Mushroom-Type Interconnect with Micro-Air Bridges
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Solution Overview
Problem
The challenge in forming high-density interconnects in solid-state electronic displays is the difficulty in creating fine-scale, planar interconnects that can bridge over multiple circuit elements independently, limited by conventional lithographic techniques and increased parasitic capacitance, especially when dealing with obstacles like electrical contacts.
Innovation Solution
The implementation of a 'mushroom'-type interconnect structure with micro-air bridges, where sections of the interconnect omit the stalk to bridge over obstacles, utilizing electron beam lithography to create narrow stalks and wider caps, allowing for low-resistivity connections without physical contact with the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithographic techniques are used to create interconnects, then manufacturing process is simple, but feature size is limited by wavelength of light
Solution Approach 1:
The patent replaces conventional photolithographic techniques with electron beam lithography to achieve finer feature sizes. The electron beam system uses a focused beam of electrons to pattern the resist, enabling sub-100nm feature sizes that are unattainable with optical methods due to diffraction limits. This substitution of the lithography mechanism directly resolves the contradiction between manufacturing simplicity and feature size precision.
2Productivity
If bridging interconnects are formed over obstacles, then interconnect density increases, but parasitic capacitance increases
Solution Approach 1:
The patent introduces air bridges where sections of the interconnect are suspended over obstacles without physical contact, creating an air gap that eliminates parasitic capacitance to underlying structures. The air gap acts as an electrical insulator while allowing the interconnect to bridge obstacles, thus maintaining high interconnect density without the harmful capacitance effect that would result from direct contact bridging.
Solution Approach 2:
The patent transitions from planar interconnect geometry to three-dimensional suspended structures. By lifting portions of the interconnect into the air gap above obstacles, the design adds a vertical dimension to the interconnect path, enabling it to clear obstacles without increasing lateral density or creating capacitive coupling to underlying layers.
3Ease of operation
If air bridge interconnects are fabricated using sacrificial layers, then air bridges can be formed, but surface planarity is lost
Solution Approach 1:
The patent extracts and removes the sacrificial layer entirely from the final structure, leaving only the air bridge interconnect suspended over the obstacle. By completely removing the sacrificial material after it has served its purpose of defining the air gap space, the design achieves air bridge formation without the residual structures that would compromise surface planarity.
Solution Approach 2:
The sacrificial layer is deposited and patterned in advance to define the precise location and dimensions of the air gap before the interconnect is formed. This preliminary action allows the air bridge to be created with accurate geometry while maintaining the ability to restore surface planarity through subsequent processing steps that remove the sacrificial material.
4Productivity
If interconnect width is reduced to increase density, then interconnect density increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs electron beam lithography instead of photolithography to achieve the required manufacturing precision for sub-100nm interconnect features. The electron beam system provides superior resolution and positioning accuracy, enabling precise control of interconnect dimensions at the scale required for high-density interconnect architectures without compromising feature size control.
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 enables the formation of fine-scale, low-resistivity interconnects with reduced parasitic capacitance and planar morphology, effectively bridging over obstacles without contact, enhancing the density and efficiency of interconnects in electronic circuits.
Implementation Method 1
A first electron beam that can penetrate all resist layers on a substrate is directed along a path on the substrate but shielded for at least a portion of the path. A second electron beam that cannot penetrate all of the resist layers on the substrate is directed along the entire path without being shielded.
Data Source
AI summary
Structures of and methods for fabricating fine-scale interconnects are disclosed. A “mushroom”-type structure with a narrow stalk supporting a wider cap can be used for fine-scale interconnects with widths on the scale of hundreds of nanometers that have low resistivity. Micro-air bridges can be introduced by omitting the stalk in sections of the interconnect, allowing the interconnect to bridge over obstacles.