Asymmetric Double Dolan Bridge Fabrication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The fabrication of Josephson Junctions using shadow mask lithography techniques faces challenges with step coverage and material deposition, leading to issues like knob formation and metal line edge roughness due to the standard bilayer resist configuration, which affects the quality of Dolan Bridge structures.
Innovation Solution
A double Dolan Bridge structure is fabricated using a triple stack resist configuration with asymmetrically arranged metallic layers, where no more than two of the three layers are stacked on each other, and a second conductor is deposited in a longitudinal direction with portions on either side of the first conductor, improving step coverage and reducing disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard bilayer resist configuration is used for shadow mask lithography, then the fabrication process is simpler, but step coverage problems and knob formation occur leading to poor junction quality
Solution Approach 1:
The resist configuration is segmented into three distinct layers (first resist layer, second resist layer, and third resist layer) instead of using a standard bilayer configuration. Each layer serves a specific function in the shadow mask lithography process, with the third layer having a different pattern than the first two layers, enabling precise control over material deposition and eliminating step coverage problems.
2Manufacturing precision
If metallic layers are stacked on each other in standard configuration, then the junction structure is formed, but metal line edge roughness and disruptions occur
Solution Approach 1:
The metallic layers are arranged in an asymmetric configuration where the first and second metallic layers are offset relative to each other, and the third metallic layer has a different pattern than the first two layers. This asymmetric arrangement prevents direct stacking of all layers, eliminating knob formation and metal line edge roughness while maintaining proper junction structure.
3Reliability
If shadow mask lithography is used with standard configuration, then the process is straightforward, but knob formation and metal line edge roughness degrade junction quality
Solution Approach 1:
The first and second resist layers are applied with the same pattern before the third resist layer is applied with a different pattern. This preliminary action of establishing the base pattern allows the subsequent asymmetric metal layer deposition to proceed without knob formation, ensuring reliable junctions from the outset.
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 enhances the quality of Josephson Junctions by reducing step coverage to a single layer, minimizing knob formation, and improving metal line edge roughness, resulting in smoother and more reliable junctions.
Implementation Method 1
The fabrication of Josephson Junctions (JJs) can use techniques that include a shadow mask lithographical approach. An evaporation mask is suspended above a substrate to apply layers of material on the substrate. Depending on an evaporation angle, the shadow image is projected onto different positions of the substrate.
Implementation Method 2
An evaporation mask is suspended above a substrate to apply layers of material on the substrate. After evaporation, the shadow mask is removed leaving behind the deposited metal.
Data Source
AI summary
A double Dolan Bridge structure includes two Dolan Bridges arranged side-by-side to form a Josephson Junction. Each Dolan Bridge includes a substrate, and a triple stack resist configuration including three layers of material arranged on the substrate. An asymmetrically arranged junction including at least three metallic layers is arranged on the substrate in a stack having no more than two of the least three metallic stacked on each other.