Variable Resistance Memory Write Method Using Recovery Voltage Pulses
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Solution Overview
Problem
Conventional variable resistance nonvolatile memory devices experience unstable resistance change operations as the number of write cycles increases, leading to a decrease in the reliability of the memory device.
Innovation Solution
A write method for variable resistance nonvolatile memory elements that includes a first transition metal oxide layer and a second transition metal oxide layer with a smaller oxygen deficiency, where a set of strong recovery-voltage pulses is applied to ensure stable resistance change operations by determining if the resistance state fails to change and applying a first strong recovery-voltage pulse followed by a second strong recovery-voltage pulse with a longer pulse width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If one high resistance writing voltage pulse and one low resistance writing voltage pulse are repetitively and alternately applied to the variable resistance nonvolatile memory element, then the resistance change operation can be performed, but the resistance change state becomes unstable as the number of times the variable resistance element is rewritten increases
Solution Approach 1:
Before applying the normal low resistance writing voltage pulse, a recovery voltage pulse with the same polarity is applied in advance. This preliminary action prepares the memory element by adjusting the oxygen distribution in the transition metal oxide layer, ensuring that the subsequent write operation can successfully change the resistance state even after multiple rewrite cycles.
Solution Approach 2:
The invention changes the voltage parameters dynamically based on the write cycle count. A recovery voltage pulse with the same polarity as the low resistance writing voltage pulse is applied before the actual write operation. This parameter change (adding a preparatory voltage pulse) modifies the electrical state of the memory element, enabling stable resistance change operations throughout the device lifetime.
2Quantity of substance
If the number of rewrite operations increases, then more data can be stored, but the resistance change state becomes unstable leading to operation failure
Solution Approach 1:
A recovery voltage pulse is applied in advance before each write operation to prepare the memory element. This preliminary action maintains the operational stability of the memory element throughout the entire data storage process, enabling the device to reliably store large amounts of data over many rewrite cycles without experiencing resistance change failures.
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 method ensures a stable operating window for resistance change operations even with increased write cycles, significantly improving the reliability of the nonvolatile memory device.
Implementation Method 1
a variable resistance layer between the first electrode and the second electrode, the variable resistance layer including a first transition metal oxide layer in contact with the first electrode, and a second transition metal oxide layer in contact with the second electrode
Implementation Method 2
changing the resistance state from a first resistance state for use in recording first information to a second resistance state for use in recording second information when a pulse of a first voltage is applied to the variable resistance nonvolatile memory element
Data Source
AI summary
A write method for writing to a variable resistance nonvolatile memory element, comprising applying a set of strong recovery-voltage pulses at least once to the variable resistance nonvolatile memory element when it is determined that the resistance state of the variable resistance nonvolatile memory element fails to change to a second resistance state, remaining in a first resistance state, the set of strong recovery-voltage pulses including pulses: (1) a first strong recovery-voltage pulse which has a greater amplitude than a normal second voltage for changing the resistance state to the first resistance state, and has the same polarity as the second voltage; and (2) a second strong recovery-voltage pulse which follows the first strong recovery-voltage pulse and has a longer pulse width than the pulse width of the normal first voltage for changing the resistance state to the second resistance state, and has the same polarity as the first voltage.