Composite Wafer Alignment Mark for Precise Optical Orientation
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Solution Overview
Problem
Existing semiconductor wafers face challenges in precise alignment during manufacturing, particularly in process control monitoring and die singulation, due to insufficient optical contrast and inaccuracy in aligning probe needles with existing alignment marks.
Innovation Solution
A composite alignment mark is introduced on the semiconductor wafer, comprising two portions of differing materials, one formed from a metal or alloy and the other from an electrically insulating material, providing sufficient optical contrast to ensure precise alignment and orientation in three-dimensional space, which can be visualized optically or using alignment cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-material alignment mark is used on the semiconductor wafer, then the alignment mark can be formed with simple structure and fabrication process, but the optical contrast is insufficient making it difficult to achieve precise alignment and orientation
Solution Approach 1:
The alignment mark is constructed using composite materials consisting of a first material layer (such as metal or alloy) and a second material layer (such as electrically insulating material) with different optical properties. This composite structure provides sufficient optical contrast for precise alignment while maintaining a relatively simple fabrication process that can be integrated into existing semiconductor manufacturing workflows.
2Measurement precision
If existing alignment marks are used for process control monitoring, then the fabrication process can be completed, but the probe needles cannot be accurately placed on the auxiliary structures due to insufficient alignment precision
Solution Approach 1:
The patent replaces mechanical alignment methods with optical alignment methods by creating alignment marks with high optical contrast. The composite material structure enables optical detection systems to accurately locate the alignment mark, which in turn enables precise positioning of probe needles for process control monitoring, thereby improving both measurement precision and process reliability.
3Measurement precision
If a composite alignment mark with multiple materials is used, then sufficient optical contrast is achieved for precise alignment, but the fabrication process becomes more complex with additional deposition and structuring steps
Solution Approach 1:
The alignment mark is segmented into distinct material layers (first material and second material) that can be deposited and structured separately. This segmentation allows each layer to be optimized for its specific function while enabling the use of standard semiconductor fabrication techniques such as sequential deposition and photolithography, thereby balancing enhanced detectability with manufacturing feasibility.
Data Source
Figure 1
Figure 2A~3B
Figure 4~5D
AI summary
In an embodiment, a semiconductor wafer (10) comprises a front surface (11), a plurality of active component positions (12) and at least one composite alignment mark (14) arranged on the front surface (11) and indicating a unique orientation of the semiconductor wafer (10). The composite alignment mark (14) comprises a first portion (17) that comprises at least one raised section (20, 24) formed of a first material and a second portion (18) that is positioned laterally adjacent the first portion (17). The second portion (18) comprises at least one raised section (25, 26) formed of a second material that is different form the first material.