Gate Stack Vacuum Gap Reduces Parasitic Capacitance
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Solution Overview
Problem
The semiconductor industry faces challenges in forming reliable semiconductor devices at increasingly smaller sizes due to the complexity and difficulty of fabrication processes as feature sizes decrease, leading to issues with parasitic capacitance and device performance in FinFETs.
Innovation Solution
The formation of semiconductor device structures involves creating gaps between the gate and gate dielectric layers to reduce parasitic capacitance, achieved through a process that includes forming a sacrificial layer, depositing a gate dielectric layer, and removing the sacrificial layer to create trenches, which are then sealed with a sealing material, thereby improving transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency increases and costs decrease, but fabrication process difficulty and complexity increase
Solution Approach 1:
The gate structure is segmented into multiple components: gate dielectric layer, gate electrode layer, and side wall spacers. The side wall spacers are formed as separate structures on opposite sides of the gate stack, dividing the gate region into distinct segments that can be independently controlled and formed, thereby simplifying the fabrication process at scaled dimensions
Solution Approach 2:
The method performs preliminary actions by first forming the gate dielectric layer and gate electrode layer completely before forming the side wall spacers. This sequence ensures that the gate structure is fully established and stable before adding additional components, reducing fabrication complexity despite feature size reduction
2Length of moving object
If gate and gate dielectric layers are positioned closer together, then device size decreases, but parasitic capacitance increases and transistor performance deteriorates
Solution Approach 1:
The side wall spacers extend in the vertical dimension above and below the gate electrode layer, creating separation between the gate and source/drain regions in the vertical direction. This dimensional approach allows the gate and gate dielectric to remain close in the horizontal plane for small device size while maintaining electrical isolation through vertical spacing provided by the spacers
Solution Approach 2:
The side wall spacers act as intermediary structures positioned between the gate electrode layer and the source/drain regions. These spacers mediate the spatial relationship by providing physical separation and reducing parasitic capacitance coupling, allowing the gate and gate dielectric layers to be positioned close together without compromising transistor performance
Data Source
AI summary
A semiconductor device structure is provided. The semiconductor device structure includes a substrate. The semiconductor device structure includes a first source/drain structure and a second source/drain structure in the substrate. The semiconductor device structure includes a gate stack over the substrate and between the first source/drain structure and the second source/drain structure. The gate stack includes a gate dielectric layer and a gate over the gate dielectric layer, a portion of the gate dielectric layer is adjacent to a first sidewall of the gate, the gate stack has a gap between the first sidewall and the portion of the gate dielectric layer, and the gap is a vacuum gap or an air gap.