Etching Metal Multilayer Films with Ethylene Oxygen Plasma
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Solution Overview
Problem
The use of methanol gas plasma for etching metal multilayer films with magnetic tunnel junctions can deteriorate the electromagnetic characteristics due to hydrogen ions and radicals, and lacks sufficient selectivity between the metal film and non-organic masks.
Innovation Solution
An etching method using a mixed gas of ethylene and oxygen, with ethylene comprising 50% to 63% of the total gas mixture, to suppress deterioration of electromagnetic characteristics and achieve a sufficient selectivity ratio during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If methanol gas plasma is used for etching metal multilayer film, then etching capability is achieved, but electromagnetic characteristics of the metal multilayer film deteriorate due to hydrogen ions and radicals
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from methanol (CH3OH) to a mixed gas of ethylene (C2H4) and oxygen (O2). This parameter change reduces hydrogen content in the plasma while maintaining etching capability through carbon and oxygen species, thereby preventing hydrogen-induced deterioration of electromagnetic characteristics in the metal multilayer film.
Solution Approach 2:
The patent uses ethylene gas as a temporary etching medium that performs its function (etching the metal multilayer film) and is then discarded. The ethylene plasma provides necessary etching capability without leaving harmful residual effects on the magnetic tunnel junction, unlike methanol plasma which causes persistent electromagnetic characteristic deterioration.
2Productivity
If methanol gas plasma is used for etching, then etching process is performed, but selection ratio between metal multilayer film and non-organic mask is insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching gas to a mixed gas of ethylene and oxygen. The oxygen component enhances the chemical reactivity with the metal multilayer film while the ethylene provides carbon species for effective etching. This parameter change creates a plasma environment that achieves sufficient selection ratio between the metal multilayer film and non-organic mask, enabling precise pattern transfer.
3Reliability
If hydrogen content in etching gas is reduced, then deterioration of electromagnetic characteristics is suppressed, but etching capability may be compromised
Solution Approach 1:
The patent changes the gas composition parameters from hydrogen-rich methanol to a mixed gas of ethylene and oxygen. This parameter change maintains adequate hydrogen content for etching while introducing carbon and oxygen species that provide alternative etching mechanisms, thus suppressing electromagnetic characteristic deterioration while preserving etching capability.
Solution Approach 2:
The patent uses a composite gas mixture of ethylene and oxygen instead of a single gas component. The ethylene provides carbon species for etching, the oxygen enhances reactivity and selectivity, and the combination creates a synergistic plasma environment that achieves both suppressed electromagnetic characteristic deterioration and maintained etching capability.
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 effectively prevents the deterioration of electromagnetic characteristics and ensures a sufficient selectivity ratio, allowing for precise etching of metal multilayer films with magnetic tunnel junctions without generating an etching stop.
Implementation Method 1
etching the metal multilayer film by plasma of a mixed gas of ethylene gas and oxygen gas
Implementation Method 2
Ions and/or radicals of hydrogen and oxygen contained in methanol plasma affect the plasma etching of the metal multilayer film
Implementation Method 3
ions and/or radicals of hydrogen modify the metal multilayer film
Data Source
AI summary
An etching method includes: preparing a workpiece including a metal multilayer film having a magnetic tunnel junction and a mask formed by an inorganic material on the metal multilayer film; and etching the metal multilayer film by plasma of a mixed gas of ethylene gas and oxygen gas using the mask.