Metal Gate Stack Structure for Low-Parasitic GAA Transistors
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Solution Overview
Problem
The challenge of forming reliable semiconductor devices at smaller sizes is exacerbated by the complexity of fabrication processes as feature sizes continue to decrease, making it difficult to achieve high production efficiency and lower costs.
Innovation Solution
The formation of semiconductor device structures involves the use of multi-patterning photolithography and self-aligned processes to create fin structures and gate all around (GAA) transistor structures, utilizing materials like silicon oxide, silicon nitride, and high-k dielectric materials, along with epitaxial growth and selective etching to form precise semiconductor layers and gate stacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency and cost are improved, but fabrication process complexity and difficulty increase
Solution Approach 1:
The fabrication process is divided into multiple sequential 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 high-density patterns to be formed through manageable stages, maintaining productivity while controlling process complexity through systematic breakdown of the fabrication sequence.
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 without requiring direct patterning of the final geometry, thus managing fabrication complexity while achieving high functional density.
2Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency and cost are improved, but manufacturing reliability deteriorates
Solution Approach 1:
The self-aligned patterning process uses the previously formed structures (mandrels, spacers) to automatically define the position of subsequent features without requiring additional alignment steps. This self-service mechanism eliminates alignment errors that would compromise reliability at smaller feature sizes, while maintaining high productivity through integrated pattern formation.
Solution Approach 2:
Multiple spacer layers and mandrel structures are formed beforehand to create buffer zones and alignment references that protect against dimensional variations and process variability. These preliminary structures cushion against manufacturing variations, ensuring reliable feature formation at reduced sizes while maintaining production efficiency.
3Reliability
If multi-patterning photolithography and self-aligned processes are used to create precise fin structures and gate all around transistor structures, then device reliability and operation speed are improved by reducing parasitic capacitance, but fabrication process complexity increases
Solution Approach 1:
Multiple patterned layers are nested within each other in a self-aligned sequence, where each layer is formed using the previous layer as a template. This nesting approach creates complex three-dimensional fin structures and gate-all-around transistor geometries through sequential deposition and etching steps, achieving high reliability through precise feature formation while managing process complexity through systematic layer integration.
Solution Approach 2:
The fabrication process transitions from two-dimensional planar patterning to three-dimensional structure formation through vertical stacking of semiconductor layers, dielectric layers, and metal gates. This dimensional transition creates gate-all-around transistor structures with superior electrical characteristics and reduced parasitic capacitance, improving reliability while the self-aligned process manages the increased fabrication 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 enables the creation of reliable semiconductor devices with improved reliability and operation speed by reducing parasitic capacitance and ensuring precise feature formation, thereby enhancing manufacturing efficiency and reducing costs.
Implementation Method 1
forming a gate dielectric layer to wrap around the semiconductor nanostructures
Implementation Method 2
introducing oxygen-containing plasma on the first metal-containing layer to transform an upper portion of the first metal-containing layer into a metal oxide layer
Implementation Method 3
utilizing materials like silicon oxide, silicon nitride, and high-k dielectric materials, along with epitaxial growth and selective etching to form precise semiconductor layers
Data Source
AI summary
A semiconductor device structure is provided. The semiconductor device structure includes a channel structure and an epitaxial structure beside the channel structure. The semiconductor device structure also includes a metal gate stack over the semiconductor nanostructures. The metal gate stack includes a gate dielectric layer, a first work function layer over the gate dielectric layer, and a metal oxide layer over the first work function layer. The metal oxide layer is thinner than the first work function layer. The metal gate stack also includes a second work function layer over the metal oxide layer.