Critical Dimension Linearity Calibration Using Gaussian Blur
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Solution Overview
Problem
Semiconductor manufacturing requires improved metrology tools that provide accurate critical dimension measurements with high throughput, as current tools exhibit non-linear behavior due to differences in beam spot size and Gaussian blur, leading to discrepancies between CD-SEM and high-throughput metrology tools.
Innovation Solution
Applying a Gaussian transfer function to the profile of a workpiece image generated by an electron beam metrology tool, adjusting Gaussian blur to enhance correlation with a baseline, and selecting threshold values to determine non-linearity, allowing for linear measurement calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CD-SEM tool with smaller beam spot size is used for measurement, then measurement precision is improved, but productivity deteriorates due to low throughput
Solution Approach 1:
A Gaussian transfer function is introduced as an intermediary mathematical model to bridge the measurement differences between CD-SEM and high-throughput tools. The function characterizes the beam spot size effects and enables correction of measurement values from high-throughput tools to match CD-SEM reference measurements, resolving the contradiction by allowing high-throughput tools to achieve CD-SEM-level precision through computational correction
Solution Approach 2:
The invention changes the measurement parameters by applying a Gaussian transfer function with specific sigma values and threshold adjustments. By modifying the analysis parameters (Gaussian blur sigma, edge placement thresholds) of the high-throughput tool's measurement data, the system achieves measurement precision comparable to CD-SEM while maintaining high throughput capability
2Productivity
If high throughput tools with larger beam current and beam spot size are used, then productivity is improved, but measurement precision deteriorates due to non-linear gray level profiles
Solution Approach 1:
The system uses reference measurements from CD-SEM tools as feedback to calibrate and correct the measurements from high-throughput tools. By comparing high-throughput tool measurements against CD-SEM reference values and applying Gaussian transfer function corrections based on this feedback, the system achieves both high throughput and measurement precision
Solution Approach 2:
The Gaussian transfer function serves as a mathematical intermediary that transforms the non-linear gray level profiles from high-throughput tools into linear measurements that match CD-SEM reference data, enabling high-throughput tools to achieve measurement precision comparable to reference standards
3Productivity
If different beam spot sizes are used between tools, then productivity varies, but measurement consistency deteriorates due to different gray level profiles
Solution Approach 1:
The invention systematically adjusts measurement parameters including Gaussian blur sigma values and edge placement thresholds to compensate for different beam spot sizes. By changing these analysis parameters, the system achieves consistent measurements across tools with different beam characteristics, enabling measurement consistency while maintaining the productivity advantages of high-throughput tools
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 and linear critical dimension measurements across a wider range, aligning high-throughput tools with CD-SEM results by tuning blur sigma and edge placement thresholds, ensuring sensitivity and precision.
Implementation Method 1
receiving, at a processor, a profile of a feature on an image of a workpiece generated using an electron beam metrology tool
Data Source
AI summary
A Gaussian transfer function is applied to a profile of a feature on an image of a workpiece generated using an electron beam metrology tool. This generates an output profile. Non-linearity of the output profile is determined. Two threshold values can be selected and plotted on an XY plane. Proximity of a slope of the threshold values to a comparison value is determined.