Magnetic Memory Circuitry Current Leakage Reduction
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Solution Overview
Problem
Two-terminal selectors in memory arrays have inferior performance due to higher current leakage, longer switching time, and finite switching life compared to transistors, necessitating an improvement in the circuitry that utilizes these selectors.
Innovation Solution
A memory circuitry comprising a magnetic memory element and a selector coupled in series between conductive lines, with a current detector and a mechanism to supply a high voltage for turning on the selector, allowing current reduction while maintaining the selector on, thereby improving performance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two-terminal selectors are used in memory arrays, then the wiring scheme is simplified and stacking of multiple levels is enabled, but current leakage increases and switching life decreases
Solution Approach 1:
The patent applies preliminary action by pre-charging the bit line to a high voltage state before the read operation. This high voltage is maintained during the read process to keep the selector in its conductive state, preventing current leakage and extending the switching life of the two-terminal selector while maintaining the simplified wiring architecture
2Ease of operation
If high voltage is applied to turn on the selector, then the selector conducts current, but current leakage increases
Solution Approach 1:
The patent implements periodic action by applying high voltage to the bit line only during the read operation period, then returning to a lower voltage state afterward. This time-limited high voltage application ensures the selector conducts current when needed while minimizing current leakage during non-operational periods, thus reducing energy loss
3Quantity of substance
If two-terminal selectors are used, then device density increases, but switching time increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage level of the bit line based on operational requirements. During read operations, high voltage is applied to ensure fast switching and proper conduction, while lower voltage is used during hold or non-operational states. This voltage parameter adjustment enables high device density with acceptable switching performance
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
The solution reduces current leakage and extends switching life by maintaining high voltage on the selector, enhancing the reliability and efficiency of the memory array while minimizing read disturbance and power consumption.
Implementation Method 1
The magnetic reference layer, the electron tunnel junction layer, and the magnetic free layer collectively form a magnetic tunneling junction (MTJ). When the magnetization directions of the magnetic free and reference layers are substantially parallel or oriented in a same direction, electrons polarized by the magnetic reference layer can tunnel through the insulating tunnel junction layer, thereby decreasing the electrical resistance of the MTJ. Conversely, the electrical resistance of the MTJ is high when the magnetization directions of the magnetic reference and free layers are substantially anti-parallel or oriented in opposite directions.
Implementation Method 2
The electron tunnel junction layer is normally made of an insulating material with a thickness ranging from a few to a few tens of angstroms. When the magnetization directions of the magnetic free and reference layers are substantially parallel or oriented in a same direction, electrons polarized by the magnetic reference layer can tunnel through the insulating tunnel junction layer, thereby decreasing the electrical resistance of the MTJ.
Data Source
AI summary
The present invention is directed to a memory circuitry that includes a magnetic memory element and a selector coupled in series between a first conductive line and a second conductive line; a current detector coupled to the second conductive line; and a means for supplying a sufficiently high voltage to the first conductive line for turning on the selector. When the selector turns on, the current detector detects a current flowing across the selector and effectuates a current limiter to reduce the current while maintaining the selector on. The memory circuitry may be operated by applying a sufficiently high voltage to the first conductive line for turning on the selector; reducing a current flowing through the selector while maintaining the sufficiently high voltage on the first conductive line; and determining a resistance state of the magnetic memory element.