Time-dependent dielectric breakdown of MgO magnetic tunnel junctions and novel test method

Abstract

Time-dependent dielectric breakdown (TDDB), which is used to measure reliability, depends on both the thickness of the tunnel barrier and bias voltage. In addition, the heat generated by self-heating in a magnetic tunneling junction (MTJ) affects TDDB. Therefore, we investigated TDDB with the self-heating effect for a MgO tunnel barrier with thicknesses of 1.1 and 1.2 nm by the constant voltage stress (CVS) method. Using the results of this experiment, we predicted a TDDB of 1.0 nm for the tunnel barrier. Also, we suggested the use of not only the CVS method, which is a common way of determining TDDB, but also the constant current stress (CCS) method, which compensates for the disadvantages of the CVS method.

Modeling of Breakdown-Limited Endurance in Spin-Transfer Torque Magnetic Memory Under Pulsed Cycling Regime

“…By monitoring the I -V curves at each cycle, we could observe possible degradation phenomena and the exact event of endurance failure. This technique is thus most accurate in reproducing the exact device conditions in real time, instead of unrealistic description by constant/ramped stress [17], [18]. Also, the pulsed signal of Fig.…”

Determination of Type and Concentration of Traps in Nanoscale-Thick HfO2 Films Applicable for Gate Dielectric Stacks

“…For example, the results strongly depend on the quality of the deposited contacts, and the obtained characteristics are integral and cannot characterize the layer homogeneity. In the case of highk dielectrics grown on a silicon substrate, a nanolayer of silicon dioxide can form between the dielectric layer and silicon, significantly affecting the integral conductivity of the film, 11 which makes it difficult to study the electrical properties of high-k dielectrics by CVC measurements. Also, CVC does not allow one to study processes with long characteristic times.…”

“…Thus, the study of the processes of charge accumulation and dissipation in dielectric layers is important for improving growth technologies and further applications of new dielectrics or their combinations. Current–voltage characteristics (CVC) are traditionally used to study the processes of charge transport through traps, − but this approach has a number of disadvantages. For example, the results strongly depend on the quality of the deposited contacts, and the obtained characteristics are integral and cannot characterize the layer homogeneity.…”

Investigation of ramped voltage stress to screen defective magnetic tunnel junctions

“…The most representative measurement methods are divided into constant voltage stress (CVS) tests used to observe the breakdown time (t BD ) as a function of the electric fields, constant current stress (CCS) tests used to observe the charge to breakdown (Q BD ), and ramped voltage stress (RVS) tests used to observe the breakdown field (E BD ) [16]. In a previous study, we evaluated the t BD of MgO-MTJs according to voltage and current through CVS and CCS tests, respectively, and found that if appropriate current is applied in CCS test, the TDDB time can be shortened to about 1/10 of that of the CVS test [17]. Although we measured t BD through CVS and CCS tests and compared the results in the last study to find whether the test methods are applicable to MTJs, the screening time was too long to efficiently detect defective MTJ cells, and the criteria for division between defective MTJ cells and normal cells were somewhat ambiguous [17].…”

“…In a previous study, we evaluated the t BD of MgO-MTJs according to voltage and current through CVS and CCS tests, respectively, and found that if appropriate current is applied in CCS test, the TDDB time can be shortened to about 1/10 of that of the CVS test [17]. Although we measured t BD through CVS and CCS tests and compared the results in the last study to find whether the test methods are applicable to MTJs, the screening time was too long to efficiently detect defective MTJ cells, and the criteria for division between defective MTJ cells and normal cells were somewhat ambiguous [17]. In other words, the methods that continuously apply constant electrical stresses, such as CVS and CCS tests, have serious disadvantage that they cannot distinguish between normal and defective MTJ cells.…”