Airgap Formation in Semiconductor Interconnects
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Solution Overview
Problem
As semiconductor fabrication processes advance, the decreasing distance between adjacent metal interconnects in portable computing devices increases parasitic capacitance, which affects the performance and reliability of these devices.
Innovation Solution
The formation of airgaps in a dielectric layer between metal interconnects, achieved by etching portions of dielectric material through specific openings in an etch stop layer, reduces parasitic capacitance by limiting the sealing material that leaks into these airgaps and using dielectric barriers to prevent oxidation and enhance structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the distance between adjacent metal interconnects is decreased to improve device integration, then device functionality is enhanced, but parasitic capacitance between interconnects increases
Solution Approach 1:
Air is extracted from the dielectric material to create airgaps between adjacent metal interconnects. The etch stop layer is selectively removed in specific regions to allow formation of air-filled voids, which are then sealed with low-k dielectric material. This extraction of dielectric material and replacement with air (or air-equivalent low-k material) reduces the parasitic capacitance between closely spaced interconnects, enabling higher device integration without the harmful capacitive coupling effect.
Solution Approach 2:
The patent employs porous low-k dielectric material to fill the airgaps. This porous material has a dielectric constant lower than traditional solid dielectrics, mimicking the low-parasitic-capacitance benefit of airgaps while providing mechanical strength and oxidation protection. The porous structure allows the material to achieve effective permittivity reduction similar to air, resolving the contradiction between close spacing and parasitic capacitance.
2Object-generated harmful factors
If airgaps are formed between metal interconnects to reduce parasitic capacitance, then parasitic capacitance is reduced, but oxidation of conductive structures may occur
Solution Approach 1:
A porous low-k dielectric material is introduced as an intermediary substance to fill the airgaps. This material serves as a mediator that provides oxidation protection to the metal interconnects while maintaining the low parasitic capacitance characteristic. The porous structure allows it to function as an effective barrier against oxygen diffusion, preventing oxidation of the conductive structures beneath, thus resolving the contradiction between capacitance reduction and oxidation prevention.
Solution Approach 2:
The porous low-k dielectric material creates an inert environment around the metal interconnects by blocking oxygen access. This inert barrier prevents direct contact between oxygen and the conductive structures, eliminating the oxidation hazard while preserving the airgap's electrical benefit of reduced parasitic capacitance.
3Object-generated harmful factors
If airgaps are formed by etching dielectric material, then parasitic capacitance is reduced, but structural support for overlying structures may be compromised
Solution Approach 1:
Porous low-k dielectric material is used to fill the airgaps, providing structural support while maintaining low parasitic capacitance. The porous structure offers mechanical strength to support overlying interconnect layers and via structures, preventing collapse or deformation during subsequent fabrication processes. Simultaneously, the porous nature maintains the effective dielectric constant low enough to preserve the capacitance reduction benefit, resolving the contradiction between structural integrity and electrical performance.
Solution Approach 2:
The patent uses composite construction by combining the etch stop layer, porous low-k dielectric material, and sealing layers to create a structurally sound architecture. The composite material system provides both mechanical support for overlying structures and the electrical property of reduced parasitic capacitance, eliminating the need to choose between strength and capacitance reduction.
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 controls parasitic capacitance, improves electromigration behavior, and provides structural support for overlying structures, thereby enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
parasitic capacitance between adjacent metal interconnects increases
Implementation Method 2
A dielectric layer includes a region between the first and second conductive structures
Implementation Method 3
sealing the first and second airgaps by depositing a layer of low-k dielectric material on the etch stop layer
Implementation Method 4
The etch stop layer defines a first opening and a second opening that are proximate to the region between the first conductive structure and the second conductive structure
Data Source
AI summary
Devices and methods to reduce parasitic capacitance are disclosed. A device may include a dielectric layer. The device may include first and second conductive structures and an etch stop layer proximate to the dielectric layer. The etch stop layer may define first and second openings proximate to a region of the dielectric layer between the first and second conductive structures. The device may include first and second airgaps within the region. The device may include a layer of material proximate to (e.g., on, above, or over) the etch stop layer. The layer of material proximate to the etch stop layer may cover the first and second airgaps.