Air Gap Interconnect Structure for Substrate Capacitance Reduction
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Solution Overview
Problem
Current semiconductor interconnect technologies, such as copper conductive layers and low-k ILD films, result in significant parasitic capacitances between metal lines and substrates due to close distances, which hinders efficiency and density in microelectronic devices.
Innovation Solution
Integration of air gap structures with interconnect structures using group III nitride layers within dielectric layers to reduce parasitic capacitances by creating a low dielectric constant gap between metal lines and substrates, thereby decreasing capacitance and improving circuit efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper conductive layers and low-k ILD films are used for interconnect, then electrical conductivity is improved, but parasitic capacitance between metal lines and substrate increases
Solution Approach 1:
The patent extracts the problematic dielectric material between the first metal layer and substrate, replacing it with an air gap structure. This removal of the solid dielectric (low-k ILD) and substitution with air (or vacuum) directly reduces the parasitic capacitance while maintaining the electrical conductivity of the copper interconnect layers above.
Solution Approach 2:
The air gap structure functions as a porous or void space between the first metal layer and substrate. This porous region filled with air (dielectric constant ≈1) instead of solid low-k material provides lower parasitic capacitance while preserving the mechanical support and electrical functionality of the interconnect structure.
2Productivity
If metal lines are placed close to substrate, then interconnect density is improved, but parasitic capacitance to substrate increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform dielectric structure: air gaps are introduced specifically in regions where metal lines are positioned close to the substrate, while other regions maintain their original dielectric structure. This localized modification reduces parasitic capacitance only where needed, preserving interconnect density without uniformly increasing device complexity.
3Object-generated harmful factors
If air gap structures are integrated with interconnect, then parasitic capacitance is reduced, but device complexity increases
Solution Approach 1:
The patent merges the air gap formation process with the existing interconnect fabrication sequence. The air gap structure is integrated into the interconnect layer stack, combining the low-capacitance function with the mechanical support and electrical routing functions of the interconnect structure, thereby reducing parasitic capacitance without proportionally increasing overall device complexity.
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
The air gap structures significantly reduce parasitic capacitances by at least 3.9 times, enhancing the efficiency and density of microelectronic device circuitry while maintaining mechanical support for film stacks.
Implementation Method 1
A first metal layer routing incurs a largest parasitic capacitance between the metal transmission lines of the first metal layer and a substrate due to the close distance between the metal lines of the first metal layer and the substrate
Implementation Method 2
an air gap structure that is located below two or more of the plurality of conductive lines. The air gap structure reduces parasitic capacitances between the conductive layer and the substrate
Data Source
AI summary
Embodiments of the invention include a microelectronic device that includes a substrate, at least one dielectric layer on the substrate and a plurality of conductive lines within the at least one dielectric layer. The microelectronic device also includes an air gap structure that is located below two or more of the plurality of conductive lines.