A5101577531- Magnetic properties of thin films
- Advanced Memory and Neural Computing
- Magnetic Properties and Applications
- Ferroelectric and Negative Capacitance Devices
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Semiconductor materials and devices
- Magnetic Field Sensors Techniques
- Non-Destructive Testing Techniques
- Surface and Thin Film Phenomena
- ZnO doping and properties
- Advanced Data Storage Technologies
- Theoretical and Computational Physics
- Magneto-Optical Properties and Applications
- Metallic Glasses and Amorphous Alloys
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic Properties of Alloys
- Semiconductor materials and interfaces
- Advanced Surface Polishing Techniques
- Atomic and Subatomic Physics Research
- Phase-change materials and chalcogenides
- Earthquake Detection and Analysis
- Advancements in Semiconductor Devices and Circuit Design
- Ionosphere and magnetosphere dynamics
IBM (United States)
2011-2021
IBM Research - Thomas J. Watson Research Center
2005-2019
Micron (United States)
2015
Seagate (United States)
2000-2005
IBM Research - Almaden
2005
Massachusetts Institute of Technology
1996-1999
Polish Academy of Sciences
1984-1993
Silesian University in Opava
1976
Spin torque switching is investigated in perpendicular magnetic tunnel junctions using Ta∣CoFeB∣MgO free layers and a synthetic antiferromagnet reference layer. We show that the Ta∣CoFeB interface makes key contribution to anisotropy. The quasistatic phase diagram for under applied field voltage reported. Low voltages, Vc 50 ns=290 mV are obtained, range required spin random access memory. Switching down 1 ns reported, with rise speed from increased overdrive eight times greater than...
Careful tunneling studies in high quality $\mathrm{Co}/{\mathrm{Al}}_{2}{\mathrm{O}}_{3}/{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ junctions show a junction magnetoresistance (JMR) of 20.2% and 27.1% at 295 77 K, respectively, where the latter is agreement with Julliere's model. The temperature dependence JMR can be explained by surface magnetization. decrease increasing dc bias intrinsic to ferromagnetic junctions. strong disagreement recent theories low region attributed magnetic excitations...
Spin-transfer torque magnetic random access memory (STT-MRAM) is one of the most promising emerging non-volatile technologies. MRAM has so far been demonstrated with a unique combination density, speed, and non-volatility in single chip, however, without capability to replace any mainstream memory. In this paper, we demonstrate basic physics spin switching 20 nm diameter tunnel junctions perpendicular anisotropy materials. This deep scaling clearly indicates STT device itself may be suitable...
The temperature dependence of spin-polarized tunneling is investigated between 77 and 420 K for various ferromagnetic tunnel junctions. Both the junction resistance magnetoresistance decrease with increasing $T.$ experimental results are successfully described by a model that includes two current contributions. dominant one elastic, electrodes, each an electron polarization $P$ decreases $T$ due to thermally excited spin waves according...
Recently developed magnetic tunnel junctions with full perpendicular magnetization that are spin-torque switchable allow for quantitative comparison of switching statistics a macrospin model. For typical devices above 50 nm in lateral size, the suggests presence subvolume excitations which often dominate process and degrade efficiency. A simple model spin-torque-driven is presented to account experimental observations. The origin thermal excitation traced competition between fluctuation...
The dependence of the write-error rate (WER) on applied write voltage, pulse width, and device size was examined in individual devices a spin-transfer torque (STT) magnetic random-access memory (MRAM) 4 kbit chip. We present 10 ns switching data at <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> error level for 655 devices, ranging diameter from 50 nm to 11 nm, make statistically significant demonstration that specific tunnel junction...
It is convenient to define the spin-torque switching efficiency in nanostructured magnetic tunnel junctions as ratio between free-layers thermal activation barrier height ${E}_{b}$ and threshold current ${I}_{c0}$. Recent device exploration has led occasional observations of induced that exceeds macrospin limit by a factor 2--10. In this paper we examine possible origins for such enhancement, materials properties may allow full realization enhancements.
Al 2 O 3 tunnel barriers I, formed by the oxidization of metal various thicknesses between two ferromagnetic (FM) films were investigated to understand influence overlayer on junction magnetoresistance (JMR). The optimum thickness was observed lie in range 1–1.6 nm achieve good JMR FM–I–FM junctions. Additionally, such junctions can be used study magnetic proximity effect ferromagnet/normal bilayer systems.
Ferromagnetic–insulator–ferromagnetic trilayer tunnel junctions show magnetoresistance (JMR) effects of about 14% or greater at room temperature. Much larger values the JMR (100% more) are observed when actual tunneling resistance (RT) is comparable to electrode film (RL) over junction area. This latter apparent an artifact nonuniform current flow in cross geometry electrodes. The ferromagnetic films were CoFe and Co Ni0.8Fe0.2, barrier was AlN Al2O3. These nonvolatile memory effects....
Bit error rates below 10 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{-11}$</tex> </formula> are reported for a 4-kb magnetic random access memory chip, which utilizes spin transfer torque writing on tunnel junctions with perpendicular anisotropy. Tests were performed at wafer level, and error-free operation was achieved ns write pulses all nondefective bits during 66-h test. Yield in the array...
We report switching performance of perpendicularly magnetized Spin-Transfer Torque MRAM (STT-MRAM) devices with double tunnel barriers and two reference layers. show that stacks improve the efficiency (Eb/Ic0) by 2x, when compared to similar a single barrier. Switching up 10 kBT/uA was observed in devices. A large operating window, Vbreakdown-Vc10ns ∼ 0.7 V achieved for 40nm devices, 0.2V barrier
A three-terminal spin-torque-driven magnetic switch is experimentally demonstrated. The device uses nonlocal spin current and accumulation as the main mechanism for current-driven switching. It separates current-induced write operation from that of a tunnel junction based read. only passes through metallic structures, improving reliability. structure makes efficient use lithography capabilities, important robust process integration.
For CoFeB∕MgO-based magnetic tunnel junctions, the switching probability has an unusual dependence on bias voltage V and field H for pulse durations t long enough to allow thermally activated reversal. At high junction close 1V, of in spin-torque-driven switches sometimes appears decrease. This is shown be due a backhopping behavior occurring at bias, it asymmetric voltage, being more pronounced direction antiparallel-to-parallel spin-torque switch, i.e., electrons tunneling into free layer....
We report for the first time reliable 2 ns switching of spin-transfer torque magneto-resistive random access memory (STT-MRAM) devices by demonstrating 100% write-error-rate (WER) yield at 1e-6 write-error floor 254 with tight distributions and steep WER slope a nominal size 49 nm. A single device was demonstrated write pulses to have less than 1e-11 rate, limited only test time. further demonstrate 3 performance, 99% 256 43 nm rate completely different free layer materials design. These two...
The magnetotransport behavior of magnetic tunnel junctions with a nonmagnetic interface layer has been studied. initial effect the added is to reduce magnetoresistance effect. Also, bias voltage dependence becomes increasingly more asymmetric. both on thickness as well can be interpreted signatures development quantum states.
The influence of an inhomogeneous current density on the (magneto)resistance a ferromagnet–insulator–ferromagnet tunnel junction in cross-strip geometry is analyzed using finite element approach. four-probe resistance smaller than actual for electrode resistances (in area) comparable to or higher resistance. Even negative can be obtained. apparent change due magnetoresistive effect also decreases, but always remains positive. This results unrealistically large magnetoresistance ratios which...
We report data from 4-kbit spin torque MRAM arrays using tunnel junctions (TJs) with magnetization perpendicular to the wafer plane. show for first time switching distribution of junctions. The percentage voltage width, σ(V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> )/<V > = 4.4%, is sufficient yield a 64 Mb chip. Furthermore we probability curves down error probabilities 5×10 <sup...
Micromagnetic structures in submicron size circular permalloy elements of various thickness (5–50 nm) have been experimentally studied using a magnetic force microscope (MFM). One and two vortex micromagnetic states were observed the elements. It was found that one state is more favorable under external field low values, while forms high fields. Switching between results hysteresis response The transition from to increases with increase element and, therefore, demagnetizing effect edges. not...
Two breakdown mechanisms are observed in magnetic tunnel junctions having an ultrathin alumina barrier. The two manifest themselves differently when considering large ensembles of nominally identical devices under different stress conditions. results suggest that one type occurs because the intrinsic a well-formed oxide barrier can be described by E model dielectric breakdown. other is extrinsic related to defects rather than failure integrity. characteristic suggests pre-existing pinhole...
Current-induced spin-torque switching was demonstrated on sub-100 nm magnetic tunnel junction devices fabricated 200 mm substrates utilizing 180 complimentary metal–oxide–semiconductor back-end-of-the-line (BEOL) technology. Low resistance-area (RA) product and high tunneling magnetoresistance (TMR) were achieved by using containing a CoFeB free layer thin MgO barrier. To obtain the desired features, photoresist trimming applied patterns created 248 lithography tool. Furthermore, stack...
We have demonstrated a robust magnetic tunnel junction (MTJ) with resistance-area product RA=8 Ω—μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> that simultaneously satisfies the statistical requirements of high tunneling magnetoresistance TMR ≫ 15σ(R <inf xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> ), write threshold spread σ(Vw)/≪Vw≫ ≪7.1%, breakdown-to-write voltage margin over 0.5V, read-induced disturbance rate below 10...
CoFeB-based magnetic tunnel junctions with perpendicular anisotropy are used as a model system for studies of size dependence in spin-torque–induced switching. For integrated solid-state memory applications, it is important to understand the and electrical characteristics these they scale junction size. Size-dependent energy, switching voltage, apparent damping, field systematically compared devices different materials fabrication treatments. Results reveal presence sub-volume thermal...
We introduce a new device for reducing the switching current, Ic, in Spin-Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM). The Double Spin-torque Magnetic Tunnel Junction (DS-MTJ) uses spin torque from both top and bottom free-layer interfaces to reduce Ic by 2x. However, unlike previous work using Junctions (DMTJs), DS-MTJ does not suffer reduced magneto resistance (MR) due increased series resistance. Experimental data 10 ns write pulses demonstrates 2x reduction reliable...
Magnetic tunnel junctions have been fabricated by magnetron sputtering and patterned deep ultraviolet photolithography. The magnetoresistance was 15%–22% resistance times area product (R×A) 7–22 Ω μm2 for having 4.75–5.5-Å-thick Al layer oxidized naturally. Two types of breakdown were observed: abrupt dielectric at an effective field 10 MV/cm determined the thickness barrier, a gradual related to defects in barrier. After metallic pinhole is created, size which depends on maximum current...