Ferroelectric 2D Memory Transistor Gate Stack Design

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Solution Overview

Problem

Conventional computing systems face limitations in power consumption and performance due to issues like tunneling leakage current and high dissipated power, and existing non-volatile memory technologies, such as flash memory, require high voltages incompatible with CMOS technology, necessitating the development of novel architectures for improved data transmission rates and reduced power consumption.

Innovation Solution

The integration of two-dimensional material layers, specifically molybdenum disulfide (MoS2), with ferroelectric materials in a flexible electronics device structure, allowing for high-temperature processing without decomposition, and using a hybrid gate stack with zirconium-doped hafnium oxide and hafnium oxide layers to enhance ferroelectricity and reduce operating voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional memory cell size is shrunk to increase density, then storage capacity is improved, but tunneling leakage current increases and dissipated power increases

Engineering Contradiction:
Improvestorage densityVSAvoiddissipated power
Core Design Contradiction:
Quantity of substanceVSLoss of energy

Solution Approach 1:

The patent transitions from conventional silicon-based three-dimensional materials to two-dimensional material layers (such as MoS2, WSe2, WS2, MoSe2, black phosphorus, and antimonene), fundamentally changing the dimensional parameter of the channel material. This parameter change enables continued scaling at advanced technology nodes while avoiding the tunneling leakage and power dissipation issues that plague conventional scaled devices.

Inventive Principle:
Principle #35Parameter changes

2Quantity of substance

If flash memory is used for non-volatile storage, then storage capacity is improved, but high voltages (20V) are required for write and erase operations which are incompatible with CMOS

Engineering Contradiction:
Improvestorage capacityVSAvoidvoltage compatibility
Core Design Contradiction:
Quantity of substanceVSEase of operation

Solution Approach 1:

The patent employs ferroelectric materials (such as Pb(Zr1-xTix)O3 or Pb1-xLaxZr1-yTiyO3 with specific compositional ranges) in the gate dielectric layer, which enables non-volatile memory operation at low voltages compatible with standard CMOS processes. The ferroelectric polarization state provides non-volatile storage without requiring the high voltages needed by conventional flash memory.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure combining two-dimensional channel materials with ferroelectric gate dielectrics. This composite material system integrates the high mobility and atomic thinness of 2D materials with the non-volatile low-voltage switching characteristics of ferroelectrics, achieving both non-volatility and CMOS compatibility simultaneously.

Inventive Principle:
Principle #40Composite materials

3Loss of energy

If two-dimensional material layers are used in memory devices, then power consumption is reduced and performance is improved, but flexibility and mechanical robustness are enhanced

Engineering Contradiction:
Improvepower consumptionVSAvoidmechanical flexibility
Core Design Contradiction:
Loss of energyVSStrength

Solution Approach 1:

The patent utilizes the inherent flexibility of atomically thin two-dimensional material layers to create bendable and flexible memory devices. These 2D material channels can be integrated onto flexible substrates, enabling wearable electronics and flexible computing applications while maintaining low power consumption and high performance.

Inventive Principle:
Principle #30Flexible shells and thin films

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 enables the creation of flexible, low-power, high-performance memory devices with efficient data storage and transmission, achieving distinct write and erase states with low-voltage operation and synaptic-like behavior, suitable for energy-efficient computing applications.

Implementation Method 1

A ferroelectric layer is provided over the buffer layer

Methodology Applied
Scientific EffectFerroelectricity:

Implementation Method 2

a two-dimensional material layer provided over a portion of a top surface of the dielectric layer

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP3759740B1Ferroelectric low power 2d memory transistor and fabrication method thereof
Publication Date: 2023.06.21 MITSUBISHI ELECTRIC CORP
  • EP3759740B1 patent drawingFigure 1A
  • EP3759740B1 patent drawingFigure 1B
  • EP3759740B1 patent drawingFigure 1C

AI summary

Disclosed is a transistor device including a memory cell comprising a gate stack with sidewalls provided over a substrate. The gate stack includes a metal gate layer provided over the substrate. A buffer layer is provided over the metal gate layer, a ferroelectric layer is provided over the buffer layer, and a dielectric layer is provided over the ferroelectric layer. A two-dimensional, 2D, material layer is provided over a portion of a top surface of the dielectric layer. Source and drain regions are provided on separate portions of the top surface of the dielectric layer so as to create a cavity wherein the 2D material layer is located.