Ferroelectric Memory Electrodes for O-Phase Stability After Cycling

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Solution Overview

Problem

The retention after cycling (RAC) memory window (MW) performance of ferroelectric random-access memory (FeRAM) devices degrades with the scaling down of device dimensions due to challenges in maintaining the formation and stability of the orthorhombic phase (O-phase) ferroelectric material.

Innovation Solution

Incorporating nitrogen-rich top and bottom electrodes with a specific nitrogen-to-metal ratio and crystal orientation in the ferroelectric layer, followed by an anneal process, to enhance the formation and stabilization of the O-phase ferroelectric material, thereby improving RAC MW performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If device dimensions are scaled down to increase storage capacity and processing speed, then productivity and speed are improved, but the stability and formation of O-phase ferroelectric material deteriorates

Engineering Contradiction:

Improvestorage capacityVSAvoidO-phase ferroelectric material stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent changes the compositional parameters of the electrode materials by incorporating nitrogen-rich metal nitrides with specific nitrogen-to-metal ratios (greater than 0.8). This parameter change in electrode composition induces beneficial stress and chemical effects that stabilize the O-phase ferroelectric material even in scaled-down devices, resolving the contradiction between miniaturization and phase stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite electrode structures made of nitrogen-rich metal nitrides (such as TiN, TaN, WN) combined with other materials. These composite electrodes provide both the electrical conductivity needed for device operation and the mechanical/chemical properties necessary to stabilize the O-phase ferroelectric material at smaller dimensions, thereby maintaining reliability while increasing storage capacity.

Inventive Principle:

Principle #40Composite materials

2Productivity

If device dimensions are scaled down, then storage capacity is improved, but the retention after cycling performance deteriorates

Engineering Contradiction:

Improvestorage capacityVSAvoidretention after cycling performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

By adjusting the nitrogen-to-metal ratio in the electrode materials to be greater than 0.8, the patent optimizes the electrode composition to provide enhanced stability and reduced degradation during cycling. This parameter change ensures that even when devices are scaled down for higher storage capacity, the retention performance after 10,000 read/write cycles remains high.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The nitrogen-rich metal nitride electrodes act as intermediary layers between the external circuitry and the ferroelectric material. These intermediary electrodes protect the ferroelectric material from degradation during cycling while maintaining electrical functionality, thus preserving retention performance in scaled-down devices with higher storage capacity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If conventional electrodes are used, then manufacturing is simpler, but the RAC MW performance degrades after cycling

Engineering Contradiction:

Improveelectrode fabrication simplicityVSAvoidRAC MW performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent modifies the electrode material parameters by incorporating nitrogen-rich metal nitrides with controlled nitrogen-to-metal ratios. While this requires additional process steps compared to conventional electrodes, the performance improvement in RAC MW retention after 10,000 cycles justifies the enhanced manufacturing complexity, achieving reliable high-capacity storage.

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

The RAC MW performance of FeRAM devices is enhanced, maintaining high performance after 10,000 read/write cycles compared to degradation after 1000 cycles without the nitrogen-rich electrodes.

Implementation Method 1

The first electrode includes a nitrogen-rich metal nitride material that induces a concentration of the O-phase in the high-k dielectric material

Methodology Applied

Scientific EffectStress-induced phase formation:

Implementation Method 2

an anneal process, to enhance the formation and stabilization of the O-phase ferroelectric material

Methodology Applied

Scientific EffectAnnealing: Annealing

Data Source

PatentUS20250344397A1Ferroelectric memory device and method of fabricating the same

Publication Date: 2025.11.06 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure describes a semiconductor device having a ferroelectric memory with improved retention after cycling (RAC) memory window (MW) performance. The semiconductor device includes an interconnect structure on a substrate, a first electrode on the interconnect structure, a ferroelectric layer on the first electrode, and a second electrode on the ferroelectric layer. The first electrode includes a metal nitride conductive material having a nitrogen concentration greater than a metal concentration. The ferroelectric layer includes a ferroelectric material. The second electrode includes the metal nitride conductive material.