Shadow Evaporation Mask for Tunnel Junction Uniformity
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Solution Overview
Problem
Current double-angle electron-beam evaporation techniques for fabricating Josephson junctions result in nanoscale misalignments and variations in junction sizes due to conical shapes of evaporated metal flows, leading to non-uniformities over large wafer areas.
Innovation Solution
The use of shadow evaporation masks with patterned openings of the same size and configuration enables double-angle evaporation of junction electrodes, ensuring uniform area of tunnel junction devices across the substrate despite changes in deposition angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If double-angle electron-beam evaporation techniques are used to fabricate Josephson junctions, then junction electrodes can be formed with overlapping areas, but conical shapes of evaporated metal flows cause nanoscale misalignments and variations in junction sizes over large wafer areas
Solution Approach 1:
The shadow evaporation mask introduces local geometric variations in the mask opening shapes to compensate for the global conical evaporation pattern. Each mask opening is specifically designed with local dimensional adjustments that counteract the position-dependent deposition angle variations, ensuring uniform junction electrode overlap areas across the entire wafer surface.
Solution Approach 2:
The mask design preemptively compensates for the known conical evaporation pattern by incorporating pre-calculated geometric corrections into the mask opening shapes. This preliminary anti-action counteracts the anticipated misalignments and size variations before the evaporation process occurs, ensuring uniform junction formation across the wafer.
2Manufacturing precision
If shadow evaporation masks with position-dependent opening shapes are used to compensate for conical evaporation patterns, then junction size uniformity can be achieved, but mask design and fabrication complexity increases
Solution Approach 1:
The mask design systematically varies the opening shape parameters (dimensions, angles, positions) as a function of location on the wafer to compensate for the conical evaporation pattern. By establishing mathematical relationships between mask opening parameters and wafer position, the design process becomes more structured and less arbitrary, reducing overall complexity despite the position-dependent variations.
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 fabrication of tunnel junction devices with invariant overlapping areas, achieving uniformity and reliability over large wafer areas, which is essential for scaling up quantum processor capabilities.
Implementation Method 1
double angle evaporation process to form a plurality of tunnel junction devices
Data Source
AI summary
A method comprises forming a shadow evaporation mask on a substrate, and utilizing the shadow evaporation mask to perform a double angle evaporation process to form a plurality of tunnel junction devices in each of the different regions of the substrate. The shadow evaporation mask comprises a plurality of patterned openings in different regions of the substrate, wherein each of the patterned openings comprises a same size and shaped opening. The tunnel junction devices each comprise a first metal layer and a second metal layer having an overlapping area, wherein the overlapping areas of the tunnel junction devices are invariant over the different regions of the substrate.