GAA Gate Stack Structure for Lower Parasitic Capacitance
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Solution Overview
Problem
The challenge in the semiconductor industry is to form reliable semiconductor devices at increasingly smaller sizes due to the complexity and difficulty of fabrication processes as feature sizes decrease, which affects production efficiency and costs.
Innovation Solution
The method involves forming a gate all around (GAA) transistor structure using a sacrificial layer and cladding layer process, where a sacrificial nanostructure is etched at a slower rate than the cladding layer, allowing for the formation of a gate stack with reduced parasitic capacitance and improved performance by increasing the distance between the gate stack and source/drain structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are decreased to increase functional density, then production efficiency and cost are improved, but fabrication process difficulty and reliability increase
Solution Approach 1:
The fabrication process is divided into multiple patterning steps (e.g., self-aligned double patterning, self-aligned triple patterning) where each step creates a portion of the final pattern. This segmentation allows complex nanoscale features to be formed through sequential simpler steps, managing fabrication complexity while achieving high functional density
Solution Approach 2:
Mandrel structures and spacer layers are formed in advance before the final pattern transfer. These preliminary structures serve as templates that guide subsequent etching steps, enabling precise feature formation at reduced sizes while maintaining process reliability
2Productivity
If feature sizes are decreased to increase functional density, then production efficiency and cost are improved, but device reliability deteriorates
Solution Approach 1:
Different regions of the device structure receive different treatments and material compositions optimized for their specific functions. For example, channel regions, source/drain regions, and gate regions are engineered with distinct properties to ensure reliable operation at scaled dimensions
Solution Approach 2:
Protective layers, sacrificial structures, and process control measures are implemented in advance to prevent defects and variability from compromising device reliability during fabrication and operation at reduced feature sizes
3Volume of moving object
If gate stack distance from source/drain is reduced, then device size is decreased, but parasitic capacitance increases
Solution Approach 1:
The gate stack is wrapped around the channel structure in a three-dimensional configuration, with the gate electrode surrounding the channel on multiple sides. This nested arrangement maximizes gate control while minimizing the footprint and reducing parasitic capacitance to source/drain regions
Solution Approach 2:
The device transitions from planar two-dimensional geometry to three-dimensional structures such as FinFETs or gate-all-around configurations. This dimensional change increases effective channel width without increasing planar footprint and reduces parasitic capacitance through improved spatial separation
Data Source
AI summary
A semiconductor device structure is provided. The semiconductor device structure includes a substrate including a base and a fin structure over the base. The fin structure includes a nanostructure. The semiconductor device structure includes a gate stack over the base and wrapped around the nanostructure. The gate stack has an upper portion and a sidewall portion, the upper portion is over the nanostructure, and the sidewall portion is over a first sidewall of the nanostructure. The semiconductor device structure includes a first inner spacer and a second inner spacer over opposite sides of the sidewall portion. A sum of a first width of the first inner spacer and a second width of the second inner spacer is greater than a third width of the sidewall portion as measured along a longitudinal axis of the fin structure.