MTJ Pillar Etching via Alternating Ion Beam and Reactive Ion Processes

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Solution Overview

Problem

Conventional manufacturing processes for MTJ pillars in MRAM devices face challenges in achieving high density and quality due to re-deposition of conductive materials at the edges of the tunnel barrier layer, which shorts the junction and compromises device performance, and high angle ion beam cleaning damages the thin layers.

Innovation Solution

A method combining thin insulator layers and alternating steps of ion beam etching and reactive ion etching to define MTJ pillars, reducing re-deposition and edge damage, and using a protective insulating layer to prevent shunts and enable high-density pillar formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If high angle ion beam cleaning is used to remove re-deposited material, then the barrier layer edges are cleaned, but the device density is limited and beam damage increases

Engineering Contradiction:

Improvecleanliness of barrier layer edgesVSAvoiddevice density

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

A protective insulating layer is deposited conformally on the MTJ pillar structure before etching, preventing re-deposited conductive material from reaching and shorting the barrier layer edges. This preliminary protective action eliminates the need for subsequent high angle ion beam cleaning, allowing higher device density without beam damage concerns

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective insulating layer acts as an intermediary barrier between the re-deposited conductive material and the barrier layer edges. This intermediate layer prevents direct contact and electrical shorting, enabling the use of conventional etching processes without requiring damaging high angle cleaning steps

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If conventional etching is used to form MTJ pillars, then material is removed efficiently, but re-deposited conductive material shorts the barrier layer

Engineering Contradiction:

Improveetching efficiencyVSAvoidtunnel junction functionality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A conformal protective insulating layer is deposited on the MTJ pillar structure before the etching process, pre-preventing re-deposited conductive material from reaching the barrier layer. This allows efficient conventional etching to proceed without compromising tunnel junction functionality

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective insulating layer serves as an intermediary barrier that intercepts re-deposited conductive material during etching, preventing it from shorting the barrier layer edges and maintaining tunnel junction functionality while allowing efficient material removal

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If high angle ion beam cleaning is performed to remove re-deposited material, then conductive shorts are prevented, but beam damage to thin MTJ layers increases

Engineering Contradiction:

Improveprevention of conductive shortsVSAvoidbeam damage to MTJ layers

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The protective insulating layer acts as an intermediary shield that blocks re-deposited conductive material from reaching the barrier layer, preventing conductive shorts without requiring high angle ion beam cleaning that would cause beam damage to the thin MTJ layers

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The conformal protective insulating layer, which would normally be considered an additional process step, actually converts the harmful re-deposited material into a benign situation by preventing it from causing shorts, thereby eliminating the need for damaging high angle cleaning

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 method eliminates the need for high angle ion beam cleaning, reduces material re-deposition, and enhances MTJ pillar density and performance by preventing shorts and damage to the tunnel junction, allowing for the use of current process tooling and technology.

Implementation Method 1

alternating steps of reactive ion etching and ion beam etching are performed to isolate MTJ pillars and expose side surfaces of the MTJ layers

Methodology Applied

Scientific EffectIon beam etching: Ion Beam

Implementation Method 2

alternating steps of reactive ion etching and ion beam etching are performed to isolate MTJ pillars

Methodology Applied

Scientific EffectReactive ion etching: Plasma

Implementation Method 3

the device is planarized using chemical mechanical polishing

Methodology Applied

Scientific EffectChemical mechanical polishing:

Data Source

PatentUS9406876B2Method for manufacturing MTJ memory device

Publication Date: 2016.08.02 INTEGRATED SILICON SOLUTION CAYMAN INC

AI summary

A method for manufacturing MTJ pillars for a MTJ memory device. The method includes depositing multiple MTJ layers on a substrate, depositing a hard mask on the substrate and coating a photoresist on the hard mask. Further, alternating steps of reactive ion etching and ion beam etching are performed to isolate MTJ pillars and expose side surfaces of the MTJ layers. An insulating layer is the applied to protect the side surfaces of the MTJ layers. A second insulating layer is deposited before the device is planarized using chemical mechanical polishing.