Doped HfO2 Ferroelectric Layer for Negative Capacitance FETs
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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 such as 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, formed through specific annealing and capping processes, to create a ferroelectric dielectric layer in negative capacitance field effect transistors (NC FETs), enabling improved ferroelectric properties and compatibility with silicon-based semiconductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If un-doped HfO2 is used as gate material, then high-K property is achieved, but the material remains amorphous and paraelectric without ferroelectric properties
Solution Approach 1:
The patent changes the compositional parameter by doping HfO2 with aluminum (Al) to achieve a minimum of 5 at% Al content. This compositional modification enables the material to form a stable orthorhombic crystal phase that exhibits ferroelectric properties, resolving the contradiction between achieving ferroelectricity and maintaining compositional stability.
Solution Approach 2:
The patent creates a composite material system by combining HfO2 with aluminum dopant. This composite approach allows the formation of a stable orthorhombic phase that displays ferroelectric behavior, overcoming the limitation of un-doped HfO2 which remains amorphous and paraelectric despite having high-K properties.
2Reliability
If ferroelectric materials like PZT or BaTiO3 are used, then ferroelectric properties are achieved, but compatibility with silicon-based semiconductors is reduced and performance degrades with thickness reduction
Solution Approach 1:
The patent modifies the material composition by doping HfO2 with aluminum at concentrations of 5 at% or higher. This parameter change transforms the material properties to achieve ferroelectricity while maintaining compatibility with silicon-based semiconductor fabrication processes, avoiding the compatibility issues associated with traditional ferroelectric materials like PZT or BaTiO3.
Solution Approach 2:
The patent adopts HfO2-based material system that can be processed using standard semiconductor manufacturing techniques, replacing exotic ferroelectric materials like PZT or BaTiO3. This approach uses more readily available and process-compatible materials that can be deposited and annealed using conventional CMOS-compatible processes.
3Length of moving object
If ferroelectric material thickness is reduced, then device scaling is achieved, but ferroelectric properties degrade
Solution Approach 1:
The patent changes the compositional parameter by incorporating aluminum doping at 5 at% or higher concentrations in the HfO2 dielectric layer. This compositional modification enables the maintenance of stable ferroelectric polarization even when the dielectric layer thickness is reduced to 3 nm or below, allowing device scaling without sacrificing ferroelectric performance.
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 doped HfO2 layer maintains polarization without degradation down to 3 nm, enhancing the subthreshold swing and compatibility with silicon-based semiconductors, thus improving the performance of NC FETs for low power operation.
Implementation Method 1
a doped HfO2 layer with an orthorhombic crystal phase is used, formed through specific annealing and capping processes
Implementation Method 2
formed through specific annealing and capping processes
Implementation Method 3
negative capacitance field effect transistors (NC FETs)
Implementation Method 4
a ferroelectric material has been proposed
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.