CD-SEM Extraction Using Multiple Cut-lines for Lithography Model Calibration
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Solution Overview
Problem
Conventional single-cut-line-based CD extraction techniques in semiconductor manufacturing are not sufficiently accurate, leading to inaccuracies in lithography process models, especially as technology nodes shrink below 45 nm, affecting the accuracy of photolithography process model calibration and post-OPC design layout verification.
Innovation Solution
A measurement-window-based CD-SEM extraction technique is employed, where multiple CD values are measured along multiple electron beam scans within a centered measurement window, and a set of CD extraction cut-lines are placed within this window based on a placement spacing parameter, allowing for the determination of simulated CD values by averaging single-cut-line CD values, and iteratively updating the photolithography process model parameters to minimize differences between simulated and measured CD values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-cut-line-based CD extraction technique is used, then the extraction process is simple and fast, but the measurement precision of CD values deteriorates
Solution Approach 1:
The patent divides the single CD measurement into multiple measurements by placing multiple cut-lines (e.g., three cut-lines) across the target feature. Each cut-line provides an independent CD measurement, and the final CD value is derived from combining these multiple measurements (e.g., averaging), thereby improving measurement precision while maintaining process efficiency
Solution Approach 2:
The patent creates multiple copies of the measurement operation by placing multiple cut-lines at different positions across the same target feature. Each cut-line acts as a copy of the measurement probe, providing redundant measurements that can be averaged to reduce random errors and improve overall measurement accuracy
2Ease of manufacture
If a single-cut-line-based CD extraction technique is used, then the process model creation is straightforward, but the manufacturing precision of lithography models deteriorates
Solution Approach 1:
The patent segments the CD extraction process into multiple measurements using multiple cut-lines, allowing the lithography process model to be calibrated against more accurate and representative CD data. This segmentation of measurement points provides a better basis for model fitting and parameter extraction, improving overall model accuracy
Solution Approach 2:
The patent changes the measurement parameters by using multiple cut-lines to extract multiple CD values from the same target feature. This parameter change in the measurement approach provides more data points for model calibration, enabling more accurate determination of lithography process parameters and improving model predictive capability
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 enhances the accuracy of photolithography process model calibration and post-OPC design layout verification by improving the precision of CD extraction, reducing inaccuracies and stabilizing the model parameters, thereby ensuring better manufacturability and quality of semiconductor chips.
Implementation Method 1
measuring multiple CD values of a feature along multiple electron beam scans on the wafer surface
Data Source
AI summary
One embodiment of the present invention relates to a process that models critical-dimension (CD) scanning-electron-microscopy (CD-SEM) extraction during photolithography process model calibration. During operation, the process receives measured CD values which were obtained using a CD-SEM extraction process, wherein the CD-SEM extraction process determines a measured CD value for a feature by measuring multiple CD values of the feature along multiple electron beam scans. The process then determines simulated CD values, wherein a simulated CD value is determined based at least on a set of CD extraction cut-lines evenly placed around the target feature. During subsequent photolithography process model calibration, the process fits a parameter that models an aspect of the photolithography process based at least on both the measured CD values and the simulated CD values.