Magnetic Tunnel Junction Cap Layers for MRAM Error Control
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Solution Overview
Problem
Existing magnetoresistive random access memory (MRAM) technologies face challenges in achieving optimal write and read error rates due to insufficient perpendicular magnetic anisotropy in magnetic tunnel junction (MTJ) elements, which affects the reliability and performance of MRAM cells.
Innovation Solution
The formation of a cap layer in MTJ elements using fully oxidized magnesium through repeated deposition and oxidation processes enhances perpendicular magnetic anisotropy, improving the write and read error rates of MRAM cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MTJ elements are used without enhanced cap layers, then the device structure remains simple, but the perpendicular magnetic anisotropy is insufficient leading to higher write and read error rates
Solution Approach 1:
The patent applies parameter changes by modifying the oxidation state of magnesium in the cap layer. By controlling the oxidation process to achieve fully oxidized magnesium (MgO) with specific oxygen stoichiometry (O/Mg ratio close to 1.0), the perpendicular magnetic anisotropy is enhanced. This chemical parameter change in the cap layer material composition directly improves the magnetic properties of the MTJ element, reducing write and read error rates while maintaining a relatively simple device structure.
2Reliability
If repeated deposition and oxidation processes are used to form the cap layer, then the perpendicular magnetic anisotropy is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The cap layer formation process is segmented into multiple cycles of deposition and oxidation steps. Each cycle deposits a thin magnesium layer and then oxidizes it partially or fully. By repeating these segmented steps multiple times, the desired fully oxidized magnesium cap layer with optimized oxidation state is achieved. This segmentation allows precise control over the final oxidation state and stoichiometry, enhancing perpendicular magnetic anisotropy while managing manufacturing complexity through standardized process cycles.
Solution Approach 2:
The manufacturing process controls the oxidation state parameter by adjusting oxidation time, temperature, and oxygen concentration during each cycle. By systematically varying these parameters across multiple cycles, the process achieves the target fully oxidized magnesium state (O/Mg ratio ≈ 1.0) in the cap layer. This parameter control strategy enables reliable enhancement of perpendicular magnetic anisotropy through a repeatable manufacturing process.
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 increased perpendicular magnetic anisotropy in MTJ elements leads to improved write and read error rates, enhancing the reliability and performance of MRAM cells.
Implementation Method 1
enhances perpendicular magnetic anisotropy
Implementation Method 2
repeated deposition and oxidation processes
Implementation Method 3
magnetoresistive random access memory (MRAM), which involves spintronics that combines semiconductor technology and magnetic materials and devices. The spins of electrons, through their magnetizations, are used to indicate bit codes.
Implementation Method 4
magnetoresistive random access memory (MRAM)
Data Source
AI summary
In an embodiment, a device includes: a magnetoresistive random access memory cell including: a bottom electrode; a reference layer over the bottom electrode; a tunnel barrier layer over the reference layer, the tunnel barrier layer including a first composition of magnesium and oxygen; a free layer over the tunnel barrier layer, the free layer having a lesser coercivity than the reference layer; a cap layer over the free layer, the cap layer including a second composition of magnesium and oxygen, the second composition of magnesium and oxygen having a greater atomic concentration of oxygen and a lesser atomic concentration of magnesium than the first composition of magnesium and oxygen; and a top electrode over the cap layer.