MRAM Metal Oxide Etching Stopper for Downsizing
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Solution Overview
Problem
Conventional magnetic random access memory (MRAM) technologies face challenges in downsizing due to difficulties in processing magnetic tunnel junction (MTJ) films, particularly with etching selectivity and overetching issues, which affect the reliability and design of the memory cells.
Innovation Solution
The proposed solution involves forming a magnetic random access memory with a metal oxide insulating film around the lower electrode layer, which is oxidized to create an etching stopper layer, allowing for precise etching of the MTJ film without overetching and enabling closer packing of cells, thus eliminating the need for separate processing of the lower electrode layer and MTJ film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If physical etching is used to process the MTJ film, then the etching process is simple, but the etching selectivity to the lower interlayer dielectric film is low causing large etching damage during overetching
Solution Approach 1:
A metal oxide insulating film is introduced as an intermediary layer between the lower electrode layer and the lower interlayer dielectric film. This intermediary film serves as a protective barrier during MTJ film etching, preventing direct contact between the etching plasma and the lower interlayer dielectric film, thereby eliminating etching damage while maintaining process simplicity
Solution Approach 2:
The lower electrode layer is oxidized to form the metal oxide insulating film before the MTJ film etching process. This preliminary oxidation creates a protective stopper layer that prevents overetching damage to the lower interlayer dielectric film, allowing subsequent etching to proceed without causing harm to underlying structures
2Manufacturing precision
If the lower electrode layer is used as an etching stopper layer, then overetching damage is prevented, but separate processing of the lower electrode layer is required increasing device complexity
Solution Approach 1:
The formation of the metal oxide insulating film through oxidation of the lower electrode layer merges two functions into one: the lower electrode layer simultaneously serves as both the electrical contact layer and the etching stopper layer. This eliminates the need for separate processing steps while maintaining the etching protection function
Solution Approach 2:
The lower electrode layer undergoes a parameter change through oxidation, transforming from a conductive metal layer to an insulating metal oxide layer. This parameter change enables the layer to function as an etching stopper while maintaining its original position and structural integrity, eliminating the need for additional processing layers
3Reliability
If design margin is given between MTJ and lower electrode layer, then processing alignment is easier, but cell downsizing is hindered
Solution Approach 1:
The metal oxide insulating film acts as a buffer zone or intermediary region between the MTJ film and the lower electrode layer. This intermediary layer provides inherent protection against misalignment during etching, allowing the cell dimensions to be reduced without compromising alignment tolerance, as the oxidative protection extends beyond the precise alignment boundaries
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 allows for the downsizing of memory cells, improves etching selectivity, and enhances the reliability of contact layers, enabling a more compact and efficient cell array with improved tolerance to misalignment.
Implementation Method 1
a metal oxide insulating film made of an oxide of a metal material forming the lower electrode layer and surrounding side surfaces of the lower electrode layer
Implementation Method 2
Research for putting a magnetic random access memory (MRAM) using the magnetoresistive effect (TMR: Tunneling Magneto Resistive) into practical use
Implementation Method 3
a spin transfer torque MRAM using the physics of spin transfer torque magnetization reversal
Data Source
AI summary
According to one embodiment, a magnetic random access memory includes a selection element formed on a semiconductor substrate, an interlayer dielectric film formed above the selection element, a contact layer formed in the interlayer dielectric film, and electrically connected to the selection element, a lower electrode layer made of a metal material, and electrically connected to the contact layer, a metal oxide insulating film made of an oxide of the metal material, and surrounding a side surface of the lower electrode layer, a magnetoresistive element formed on the lower electrode layer, an upper electrode layer formed on the magnetoresistive element, a sidewall insulating film formed on a side surface of the magnetoresistive element and a side surface of the upper electrode layer, and a bit line electrically connected to the upper electrode layer.