Bitline Spacer Stack With Air Gap for Lower Parasitic Capacitance
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving compact size and improved electrical performance due to limitations in spacer structure design, which affect the efficiency and reliability of capacitor structures.
Innovation Solution
The semiconductor device incorporates a spacer structure with a sequence of spacers, including an air spacer and spacers made of different materials, such as silicon nitride and silicon oxynitride, with specific thicknesses and configurations to enhance electrical connectivity and reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spacer structure is used, then the device layout is simple, but parasitic capacitance increases and electrical performance deteriorates
Solution Approach 1:
The spacer structure is divided into multiple segments (first spacer, second spacer, third spacer, fourth spacer) with different materials and thicknesses. Each segment serves a specific function: the first and fourth spacers provide structural support, the second air spacer reduces parasitic capacitance, and the third spacer provides electrical isolation. This segmentation allows optimization of electrical performance while managing structural complexity.
Solution Approach 2:
Different regions of the spacer structure have different material compositions and thicknesses tailored to local requirements. The air spacer is positioned where parasitic capacitance reduction is most critical, while thicker spacers are placed where structural support is needed. This local optimization enables improved electrical characteristics without uniformly increasing device complexity.
2Stability of the object's composition
If spacer thickness is increased to maintain integrity, then structural stability improves, but device area increases
Solution Approach 1:
Instead of using a single thick spacer, the structure is segmented into multiple thinner spacers stacked vertically. This maintains the required structural integrity through cumulative thickness while reducing the lateral footprint. The segmented approach allows the spacer to achieve mechanical stability without proportionally increasing device area.
Solution Approach 2:
The spacer structure transitions from a lateral expansion approach to a vertical stacking approach. By arranging spacers in the vertical dimension (first through fourth spacers stacked sequentially), the structure achieves the required integrity without proportionally increasing the horizontal device area. This dimensional transition optimizes the area-to-integrity ratio.
3Reliability
If air spacer is introduced to reduce parasitic capacitance, then electrical characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The air spacer structure is designed to be formed during the existing spacer fabrication process sequence, integrating the air gap creation into preliminary manufacturing steps. By planning the air spacer formation as part of the standard spacer deposition and etch sequence, the manufacturing complexity is minimized while achieving the electrical benefits.
Solution Approach 2:
The air spacer acts as an intermediary element between conductive structures, providing electrical isolation and reducing parasitic capacitance. Its presence as a non-material spacer simplifies the overall manufacturing process compared to requiring additional insulating material deposition and patterning steps, as the air gap can be created through selective removal of sacrificial materials during existing process steps.
Data Source
AI summary
A semiconductor device includes a substrate including first and second active regions; a bitline structure extending in one direction on the substrate, the bitline structure being electrically connected to the first active region; a storage node contact on a sidewall of the bitline structure, the storage node contact being electrically connected to the second active region; a spacer structure between the bitline structure and the storage node contact; a landing pad on the storage node contact, the landing pad being in contact with a sidewall of the spacer structure; and a capacitor structure electrically connected to the landing pad, wherein the spacer structure includes a first spacer, a second spacer, a third spacer, and a fourth spacer, sequentially stacked on the sidewall of the bitline structure, the second spacer is an air spacer, and the third spacer has a thickness that is less than a thickness of the first spacer.