Segmented Metal Nitride Bottom Electrode for STT-MRAM Write Current
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Solution Overview
Problem
Magnetic memory devices, particularly spin transfer torque magnetic random access memory (STT-MRAM) devices, face challenges with decreasing write current as magnetic cell sizes decrease, affecting their performance and efficiency.
Innovation Solution
A magnetic memory device structure is developed with a bottom electrode comprising a first and second bottom electrode, both made of metal nitride, where the first bottom electrode has higher crystallinity and a columnar structure, and the second bottom electrode is thinner and amorphous, enhancing the electrical characteristics and allowing for easier patterning and separation between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the magnetic cell size is decreased to increase storage capacity, then the storage density is improved, but the write current decreases
Solution Approach 1:
The bottom electrode is segmented into two distinct layers: a first bottom electrode layer with high crystallinity and a second bottom electrode layer with low crystallinity. This segmentation allows each layer to perform different functions - the first layer provides high electrical conductivity to maintain write current, while the second layer enables easy patterning and cell separation, thus resolving the contradiction between maintaining write current and enabling miniaturization for higher storage density.
Solution Approach 2:
Different crystallinity properties are assigned to different parts of the bottom electrode structure. The first bottom electrode layer has high crystallinity for optimal electrical conductivity, while the second bottom electrode layer has low crystallinity for ease of patterning. This local differentiation of material properties allows the system to simultaneously achieve high write current and easy manufacturability for small cell sizes.
2Device complexity
If a single bottom electrode layer is used to simplify the structure, then the device complexity is reduced, but the electrical characteristics deteriorate
Solution Approach 1:
The bottom electrode is divided into two functional layers with distinct crystallinity characteristics. The first layer (higher crystallinity) ensures good electrical conductivity and interface quality with the magnetic tunnel junction, while the second layer (lower crystallinity) provides ease of patterning and separation. This segmentation maintains excellent electrical characteristics while enabling manufacturability.
Solution Approach 2:
The bottom electrode uses a composite structure combining two metal nitride layers with different crystallinity properties. This composite approach allows the system to leverage the advantages of both high crystallinity (good electrical properties) and low crystallinity (easy patterning) within a single electrode component, thereby maintaining reliability while managing complexity.
3Reliability
If the bottom electrode has high crystallinity to improve electrical conductivity, then the write current is maintained, but the patterning and cell separation become difficult
Solution Approach 1:
The bottom electrode is segmented into two layers with different crystallinity to separate the functions of electrical conductivity and patterning ease. The first layer (higher crystallinity) ensures good electrical conductivity for maintaining write current, while the second layer (lower crystallinity) enables easy patterning and cell separation. This segmentation resolves the contradiction by assigning different properties to different parts of the same component.
Solution Approach 2:
Different crystallinity qualities are applied locally within the bottom electrode structure. The first bottom electrode layer has higher crystallinity for optimal electrical conductivity, while the second bottom electrode layer has lower crystallinity for ease of patterning. This local quality differentiation allows the system to simultaneously achieve good electrical properties and manufacturability.
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 proposed structure improves the electrical characteristics of magnetic memory devices by maintaining high write current and enabling efficient data storage through controlled magnetization direction changes, addressing the issue of decreasing write current with smaller cell sizes.
Implementation Method 1
spin transfer torque magnetic random access memory (STT-MRAM) devices
Data Source
AI summary
Disclosed are a magnetic memory device and a method of fabricating the same. The magnetic memory device comprises a bottom electrode on a substrate, a magnetic tunnel junction pattern including a first magnetic layer, a tunnel barrier layer, and a second magnetic layer that are sequentially stacked on the bottom electrode, and a top electrode on the magnetic tunnel junction pattern. The bottom electrode comprises a first bottom electrode and a second bottom electrode on the first bottom electrode. Each of the first and second bottom electrodes comprises metal nitride. The first bottom electrode has a crystallinity higher than that of the second bottom electrode.