Two-Stage Filament Forming for Resistive Memory Stability
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Solution Overview
Problem
The existing resistive memory technologies face challenges in efficiently forming a stable filament structure due to difficulties in selecting a suitable gate voltage, leading to poor forming efficiency and reliability, with issues such as insufficient oxygen vacancy generation and unstable filament structures resulting in current tail states.
Innovation Solution
A two-stage filament forming method is introduced, where a first bias voltage is applied until a saturating read current is reached, and then adjusted by increasing the gate voltage and decreasing the drain voltage to ensure the formation of a stable filament structure, with verification of the target current value to complete the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a gate voltage above 1.5V is applied to the dielectric layer, then the voltage applied to the TMO becomes too small (below 0.3V), but this results in insufficient electric field to push oxygen ions to escape from the TMO
Solution Approach 1:
The forming process is divided into multiple stages with different voltage conditions. The first stage uses initial voltage conditions to start oxygen vacancy generation, and subsequent stages adjust voltages to complete filament formation, resolving the contradiction between maintaining stable gate voltage and providing sufficient voltage to TMO for oxygen ion migration.
Solution Approach 2:
The gate voltage and drain voltage are dynamically adjusted during the forming process rather than maintaining fixed values. The voltages are changed in response to measured read current saturation states, allowing the system to adapt voltage conditions to achieve both stability and sufficient electric field for filament formation.
2Reliability
If the gate voltage is set too low (such as Vg=0.65V), then the voltage applied to the TMO increases, but the forming current is almost zero meaning no sufficient oxygen vacancy is generated in the TMO to form the current path
Solution Approach 1:
The method applies preliminary voltage conditions in the first stage to initiate oxygen vacancy generation, then measures the read current saturation state to determine whether to proceed to subsequent stages. This preliminary action ensures that voltage is applied effectively only after sufficient oxygen vacancies are generated, improving both reliability and forming efficiency.
Solution Approach 2:
The forming process uses feedback from measuring read current saturation states to control subsequent voltage applications. The system continuously monitors whether oxygen vacancies are being generated sufficiently and adjusts the forming process accordingly, preventing both insufficient vacancy generation and wasteful continued voltage application.
3Productivity
If the initial RESET is performed when the current is too early after the filament forming process, then many bits will increase rather than decrease current from RESET, indicating the formed filament structure is not stable enough
Solution Approach 1:
The method performs preliminary voltage applications and read current measurements to ensure the filament structure is sufficiently formed and stable before allowing RESET operations. This preliminary formation phase prevents premature RESET operations that would otherwise occur when the filament is still unstable.
Solution Approach 2:
The system uses feedback from read current measurements to determine when the filament structure has reached sufficient stability. Only when the read current saturation state indicates adequate filament formation does the system permit RESET operations, ensuring both speed and stability requirements are met.
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 method enhances the stability of the filament structure, reduces current tail states, and improves the reliability of resistive memory units by ensuring sufficient oxygen ion generation and efficient filament formation.
Implementation Method 1
a positive bias voltage is applied so that oxygen vacancy and oxygen ions are generated in the dielectric layer
Implementation Method 2
the oxygen ions escape from the dielectric layer (TMO), and then a current path (filament structure) is formed in the dielectric layer
Data Source
AI summary
A filament forming method includes: performing first stage to apply first bias including gate and drain voltages to a resistive memory unit plural times until read current reaches first saturating state, latching read current in first saturating state as saturating read current, determining whether rate of increase of saturating read current is less than first threshold value; when rate of increase of saturating read current is not less than first threshold value, performing second stage to apply second bias, by increasing gate voltage and decreasing drain voltage, to the resistive memory unit plural times until read current reaches second saturating state, latching read current in second saturating state as saturating read current and determining whether rate of increase of saturating read current is less than first threshold value; finishing the method when rate of increase of saturating read current is less than first threshold value and saturating read current reaches target current value.