ALD Reactor Flow-Through Geometry for Porous Substrates
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Solution Overview
Problem
Conventional ALD reactors face challenges in uniformly coating high surface area, porous substrates like capillary glass arrays due to non-uniform precursor flux and trapping effects, leading to non-uniform coatings and increased fabrication costs.
Innovation Solution
An improved ALD reactor system with a showerhead inlet and outlet section to ensure a uniform precursor flux and flow-through geometry, forcing precursor reactants and carrier gas through the substrate's pores, maintaining perpendicular flow to minimize deposition nonuniformities and enhance purging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cross-flow ALD reactors are used to coat porous substrates, then the substrate can be processed, but non-uniform precursor flux leads to non-uniform coatings along the flow axis
Solution Approach 1:
The patent inverts the conventional cross-flow geometry by implementing a flow-through geometry where the substrate is positioned perpendicular to the gas flow direction. This inversion ensures that precursor flux is uniform across the substrate surface, eliminating the non-uniform coating problem that occurs in conventional cross-flow reactors where upstream portions receive higher precursor flux than downstream portions.
2Manufacturing precision
If purge gas flow is normal to the axis of pores in porous substrates, then purging can be performed, but H2O diffuses back into downstream pores and physisorbs, creating a trapping effect that increases coating non-uniformity
Solution Approach 1:
The patent inverts the purge gas flow direction relative to the pore axis. Instead of flowing normal to the pore axis as in conventional reactors, the purge gas flows parallel to the pore axis in the flow-through geometry. This directional change prevents H2O from diffusing back into downstream pores, eliminating the trapping effect that causes coating non-uniformity.
3Manufacturing precision
If showerhead inlet and outlet sections are implemented to maintain uniform flow perpendicular to substrate, then deposition uniformity improves, but device complexity increases
Solution Approach 1:
The reactor is segmented into distinct functional sections: a showerhead inlet section that distributes precursor uniformly across the substrate surface, the substrate processing zone with flow-through geometry, and a showerhead outlet section that maintains uniform flow perpendicular to the substrate. This segmentation allows each section to be optimized for its specific function, achieving uniform deposition while managing overall system complexity through modular design.
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 system achieves improved thickness and compositional uniformity of deposited layers on porous substrates, reducing non-uniformity and fabrication costs by maintaining a consistent precursor flux and effective purging, even with high aspect ratio substrates.
Implementation Method 1
showerhead inlet section which provides a uniform flux of precursor reactants across a surface of the porous substrate
Implementation Method 2
precursor reactants and carrier gas are forced to flow-through pores of the porous substrate
Implementation Method 3
precursor reactants and carrier gas are forced to flow-through pores of the porous substrate
Implementation Method 4
molecules such as H2O which physisorb strongly to surfaces can continue to outgas for long periods of time
Implementation Method 5
ALD/CVD deposition for coating porous substrates
Data Source
AI summary
A system and method for improved atomic layer deposition. The system includes a top showerhead plate, a substrate and a bottom showerhead plate. The substrate includes a porous microchannel plate and a substrate holder is positioned in the system to insure flow-through of the gas precursor.