Grid Model Selection for Lithographic Overlay Correction
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Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining pattern alignment across multiple layers due to grid deformations, leading to misalignment issues during the transfer of patterns from one layer to another.
Innovation Solution
A method is developed to select a grid model for correcting process recipes by providing a set of grid models, obtaining alignment and metrology data, checking suitability, and selecting the model with the lowest residuals, which involves a computer program product executed by a processor to perform this method within a lithographic assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed grid model is used for pattern transfer, then the manufacturing process is simple and fast, but grid deformations cause misalignment between layers
Solution Approach 1:
The system dynamically selects the most appropriate grid model from multiple available models based on real-time alignment data and metrology measurements. Instead of using a fixed grid model, the system adapts the grid model choice to match the actual deformation characteristics observed during processing, thereby maintaining high alignment accuracy without requiring all possible correction mechanisms to be active simultaneously.
Solution Approach 2:
The system changes the parameters of the grid model selection process by evaluating multiple candidate models with different deformation characteristics. By comparing alignment residuals across different grid models and selecting the one with the lowest residuals, the system optimizes the grid model parameters to match the actual process conditions, resolving the contradiction between simplicity and precision.
2Manufacturing precision
If multiple grid models are evaluated and selected based on alignment data, then alignment accuracy is improved, but the processing time and computational complexity increase
Solution Approach 1:
The system performs preliminary evaluation of multiple grid models using alignment data obtained during the alignment measurement step. By assessing the suitability of different grid models before actual pattern transfer and selecting the best model in advance, the system avoids time-consuming trial-and-error adjustments during production, thus improving overlay accuracy without excessive time loss.
Solution Approach 2:
The system replaces physical trial-and-error grid adjustments with a computational model selection process. By using automated algorithms to evaluate alignment residuals and select the optimal grid model based on metrology data, the system substitutes mechanical adjustment time with efficient computational analysis, achieving high overlay accuracy while minimizing time consumption.
Data Source
AI summary
A method of selecting a grid model for correcting a process recipe for grid deformations in a lithographic apparatus is disclosed. First a set of grid models is provided. Subsequently, alignment data are obtained by performing an alignment measurement on a plurality of alignment marks on a number of substrates. For each grid model it is checked whether the alignment data is suitable to solve the grid model. If so, the grid model is added to a subset of grid models. The grid model with lowest residuals is selected. In addition to alignment data, metrology data may be obtained by performing an overlay measurement on a plurality of overlay marks on the number of substrates. For each grid model of the subset simulated metrology data may then be determined that is used to determine overlay performance indicators. The grid model is then selected using the overlay performance indicators.