Double-Gate FinFET With Different Work Functions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor devices face short channel effects and excessive leakage when gate length is reduced below 100 nm, necessitating new device configurations to enable further dimension reduction in integrated circuits.
Innovation Solution
A double-gate metal oxide semiconductor field-effect transistor (MOSFET) structure is developed, featuring two gates with different work functions, where one gate is made of polycrystalline silicon and the other of a metal silicide compound, allowing for better short channel control through doping and silicide phase modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate length is reduced to below 100 nm to increase device density, then device density is improved, but short channel effects and excessive leakage occur
Solution Approach 1:
The gate is segmented into two separate gates with different work functions (first gate: n-type polysilicon, second gate: metal silicide compound) positioned on opposite sides of the fin. This segmentation allows independent control of each gate to address short channel effects while maintaining high device density.
Solution Approach 2:
Different materials with specific local properties are used for each gate: n-type polysilicon for the first gate and metal silicide compound for the second gate. This local quality differentiation enables tailored work functions to optimize both density and short channel control in specific device regions.
2Device complexity
If conventional single-gate structures are used, then device structure is simple, but short channel effects cause excessive leakage
Solution Approach 1:
The single gate is divided into two separate gates positioned on opposite sides of the fin structure. This segmentation provides dual control over the channel, improving leakage control while maintaining manageable device complexity through systematic fabrication processes.
Solution Approach 2:
The gate structure uses composite materials: n-type polysilicon for the first gate and metal silicide compound for the second gate. This composite approach combines different material properties to achieve superior leakage control compared to conventional single-material gates.
3Ease of manufacture
If gates are made from the same material, then manufacturing process is simple, but work function tuning flexibility is limited
Solution Approach 1:
Different materials are used for each gate to provide local quality differentiation: n-type polysilicon for the first gate and metal silicide compound for the second gate. This enables independent work function tuning for each gate while maintaining a systematic fabrication process that deposits layers sequentially across the substrate.
Solution Approach 2:
The use of composite materials (polysilicon and metal silicide compound) in the gate structure provides versatile work function tuning capabilities. Each material can be independently doped or modified to achieve desired work functions, enhancing adaptability while following a structured manufacturing approach.
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 configuration effectively reduces series resistance and improves short channel control, enabling further miniaturization of semiconductor devices by tuning the work functions of the gates and forming a metal silicide compound to enhance gate performance.
Implementation Method 1
annealing such that a metal silicide compound is formed by the polycrystalline silicon and metal overlying the second side of the fin
Implementation Method 2
projecting ions towards the substrate, at a non-perpendicular angle relative to its top surface, such that a greater number of ions are implanted in a portion of the polycrystalline silicon layer overlying the second side of the fin
Implementation Method 3
etching away oxide material isotropically to leave said localised layer
Data Source
AI summary
A double-gate FinFET and methods for its manufacture are provided. The FinFET includes first and second gates (72, 74) adjacent respective sides of the fin (20), with at least a portion of the first gate facing the fin being formed of polycrystalline silicon, and at least a portion of the second gate facing the fin being formed of a metal silicide compound. The different compositions of the two gates provide different respective work functions to reduce short channel effects.