MRAM Cell Lower Electrode Direct Coupling

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Solution Overview

Problem

Conventional magnetoresistive random-access memory (MRAM) cells require chemical mechanical planarization (CMP) operations, leading to increased manufacturing costs and defects, and have a larger height due to the use of contacts or vias between the lower electrode and underlying metal layers, making them less compatible with existing back-end-of-line (BEOL) metallization techniques.

Innovation Solution

The MRAM cell design eliminates the need for CMP by directly coupling the lower electrode to the underlying metal layer without using contacts or vias, reducing the overall height and simplifying the manufacturing process, thereby improving compatibility with BEOL processes and reducing defects and costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If contacts or vias are used between the lower electrode and underlying metal layers, then electrical connection is achieved, but the overall height increases and compatibility with BEOL metallization techniques decreases

Engineering Contradiction:

Improvecompatibility with BEOL metallization techniquesVSAvoidoverall height of MRAM cell

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The patent removes the contact or via structure from the MRAM cell design, allowing the lower electrode to directly contact the underlying metal layer. This extraction of the intermediate connection structure reduces the overall cell height and simplifies the manufacturing process while maintaining electrical connectivity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If CMP operations are used for planarization, then surface flatness is achieved, but manufacturing costs increase and defects are introduced

Engineering Contradiction:

Improvesurface flatnessVSAvoidmanufacturing cost and defect rate

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent eliminates the CMP process step from the manufacturing sequence by designing the lower electrode and underlying metal layer interface to not require planarization. This removal of the CMP operation reduces manufacturing complexity, lowers costs, and decreases the introduction of defects while still achieving the necessary surface quality for device operation.

Inventive Principle:

Principle #2Taking out (Extraction)

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 results in a more cost-effective and defect-reduced MRAM cell with a shorter profile, enhancing compatibility with existing BEOL flows and improving manufacturing yields.

Implementation Method 1

a magnetic tunnel junction (MTJ) arranged between the upper and lower electrodes

Methodology Applied

Scientific EffectQuantum tunneling:

Data Source

PatentUS11653572B2Manufacturing techniques and corresponding devices for magnetic tunnel junction devices

Publication Date: 2023.05.16 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Some embodiments relate to a magnetoresistive random-access memory (MRAM) cell. The cell includes a bottom electrode having a central bottom electrode portion surrounded by a peripheral bottom electrode portion. Step regions of the conductive bottom electrode couple the central and peripheral bottom electrode portions to one another such that an upper surface of the central portion is recessed relative to an upper surface of the peripheral portion. A magnetic tunneling junction (MTJ) has MTJ outer sidewalls which are disposed over the bottom central electrode portion and which are arranged between the step regions. A top electrode is disposed over an upper surface of the MTJ. Other devices and methods are also disclosed.