Intermediate Range Flare Simulation for Lithographic Mask Design
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Solution Overview
Problem
Current lithographic processes face challenges in accurately and efficiently simulating intermediate-range flare effects during mask verification and optical proximity correction, as existing methods either sacrifice accuracy for computational efficiency or vice versa, due to the computational intensity of modeling aerial images with partially coherent illumination and the complexity of flare effects across chip areas.
Innovation Solution
A method is introduced that determines specific regions of influence (ROI) around a point of interest to differentiate between high and low flare contributions, using smoothed mask polygon shapes within the intermediate ROI to reduce computational complexity while maintaining accuracy, and employing density mapping for regions with minimal flare influence, thereby improving the efficiency and accuracy of flare computation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MBOPC simulation methods are used to model aerial images with partially coherent illumination, then accuracy of flare effect simulation is improved, but computational time and complexity increase significantly
Solution Approach 1:
The patent divides the mask layout into multiple tiles and processes flare computation for each tile independently. This segmentation allows parallel processing and reduces the computational burden of full-chip simulation while maintaining accuracy for intermediate-range flare effects within each tile
Solution Approach 2:
The patent applies different computation strategies to different spatial regions: full coherent imaging for nearby features within the same tile, and simplified flare models for distant features in other tiles. This local differentiation optimizes computational resources by applying high-accuracy methods only where necessary
2Measurement precision
If full coherent imaging simulation is applied to all mask features, then accuracy of short-range flare computation is improved, but memory utilization and processing efficiency deteriorate
Solution Approach 1:
The patent segments the computation domain into intra-tile and inter-tile regions. Within each tile, full coherent imaging is used for accurate short-range flare computation. For inter-tile contributions, the patent uses simplified flare models that require minimal memory, thus maintaining accuracy where needed while reducing overall memory complexity
3Productivity
If simplified flare models are used across the entire chip area, then computational efficiency is improved, but accuracy of intermediate-range flare simulation deteriorates
Solution Approach 1:
The patent applies a hybrid approach where simplified flare models are used for distant inter-tile features to maintain computational efficiency, while full coherent imaging is applied to intermediate-range features within the same tile to preserve accuracy. The tile-based architecture ensures that intermediate-range effects are captured with appropriate fidelity
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
This approach reduces the number of sectors needed for mask shapes in the intermediate flare range, enhancing the efficiency of Model-Based Optical Proximity Correction (MBOPC) iterations, improving memory utilization, and maintaining high accuracy in short-range computations, while providing a more efficient and accurate simulation of flare effects across the entire chip area.
Implementation Method 1
the scattered light which affects the exposure over long distances on the wafer are recently being considered. Such long-range optical effects are generally referred to as 'flare' in the literature.
Implementation Method 2
In an Aerial Image simulator, in addition to the diffraction of light in the presence of low order aberrations, the scattered light which affects the exposure over long distances on the wafer are recently being considered.
Data Source
AI summary
A method is provided for modeling lithographic processes in the design of photomasks for the manufacture of semiconductor integrated circuits, and more particularly for simulating intermediate range flare effects. For a region of influence (ROI) from first ROI1 of about 5λ/NA to distance ROI2 when the point spread function has a slope that is slowly varying according to a predetermined criterion, then mask shapes at least within the distance range from ROI1 to ROI2 are smoothed prior to computing the SOCS convolutions. The method provides a fast method for simulating intermediate range flare effects with sufficient accuracy.