Bonded Wafer Sampling Scheme for Central Overlay Singularities
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Solution Overview
Problem
Existing process control methods in integrated device manufacturing, particularly in wafer-to-wafer bonding, fail to effectively address large overlay errors and grid deformations at the central location of bonded substrates, leading to inefficiencies and inaccuracies in pattern application.
Innovation Solution
A method for optimizing a sampling scheme on bonded substrates by determining and adjusting the sampling locations to account for large overlay errors and grid deformations at the central location, using techniques such as radial basis function modeling and support vector machines to improve alignment and overlay measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard sampling scheme is used on bonded substrates, then the metrology process is simple and fast, but the measurement accuracy is poor due to large overlay errors and grid deformations at the central location
Solution Approach 1:
The patent applies local quality by implementing a non-uniform sampling scheme where the density and distribution of sampling locations are adapted to local conditions on the substrate. Specifically, the sampling scheme concentrates more measurement points in regions with large overlay errors and grid deformations (such as the central location of bonded substrates) while using fewer points in regions with smaller errors. This localized adaptation of sampling density ensures that measurement accuracy is improved where it is most needed without unnecessarily increasing the overall complexity and measurement time across the entire substrate.
Solution Approach 2:
The patent implements dynamics by making the sampling scheme adaptive and variable rather than static and uniform. The sampling locations and densities are dynamically adjusted based on the specific characteristics of each substrate and bonding process, allowing the metrology system to respond to varying error conditions across different regions of the substrate. This dynamic approach enables the system to optimize measurement accuracy for each specific case while maintaining reasonable process complexity.
2Manufacturing precision
If sampling locations are optimized to address central wafer singularities, then pattern reproduction accuracy is improved, but the metrology effort and process complexity increase
Solution Approach 1:
The patent applies local quality by concentrating enhanced sampling efforts specifically at the central location of bonded substrates where large overlay errors and grid deformations occur, rather than uniformly increasing sampling across the entire substrate. This localized approach to optimizing sampling locations ensures that pattern reproduction accuracy is improved in the most critical regions while minimizing the additional metrology effort required, thus reducing the time penalty compared to a comprehensive uniform sampling approach.
3Productivity
If a uniform sampling scheme is used across the substrate, then the sampling process is simple and quick, but it fails to capture the singularity effects at the central location of bonded substrates
Solution Approach 1:
The patent applies local quality by implementing a non-uniform sampling scheme that adapts the sampling density to the local error characteristics of different substrate regions. Specifically, the scheme increases sampling density at the central location of bonded substrates where large overlay errors and grid deformations occur, while maintaining lower sampling density in regions with smaller errors. This localized adaptation ensures that critical overlay error information is captured without requiring a uniform increase in sampling across the entire substrate, thus maintaining reasonable metrology throughput while preventing information loss in critical regions.
Data Source
AI summary
A method and associated apparatuses for optimizing a sampling scheme which defines sampling locations on a bonded substrate, having undergone a wafer to wafer bonding process. The method includes determining a sampling scheme for a metrology process and optimizing the sampling scheme with respect to a singularity defined by a large overlay error and/or grid deformation at a central location on the bonded substrate to obtain a modified sampling scheme.