Ferroelectric Memory Stack with Oxidized Electrode Interface Retention

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Solution Overview

Problem

Current semiconductor devices with ferroelectric dielectric materials face challenges in achieving long retention times and high switching speeds, particularly in data storage applications where film stacks require improved reliability and retention performance.

Innovation Solution

A method is developed that involves forming a retention enhancement layer on a lower electrode layer using a gas phase oxidation process, followed by depositing a ferroelectric high-k metal oxide layer, such as hafnium zirconium oxide, in direct physical contact with the enhancement layer using vapor deposition, to enhance the retention performance and reliability of the ferroelectric device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional ferroelectric film stack is used without additional retention enhancement layers, then the device structure remains simple, but the retention time and reliability are insufficient for advanced memory applications

Engineering Contradiction:

Improveretention performanceVSAvoidfilm stack structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the electrode structure into multiple functional segments: a lower electrode layer, a retention enhancement layer with specific oxidation states, and a ferroelectric layer. This segmentation allows each layer to perform its specialized function independently, improving overall retention performance while maintaining manageable structural complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The retention enhancement layer is formed in advance before depositing the ferroelectric layer. The gas phase oxidation process creates a pre-conditioned interface with specific oxygen vacancies and oxidation states that prepare the surface for optimal ferroelectric layer adhesion and charge retention, preventing subsequent degradation

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the ferroelectric layer is deposited directly on the lower electrode without a retention enhancement layer, then the manufacturing process is simpler, but the switching speed and retention time deteriorate

Engineering Contradiction:

Improveswitching speedVSAvoidfabrication process

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent modifies the oxidation state parameters of the retention enhancement layer through controlled gas phase oxidation. By adjusting oxygen exposure conditions, the layer achieves optimal oxidation states that facilitate fast charge switching while maintaining manufacturing feasibility through standard semiconductor processing techniques

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The retention enhancement layer acts as an intermediary between the lower electrode and the ferroelectric layer. It mediates the interaction by providing a controlled interface that enhances charge transfer efficiency and switching speed without requiring complex direct contact structures

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If extensive oxidation is applied to the lower electrode surface, then the retention performance improves, but the electrode material may deteriorate or form excessive oxide layers

Engineering Contradiction:

Improveretention performanceVSAvoidelectrode integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies partial oxidation to the lower electrode surface, creating a retention enhancement layer with controlled thickness and oxidation state. This partial action is sufficient to improve retention performance by creating the necessary interface conditions without over-oxidizing the electrode and compromising its electrical conductivity and structural integrity

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent uses gas phase oxidation with controlled oxygen exposure to accelerate the formation of the retention enhancement layer. This controlled accelerated oxidation achieves the desired retention performance while precisely limiting the oxidation extent to preserve electrode strength, avoiding the need for prolonged or excessive oxidation processes

Inventive Principle:

Principle #38Strong oxidants (Accelerated oxidation)

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 approach results in improved retention performance and reliability of ferroelectric memory devices, maintaining high switching speeds and long retention times, suitable for advanced memory applications like FRAM, NVRAM, and DRAM.

Implementation Method 1

forming a retention enhancement layer by oxidizing a surface of the lower electrode layer using a gas phase oxidation process

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

depositing a ferroelectric high-k metal oxide layer over the retention enhancement layer using a vapor deposition process

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS20240128308A1Method for fabricating a ferroelectric device

Publication Date: 2024.04.18 TOKYO ELECTRON LTD

AI summary

A method for fabricating a ferroelectric device includes providing a lower electrode layer on a substrate, forming a retention enhancement layer by oxidizing a surface of the lower electrode layer using a gas phase oxidation process, and depositing a ferroelectric high-k metal oxide layer over the retention enhancement layer on the lower electrode layer using a vapor deposition process. The retention enhancement layer on the lower electrode layer increases the retention performance and reliability of the ferroelectric device.