Charged Particle Beam Pattern Measurement Edge Width Correction
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Solution Overview
Problem
Conventional scanning electron microscopes struggle to accurately measure line widths of patterns with small edge widths due to the influence of electron beam diameter, leading to measurement errors.
Innovation Solution
A pattern measurement apparatus and method that involves creating a reference-beam intensity distribution by scanning a charged particle beam over a reference pattern, calculating edge widths for patterns with varying inclination angles, and using a correspondence table to correct edge positions and measure line widths accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scanning electron microscope methods are used to measure line widths, then the measurement process is simple, but measurement precision deteriorates when edge width is smaller than beam diameter
Solution Approach 1:
The patent applies preliminary action by creating a correspondence table in advance that stores the relationship between measured line widths and actual line widths for various edge widths and inclination angles. During actual measurement, the system simply looks up the correction value in this pre-created table, avoiding complex real-time calculations while achieving high precision even when edge width is smaller than beam diameter.
Solution Approach 2:
The patent changes parameters by considering multiple inclination angles (0°, 15°, 30°, 45°, 60°, 75°, 90°) and various edge widths to create comprehensive correction data. By varying these parameters during table creation, the system can accurately correct measurements under different pattern conditions without increasing operational complexity.
2Measurement precision
If the electron beam diameter is reduced to improve measurement precision, then measurement precision improves, but the influence of beam width on measurement accuracy increases when edge width is small
Solution Approach 1:
The patent converts the harmful effect of beam width influence into a benefit by creating a correspondence table that quantifies the relationship between measured line width and actual line width for various beam conditions. Instead of trying to eliminate beam width effects, the system uses them predictably to correct measurements, transforming the harmful factor into a useful correction mechanism.
Solution Approach 2:
The correspondence table acts as an intermediary between the raw measurement data and the actual line width. It mediates the complex relationship between beam parameters, edge geometry, and measurement results, providing a straightforward lookup mechanism that eliminates the need for complex real-time beam parameter optimization.
3Measurement precision
If correction values are calculated for all possible inclination angles and edge widths, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies partial action by selecting representative inclination angles (0°, 15°, 30°, 45°, 60°, 75°, 90°) and typical edge widths rather than covering every possible value. This provides sufficient measurement accuracy for practical applications while keeping the correspondence table size manageable and the system complexity reasonable.
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 accurate length measurement of patterns with small edge widths by accounting for the electron beam's influence, improving measurement precision and reliability.
Implementation Method 1
a sample is irradiated with and scanned by incident electrons within an electron beam scanning range, and secondary-electrons emitted from the sample are acquired through a scintillator
Data Source
AI summary
A pattern measurement apparatus includes a beam intensity distribution creation unit to scan a charged particle beam over a reference pattern having edge portions formed at a right angle to create a line profile of the reference pattern and thus create a reference-beam intensity distribution, an edge width detection unit to determine line profiles for pattern models including edges formed at various inclination angles by use of the reference-beam intensity distribution and calculate edge widths reflecting an influence of a width of a reference beam, and a correspondence table creation unit to calculate correction values for edge positions from the calculated edge widths and the pattern models and create a correspondence table in which the edge widths and the correction values are associated with one another.