Flash Technology Research Articles

A Progressive Performance Boosting Strategy for 3-D Charge-Trap NAND Flash

The growing demands of large-capacity flash-based storages have facilitated the downscaling process of NAND flash memory. However, the downscaling of traditional planar floating-gate flash memory faces several challenges. Therefore, new NAND flash technologies have been explored to provide larger capacity with low cost. Among these new technologies, the 3-D charge-trap flash is regarded as one of the most promising candidates. The 3-D charge-trap flash is composed of several gate-stack layers and vertical cylindrical channels to provide high-density and low cell-to-cell interference. Owing to the cylindrical geometry of vertical channels, the access performance of each page in one block is distinctive, and this situation is exacerbated in the 3-D charge-trap flash with the fast-growing number of gate-stack layers. In this paper, a progressive performance boosting strategy is proposed to boost the performance of 3-D charge-trap flash by utilizing its asymmetric page access speed feature. A series of experiments was conducted to demonstrate the capability of the proposed strategy on improving the access performance of 3-D charge-trap flash.

Characterization and Modeling of Temperature Effects in 3-D NAND Flash Arrays—Part II: Random Telegraph Noise

This paper investigates the temperature dependence of random telegraph noise (RTN) in 3-D NAND Flash technologies. Experimental results on memory arrays reveal an increase of RTN when temperature is reduced, which is mainly attributed to the growth of the amplitude of the fluctuations arising from RTN traps. A direct proof of this growth is provided by directly monitoring some RTN waveforms arising from single traps in cells out of either memory arrays or test elements. In order to explain this evidence, the TCAD model for polysilicon NAND strings presented in Part I of this paper is adopted and extended to address the amplitude of the threshold-voltage shift coming from the trapping of a single electron at different positions in cell channel. Numerical results successfully reproduce the experimental trends with temperature and allow to explain them in terms of stronger nonuniformities in polysilicon inversion when temperature decreases. In particular, the reduction of temperature makes the string currentmore controlledby the polysilicon grain boundaries, increasing, in turn, the amplitude of the RTN fluctuations arising from traps placed on or close to them.

A New Visual Associated Analysis Framework and Design Method for Statistical Data

According to the analysis to the characteristics of socio-economic data, referring to the information expressing method in Geographic Information System (GIS), this paper designs a visualization analysis system to the socio-economic data with attribute, graphics and charts associated style based on Flash technology. According to the requirement, administrative unit spatial graphics database, socio-economic database is designed and the chart component library and model library are constructed. Analysis result shows that the system can improve the efficiency in socio-economic and other relevant data analysis.

Decentralized stand-alone Multi Effect Desalination (MED) system using fixed focus type Scheffler concentrator for the remote and arid rural regions of Sultanate of Oman

Rising population and industrialization made desalination of prime importance in physically water scarce Sultanate of Oman for fulfilling the gap between the rising demand and supply of fresh water. Almost 80-85% of the installed and planned desalination plants in the Sultanate are based on Combined Cycle Gas Turbine (CCGT) power plants while remaining are standalone which includes about 5-7% of the installed plants for rural arid and dry regions. All the installed and planned desalination plants utilises fossil fuels for their operation and are based on Reverse Osmosis (almost 90-95% of the plants) and Multi Stage Flash technologies. Sultanate of Oman is a tropical country with most of the regions being arid and dry receiving solar energy most abundantly. But the utilisation of solar energy in the country is mostly limited to installations based on photovoltaic systems. Only recently solar thermal Enhanced Oil Recovery plant with 1 GWth power output has been undertaken in the country at Amal oil field. A pilot standalone Multi Effect Desalination (MED) plant using fixed focus type Scheffler concentrator for remote and arid rural regions of country has been discussed in this paper to address this gap. This pilot plant has been designed for producing 100 kg/day output based on three stage cross flow type multi effect desalination technology with two 16 m2 Scheffler concentrators and operates in the temperature limits of 170 – 90°C. Preliminary testing carried out on the system during summer and winter period has shown that with available insolation above 700 W/m2, steam at a pressure of 8 to 8.5 bar could be generated in a batch experiment after 2-3 hours from starting the operation for 42 to 55 kg of water in the header of the system. This steam generated is further utilised for desalination in three stages. The initial lag period for the system is measured to be 35-50 minutes depending on the quantity of water in the header, wind speed and solar insolation. System comes out of the lag period when solar insolation reaches just above 650-700 W/m2. The desalination output for the system is measured between 60-65 litres per day for the summer period. Batch type intermittent operation, tracking errors, optical concentration losses, receiver convection losses, brine heat losses are few of the reasons observed based on the analysis for the lower output from the system. Experimentation has given a direction to make operation of the system from batch to continuous production while reducing optical and convection losses through appropriate rectifications for increasing overall yield of the system.

ReveNAND

The paradigm shift from planar (two dimensional (2D)) to vertical (three-dimensional (3D)) models has placed the NAND flash technology on the verge of a design evolution that can handle the demands of next-generation storage applications. However, it also introduces challenges that may obstruct the realization of such 3D NAND flash. Specifically, we observed that the fast threshold drift (fast-drift) in a charge-trap flash-based 3D NAND cell can make it lose a critical fraction of the stored charge relatively soon after programming and generate errors. In this work, we first present an elastic read reference ( V Ref ) scheme (ERR) for reducing such errors in ReveNAND—our fast-drift aware 3D NAND design. To address the inherent limitation of the adaptive V Ref , we introduce a new intra-block page organization (hitch-hike) that can enable stronger error correction for the error-prone pages. In addition, we propose a novel reinforcement-learning-based smart data refill scheme (iRefill) to counter the impact of fast-drift with minimum performance and hardware overhead. Finally, we present the first analytic model to characterize fast-drift and evaluate its system-level impact. Our results show that, compared to conventional 3D NAND design, our ReveNAND can reduce fast-drift errors by 87%, on average, and can lower the ECC latency and energy overheads by 13× and 10×, respectively.

Multimedia Teaching Platform Construction Based on Flash Interaction Technology for Gymnastics

The rapid development of mobile multimedia technology provides broader space for improvement of distance teaching system. It is very difficult for the previous multimedia technology to meet people’s requirements for informatization and intelligentization of multimedia teaching. The appearance of Flash technology offers the new thought for multimedia teaching. Flash not just supports image, voice and video, but also owns thorough object-oriented program design and can achieve interaction among multimedia of different types. In this paper, based on functional framework and distance question answering sub-system, multimedia teaching platform for Gymnastics based on Flash was constructed. Besides, the course Gymnastics was taken for example to carry out effect test, in the hope of offering data support for improvement and promotion of multimedia teaching platform and exploiting future potential development direction of network teaching.

A Quantitative Approach to Characterize Total Ionizing Dose Effect of Periphery Device for 65 nm Flash Memory

To evaluate the total ionizing dose (TID) response of periphery devices with 65 nm flash memory, the TID effects of the main and parasitic transistor have been investigated based on the proposed novel parameter extraction approach. By analyzing post-radiation behavior of the device's drain current and interface trap density, it has been proven that the parasitic transistor demonstrates stronger radiation dependence than the main transistor. With the proposed approach, the roles of the parasitic transistor and main transistor in the TID effect are quantitatively characterized. For a W =10 μm HVN device, the main transistor Vth shows a shift of <0.1 V with a TID of 100 krad (Si), while the parasitic transistor shows shift >0.5 V with 100 krad (Si) radiation. It is concluded that the net positive charge accumulating in the shallow trench isolation oxide is responsible for the TID induced leakage and the Vth shift in the flash technology periphery device.

An Analysis of Flash Page Reuse With WOM Codes

Flash memory is prevalent in modern servers and devices. Coupled with the scaling down of flash technology, the popularity of flash memory motivates the search for methods to increase flash reliability and lifetime. Erasures are the dominant cause of flash cell wear, but reducing them is challenging because flash is a write-once medium— memory cells must be erased prior to writing. An approach that has recently received considerable attention relies on write-once memory (WOM) codes, designed to accommodate additional writes on write-once media. However, the techniques proposed for reusing flash pages with WOM codes are limited in their scope. Many focus on the coding theory alone, whereas others suggest FTL designs that are application specific, or not applicable due to their complexity, overheads, or specific constraints of multilevel cell (MLC) flash. This work is the first that addresses all aspects of page reuse within an end-to-end analysis of a general-purpose FTL on MLC flash. We use a hardware evaluation setup to directly measure the short- and long-term effects of page reuse on SSD durability and energy consumption, and show that FTL design must explicitly take them into account. We then provide a detailed analytical model for deriving the optimal garbage collection policy for such FTL designs, and for predicting the benefit from reuse on realistic hardware and workload characteristics.

Research on Distributed File System Framework Based on Solid State Drive

As the computing power of high performance computing (HPC) systems is developing to exascale, and Big data application tends to be I/O intensive, the storage system is facing high I / O traffic. The poor performance of disk has gradually become the bottleneck of storage system. In recent years, Flash technology has developed rapidly, Flash-based Solid State Drive (SSD) has been widely used in HPC, adding SSD into the storage system can improve the performance of the storage system. In this paper, we designed DSFS, a user-level distributed file system based on SSD. DSFS uses SSD as the underlying storage medium, and adopts Infiniband RDMA (Remote Direct Memory Access) transmission mechanism. The test result shows that DSFS improves the performance of HPC storage system effectively.

FLASH Technology: Full-Scale Hospital Waste Water Treatments Adopted in Aceh

A Hospital waste water contains a complex mixture of hazardous chemicals and harmful microbes, which can pose a threat to the environment and public health. Some efforts have been carried out in Nangroe Aceh Darussalam (Aceh), Indonesia with the objective of treating hospital waste water effluents on-site before its discharge. Flash technology uses physical and biological pre-treatment, followed by advanced oxidation process based on catalytic ozonation and followed by GAC and PAC filtration. Flash Full-Scale Hospital waste water Treatments in Aceh from different district have been adopted and investigated. Referring to the removal efficiency of macro-pollutants, the collected data demonstrate good removal efficiency of macro-pollutants using Flash technologies. In general, Flash technologies could be considered a solution to the problem of managing hospital waste water.

Analysis of combustion residue of the typical plastic carrier and accelerant by flash gas chromatography-mass spectrometry

A method of fire evidence identification applicable to combustion residue was developed by analyzing the combustion residue of a common plastic carrier and accelerant in a fire field. The method could detect the presence of the accelerant in a fire field, thereby preventing missed identification. The appropriate flash temperature was determined by thermal analysis. The combustion residue of the plastic carrier and accelerant was analyzed by flash technology under the appropriate flash temperature. The application of flash technology was evaluated in terms of a range of different experimental conditions, alongside feasibility and qualitative assessments. We found that the optimum flash evaporation temperature was 300℃ when analyzing the combustion residue corresponding to polyethylene (PE) and polyethylene terephthalate (PET) carrier. Experimental results showed that flash gas chromatography-mass spectrometry (Flash GC-MS) extracted the characteristic residual components of the accelerant and could be used to distinguish whether an accelerant was present in a fire or not. The application of flash evaporation technology to fire evidence identification provides a more complete and accurate analysis of the components of combustion residue, eliminating interference factors. Flash GC-MS enriches the modern fire evidence identification toolkit and can support current methods, leading to more accurate and reliable identification.

$${ SIM}^2{ RRAM}$$ S I M 2 R R A M : a physical model for RRAM devices simulation

In the last few years, resistive random access memory (RRAM) has been proposed as one of the most promising candidates to overcome the current Flash technology in the market of non-volatile memories. These devices have the ability to change their resistance state in a reversible and controlled way applying an external voltage. In this way, the resulting high- and low-resistance states allow the electrical representation of the binary states “0” and “1” without storing charge. Many physical models have been developed with the aim of understanding the mechanisms that control the resistive switching. In this work, we have compiled the main theories accepted as well as their corresponding models for the conduction characteristics. In addition, simulation tools play a very important role in the task of checking these theories and understanding these mechanisms. For this reason, the simulation tool called $$\hbox {SIM}^{2}\hbox {RRAM}$$ has been presented. This simulator is capable of replicating the global behavior of RRAM cell based on $$\hbox {HfO}_{x}$$ .

Potential performance of environmental friendly application of ORC and Flash technology in geothermal power plants

The successful exploitation of geothermal energy for power production relies on to the availability of nearly zero emission and efficient technologies, able to provide flexible operation. It can be realized with the binary cycle technology. It consists of a closed power cycle coupled to a closed geothermal loop, whereby the closed power cycle is generally accomplished by means of an organic Rankine cycle (in a few cases the Kalina cycle has been adopted). The confinement of the geothermal fluid in a closed loop is an important advantage from the environmental point of view: possible pollutants contained in the geothermal fluid are not released into the ambient and are directly reinjected underground.Although a well-established technology in the frame of geothermal applications, the adoption of the binary cycle technology is at the moment typically confined to the exploitation of medium-low temperature liquid geothermal reservoirs, generally between 100-170 °C. The important advantages of the binary cycle technology from the environmental point of view suggest nevertheless that it is worthwhile to investigate whether the application range could be extended to higher temperature reservoirs, and up to which extent. Moreover, the paper investigates the effect of an increasing CO2 content in the geothermal fluid. The paper compares in a convenient high temperature range of the geothermal source the performance of a properly optimized geothermal ORC plant, with the performance of a modified flash plant, whereby the geothermal steam enters a turbine, and the CO2 stream is separated, compressed and finally reinjected. An environmentally friendly working fluid, recently introduced in the market, is considered in the ORC optimization process. The performance comparison will involve the assessment of plant net power. As far as the calculations are concerned, the geothermal fluid is assumed to be a mixture of water and possibly CO2. The auxiliary power consumption is properly accounted for: beyond cooling auxiliaries, a submersible well pump for the ORC plant and a gas compressor for the reinjection of the non-condensable gases in the flash plant are considered.

Reviewing the Evolution of the NAND Flash Technology

This paper reviews the recent historical trends of the NAND Flash technology, highlighting the evolution of its main parameters and explaining what allowed it to become not only the most important integrated solution for nonvolatile storage of high volumes of data but also a strong rival eroding the market share of hard-disk drives. The scaling trend followed by planar arrays will be discussed with close attention, along with the major physical constraints impacting the performance and the reliability of modern deca-nanometer technologies. This will make clear why the development of further planar nodes with feature size below ~15 nm, representing today's state of the art, can be considered less favorable than turning all the efforts toward the integration of 3-D arrays. The most promising 3-D architectures will then be reviewed, discussing their benefits and issues and addressing the impact of the change of the integration paradigm from the standpoint of the major NAND applications.

Architectural and Integration Options for 3D NAND Flash Memories

Nowadays, NAND Flash technology is everywhere, since it is the core of the code and data storage in mobile and embedded applications; moreover, its market share is exploding with Solid-State-Drives (SSDs), which are replacing Hard Disk Drives (HDDs) in consumer and enterprise scenarios. To keep the evolutionary pace of the technology, NAND Flash must scale aggressively in terms of bit cost. When approaching ultra-scaled technologies, planar NAND is hitting a wall: both academia researchers and industry worked to cope with this issue for several decades. Then, the 3D integration approach turned out to be the definitive alternative by eventually reaching mass production. This review paper exposes several 3D NAND Flash memory technologies, along with their related integration challenges, by showing their different layouts, scaling trends and performance/reliability features.

Volume Resistive Switching in metallic perovskite oxides driven by the Metal-Insulator Transition

In recent years Resistive Random Access Memory (RRAM) is emerging as the most promising candidate to substitute the present Flash Technology in the non-volatile memory market. RRAM are based on the Resistive Switching (RS) effect, where a change in the resistance of the material can be reversibly induced upon the application of an electric field. In this sense, strongly correlated complex oxides present unique intrinsic properties and extreme sensitivity to external perturbations, which make them suitable for the nanoelectronics of the future. In particular, metallic complex oxides displaying metal-insulator transition (MIT) are very attractive materials for applications and are barely explored as RS active elements. In this work, we analyze the RS behavior of different films belonging to three different families of metallic perovskites: La0.8Sr0.2MnO3, YBa2Cu3O7-δ and NdNiO3. We demonstrate that these mixed electronic-ionic conductors undergo a metal-insulator transition upon the application of an electric field, being able to transform the bulk volume. This volume RS is different in nature from interfacial or filamentary type and opens new possibilities of robust device design. As an example, we present a proof-of-principle result from a 3-Terminal configuration with multilevel memory states.

Exploiting Data Longevity for Enhancing the Lifetime of Flash-based Storage Class Memory

Storage-class memory (SCM) combines the benefits of a solid-state memory, such as high-performance and robustness, with the archival capabilities and low cost of conventional hard-disk magnetic storage. Among candidate solid-state nonvolatile memory technologies that could potentially be used to construct SCM, flash memory is a well-established technology and have been widely used in commercially available SCM incarnations. Flash-based SCM enables much better tradeoffs between performance, space and power than disk-based systems. However, write endurance is a significant challenge for a flash-based SCM (each act of writing a bit may slightly damage a cell, so one flash cell can be written 10^4-10^5 times, depending on the flash technology, before it becomes unusable). This is a well-documented problem and has received a lot of attention by manufactures that are using some combination of write reduction and wear-leveling techniques for achieving longer lifetime. In an effort to improve flash lifetime, first, by quantifying data longevity in an SCM, we show that a majority of the data stored in a solid-state SCM do not require long retention times provided by flash memory (i.e., up to 10 years in modern devices); second, by exploiting retention time relaxation, we propose a novel mechanism, called Dense-SLC (D-SLC), which enables us perform multiple writes into a cell during each erase cycle for lifetime extension; and finally, we discuss the required changes in the flash management software (FTL) in order to use D-SLC mechanism for extending the lifetime of the solid-state part of an SCM. Using an extensive simulation-based analysis of an SLC flash-based SCM, we demonstrate that D-SLC is able to significantly improve device lifetime (between 5.1X and 8.6X) with no performance overhead and also very small changes at the FTL software.

Physically-based evaluation of aging contributions in HC/FN-programmed 40 nm NOR Flash technology

In this paper, an in-depth aging assessment for 40nm NOR Flash cells, programmed by Hot Carrier (HC) and erased by Fowler-Nordheim (FN) mechanisms, is performed during Program/Erase (P/E) cycling. Firstly, the difficulty of properly analyzing the overall HC+FN wear out and the importance of evaluating the different cell characteristic drifts are pointed out. Thus, in order to thoroughly explore the cell degradation, ad-hoc experimental setup and test structures are considered. In particular, using customizable gate patterns during P/E operations, the cell endurance is successfully reproduced on equivalent Flash transistors. Taking advantage of these results and of cell dynamics computation within P/E phases, a fine extraction and separation of electrostatic and cell performance decays within the Programming Window (PW) evolution is presented. Then, using this technique, an accurate physical assessment of cell aging characteristic evolutions under different gate ramp patterns is provided. This attitude is shown to give important guidelines for the optimization of Flash cell endurance performance for a certain initial PW. In particular, the erase pattern is demonstrated not to significantly influence the PW drift, whereas, lowering the ramp speed during the program operation, an important increase of Vth in both states is observed and physically explained.

Analysis of 3D NAND technologies and comparison between charge-trap-based and floating-gate-based flash devices

NAND flash chips have been innovated from two-dimension (2D) design which is based on planar NAND cells to three-dimension (3D) design which is based on vertical NAND cells. Two types of NAND flash technologies–charge-trap (CT) and floating-gate (FG) are presented in this paper to introduce NAND flash designs in detail. The physical characteristics of CT-based and FG-based 3D NAND flashes are analyzed. Moreover, the advantages and disadvantages of these two technologies in architecture, manufacture, interference and reliability are studied and compared.

A low-voltage sense amplifier with two-stage operational amplifier clamping for flash memory**Project supported by the National Natural Science Fundation of China (No. 61376028).

A low-voltage sense amplifier with reference current generator utilizing two-stage operational amplifier clamp structure for flash memory is presented in this paper, capable of operating with minimum supply voltage at 1 V. A new reference current generation circuit composed of a reference cell and a two-stage operational amplifier clamping the drain pole of the reference cell is used to generate the reference current, which avoids the threshold limitation caused by current mirror transistor in the traditional sense amplifier. A novel reference voltage generation circuit using dummy bit-line structure without pull-down current is also adopted, which not only improves the sense window enhancing read precision but also saves power consumption. The sense amplifier was implemented in a flash realized in 90 nm flash technology. Experimental results show the access time is 14.7 ns with power supply of 1.2 V and slow corner at 125 °C.