Dry Plasma Etch Method for MRAM Stack Patterning

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Solution Overview

Problem

Current semiconductor fabrication techniques face challenges in etching non-volatile metals for MRAM structures, particularly in preventing sidewall re-deposition and damage to exposed layers, which leads to defects and device failure due to the re-deposition of etched byproducts.

Innovation Solution

A method involving a dry plasma etch system that uses a halogen-containing gas and a reactive material like silicon or titanium to form volatile species, combined with atomic layer deposition and etch techniques, to etch non-volatile metals without sidewall re-deposition and damage, ensuring precise etch rate control and conformality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional etching techniques are used to etch non-volatile metals, then etching can be performed, but etched byproducts re-deposit onto exposed regions causing defects and device failure

Engineering Contradiction:

Improvedevice reliabilityVSAvoidre-deposition of etched byproducts

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A silicon-containing material is introduced as an intermediary substance that reacts with halogen-containing gas to form volatile silicon halide species. This intermediary reacts with metal etch byproducts to form volatile compounds that can be easily removed, preventing re-deposition on sidewalls and exposed regions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The etching process uses parameter changes by alternating between halogen-containing gas exposure (to form volatile species) and activation gas exposure (to enable etching). This cyclic parameter change allows control over the etching reaction to minimize byproduct formation and re-deposition.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If etching is performed on MRAM stack layers, then material removal is achieved, but sidewall re-deposition occurs causing tapered profiles and shorting

Engineering Contradiction:

Improveetch profile precisionVSAvoidsidewall re-deposition

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The silicon-containing material serves as a mediator that forms volatile silicon halide compounds during etching. These volatile species prevent metal byproducts from adhering to sidewalls, maintaining vertical profiles and preventing the tapered shapes that lead to shorting defects.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The process converts the potentially harmful re-deposition issue into a benefit by using the silicon-containing material to deliberately form a volatile protective layer on sidewalls. This layer actually prevents the harmful re-deposition of metal byproducts while the volatile silicon halide species are easily pumped away.

Inventive Principle:

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

3Productivity

If halogen-containing gas is used for etching, then etching capability is improved, but damage to exposed layers occurs

Engineering Contradiction:

Improveetching rateVSAvoiddamage to exposed layers

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The silicon-containing material acts as a protective intermediary that is deposited on exposed layers before halogen-containing gas exposure. This silicon layer reacts with the halogen gas to form volatile silicon halide species, protecting the underlying sensitive MRAM layers from direct halogen exposure and damage while still allowing controlled etching of metal layers.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively prevents sidewall re-deposition and damage, achieving precise etch rate control and uniformity, thereby enhancing the reliability and scalability of MRAM devices by forming stable volatile etch products that can be easily removed.

Implementation Method 1

providing to the chamber a reactive material that is reactive with both the halogen-containing gas and a material of the one or more layers on the substrate to form a volatile species

Methodology Applied

Scientific EffectVolatile species formation:

Implementation Method 2

exposing the substrate to an activation gas and an activation source to etch one or more layers on the substrate

Methodology Applied

Scientific EffectPlasma activation: Plasma

Implementation Method 3

The reactive material is deposited conformally

Methodology Applied

Scientific EffectConformal deposition: Deposition (physical)

Implementation Method 4

The reactive material is deposited by a self-limiting reaction

Methodology Applied

Scientific EffectSelf-limiting reaction:

Data Source

PatentUS10749103B2Dry plasma etch method to pattern MRAM stack

Publication Date: 2020.08.18 LAM RES CORP

AI summary

Apparatuses for etching metal by depositing a material reactive with a metal to be etched and a halogen to form a volatile species and exposing the substrate to a halogen-containing gas and activation gas to etch the substrate are provided. Deposited materials may include silicon, germanium, titanium, carbon, tin, and combinations thereof. Apparatuses are suitable for fabricating MRAM structures and may be used to integrate ALD and ALE processes without breaking vacuum.