Resistance Variable Memory Drift Acceleration
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Solution Overview
Problem
Resistance variable memory cells, such as phase change memory cells, experience resistance drift over time, leading to erroneous data sensing and reliability issues, which existing technologies have not adequately addressed.
Innovation Solution
Applying a pre-read signal to the programmed resistance variable memory cell before readout to accelerate the drift of the resistance, providing improved stabilization and accuracy without the need for temperature-based annealing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance variable memory cells are programmed to store data, then data storage capability is achieved, but resistance drift occurs over time leading to erroneous sensing
Solution Approach 1:
The patent applies a preliminary annealing pulse immediately after programming the memory cell before any read operations. This pre-action stabilizes the resistance state by accelerating the annealing process, preventing subsequent drift that would cause erroneous sensing. The preliminary action eliminates the need for continuous monitoring and correction during read operations.
Solution Approach 2:
The patent changes the temporal parameter of the annealing process by applying a short high-current pulse immediately after programming. This parameter change (timing and intensity of the pulse) accelerates the structural relaxation and stabilizes the resistance state, transforming the natural slow drift process into a rapid initial stabilization followed by minimal further drift.
2Stability of the object's composition
If temperature-based annealing processes are used to stabilize resistance, then resistance drift is reduced, but process complexity and power consumption increase
Solution Approach 1:
The patent replaces the thermal annealing mechanism (temperature-based process) with an electrical field-based annealing approach. By applying a high-current pulse, the system uses electrical energy directly to drive the structural relaxation and stabilization process, eliminating the need for temperature control mechanisms and associated complexity.
Solution Approach 2:
The patent changes the physical parameter from temperature to electrical current density. Instead of using thermal energy to drive annealing, the system applies a concentrated electrical pulse that directly provides the energy needed for structural relaxation, simplifying the control mechanism while achieving the same stabilization effect.
3Speed
If read operations are performed immediately after programming, then access speed is improved, but resistance drift causes increased error rates
Solution Approach 1:
The patent performs a preliminary annealing action immediately after programming before the first read operation. This pre-stabilization ensures that when reading occurs, the resistance state is already optimized, allowing for both fast access and high accuracy. The preliminary action eliminates drift-related errors without adding delay to the overall access time.
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 approach increases the accuracy and reliability of resistance variable memory cells by accelerating the stabilization of resistance states, resulting in decreased error rates and extended memory life.
Implementation Method 1
resistance variable memory cells can store data based on the resistance of a storage element, e.g., a storage element having a variable resistance
Implementation Method 2
applying sources of an electrical field or energy, such as positive or negative electrical signals, e.g., positive or negative voltage or current signals, to the cells
Data Source
Figure 1
Figure 2A~2B
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AI summary
The present disclosure includes apparatuses and methods including drift acceleration in resistance variable memory. A number of embodiments include applying a programming signal to the resistance variable memory cell to program the cell to a target state, subsequently applying a pre-read signal to the resistance variable memory cell to accelerate a drift of a resistance of the programmed cell, and subsequently applying a read signal to the resistance variable memory cell.