Airgap Gate Structure for Dense Word Line Capacitance Reduction
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Solution Overview
Problem
Dense word line structures in semiconductor devices experience increased interference due to varying gate space geometries and WL space sizes, leading to unpredictable charge buildup and capacitance issues, which existing technologies, including cobalt-containing silicide layers, fail to adequately address.
Innovation Solution
The introduction of an airgap structure within the semiconductor device, formed using a deposited layer via chemical vapor deposition, along with a cobalt silicide layer, to reduce WL interference and capacitance, where the airgaps are defined by a spacer comprising a buffer oxide layer and liner silicon nitride film, and filled with high-density plasma dielectric material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the separation between two adjacent control gates is reduced to achieve dense WL structure, then the device density is improved, but the risk of interference between WL capacitances increases
Solution Approach 1:
An airgap material is introduced as an intermediary substance between adjacent control gates in dense WL regions. This airgap acts as a mediator that reduces the capacitive coupling between gates while maintaining the physical proximity required for high device density. The airgap material with lower dielectric constant than conventional isolation oxide provides electrical isolation while allowing the gates to remain closely spaced.
Solution Approach 2:
The dielectric constant parameter of the isolation material is changed from conventional oxide materials to airgap material with lower dielectric properties. This parameter change reduces the capacitance between adjacent control gates, thereby reducing interference in dense WL structures while maintaining the geometric configuration needed for high density.
2Reliability
If cobalt containing silicide layer is applied to reduce gate resistance, then the resistance is reduced, but interference in dense WL structures is not sufficiently reduced
Solution Approach 1:
The solution merges two previously separate functions into a unified approach: (1) applying cobalt silicide layer to reduce gate resistance, and (2) forming airgap structures to reduce capacitive interference. By combining these two techniques, the patent achieves both low resistance and reduced interference in dense WL structures, where either technique alone would be insufficient.
3Object-affected harmful factors
If airgap structure is formed using deposited layer via CVD process, then WL interference is reduced, but the manufacturing process complexity increases
Solution Approach 1:
The airgap structure is formed using a preliminary deposition action where a deposited layer is applied via CVD process before final patterning. This preliminary deposition creates the airgap material in the isolation regions, which is then patterned and etched to form the final airgap structure. This approach simplifies the overall process by establishing the airgap material presence early in the fabrication sequence.
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 structure effectively suppresses word line to word line capacitance, reducing interference and maintaining low resistance, while the cobalt silicide layer decreases RC delay and avoids substrate damage, resulting in a resilient gate structure with minimal cobalt residue.
Implementation Method 1
the deposited layer defining the airgap is deposited using a chemical vapor deposition (CVD) process
Implementation Method 2
A high density plasma dielectric material may fill any gaps that are in the space structure
Data Source
AI summary
A process for fabricating a gate structure, the gate structure having a plurality of gates defined by a network of spaces. The word line (WL) spaces within a dense WL region having airgaps and those spaces outside of the dense WL being substantially free of airgaps. A gate structure having a silicide layer dispose across the plurality of gates is also provided.