Layered Bottom Electrode for pMTJ Integration

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Solution Overview

Problem

The integration of high-yielding perpendicular magnetic random-access memory (MRAM) arrays with surrounding logic circuitry is challenging due to the need for a bottom electrode contact structure that promotes strong perpendicular magnetic anisotropy, minimizes device sidewall shorting, and allows for clean removal from non-memory regions.

Innovation Solution

A layered bottom electrode contact structure comprising a titanium-nitrogen layer for easy removal and a tantalum-nitrogen layer for promoting strong FCC crystal structure and perpendicular magnetic anisotropy, with oxygen presence to facilitate the growth of bottom-most layers in the magnetic tunnel junction (MTJ) stack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single-layer bottom electrode contact structure is used, then the device structure is simple, but it cannot simultaneously promote strong perpendicular magnetic anisotropy and allow for clean removal from non-memory regions

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoidremoval from non-memory regions

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The bottom electrode contact structure is divided into two distinct layers: a first conductive layer (titanium-nitrogen) that serves as an etch stop layer for clean removal from non-memory regions, and a second conductive layer (tantalum-nitrogen) that promotes strong perpendicular magnetic anisotropy and FCC crystal structure. This segmentation allows each layer to fulfill its specific function independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different materials are selected for different layers based on their local functional requirements. The titanium-nitrogen layer is optimized for etch selectivity and removal, while the tantalum-nitrogen layer is optimized for promoting magnetic anisotropy and crystal growth. This local quality approach ensures each layer performs its designated function effectively.

Inventive Principle:

Principle #3Local quality

2Reliability

If the bottom electrode material promotes strong perpendicular magnetic anisotropy, then the pMTJ device performance is improved, but it becomes difficult to remove cleanly from non-memory regions

Engineering Contradiction:

ImprovepMTJ device performanceVSAvoidclean removal

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The electrode structure is segmented into two layers with distinct material compositions and functions. The titanium-nitrogen layer provides easy removability through selective etching, while the tantalum-nitrogen layer provides the magnetic anisotropy promotion. This segmentation resolves the conflict between performance and manufacturability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The titanium-nitrogen layer acts as an intermediary between the substrate and the magnetic tunnel junction stack. It serves as a sacrificial etch stop layer that facilitates clean removal of the entire stack from non-memory regions without damaging underlying structures, while the tantalum-nitrogen layer maintains the magnetic properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If feature size is reduced for higher density, then chip capacity increases, but the integration of MRAM arrays with logic circuitry becomes more challenging

Engineering Contradiction:

Improvememory densityVSAvoidintegration with logic circuitry

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The removable bottom electrode structure is segmented into functionally distinct layers that can be selectively etched away from non-memory regions. This segmentation enables clean separation of MRAM arrays from surrounding logic circuitry, facilitating integration at smaller feature sizes without compromising manufacturing yield.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The etch selectivity parameter between the titanium-nitrogen layer and underlying structures is optimized to enable clean removal. By controlling the composition and thickness of the titanium-nitrogen layer, the structure can be selectively removed from non-memory regions even at reduced feature sizes, maintaining integration capability.

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 solution enables high tunneling magnetoresistance ratio, low switching voltage, and low write error rate in pMTJ devices while maintaining high yield and avoiding damage to existing logic circuitry.

Implementation Method 1

a first conductive layer that includes titanium and nitrogen... The first layer of titanium and nitrogen is a conductive material that is easy to remove from the substrate by a suitable etch process

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

promotes strong perpendicular magnetic anisotropy

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy:

Data Source

PatentUS11380838B2Magnetic memory devices with layered electrodes and methods of fabrication

Publication Date: 2022.07.05 INTEL CORP

AI summary

A memory device method of fabrication that includes a first electrode having a first conductive layer including titanium and nitrogen and a second conductive layer on the first conductive layer that includes tantalum and nitrogen. The memory device further includes a magnetic tunnel junction (MTJ) on the first electrode. In some embodiments, at least a portion of the first conductive layer proximal to an interface with the second conductive layer includes oxygen.