MTJ Sidewall Passivation Layer for Oxygen Diffusion Barrier
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Solution Overview
Problem
Magnetic tunnel junctions (MTJs) in MRAM and spin-torque MRAM devices are susceptible to sidewall damage during etching, deposition, and annealing processes, particularly due to oxygen diffusion and redeposition of metal layers, leading to reduced device performance and yield.
Innovation Solution
A protective passivation layer is deposited on the MTJ sidewalls using techniques such as RF magnetron sputtering or atomic layer deposition, comprising materials like B, C, or Ge, which are amorphous and non-crystalline to prevent diffusion and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric layer is deposited on MTJ sidewalls to insulate adjacent MTJs, then electrical insulation between MTJs is improved, but sidewall damage occurs due to oxygen diffusion and metal redeposition
Solution Approach 1:
A protective passivation layer is deposited as an intermediary between the MTJ sidewalls and the dielectric layer. This passivation layer (comprising materials such as B, C, or Ge) acts as a barrier that prevents oxygen diffusion and metal redeposition during dielectric layer deposition, while still allowing the dielectric layer to be formed on top for electrical insulation.
Solution Approach 2:
The protective passivation layer is applied in advance before the dielectric layer deposition process. This preliminary protective coating prevents harmful oxygen diffusion and metal redeposition from occurring during subsequent high-temperature annealing and dielectric layer deposition processes.
2Reliability
If high temperature annealing around 400° C. is applied to improve CMOS quality, then CMOS unit quality is improved, but MTJ sidewall damage is exacerbated
Solution Approach 1:
The protective passivation layer serves as a mediator that shields MTJ sidewalls from the harmful effects of high-temperature annealing. It prevents oxygen diffusion into the MTJ structure during the 400° C. annealing process required for CMOS quality improvement.
Solution Approach 2:
The passivation layer creates an inert protective environment around the MTJ sidewalls during high-temperature processing. This barrier layer prevents reactive oxygen species from reaching and damaging the MTJ structure during annealing.
3Ease of manufacture
If the MgO tunnel barrier layer is exposed to atmosphere during dielectric layer deposition, then dielectric layer can be deposited, but the MgO layer degrades due to poor corrosion properties
Solution Approach 1:
The protective passivation layer is deposited as an intermediary barrier between the atmosphere (during dielectric layer deposition) and the MgO tunnel barrier layer. This prevents direct exposure and degradation of the MgO layer while still allowing the dielectric layer to be formed on top.
Solution Approach 2:
A thin film passivation layer is applied to the MTJ sidewalls and top surface, creating a protective shell that prevents atmospheric degradation of the underlying MgO tunnel barrier layer during dielectric layer deposition and subsequent processing.
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 passivation layer significantly improves the resistance of MTJs to sidewall damage, maintaining device integrity during high-temperature annealing and dielectric layer deposition, thereby enhancing performance and yield.
Implementation Method 1
damage may result from oxygen diffusion through a MTJ sidewall during an oxide dielectric layer deposition
Implementation Method 2
metal from a MTJ capping layer may be redeposited on MTJ sidewalls to cause shunting around the tunnel barrier layer
Implementation Method 3
The passivation layer is amorphous and not crystalline to prevent diffusion of reactive materials between crystals in a lattice
Data Source
AI summary
A magnetic device for magnetic random access memory (MRAM), spin torque MRAM, or spin torque oscillator technology is disclosed wherein a magnetic tunnel junction (MTJ) with a sidewall is formed between a bottom electrode and a top electrode. A passivation layer that is a single layer or multilayer comprising one of B, C, or Ge, or an alloy thereof wherein the B, C, and Ge content, respectively, is at least 10 atomic % is formed on the MTJ sidewall to protect the MTJ from reactive species during subsequent processing including deposition of a dielectric layer that electrically isolates the MTJ from adjacent MTJs, and during annealing steps around 400° C. in CMOS fabrication. The single layer is about 3 to 10 Angstroms thick and may be an oxide or nitride of B, C, or Ge. The passivation layer is preferably amorphous to prevent diffusion of reactive oxygen or nitrogen species.