Overlay Measurement Using SEM Image Synthesis
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Solution Overview
Problem
Current overlay measurement methods in semiconductor manufacturing face challenges in achieving accurate and robust measurements without relying on CAD data, especially when circuit patterns are defective or have positional deviations, making it difficult to measure overlay directly in actual patterns formed on semiconductor devices.
Innovation Solution
A method and apparatus that captures images of semiconductor devices using a scanning electron microscope, sets a reference image, quantifies differences between captured images, and calculates overlay without requiring CAD data or inputting reference values, allowing for robust overlay measurement by recognizing circuit pattern areas and quantifying positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If overlay measurement is performed using captured images of actual patterns without CAD data, then measurement simplicity and robustness are improved, but measurement precision deteriorates due to pattern shape differences between wafer and CAD data
Solution Approach 1:
The patent creates a reference image by synthesizing it from multiple captured images of actual patterns. This reference image serves as a copy of the actual pattern configuration, eliminating the need for CAD data while maintaining measurement accuracy through direct replication of the measured object's structure
Solution Approach 2:
The patent performs preliminary synthesis of a reference image from multiple captured images before conducting overlay measurement. This preliminary action creates a robust reference that accounts for pattern variations and defects, enabling accurate measurement without requiring perfect CAD data matching
2Measurement precision
If overlay measurement is performed by comparing contour information with CAD data, then measurement accuracy is improved, but device complexity increases due to CAD data handling requirements
Solution Approach 1:
The system performs self-service by automatically synthesizing the reference image from captured images of actual patterns. This eliminates the need for external CAD data input and processing, simplifying the system while maintaining measurement capability through self-generated reference data
Solution Approach 2:
The patent extracts the reference pattern information directly from captured images of actual patterns, removing the dependency on CAD data. This extraction approach simplifies the system by eliminating CAD data handling components while obtaining necessary reference information from the measured object itself
3Adaptability or versatility
If overlay measurement is performed using relative position calculation between circuit patterns, then measurement capability is improved, but reliability deteriorates when circuit patterns are defective or missing
Solution Approach 1:
The patent uses partial matching by comparing contour information with the synthesized reference image rather than requiring complete pattern matching. This allows measurement to proceed even when some pattern elements are defective or missing, maintaining reliability through partial correspondence
Solution Approach 2:
The synthesized reference image created from multiple captured images serves as a cushion against defects. By aggregating information from multiple images, the reference contains redundant pattern information that compensates for missing or defective elements in individual images, ensuring measurement reliability
4Reliability
If multiple captured images are used to synthesize reference image, then measurement robustness is improved, but measurement time increases
Solution Approach 1:
The patent uses periodic scanning electron microscope imaging to capture multiple images at different positions. This periodic action systematically collects data that will be synthesized into the reference image, organizing the time-consuming process into regular, manageable cycles
Solution Approach 2:
The patent merges multiple captured images into a single synthesized reference image. This combining process consolidates redundant information from multiple images, creating a comprehensive reference that improves robustness while the merging operation itself optimizes processing 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
Enables easy and robust overlay measurement of actual patterns without CAD data, improving measurement accuracy and handling positional deviations in semiconductor manufacturing, thereby enhancing the precision of circuit pattern alignment.
Implementation Method 1
capturing images of a plurality of areas of a semiconductor device
Data Source
AI summary
A method for measuring overlay at a semiconductor device on which circuit patterns are formed by a plurality of exposure processes is characterized in including an image capturing step for capturing images of a plurality of areas of the semiconductor device, a reference image setting step for setting a reference image based on a plurality of the images captured in the image capturing step, a difference quantifying step for quantifying a difference between the reference image set in the reference image setting step and the plurality of images captured in the image capturing step, and an overlay calculating step for calculating the overlay based on the difference quantified in the difference quantifying step.