Air Gap Sealing in Semiconductor Interconnects
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Solution Overview
Problem
As semiconductor device sizes decrease, the reduced distance between interconnect lines leads to increased parasitic capacitance, affecting the performance of integrated circuits by increasing the RC constant and reducing circuit speed.
Innovation Solution
A structure is developed where an air gap with a bottle-shaped cross-section is formed between adjacent metal elements, sealed by a porous ultra-low-dielectric-constant (ULK) layer that does not enter the air gap, maintaining its volume and reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the device size is reduced, then the integration is improved, but the parasitic capacitance between interconnect lines increases
Solution Approach 1:
The patent extracts the harmful dielectric material between adjacent metal elements and replaces it with air gaps. By removing the solid dielectric layer from the regions between metal interconnects, the parasitic capacitance is reduced while maintaining the compact device structure needed for high integration.
Solution Approach 2:
The patent introduces porous dielectric layers with air gaps between metal elements. The porous structure allows for reduced effective dielectric constant between interconnect lines, thereby lowering parasitic capacitance while still providing electrical insulation and maintaining structural integrity for high-density integration.
2Object-affected harmful factors
If the air gap volume is increased, then the parasitic capacitance is reduced, but the dielectric layer may enter and consume the air gap volume
Solution Approach 1:
The patent applies preliminary action by forming a sealing dielectric layer over the air gaps before subsequent dielectric deposition processes. This sealing layer prevents the entry and consumption of air gap volume by later-deposited dielectric materials, thereby preserving the air gap volume needed for low parasitic capacitance.
Solution Approach 2:
The patent introduces a sealing dielectric layer as an intermediary between the air gaps and subsequent dielectric layers. This intermediary layer acts as a barrier that prevents the harmful effect of dielectric material intrusion into the air gaps, while allowing the air gaps to maintain their volume for capacitance reduction.
3Volume of moving object
If a sealing dielectric layer is formed over the air gap, then the air gap volume is preserved, but the parasitic capacitance reduction is limited
Solution Approach 1:
The patent applies local quality by using different dielectric materials with different dielectric constants in different regions. The sealing layer uses a first dielectric material with a lower dielectric constant, while the inter-layer dielectric uses a second dielectric material. This local variation in dielectric properties maximizes parasitic capacitance reduction while preserving air gap volume.
Solution Approach 2:
The patent employs composite material structures combining multiple dielectric layers with different properties. The sealing dielectric layer and inter-layer dielectric layer form a composite structure that simultaneously preserves air gap volume and minimizes parasitic capacitance through the combined effects of air gaps and low-k dielectric materials.
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 effectively reduces parasitic capacitance between metal elements, optimizing the air gap volume and minimizing the dielectric constant, thereby enhancing circuit speed by reducing the RC constant.
Implementation Method 1
A porous dielectric layer is disposed over the substrate, sealing the flat top of the air gap
Implementation Method 2
the porous dielectric layer is an ultra-low-dielectric-constant (ULK) layer
Data Source
AI summary
A structure of semiconductor device includes a substrate, having a dielectric layer on top. The structure further includes at least two metal elements being adjacent, disposed in the dielectric layer, wherein an air gap is existing between the two metal elements. The air gap has a cross-section of substantially bottle shape with a flat top. A porous dielectric layer is disposed over the substrate, sealing the flat top of the air gap. An inter-layer dielectric layer disposed on the porous dielectric layer.