Pre-conditioning Two-terminal Memory for Endurance
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Solution Overview
Problem
Two-terminal memory cells, particularly resistive-switching memory cells, face challenges in maintaining multi-programmability due to 'reverse pop' phenomena, where application of a negative voltage after programming further programs the cell, rendering it inoperable, and difficulty in erasing programmed states, leading to loss of capacity for switching.
Innovation Solution
Pre-conditioning of two-terminal memory cells with a series of successively larger magnitude signals, including opposite polarity signals, to establish a stable conductive filament and facilitate reliable switching, reducing power consumption and preventing 'reverse pop' by ensuring effective erasability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative voltage is applied after programming the memory cell, then the cell is intended to be erased, but the 'reverse pop' phenomenon causes further programming of the cell, rendering it inoperable
Solution Approach 1:
The patent applies preliminary forming voltages to the memory cell before actual programming operations. These forming voltages prepare the conductive filament structure in advance, establishing a stable baseline state that prevents the reverse pop phenomenon during subsequent erase operations. The preliminary action creates a controlled initial condition that resolves the harmful interaction between erase voltages and the filament structure.
2Adaptability or versatility
If multiple programming states are implemented to increase storage capacity, then memory versatility is improved, but the ability to reliably erase and reprogram cells deteriorates due to reverse pop
Solution Approach 1:
The patent implements preliminary forming operations that establish a stable conductive filament structure before multi-state programming. This preliminary action creates a robust baseline that allows multiple programming levels while maintaining the ability to reliably erase and reprogram cells without reverse pop interference.
Solution Approach 2:
The patent utilizes parameter changes in the forming voltage characteristics (magnitude, duration, polarity sequence) to control the filament formation process. By carefully adjusting these voltage parameters, the patent achieves stable multi-state programming while preserving erasability, resolving the contradiction between versatility and reliability.
3Speed
If high magnitude program signals are applied to achieve fast switching, then switching speed is improved, but power consumption increases and reliability decreases
Solution Approach 1:
The patent applies preliminary forming voltages that prepare the conductive filament structure in advance. This preliminary action reduces the magnitude of subsequent programming voltages needed, thereby decreasing power consumption while maintaining fast switching speeds. The forming operation creates a favorable initial state that enables efficient later programming cycles.
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
Pre-conditioning enhances the endurance and reliability of two-terminal memory cells by allowing for reversible switching between high and low resistive states, maintaining multi-programmability and reducing power consumption by ensuring effective erasure capabilities.
Implementation Method 1
Pre-conditioning of two-terminal memory cells with a series of successively larger magnitude signals, including opposite polarity signals, to establish a stable conductive filament
Data Source
AI summary
Providing for preconditioning of multi-programmable, two-terminal memory for improved endurance and switching functionality is described herein. By way of example, one or more pre-conditioning signals can be applied to a memory cell post-fabrication. The preconditioning signal(s) can have relatively small power, avoiding programming of the memory cell, compared with an associated program signal. The preconditioning signal(s) can facilitate reliable erasure of the memory cell following subsequent programming at normal programming power. Accordingly, switching functionality of the two-terminal memory can be preserved, maintaining the multi-programmable nature of the memory cell.