Photomask Measurement Simulation Parameter Optimization
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Solution Overview
Problem
Existing methods for measuring photomasks in semiconductor lithography face challenges in accurately assessing mask quality due to variations in production processes, leading to deviations in critical dimensions and corner rounding, which are not accurately reflected by current simulation parameters, resulting in simulation errors.
Innovation Solution
A method that optimizes simulation parameters by comparing recorded images with simulated images, adjusting parameters based on threshold values and using a merit function to improve simulation quality, and employing preliminary measurements to select suitable parameter sets for specific mask structures, allowing for precise registration measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard simulation parameters are used for measuring photomasks, then the measurement process is simple and fast, but the simulation accuracy deteriorates due to production process variations and mask deviations
Solution Approach 1:
The patent applies preliminary action by performing preliminary measurements on the photomask before the actual measurement process. These preliminary measurements capture mask-specific properties such as corner rounding and critical dimension variations, which are then used to optimize simulation parameters in advance. This ensures that the simulation accurately reflects the actual mask characteristics without adding complexity to the main measurement process.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting simulation parameters based on preliminary measurement results. Instead of using fixed standard parameters, the system modifies parameters such as critical dimensions and corner rounding values to match the specific mask being measured. This approach maintains measurement precision while managing complexity through automated parameter adaptation.
2Measurement precision
If simulation parameters are optimized for each specific mask structure, then measurement accuracy improves, but the measurement time and processing complexity increase
Solution Approach 1:
The system performs preliminary measurements and simulations in advance to determine optimal parameters for each mask structure. These optimized parameters are stored and reused for subsequent measurements of similar structures, eliminating the need to repeat the optimization process and significantly reducing measurement time while maintaining high accuracy.
Solution Approach 2:
The patent uses copying by creating a digital model of the mask based on preliminary measurements and design data. This digital model includes optimized simulation parameters that are copied and applied to multiple measurement scenarios, reducing the need for repeated optimization and accelerating the measurement process.
3Ease of manufacture
If ideal mask design is assumed in simulation, then the simulation model is simple, but it fails to account for real mask deviations from production processes
Solution Approach 1:
The patent applies local quality by incorporating specific deviation characteristics at different locations on the mask. Instead of using a uniform ideal mask model, the system adjusts simulation parameters locally based on preliminary measurements of corner rounding, critical dimensions, and other structure-specific variations. This maintains reasonable model simplicity while significantly improving reliability.
Solution Approach 2:
The system modifies simulation parameters to reflect actual mask properties rather than ideal design specifications. By changing parameters such as critical dimensions and corner rounding values based on preliminary measurements, the simulation model becomes more representative of real masks while retaining its computational efficiency.
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 enhances the accuracy of photomask measurements by reducing simulation errors and ensuring high-quality reference images, enabling efficient and precise registration measurements while accounting for structure-specific and manufacturing process-dependent deviations.
Implementation Method 1
recording images of individual measurement regions on the photomask by means of an image capturing unit
Implementation Method 2
recording images of individual measurement regions on the photomask by means of an image capturing unit
Data Source
AI summary
A method for measuring photomasks for semiconductor lithography, includes the following steps:loading a photomask into a recording unit of a measuring apparatus,recording images of individual measurement regions on the photomask by means of an image capturing unit,comparing at least one recorded image of a measurement region with a simulated image of this measurement region using specific simulation parameters. In the process, the comparison of at least one of the recorded images with the corresponding simulated image is used to carry out an adjustment of at least one portion of the simulation parameters.