Pattern Shape Evaluation Using 2D-MtT to Reduce EPE Variability
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Solution Overview
Problem
Edge placement error (EPE) measurement in pattern shape evaluation is influenced by pattern size, shape, layout, and measurement region, making it difficult to obtain an absolute evaluation value without category-specific influences.
Innovation Solution
A pattern shape measuring method that involves acquiring SEM image data, extracting contour data, and calculating a pattern shape evaluation value based on the difference between measurement and design data, using units like 2D-MtT, to evaluate the shape of mask patterns while minimizing the impact of pattern category variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EPE measurement is used to evaluate mask pattern shape, then pattern shape evaluation can be performed, but the evaluation value changes depending on pattern size, shape, layout, and measurement region, making it difficult to obtain absolute evaluation values
Solution Approach 1:
The patent changes the evaluation parameter from EPE (edge placement error) to 2D-MtT (two-dimensional minimum total tangent distance). This parameter transformation allows the evaluation to be standardized by dividing the contour difference area by the perimeter length, making the evaluation value independent of pattern size and category while maintaining measurement precision.
2Manufacturing precision
If EPE measurement is used, then pattern shape can be evaluated, but the measurement is influenced by pattern category variations such as size, shape, and layout
Solution Approach 1:
The patent transforms the evaluation parameter from EPE to 2D-MtT, where 2D-MtT is calculated by dividing the area of contour difference by the perimeter length of the measurement pattern. This parameter change eliminates the harmful influence of pattern category variations (size, shape, layout) while maintaining the ability to evaluate mask pattern shape accuracy for manufacturing precision control.
Solution Approach 2:
The patent uses measurement patterns that are extracted and compared against design data, creating a standardized evaluation model that copies the essential geometric relationships while removing category-specific variations. This allows consistent evaluation across different pattern types.
3Measurement precision
If standardized evaluation is implemented using 2D-MtT, then absolute evaluation values can be obtained, but additional calculation steps are required compared to simple EPE measurement
Solution Approach 1:
The patent introduces a new parameter 2D-MtT that requires calculating the area of contour difference and dividing by the perimeter length. While this adds calculation steps compared to simple EPE measurement, it provides absolute evaluation values that are not influenced by pattern category, achieving higher measurement precision through standardized computation.
Data Source
AI summary
According to one embodiment, an image data of a measurement object including a pattern is acquired. First data is acquired by extracting a contour of an element in composition of the pattern from the image data. Second data that specifies a design data of the measurement object and the pattern of the measurement object is acquired. The design data includes a pattern data. A measurement pattern is extracted by using the first data and the second data. An evaluation value for the measurement pattern with respect to the design data is calculated based on the difference between the measurement pattern and the design data.