Electron Microscope Pattern Measurement Shrinkage Correction
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Solution Overview
Problem
Current methods for measuring fine patterns in semiconductor manufacturing, such as those using ArF lithography, face challenges in accurately estimating shrinkage and correcting errors caused by charging and primary coating material influences, especially for complex two-dimensional shapes and varying primary coating materials, leading to imprecise dimension and contour measurements.
Innovation Solution
A method involving the use of a charged particle beam on a sample with a different primary coating material, along with data processing to calculate pre-shrinking dimensions and contours by accounting for pattern and primary coating material shrinkage parameters, and beam conditions, utilizing image processing techniques to correct for charging errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charged particle beam (electron beam) is used to measure the fine resist sample, then the measurement process can be performed, but the pattern contracts (shrinks) due to irradiation and the dimension and shape change
Solution Approach 1:
The patent performs multiple measurements before significant shrinkage occurs and uses the initial measurement as a reference. By conducting measurements in sequence and comparing subsequent measurements to the first measurement, the system captures dimensional changes due to shrinkage and corrects for them, thereby obtaining accurate pre-shrinkage dimensions.
Solution Approach 2:
The patent establishes a feedback loop where measurement results are used to correct subsequent measurements. The system calculates shrinkage based on the difference between the first measurement and subsequent measurements, then applies this correction to obtain accurate dimensional data, creating a closed-loop correction mechanism.
2Measurement precision
If a charged particle beam is used to measure the fine resist sample, then the measurement can be performed, but charging occurs on the sample surface causing orbit changes and signal electron return, making the SEM image locally dark
Solution Approach 1:
The patent uses feedback by comparing the first SEM image (taken before significant charging occurs) with subsequent images. The system detects local darkening caused by charging and uses the initial image as a reference to correct the contour information, thereby compensating for charging effects and maintaining measurement accuracy.
3Measurement precision
If multiple measurements are performed to estimate shrinkage, then the shrink curve can be obtained, but the measurement time increases
Solution Approach 1:
The patent performs the first measurement quickly as a reference point before significant shrinkage occurs. By establishing this initial reference measurement, the system reduces the need for numerous subsequent measurements to determine pre-shrinkage dimensions, as the first measurement already provides baseline data for correction.
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 enables highly precise determination of pattern contours and dimensions, even under electron beam irradiation, by accurately accounting for primary coating material influences and charging effects, improving measurement accuracy for complex patterns.
Implementation Method 1
contraction (shrink) of the pattern of the resist sample caused by irradiation with an electron beam is generated and the dimension and the shape are changed
Implementation Method 2
since the resist sample is generally an insulator, there are cases where charging occurs on the sample surface caused by irradiation with the electron beam. In a case where charging occurs, the orbit of an incident electron beam is changed and some of signal electrons generated from the sample are brought back by positive charging of the sample surface
Data Source
AI summary
The objective of the invention is to provide a measuring method that can determine pattern contours and dimensions with high precision even if an object to be measured shrinks due to electron beam radiations. In order to achieve this objective, a method, which performs measurements by irradiating an electron beam onto a sample having a pattern formed on a primary coating thereof, prepares an SEM image and contour of the pattern (S201, S202), material parameters of the pattern part and primary coating part of the sample (S203, S204), and a beam condition in irradiating the electron beam onto the sample (S205), and uses these prepared things to calculate a pattern shape or dimensions before the irradiation of the electron beam (S206).