MgO Ferroelectric Tunnel Junction Memory for Low-Power Stability

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Solution Overview

Problem

Current memory devices face challenges in achieving high remnant polarization and coercive electrical field, which are essential for stability against noise and interference, while also requiring low power consumption.

Innovation Solution

The development of ferroelectric tunnel junction memory cells using magnesium oxide as a tunneling dielectric material, which allows for coherent electron tunneling and large tunneling electroresistance, thereby enhancing remnant polarization and coercive field, and reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional memory devices are used, then manufacturing is simpler, but remnant polarization and coercive electrical field are insufficient leading to poor stability against noise and interference

Engineering Contradiction:

Improvestability against noise and interferenceVSAvoiddevice structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs a composite structure consisting of a ferroelectric material layer (such as Pb(Zr,Ti)O3 or Pb1-xLaxZr1-yTiyO3) combined with a tunnel dielectric layer (such as Al2O3 or HfO2) to form a ferroelectric tunnel junction. This composite material approach enables simultaneous achievement of high remnant polarization and high coercive electrical field, providing stability against noise and interference while maintaining feasible manufacturing processes.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes parameter changes in the ferroelectric material composition (adjusting zirconium and lanthanum content in PLZT, or composition ratios in PZT) to optimize the balance between remnant polarization and coercive electrical field. By controlling deposition parameters such as oxygen partial pressure, temperature, and layer thickness during fabrication, the device achieves enhanced reliability without excessive complexity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If high remnant polarization and coercive electrical field are achieved, then stability against noise and interference improves, but power consumption increases

Engineering Contradiction:

Improvestability against noise and interferenceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent introduces a tunnel dielectric layer as an intermediary between the electrodes and the ferroelectric material. This tunnel barrier enables tunneling electroresistance effect, allowing the device to achieve high stability through enhanced polarization control while reducing the energy required for switching. The tunnel dielectric acts as a mediator that facilitates low-power operation by enabling quantum tunneling mechanisms for state switching.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces conventional capacitive switching mechanisms with quantum mechanical tunneling effects in the ferroelectric tunnel junction. This substitution allows for non-volatile memory storage with lower power consumption, as the tunneling current provides inherent stability without requiring continuous power supply, thereby achieving both high reliability and energy efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 use of magnesium oxide in ferroelectric tunnel junction memory cells improves domain uniformity, leading to more coherent electron tunneling and large ferroelectric tunneling resistance, resulting in stable and low-power memory devices.

Implementation Method 1

magnesium oxide as a tunneling dielectric material, which allows for coherent electron tunneling and large tunneling electroresistance

Methodology Applied

Scientific EffectElectron tunneling: Conduction (electrical)

Implementation Method 2

A ferroelectric material is a material that may have spontaneous nonzero electrical polarization (i.e., non-zero total electrical dipole moment) when the external electrical field is zero. The spontaneous electrical polarization may be reversed by a strong external electric field applied in the opposite direction. The electrical polarization is dependent not only on the external electrical field at the time of measurement, but also on the history of the external electrical field, and thus, has a hysteresis loop.

Methodology Applied

Scientific EffectFerroelectricity: Hysteresis

Data Source

PatentUS12120885B2Ferroelectric tunnel junction memory device using a magnesium oxide tunneling dielectric and methods for forming the same

Publication Date: 2024.10.15 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A ferroelectric tunnel junction (FTJ) memory device includes a bottom electrode located over a substrate, a top electrode overlying the bottom electrode, and a ferroelectric tunnel junction memory element located between the bottom electrode and the top electrode. The ferroelectric tunnel junction memory element includes at least one ferroelectric material layer and at least one tunneling dielectric layer.