Fork Sheet FET Airgap Isolation for Capacitance Coupling
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Solution Overview
Problem
Fork sheet FET devices face challenges due to close proximity of NFET and PFET source/drain regions and gates, leading to capacitance coupling issues that result in false turn-on of transistors and affect read/write stability.
Innovation Solution
Incorporating an airgap in the dielectric pillar between NFET and PFET devices, which reduces capacitance coupling by utilizing a dielectric liner that pinches off at the top portion of the opening, creating a dielectric pillar with an airgap, thereby minimizing electrical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a minimal insulator is employed between NFET and PFET source/drain regions and gates, then area scaling is improved, but capacitance coupling increases causing false turn-on and read/write stability issues
Solution Approach 1:
An airgap dielectric pillar is introduced as an intermediary structure between the NFET and PFET source/drain regions and gates. This pillar acts as a mediator that physically separates the closely spaced transistor components while maintaining the compact fork sheet layout, thereby reducing capacitance coupling without sacrificing area scaling benefits
Solution Approach 2:
The dielectric pillar is positioned locally at critical interfaces where capacitance coupling occurs most strongly - specifically between source/drain regions and between gates. This localized dielectric insertion provides targeted capacitance reduction at the most problematic coupling points while leaving other areas of the device unaffected
2Area of stationary object
If NFET and PFET are placed in close proximity for area scaling, then device density is improved, but capacitance coupling between source/drain regions and gates increases
Solution Approach 1:
The airgap dielectric pillar serves as a mediator structure that enables close proximity placement of NFET and PFET while simultaneously reducing the harmful capacitance coupling effect. The pillar is strategically positioned to interrupt the electric field coupling paths between adjacent transistor components
Solution Approach 2:
The dielectric pillar segments the continuous dielectric medium into distinct regions, creating isolated airgap zones between NFET and PFET components. This segmentation approach divides the coupling path into multiple smaller segments, each with reduced capacitance, thereby lowering overall coupling effects
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 airgap isolation significantly reduces capacitance coupling, enhancing the stability and performance of fork sheet FET devices by lowering the dielectric constant between NFET and PFET components.
Implementation Method 1
The airgap isolation significantly reduces capacitance coupling, enhancing the stability and performance of fork sheet FET devices by lowering the dielectric constant between NFET and PFET components
Data Source
AI summary
Fork sheet FET devices with airgap isolation are provided. In one aspect, a fork sheet FET device includes: at least a first nanosheet FET and a second nanosheet FET; and a dielectric pillar disposed directly between the first nanosheet FET and the second nanosheet FET, wherein the dielectric pillar includes an airgap. For instance, the first nanosheet FET and the second nanosheet FET can have nanosheets that extend horizontally on opposite sides of the dielectric pillar. A method of forming a fork sheet FET device having airgap isolation is also provided.