Wafer Alignment Marks for Reduced Solvent Splash and Faster Positioning
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Solution Overview
Problem
The existing wafer notch alignment method in integrated circuit fabrication is prone to random solvent splash during edge cleaning, leading to defects and yield penalties, and can cause arcing effects during etching due to the need for 360° rotation.
Innovation Solution
The implementation of wafer alignment marks on the backside of the wafer, evenly distributed at specific angles, which are detected using a light source and CCD sensor to reduce solvent splash impact and align the wafer efficiently, allowing for reduced rotation time and improved yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wafer notch is used for alignment, then the wafer can be aligned during fabrication, but random solvent splash occurs during edge cleaning causing defects and yield penalty
Solution Approach 1:
The alignment function is extracted from the wafer edge notch and relocated to discrete alignment marks positioned on the wafer surface. This removes the vulnerability of the edge notch to solvent splash while preserving the alignment capability through optically detectable marks that can be positioned away from solvent exposure zones.
Solution Approach 2:
Optical alignment marks serve as an intermediary between the wafer positioning system and the alignment detection system. These marks enable precise alignment detection without requiring physical contact or exposure of critical wafer features to solvent during the cleaning process.
2Measurement precision
If a wafer notch is used for alignment, then alignment can be achieved, but arcing effect occurs during etching process
Solution Approach 1:
The alignment function is extracted from the wafer edge notch and relocated to discrete alignment marks positioned on the wafer surface. This removes the vulnerability of the edge notch to solvent splash while preserving the alignment capability through optically detectable marks that can be positioned away from solvent exposure zones.
3Measurement precision
If 360° rotation is performed to find wafer notch, then alignment can be achieved, but alignment time is increased
Solution Approach 1:
Multiple alignment marks are pre-positioned at known angular intervals (e.g., 0°, 90°, 180°, 270°) around the wafer periphery. This preliminary arrangement allows the alignment system to detect marks within a limited rotation range rather than requiring a full 360° search, significantly reducing alignment time while maintaining precision.
Solution Approach 2:
The continuous 360° rotation search space is segmented into discrete angular sectors by placing alignment marks at specific intervals. This segmentation allows the alignment system to search within smaller angular ranges, reducing the time required to locate alignment marks while maintaining accurate positioning capability.
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
The wafer alignment marks significantly reduce solvent splash issues and align the wafer 75% faster than traditional notch-based methods, enhancing process yield and minimizing defects.
Implementation Method 1
a light detection device configured to detect reflected light intensity from the wafer to locate at least one wafer alignment mark
Data Source
AI summary
A wafer alignment apparatus includes a light source, a light detection device, and a rotation device configured to rotate a wafer. The light source is configured to provide a light directed to the wafer. The light detection device is configured to detect reflected light intensity from the wafer to locate at least one wafer alignment mark of wafer alignment marks separated by a plurality of angles. At least two of those angles are equal.