Adaptive Wafer Receiving Surface for Sub-Micron Bond Alignment
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Solution Overview
Problem
Existing technologies face challenges in achieving high alignment accuracy for wafers beyond 2 μm, especially due to mechanical distortions during the pre-bonding and bonding processes, which affect the precision of structures on wafers, particularly in applications like lithography for CMOS image sensors where alignment demands are stringent.
Innovation Solution
A receiving means with active control elements that allow for precise alignment by detecting strain and stress maps, using temperature control and piezoelements to compensate for local distortions, and enabling in-situ monitoring and correction of alignment errors, ensuring accurate positioning of wafers before forming a permanent bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional receiving means with flat mounting surface are used, then the device complexity is low, but the alignment precision deteriorates beyond 2 μm due to mechanical distortions during bonding
Solution Approach 1:
The mounting surface is transformed from a static rigid structure to a dynamic adaptive surface using piezoelectric actuators. These actuators can individually adjust the position of mounting surface regions in real-time during the bonding process, allowing the surface to dynamically compensate for mechanical distortions and maintain alignment precision better than 2 μm throughout the bonding operation.
Solution Approach 2:
The system changes physical parameters of the mounting surface by controlling piezoelectric actuators to adjust local positions and orientations. This parameter adjustment allows compensation for thermal expansion, mechanical stress-induced distortions, and other dynamic changes during bonding, maintaining alignment precision without requiring an entirely new device architecture.
2Manufacturing precision
If active control elements are added to the receiving means, then the alignment precision improves to better than 0.1 μm, but the device complexity increases
Solution Approach 1:
The system incorporates sensors that continuously monitor the actual positions of wafers and the mounting surface during bonding. This feedback information is fed to a control system that calculates required adjustments and commands the piezoelectric actuators to compensate for deviations in real-time, achieving alignment precision better than 0.1 μm through closed-loop control rather than open-loop complexity.
Solution Approach 2:
Complex mechanical adjustment mechanisms are replaced with piezoelectric actuators that provide precise, electrically-controlled position adjustments. This substitution reduces mechanical complexity while achieving superior alignment precision, as piezoelectric elements can make sub-micron adjustments without the bulk and complexity of traditional mechanical positioning systems.
3Ease of manufacture
If the mounting surface is kept flat and rigid, then the ease of manufacture is high, but the alignment accuracy deteriorates due to uncorrected distortions during pre-bonding and bonding
Solution Approach 1:
The mounting surface is divided into multiple independently controllable regions, each with its own piezoelectric actuator. This segmentation allows localized compensation for distortions without requiring the entire surface to be complex or difficult to manufacture. Each segment can be adjusted independently while maintaining the overall flat rigid structure, preserving ease of manufacture while improving alignment accuracy.
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 alignment accuracies better than 0.1 μm, allowing for reliable and precise alignment of wafers, minimizing distortions, and ensuring the quality of subsequent process steps like lithography by correcting alignment errors before forming a permanent bond.
Implementation Method 1
piezoelements to compensate for local distortions
Implementation Method 2
temperature control and piezoelements to compensate for local distortions
Data Source
AI summary
A receiving means for receiving and mounting of wafers, comprised of a mounting surface, mounting means for mounting a wafer onto the mounting surface and compensation means for active, locally controllable, compensation of local and/or global distortions of the wafer.