Advanced Memory Research Articles

Si-Doped HfO2-Based Ferroelectric Tunnel Junctions with a Composite Energy Barrier for Non-Volatile Memory Applications.

Ferroelectric tunnel junctions (FTJs) have attracted attention as devices for advanced memory applications owing to their high operating speed, low operating energy, and excellent scalability. In particular, hafnia ferroelectric materials are very promising because of their high remanent polarization (below 10 nm) and high compatibility with complementary metal-oxide-semiconductor (CMOS) processes. In this study, a Si-doped HfO2-based FTJ device with a metal-ferroelectric-insulator-semiconductor (MFIS) structure was proposed to maximize the tunneling electro-resistance (TER) effect. The potential barrier modulation effect under applied varying voltage was analyzed, and the possibility of its application as a non-volatile memory device was presented through stability assessments such as endurance and retention tests.

The Olfactory Tract: Basis for Future Evolution in Response to Rapidly Changing Ecological Niches.

Within the forebrain the olfactory sensory system is unique from other sensory systems both in the projections of the olfactory tract and the ongoing neurogenic potential, characteristics conserved across vertebrates. Olfaction plays a crucial role in behaviors such as mate choice, food selection, homing, escape from predators, among others. The olfactory forebrain is intimately associated with the limbic system, the region of the brain involved in learning, memory, and emotions through interactions with the endocrine system and the autonomic nervous system. Previously thought to lack a limbic system, we now know that teleost fishes process emotions, have exceptional memories, and readily learn, behaviors that are often associated with olfactory cues. The association of neuromodulatory hormones, and more recently, the immune system, with odor cues underlies behaviors essential for maintenance and adaptation within natural ecological niches. Increasingly anthropogenic perturbations affecting ecosystems are impacting teleost fishes worldwide. Here we examine the role of the olfactory tract as the neural basis for the integration of environmental cues and resulting behaviors necessary for the regulation of biotic interactions that allow for future adaptation as the climate spins out of control.

NIH Toolbox® Episodic Memory Measure Differentiates Older Adults with Exceptional Memory Capacity from those with Average-for-Age Cognition.

Older adults with exceptional memory function, designated "SuperAgers," include individuals over age 80, with episodic memory at least as good as individuals ages 50s-60s. The Northwestern University SuperAging cohort is defined by performance on an established test of verbal memory. The purpose of this study was to determine if superior verbal memory extends to nonverbal memory in SuperAgers by examining differences in the National Institutes of Health Toolbox® (NIHTB) between older adults with exceptional memory and those with average-for-age cognition. SuperAgers (n=46) and cognitively average-for-age older adults (n=31) completed a comprehensive neuropsychological battery and the NIHTB Cognition module. Multiple linear regressions were used to examine differences on subtests between groups. There was a significant effect of group on the Picture Sequence Memory score, (p=.007), such that SuperAgers had higher scores than cognitively average-for-age older adults. There were no other group effects across other non-episodic memory NIHTB Cognition measures. Findings from this study demonstrated stronger performance on the memory measure of the NIHTB in SuperAgers compared to cognitively average-for-age older adults demonstrating superior memory in not only verbal but also nonverbal episodic memory in this group. Additionally, this study adds to the literature validating the NIHTB in older adults, particularly in a novel population of adults over age 80 with exceptional memory.

Recent Progress in Crystallographic Characterization, Magnetoresponsive and Elastocaloric Effects of Ni-Mn-In-Based Heusler Alloys—A Review

Ni-Mn-In-based magnetic shape memory alloys have promising applications in numerous state-of-the-art technologies, such as solid-state refrigeration and smart sensing, resulting from the magnetic field-induced inverse martensitic transformation. This paper aims at presenting a comprehensive review of the recent research progress of Ni-Mn-In-based alloys. First, the crystallographic characterization of these compounds that strongly affects functional behaviors, including the crystal structure of modulated martensite, the self-organization of martensite variants and the strain path during martensitic transformation, are reviewed. Second, the current research progress in functional behaviors, including magnetic shape memory, magnetocaloric and elastocaloric effects, are summarized. Finally, the main bottlenecks hindering the technical development and some possible solutions to overcome these difficulties are discussed. This review is expected to provide some useful insights for the design of novel advanced magnetic shape memory alloys.

An Unwavering Passion: Doran Ross's Scholarship on Asafo Flags

An Unwavering Passion: Doran Ross's Scholarship on Asafo Flags

Synthesis of novel FeM (Co, Ni, Cu & Zn)/PDMS for magnetic actuators thin film fabrication by greener route

A novel PDMS-bimetallic magnetic nanoparticle thin films based magnetic actuators have been fabricated using an eco-friendly cost-effective facile method. The magnetic thin films have received greater attention for their variety of specialized applications, particularly in the medical field. Actuators find very broad applications in microfabrication, microelectronics, medicine, and lab-on-a-chip systems. The FeM(Co/Ni/Cu/Zn) bimetallic magnetic nanoparticles have been synthesized through greener Mimosa Pudica leaf extract. These synthesized nanoparticles are combined with PDMS polymer to form flexible thin films to fabricate magnetic actuators. Optical characterization of the FeM nanoparticles showed a broad plasmon absorption band around 1100–1600 nm, and their corresponding thin-film absorption band shifted negligibly. The magnetic investigations showed that the obtained nanoparticles and their thin films are ferromagnetic with a significant remanent magnetization. Particularly Fe-Cu magnetic NPs and their FeCu@PDMS film displayed 90.82, 55.79 emu/g Ms and 33.34, 11.68 emu/g Mr values at 300 K respectively. These results make the FeM@PDMS flexible films are promising for advanced magnetics memory devices and magnetic induced actuators fabrication.

Microsphere-assisted, nanospot, non-destructive metrology for semiconductor devices

As smaller structures are being increasingly adopted in the semiconductor industry, the performance of memory and logic devices is being continuously improved with innovative 3D integration schemes as well as shrinking and stacking strategies. Owing to the increasing complexity of the design architectures, optical metrology techniques including spectroscopic ellipsometry (SE) and reflectometry have been widely used for efficient process development and yield ramp-up due to the capability of 3D structure measurements. However, there has been an increasing demand for a significant reduction in the physical spot diameter used in the SE technique; the spot diameter should be at least 10 times smaller than the cell dimension (~30 × 40 μm2) of typical dynamic random-access memory to be able to measure in-cell critical dimension (CD) variations. To this end, this study demonstrates a novel spectrum measurement system that utilizes the microsphere-assisted super-resolution effect, achieving extremely small spot spectral metrology by reducing the spot diameter to ~210 nm, while maintaining a sufficiently high signal-to-noise ratio. In addition, a geometric model is introduced for the microsphere-based spectral metrology system that can calculate the virtual image plane magnification and depth of focus, providing the optimal distance between the objective lens, microsphere, and sample to achieve the best possible imaging quality. The proof of concept was fully verified through both simulations and experiments for various samples. Thus, owing to its ultra-small spot metrology capability, this technique has great potential for solving the current metrology challenge of monitoring in-cell CD variations in advanced logic and memory devices.

PEzoNG: Advanced Packer For Automated Evasion On Windows

The ability to evade Antivirus analyses is a highly coveted goal in the cybersecurity field, especially in the case of Red Team operations where advanced external threats against a target infrastructure are performed. In this paper we present the design and implementation of PEzoNG, a framework for automatically creating stealth binaries that target a very low detection rate in a Windows environment. PEzoNG features a custom loader for Windows binaries, polymorphic obfuscation, a payload decryption process and a number of anti-sandbox and anti-analysis evasion mechanisms, including a novel user space unhooking technique. In addition, the custom loader supports a large amount of Windows executable files, and features stealth and advanced memory allocation schemes. We evaluate the effectiveness of PEzoNG by testing various malicious payloads against up to 29 commercial Antivirus solutions, and we highlight and discuss the assets and differences of PEzoNG with respect to similar tools.

Bonding Nature and Optical Properties of As2Te3 Phase‐Change Material

Chalcogenide phase‐change materials (PCMs) are a promising candidate for advanced memory and computing technologies. PCM‐based random access memories have entered the global memory market as storage‐class memory. In these products, the element arsenic plays an essential role in the selector layers, but how arsenic stabilizes the thermal stability of the chalcogenide glass remains elusive. Herein, thorough ab initio simulations are carried out to understand the chemical bonding, electronic structure, and optical properties of an important arsenic alloy As2Te3 in both crystalline and amorphous forms. In comparison with the homologue alloy Sb2Te3, the importance of homopolar bonds in stabilizing the amorphous phase of As2Te3 is revealed. Also, a strategy for the design of As x Sb2−x Te3 alloys with optimal material properties for nonvolatile photonic phase‐change applications is proposed.

Discrete resistive switching characteristics in metal-free phthalocyanine and Dy-phthalocyanine based devices

The resistive memory devices based on planar metal-free phthalocyanine (H2Pc) and sandwiched Dy-phthalocyanine (DyPc2) have been prepared on an ITO glass substrate with the Al as a top electrode. The current-voltage characteristics of these devices are found to be relevant with the interlayer thickness and the crystalline structure. Both the average values of reset and set voltage increased with the increasing thickness of interlayer. The devices can be cycled more than 150 consecutive cycles when the thickness of H2Pc and DyPc2 are 60 nm and 30 nm, respectively. The resistances of present H2Pc devices are larger than that of DyPc2 devices, which may be related to different orientations of H2Pc and DyPc2 films. Additionally, a high ON/OFF current ratio of about 103 and a long retention ability of over 104 s were achieved for both devices, implying their nonvolatile storage capacity. An analysis of the current-voltage characteristics revealed that the electrical conduction behavior followed the space charge limited conduction mechanism. This study is useful to design advanced resistive memory devices and understand the underlying resistive switching mechanism.

Phase transitions in ferroelectric domain walls

Despite multiple efforts, there exist many unsolved fundamental problems related with detection and analysis of internal polarization structure and related phase transitions in ferroelectric domain walls. Their solution can be very important for the progress in domain wall nanoelectronics and related applications in advanced memories and other information technologies. Here, we theoretically study the features of phase transitions in the domain walls, which are potentially detectable by the scanning probe capacitance microwave microscopy. The finite element modelling based on the Landau-Ginzburg-Devonshire theory is performed for the capacitance changes related with the domain wall motion in a multiaxial ferroelectric BaTiO3.

Modern Value Based Reinforcement Learning: A Chronological Review

Investigation of value based Reinforcement Learning algorithms exhibited a resurgence into mainstream research in 2015 following demonstration of super-human performance when applied to Atari 2600 games. Since then, significant media attention and hype have accompanied this area, and the field of Artificial Intelligence generally, spread across distinct categories. This review paper is focused exclusively on the progression of value based Reinforcement Learning in the last five years. We aim to distill the incremental improvements to stability and performance in this period, highlighting the minimal changes to the base algorithm over this time. This holds true with all but the one exception of the Recurrent Experience Replay in Distributed Reinforcement Learning algorithm, representing a fundamental shift and increase in agent performance through an advanced memory representation. We suggest a new focus area for value based Reinforcement Learning research.

NIH toolbox episodic memory measure differentiates older adults with exceptional memory capacity from those with average memory

AbstractBackground“SuperAgers” are older adults over the age of 80 with exceptional memory abilities, at least as good as cognitively average individuals in their 50s and 60s. The purpose of this study was to compare SuperAgers with their cognitively normal‐for‐age peers on subtests of the NIH Toolbox Cognition Battery (NIHTB‐CB), including a test of nonverbal picture sequence memory.MethodParticipants categorized as SuperAgers (n=46) or as cognitively average‐for‐age (n=31) completed standard neuropsychological tests of attention, executive functions, language, and episodic memory. SuperAgers are classified by a delayed recall score on the Rey Auditory Verbal Learning Test that falls at or above the average score of 50 to 65‐year‐old norms, while scores in non‐memory domains must be at least in the average range for age. Multivariable linear regression models were used to examine differences across subtests between the groups.ResultAfter controlling for IQ, gender, age, and education, Picture Sequence Memory Scores were higher in Super Agers than in the cognitively normal‐for‐age group (p = 0.007). However, the groups did not differ in their scores on all other Cognition measures.ConclusionFindings from this study demonstrated that SuperAgers scored higher on a test of nonverbal memory in the NIHTB‐CB compared to cognitively average‐for‐age peers, while groups scored similarly on non‐memory domains. These findings demonstrate that memory abilities in SuperAgers are strong not only on tests of verbal memory, but on nonverbal measures, as well. These findings extend the potential to identify SuperAgers with more efficient assessment methods.

Reduction of advanced tau-mediated memory deficits by the MAP kinase p38γ.

Hyperphosphorylation of the neuronal tau protein contributes to Alzheimer's disease (AD) by promoting tau pathology and neuronal and cognitive deficits. In contrast, we have previously shown that site-specific tau phosphorylation can inhibit toxic signals induced by amyloid-β (Aβ) in mouse models. The post-synaptic mitogen-activated protein (MAP) kinase p38γ mediates this site-specific phosphorylation on tau at Threonine-205 (T205). Using a gene therapeutic approach, we draw on this neuroprotective mechanism to improve memory in two Aβ-dependent mouse models of AD at stages when advanced memory deficits are present. Increasing activity of post-synaptic kinase p38γ that targets T205 in tau reduced memory deficits in symptomatic Aβ-induced AD models. Reconstitution experiments with wildtype human tau or phosphorylation-deficient tauT205A showed that T205 modification is critical for downstream effects of p38γ that prevent memory impairment in APP-transgenic mice. Furthermore, genome editing of the T205 codon in the murine Mapt gene showed that this single side chain in endogenous tau critically modulates memory deficits in APP-transgenic Alzheimer's mice. Ablating the protective effect of p38γ activity by genetic p38γ deletion in a tau transgenic mouse model that expresses non-pathogenic tau rendered tau toxic and resulted in impaired memory function in the absence of human Aβ. Thus, we propose that modulating neuronal p38γ activity serves as an intrinsic tau-dependent therapeutic approach to augment compromised cognition in advanced dementia.

AB018. Advances in mediastinal tumors diagnosis: J. Rosai, a master of Pathology, and the value of morphology and related disciplines

Background: In the last 60 years, significant progresses were made in diagnostics of mediastinal tumors from the confusing existing situation. Finally, with the immunological discovers concerning thymic functions, a new era began due to the excellent diagnostic skill of Juan Rosai. He was born in Italy, Poppi, in 1940. Emigrated to Argentina with the family, after his degree in Medicine and training in pathology, J. Rosai was invited to join United States and in short, he was very well appreciated in the group of Lauren Ackerman. He was Professor and Chairman of Pathology in several University, in United States and Director of the Pathology Department at the National Cancer Institute in Milan, Italy. His excellent morphologic skill, comprehensive understanding of diagnostic patterns and exceptional memory rendered him a Master in pathology and in Surgical Pathology.

Room-temperature large magnetoelectricity in a transition metal doped ferroelectric perovskite

There is increasing interest in novel magnetoelectric (ME) materials that exhibit robust ME coupling at room temperature (RT) for advanced memory, energy, spintronics, and other multifunctional device applications, by making use of the ability to control polarization with a magnetic field and/or magnetization via an electric field. Obtaining ME materials with strong ME coupling, understanding the origin, and manipulating its processing along with composition to realize large ME coefficients at RT constitute an important step in multiferroic research. To address this, we have investigated the multiferroic and ME properties of Ni-doped $\mathrm{Pb}({\mathrm{Zr}}_{0.20}{\mathrm{Ti}}_{0.80}){\mathrm{O}}_{3}$ (PZT). We find that the ferroelectric $({T}_{\mathrm{C}}\ensuremath{\sim}700\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ and weak ferromagnetic (\ensuremath{\sim}602 K) phase transitions of Ni-doped PZT are well above room temperature (RT), leading to a strong ME coupling coefficient (${\ensuremath{\alpha}}_{E,31}$) of $11.7\phantom{\rule{0.16em}{0ex}}\mathrm{mV}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{--1}\phantom{\rule{0.16em}{0ex}}{\mathrm{Oe}}^{--1}$ (${H}_{\mathrm{ac}}=1\phantom{\rule{0.16em}{0ex}}\mathrm{Oe}$ and $f=1\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$). While x-ray diffraction suggests a single-phase material, high-resolution transmission electron microscopy reveals regions with and without Ni present; thus magnetoelectric coupling between two phases is possible. First-principles calculations suggest the $(\mathrm{N}{\mathrm{i}}_{\mathrm{Pb}}{)}^{\ifmmode\times\else\texttimes\fi{}}$ defect is likely to be responsible for the experimental observed magnetism and ME coupling in Ni-doped PZT. We further demonstrate that Ni-doped PZT exhibits low loss tangent, low leakage current, large saturation polarization, and weak ferromagnetism. Ultimately, our work demonstrates that Ni-doped PZT is a cost-effective RT multiferroic with strong ME coupling.

Sub-resolution assist feature placement with generative adversarial network

Background: As the design layout of integrated circuits (ICs) is continually scaling down, sub-resolution assist features (SRAF) have been extensively used in resolution enhancement technique applications to enhance lithography printing fidelity and widen the manufacturing process window (PW). With conventional SRAF insertion techniques, rule-based SRAF (RB-SRAF) and model-based SRAF (MB-SRAF) methods have since been widely adopted. Aim: The typical RB-SRAF is an efficient method to generate SRAFs consistently for simple designs but cannot be optimized for multiple critical patterns or complex layout schemes. Although MB-SRAF is able to achieve better PW as well as reducing conflicts between placement rules and clean-up rules, many iterations for convergence and extremely high computational costs are required. The explosion of machine learning techniques could facilitate the complex processes of mask optimization, such as SRAF insertion. Approach: Generative adversarial network was studied on a Via layer of advanced 3D NAND flash memory, by training target images and Inverse Lithography Technology (ILT) images of target patterns. GAN models, pix2pix, and CycleGAN, were first trained and then utilized to synthesize realistic ILT images. Results: These ILT images were eventually translated to polygons of SRAF with simplification process and mask manufacturing rules check constraints. The simulation results demonstrate that CycleGAN approach can place SRAF with comparable performance to mask optimization (MO) result which was optimized by the Tachyon source-mask optimizer (SMO). Conclusions: Methodologies of SRAF placement based on GANs were demonstrated in this paper. While traditional MO approach showed the best lithography performance, CycleGAN in particular was close behind and had much better performance than conventional RB-SRAF approach, whilst achieving good stability for different layout environments. Most importantly, the efficiency of SRAF insertion can be enhanced significantly through GANs.

(Invited) Ultrathin Ferroelectric on Silicon and Application for Energy Efficient Logic and Memory Devices

Compared to archetypical perovskites, fluorite HfO2 based ferroelectric materials are process-compatible with advanced CMOS transistors. As a result, they promise to bring ferroelectric technologies into wide-spread applications. At the same time, ferroelectricity in these materials is also different. In conventional perovskites, the polarization becomes weaker as the thickness is decreased due to ‘size effects’. Balking this conventional trend, our recent work has shown that ferroelectricity in HfO2 in fact enhances as the thickness goes down. The ferroelectricity can be demonstrated even in a 1 nm film, which is just two unit cells! In this seminar I shall discuss these results. In addition, I shall also discuss Negative Capacitance transistors with just 18A thick ferroelectric material- the same thickness of high- dielectric used in today’s advanced transistors. I shall further present ferroelectric tunnel junction results with 1 nm ferroelectric. These results demonstrate that, unlike conventional ferroelectrics, thickness scaling is not a bottleneck for HfO2 based ferroelectrics, paving the way for their integration in the most advanced logic and memory devices.

(Keynote) Status & Challenges in Today's Atomic Layer Processing Market

The global market for atomic-layer deposition (ALD) and chemical-vapor deposition (CVD) metal precursors for semiconductor manufacturing in 2020 was worth ~US$640M [1]. Driven by advanced logic, DRAM and 3D-NAND memory chip fabrication needs, demand for ALD and CVD metal precursors is forecast to see a 2020-2025 compound annual growth rate (CAGR) of ~10%. In the short-term forecast, sees the global semiconductor market as very healthy with 15-20% Year-over-Year (YoY) growth in 2021 revenues [2], and overall critical materials market growth >7% YoY. The greatest material demand increases are seen in ALD/CVD metal precursors, and in specialty wet cleans that often are integrated with metal deposition and etching. All ALD/CVD metal precursors are in healthy demand, since ALD is critical for fabs running 22-45nm nodes as well as for fabs at the leading edge at 16/14 nm and below. In particular, cobalt (Co) and hafnium (Hf) precursors saw 18-20% year-over-year (YoY) growth in 2020, and are forecasted to see strong demand through 2025. Zirconium (Zr) used for DRAM capacitors saw a lower growth but is a big segment on its ow. Ruthenium (Ru) metal is slowly replacing some of the Co and tungsten (W) interconnects on the most advanced logic chips, with anticipated precursor revenue growth to US$10M in 2025 for this highly strategic material. Metals to observe the next years include molybdenum (Mo), niobium (Nb) and lanthanum (La). The long-term revenue outlook for precursors continues to be good driven by: replacement of PVD processes to meet challenging specification for 3D and high aspect ratio device architecture, driven my lateral and stacked scalingReplacement of high themperature diffusion processes (oxidation and nitridation) with low thermal budget plasma ALD processes.Implementation of leading-edge logic nodes with a higher penetration of ALD processes in automotive and the EV transition of the global vehicle fleet.Growing need for ALD films in new semiconductor device technologies and new products: Spin-transfer torque MRAM (STT-MRAM), Resistive RAM (ReRAM), Ferroelectric FET (FeFET) and RAM (FRAM) and Cross-Point memoryImplementation of ALD in emerging new technologies: Photovoltaic, Display, MEMS, Power Electronics, LED/µLED, Optical, Lithium Battery (EVs, Mobile), Parts and powder coating, Medical / Healthcare. New precursors will be needed to meet improved performance for 3D devices and lower thermal budgets as well as reduced cost of ownership. New metals and new metal precursors, mainly for interconnects and contacts, are being continuously researched (e.g. W, Co, Ru, La, Mn).ALD materials and Original Equipment Manufacturer (OEM) tools are needed for multi-patterning lithography used with Deep-UV (DUV) Immersion and with Extreme-UV (EUV) in leading logic and memory fabs. Multi-patterning typically uses low-temperature Plasma-Enhanced ALD (PEALD), either in clusters of 8-16 single-wafer chambers, or in “Spatial” high-throughput tools. It is anticipated that fab investments in Asia will allow South Korean and Chinese OEMs to win near-term ALD orders, and they may soon compete with US, EU, and Japanese OEMs in the global tool market for standard processes that are commoditized. Recent actions taken by the new US administration has boosted logic fab investments in the US and in total USD 70 B leading edge fab investments are on the horizon the next three years, which will generate a need for both ALD equipment and a healthy precursor supply chain on all materials above going forward.

A-17 Examining Cognitive Trajectories in SuperAgers within the LonGenity Study

Abstract Objective Rogalski and colleagues (2013) use the term SuperAgers to indicate individuals aged 80 and older who have exceptional memory with the goal of clarifying factors that impact successful aging. Using a modified definition, we explored cognitive trajectories of SuperAgers within our longitudinal study of the genetic factors associated with exceptional longevity (OPEL) in individuals of Ashkenazi Jewish descent. Method LonGenity Study participants complete annual physical and cognitive assessments which include the Free and Cued Selective Reminding Test (FCSRT) and WMS-R Logical Memory (LMI). All participants who completed a visit at age 80 were included in the analysis (N = 230; 56.5% female; mean education 17.57 ± 2.74 years; 46.5% OPEL; median follow-up 4 years). Twenty-one participants met modified SuperAger criteria (FCSRT: >38 and LMI: >25; no other cognitive impairment). Descriptive statistics, t-tests, and linear mixed effects models of cognitive trajectories were used to examine the differences between SuperAgers and non-SuperAgers. Results Although there were no differences in demographics or familial history of exceptional longevity, SuperAgers were less likely to have a history of cardiac problems (p = 0.02). Overall cognitive functioning remained stable with age in the SuperAgers, whereas non-SuperAgers demonstrated declining overall cognition with age (β = −0.029, CI: −0.036—0.022). Memory task performances demonstrated a similar discrepancy in trajectories. Conclusion(s) In our unique and high functioning population, SuperAgers as defined at age 80 do not demonstrate the typical cognitive declines thought to be associated with age. Vascular risk factors appear to play a role, but further investigation including exploring genetic markers and MRI is warranted.