MTJ Element Sidewall Insulation via Dual Underlayer Oxidation
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Solution Overview
Problem
Magnetic Tunnel Junction (MTJ) elements in MRAM face challenges with corrosion and dielectric breakdown during processing due to low corrosion resistance and re-deposition issues during ion milling, which complicates the etching and leads to short circuits.
Innovation Solution
The MTJ element is structured with a dual underlayer configuration, where the first underlayer has a material with a small spin pumping effect and the second underlayer is oxidizable, with an insulating deposition layer formed on the sidewalls using inert gas ion milling and subsequent oxidation or nitridation, ensuring high breakdown voltage and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ion milling with Ar ion is used to process the MTJ element, then the MTJ element can be etched, but a leak current is passed through the tunnel barrier layer due to re-adhesion of spattered atoms causing dielectric breakdown
Solution Approach 1:
A protective film comprising a first film (e.g., W, Pt, or Pd) and a second film (e.g., SiO2, Si3N4, or SiON) is introduced as an intermediary layer between the MTJ element and the ion milling process. The protective film absorbs the harmful effects of ion milling, preventing direct damage to the tunnel barrier layer while allowing controlled etching of the MTJ element through the protective film using the MTJ element itself as an etch mask.
2Ease of manufacture
If RIE using halogen gas is used to process the MTJ element, then etching can be performed, but corrosion problem is generated due to low corrosion resistance of the MTJ element
Solution Approach 1:
The protective film serves as a mediator that enables RIE processing with halogen gas while preventing direct contact between the corrosive gas and the MTJ element. The protective film is selectively removed after etching, leaving the MTJ element intact without corrosion damage.
3Device complexity
If the MTJ element is processed without protective measures, then the processing is simpler, but short circuits occur due to re-deposition layer causing dielectric breakdown
Solution Approach 1:
The protective film is formed in advance before the ion milling or RIE process. This preliminary protective layer prevents re-deposition of spattered atoms directly onto the MTJ element, eliminating the source of dielectric breakdown while maintaining processing simplicity.
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 configuration reduces write current, maintains high magnetoresistance ratio, and prevents insulation defects, allowing for effective processing of MTJ elements without short circuits or dielectric breakdown.
Implementation Method 1
an insulating deposition layer formed on the sidewalls using inert gas ion milling and subsequent oxidation or nitridation
Implementation Method 2
an insulating deposition layer formed on the sidewalls using inert gas ion milling and subsequent oxidation or nitridation
Implementation Method 3
ion milling in which an Ar ion of an inert gas is used to process the MTJ element
Implementation Method 4
An MTJ (Magnetic Tunnel Junction) element is used as a magnetoresistance element of an MRAM (Magnetic Random Access Memory)
Data Source
AI summary
A magnetoresistance element includes a first magnetic layer having first and second surfaces, a second magnetic layer, an intermediate layer provided between the first surface and the second magnetic layer, a first layer provided on the second surface, containing B and at least one element selected from Hf, Al, Mg, and Ti and having third and fourth surfaces, a second layer provided on the fourth surface and containing B and at least one element selected from Hf, Al, and Mg, and an insulating layer provided on a sidewall of the intermediate layer and containing at least one element selected from the Hf, Al, and Mg contained in the second layer.