Liquid-Based Masking Layer for Conformal Wet Etching
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Solution Overview
Problem
Conventional masking layers for wet etching processes are limited by their requirement for clean substrates, susceptibility to detachment during substrate deformation, inability to adhere to non-flat surfaces, and the need for thermal procedures, which increases time and cost, and restricts their application to flat surfaces and 3D substrates.
Innovation Solution
A liquid-based masking layer is fabricated by forming a porous surface on a substrate and filling its pores with a filling liquid, which is resistant to etchants and can be applied to non-flat surfaces, allowing for efficient patterning without the need for thermal procedures, and can be reused.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional masking layers (photo-resist or vapor-deposited) are used, then the substrate surface can be protected from etching, but the masking layer requires clean substrates and clean environments, and any foreign material on the surface alters adhesion
Solution Approach 1:
The masking layer is designed as a porous coating that can accommodate foreign material on the substrate surface. The porous structure allows the masking layer to conform to the actual surface topology, maintaining adhesion even when foreign material is present. The pores can also be filled with liquid etchant, enabling the etching process to proceed through the masking layer in controlled regions.
Solution Approach 2:
The invention changes the physical and chemical parameters of the masking layer by applying it in liquid form and allowing it to dry or cure in place. This liquid-based approach enables better wetting and adhesion to substrates with foreign material, compared to vapor-phase deposition which requires extremely clean surfaces. The masking layer can be applied as a slurry or suspension that penetrates around foreign material particles.
2Manufacturing precision
If thin masking layers are used, then the etching precision can be improved, but the masking layer easily detaches from the substrate when the substrate is subjected to bending or deformation
Solution Approach 1:
The porous structure of the masking layer provides mechanical compliance that allows thin layers to deform with the substrate without detaching. The pores can compress and expand during bending, distributing mechanical stresses and preventing catastrophic failure of the thin masking layer. This enables use of very thin masking layers for high precision while maintaining adhesion during substrate deformation.
Solution Approach 2:
The masking layer is formulated as a composite material combining a porous solid matrix with liquid or gel components. This composite structure provides both the mechanical strength needed for adhesion during deformation and the flexibility to maintain thin profile for precision etching. The liquid/gel phase can flow to accommodate deformation while the solid matrix maintains structural integrity.
3Area of stationary object
If conventional masking layers are used, then flat surfaces can be effectively masked, but non-flat surfaces and enclosed passages cannot be accessed
Solution Approach 1:
The masking layer is applied in liquid form that can flow into enclosed passages, non-flat surfaces, and complex 3D geometries. The liquid precursor can be delivered via capillary action, pressure-driven flow, or dip-coating methods that ensure complete coverage of complex surfaces. After application, the liquid masks converts to solid form, creating a conformal coating that adheres to the complex geometry.
Solution Approach 2:
The invention utilizes parameter changes by applying the masking layer in a liquid state with low viscosity for easy penetration into complex geometries, then transforming it to a solid state for structural integrity. This phase change enables the masking material to flow into and coat non-flat surfaces and enclosed passages, then solidify to provide the necessary mechanical properties for the etching process.
4Reliability
If thermal procedures are used to solidify masking layers, then suitable hydrophobicity and decreased residual stress are achieved, but time and cost increase
Solution Approach 1:
The invention replaces thermal procedures with chemical or ambient drying processes to solidify the masking layer. Instead of using heat to evaporate solvents and cure the masking material, the process relies on ambient evaporation, capillary action, or chemical crosslinking at room temperature. This substitution eliminates the need for thermal equipment and processing time, reducing both cost and time while achieving the necessary solidification and hydrophobicity.
Solution Approach 2:
The masking layer formulation is designed to self-solidify through ambient drying or spontaneous chemical reactions without requiring external thermal energy input. The liquid precursor contains components that naturally evaporate or crosslink at room temperature, allowing the masking layer to complete its solidification process autonomously. This self-service approach eliminates the need for controlled thermal processing equipment and procedures.
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 liquid-based masking layer effectively protects substrate areas from etching, maintains adhesion during the process, and can be easily removed, reducing costs and expanding the applicability to complex geometries, while ensuring efficient and reliable patterning.
Implementation Method 1
forming a liquid-based masking layer by filling the pores of the porous preliminary mask with a filling liquid
Data Source
AI summary
A method of fabricating a liquid-based masking layer for a wet etching process, is disclosed. The method comprises forming a coated solid substrate by coating a solid substrate with a coating; forming a preliminary masking layer by removing parts of the coating which are not included in a pattern; depositing a porous surface on the preliminary mask to obtain a porous preliminary mask; forming a liquid-based masking layer by filling the pores of the porous preliminary mask with a filling liquid; and applying an etchant to a surface of the solid substrate and the liquid-based masking layer, etching parts of the substrate that are not covered with the liquid-based masking layer.