The Kynix Blog - Memory

SummaryMemory is one of the most important part for electronics. Computers and Smartphones woludn't be nearly as useful without room for lots of apps,music and videos. Devices tend to store that  information in two ways: through electric fields (think of a flash drive) or through magnetic fields (like a computer’s spinning hard disk). Each method has advantages and disadvantages. However, in the future, our electronics could benefit from the best of each. There are some questions put by Chang-Beom Eom, the Theodore H. Geballe Professor and Harvey D. Spangler Distinguished Professor of Materials Science and Engineering at the University of Wisconsin-Madison. “Can you cross-couple these two different ways to store information? Could we use an electric field to change the magnetic properties? Then you can have a low-power, multifunctional device. We call this a ‘magnetoelectric’ device.” In research published recently in the journal Nature Communications, Eom and his collaborators describe not only their unique process for making a high-quality magnetoelectric material, but exactly how and why it works. Physics graduate student Julian Irwin checks equipment in the lab of materials science and engineering Professor Chang-Beom Eom, where researchers have produced a material that could exhibit the best qualities of both solid-state and spinning disk digital storage. Magnetoeletric materialsMagnetoelectric materials,which have both magnetic and electrical functionalities,or "orders" already exist. Switching one functionality induces a change in the other.“It’s called cross-coupling,” says Eom. “Yet, how they cross-couple is not clearly understood.” Gaining that understanding, he says, requires studying how the magnetic properties change when an electric field is applied. Up to now, this has been difficult due to the complicated structure of most magnetoelectric materials. In the past,people studied magnetoelectric properties using very "complex" materials,or those that lack uniformity.In his approach,Eom simplified not only the research but the material itself. Drawing on Eom's expertise in material growth,he developed a unique process,using atomic "steps" to guide the growth of a homogenous,single-crystal thin film of bismuth ferrite. Atop that, he added cobalt, which is magnetic; on the bottom, he placed an electrode made of strontium ruthenate.  Bismuth Ferrite MaterialThe bismuth ferrite material was important because it made it much easier for Eom to study the fundamental magnetoelectric cross-coupling. Eom found that in their work,because of their single domain,they could actually see what was going on using multiple probing, or imaging, techniques.The mechanism is intrinsic. It’s reproducible — and that means you can make a device without any degradation, in a predictable way. To image the changing  electric and magnetic properties switching in real time, Eom and his colleagues used the powerful synchrotron light sources at Argonne National Laboratory outside Chicago, and in Switzerland and the United Kingdom. “When you switch it, the electrical field switches the electric polarization. If it’s ‘downward,’ it switches ‘upward,'” he says. “The coupling to the magnetic layer then changes its properties: a magnetoelectric storage device.” That change in direction enables researchers to take the next steps needed to add programmable integrated circuits — the building blocks that are the foundation of our electronics — to the material. While the homogenous material enabled Eom to answer important scientific questions about how magnetoelectric cross-coupling happens, it also could enable manufacturers to improve their electronics.Eom saied they can design a much more effective,efficient and low-power device now. 

A device that turns light into sound has allowed researchers to capture lightning in a bottle, in a sense, slowing down the light beams enough so that they can be easily stored and manipulated. Researchers at the University of Sydney in Australia, have figured out how to turn a light wave into a sound wave, creating an acoustic memory that they say will help data centers save energy by eliminating some electrical connections between processors. They reported their work in a recent issue of Nature Communications. “Our vision is to replace the electronic interconnects between different processors and computing machines with photonic ‘wires,’’’ said Birgit Stiller, a postdoctoral researcher who led the project. “So light transmission will be used instead of electronic connections.” The team built a chip that consists of a spiral-shaped waveguide made from a soft glass called chalcogenide, sandwiched between two stiffer pieces of silica glass. As a light beam travels through the chip, it is met by another pulse of light that has a slightly different frequency. The difference between the frequencies of the two light beams is a “beat,” a wave with a frequency 100,000 times lower, thus turning the light wave into a sound wave.  The sound wave lives for a brief time—several nanoseconds—in the spiral chalcogenide waveguide. To read it out, the device reverses the process, adding the beat frequency to a light pulse to recreate the original light wave. In standard optical fibers, light waves are prevented from leaking out of the fiber by a difference in refractive index between the core of the fiber and the cladding wrapped around it. In a similar way, the two types of glass keep the sound wave in place; the speed of sound is much slower in the chalcogenide than in the silica. Slowing down the waves provides time to synchronize different signals coming from different processors. That eliminates the need to convert the optical signal to an electronic signal. Electronics can produce excess heat and require more energy, which are important issues in the big data centers owned by Google, Amazon, or Microsoft, Stiller says. Further work with the design and materials might allow the sound waves to be stored longer, although the memory already lasts long enough for the use they envision. She and her team hope to refine the work further, with an eye to building a prototype of a manufacturable chip within the next few years. 

An entirely new model of the way electrons are briefly trapped and released in tiny electronic devices suggests that a long-accepted, industry-wide view is just plain wrong about the way these captured electrons affect the behavior of hardware components such as flash memory cells. The model which devised by scientists at the National Institute of Standards and Technology (abbreviation NIST),a measurement standards laboratory, and a non-regulatory agency of the United States Department of Commerce and its mission is to promote innovation and industrial competitiveness, was test to explain how electron capture and emission creates the insidious nosise that increasingly threatens performance as electronic devices continue to shrink in size.   KIN Cheung, NIST researcher Kin Cheung also the lead author of a new report in IEEE Transactions on Electron Devices said "Such a burst noise,popcorn noise or random telegraph noise(abbreviation RTN) have become a major problem for extremely small devicess". Charge trapping is one of the known causes of flash memory failure. The new model, which NIST physicist John Kramar called "a major paradigm shift in charge-trapping modeling," could lead to a different approach to manage this problem, and potentially, a new way of making the memory cells smaller. John Kramar explained:" Charge trapping is one of the known causes of flash memory failure,the new model whicl I called it a major paradigm shift in charge-trapping modeling,could lead to a different approach to manage this problem,and potentially,a new way of making the memory cells smaller.  What is RTN noise? RTN noise consists of abrupt random drops in voltage or current caused by itinerant electrons that are briefly captured from, and then rejoin, the main flow along a current channel in, for example, a common type of transistor called a MOSFET. "The effect was mostly negligible back in the good old days when devices were larger and there were lots of electrons flowing around," Cheung said. But in today's advanced devices, with feature dimensions in the range of 10 nanometers (nm, billionths of a meter) or less, the active area is so small that it can be swamped by a single trapped charge. "As you get down to the very smallest sizes, RTN can be nearly 100 percent as strong as the signal you're trying to measure," Cheung said. "In those conditions, reliability disappears." In the case of RTN, the basics are known: The noise is caused by the action of electrons near the interface between two materials such as an insulator layer and the bulk of the semiconductor in a transistor. Specifically, an electron is pulled out of the current flow and trapped in a defect in the insulator; after a short time, it is emitted back into the main current in the semiconductor. What actually happens on the atomic scale at each stage of the process, however, is incompletely understood. The orthodox approach to account for those effects is to treat all the trapped electrons as a single 2-D sheet of charge that extends uniformly across the center of the insulator. Each emitted electron is thought to return to the semiconductor in a reverse of the same process by which it was captured, causing very little change in the presumably stable state along the insulator/semiconductor boundary. The model is suitable for very small devices,however,it didn't make sense to the NIST scientists. Among other difficulties, it ignored the fact that, once they are immobilized, electrons cause considerable distortions in local electrical field conditions along the boundary, affecting current flow. "We're saying the traditional way doesn't really work," Cheung said. "You have to rethink this thing. The old model doesn't make reasonable assumptions about how charge carriers behave." The researchers proposed a new model, based on local effects, in which the mechanisms of capture and emission are dramatically different from the standard picture. For one thing, they determined that quantum mechanics, the modern theory that describes the behavior of these systems, makes it hugely improbable, if not impossible, for electrons to get out of the insulator the same way they got in. "It's like a highway where there is an exit ramp, but there's no on ramp," says NIST co-author Jason Campbell. "You can go in, but you can't come back that way. You've got to come back a different way. That is, there is a set of rules for capture that don't apply to emission." "When you realize that the capture and emission processes are decoupled," Cheung added, "you quickly have a very different view of the problem."  The standard RTN picture supposes a weak interaction of trapped charge with its local surroundings―in this case, the highly separated electric charge in the silicon dioxide that often makes up the insulator layer in a transistor. NIST scientists found that a weak interaction is inconsistent with known physics and not in agreement with reports from two independent laboratories. Indeed, the interaction energy of a captured electron can be more than 10 times greater than previously believed. Recognition of this stronger interaction energy enables the new local field picture to explain RTN naturally. The success of the new model, and the resulting drastic change in the understanding of both capture and emission, suggested that many long-held ideas would have to be thoroughly reconsidered. "It's a very scary and very unsetting conclusion,I mean,this is tear-up-the textbook stuff." Campbell said. As an end, NIST researchers hope the new model will help chip engineers and designers understand in much greater detail how devices degrade and hat will be required to get to the next stage of miniaturization while maintaining reliability and reducing noise. 

As one of the world-leading research and innovation hub in nanoelectronics and digital technology,IMEC announced at the 2017 Symposia on VLSI Technology and Circuits that the world's first demonstration of a vertically stacked ferroelectric,AI doped HfO2 device for NAND applications.Using a new material and a novel architecture,imechas created a non-volatile memory concept with attractive characteristics for power consumption, switching speed, scalability and retention. The achievement shows that ferro-electric memory is a highly promising technology at various points in the memory hierarchy, and as a new technology for storage class memory. Imec will further develop the concept in collaboration with the world's leading producers of memory ICs.  Ferro-electric materials consist of crystals that exhibit spontaneous polarization; they can be in one of two states, which can be reversed with a suitable electric field. This non-volatile characteristic resembles ferromagnetism, after which they have been named. Discovered more than five decades ago, ferro-electric memory has always been considered ideal, due to its very low power needs, non-volatile character and high switching speed. However, issues with the complex materials, the breakdown of the interfacial layer and bad retention characteristics have presented significant challenges. The recent discovery of a ferro-electric phase in HfO2, a well-known and less complex material, has triggered a renewed interest in this memory concept.  "With HfO2, there is now a material with which we can process ferro-electric memories that are fully CMOS compatible. This allows us to make a ferro-electric FET (FeFET) in both planar and vertical varieties," noted Jan Van Houdt, imec's chief scientist for memory technology. "We are working to overcome some of the remaining issues, such as retention, precise doping techniques and interface properties, in order to stabilize the ferro-electric phase. We are now confident that our FeFET concept has all the required characteristics. It is, in fact, suitable for both stand-alone and embedded memories at various points in the memory hierarchy, going all the way from non-volatile DRAM to Flash-like memories. It has particularly interesting characteristics for future storage-class memory, which will help overcome the current bottleneck caused by the differences in speed between fast processors and slower mass memory." Imec recently presented the first, extremely positive results to its partners. The research center is now offering further development and industrialization of the vertical FeFET as a program to all its memory partners, which include the world's major companies producing memory ICs.  Van Houdt explained "FeFETs can be used as a technology to build memory very similar to Flash-memory, but with additional advantages for further scaling, simplified processing, and power consumption,with our longstanding R&D and processing experience on advanced Flash, we are uniquely positioned to offer our partners a head start in this exciting opportunity. They can then decide how best to fit ferro-electric memories in their products and chips." This is a breakthrough in CMOS-compatible ferroelectric memory, let's look forward to the CMOS-compatible ferroelectric memory together.  

A Tomsk Polytechnic University study reveals how topological vortices found in low-dimensional materials can be both displaced and erased and restored again by the electrical field within nanoparticles. This may open exciting opportunities for memory devices or quantum computers in which information will be encrypted in the characteristics of topological vortices.(Vortices in nanoparticles exposed by the electrical field. Credit: Tomsk Polytechnic University (TPU))Scientists from TPU and international collaborators have discovered unusual self-organization of atoms in the volume of nanoparticles and have learned to control it via an electric field. Such controlled nanoparticles can be used to generate capacious non-volatile random access memory (NRAM), quantum computers and other next-generation electronics. The main author is Dmitriy Karpov, engineer of the Department of General Physics, TPU, who explains that in modern materials science, the defects of matter are divided into two large groups. The first group includes classical, well-studied defects, when atoms in matter are mechanically disordered, i.e., atoms are either removed or inserted into the lattice. In the other group, the spatial organization of the lattice itself changes and such defects are called topological. Topological defects can strongly influence matter, making it superfluid or superconductive, and therefore, it is very important to study them. Topological defects can be found only in low-dimensional materials—two-dimensional nanorods and nanofilms (just several atoms thick) and one-dimensional nanodots or nanoparticles, which are spherical particles consisting of several tens or hundreds of identical atoms. "One of the important topological defects is a topological vortex which looks like a discernible twisting caused by a small displacement of all atoms. The vortex core is a nanostrand which can be both displaced by the field, and erased and restored again within nanoparticles," explains Edwin Fohtung, Professor of Los Alamos National Laboratory and New Mexico State University . The scientists studied barium titanate nanoparticles whose internal structure was visualized with the help of penetrating X-ray radiation from the synchrotron Advanced Photon Source (Chicago, USA). They obtained an image of the volume of nanoparticles with a resolution of 18 nanometers, which enabled them to analyze the slightest changes in the structure. As a result, the researchers showed that an external electric field can displace the core of the topological vortex inside the nanoparticle, and when the field is removed, it returns to its original position. Modern components of electronics are gradually becoming smaller. This can significantly influence the efficiency of devices, which will be significantly reduced due to quantum effects. One way to circumvent these limitations is to use topological vortices. Thus, they can be used to generate high density NRAM or quantum computers in which information will be encrypted in the characteristics of topological vortices. "All in all, the possibility to control and adjust topological vortices in nanoparticles is important for the creation of new electronics," concludes Dmitriy Karpov. Further reading>>>Topological defectA topological defect can be proven to exist[when?] because the boundary conditions entail the existence of homotopically distinct solutions. Typically, this occurs because the boundary on which the conditions are specified has a non-trivial homotopy group which is preserved in differential equations; the solutions to the differential equations are then topologically distinct, and are classified by their homotopy class. Topological defects are not only stable against small perturbations, but cannot decay or be undone or be de-tangled, precisely because there is no continuous transformation that will map them (homotopically) to a uniform or "trivial" solution. Reference>>>KY259-BB910KY259-CXA1512MKY32-K9T1G08U0M-YIBO 

(Steve Cain is a senior research support specialist in the Integrated Electronics Engineering Center (IEEC) at Binghamton University. Credit: Jonathan Cohen/Binghamton University)While investigating mass transit accidents, especially in air travel, National Transportation Safety Board (NTSB) officials often rely on digital clues left behind in flash memories of any and all electronic devices—both personal and professional—at a crash site. With the physical forces and high-temperature fires associated with many crashes, memory units are often damaged and sometimes unreadable.Researchers at Binghamton University, State University of New York have figured out how much damage memory units can sustain before becoming unreadable and new repair techniques to retrieve clues off of damaged units, which might help prevent future tragedies."The biggest surprise was how much punishment these devices can take before ceasing to function," said Steve Cain, who is the project manager and a senior research support specialist in the Integrated Electronics Engineering Center (IEEC) at Binghamton University. "As part of their post-crash investigations, the NTSB collects anything and everything at the scene, including personal electronic devices. If the device was active during or just before the crash, it is possible that the data stored in the memory can provide clues as to the cause of the crash. Most of the time the device is ruined, but sometimes it is intact."The interdisciplinary Binghamton group of Cain, Preeth Sivakumar, Jack Lombardi, and Mark Poliks along with James Cash, Joseph Gregor, and Michael Budinski from the NTSB, presented "Fire Damage and Repair Techniques for Flash Memory Modules: Implication for Post-Crash Investigations" at the Fall 2016 International Symposium of Microelectronics.Scientists found plastic coverings started to break down after three hours of exposure to temperatures of 300 degrees Celsius, or about 572 degrees Fahrenheit or more, but memory chips were still readable.Researchers pointed out that even with the pressures and forces in play during past crashes, temperatures typically only reach those levels for short periods of time."Data integrity was maintained even in a plasma discharge," Cain said. "Basically, if the device doesn't burn up, there is a reasonable chance of the data being retained in the chip. The only problem is that the connections to the memory chips may be broken, so that the data cannot be read."For the second part of the study, researchers addressed the readability issue. The team purposely damaged memory units and then extracted memory chips using acid, lasers, plasma, or mechanical polishing.Lasers were the most effective extraction method and mechanical extractions was the simplest, but each method still damaged the wire bonds within memory chips and made many unreadable. A specialized metallic ink from a precision printer was used to restore functionality."These results expand the investigative scope for aviation accidents, where the data rather than the device is of paramount importance," the team concluded. "It is possible to repair the interconnections of flash memory modules, provided the chip is intact." Ref.AT27C1024-45JCEDD10161BBH-6ETS-F