Angled Deposition Shadow Walls for Isolated Nanowire Contacts
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Solution Overview
Problem
Conventional fabrication processes for semiconductor nanowires involve detrimental post-fabrication steps such as etching and lithography, which can damage the devices and affect their performance, particularly in hybrid semiconductor-superconductor structures like InSb/Al.
Innovation Solution
A method involving angled deposition using shadow walls with gaps and a vertical hard mask template to form electrically isolated conducting elements like gates, leads, and bond pads directly on the nanowires, eliminating the need for post-fabrication etching and lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional post-fabrication steps (etching and lithography) are used to form conducting elements, then electrical contacts and gates can be created, but device performance deteriorates due to material damage and surface potential fluctuations
Solution Approach 1:
The shadow wall structure is formed before the deposition of conducting materials. By pre-positioning these walls, the patent enables selective area deposition without requiring subsequent etching or lithography steps, thus avoiding damage to the nanowire devices while still achieving the necessary electrical contacts and gates
Solution Approach 2:
The shadow wall structure acts as an intermediary element that enables selective deposition. These walls are positioned to cast shadows during angled deposition, allowing conducting materials to be deposited only in desired areas without direct contact or damage to the underlying nanowire structures
2Device complexity
If standard lithography and post-fabrication steps are performed, then complex nanoelectronics can be created, but harmful effects from adsorbates and surface potential fluctuations increase
Solution Approach 1:
The shadow wall structure is formed in advance before any conducting material deposition. This preliminary structure enables complex nanoelectronics to be created through selective area deposition alone, eliminating the need for harmful lithography and etching steps that would otherwise be required to achieve such complexity
Solution Approach 2:
The patent extracts and removes the harmful post-fabrication steps (etching and lithography) from the fabrication process. By using shadow walls with angled deposition, only the necessary deposition steps remain, taking out the problematic steps that cause surface potential fluctuations and adsorbate-related damage
3Reliability
If fewer post-fabrication steps are used, then device damage is reduced, but the ability to form electrically isolated conducting elements becomes more difficult
Solution Approach 1:
The shadow wall structure exploits asymmetric geometry to achieve electrical isolation. By positioning walls at specific angles and heights relative to the deposition direction, the structure casts shadows that prevent conducting material from bridging between adjacent regions, thereby achieving precise electrical isolation without requiring additional patterning steps
Solution Approach 2:
The patent transitions from two-dimensional planar patterning to three-dimensional shadow casting. By introducing vertical shadow walls and using angled deposition, the system achieves precise spatial control and electrical isolation in three dimensions, eliminating the need for complex multi-step lithography processes
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 device performance by reducing material damage and maintaining high-quality semiconductor-superconductor interfaces, allowing for the formation of complex nanoelectronics without detrimental post-fabrication steps.
Implementation Method 1
the shadow wall structure is arranged to cast a shadow in the deposition process, leaving areas where the conductor is not deposited
Implementation Method 2
depositing an upper conducting layer over the substrate by angled deposition of a conductor such as a metal. E.g. this may be performed using vapour deposition
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
A method of fabricating a device (12), comprising: forming portions of electronic circuitry and a shadow wall structure (13) over a substrate, and subsequently depositing a conducting layer (5) over the substrate by angled deposition of a conducting material in at least a first deposition direction at an acute angle relative to the plane of the substrate. The shadow wall structure is arranged to cast a shadow in the deposition, leaving areas where the conducting material is not deposited. The shadow wall structure comprises one or more gaps (15) each shorter than a shadow length of a respective part of the shadow wall structure casting the shadow into the gap, to prevent the conducting material forming in the gaps and to thereby create regions of said upper conducting layer that are electrically isolated from one another. These are arranged to form conducting elements for applying signals to, and/or receiving signals from, the electronic circuitry.