Lithography Focus Exposure Window Optimization
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Solution Overview
Problem
Current lithography processes, especially at shorter wavelengths and smaller geometries, are sensitive to manufacturing variations, leading to sub-optimal configurations due to ignored stochastic defect mechanisms, resulting in reduced yield and increased defect probabilities.
Innovation Solution
A method to determine a defect-based focus exposure window and a critical dimension-based focus exposure window, with a processor modifying the lithography configuration to increase the overlap between these two windows, using predictive models for defect probabilities and CD variations to optimize source and mask settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lithography operates at shorter wavelengths and smaller geometries to improve resolution, then manufacturing precision is improved, but stochastic defect mechanisms increase and reliability deteriorates
Solution Approach 1:
The patent changes the parameters of the focus exposure window by determining separate defect-based and CD-based FEWs using different predictive models. By adjusting and optimizing these parameter sets independently, the system resolves the contradiction between achieving high resolution at short wavelengths and maintaining low defect probabilities, enabling operation in a regime that satisfies both requirements simultaneously.
Solution Approach 2:
The patent segments the traditional unified focus exposure window into two distinct windows: a defect-based FEW derived from defect probability distributions and a CD-based FEW derived from critical dimension variations. This segmentation allows independent optimization of each window's parameters, enabling the system to address resolution and reliability as separate but coordinated objectives rather than conflicting constraints.
2Device complexity
If current lithography optimization approaches are used that ignore stochastic defect mechanisms, then device complexity is reduced, but manufacturing precision deteriorates
Solution Approach 1:
The patent performs preliminary action by determining the defect-based focus exposure window in advance using predictive models of defect probability distributions. This pre-calculation of the defect-based FEW allows the system to identify and avoid parameter combinations that would lead to high defect probabilities, thereby improving manufacturing precision and yield before actual production occurs, rather than reacting to defects after they happen.
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 operational tolerance and yield of lithography equipment by considering both defect probabilities and CD variations, resulting in a larger usable process window and reduced defect occurrence.
Implementation Method 1
a source produces light that is collected and directed by collection/illumination optics to illuminate a mask
Data Source
AI summary
Certain aspects relate to a method for improving a lithography configuration. In the lithography configuration, a source illuminates a mask to expose resist on a wafer. A processor determines a defect-based focus exposure window (FEW). The defect-based FEW is an area of depth of focus and exposure latitude for the lithography configuration with an acceptable level of defects on the wafer. The defect-based FEW is determined based on a predicted probability distribution for occurrence of defects on the wafer. A processor also determines a critical dimension (CD)-based FEW. The CD-based FEW is an area of depth of focus and exposure latitude for the lithography configuration with an acceptable level of CD variation on the wafer. It is determined based on predicted CDs on the wafer. The lithography configuration is modified based on increasing an area of overlap between the defect-based FEW and the CD-based FEW.