Ferroelectric Gate Stack with Seed Layer for Low-Leakage FeRAM

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Solution Overview

Problem

Current semiconductor devices, such as field effect transistor (FET) ferroelectric random access memories (FeRAMs), face challenges in enhancing remanent polarization and reducing oxygen vacancies and carrier leakage currents, which affect their performance and reliability.

Innovation Solution

The implementation of a seed layer to increase the orthorhombic phase fraction of the ferroelectric gate layer and a blocking layer to enhance band offset and reduce oxygen vacancies between the ferroelectric gate and channel layers, improving the device's properties and reducing charge carrier scattering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional ferroelectric gate layer is used without a seed layer, then the device structure is simpler, but the orthorhombic phase fraction is lower resulting in reduced remanent polarization

Engineering Contradiction:

Improveremanent polarizationVSAvoidlayer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A seed layer is formed on the metal layer before forming the ferroelectric gate layer. The seed layer is arranged to increase the orthorhombic phase fraction of the ferroelectric gate layer, preparing the substrate in advance to promote desirable crystal phase formation and enhance remanent polarization.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The seed layer acts as an intermediary between the metal layer and the ferroelectric gate layer. It mediates the crystal growth process by promoting the orthorhombic phase formation in the ferroelectric gate layer, thereby improving remanent polarization without requiring changes to the ferroelectric material composition.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If no blocking layer is used between the ferroelectric gate and channel layers, then the device structure is simpler, but oxygen vacancies and carrier leakage currents increase

Engineering Contradiction:

Improvecarrier leakage currentVSAvoidlayer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A blocking layer is disposed on the ferroelectric gate layer and beneath the channel layer. This blocking layer serves as an intermediary that increases the band offset between the ferroelectric gate and channel layers, thereby reducing carrier leakage currents and improving device reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The blocking layer converts the potentially harmful effect of oxygen vacancies and band alignment issues into a benefit by providing a controlled interface that manages carrier transport. The layer is arranged to increase band offset, transforming the interface into a beneficial barrier against carrier leakage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the band offset between ferroelectric gate and channel layers is low, then carrier transport is easier, but carrier leakage currents increase reducing device reliability

Engineering Contradiction:

Improvedevice enduranceVSAvoidcharge carrier scattering

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The blocking layer is arranged to increase the band offset between the ferroelectric gate and channel layers. By changing the electrical parameter (band offset) at the interface, the device achieves better control over carrier leakage currents, improving reliability and endurance.

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

This approach increases remanent polarization, reduces carrier leakage currents, and enhances the reliability of FeRAMs by improving the band offset and reducing oxygen vacancies, leading to better performance and endurance.

Implementation Method 1

a seed layer to increase the orthorhombic phase fraction of the ferroelectric gate layer

Methodology Applied

Scientific EffectPhase transition: Phase Change

Implementation Method 2

a blocking layer to enhance band offset and reduce oxygen vacancies between the ferroelectric gate and channel layers

Methodology Applied

Scientific EffectBand offset effect:

Implementation Method 3

Field effect transistor (FET) ferroelectric random access memories (FeRAMs) are semiconductor devices which operate based on a ferroelectric material in the devices

Methodology Applied

Scientific EffectFerroelectricity:

Data Source

PatentUS12119402B2Semiconductor devices with ferroelectric layer and methods of manufacturing thereof

Publication Date: 2024.10.15 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device is described. The semiconductor device includes a substrate and a metal layer disposed on the substrate. A seed layer is formed on the metal layer. A ferroelectric gate layer is formed on the seed layer. A channel layer is formed over the ferroelectric gate layer. The seed layer is arranged to increase the orthorhombic phase fraction of the ferroelectric gate layer.