Wafer Alignment Markers Using Magnetic Detection
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Solution Overview
Problem
Conventional methods for aligning semiconductor wafers during photolithography and other semiconductor processing steps are prone to misalignment due to changes in alignment markers caused by fabrication processes, leading to structural deficiencies and yield loss.
Innovation Solution
The use of alignment systems that detect and measure magnetic attributes of ferromagnetic or antiferromagnetic alignment markers within the wafer, applying a magnetic field to magnetize them, and determining their locations relative to an ideal grid to compensate for deviations and align the wafer accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical alignment markers are used, then alignment can be performed, but the markers are altered by fabrication processes (deposition, oxide growth, removal) causing misalignment
Solution Approach 1:
The patent changes the detection parameter from optical properties to magnetic properties. Alignment markers are formed with ferromagnetic or antiferromagnetic materials that maintain stable magnetic characteristics through fabrication processes. The magnetic field detection method is insensitive to optical alterations caused by deposition, oxide growth, and removal processes, thereby resolving the contradiction between measurement precision and marker stability.
Solution Approach 2:
The patent replaces the optical detection system with a magnetic detection system. Instead of using optical microscopes to read alignment markers, the system uses magnetic field sensors to detect the magnetic signature of ferromagnetic or antiferromagnetic alignment markers. This substitution eliminates the problem of optical property changes during fabrication while maintaining alignment accuracy.
2Measurement precision
If manual alignment methods are used, then operators can adjust wafer position, but the process is slow and inaccurate with high yield loss
Solution Approach 1:
The alignment system performs self-alignment by automatically detecting the magnetic field signature of alignment markers and calculating the required wafer position adjustments. The system eliminates the need for manual operator intervention, providing both high precision through magnetic field detection and high productivity through automated processing. The controller automatically computes alignment corrections and directs wafer positioning based on detected marker locations.
3Measurement precision
If optical alignment markers are used, then alignment can be performed, but opaque material levels and surface topography interfere with marker visibility
Solution Approach 1:
The patent replaces optical detection with magnetic field detection. Magnetic fields penetrate opaque materials and are not affected by surface topography or material composition. The magnetic alignment markers maintain their detectability regardless of overlying material layers, eliminating optical interference problems while preserving detection accuracy.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary for detecting alignment markers. Instead of using light that is blocked by opaque materials, the system uses magnetic fields that can penetrate through materials to reach and detect the magnetic alignment markers. This intermediary approach allows marker detection without being affected by intervening material layers or surface conditions.
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 provides precise alignment of wafers, unaffected by opaque material levels or surface topography, allowing for smaller marker sizes and improved accuracy, reducing yield loss and structural deficiencies.
Implementation Method 1
The alignment marker exhibits a magnetic response to an applied magnetic field that is detectable by a sensor.
Implementation Method 2
alignment markers exhibiting ferromagnetic or antiferromagnetic characteristics
Implementation Method 3
alignment markers exhibiting ferromagnetic or antiferromagnetic characteristics
Data Source
AI summary
A method of aligning a wafer for semiconductor fabrication processes may include applying a magnetic field to a wafer, detecting one or more residual magnetic fields from one or more alignment markers within the wafer, responsive to the detected one or more residual magnetic fields, determining locations of the one or more alignment markers. The marker locations may be determined relative to an ideal grid, followed by determining a geometrical transformation model for aligning the wafer, and aligning the wafer responsive to the geometrical transformation model. Related methods and systems are also disclosed.