2D Material Gate-All-Around CFET Stacking for Transistor Scaling
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Solution Overview
Problem
Conventional semiconductor transistors face challenges in further scaling beyond FinFETs and nanowires, particularly when reducing dimensions to single-digit nanometers, necessitating new materials and configurations to enhance performance and energy efficiency.
Innovation Solution
The integration of 2D-material gate-all-around (GAA) complementary field effect transistors (CFETs) using transition metal dichalcogenide (TMD) channels, which are stacked to form a 3D configuration, with complementary transistors of opposite conductivity types and a common gate structure to induce conductive paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional silicon-based transistors are scaled down to single-digit nanometers, then transistor density increases, but fabrication becomes problematic and performance degrades
Solution Approach 1:
The patent changes the material parameter from conventional silicon to transition metal dichalcogenide (TMD) 2D materials, enabling continued scaling to single-digit nanometers while maintaining fabrication feasibility and performance. The 2D material's atomic-layer thickness and unique electronic properties allow for effective channel control at dimensions where silicon-based transistors fail.
Solution Approach 2:
The patent employs composite material structures including TMD channels combined with high-k dielectric gate oxides and metal gates. This composite approach leverages the complementary strengths of different materials: TMD provides superior mobility and scaling characteristics, while high-k dielectrics enable effective gate control with reduced leakage, together solving the fabrication and performance degradation issues at single-digit nanometer scales.
2Area of stationary object
If transistor dimensions are reduced to enhance density, then area decreases, but drive current and energy efficiency deteriorate
Solution Approach 1:
The patent transitions from planar 2D channel structures to vertically stacked 3D GAA configurations. This dimensional change allows multiple channel structures to occupy a smaller footprint area while maintaining or enhancing drive current through increased effective channel width. The vertical stacking enables better electrostatic control and higher current density without proportionally increasing area.
Solution Approach 2:
The patent changes the channel material parameter to TMD 2D materials, which exhibit superior charge carrier mobility and electrostatic control compared to conventional materials. This parameter change enables maintaining high drive current at reduced dimensions, and the gate-all-around configuration further enhances gate control efficiency, allowing effective drive current preservation despite area reduction.
3Area of stationary object
If transistor dimensions are reduced to enhance density, then area decreases, but switching capacitance increases
Solution Approach 1:
The gate-all-around vertical configuration wraps the gate electrode completely around the channel in three dimensions, providing superior electrostatic control compared to planar gates. This dimensional change reduces the effective gate-to-channel distance and improves field control efficiency, thereby reducing switching capacitance and energy requirements despite reduced transistor area.
Solution Approach 2:
The combination of TMD 2D channel materials with high-k dielectric gate oxides creates a composite structure with enhanced electrostatic control. The high-k dielectric increases gate capacitance efficiency, allowing better control with lower voltage swings, which reduces switching energy. The TMD material's atomic precision and surface properties further minimize parasitic capacitance, addressing the switching capacitance increase issue at scaled dimensions.
Data Source
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AI summary
Disclosed is a complementary field effect transistor (CFET) formed from stacked 2D-material transistors. The 2D-material transistors are formed from transition metal dichalcogenide (TMD), which are atomically thin semiconductors. The stacked TMD transistors allow for enhanced drive current and lower switching capacitance, both of which are desirable.