Crossbar Array Resistive Memory Pulse Width Control
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Solution Overview
Problem
The existing crossbar array devices using variable resistive memory elements, such as hafnium oxide, face challenges in accurately controlling the resistance value during set writing due to large voltage dependence, making it difficult for back propagation algorithms to converge and achieve fine-tuned synapse strength in neural networks.
Innovation Solution
A method is introduced where a first write voltage with a controlled pulse width is applied to a selected row line and a second write voltage with a controlled pulse width is applied to a selected column line in a crossbar array, allowing for precise control of the resistance value change in the variable resistive memory elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high pulse voltage is applied to achieve fast writing speed, then the write speed is improved, but the resistance value changes drastically and controllability deteriorates
Solution Approach 1:
The patent applies periodic pulsed voltage instead of continuous voltage to control the resistance change. By using voltage pulses with specific widths (tp1, tp2, tp3) rather than constant high voltage, the system achieves both fast writing and precise resistance control. The periodic action allows the resistance to change in controlled steps during each pulse cycle.
Solution Approach 2:
The patent changes the parameter of pulse width to control the resistance value. Instead of varying voltage magnitude to control resistance (which causes drastic changes), the system uses fixed voltage levels with variable pulse widths. This parameter change approach enables fine-grained control of resistance states while maintaining fast writing speeds.
2Manufacturing precision
If a low pulse voltage is used to improve resistance controllability, then the resistance value controllability is improved, but the write time increases
Solution Approach 1:
The patent uses periodic voltage pulses with optimized widths to achieve fast writing at low voltage. The pulsed action concentrates the writing effect into brief time windows, reducing total write time while maintaining precise resistance control through the controlled pulse duration rather than high voltage.
Solution Approach 2:
The patent optimizes the pulse width parameter to balance between writing speed and resistance control. By carefully selecting pulse widths (tp1 < tp2 < tp3 corresponding to different resistance states), the system achieves fast writing without requiring high voltage, thus maintaining both speed and precision.
3Manufacturing precision
If pulse width control is used to achieve fine adjustment of resistance, then the resistance value controllability is improved, but the write time increases
Solution Approach 1:
The patent implements periodic pulsed voltage application with specifically controlled widths to achieve fine resistance adjustment. The periodic nature of the pulses allows for precise control of the resistance change duration, enabling fine-tuning of resistance states while keeping the total write time minimal through efficient pulse timing.
Solution Approach 2:
The patent uses pulse width as the primary control parameter for resistance adjustment. By varying the pulse width within a controlled range rather than using prolonged low voltage or high voltage, the system achieves fine resistance control with minimal write time. The parameter optimization balances precision and speed.
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 enables high-accuracy control of resistance value changes, improving the controllability of multi-level cells and facilitating more effective learning processes in neural networks by reducing crosstalk and shortening write time.
Implementation Method 1
variable resistive memory elements 30 store different resistance states by applying voltage or current
Implementation Method 2
The voltage dependence of the resistance change at the setting side is very large compared to the reset side
Data Source
AI summary
An array device and a writing method thereof are provided. A synapse array device includes: a crossbar array, in which a resistive memory element is connected to each intersection of a plurality of row lines and a plurality of column lines; a row select/drive circuit selecting a row line of the crossbar array and applying a pulse signal to the selected row line; a column select/drive circuit selecting a column line of the crossbar array and applying a pulse signal to the selected column line; and a writing part writing to the resistive memory element connected to the selected row line and the selected column line. A first write voltage with controlled pulse width is applied to the selected row line, and a second write voltage with controlled pulse width is applied to the selected column line to perform set writing of the resistive memory element.