set; the image of the pattern obtained as the results of the SMO is formed on a wafer, using illumination light emitted from the illumination light source having the set light source shape, an OPE is evaluated as image-forming performance using the detection results obtained by detecting the image of the pattern thus formed; and the light source shape is optimized.