Microstructure Parameter Determination via Phase Retrieval
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Solution Overview
Problem
Current scatterometer measurement techniques lack the sensitivity and accuracy to measure small variations in substrate shape parameters, particularly in lithographic processes, due to limitations in detector sensitivity and wavelength choice.
Innovation Solution
The method involves illuminating overlapping regions of a substrate with coherent radiation beams, measuring diffraction intensity patterns, retrieving phase information, and modeling the target structure to determine accurate structure parameters by comparing measured and calculated patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scatterometer measurement techniques are used, then the measurement process is simple and fast, but the measurement precision and sensitivity are insufficient for small variations in substrate shape parameters
Solution Approach 1:
The patent segments the measurement process into multiple discrete steps: illuminating different regions with coherent beams, measuring diffraction patterns separately, retrieving phase information through mathematical processing, and combining results. This segmentation enables precise measurement of small variations while maintaining manageable system complexity through modular processing steps.
Solution Approach 2:
The patent transitions from conventional intensity-only measurement to a two-dimensional measurement space by retrieving and utilizing phase information in addition to intensity. This dimensional expansion from scalar intensity to complex amplitude (intensity + phase) significantly enhances sensitivity to small shape variations without proportionally increasing hardware complexity.
2Reliability
If conventional scatterometer techniques are used, then the setup is straightforward, but the ability to detect small variations in target shape is limited
Solution Approach 1:
The patent implements feedback through iterative phase retrieval algorithms that use measured diffraction patterns to refine estimates of the target structure. By comparing measured and calculated patterns and adjusting phase information accordingly, the system achieves reliable detection of small shape variations that would be undetectable with single-pass conventional methods.
Solution Approach 2:
The patent changes the fundamental measurement parameters from conventional intensity-only detection to include phase information retrieval. By measuring and processing both intensity and phase of the coherent diffraction patterns, the system achieves enhanced reliability in detecting small shape variations that conventional techniques miss.
3Measurement precision
If phase information retrieval is implemented, then measurement accuracy improves, but the processing complexity and computational requirements increase
Solution Approach 1:
The patent performs preliminary actions by capturing multiple diffraction patterns from different illuminated regions before phase retrieval processing. This preliminary data collection from overlapping regions with coherent illumination provides the necessary information for subsequent phase retrieval, enabling accurate measurements while organizing computational work in advance.
Solution Approach 2:
The patent creates copies of the diffraction measurement process by illuminating multiple overlapping regions and capturing separate diffraction patterns. These copied measurements from different regions provide redundant information that facilitates phase retrieval through mathematical processing, improving precision without requiring exponentially more processing time.
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 measurement accuracy and sensitivity, allowing for better determination of structure parameters with reduced uncertainties, particularly in the context of microstructure analysis in lithographic processes.
Implementation Method 1
measuring a diffraction intensity pattern arising from the illumination of the first region
Implementation Method 2
measuring a diffraction intensity pattern arising from the illumination of the first region
Data Source
AI summary
A method of determining a structure parameter of a target. Illuminating a first region of the target with a first beam and measuring a diffraction pattern. Shifting the position between the target and the projection system to offset a second region to be illuminated from the first region. Illuminating the second region and measuring a diffraction pattern. Retrieving phase information from the measured first and second diffraction patterns. Modeling the target using an estimated structure parameter to calculate a modeled diffraction pattern and modeled phase information. Determining the structure parameter of the target by comparing the measured diffraction patterns and the retrieved phase to the calculated modeled diffraction intensity pattern and the modeled phase information.