Transparent Wafer Alignment Marks Using Optical Interference
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Solution Overview
Problem
In electronic devices with optical circuits, such as digital cameras and lasers, the use of metal contacts or wires for alignment marks can interfere with transparency, leading to reduced precision and increased costs, especially when bonding transparent wafers where metal alignment marks are not the most effective material.
Innovation Solution
Forming alignment marks on transparent wafers by patterning and removing portions of the wafer material, rather than adding features, to create surfaces that optimize destructive interference for better recognition during alignment, using a reflective chuck and light source for precise location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metal contacts or wires are used for alignment marks, then alignment marks can be formed, but transparency is reduced and precision is reduced
Solution Approach 1:
The patent removes metal contacts or wires from the alignment mark structure entirely. Instead, alignment marks are formed by patterning and removing portions of the transparent wafer material itself, creating surfaces that optimize destructive interference for light. This extraction of the harmful metal component resolves the contradiction by eliminating transparency interference while maintaining alignment precision through optical interference effects.
Solution Approach 2:
The patent changes the physical and optical parameters of the alignment mark by creating surfaces with specific depths and configurations within the transparent wafer material. By controlling the depth, width, and spacing of these patterned surfaces, the patent optimizes destructive interference of light at specific wavelengths, enabling precise alignment detection without metal components. This parameter change transforms the alignment mark from a metal-based reflective structure to a transparent material-based interference structure.
2Ease of manufacture
If metal alignment marks are used on transparent wafers, then alignment marks can be formed, but material costs increase
Solution Approach 1:
The patent uses the same transparent material for both the wafer substrate and the alignment marks. By patterning and removing portions of the transparent wafer material, the alignment marks are created from the homogeneous transparent material itself rather than introducing heterogeneous metal materials. This homogeneity eliminates the need for additional metal materials, reducing material costs while maintaining ease of manufacture through integrated processing.
Solution Approach 2:
The patent merges the alignment mark formation process with the wafer fabrication process. Alignment marks are created by patterning and removing portions of the transparent wafer material during the same manufacturing sequence, rather than as a separate post-processing step requiring metal deposition. This merging of processes reduces both material costs and manufacturing complexity.
3Manufacturing precision
If metal contacts are used for alignment marks, then alignment marks can be formed, but bonding precision is reduced
Solution Approach 1:
The patent extracts metal contacts from the alignment mark structure to eliminate their harmful effect on transparency. By forming alignment marks solely from transparent wafer material through patterning and removal, the patent eliminates metal-induced transparency interference that would otherwise degrade bonding precision in vertically stacked transparent wafer configurations.
Solution Approach 2:
The patent changes the optical parameters of the alignment mark by creating surfaces that optimize destructive interference. These patterned surfaces in the transparent material provide precise alignment references through optical interference effects, enabling accurate bonding alignment without the transparency interference caused by metal contacts.
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 allows for more precise and reliable alignment of transparent wafers, reducing material costs and improving the accuracy of bonding processes by utilizing the natural transparency of the wafers.
Implementation Method 1
create surfaces that optimize destructive interference for better recognition during alignment
Data Source
AI summary
In some embodiments, the present disclosure relates to an integrated chip that includes bonding structure arranged directly between a first substrate and a second substrate. The first substrate includes a first transparent material and a first alignment mark. The first alignment mark is arranged on an outer region of the first substrate and also includes the first transparent material. The first alignment mark is defined by surfaces of the first substrate that are arranged between an uppermost surface of the first substrate and a lowermost surface of the first substrate. The second substrate includes a second alignment mark on an outer region of the second substrate. The second alignment mark directly underlies the first alignment mark, and the bonding structure is arranged directly between the first alignment mark and the second alignment mark.