Multiple Patterning Metrology via Non-Zero Diffraction Orders
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Solution Overview
Problem
Metrology systems face challenges in accurately measuring geometric errors induced by multiple patterning processes in semiconductor manufacturing, such as pitch walk and critical dimension variations, due to imperfections in techniques like double patterning lithography, which affect the precision and resolution of feature dimensions on semiconductor wafers.
Innovation Solution
The method involves using a combined measurement model that links structural and material parameters of single and multiple patterned metrology targets, with targets located close together to enhance accuracy, and analyzing diffracted light of non-zero orders to determine geometric errors, allowing for active feedback to process tools to improve output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple patterning processes are used to increase resolution, then feature density increases, but geometric errors such as pitch walk and critical dimension variations increase
Solution Approach 1:
The patent introduces an intermediary measurement system that uses optical diffraction to indirectly measure geometric errors. Instead of directly measuring the problematic multiple patterned features, the system uses a separate metrology target that undergoes the same multiple patterning process, measures its diffraction pattern, and infers the geometric errors from that measurement. This intermediary approach allows accurate measurement of pitch walk and critical dimension variations without directly confronting the measurement difficulties of the main features.
2Measurement precision
If conventional metrology methods are used to measure multiple patterned structures, then measurement simplicity is maintained, but measurement precision deteriorates
Solution Approach 1:
The patent creates a copy of the multiple patterning process applied to a dedicated metrology target. This metrology target is processed through the same lithography and etching steps as the main features, creating an identical copy of the process-induced geometric errors. By measuring this copied structure instead of the original features, the system achieves high measurement precision while keeping the measurement methodology relatively simple and familiar.
Solution Approach 2:
The patent changes the measurement parameter from direct spatial measurement to optical diffraction parameter measurement. Instead of trying to directly measure pitch and critical dimensions with physical probes or imaging systems, the system measures optical diffraction parameters (diffraction efficiency, angular positions) which are sensitive to geometric errors. This parameter transformation enables precise measurement of geometric errors that would be difficult to measure directly.
3Productivity
If single patterning is used, then process simplicity is maintained, but feature density and resolution are limited
Solution Approach 1:
The patent segments the patterning process into multiple distinct steps (first lithography, etching, second lithography, second etching) to achieve higher feature density. By breaking down the single patterning operation into sequential stages, each creating a subset of the final pattern, the system multiplies the effective resolution and feature density beyond what a single patterning step could achieve alone.
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 precise measurement of geometric errors, enhancing the accuracy of semiconductor feature dimensions and process control, thereby improving the yield and quality of semiconductor devices.
Implementation Method 1
analyzing diffracted light of non-zero orders to determine geometric errors
Data Source
Figure 1A~1D
Figure 2
Figure 3
AI summary
Methods and systems for evaluating the performance of multiple patterning processes are presented. Patterned structures are measured and one or more parameter values characterizing geometric errors induced by the multiple patterning process are determined. In some examples, a single patterned target and a multiple patterned target are measured, the collected data fit to a combined measurement model, and the value of a structural parameter indicative of a geometric error induced by the multiple patterning process is determined based on the fit. In some other examples, light having a diffraction order different from zero is collected and analyzed to determine the value of a structural parameter that is indicative of a geometric error induced by a multiple patterning process. In some embodiments, a single diffraction order different from zero is collected. In some examples, a metrology target is designed to enhance light diffracted at an order different from zero.