Memory Element with Al-Se-S Ion Source Layer for Low Voltage Operation
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Solution Overview
Problem
Existing nonvolatile memory elements face challenges in information retention due to resistance value changes over time and high operating voltages, particularly when stored at elevated temperatures or for extended periods, limiting their suitability for reliable data storage.
Innovation Solution
A memory element configuration featuring a resistance change layer with a high percentage of tellurium and an ion source layer containing aluminum, selenium, and sulfur, allowing for controlled resistance changes through voltage or current pulses, which stabilizes the low-resistance state and facilitates easy dissolution of metallic elements during erasure, thereby improving retention characteristics and reducing operating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing nonvolatile memory elements are used for data storage, then information can be retained without power, but resistance value changes over time and temperature cause information retention failures
Solution Approach 1:
The memory element is divided into distinct functional layers: a resistance change layer (containing Te, Sb, and metallic elements) and an ion source layer (containing Al, Se, and S). This segmentation allows each layer to perform its specific function optimally - the resistance change layer provides stable resistance states while the ion source layer enables controlled ion migration for writing and erasing operations, thereby resolving the contradiction between information retention and resistance stability.
Solution Approach 2:
The patent employs composite material compositions in both layers. The resistance change layer uses a composite of Te-Sb-metallic elements, while the ion source layer uses Al-Se-S composite. These composite materials provide synergistic effects that enhance both the stability of resistance states and the reliability of ion migration, directly addressing the contradiction between maintaining stable resistance values and ensuring reliable information retention.
2Ease of operation
If high voltage is applied to erase recorded information in existing memory elements, then erasure can be achieved, but the operation requires relatively high voltage levels and shows large resistance variation
Solution Approach 1:
The patent changes the chemical and physical parameters of the ion source layer by incorporating Al, Se, and S in specific ratios. This parameter change enables the layer to provide ions more efficiently at lower voltage levels. The Al-Se-S composition allows for controlled ion migration with reduced voltage requirements, directly addressing the contradiction between ease of erasure operation and energy consumption.
Solution Approach 2:
The ion source layer with Al-Se-S composition creates a structure that facilitates ion migration through controlled porosity and defect sites. This structural characteristic allows ions to move more easily under lower voltage conditions, reducing the operating voltage needed for erasure operations while maintaining ease of operation.
3Productivity
If metallic elements are dispersed into ion conductor in existing memory elements, then resistance value changes occur, but the resistance value shows unwanted changes when stored for long periods or at high temperatures
Solution Approach 1:
The patent introduces an intermediary ion source layer composed of Al-Se-S between the electrodes and the resistance change layer. This intermediary layer controls the migration of metallic elements, allowing them to move when needed for writing/erasing operations but preventing unwanted migration during storage. The Al-Se-S composition acts as a mediator that enables controlled resistance changes while maintaining resistance value retention during long-term storage or high-temperature conditions.
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 memory element achieves stable low-resistance states for data retention and efficient erasure with reduced voltage requirements, enhancing the overall performance and reliability of nonvolatile memory devices.
Implementation Method 1
at the time of voltage application between the two electrodes, the metal in the electrode as ions in the electrode is dispersed into the ion conductor, thereby changing the resistance value of the ion conductor
Implementation Method 2
changing the resistance value of the ion conductor or the electrical characteristics such as capacitance
Data Source
AI summary
There are provided a memory element and a memory device excellently operating at a low current, and having the satisfactory retention characteristics. The memory element includes a first electrode, a memory layer, and a second electrode in this order. The memory layer includes a resistance change layer disposed on the first electrode side, and being in a single- or multi-layer structure including a layer containing a highest percentage of tellurium (Te) as an anionic component, and an ion source layer disposed on the second electrode side, and containing a metallic element and one or more chalcogen elements including tellurium (Te), sulfur (S), and selenium (Se) with aluminum (Al) of 27.7 atomic % or more but 47.4 atomic % or less.