Pattern Measurement Device Variability Calculation
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Solution Overview
Problem
The miniaturization of semiconductor patterns leads to increased complexity in measuring shape variability and roughness, where measurement errors from scanning electron microscopes (SEM) complicate proper process control due to variability in electron emission, making it difficult to distinguish between true shape changes and measurement reproducibility errors.
Innovation Solution
A pattern measurement device calculates variability by separating measurement reproducibility error from true shape variability using the formula σ2_observed=σ2_pattern/Np + σ2_sem/(Np·Nframe), where σ2_pattern represents shape variability, σ2_sem represents measurement reproducibility error, Np is the number of measurement points, and Nframe is a device condition-dependent value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurement points are used to evaluate pattern shape variability, then measurement coverage is improved, but measurement variability due to SEM fluctuation increases
Solution Approach 1:
The patent segments the total measured variability into two distinct components: pattern variability (σ²_pattern) representing true shape changes, and measurement variability (σ²_measurement) representing SEM fluctuation. This segmentation allows separate evaluation and compensation of each component, enabling accurate pattern shape assessment despite multiple measurement points introducing additional measurement noise.
Solution Approach 2:
The patent establishes a feedback mechanism where measurement variability is continuously monitored and used to adjust the evaluation process. By calculating measurement variability from repeated measurements and comparing it against pattern variability, the system can determine whether observed changes represent true pattern variations or measurement noise, thereby improving reliability of variability assessment.
2Measurement precision
If repeated measurements are performed to reduce measurement error, then measurement accuracy is improved, but time consumption increases
Solution Approach 1:
The patent applies partial action by performing a limited number of repeated measurements (typically 3-5 times) rather than exhaustive measurement. This partial repetition is sufficient to statistically characterize measurement variability without incurring excessive time costs, achieving an optimal balance between accuracy improvement and time consumption.
Solution Approach 2:
The patent performs preliminary measurements to establish the measurement variability baseline before final pattern shape evaluation. By conducting these preliminary repeated measurements first, the system pre-characterizes the measurement system's noise level, which then informs the interpretation of subsequent measurements and reduces the need for excessive repeated measurements during actual evaluation.
3Productivity
If device conditions are optimized for measurement speed, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent systematically evaluates the relationship between device condition parameters (such as electron beam current, scanning speed, magnification) and measurement precision. By establishing quantitative relationships between these parameters and measurement variability, the system can select optimal parameter combinations that maintain sufficient precision while maximizing measurement throughput, rather than using fixed conservative settings.
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 allows for accurate selection of device conditions to minimize measurement errors, enabling reliable process control and improved reproducibility in semiconductor manufacturing by isolating true shape variability from measurement variability.
Implementation Method 1
in a case of a SEM that detects electrons obtained based on scanning of an electron beam
Implementation Method 2
a SEM that detects electrons obtained based on scanning of an electron beam
Data Source
AI summary
A purpose of the present invention is to provide a pattern measurement device that allows the selection of device conditions for calculating proper variability and allows the estimation of proper variability. The present invention provides a pattern measurement device comprising a computation processing device that, on the basis of a plurality of measured values acquired by a charged particle radiation device, calculates the variability of the measured values of a pattern that is the object of measurement, said pattern measurement device characterized in that a variability σmeasured of the plurality of measured values formed at different positions and σ2observed=σ2pattern/Np+σ2sem0/(Np·Nframe) are used to calculate σSEM0, which indicates measurement reproducibility error. σpattern0 is the variability due to pattern shape error, Np is the number of measurement points, and Nframe is a value that changes according to device conditions.