MRAM SOT Interconnect Structure for Low-Resistance BEOL Contact

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional magnetoresistive random access memory (MRAM) devices face limitations in contact area and interconnection resistance, which affect driving current and device performance, and are prone to damage during the back-end-of-line (BEOL) process, impacting yield and reliability.

Innovation Solution

The MRAM device features a structure where the upper metal line is directly landed on the second SOT layer, increasing contact area and reducing interconnection resistance, and includes an etch stop layer made of SiN to prevent damage during the BEOL process, using materials like TiN for the second SOT layer and Ta, TaN, or Pt for the cap layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the upper metal line is directly landed on the second SOT layer, then the contact area between the upper metal line and the second SOT layer is increased, but the risk of damaging the second SOT layer during BEOL process increases

Engineering Contradiction:

Improvecontact area between upper metal line and second SOT layerVSAvoidintegrity of second SOT layer

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

An etch stop layer is introduced as an intermediary protective layer between the second SOT layer and the upper metal line. This etch stop layer prevents direct contact and potential damage to the second SOT layer during BEOL processing, while still allowing the upper metal line to be positioned directly over the second SOT layer to maximize contact area. The etch stop layer acts as a mediator that protects the underlying SOT layer from etching damage while maintaining the desired electrical connection geometry.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Length of moving object

If the upper metal line is directly landed on the second SOT layer, then the electrical path between the second SOT layer and FEOL transistors is shortened, but the interconnection resistance may increase due to potential damage to the second SOT layer

Engineering Contradiction:

Improveelectrical path length between second SOT layer and FEOL transistorsVSAvoiddevice performance stability

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The etch stop layer serves as a protective intermediary that enables the upper metal line to be positioned directly over the second SOT layer, shortening the electrical path length. Simultaneously, this etch stop layer prevents etching damage to the second SOT layer during BEOL processing, ensuring the integrity and stability of the magnetic tunnel junction structure and maintaining reliable device performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the etch stop layer is formed on the second SOT layer, then the second SOT layer is protected from damage during BEOL process, but the manufacturing steps increase

Engineering Contradiction:

Improveprotection of second SOT layer during BEOL processVSAvoidnumber of manufacturing steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The etch stop layer is formed on the second SOT layer before performing the BEOL process. This preliminary protective action prevents damage to the second SOT layer during subsequent etching operations. The etch stop layer is deposited as a thin film layer that provides protection throughout the BEOL manufacturing steps, ensuring the integrity of the underlying magnetic tunnel junction structure.

Inventive Principle:

Principle #10Preliminary action

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 configuration enhances driving current, shortens electrical paths, reduces manufacturing costs, and improves device performance and reliability by increasing the contact area and protecting the SOT layer from damage during the BEOL process.

Implementation Method 1

the upper metal line is directly landed on the second SOT layer to increase the contact area between the upper metal line and the second SOT layer, thereby increasing the driving current

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Implementation Method 2

the etch stop layer is formed on the second SOT layer to prevent from damaging the second SOT layer due to the formation of trenches or vias in the subsequent back-end-of-line (BEOL) process

Methodology Applied

Scientific EffectEtch stopping:

Implementation Method 3

Magnetoresistive random access memory does not use traditional electric charge to store bit information, but uses magnetoresistance effect to store data

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS20240032441A1Magnetoresistive random access memory (MRAM) device and method of forming the same

Publication Date: 2024.01.25 UNITED MICROELECTRONICS CORP

AI summary

Provided is a magnetoresistive random access memory (MRAM) device including a bottom electrode, a magnetic tunnel junction (MTJ) structure, a first spin orbit torque (SOT) layer, a cap layer, a second SOT layer, an etch stop layer, and an upper metal line layer. The MTJ structure is disposed on the bottom electrode. The first SOT layer is disposed on the MTJ structure. The cap layer is disposed on the first SOT layer. The second SOT layer is disposed on the cap layer. The etch stop layer is disposed on the second SOT layer. The upper metal line layer penetrates though the etch stop layer and is landed on the second SOT layer.