Air Gap Insulation for Semiconductor Parasitic Capacitance Reduction
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Solution Overview
Problem
Semiconductor devices face challenges in reducing parasitic capacitance between conductive layer patterns, which affects operation speed and refresh characteristics, due to limitations in increasing distance between patterns and the high dielectric constants of traditional insulation layers.
Innovation Solution
The introduction of air gaps with a dielectric constant of '1' between bit lines and storage node contact plugs, achieved through selective etching and capping layer processes, reduces parasitic capacitance and prevents electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the distance between bit line and storage node contact plug is increased to reduce parasitic capacitance, then parasitic capacitance is reduced, but device area increases
Solution Approach 1:
The patent changes the dielectric parameter (dielectric constant) of the insulation layer from traditional high-k materials (silicon oxide k≈4, silicon nitride k≈7) to low-k materials (silicon boron nitride, silicon carbon nitride with k approaching 6, or air gaps with k=1). This parameter change allows maintaining small device area while reducing parasitic capacitance through material property modification rather than geometric expansion.
2Object-affected harmful factors
If the height of conductive layer patterns is decreased to reduce confrontation area, then parasitic capacitance is reduced, but resistance of conductive layer patterns increases
Solution Approach 1:
Instead of changing the geometric parameter (height) of conductive layers, the patent changes the dielectric parameter (dielectric constant) of the insulation layer. This allows reducing parasitic capacitance through C=kε₀A/d by lowering k, while maintaining the original height and resistance characteristics of the conductive layers unchanged.
3Ease of manufacture
If traditional insulation layers with high dielectric constant are used, then manufacturing is simple, but parasitic capacitance cannot be sufficiently reduced
Solution Approach 1:
The patent modifies the dielectric parameter by introducing air gaps (k=1) through selective etching and capping layer processes. This creates regions with extremely low dielectric constant, significantly reducing parasitic capacitance while using standard semiconductor fabrication techniques to maintain manufacturing feasibility.
Solution Approach 2:
The patent introduces air gaps as intermediary structures between the bit line and storage node contact plug. These air gaps act as mediators that provide electrical isolation with minimal parasitic capacitance, enabling the reduction of harmful capacitive coupling without requiring direct contact or complex shielding structures.
4Speed
If air gaps are introduced to reduce parasitic capacitance, then sensing margin and operation speed are enhanced, but device complexity increases
Solution Approach 1:
The insulation layer is segmented into multiple regions: regions with air gaps (k=1) between bit line and storage node contact plug, and regions with conventional insulation material elsewhere in the device. This segmentation allows localized reduction of parasitic capacitance where needed while maintaining standard insulation in other areas, balancing performance improvement with manufacturing complexity.
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 significantly decreases parasitic capacitance, enhancing the sensing margin and operation speed of semiconductor devices while preventing electrical shorts.
Implementation Method 1
The narrower space between the first conductive layer pattern and the second conductive layer pattern may raise a parasitic capacitance between the first conductive layer pattern and the second conductive layer pattern
Implementation Method 2
The dielectric constant (k) of the silicon oxide layer is approximately 4, and the dielectric constant (k) of the silicon nitride layer is approximately 7
Implementation Method 3
exposing a surface of the substrate by selectively etching the spacer layers; forming air gaps and capping spacers for covering upper portions of the air gaps by selectively etching the capping layer
Data Source
AI summary
A method for fabricating a semiconductor device includes forming a plurality of bit line structures over a substrate, forming multiple layers of spacer layers with a capping layer interposed therebetween over the bit line structures, exposing a surface of the substrate by selectively etching the spacer layers, forming air gaps and capping spacers for covering upper portions of the air gaps by selectively etching the capping layer, and forming storage node contact plugs between the bit line structures.