Lithographic Tool Fingerprint Correction via Minimal Parameter Modeling
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Solution Overview
Problem
Current methods for characterizing and correcting process fingerprints in lithographic tools are inefficient, requiring a large number of measurements and failing to optimize noise reduction, leading to unwieldy correction processes and reduced spatial resolution.
Innovation Solution
A method involving measuring process data, fitting a process signature model, and using it to calculate corrections for the lithographic tool, which reduces the number of necessary measurements and improves noise reduction by using a minimal number of parameters to characterize deviations, enabling more accurate and efficient corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional fingerprint characterization methods are used to correct lithographic tool imperfections, then corrections can be applied to reduce overlay errors, but the process requires a large number of measurements and becomes unwieldy
Solution Approach 1:
The patent extracts only the essential parameters needed to characterize the process fingerprint from the full set of possible measurements. By identifying and measuring only the critical parameters that actually influence overlay errors, the method reduces the measurement burden while maintaining correction effectiveness.
Solution Approach 2:
The patent creates a simplified model (fingerprint model) that copies only the essential characteristics of the lithographic tool's imperfections. This model uses minimal parameters to represent the complex tool behavior, enabling efficient corrections without requiring full characterization of all tool parameters.
2Measurement precision
If traditional fingerprint characterization methods are used, then process corrections can be calculated, but noise reduction is not optimized and spatial resolution is reduced
Solution Approach 1:
The patent applies local quality by tailoring the measurement approach to the specific characteristics of each tool and process combination. Instead of using a uniform measurement strategy, the method identifies the local essential parameters specific to each lithographic tool's fingerprint, optimizing measurement precision for that particular application while avoiding unnecessary measurements that would lose spatial information.
Solution Approach 2:
The patent changes the parameter set used for fingerprint characterization from a comprehensive set to a minimal essential set. By selecting only the parameters that have the greatest impact on overlay errors and removing redundant parameters, the method improves signal-to-noise ratio and preserves spatial resolution while maintaining correction accuracy.
3Reliability
If a large number of measurements are taken to characterize process fingerprints, then more complete tool imperfections can be captured, but the measurement process becomes time-consuming and inefficient
Solution Approach 1:
The patent extracts only the essential parameters from the full measurement space, measuring only what is necessary to characterize the process fingerprint accurately. This selective measurement approach captures the critical tool imperfections while eliminating redundant measurements, thereby improving measurement efficiency without sacrificing characterization reliability.
Solution Approach 2:
The patent applies partial action by performing only the necessary measurements required for accurate fingerprint characterization rather than exhaustive measurements of all possible parameters. This partial measurement strategy is sufficient to capture the essential tool imperfections and enables efficient corrections without the time cost of complete characterization.
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 more accurate and less noisy fingerprint corrections with fewer measurements, improving fabrication performance and process control by reducing lot-to-lot and wafer-to-wafer variations, and enabling more meaningful key performance indicators.
Implementation Method 1
a scatterometer in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered or reflected beam are measured
Implementation Method 2
properties of the scattered or reflected beam are measured
Data Source
AI summary
A method of calculating process corrections for a lithographic tool, and associated apparatuses. The method comprises measuring process defect data on a substrate that has been previously exposed using the lithographic tool; fitting a process signature model to the measured process defect data, so as to obtain a model of the process signature for the lithographic tool; and using the process signature model to calculate the process corrections for the lithographic tool.