Micropore Membrane Fabrication Using Pillar Templates
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Solution Overview
Problem
Standard semiconductor manufacturing techniques are inadequate for producing large surface area microporous membranes with desirable properties, particularly in achieving uniform pore sizes and high aspect ratio vias in polymeric materials.
Innovation Solution
The use of a pillar template in combination with photolithographic and etching techniques to create porous polymeric membranes, where the polymer layer has pores with a tapered profile that opens wider at the top surface and a substantially vertical profile at the bottom, allowing for greater variability and control in pore size and etching uniformity, and the option of a tear prevention ring to prevent membrane tearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional semiconductor manufacturing techniques are used to make membranes, then manufacturing precision can be achieved, but large surface area membranes with desirable properties cannot be produced
Solution Approach 1:
The patent applies preliminary action by first forming a layer of spherical beads (polystyrene or silica) on the substrate before depositing the polymeric material. These beads serve as pre-positioned templates that define the pore locations and sizes. The etching process then removes these beads to create uniform pores. This preliminary structuring enables large area membranes to achieve uniform pore characteristics that conventional direct etching cannot provide.
2Length of moving object
If high aspect ratio vias are etched in polymeric materials, then deep pores can be created, but etching uniformity and control are lost
Solution Approach 1:
The patent uses an intermediary etching process where spherical beads embedded in the polymeric layer serve as self-aligned templates. The etchant selectively removes material around these beads, creating uniform cylindrical pores. The beads act as physical guides that maintain etching uniformity throughout the polymeric layer thickness, enabling deep pores with consistent dimensions that would otherwise be impossible to achieve through direct etching.
3Manufacturing precision
If pore openings are made smaller to prevent clogging, then filtration precision improves, but manufacturing variability increases
Solution Approach 1:
The patent changes the fundamental parameter of pore formation from direct etching to template-based removal. By using spherical beads of controlled size (which can be precisely manufactured) as templates, the pore dimensions are determined by the bead size rather than etching parameters. This parameter change decouples pore size control from etching variability, enabling precise small pore openings with high manufacturing reliability and reduced variability.
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 approach enables the production of membranes with reproducible exit dimensions, faster etch times, and improved controllability of pore geometry, overcoming challenges in etching high aspect ratio vias and preventing clogging, while allowing for larger membrane surface areas and increased manufacturing throughput.
Implementation Method 1
The pillar template defines a bottom surface of the membrane and a top surface of the membrane, with pores having tapered profiles opening wider at the top and substantially vertical profiles at the bottom
Implementation Method 2
patterning the hard mask layer to define a plurality of openings in the hard mask layer that are aligned with each pillar corresponding to each pore
Implementation Method 3
removing the polymer layer until the optional release layer over each pillar or the pillar in the case of no release layer corresponding to each pore is exposed through a first opening in the polymer layer
Data Source
AI summary
Porous liquid-filtering membranes having a repeatable distribution of pores of a small dimension are provided, as well as pillar templates that are used to produce such liquid filtering membranes. Also disclosed are methods of making and using the pillar templates to make porous liquid filtering membranes.