Doped Ferroelectric Memory Cells for Sub-5 nm Polarization Stability
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Solution Overview
Problem
Existing ferroelectric memory devices have limited memory cell density due to ferroelectric materials losing their properties at small dimensions, leading to depolarization fields and failure to crystallize in thin films.
Innovation Solution
A doped ferroelectric layer with a concentration gradient of dopants from Group II, III, and Lanthanide elements is used, enhancing high-K ferroelectric film crystallization, reducing structural defects, and increasing remnant polarization, allowing ferroelectric properties at thinner thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ferroelectric material thickness is reduced to increase memory cell density, then memory cell array density is improved, but ferroelectric properties are lost due to depolarization fields and failure to crystallize
Solution Approach 1:
The patent applies local quality by introducing dopants with specific concentration gradients at different locations within the ferroelectric layer. The dopant concentration varies from the first interface to the second interface, creating regions with different properties. This local variation in dopant concentration enables the thin ferroelectric layer to maintain crystallization and ferroelectric properties while achieving high density.
Solution Approach 2:
The patent changes the chemical composition parameters of the ferroelectric layer by incorporating dopants from Group II, III, and Lanthanide elements. The dopant concentration is controlled within specific ranges (e.g., 0.1-10 at%) and varies through the layer thickness, fundamentally altering the material properties to enable stable ferroelectric behavior at reduced thicknesses below 5 nm.
2Reliability
If dopant concentration is increased to enhance ferroelectric properties, then remnant polarization is improved, but structural defects may increase
Solution Approach 1:
The patent uses local quality by implementing different dopant concentrations at different locations within the ferroelectric layer. The dopant concentration gradient ensures that regions with higher dopant content (which enhance polarization) are strategically positioned, while regions with lower dopant content minimize structural defects. This spatial variation optimizes the balance between remnant polarization and structural integrity.
Solution Approach 2:
The patent creates a composite ferroelectric material system by combining host ferroelectric material with multiple types of dopants (Group II, III, and Lanthanide elements). This composite structure allows the material to benefit from the synergistic effects of different dopants, where some dopants enhance polarization while others suppress defect formation, achieving both high remnant polarization and low structural defects.
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 approach increases memory cell array density, improves film quality, and maintains ferroelectric properties at thicknesses below 5 nm, enhancing the orthorhombic phase and overall performance of ferroelectric memory devices.
Implementation Method 1
enhancing high-K ferroelectric film crystallization
Implementation Method 2
A doped ferroelectric layer with a concentration gradient of dopants from Group II, III, and Lanthanide elements is used
Implementation Method 3
A ferroelectric material has a nonlinear relationship between the applied electric field and the apparent stored charge and thus, can switch polarity in an electric field
Data Source
AI summary
Embodiments of ferroelectric memory devices and methods for forming the ferroelectric memory devices are disclosed. In an example, a method of forming a ferroelectric memory cell is disclosed. A first electrode is formed. A doped ferroelectric layer is formed in contact with the first electrode. The doped ferroelectric layer includes oxygen and one or more ferroelectric metals. The doped ferroelectric layer further includes a plurality of dopants including at least one dopant from one of Group II elements, Group III elements, or Lanthanide elements. The plurality of dopants are different from the one or more ferroelectric metals. A second electrode is formed in contact with the doped ferroelectric layer.