Bismuth-Doped Ferroelectric Memory Cells for Thin-Film Scaling
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Solution Overview
Problem
Conventional ferroelectric materials, such as lead zirconate titanate (PZT), face limitations in bit density and scalability due to low remnant polarization and compatibility issues with standard semiconductor processing techniques, making them unsuitable for non-volatile memory devices with feature sizes of 20 nm or less.
Innovation Solution
Doping hafnium oxide with bismuth to create ferroelectric materials like hafnium bismuth oxide, which exhibits improved remnant polarization and compatibility, allowing for thinner films with enhanced readout signals and extended useful life in memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ferroelectric materials like PZT are used, then ferroelectric properties are maintained, but remnant polarization is low and scalability to 20 nm or less is limited
Solution Approach 1:
The patent changes the material composition parameters by doping hafnium oxide with bismuth at specific concentrations (0.1-10 atomic percent). This parameter change enables the material to maintain ferroelectric properties at reduced thicknesses while achieving higher remnant polarization, directly resolving the contradiction between maintaining ferroelectric properties and reducing film thickness for scalability.
Solution Approach 2:
The patent creates a composite material system by combining hafnium oxide with bismuth dopant. This composite approach produces hafnium bismuth oxide, which exhibits superior ferroelectric properties including enhanced remnant polarization and stability at thin film thicknesses, thereby resolving the limitation of conventional materials at 20 nm scale.
2Quantity of substance
If PZT film thickness is reduced to achieve higher density, then bit density improves, but ferroelectric properties are lost
Solution Approach 1:
By modifying the material composition through bismuth doping, the patent enables the ferroelectric material to maintain its properties at reduced thicknesses. This parameter change allows thinner films to be used, increasing bit density while preserving ferroelectric functionality, thus resolving the contradiction between density and reliability.
3Ease of manufacture
If conventional ferroelectric materials are used, then compatibility with existing processes is maintained, but remnant polarization remains low limiting readout signal
Solution Approach 1:
The patent modifies the material composition by introducing bismuth dopant into hafnium oxide, changing the material parameters to achieve higher remnant polarization. This compositional change enables improved readout signals while the doping process remains compatible with existing semiconductor manufacturing techniques, resolving the contradiction between process compatibility and 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 bismuth-doped ferroelectric materials demonstrate up to a 25% increase in remnant polarization, leading to improved memory readout signals and longer operational life compared to conventional materials, while maintaining desired ferroelectric properties at reduced thicknesses.
Implementation Method 1
Doping hafnium oxide with bismuth to create ferroelectric materials like hafnium bismuth oxide, which exhibits improved remnant polarization
Implementation Method 2
Ferroelectric materials exhibiting a switchable polarization responsive to application of an electric field (e.g., a bias voltage). Ferroelectric materials may include at least two polarization states, which polarization states may be switched by the application of the electric field.
Data Source
AI summary
A ferroelectric device includes an electrode, another electrode, and a ferroelectric structure between the electrode and the another electrode. The ferroelectric structure includes one or more portions of bismuth oxide, and one or more portions of at least one metal oxide comprising hafnium-containing oxide, zirconium-containing oxide, or a combination thereof. A ferroelectric memory cell includes a source region, a drain region, and a capacitor in electrical communication with the drain region. The capacitor includes an electrode and a ferroelectric structure neighboring the electrode. The ferroelectric structure includes a first material comprising a first metal oxide, a second material comprising bismuth oxide, and a third material comprising a second metal oxide. The ferroelectric structure also includes a dopant in an amount of between about 0.1 atomic percent and about 25.0 atomic percent based on non-oxygen atoms of the ferroelectric structure.