Nonvolatile Memory Device Current Limiting Resistance Layer
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Solution Overview
Problem
In resistive random access memory (ReRAM) devices, the sudden drop in resistance during forming or set processes can lead to excessive current flow, potentially breaking the variable resistance element and damaging driving and protection circuit elements, due to uncontrolled current fluctuations and parasitic capacitances when external resistors are used.
Innovation Solution
Incorporating current limiting resistance layers with resistances of 1 kilo-ohm to 1 mega-ohm in series with the variable resistance element to control and limit electric current, thereby stabilizing filament formation and preventing element breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage is applied to the variable resistance element during forming or set, then resistance switching occurs, but resistance suddenly falls causing large electric current to flow and break the variable resistance element
Solution Approach 1:
A current limiting resistance layer is introduced as an intermediary component between the variable resistance element and the external circuit. This mediator layer limits the electric current flowing through the variable resistance element during forming and set operations, preventing excessive current that would cause element breakage, while still allowing sufficient current for resistance switching.
Solution Approach 2:
The current limiting resistance layer is configured beforehand to cushion or absorb excess current before it reaches the variable resistance element. By having this protective layer in place prior to forming or set operations, the system prevents harmful current spikes from damaging the element, addressing the reliability issue proactively.
2Reliability
If the resistance of the variable resistance element is reduced during set processing, then storage capability improves, but large reset current flows during reset and breaks driving circuit elements and protection circuit elements
Solution Approach 1:
The current limiting resistance layer serves as a mediator that continuously limits current flow in both directions - during set operations when forming the low resistance state, and during reset operations when the element switches back to high resistance. This prevents large reset currents from damaging driving and protection circuit elements.
Solution Approach 2:
The resistance value of the current limiting resistance layer is specifically designed to change the overall current characteristics of the memory cell. By selecting appropriate resistance values, the system maintains proper current levels during both set and reset operations, preventing circuit element breakage while preserving storage functionality.
3Reliability
If external resistors are used to limit current, then element breakage is prevented, but uncontrolled current fluctuations and parasitic capacitances cause read threshold deficiencies
Solution Approach 1:
The current limiting resistance layer is designed with specific resistance parameters (1 kilo-ohm to 1 mega-ohm) that optimize both current limiting and read threshold performance. This parameter selection prevents element breakage while minimizing negative effects on read threshold accuracy, unlike external resistors that cause uncontrolled current fluctuations and parasitic capacitance issues.
Solution Approach 2:
The current limiting resistance layer is merged with the variable resistance element to form an integrated memory cell structure. This integration eliminates the parasitic capacitances and connection issues associated with external resistors, while maintaining the current limiting function. The combined structure ensures stable read thresholds and prevents element breakage simultaneously.
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 solution effectively suppresses filament size fluctuations, prevents element breakage, and maintains stable switch characteristics, ensuring consistent set and reset voltages and currents, thus preventing read threshold deficiencies.
Implementation Method 1
a current limiting resistance layer connected in series to the variable resistance element and having resistance of 1 kilo-ohm to 1 mega-ohm
Implementation Method 2
processing called forming for feeding, while adjusting voltage, electric current and forming a filament (a current path) in nanometer order in the variable resistance element to reduce the resistance
Implementation Method 3
when voltage is applied to the variable resistance element, resistance suddenly falls at certain voltage. Therefore, it is likely that large electric current flows to the variable resistance element
Data Source
AI summary
According to one embodiment, a nonvolatile memory device includes a first wire, a second wire and a nonvolatile memory cell. The first wire is formed to extend in a first direction, and the second wire is formed at height different from height of the first wire and to extend in a second direction. The nonvolatile memory cell is arranged to be held between the first wire and the second wire in a poison where the first wire and the second wire cross. The nonvolatile memory cell includes a nonvolatile storage layer and a current limiting resistance layer connected in series to the nonvolatile storage layer and having resistance of 1 kilo-ohm to 1 mega-ohm.