Dual MgO Barrier Layer for TMR Devices
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Solution Overview
Problem
TMR devices with existing MgO barrier layers face challenges in achieving high ΔR/R and low RA while maintaining good antiferromagnetic and ferromagnetic properties, which are crucial for optimal performance, especially as devices are miniaturized for higher densities.
Innovation Solution
A method involving DC magnetron sputter deposition of a first MgO barrier layer from an Mg target in an oxygen environment, followed by RF sputter deposition of a second MgO barrier layer in an oxygen-free environment, with optional protection layers and oxygen treatments to optimize oxygen doping and minimize contamination, ensuring high-spin-polarization tunneling paths and low contact resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single MgO barrier layer is deposited by conventional sputtering, then the device structure is simple, but the TMR coefficient (ΔR/R) is insufficient and contact resistance is high
Solution Approach 1:
The barrier layer is divided into multiple sub-layers (MgO1, MgO2, MgO3) with different deposition conditions and compositions. Each sub-layer serves a specific function: the first MgO layer provides good interface contact, the second layer provides optimal tunneling barrier properties, and the third layer provides protection and stability. This segmentation allows optimization of each layer's properties independently, achieving high TMR coefficient and low contact resistance
Solution Approach 2:
The barrier structure uses composite material design by combining multiple MgO layers with different deposition parameters and optional intermediate layers (such as Ru or Ta). This composite structure leverages the advantages of each layer to achieve superior overall performance in terms of tunneling magnetoresistance and electrical contact properties
2Reliability
If the barrier layer thickness is increased to reduce resistance, then contact resistance decreases, but the TMR coefficient (ΔR/R) decreases
Solution Approach 1:
Different regions of the barrier structure have different thicknesses and properties optimized for their specific functions. The interface regions have thinner effective barrier thickness for low contact resistance, while the central region maintains optimal thickness for high TMR coefficient. This local optimization allows simultaneous achievement of low resistance and high TMR effect
3Productivity
If devices are miniaturized to achieve higher densities, then storage capacity increases, but maintaining high SNR becomes more difficult due to increased resistance
Solution Approach 1:
The deposition parameters (power, pressure, oxygen flow rate, temperature) are precisely controlled and optimized for each layer to achieve atomic-level interface quality and minimal defects. This parameter optimization reduces variability and maintains consistent electrical properties even as device dimensions are reduced for higher density applications
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 results in TMR devices with significantly higher ΔR/R and lower RA, maintaining thermal stability and enabling better performance in high-density memory cells and recording media by minimizing pinholes and residual impurities through in-situ deposition in the same module.
Implementation Method 1
a first magnesium-oxide (MgO) barrier layer or film is formed over one of the TMR device's ferromagnetic layers by a DC magnetron sputter deposition from an Mg target in an oxygen environment
Implementation Method 2
a second MgO barrier layer or film is formed over the first MgO film by an RF sputter deposition from an MgO target and in an environment substantially free of oxygen
Implementation Method 3
oxidizing these films in an oxygen gas in an oxygen treatment module
Data Source
AI summary
A method of forming a barrier layer of a tunneling magnetoresistive (TMR) device by forming first and second MgO barrier layers by different sputtering methods, but in the same sputtering system module. A first magnesium-oxide (MgO) barrier layer is formed over one of the TMR device's ferromagnetic layers by a DC magnetron sputter deposition from an Mg target in an oxygen environment. In the same module, a second MgO barrier layer is formed over the first MgO film by an RF sputter deposition from an MgO target and in an environment free of oxygen. Prior to the formation of the first MgO barrier layer, an optional Mg protection layer can be deposited on the ferromagnetic layer and oxidized by a first optional oxygen treatment. After deposition of the first MgO barrier layer, a second optional oxygen treatment may be conducted. After deposition of the second MgO barrier layer, a second Mg protection layer may be deposited by DC sputter deposition, followed by an optional third oxygen treatment.