Ferroelectric Memory Device Multi-Level Storage

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Solution Overview

Problem

Ferroelectric memory devices face challenges in reliably maintaining partially switched polarization orientation states during read and write operations, which is crucial for storing multiple levels of logic information effectively.

Innovation Solution

A ferroelectric memory device is designed with a substrate, a ferroelectric structure comprising a first and second ferroelectric material layer, an electrical floating layer, and a gate electrode layer, where the hysteresis loops of the second ferroelectric material layer differ from those of the first, allowing for controlled polarization orientation adjustments through varying write voltages to store multiple levels of logic information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single ferroelectric material layer is used, then the device structure is simple, but it cannot store multiple levels of logic information reliably

Engineering Contradiction:

Improvestorage capacityVSAvoidstructure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The ferroelectric memory device divides the single ferroelectric layer into multiple stacked ferroelectric material layers (first, second, and third layers). Each layer can be independently controlled to store different logic levels, enabling multi-level storage capacity while maintaining a relatively compact vertical structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite ferroelectric material layers with different material compositions or properties. The first, second, and third ferroelectric material layers may have different coercive fields or hysteresis characteristics, allowing each layer to respond differently to applied voltages and thereby store distinct logic information reliably.

Inventive Principle:

Principle #40Composite materials

2Productivity

If write voltage is increased to switch polarization orientation, then logic information can be written, but adjacent cells may be altered

Engineering Contradiction:

Improvewrite operation efficiencyVSAvoiddata integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies different write voltages to different ferroelectric material layers based on their specific characteristics. The first write voltage is applied to the first ferroelectric material layer, a second write voltage to the second layer, and a third write voltage to the third layer. This localized voltage application ensures that only the intended cell's specific layer is switched, preventing interference with adjacent cells while maintaining efficient write operations.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If read operation is performed on target cell, then data can be read, but adjacent cells may be affected

Engineering Contradiction:

Improveread accuracyVSAvoidcell isolation

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements cell isolation by applying different read voltages to different ferroelectric material layers. The first read voltage is applied to the first layer, a second read voltage to the second layer, and a third read voltage to the third layer. This selective voltage application ensures that the read operation affects only the target cell's corresponding layer, preventing disturbance to adjacent cells while achieving accurate data retrieval.

Inventive Principle:

Principle #3Local quality

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 configuration enables reliable storage of multiple levels of logic information by maintaining stable remanent polarization states during read operations and allowing for precise control of polarization orientation, ensuring reliable data storage without altering the polarization state of adjacent cells.

Implementation Method 1

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

Methodology Applied

Scientific EffectSpontaneous electrical polarization: Polarisation

Implementation Method 2

a ferroelectric material can be controlled by an externally applied electric field to maintain either of two stable remanent polarization states on a hysteresis curve

Methodology Applied

Scientific EffectRemanent polarization: Hysteresis

Implementation Method 3

A hysteresis loop of the second ferroelectric material layer differs from a hysteresis loop of the first ferroelectric material layer

Methodology Applied

Scientific EffectHysteresis loop: Hysteresis

Implementation Method 4

the electrical floating layer comprises a conductive material

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS10978483B2Ferroelectric memory device

Publication Date: 2021.04.13 SK HYNIX INC

AI summary

A ferroelectric memory device includes a substrate having a source region and a drain region, a ferroelectric structure having a first ferroelectric material layer, an electrical floating layer, and a second ferroelectric material layer sequentially stacked on the substrate, and a gate electrode layer disposed on the ferroelectric structure. A coercive electric field of the first ferroelectric material layer is different from that of the second ferroelectric material layer, and the electrical floating layer comprises a conductive material.