Photomask Alignment Marks and Vacuum Recess for Substrate Positioning
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Solution Overview
Problem
Existing methods for aligning conductive patterns on both faces of flexible printed circuit substrates face challenges in achieving high positional accuracy due to issues like positional displacement, light scattering from concavities and convexities, and processing variations, which hinder precise alignment between photomasks and substrates.
Innovation Solution
A photomask system with distinct alignment marks on each face, utilizing a recessed portion with suction trenches and holes for precise alignment and retention, and a control unit to manage pressure for stable substrate positioning during exposure, allowing for improved alignment accuracy between photomasks and substrates on both faces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks are provided on both faces of the photomask for aligning with substrate side marks, then alignment accuracy between photomasks and substrates on both faces is improved, but device complexity increases due to additional alignment marks and regions
Solution Approach 1:
The photomask is segmented into distinct functional regions: a first region with a drawing pattern for exposure on one face, and a second region with alignment marks on both faces. This segmentation allows the alignment function to be separated from the exposure function, enabling high-precision alignment without interfering with the drawing pattern exposure process.
Solution Approach 2:
The invention extends the alignment functionality from a single face to both faces of the photomask by providing alignment marks in a second region that is transparent to light. This dimensional extension allows alignment operations on both the front and rear faces of the substrate simultaneously, improving overall alignment accuracy without adding complexity to the exposure process.
2Stability of the object's composition
If a recessed portion with suction holes is provided in the photomask for retaining the substrate, then substrate positioning stability is improved, but manufacturing complexity increases
Solution Approach 1:
The photomask incorporates a recessed portion with suction holes that utilize vacuum suction to retain the substrate during alignment and exposure. This pneumatic mechanism provides stable substrate positioning by creating a secure hold through negative pressure, preventing substrate displacement while maintaining ease of substrate loading and removal.
3Illumination intensity
If the first region of the photomask is made transparent to light for exposure, then exposure quality is improved, but alignment mark visibility for the first alignment mark may be reduced
Solution Approach 1:
The photomask is divided into functionally distinct regions: the first region with the drawing pattern that requires high light transmission for exposure quality, and the second region with alignment marks that requires sufficient contrast for visibility. This segmentation allows each region to be optimized for its specific function without compromising the other.
Solution Approach 2:
Different regions of the photomask are assigned different optical properties: the first region is made transparent to light to ensure high exposure quality, while the second region containing alignment marks is designed with appropriate light absorption or contrast enhancement to ensure visibility. This local differentiation of properties allows both exposure quality and alignment mark visibility to be optimized simultaneously.
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 solution enhances alignment accuracy between photomasks and substrates, reducing positional displacement and improving the precision of conductive pattern alignment on multi-layer substrates, thereby supporting denser and more accurate circuit board manufacturing.
Implementation Method 1
a recessed portion provided in the one face, and when negative pressure is applied via a pressure generating means, the recessed portion applies the negative pressure to an opposing face of the substrate which opposes the one face
Data Source
AI summary
An exposure apparatus may include a first moving mechanism moving by driving a first drive source a first photomask; a second moving mechanism moving by driving a second drive source a second photomask; an imaging means for imaging a first alignment mark formed on the first photomask and a substrate side mark formed on the substrate and imaging a second alignment mark formed on the first photomask and a third alignment mark formed on the second photomask; and a control unit, wherein the control unit controls the first drive source so that alignment between the first alignment mark and the substrate side mark is performed based on results of imaging these marks, and the control unit controls the second drive source so that alignment between the second alignment mark and the third alignment mark is performed based on results of imaging these marks.