Nonvolatile Resistance Change Device with Segmented Filament Layers
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Solution Overview
Problem
Current nonvolatile resistance change devices face challenges in miniaturization and reliability due to parasitic capacitance effects and variability in resistance values, which affect the multi-level bit capability and switching performance.
Innovation Solution
A nonvolatile resistance change device configuration with multiple variable resistance layers and electrodes, where conductive filaments grow at different rates based on metal supply from each electrode, allowing for stepwise resistance changes and improved reliability through the use of diffusion barrier layers and specific metal combinations to control filament formation and elimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If current compliance control method is used to achieve multi-level bit capability, then storage density increases, but reliability deteriorates due to parasitic capacitance effects and resistance value variation
Solution Approach 1:
The variable resistance layer is divided into multiple sub-layers (first variable resistance layer and second variable resistance layer), each capable of forming conductive filaments independently. This segmentation allows multi-level bit capability through different filament formation combinations while distributing the effect of parasitic capacitance across multiple layers, thereby improving reliability
Solution Approach 2:
A diffusion barrier layer is introduced between the electrode and the variable resistance layers to control and regulate the formation of conductive filaments. This intermediary layer prevents uncontrolled metal diffusion, reduces resistance value variation, and mitigates the harmful effects of parasitic capacitance, thereby improving reliability while maintaining multi-level bit capability
2Volume of moving object
If device size is reduced for miniaturization, then capacity per bit increases, but manufacturing precision deteriorates due to short channel effect and cell interferences
Solution Approach 1:
The variable resistance layer is segmented into multiple sub-layers with controlled thicknesses, allowing precise control of conductive filament formation in each layer. This enables miniaturization while maintaining manufacturing precision through independent control of resistance states in each sub-layer
Solution Approach 2:
Different regions of the variable resistance layer are designed with different properties (amorphous silicon in first layer, crystalline silicon in second layer), allowing localized control of filament formation and resistance characteristics. This enables miniaturization while maintaining element uniformity through optimized local material properties
3Speed
If conductive filament growth rate is increased for faster switching, then speed improves, but reliability deteriorates due to uncontrolled filament expansion and contraction
Solution Approach 1:
The conductive filament formation process is segmented across multiple variable resistance layers, each with different materials and thicknesses. This allows different parts of the filament to form and contract at different rates, enabling fast switching while maintaining resistance stability through the combined effect of multiple layers
Solution Approach 2:
The material composition and thickness parameters of each variable resistance layer are optimized to control filament growth rates. By adjusting these parameters, fast switching is achieved while maintaining reliable resistance values through controlled filament expansion and contraction in each layer
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
This configuration enables reliable multi-level bit capability and miniaturization by controlling conductive filament growth and resistance changes, enhancing the performance and reliability of the device.
Implementation Method 1
a first conductive filament is capable of growing based on metal supplied from the second electrode, and an n-th conductive filament whose growth rate is different from the first conductive filament is capable of growing based on metal supplied from the (n+1)-th electrode
Data Source
AI summary
According to one embodiment a first variable resistance layer which is arranged between a second electrode and a first electrode and in which a first conductive filament is capable of growing based on metal supplied from the second electrode, and an n-th variable resistance layer which is arranged between an n-th electrode and an (n+1)-th electrode and in which an n-th conductive filament whose growth rate is different from the first conductive filament is capable of growing based on metal supplied from the (n+1)-th electrode are included, a configuration in which a plurality of conductive filaments is electrically connected in series between the first electrode layer and the (n+1)-th electrode layer is included, and a resistance is changed in a stepwise manner.