Crack-Defined Nanogap Fabrication via Stress-Controlled Fracture
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Solution Overview
Problem
Current methods for fabricating electronic nanogaps, such as break junctions and sacrificial spacer layers, face challenges in scalability, precision, and contamination, limiting their application in complex molecular electronic circuits and DNA sequencing devices, particularly in achieving sub-10 nm dimensions and high gap-height to gap-width aspect ratios.
Innovation Solution
A method involving the creation of crack structures on substrates using a sacrificial layer with built-in stress, where a layer of selected materials is patterned to form stress concentration structures, allowing for controlled fracture and precise definition of nanogap widths, enabling the fabrication of sub-3 nm gaps with high aspect ratios and scalability for large-scale production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If break junction approach is used to generate individual atomically sharp electrode tips, then manufacturing precision of sub-1 nm separations is achieved, but productivity is limited to only a few Break junctions per substrate
Solution Approach 1:
The substrate is divided into multiple regions, each containing a sacrificial layer that can be independently removed to form separate nanogaps. This segmentation allows parallel fabrication of many nanogaps simultaneously across the substrate, dramatically increasing productivity while maintaining the precision benefits of controlled fracture mechanisms.
Solution Approach 2:
Sacrificial layers are pre-deposited in specific patterns before electrode fabrication. These pre-positioned sacrificial structures serve as templates that guide subsequent electrode formation and define the exact locations where nanogaps will form, enabling high-throughput parallel fabrication with precise spatial control.
2Manufacturing precision
If masking layers with etching processes are used to define nanogap dimensions, then manufacturing precision of nanogap width is attempted, but device complexity increases and scalability is limited
Solution Approach 1:
The complex masking and etching processes are replaced by extracting/removing sacrificial layers through selective dissolution. This extraction approach simplifies the fabrication process by eliminating multiple patterning and etching steps, reducing device complexity while maintaining precise nanogap dimension control through the sacrificial layer thickness.
Solution Approach 2:
Mechanical and chemical etching processes are replaced with chemical dissolution of sacrificial layers. This substitution eliminates the need for complex masking layers and anisotropic etching, significantly reducing fabrication process complexity while achieving comparable or superior precision through controlled sacrificial material removal.
3Manufacturing precision
If sacrificial spacer layers are used to define gap widths, then manufacturing precision of gap width is achieved, but productivity is limited and contamination risks increase
Solution Approach 1:
The substrate is divided into multiple independent regions, each with its own sacrificial layer that can be simultaneously removed to create multiple nanogaps in parallel. This segmentation enables high productivity by fabricating many nanogaps concurrently while maintaining precise gap width control through uniform sacrificial layer deposition across the entire substrate.
Solution Approach 2:
A single sacrificial layer deposition process creates identical template structures across the entire substrate, which are then simultaneously removed to produce multiple identical nanogaps. This copying approach enables scalable production of many identical nanogap devices with consistent dimensions, dramatically increasing productivity while maintaining precision.
4Ease of manufacture
If etching of sacrificial layer is performed to form nanogaps, then nanogap structure is created, but harmful factors such as etch-residue contamination occur
Solution Approach 1:
Instead of etching away sacrificial material, the sacrificial layers are extracted through selective dissolution or removal processes. This extraction approach eliminates etch-residue contamination while still achieving precise nanogap formation, as the sacrificial layers are completely removed without leaving behind harmful byproducts that would contaminate the electrode surfaces.
Solution Approach 2:
The potential harm of sacrificial material removal is converted into a benefit by using sacrificial layers made of materials that can be selectively removed without contamination. The removal process itself becomes beneficial by leaving clean surfaces ideal for electron transport, transforming what could be a contamination source into a surface cleaning and preparation mechanism.
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 allows for the production of millions of crack structures with tailored gap widths between sub-2 nm and 100 nm, achieving high aspect ratios and clean, contaminant-free surfaces, suitable for integration with CMOS circuits and various materials, enabling efficient electron tunneling and sequencing applications.
Implementation Method 1
The layer of selected material(s) is patterned... to provide a bridge, preferably elongated, having one or several stress concentration structures, preferably a notch or notches
Implementation Method 2
a layer of one or more selected materials is provided on the sacrificial layer, such that there will be a built-in stress in the material
Implementation Method 3
Electronic nanogaps feature rich physics... applications using electron transport mechanisms such as tunnel junctions
Data Source
AI summary
Disclosed is a method of making a crack structure on a substrate, the crack structure being usable as a tunnelling junction structure in a nanogap device, including the controlled fracture or release of a patterned layer under built-in stress, thereby forming elements separated by nanogaps or crack-junctions. The width of the crack-defined nanogap is controlled by locally release-etching the film at a notched bridge patterned in the film. The built-in stress contributes to forming the crack and defining of the width of the crack-defined nanogap. Further, by design of the length of the bridge in a range between sub-μπι to >25μαι, the separation between the elements, defined by the width of the crack-defined nanogaps, can be controlled for each individual crack structure from <2 nm to >100 nm. The nanogaps can be used for tunneling devices in combination with nanopores for DNA, RNA or peptides sequencing.