Semiconductor Air Gap Structure for Parasitic Capacitance Reduction
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Solution Overview
Problem
As semiconductor devices become more highly integrated, the increasing parasitic capacitance between conductive structures degrades their performance, and reducing this capacitance with existing dielectric materials is limited by their high dielectric constant.
Innovation Solution
The introduction of air gaps between conductive structures, combined with the use of low resistance silicide layers and increased contact areas, reduces parasitic capacitance and improves contact resistance without relying on dielectric materials for capping the air gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If dielectric material is used to reduce parasitic capacitance, then capacitance reduction is achieved, but the high dielectric constant of the material limits further reduction
Solution Approach 1:
The patent extracts the dielectric material from the air gap region, removing the harmful high dielectric constant material that limits capacitance reduction. By replacing the dielectric material with air (vacuum), the parasitic capacitance is significantly reduced without the limitations imposed by solid dielectric materials.
Solution Approach 2:
The patent changes the dielectric constant parameter from high values (solid dielectric materials) to the minimum possible value (air/vacuum with dielectric constant ≈ 1). This parameter change enables maximum parasitic capacitance reduction while maintaining electrical insulation functionality.
2Object-affected harmful factors
If air gaps are introduced between conductive structures, then parasitic capacitance is reduced, but additional fabrication steps are required
Solution Approach 1:
The patent performs preliminary actions by forming sacrificial spacers before depositing the capping conductive pattern. These sacrificial spacers define the future air gap dimensions and position, allowing the air gap to be created as an integrated part of the overall fabrication process rather than as a separate post-processing step.
Solution Approach 2:
The patent uses sacrificial spacers as intermediary elements that temporarily occupy the space where air gaps will eventually form. These spacers mediate between the conductive structures and the final air gap configuration, enabling precise air gap formation through standard semiconductor fabrication techniques.
3Reliability
If multiple conductive patterns are used to cap air gaps, then electrical insulation is improved, but contact resistance may increase
Solution Approach 1:
The patent employs composite conductive structures with multiple patterns having different functions. The first conductive pattern provides mechanical support and defines the air gap, while the second conductive pattern provides low-resistance electrical contact. This composite approach allows simultaneous optimization of insulation and conductivity.
Solution Approach 2:
The patent applies different properties to different parts of the conductive structure. The first conductive pattern is designed with properties optimized for structural support and air gap definition, while the second conductive pattern is designed with properties optimized for low contact resistance. This local differentiation resolves the contradiction between insulation and conductivity requirements.
Data Source
AI summary
A semiconductor device includes a dielectric structure which has an opening exposing a surface of a substrate; and a conductive structure which is formed in the opening, wherein the conductive structure comprises: a first conductive pattern recessed in the opening; a second conductive pattern covering a top surface and sidewalls of the first conductive pattern; an air gap defined between sidewalls of the opening and the second conductive pattern; and a third conductive pattern capping the second conductive pattern and the air gap.