Doped HfO2 Ferroelectric Layer for NC FET Subthreshold Swing
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Solution Overview
Problem
Conventional semiconductor devices face challenges in achieving a low subthreshold swing due to the limitations of high-K gate materials like un-doped HfO2, which are amorphous and paraelectric, and ferroelectric materials like PZT or BaTiO3, which are not fully compatible with silicon-based semiconductors and degrade with thickness reduction.
Innovation Solution
A doped HfO2 layer with an orthorhombic crystal phase is used, where the crystal orientation is controlled to achieve ferroelectric properties, integrated into a negative-capacitance field effect transistor (NC FET) structure, utilizing a capping layer and seed dielectric layers to maintain polarization and enhance ferroelectric effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If un-doped HfO2 is used as gate material, then high-K property is achieved, but ferroelectric properties are lost due to amorphous structure
Solution Approach 1:
The patent changes the crystal structure parameter of HfO2 from amorphous to orthorhombic phase through doping and annealing processes. This parameter change enables the material to exhibit ferroelectric properties while maintaining high-K characteristics, resolving the contradiction between achieving high-K properties and maintaining ferroelectric stability.
Solution Approach 2:
The patent creates a composite structure by doping HfO2 with other elements (such as Si, Al, or Ta) to stabilize the orthorhombic phase. This composite approach allows the material to simultaneously achieve high-K properties and stable ferroelectric behavior, overcoming the limitation of un-doped amorphous HfO2.
2Reliability
If traditional ferroelectric materials like PZT or BaTiO3 are used, then ferroelectric properties are achieved, but compatibility with silicon-based semiconductors deteriorates
Solution Approach 1:
The patent changes the material composition parameter from traditional ferroelectric materials (PZT, BaTiO3) to doped HfO2 with orthorhombic phase. This parameter change maintains ferroelectric properties while improving compatibility with silicon-based semiconductor manufacturing processes, as HfO2 can be deposited and annealed using standard CMOS-compatible techniques.
3Length of moving object
If ferroelectric material thickness is reduced, then device scaling is achieved, but ferroelectric properties degrade
Solution Approach 1:
The patent uses doped HfO2 composite material where the doping elements (Si, Al, Ta, etc.) stabilize the orthorhombic phase at reduced thicknesses. This composite approach allows the ferroelectric layer to be scaled down to thinner dimensions while maintaining stable ferroelectric properties, overcoming the degradation issue faced by traditional ferroelectric materials.
Solution Approach 2:
The patent changes the crystal phase parameter to orthorhombic phase through doping and controlled annealing, which enables the material to maintain ferroelectric properties at reduced thicknesses. The orthorhombic phase stabilization through doping allows thin film ferroelectric layers to retain their properties even when scaled down for advanced technology nodes.
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
The approach results in a steep subthreshold swing for low power operation, maintaining ferroelectric properties down to 3 nm, and is compatible with silicon-based semiconductors, improving the performance of NC FETs.
Implementation Method 1
A doped HfO2 layer with an orthorhombic crystal phase is used, where the crystal orientation is controlled to achieve ferroelectric properties
Implementation Method 2
utilizing a capping layer and seed dielectric layers to maintain polarization and enhance ferroelectric effects
Implementation Method 3
A doped HfO2 layer with an orthorhombic crystal phase is used, where the crystal orientation is controlled to achieve ferroelectric properties
Data Source
AI summary
In a method of manufacturing a negative capacitance structure, a dielectric layer is formed over a substrate. A first metallic layer is formed over the dielectric layer. After the first metallic layer is formed, an annealing operation is performed, followed by a cooling operation. A second metallic layer is formed. After the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase. The first metallic film includes a oriented crystalline layer.