Wafer Shape Metrology for Predicting Post-Bonding Overlay
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Solution Overview
Problem
Conventional methods for measuring post bonding overlay in semiconductor wafers require metrology targets on both wafers, which can complicate processing and limit measurement density.
Innovation Solution
A wafer metrology system that performs stress-free shape measurements on individual wafers and bonded pairs, using machine learning algorithms or mechanical models to predict overlay and provide feedback or feedforward adjustments to process tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metrology targets are placed on both wafers to measure post bonding overlay, then overlay measurement can be achieved, but processing complexity increases and measurement density is limited
Solution Approach 1:
The patent extracts the measurement requirement from the conventional approach by eliminating the need for metrology targets on both wafers. Instead, it uses shape measurements from a wafer shape metrology tool to predict overlay, thereby removing the complexity of target placement while maintaining measurement capability
Solution Approach 2:
The patent creates a virtual copy of the overlay measurement process by using shape measurements and prediction algorithms. Rather than directly measuring overlay with physical targets, the system copies the essential information (wafer shapes) and uses computational methods to derive overlay predictions, reducing processing complexity
2Measurement precision
If metrology targets are placed on both wafers, then overlay measurement is possible, but measurement density is limited
Solution Approach 1:
The patent makes the wafer shape metrology tool universal by enabling it to perform both shape measurements and overlay predictions. This multi-functionality allows the same tool and data to serve multiple purposes, increasing measurement density without requiring additional target-based measurement systems
Solution Approach 2:
The patent changes the measurement parameter from direct overlay measurement (requiring targets) to shape parameter measurement. By measuring wafer shapes and using prediction algorithms, the system transforms the measurement approach to enable higher density measurements across multiple wafers and bonding scenarios
3Measurement precision
If shape measurements are performed on individual wafers and bonded pairs, then overlay prediction accuracy improves, but measurement time increases
Solution Approach 1:
The patent performs shape measurements on individual wafers before bonding as a preliminary action. This allows overlay prediction to be prepared in advance, and the measurements can be performed in parallel or staged, reducing the critical path time while maintaining high prediction accuracy
Solution Approach 2:
The system maintains continuous useful action by using the same wafer shape metrology tool for measurements on individual wafers and bonded pairs. The continuous collection of shape data enables ongoing overlay predictions without interrupting the bonding process, optimizing the balance between accuracy and time
Data Source
AI summary
A wafer shape metrology system includes a wafer shape metrology sub-system configured to perform one or more stress-free shape measurements on a first wafer, a second wafer, and a post-bonding pair of the first and second wafers. The wafer shape metrology system includes a controller communicatively coupled to the wafer shape metrology sub-system. The controller is configured to receive stress-free shape measurements from the wafer shape sub-system; predict overlay between one or more features on the first wafer and the second wafer based on the stress-free shape measurements of the first wafer, the second wafer, and the post-bonding pair of the first wafer and the second wafer; and provide a feedback adjustment to one or more process tools based on the predicted overlay. Additionally, feedforward and feedback adjustments may be provided to one or more process tools.