MRAM Sidewall Protection via Segmented Etching and Sacrificial Plugs

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Solution Overview

Problem

In the formation of magnetoresistive random-access memory (MRAM) devices, existing technologies face challenges in minimizing the exposure of sidewalls to sputtered metallic deposition and plasma, which can lead to electrical shorts and damage to the tunnel oxide layer, particularly due to the high aspect ratio of etched spaces and the magnetic nature of sidewalls formed during etching.

Innovation Solution

A method is developed to form MRAM devices by individually etching each layer and filling the gaps before subsequent etches, minimizing exposure to etch plasma and reducing sidewall formation, using a process that includes forming bottom, magnetic junction, and top electrode assemblies with specific layer deposition and masking steps, followed by planarization, to prevent electrical interference and damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple metal layers are sequentially etched through conventional processes, then the MRAM device structure is formed, but sidewalls are exposed to sputtered metallic deposition and plasma causing electrical shorts and tunnel oxide damage

Engineering Contradiction:

Improvedevice reliabilityVSAvoidsidewall exposure to sputtered metal and plasma

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the etching process into separate sequential etches for each metal layer (first metal layer, second metal layer, third metal layer) rather than etching all layers simultaneously. This segmentation allows the formation of sacrificial plugs between layers, which isolate sidewalls from harmful sputtered metal deposition and plasma exposure during subsequent etching steps, thereby preventing electrical shorts and tunnel oxide damage while maintaining device reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces sacrificial plugs as intermediary structures formed between metal layers. These plugs act as protective barriers that prevent direct exposure of sidewalls to sputtered metallic deposition and plasma during sequential etching processes. The sacrificial plugs are temporarily present during manufacturing and are later removed, having served their protective function throughout the fabrication process

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If conventional sequential etching is used without intermediate steps, then manufacturing process is simpler, but electrical shorts and tunnel oxide damage occur

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoiddevice reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The manufacturing process is segmented into distinct sequential etching steps for each metal layer, with intermediate sacrificial plug formation steps. While this increases the number of process steps compared to conventional single-step etching, each segment is designed to be straightforward and modular, maintaining ease of manufacture while dramatically improving device reliability by preventing electrical shorts and oxide damage

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sacrificial plugs are formed in advance (preliminarily) before the sequential etching of subsequent metal layers begins. This preliminary action prepares the structure to withstand the harmful effects of sputtered metal and plasma exposure during etching, ensuring reliability is maintained throughout the manufacturing process without requiring complex real-time adjustments

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 approach reduces the risk of electrical shorts and tunnel oxide damage, improving the reliability and performance of MRAM devices by minimizing sidewall exposure to sputtered metallic deposition and plasma, thereby enhancing device functionality.

Implementation Method 1

minimizing the exposure of sidewalls to sputtered metallic deposition and plasma

Methodology Applied

Scientific EffectPlasma: Plasma

Implementation Method 2

minimizing the exposure of sidewalls to sputtered metallic deposition

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS8895323B2Method of forming a magnetoresistive random-access memory device

Publication Date: 2014.11.25 LAM RES CORP

AI summary

A method for forming MRAM (magnetoresistive random access memory) devices is provided. A bottom electrode assembly is formed. A magnetic junction assembly is formed, comprising, depositing a magnetic junction assembly layer over the bottom electrode assembly, forming a patterned mask over the magnetic junction assembly layer, etching the magnetic junction assembly layer to form the magnetic junction assembly with gaps, gap filling the magnetic junction assembly, and planarizing the magnetic junction assembly. A top electrode assembly is formed.