Variable Resistance Memory Dual-Pulse Access Method
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Solution Overview
Problem
Existing memory devices face challenges in maintaining a large read window and stability of threshold voltage/current values over time due to element migration during access operations in variable resistance memory cells, leading to degradation in performance metrics such as threshold voltage window and cycling endurance.
Innovation Solution
Implementing a dual-pulse access method with opposite polarity pulses during write operations on variable resistance memory cells, specifically using a first pulse to change the resistance state and a second pulse with reduced magnitude and opposite polarity to minimize atom migration and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single pulse is used to change the resistance state of a memory cell, then the access operation is simple and fast, but element migration occurs leading to degradation in threshold voltage stability and cycling endurance
Solution Approach 1:
The access operation is segmented into multiple phases: a first phase applying a first bias to change the resistance state, and a second phase applying a second bias of opposite polarity to mitigate element migration. This segmentation allows the system to achieve both state change and stability improvement without excessive complexity
Solution Approach 2:
The second bias is applied as a preliminary anti-action to counteract the element migration caused by the first bias. By applying the opposite polarity bias immediately after the state change, the system prevents degradation before it occurs, maintaining threshold voltage stability and cycling endurance
2Reliability
If a dual-pulse access method is used to reduce element migration, then threshold voltage stability improves, but the access operation time increases
Solution Approach 1:
The access operation uses periodic action with two distinct phases: the first phase applies a first bias for a first duration to change the resistance state, and the second phase applies a second bias of opposite polarity for a second duration to mitigate migration. This periodic structure achieves reliability improvement while controlling total access time through optimized phase durations
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 dual-pulse approach significantly increases the resistance value of memory cells in the RESET state, providing a larger read window and improving the stability of threshold voltage/current values, thereby reducing degradation and enhancing memory cell performance.
Implementation Method 1
a first pulse having a first polarity and a first magnitude is applied across a variable resistance memory cell to cause a state change of the memory cell from a first resistance state to a second resistance state
Implementation Method 2
a second pulse having a second polarity opposite to the first polarity and a second magnitude less than the first magnitude is applied across the variable resistance memory cell subsequent to application of the first pulse
Data Source
AI summary
The disclosed technology generally relates to memory apparatuses and methods of operating the same, and more particularly to a memory device having a controller configured to cause a write operation to be performed on a variable resistance memory cell, which includes application of two successive access pulses having opposite polarities, and methods of using the same.