Air-Gapped Isolation Walls for Transistor Parasitic Capacitance
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Solution Overview
Problem
Conventional transistors face issues with parasitic capacitance due to tightly-spaced conductive components, which degrade device performance and increase power consumption, particularly in high-density IC chips with back-side power delivery and non-planar transistor architectures.
Innovation Solution
Incorporating air gaps into the transistor layer to reduce capacitance by replacing portions of the gate cut dielectric with air, capped by a dielectric material, thereby isolating conductive components and reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conductive components are tightly spaced to increase device density, then device integration density is improved, but parasitic capacitance increases and device performance degrades
Solution Approach 1:
The patent extracts the harmful dielectric material from between adjacent gates and replaces it with air gaps. This removes the source of parasitic capacitance while maintaining the tight spacing of conductive components needed for high device density. The air gaps are created by removing portions of the gate cut dielectric layer, effectively taking out the problematic material that causes capacitive coupling between adjacent gates.
Solution Approach 2:
The patent introduces air gaps (porous spaces) into the transistor layer structure between adjacent gates. These air gaps serve as low-dielectric-constant regions that reduce parasitic capacitance while allowing the conductive components to remain tightly spaced. The porous air-filled structure provides electrical isolation without requiring additional material layers that would increase device footprint.
2Reliability
If air gaps are introduced to reduce parasitic capacitance, then device performance is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the air gaps during the gate cut dielectric deposition and patterning process, before final device assembly. The gate cut dielectric is deposited and then selectively removed to create air gaps in advance, so that subsequent processing steps can proceed without additional complexity. This preliminary structuring integrates the capacitance reduction feature into the existing fabrication flow rather than adding separate complex steps.
Solution Approach 2:
The gate cut dielectric layer serves as an intermediary that facilitates air gap formation. By depositing this dielectric layer and then selectively removing portions of it, the patent creates air gaps without directly manipulating the gate structures themselves. The dielectric layer acts as a sacrificial intermediary that enables the introduction of air gaps while maintaining compatibility with standard fabrication processes.
3Object-generated harmful factors
If dielectric material is removed to create air gaps, then parasitic capacitance is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies partial action by selectively removing only specific portions of the gate cut dielectric layer where air gaps are desired, rather than removing the entire dielectric layer. This selective removal is achieved through lithographic patterning that defines the precise locations of air gaps. The partial removal approach reduces parasitic capacitance only where needed between adjacent gates while maintaining dielectric material in other areas where it provides beneficial functions.
Solution Approach 2:
The patent applies local quality by creating air gaps at specific locations between adjacent gates where parasitic capacitance is most problematic. The gate cut dielectric is removed only in these localized regions, giving different parts of the device different properties - air-filled regions for capacitance reduction and dielectric-filled regions for electrical isolation. This local modification approach targets the harmful capacitance without unnecessarily altering the entire device structure.
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 implementation of air gaps significantly reduces parasitic capacitance, enhancing transistor performance, reducing power consumption, and enabling smaller, faster, and more energy-efficient electronic devices.
Implementation Method 1
Incorporating air gaps into the transistor layer to reduce capacitance by replacing portions of the gate cut dielectric with air, capped by a dielectric material, thereby isolating conductive components and reducing parasitic capacitance.
Implementation Method 2
capped by a dielectric material, thereby isolating conductive components and reducing parasitic capacitance
Data Source
Figure 1A~1B
Figure 2
Figure 3A
AI summary
Air gaps are incorporated into a transistor layer to reduce capacitance between conductive components. In some embodiments, along a gate cut region extending across the gates of multiple transistors, a gate cut dielectric may be partially or fully replaced by an air gap. The air gap may extend between two adjacent gates of two adjacent transistors, or between a gate and a via, where the via extends through the gate line and between two gates. As another example, air gaps may extend between adjacent source or drain regions between pairs of adjacent transistors, e.g., in a device that includes back side source or drain contacts. The air gap may be formed on the back side of the device. The air gaps are capped by a dielectric material, so that additional layers (e.g., back side interconnect layers) may be formed over the air gap.