MRAM Magnetic Tunnel Junction Etching With RIE-IBE Sequencing
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Solution Overview
Problem
Existing etching methods for MRAM magnetic tunnel junctions struggle to simultaneously achieve high profile maintenance, prevent sidewall contamination, and minimize residual deposition, especially in small-sized and dense patterns, which affects the performance and longevity of TMR and increases the risk of short circuits.
Innovation Solution
A combined method of reactive ion etching (RIE) and ion beam etching (IBE) with specific etching sequences and parameter selection, including large- and small-angle ion beam etching, followed by a cleaning step and in-situ protection with a dielectric film, to enhance the etching of non-dense and small-sized magnetic tunnel junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional IBE etching is used, then selectivity is improved, but magnesium oxide layer is damaged greatly and residual deposition increases
Solution Approach 1:
The etching process is divided into multiple sequential steps with different parameters: a first etching step with higher selectivity followed by a second etching step with lower selectivity but better profile control. This segmentation allows each step to optimize for its specific function, resolving the contradiction between selectivity and layer integrity.
Solution Approach 2:
The patent employs dynamic adjustment of etching parameters including ion beam angle (changing from oblique to normal incidence), power density, and gas flow rates between etching steps. This dynamic parameter optimization enables maintenance of magnesium oxide layer integrity while achieving high selectivity.
2Quantity of substance
If smaller and denser MTJ junction patterns are used, then spin-polarized current is reduced, but etching difficulty and sidewall contamination increase
Solution Approach 1:
The patent applies localized quality control by using oblique ion beam incidence during the first etching step to specifically protect sidewalls of small-sized patterns, while maintaining etching precision through normal incidence in the second step. This local quality approach enables high-precision etching of dense patterns without excessive sidewall contamination.
3Productivity
If conventional IBE or RIE etching is used, then etching speed is maintained, but profile quality and device survival rate decrease
Solution Approach 1:
The patent implements periodic action through alternating etching steps with different ion beam angles and parameters. The first step uses oblique incidence for profile formation, followed by a second step with normal incidence for precision etching. This periodic parameter variation maintains overall etching speed while significantly improving device survival rate through better profile control and reduced damage.
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
The method improves the etching effect of small-sized dense magnetic tunnel junctions, enhances the TMR performance, prolongs the device's service life, and reduces sidewall contamination and residual deposition, resulting in a more reliable MRAM structure.
Implementation Method 1
IBE uses an ion beam with certain energy to bombard the material surface for etching
Implementation Method 2
IBE uses an ion beam with certain energy to bombard the material surface for etching
Implementation Method 3
RIE is a method of etching by a chemical reaction and a physical ion bombardment
Data Source
AI summary
A method for etching an MRAM magnetic tunnel junction. The method includes performing a main etching step with an etching amount of t1 by using ion beam etching and/or reactive ion etching, wherein the direction angle of an ion beam is 10°-60°, and the bias voltage of the reactive ion etching is 400 V-1000 V; performing a cleaning step with an etching amount of t2, wherein the bias voltage of the reactive ion etching is 50 V-400 V, the pulse duty ratio is 5%-50%, t1:t2≥0.5, and after the cleaning step is completed, the etching morphology on a bottom electrode or a bottom dielectric layer is square trench; and performing in-situ protection, involving performing in-situ protection on a coating film. RIE is combined with IBE, and by means of the arrangement of an etching sequence and the selection of etching parameters, the the etching effect of small-sized dense magnetic tunnel junctions is significantly improved.