Lithography Simulation Modulating Mask Transmission for Accuracy
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Solution Overview
Problem
Current lithography simulation methods face challenges in achieving high accuracy due to the complexity of simulating the mask topography effect, which requires a large number of calculations, making it difficult to use a simple method for high-accuracy simulations.
Innovation Solution
A lithography simulation method that modulates the mask transmission function using a mask transmission function modulation function, such as 'exslope', to reflect the mask topography effect, allowing for high-accuracy simulations without increasing the computational burden, by applying this modulation to determine a modulated mask transmission function and subsequently obtaining an optical image and resist image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strict calculation considering mask topography effect is performed, then simulation accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent segments the mask transmission function into multiple components (e.g., amplitude transmission function and phase transmission function) and processes each segment separately. This allows the complex topography effect calculation to be divided into manageable parts, reducing computational complexity while maintaining accuracy.
Solution Approach 2:
The patent performs preliminary calculations of mask topography effects before the main lithography simulation. By pre-computing the modulated mask transmission function that incorporates topography effects, the method avoids repeated complex calculations during the simulation process, thereby reducing overall computational burden.
2Measurement precision
If mask topography effect is considered, then simulation accuracy is improved, but calculation time increases
Solution Approach 1:
The patent performs preliminary action by pre-calculating the modulated mask transmission function that incorporates mask topography effects before the main lithography simulation. This pre-computation approach allows the topography effects to be accounted for without requiring repeated complex calculations during the simulation, thereby reducing calculation time while maintaining accuracy.
Solution Approach 2:
The patent creates a simplified model (modulated mask transmission function) that copies the essential characteristics of the complex mask topography effect. This copied model can be used in place of the full complex calculation, significantly reducing computation time while preserving the critical topography effects on simulation accuracy.
3Device complexity
If thin mask approximation model is used, then computational complexity is reduced, but simulation accuracy deteriorates
Solution Approach 1:
The patent changes the parameters of the mask transmission function by introducing modulation factors that account for mask topography effects. Instead of using the simple thin mask approximation, the method modifies the transmission function parameters to incorporate thickness and topography information, thereby improving accuracy without requiring full complex electromagnetic calculations.
Solution Approach 2:
The patent introduces an intermediary element (modulated mask transmission function) that bridges the gap between the simple thin mask approximation and the complex strict calculation. This intermediary function incorporates topography effects in a simplified manner, providing improved accuracy over the basic approximation while avoiding the computational burden of strict electromagnetic field calculations.
Data Source
AI summary
A lithography simulation method of obtaining a resist image by a simulation using a first function and a second function, the lithography simulation method comprising: determining a mask transmission function from a mask layout, modulating the mask transmission function using the first function to determine a modulated mask transmission function, obtaining an optical image of the mask layout using the modulated mask transmission function, and applying the second function to the optical image to obtain the resist image of the mask layout.