FeFET Dual Passivation Interface for Uniform Ferroelectric Switching

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Solution Overview

Problem

Conventional ferroelectric field effect transistors (FeFETs) face challenges in achieving uniform ferroelectric characteristics due to interfacial excess metal ions and varying oxygen concentrations at the ferroelectric and metal oxide semiconductor interface, leading to instability and non-uniform switching.

Innovation Solution

The implementation of an interfacial dual passivation layer comprising a metal-rich metal oxide layer and a dielectric metal nitride layer, formed through nitridation treatment or deposition processes, to stabilize the interface and reduce metal-metal coordination, thereby enhancing ferroelectric switching and device uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional ferroelectric interface is used without passivation, then device structure is simpler, but ferroelectric characteristics are non-uniform and unstable due to interfacial excess metal ions and varying oxygen concentrations

Engineering Contradiction:

Improveferroelectric characteristics stabilityVSAvoidinterface structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces an interfacial passivation layer as an intermediary between the ferroelectric layer and the metal oxide semiconductor layer. This passivation layer mediates the interface by reducing metal-metal coordination and stabilizing oxygen concentrations, thereby improving ferroelectric characteristics without directly modifying the bulk materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite interface structure consisting of multiple materials (ferroelectric material, passivation layer, and metal oxide semiconductor) working together. The passivation layer is specifically engineered with properties that bridge the ferroelectric and semiconductor layers, creating a composite system that achieves both structural stability and enhanced ferroelectric performance.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If interfacial passivation layer is added to stabilize the interface, then ferroelectric switching uniformity is improved, but manufacturing process complexity increases

Engineering Contradiction:

Improveferroelectric switching uniformityVSAvoidinterface fabrication ease

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The passivation layer is formed preliminarily at the interface between the ferroelectric and metal oxide semiconductor layers before final device assembly. This preliminary action of creating a stable interface early in the fabrication process prevents subsequent issues with metal ion migration and oxygen variation, ensuring uniform ferroelectric switching characteristics.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If metal-rich metal oxide layer and dielectric metal nitride layer are deposited to form dual passivation, then interface stability is enhanced, but deposition process time and complexity increase

Engineering Contradiction:

Improveinterface composition stabilityVSAvoiddeposition process time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The passivation layer is segmented into two distinct functional layers: a metal-rich metal oxide layer that reduces metal-metal coordination, and a dielectric metal nitride layer that provides additional interface stabilization. This segmentation allows each layer to perform its specific function efficiently, achieving superior interface stability through coordinated action of specialized sub-layers.

Inventive Principle:

Principle #1Segmentation

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 interfacial dual passivation layer stabilizes the ferroelectric characteristics, reduces variability, and facilitates uniform switching, improving the stability and endurance of ferroelectric memory devices by reducing energy barriers and operational voltage.

Implementation Method 1

The interfacial dual passivation layer may include a metal-rich metal oxide layer and a dielectric metal nitride layer formed over the metal-rich metal oxide layer

Methodology Applied

Scientific EffectNitridation: Nitriding

Implementation Method 2

The metal-rich metal oxide layer may include a non-stoichiometric and metal-rich oxide

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS12051749B2Interfacial dual passivation layer for a ferroelectric device and methods of forming the same

Publication Date: 2024.07.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor structure includes, from bottom to top or from top to bottom, a gate electrode, a ferroelectric dielectric layer, a metal-rich metal oxide layer, a dielectric metal nitride layer, and a metal oxide semiconductor layer. A ferroelectric field effect transistor may be provided by forming a source region and a drain region on the metal oxide semiconductor layer. The metal-rich metal oxide layer and the dielectric metal nitride layer homogenize and stabilize the interface between the ferroelectric dielectric layer and the metal oxide semiconductor layer, and reduce excess oxygen atoms at the interface, thereby improving switching characteristics of the ferroelectric field effect transistor.