Characterization, Modeling, and Test of Intermediate State Defects in STT-MRAM

<div>The manufacturing process of STT-MRAM requires unique steps to fabricate and integrate magnetic tunnel junction (MTJ) devices which are data-storing elements. Thus, understanding the defects in MTJs and their faulty behaviors are paramount for developing high-quality test solutions. This article applies the advanced device-aware test to intermediate (IM) state defects in MTJ devices based on silicon measurements and circuit simulations. An IM state manifests itself as an abnormal third resistive state, which differs from the two bi-stable states of MTJ. We performed silicon measurements on MTJ devices with diameter ranging from 60nm to 120nm; the results show that the occurrence probability of IM state strongly depends on the switching direction, device size, and bias voltage. We demonstrate that the conventional resistor- based fault modeling and test approach fails to appropriately model and test such a defect. Therefore, device-aware test is applied. We first physically model the defect and incorporate it into a Verilog-A MTJ compact model and calibrate it with silicon data. Thereafter, this model is used for a systematic fault analysis based on circuit simulations to obtain accurate and realistic faults in a pre-defined fault space. Our simulation results show that an IM state defect leads to intermittent write transition faults. Finally, we propose and implement a device-aware test solution to detect the IM state defect.</div>

Download Full-text

Characterization, Modeling, and Test of Intermediate State Defects in STT-MRAM

10.36227/techrxiv.13811612.v2 ◽

2021 ◽

Author(s):

Lizhou Wu ◽

Siddharth Rao ◽

Mottaqiallah Taouil ◽

Erik Jan Marinissen ◽

Said Hamdioui ◽

...

Keyword(s):

Magnetic Tunnel Junction ◽

Fault Analysis ◽

Test Solution ◽

Resistive State ◽

Occurrence Probability ◽

Stable States ◽

Transition Faults ◽

Simulation Results ◽

Circuit Simulations ◽

Device Size

<div>The manufacturing process of STT-MRAM requires unique steps to fabricate and integrate magnetic tunnel junction (MTJ) devices which are data-storing elements. Thus, understanding the defects in MTJs and their faulty behaviors are paramount for developing high-quality test solutions. This article applies the advanced device-aware test to intermediate (IM) state defects in MTJ devices based on silicon measurements and circuit simulations. An IM state manifests itself as an abnormal third resistive state, which differs from the two bi-stable states of MTJ. We performed silicon measurements on MTJ devices with diameter ranging from 60nm to 120nm; the results show that the occurrence probability of IM state strongly depends on the switching direction, device size, and bias voltage. We demonstrate that the conventional resistor- based fault modeling and test approach fails to appropriately model and test such a defect. Therefore, device-aware test is applied. We first physically model the defect and incorporate it into a Verilog-A MTJ compact model and calibrate it with silicon data. Thereafter, this model is used for a systematic fault analysis based on circuit simulations to obtain accurate and realistic faults in a pre-defined fault space. Our simulation results show that an IM state defect leads to intermittent write transition faults. Finally, we propose and implement a device-aware test solution to detect the IM state defect.</div>

Download Full-text

Study on the Unbalanced Fault Dynamic Characteristics of Eccentric Motorized Spindle considering the Effect of Magnetic Pull

Shock and Vibration ◽

10.1155/2021/5536853 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Zhan Wang ◽

Wenzhi He ◽

Siyuan Du ◽

Zhe Yuan

Keyword(s):

Dynamic Model ◽

High Speed ◽

Air Gap ◽

Fault Analysis ◽

Experimental Results ◽

Machining Accuracy ◽

Motorized Spindle ◽

Unbalanced Magnetic Pull ◽

Static Eccentricity ◽

Simulation Results

Unbalanced fault is the most common fault of high-speed motorized spindle, which is the main factor affecting the machining accuracy of high-speed spindle. Due to the unbalanced magnetic pull produced by the air gap eccentricity of the stator and rotor, the unbalanced vibration of the motorized spindle will be further aggravated. In order to explore the dynamic behavior and motion law of the unbalanced fault motorized spindle under the eccentric state, a dynamic model of the unbalanced fault of the high-speed motorized spindle considering the unbalanced magnetic pull was established. Taking the eccentric motorized spindle customized by the research group as the research object, the dynamic model is established, simulated, and analyzed, and the response change law of motorized spindle under the effect of different speed, unbalance, and air gap is obtained. The simulation results show that the unbalanced magnetic pull caused by static eccentricity will increase the unbalanced vibration of motorized spindle, and the unbalanced vibration will also increase with the increase of static eccentricity. The vibration caused by unbalanced magnetic pull does not increase with the increase of rotating speed. In frequency-domain analysis, when there is unbalanced magnetic pull, the peak appears at 0 Hz, and the amplitude of fundamental frequency vibration will increase with the increase of eccentricity. The experimental results show that the greater the eccentricity is, the greater the unbalance vibration of the motorized spindle is. The experimental results are consistent with the simulation results, which further verify the accuracy of the model. The research results lay a theoretical basis for fault analysis and diagnosis of coupling fault motorized spindle.

Download Full-text

Implementation of an Associative Memory using a Restricted Hopfield Network

Global Journal of Researches in Engineering ◽

10.34257/gjrefvol21is2pg1 ◽

2021 ◽

pp. 1-18

Author(s):

Tet Yeap

Keyword(s):

Associative Memory ◽

Memory Capacity ◽

Hopfield Network ◽

Boltzmann Machine ◽

Noise Tolerance ◽

Stable States ◽

Noisy Images ◽

Machine Simulation ◽

Simulation Results ◽

Hidden Nodes

A trainable analog restricted Hopfield Network is presented in this paper. It consists of two layers of nodes, visible and hidden nodes, connected by weighted directional paths forming a bipartite graph with no intralayer connection. An energy or Lyapunov function was derived to show that the proposed network will converge to stable states. The proposed network can be trained using either the modified SPSA or BPTT algorithms to ensure that all the weights are symmetric. Simulation results show that the presence of hidden nodes increases the network’s memory capacity. Using EXOR as an example, the network can be trained to be a dynamic classifier. Using A, U, T, S as training characters, the network was trained to be an associative memory. Simulation results show that the network can perform perfect re-creation of noisy images. Its recreation performance has higher noise tolerance than the standard Hopfield Network and the Restricted Boltzmann Machine. Simulation results also illustrate the importance of feedback iteration in implementing associative memory to re-create from noisy images.

Download Full-text

Microgrid Fault Analysis Based on Multiple Distributed Generations

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.614-615.1820 ◽

2012 ◽

Vol 614-615 ◽

pp. 1820-1826

Author(s):

Xue Shun Ye ◽

Long Zhou ◽

Xi Sheng Tang

Keyword(s):

Energy Storage ◽

Diesel Engine ◽

Wind Turbine ◽

Theoretical Basis ◽

Simulation Models ◽

Transient Behavior ◽

Fault Analysis ◽

Distributed Generations ◽

Micro Grid ◽

Simulation Results

A microgrid is composed of multiple distributed generations (DGs).The amplifier and directions of micro-grid power are quite stochastic with the existence of the DGs. It results in great challenges on the adaptability and coordinate issue of protection. The mathematical and simulation models of photovoltaic, AWTG (asynchronous wind turbine generations), DEG (diesel engine generation) and energy storage are established and a typical microgrid containing multiple DGs is also introduced in this paper. It is demonstrated that the transient behavior of microgrid during fault depends mainly on the penetration level of different type of DGs. The simulation results verified that the transient characteristics of fault can provide theoretical basis for the protection of microgrid.

Download Full-text

Fault Analysis of Stator Inter-Turn Short Circuit in Doubly Fed Induction Machines

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.912-914.679 ◽

2014 ◽

Vol 912-914 ◽

pp. 679-683

Author(s):

Bo Qiang Xu ◽

Jing Ting Wang

Keyword(s):

Short Circuit ◽

Short Circuit Current ◽

Induction Machines ◽

Fault Analysis ◽

Loop Model ◽

Doubly Fed Induction Generator ◽

Fault Features ◽

Simulation Results ◽

Doubly Fed ◽

Short Circuit Fault

The doubly fed induction generator (DFIG) is an important component of wind turbine systems,so the fault analysis is great necessary.This paper shows a way to analysis the features of stator inter-short circuit fault,which is based on multi-circuit theory.The fault features of stator inter-turn short circuit in doubly fed induction are analyzed in this paper,deeply and thoroughly.Then a multi-loop model was carried out to simulate 5.5kW DFIG ,which was in normal conditions and in cases of fault of stator inter-turn short circuit,respectively.A fourier transformation was applied to analysis the simulation results,especially about short circuit current.

Download Full-text

Electrically programmable magnetoresistance in $$\text{AlO}_{x}$$-based magnetic tunnel junctions

Scientific Reports ◽

10.1038/s41598-021-84749-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jhen-Yong Hong ◽

Chen-Feng Hung ◽

Kui-Hon Ou Yang ◽

Kuan-Chia Chiu ◽

Dah-Chin Ling ◽

...

Keyword(s):

Resistive Switching ◽

Magnetic Tunnel Junction ◽

High Resistance State ◽

Resistive State ◽

Bipolar Resistive Switching ◽

Spin Dependent Transport ◽

Electric And Magnetic Fields ◽

Potential Applications ◽

Resistance State ◽

Dependent Transport

AbstractWe report spin-dependent transport properties and I–V hysteresis characteristics in an $$\text{AlO}_{x}$$ AlO x -based magnetic tunnel junction (MTJ). The bipolar resistive switching and the magnetoresistances measured at high resistance state (HRS) and low resistance state (LRS) yield four distinctive resistive states in a single device. The temperature dependence of resistance at LRS suggests that the resistive switching is not triggered by the metal filaments within the $$\text{AlO}_{x}$$ AlO x layer. The role played by oxygen vacancies in $$\text{AlO}_{x}$$ AlO x is the key to determine the resistive state. Our study reveals the possibility of controlling the multiple resistive states in a single $$\text{AlO}_{x}$$ AlO x -based MTJ by the interplay of both electric and magnetic fields, thus providing potential applications for future multi-bit memory devices.

Download Full-text