Magnetic Wafer Alignment Marks for Sub-0.1 μm Bonding Accuracy
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Solution Overview
Problem
Existing wafer bonding techniques face challenges in achieving precise alignment and reducing misalignment and warpage in stacked semiconductor devices, which affect the accuracy and reliability of integrated circuits.
Innovation Solution
The use of magnetic alignment marks with opposite magnetic polarity on semiconductor wafers that are magnetically attracted to each other during bonding, combined with optical alignment, to achieve self-alignment and reduce misalignment and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional wafer bonding techniques are used, then bonding can be achieved, but alignment precision is insufficient and misalignment occurs
Solution Approach 1:
Magnetic alignment marks are introduced as intermediary elements between the wafers to be bonded. These marks contain magnetic features that generate magnetic forces to attract and align the wafers precisely during the bonding process, thereby achieving sub-0.1 μm alignment precision and reducing misalignment.
2Reliability
If conventional wafer bonding is performed, then bonding is achieved, but warpage occurs in the stacked devices
Solution Approach 1:
Magnetic alignment marks serve as intermediary elements that not only facilitate alignment but also help control warpage. The magnetic forces generated by these marks during bonding ensure uniform contact and reduce differential stress between wafers, thereby minimizing warpage in the final stacked device structure.
3Measurement precision
If magnetic alignment marks with opposite polarity are used, then self-alignment is achieved with precision less than 0.1 μm, but the device complexity increases
Solution Approach 1:
The magnetic alignment marks are designed to automatically generate aligning forces through their opposite magnetic polarities when brought into proximity. This self-aligning mechanism eliminates the need for complex external alignment equipment or manual adjustment processes, achieving sub-0.1 μm precision while actually simplifying the overall bonding process.
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 method enhances the accuracy of wafer alignment to less than 0.1 μm misalignment and reduces warpage, improving the precision and reliability of stacked semiconductor devices.
Implementation Method 1
magnetic alignment marks with opposite magnetic polarity on semiconductor wafers that are magnetically attracted to each other during bonding
Data Source
AI summary
In an embodiment, a method includes: receiving a first wafer and a second wafer, the first wafer including a first alignment mark, the first alignment mark including a first grid of first magnetic features, the second wafer including a second alignment mark, the second alignment mark including a second grid of second magnetic features; aligning the first alignment mark with the second alignment mark in an optical alignment process; after the optical alignment process, aligning the first alignment mark with the second alignment mark in a magnetic alignment process, north poles of the first magnetic features being aligned with south poles of the second magnetic features, south poles of the first magnetic features being aligned with north poles of the second magnetic features; and forming bonds between the first wafer and the second wafer.