Modified Photolithography Mask Protrusion for TSV Wafer Resolution
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Solution Overview
Problem
The resolution and accuracy of photolithography processes are limited by light diffraction at the chrome structures of traditional masks, and there is a need for improved lithography methods for Through Silicon Via (TSV) wafers with thinned inner portions and supporting structures at the rim, which require minimizing the gap between the mask and wafer while maintaining mechanical stability.
Innovation Solution
A modified photolithography mask with a protrusion section that allows for a reduced gap between the mask and the thinned inner portion of the wafer, using a round protrusion with a circular groove to facilitate alignment and minimize diffraction, compatible with existing mask aligners, enabling high-resolution lithography without additional costs or complex optical setups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional mask is used with a thinned wafer, then the gap between mask and wafer increases, but the diffraction of light increases and resolution decreases
Solution Approach 1:
The mask is transformed from a flat two-dimensional structure to a three-dimensional structure with a protrusion section that extends toward the wafer. This dimensional change allows the mask to bridge the gap created by the thinned wafer, reducing the effective distance for light propagation and minimizing diffraction while maintaining compatibility with standard mask holders.
Solution Approach 2:
Only a specific portion of the mask (the protrusion section) is modified to extend toward the wafer, while the rest of the mask maintains its original flat structure. This localized modification allows the gap reduction to occur only where needed (over the thinned inner portion) without affecting the overall mask structure or requiring changes to the mask holder system.
2Manufacturing precision
If the gap between mask and wafer is reduced to minimize diffraction, then resolution improves, but mechanical stability of the thin wafer may be compromised
Solution Approach 1:
The mask is divided into two functional sections: a flat mask holder section that maintains mechanical stability and compatibility with the holder, and a protrusion section that extends toward the wafer to reduce the gap. This segmentation allows each part to fulfill its specific function without compromising the other.
Solution Approach 2:
The protrusion section acts as an intermediary structure between the mask holder and the thinned wafer. It provides the necessary support close to the wafer surface to minimize diffraction while the mask holder provides overall mechanical stability, effectively mediating between the conflicting requirements.
3Manufacturing precision
If a modified mask with protrusion is used to reduce gap, then lithography resolution improves, but mask complexity increases
Solution Approach 1:
The protrusion section has a rounded, dome-like shape rather than a sharp or angular form. This curved geometry is easier to manufacture using standard techniques such as spin coating and reflow, and it provides smooth optical surfaces that minimize unwanted diffraction effects while maintaining structural integrity.
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 modified mask setup allows for high-resolution lithography with reduced diffraction, enabling precise feature replication on TSV wafers while maintaining mechanical stability and compatibility with existing production systems.
Implementation Method 1
The light that passes through the mask initiates a photochemical reaction on the resist
Implementation Method 2
The resolution of structures is limited by the diffraction of light at the chrome structures of the mask. The light passing through the chrome structures is bent at these structures. While the incoming light at the mask can be considered as parallel, the light passing through the mask is not parallel anymore and is diverging.
Data Source
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AI summary
A mask for photolithography of a semiconductor wafer is dis- closed. The mask comprises a protrusion section that pro- trudes from a handling section of the mask. An outer shape of the handling section is provided to enable handling by a mask aligner device. The protrusion has a face surface that is provided at a level which is different from a face surface area of the handling section.