MFM Capacitor Seed Layer for Ferroelectric Phase Stability

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Solution Overview

Problem

Existing metal-ferroelectric-metal (MFM) capacitors face performance issues due to undesirable monoclinic phase transitions during post oxide deposition anneal operations, which negatively impact the stability of the orthorhombic polar phase and ferroelectricity.

Innovation Solution

Incorporating a seed layer with a preferred lattice constant as a templating layer to promote polar phase growth and stabilizing the oxide phase, followed by capping with a thin low-temperature metal layer to apply mechanical constraints and prevent phase transitions to non-polar phases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If post oxide deposition anneal operations are performed, then oxide deposition is completed, but undesirable monoclinic phase transitions occur that negatively impact ferroelectricity

Engineering Contradiction:

Improveoxide deposition completionVSAvoidferroelectricity stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A seed layer is formed on the bottom electrode before depositing the ferroelectric oxide layer. This seed layer promotes the formation of the desired orthorhombic polar phase during subsequent annealing operations, preventing monoclinic phase transitions before they can occur. The preliminary structural preparation ensures that when annealing is performed to complete oxide deposition, the ferroelectric phase is stabilized from the outset.

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If orthorhombic polar phase stabilization is attempted, then ferroelectricity is enhanced, but undesirable phase transitions still occur

Engineering Contradiction:

Improveorthorhombic polar phase stabilityVSAvoidmonoclinic phase transitions

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent modifies the structural parameters of the capacitor by introducing a seed layer with specific crystallographic properties and adjusting the composition of the ferroelectric oxide layer. These parameter changes alter the phase transition behavior during annealing, stabilizing the orthorhombic polar phase and suppressing monoclinic transitions. The modified parameters ensure that when thermal energy is applied during annealing, the desired phase is maintained rather than transitioning to harmful monoclinic phases.

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 effectively locks the oxide phase in a ferroelectric state, enhancing the strength of the ferroelectric layer and minimizing non-polar phase presence, thereby maximizing remnant polarization and memory window performance.

Implementation Method 1

Incorporating a seed layer with a preferred lattice constant as a templating layer to promote polar phase growth and stabilizing the oxide phase

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

capping with a thin low-temperature metal layer to apply mechanical constraints and prevent phase transitions to non-polar phases

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11901400B2MFM capacitor and process for forming such

Publication Date: 2024.02.13 SK HYNIX NAND PRODUCT SOLUTIONS CORP

AI summary

A capacitor is disclosed that includes a first metal layer and a seed layer on the first metal layer. The seed layer includes a polar phase crystalline structure. The capacitor also includes a ferroelectric layer on the seed layer and a second metal layer on the ferroelectric layer.