Nonvolatile Storage Device Stabilizing Resistance via Measuring Cells
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Solution Overview
Problem
Conventional nonvolatile resistive random access memory devices face challenges in stabilizing resistance values in high and low resistance states due to variations in the threshold voltage of the cell transistor, affecting read and write operation characteristics and reliability.
Innovation Solution
A nonvolatile semiconductor storage device design that applies a predetermined voltage to the variable resistance element during write operations, independent of the cell transistor's threshold voltage, using a configuration with cell transistor performance measuring cells to determine optimal voltage values for program and erase operations, ensuring stable resistance states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional resistive random access memory uses a cell transistor to select the variable resistance element, then the memory cell can be configured with series connection of transistor and resistor, but the resistance values in high and low resistance states vary due to manufacturing variations in the threshold voltage of the cell transistor
Solution Approach 1:
The patent applies preliminary action by measuring the threshold voltage of the cell transistor before write operations and using this measured value to determine the optimal write voltage. This pre-measurement and pre-calculation approach ensures that the write voltage is precisely tailored to compensate for manufacturing variations, thereby stabilizing the resistance values in both high and low resistance states without requiring additional hardware complexity.
2Productivity
If the resistance value of the variable resistance element is used to store data, then high-speed write operation can be achieved, but the resistance values depend on applied voltage which is affected by cell transistor threshold voltage variations
Solution Approach 1:
The patent implements feedback by measuring the threshold voltage of the cell transistor and using this information to adjust the write voltage applied to the variable resistance element. This feedback mechanism ensures that despite manufacturing variations in the cell transistor, the write voltage is optimized to achieve stable resistance values, thereby maintaining both high-speed write operation and reliable data storage.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the write voltage based on the measured threshold voltage of the cell transistor. Instead of using a fixed write voltage, the system calculates and applies an optimized voltage value that compensates for manufacturing variations, thereby stabilizing the resistance values while maintaining high-speed write performance.
3Ease of operation
If a predetermined voltage is applied to the variable resistance element during program operation, then write operation can be performed, but the voltage is affected by threshold voltage variations causing resistance value instability
Solution Approach 1:
The patent applies preliminary action by measuring the threshold voltage of the cell transistor before write operations and using this measured value to determine the optimal write voltage. This pre-measurement and pre-calculation approach ensures that the write voltage is precisely tailored to compensate for manufacturing variations, thereby stabilizing the resistance values in both high and low resistance states without requiring additional hardware complexity.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the write voltage based on the measured threshold voltage of the cell transistor. Instead of using a fixed write voltage, the system calculates and applies an optimized voltage value that compensates for manufacturing variations, thereby stabilizing the resistance values while maintaining ease of write operation.
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 stabilizes resistance values in both low and high states, enhancing read operation characteristics and reliability, allowing for simultaneous good read and write performance.
Implementation Method 1
The variable resistance element is reversibly switched between the low and high resistance states, depending on the polarity of a voltage applied to the opposite ends of the variable resistance element
Data Source
AI summary
A memory array includes a plurality of memory cells arranged in a matrix, each memory cell including a cell transistor and a variable resistance element connected to an end of the cell transistor, and a cell transistor performance measuring cell including a MOS transistor. The cell transistor performance measuring cell is used to stabilize resistance values in a low resistance state and a high resistance state of the variable resistance element irrespective of variations in the cell transistor and thereby improve read characteristics and reliability characteristics of a nonvolatile semiconductor storage device.