State-Variable Memory Device Merging Diode and Resistance Functions
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Solution Overview
Problem
Conventional nonvolatile memory devices using diodes for memory cell selection have complex production processes and restricted pulse voltage polarity, limiting their practicality and efficiency in quickly setting or resetting resistance states.
Innovation Solution
A memory device with a state-variable layer exhibiting both diode and variable-resistance characteristics, allowing for simplified production without a diode and enabling pulse voltage application in both polarities, reducing the pulse width required for state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is used for memory cell selection, then memory cell selection is achieved, but the production process becomes complex and pulse voltage polarity is restricted
Solution Approach 1:
The patent combines the diode selection function and variable resistance memory function into a single state-variable portion. The state-variable material exhibits both diode characteristics (rectification) and variable resistance characteristics, eliminating the need for separate diode and resistor components. This merging reduces production process complexity while maintaining reliable memory cell selection capability.
Solution Approach 2:
The state-variable portion serves multiple functions simultaneously: it acts as both the memory cell selection device (diode) and the storage element (variable resistance). This multi-functionality eliminates the need for separate components, simplifying the production process while achieving reliable memory cell selection and data storage in a single element.
2Reliability
If a diode is used for memory cell selection, then memory cell selection is achieved, but pulse voltage polarity application is restricted
Solution Approach 1:
The state-variable portion integrates both diode and variable resistance functions, allowing the same component to handle both selection and storage operations. This integration enables pulse voltage to be applied in both polarities for setting and resetting operations, removing the polarity restriction inherent in conventional diode-based designs while maintaining reliable memory cell selection.
Solution Approach 2:
The state-variable material's resistance is changed by applying pulse voltages of different polarities. A first polarity pulse sets the resistance to a first state, while a second polarity pulse resets it to a second state. This parameter change capability in both directions enables versatile pulse voltage application while the diode characteristic ensures proper memory cell selection.
3Reliability
If conventional variable-resistance material is used, then resistance value variation is achieved, but the production process requires separate diode and resistor components
Solution Approach 1:
The patent merges the diode selection function and variable resistance memory function into a single state-variable portion. The state-variable material exhibits both diode characteristics (rectification) and variable resistance characteristics, eliminating the need for separate diode and resistor components. This merging reduces production process complexity while maintaining reliable resistance value variation for data storage.
4Reliability
If pulse width is increased to change resistance state, then reliable state change is achieved, but the time required for memorization or reset increases
Solution Approach 1:
The state-variable material's resistance is changed by applying pulse voltages of different polarities rather than relying solely on pulse width modulation. A first polarity pulse sets the resistance to a first state, while a second polarity pulse resets it to a second state. This polarity-based control mechanism achieves reliable state changes with shorter pulse widths, reducing the time required for memorization and reset operations.
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 simplifies the production process, allows for accurate determination of resistance values, and shortens the time required for memorization or reset operations by enabling pulse voltage application in both polarities, improving the efficiency of state changes.
Implementation Method 1
a state-variable layer which lies on the first electrode layer and includes a plurality of state-variable portions that exhibit a diode characteristic and a variable-resistance characteristic
Implementation Method 2
Each of the plurality of state-variable portions exhibits a diode characteristic such that a forward direction is the direction extending from one of the first electrode line and the second electrode line to the other while a reverse direction is opposite to the forward direction
Data Source
AI summary
First electrode layer includes a plurality of first electrode lines (W1, W2) extending parallel to each other. State-variable layer lying on the first electrode layer includes a plurality of state-variable portions (60-11, 60-12, 60-21, 60-22) which exhibits a diode characteristic and a variable-resistance characteristic. Second electrode layer lying on the state-variable layer includes a plurality of second electrode lines (B1, B2) extending parallel to each other. The plurality of first electrode lines and the plurality of second electrode lines are crossing each other when seen in a layer-stacking direction with the state-variable layer interposed therebetween. State-variable portion (60-11) is provided at an intersection of the first electrode line (W1) and the second electrode line (B1) between the first electrode line and the second electrode line.