Ferroelectric Memory Device with Dopant Gradient

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Solution Overview

Problem

Current ferroelectric memory devices face challenges in stabilizing ferroelectric properties due to transformations into paraelectric or antiferroelectric states, and in aligning defective dipoles, which affects data storage reliability.

Innovation Solution

A ferroelectric memory device is developed with a ferroelectric material layer having a concentration gradient of a dopant, generating a lattice strain gradient that results in a flexoelectric effect, forming an internal electric field to improve polarization alignment and stabilize ferroelectric properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional ferroelectric material layer is used, then the device structure is simple, but the ferroelectric properties are unstable due to transformations into paraelectric or antiferroelectric states

Engineering Contradiction:

Improveferroelectric property stabilityVSAvoidmaterial layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating a concentration gradient of dopant atoms within the ferroelectric material layer. The dopant concentration varies spatially, being higher at certain regions and lower at others, which generates a localized lattice strain gradient that stabilizes ferroelectric properties in specific areas while maintaining overall device functionality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical parameter of dopant concentration distribution within the ferroelectric material layer. By introducing a controlled gradient in dopant concentration rather than uniform distribution, the lattice strain is modified locally, which prevents unwanted phase transformations and stabilizes the ferroelectric state without requiring fundamental material changes.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a uniform dopant distribution is used, then the manufacturing process is simple, but defective dipoles cannot be aligned properly

Engineering Contradiction:

Improvepolarization alignmentVSAvoiddopant distribution control

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent implements local quality by establishing a non-uniform dopant concentration profile within the ferroelectric material layer. This spatial variation in dopant distribution creates localized regions with different lattice strain characteristics, which enables proper alignment of defective dipoles while maintaining manufacturability through controlled deposition processes.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent transitions from a uniform zero-dimensional dopant distribution to a gradient distribution that introduces spatial dimensionality. The dopant concentration varies along the thickness direction of the ferroelectric layer, creating a one-dimensional gradient that generates the necessary lattice strain variation for dipole alignment without significantly complicating the manufacturing process.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of manufacture

If the ferroelectric material layer is made thicker, then manufacturing is easier, but the polarization orientation is weaker

Engineering Contradiction:

Improvelayer thickness controlVSAvoidpolarization strength

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the dopant concentration parameter within the ferroelectric material layer to compensate for the reduced polarization strength in thicker layers. By introducing a dopant gradient, particularly with higher concentration near the electrode interfaces, the lattice strain is optimized to enhance polarization orientation even in thicker material layers, thereby maintaining reliability while facilitating easier manufacturing.

Inventive Principle:

Principle #35Parameter changes

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 internal electric field enhances polarization orientation, preventing transformations into undesirable states and aligning defective dipoles, thereby stabilizing and improving the ferroelectric properties for reliable nonvolatile data storage.

Implementation Method 1

generating a lattice strain gradient that results in a flexoelectric effect, forming an internal electric field

Methodology Applied

Scientific EffectFlexoelectric effect:

Implementation Method 2

a ferroelectric material is a material having spontaneous electrical polarization in the absence of an applied external electric field

Methodology Applied

Scientific EffectSpontaneous polarization:

Implementation Method 3

Remanent polarization in a ferroelectric material can be reversibly switched by an external electric field

Methodology Applied

Scientific EffectPolarization switching:

Data Source

PatentUS10522564B2Ferroelectric memory device and method of manufacturing the same

Publication Date: 2019.12.31 SK HYNIX INC

AI summary

In an embodiment, a ferroelectric memory device includes a substrate having a source region and a drain region, a ferroelectric structure disposed on the substrate, and a gate electrode layer disposed on the ferroelectric structure. The ferroelectric structure includes a ferroelectric material layer having a concentration gradient of a dopant.