Variable Resistance Memory Driving Method for Endurance
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Solution Overview
Problem
Conventional nonvolatile memory elements with variable resistance elements face challenges in achieving desired endurance characteristics, particularly during repeated writing processes, leading to degradation in read current and resistance value stability.
Innovation Solution
A method of driving a nonvolatile memory element that includes a variable resistance element and a current steering element, where the variable resistance element is set to low and high resistance states using specific gate voltages and write voltages, and the resistance value of the transistor is adjusted based on the current passing through or the resistance value read, to maintain stability within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional variable resistance elements are used for multiple writing processes, then the memory device can store data, but the endurance characteristics degrade and read current stability decreases
Solution Approach 1:
The patent changes the resistance value parameter of the transistor from a fixed state to a dynamically adjustable state. By modifying the transistor's resistance based on the variable resistance element's state, the system compensates for degradation effects and maintains stable read current characteristics over multiple writing operations, thereby improving endurance characteristics
Solution Approach 2:
The patent implements a feedback mechanism where the resistance value of the transistor is adjusted according to the current passing through or resistance value of the variable resistance element. This closed-loop control compensates for degradation in the variable resistance element, maintaining stable read current and improving reliability over repeated operations
2Productivity
If the resistance value of the variable resistance element changes outside a predetermined range, then the memory can be written, but the read current stability and resistance value stability deteriorate
Solution Approach 1:
The system continuously monitors the resistance value of the variable resistance element and provides feedback to adjust the transistor's resistance value accordingly. This feedback control ensures that even when the variable resistance element changes outside the predetermined range during writing operations, the overall read current remains stable by compensating through the transistor's resistance adjustment
Solution Approach 2:
The patent dynamically changes the transistor's resistance parameter in response to the variable resistance element's state. When the variable resistance element's resistance changes during writing operations, the transistor's resistance is adjusted to compensate, maintaining the overall circuit's stability and ensuring resistance values remain within acceptable ranges
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 improves the endurance characteristics of nonvolatile memory elements by maintaining the structure of the variable resistance element and ensuring the resistance value remains within a stable range, even with increased repeat counts, thereby enhancing the memory device's performance.
Implementation Method 1
a variable resistance element that reversibly changes in the resistance state in response to an applied electrical signal
Implementation Method 2
a current steering element having a transistor connected in series with the variable resistance element
Data Source
AI summary
A method of driving a nonvolatile memory element including a variable resistance element having a state reversibly changing between low and high resistance states by an applied electrical signal and a transistor serially connected to the variable resistance element. The method including: setting the variable resistance element to the low resistance state by applying a first gate voltage to a gate of the transistor and applying a first write voltage negative with respect to a first electrode; and changing a resistance value of the transistor obtained in a low-resistance write operation, when a value of current passing through the variable resistance element in the setting of the low resistance state or a resistance value of the nonvolatile memory element in the case where the variable resistance element is in the low resistance state is outside a predetermined range.