Local Electric Field Estimation for Lithography Overlay Accuracy
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Solution Overview
Problem
Current lithographic projection systems face challenges in accurately transferring patterns to substrates due to the inability of existing models to account for local electric fields, leading to inaccuracies in etch profiles and overlay measurements, which affect the precision of device manufacturing, especially at the nanoscale.
Innovation Solution
A method and apparatus that estimate local electric fields in the mask stack region of interest and adjust target features based on these estimates to enhance metrology target designs and mask layout designs, using hardware computer systems to iteratively refine the designs and reduce the difference between pre- and post-etch overlay measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing models are used for pattern transfer, then the patterning process can be performed, but the models cannot account for local electric fields leading to inaccuracies in etch profiles and overlay measurements
Solution Approach 1:
The patent changes the parameters of the patterning model by incorporating local electric field estimates into the etch profile modeling. This allows the model to account for electric field effects that were previously neglected, thereby improving both overlay measurement accuracy and model reliability without requiring a complete model redesign
Solution Approach 2:
The patent introduces an intermediary component - the local electric field estimation - that bridges the gap between the existing patterning model and the actual physical processes. By estimating local electric fields and using them to adjust etch profiles, the model can indirectly account for complex electromagnetic interactions without directly simulating them
2Manufacturing precision
If local electric fields are estimated and target features are adjusted, then etch profile accuracy and overlay precision improve, but the device complexity increases due to additional computational steps
Solution Approach 1:
The patent applies partial action by estimating local electric fields only in specific regions of interest rather than computing fields across the entire substrate. This selective approach improves etch profile accuracy where it matters most while avoiding the computational complexity of a full-field analysis
Solution Approach 2:
The patent performs preliminary estimation of local electric fields before the actual patterning simulation. By pre-computing the electric field distribution and using it to adjust etch profiles in advance, the method simplifies the overall computational process compared to performing full electromagnetic simulations during the patterning analysis
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 leads to more accurate modeling and determination of etch profiles, improving overlay precision and reducing the overlay penalty, thereby enhancing the accuracy of wafer feature design and placement, and facilitating more precise device manufacturing.
Implementation Method 1
obtaining, with a hardware computer system, a mask stack region of interest. The mask stack region of interest has one or more characteristics associated with propagation of electromagnetic waves through the mask stack region of interest
Implementation Method 2
estimating, with the hardware computer system, a local electric field based on the one or more characteristics associated with the propagation of electromagnetic waves through the mask stack region of interest. The local electric field is estimated for a portion of the mask stack region of interest in proximity to the target feature
Data Source
AI summary
A method for determining a target feature in a model of a patterning process based on local electric fields estimated for the patterning process. The method includes obtaining a mask stack region of interest. The mask stack region of interest has one or more characteristics associated with propagation of electromagnetic waves through the mask stack region of interest. The mask stack region of interest includes the target feature. The method includes estimating a local electric field based on the one or more characteristics associated with the propagation of electromagnetic waves through the mask stack region of interest. The local electric field is estimated for a portion of the mask stack region of interest in proximity to the target feature. The method includes determining the target feature based on the estimated local electric field.