Single-Wafer Overlay Metrology With Tool-Induced Shift Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spectral ellipsometry methods for overlay metrology are hindered by Tool Induced Shift (TIS) errors, which require time-consuming measurements in two wafer orientations to correct, increasing costs and measurement time.
Innovation Solution
A spectroscopic metrology system generates a TIS model using off-diagonal Mueller matrix elements to infer a TIS signature, allowing TIS correction from a single azimuthal angle measurement, reducing the need for dual orientation measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual orientation measurements are performed to correct TIS errors, then measurement accuracy is improved, but measurement time and cost increase
Solution Approach 1:
The system performs preliminary characterization of the optical path using training samples to build a TIS model before actual measurements. This pre-established model captures the asymmetric response of the optical system, enabling TIS correction without requiring dual orientation measurements during production testing, thus resolving the time-accuracy tradeoff
Solution Approach 2:
The system creates a virtual model (TIS model) that replicates the asymmetric behavior of the optical path based on training data. This copied behavioral model is then applied to correct test measurements, eliminating the need for physical dual-orientation measurements while maintaining correction accuracy
2Measurement precision
If dual orientation measurements are performed to correct TIS errors, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The system performs preliminary characterization of the optical path using training samples to build a TIS model before actual measurements. This pre-established model captures the asymmetric response of the optical system, enabling TIS correction without requiring dual orientation measurements during production testing, thus resolving the time-accuracy tradeoff
Solution Approach 2:
The system creates a virtual model (TIS model) that replicates the asymmetric behavior of the optical path based on training data. This copied behavioral model is then applied to correct test measurements, eliminating the need for physical dual-orientation measurements while maintaining correction accuracy
3Measurement precision
If spectral ellipsometry with asymmetric architecture is used, then overlay metrology capability is achieved, but TIS errors are introduced
Solution Approach 1:
The system extracts and isolates the TIS component from the total measurement signal by analyzing the asymmetric response in the Mueller matrix elements. By separating the TIS contribution from the true overlay signal, the system can remove the harmful TIS errors while preserving the useful overlay measurement capability
Solution Approach 2:
The TIS model acts as an intermediary that mediates between the raw asymmetric measurements and the corrected overlay values. The model translates the asymmetric optical path effects into quantifiable TIS corrections, enabling the system to maintain spectral ellipsometry's measurement capability while eliminating its primary source of error
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
The method significantly reduces measurement time by correcting TIS errors in a single orientation, maintaining accuracy while minimizing hardware modifications to existing systems.
Implementation Method 1
spectroscopic ellipsometry methods have been developed, particularly for measuring after-etch inspection (AEI) device OVL
Data Source
AI summary
A metrology system may include a spectroscopic metrology sub-system and a controller, the controller including one or more processors configured to execute program instructions configured to cause the one or more processors to: generate a tool-induced shift (TIS) model of a training sample by the metrology sub-system comprising: receiving training data from metrology measurements of the training sample, the training data comprising spectral data associated with at least one off-diagonal Mueller matrix element generated by one or more first measurements of the training sample at a first azimuthal angle and one or more second measurements of the training sample at a second azimuthal angle, deriving overlay spectra data and TIS spectra data from the training data, decomposing the overlay spectra data and the TIS spectra data, and inferring a TIS signature for the training sample; and to remove the TIS signature from a test sample.