NILS-Based Source Optimization for Fine-Pattern Lithography
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Solution Overview
Problem
Existing lithography processes face challenges in achieving optimal source system performance for fine pattern formation, particularly in cell and core/peri areas of DRAM products, with existing solutions often dependent on user proficiency and lacking in consistent patterning quality.
Innovation Solution
A method for source optimization simulation that generates an optimized source system by selecting target patterns, generating aerial images, constructing an objective function based on NILS values, and adjusting the source system to maximize this function, using a combination of effective factors for point sources, independent of user proficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional source optimization methods are used, then the process is simple to operate, but the patterning quality is insufficient for fine patterns
Solution Approach 1:
The patent changes the optimization parameter from traditional edge placement error (EPE) to normalized image log-slope (NILS). This parameter transformation enables better correlation with patterning quality while maintaining computational feasibility. The NILS parameter directly reflects the slope of the aerial image intensity profile, which is critical for determining pattern fidelity at fine dimensions.
Solution Approach 2:
The patent replaces manual trial-and-adjustment optimization with an automated computational optimization system. The system automatically adjusts source parameters (illumination angles, intensities, phases) to maximize the NILS-based objective function, eliminating dependence on user proficiency while achieving optimal patterning results.
2Reliability
If manual source optimization is performed, then the computational resources required are low, but the results depend on user proficiency
Solution Approach 1:
The patent implements a feedback-based optimization loop where the NILS values are calculated from aerial images generated with current source parameters, compared against the objective function, and used to guide adjustments to source parameters. This iterative feedback process ensures consistent convergence to optimal solutions regardless of initial conditions or user expertise.
Solution Approach 2:
The optimization system is self-adjusting, automatically modifying source parameters to maximize the NILS-based objective function without requiring manual intervention or expert knowledge. The system performs rendering, aerial image generation, NILS calculation, and parameter adjustment in an autonomous manner, ensuring reproducible results.
3Manufacturing precision
If fine patterns are formed, then the patterning performance improves, but the source system performance becomes insufficient
Solution Approach 1:
The patent transforms the source system from a static configuration to a dynamic, optimized configuration. By adjusting illumination angles, intensities, and phases based on NILS optimization, the source system adapts to the specific requirements of fine pattern formation. This dynamic optimization enables the source system to deliver enhanced performance for sub-10nm patterns while maintaining flexibility for different pattern types.
Data Source
AI summary
Disclosed is a program code and a non-transitory computer readable medium including the program code, in which the program code, when executed by a processor, causes an apparatus including the processor to perform operations of selecting a plurality of target patterns from a mask layout, generating an aerial image based on a source system including a plurality of point sources and the mask layout, constructing an objective function based on a plurality of NILS values corresponding to the plurality of target patterns in the aerial image, optimizing the source system such that the objective function has a maximum value, and outputting an optimized source system, and the optimized source system includes a combination of a plurality of effective factors corresponding to the plurality of point sources.