Pattern Misalignment Measurement Using SEM Image Contour Matching
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Solution Overview
Problem
Current methods for measuring pattern misalignment in semiconductor manufacturing, such as optical measurement and SEM imaging, face challenges in accuracy due to uneven patterns and overlapping layers, leading to decreased measurement reliability and inability to directly measure the main semiconductor device pattern.
Innovation Solution
A method involving SEM image data processing using pattern matching techniques to calculate shift amounts and standard deviations between design and image data contours, stabilizing the measurement region to improve accuracy and reliability of misalignment measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical measurement method is used to measure misalignment through film layers, then measurement accessibility is improved and marks can be frequently measured, but measurement precision deteriorates due to inability to directly measure main patterns and requirement for larger measurement marks
Solution Approach 1:
The patent replaces optical measurement with electron beam-based SEM imaging to directly observe and measure main patterns without interference from overlying film layers, achieving higher measurement precision while maintaining measurement accessibility through automated image processing and pattern matching algorithms
Solution Approach 2:
The patent creates digital copies of pattern contours from SEM images and design data, then performs pattern matching on these digital representations to calculate misalignment, avoiding the limitations of direct optical measurement while preserving measurement efficiency
2Measurement precision
If SEM image method is used to directly measure main pattern misalignment, then measurement precision is improved with higher spatial resolution, but measurement reliability deteriorates due to local region information limitation and pattern overlapping conditions
Solution Approach 1:
The patent divides the measurement process into distinct segments: acquiring multiple SEM images of different regions, extracting contours from each image, performing pattern matching separately for each region, and then synthesizing results to calculate overall misalignment, thereby overcoming the limitation of local region information
Solution Approach 2:
The patent implements feedback by calculating standard deviation of spacing between design contours and image contours to assess measurement stability, and using this feedback to determine whether the measurement result is reliable or if additional measurements are needed
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
The method achieves high spatial resolution for misalignment measurement, enhancing the reliability and accuracy of pattern alignment correction in semiconductor devices by stabilizing the variation of contour spacing, thus improving the lithography process.
Implementation Method 1
use of a scanning electron microscope (SEM) secondary electron image (hereinafter referred to as SEM image)
Data Source
AI summary
According to one embodiment, a method for measuring pattern misalignment, includes: a first step obtaining image data; a second step specifying a measurement region; a third step calculating a first shift amount (x1, y1); a fourth step determining, after calculating the first shift amount, a first distribution; a fifth step executing a plurality of times the second step, the third step, and the fourth step; a seventh step calculating a second shift amount (x2, y2); an eighth step determining, after calculating the second shift amount, a second distribution; a ninth step executing a plurality of times the sixth step, the seventh step, and the eighth step; and a tenth step calculating a difference (x2−x1, y2−y1) between the second pattern misalignment and the first pattern misalignment.