Thermal stability and data retention of resistive random access memory with HfOx/ZnO double layers

As an industry accepted storage scheme, hafnium oxide（HfO_x） based resistive random access memory（RRAM）should further improve its thermal stability and data retention for practical applications. We therefore fabricated RRAMs with HfO_x/ZnO double-layer as the storage medium to study their thermal stability as well as data retention. The HfO_x/ZnO double-layer is capable of reversible bipolar switching under ultralow switching current（〈 3 μA） with a Schottky emission dominant conduction for the high resistance state and a Poole–Frenkel emission governed conduction for the low resistance state. Compared with a drastically increased switching current at 120℃ for the single HfO_x layer RRAM, the HfO_x/ZnO double-layer exhibits excellent thermal stability and maintains neglectful fluctuations in switching current at high temperatures（up to 180℃）, which might be attributed to the increased Schottky barrier height to suppress current at high temperatures. Additionally, the HfO_x/ZnO double-layer exhibits 10-year data retention @85℃ that is helpful for the practical applications in RRAMs.

An effective approach to improve split-gate flash product data retention

Data retention is one of the most important reliability characteristics of split-gate flash.Therefore,many efforts were made to improve data retention of split-gate flash.By experiments,it was found that higher chlorine concentration produced in FGSP2 oxide deposition can induce worse data retention.Thus,reducing chlorine concentration is an effective approach to improve data retention for split-gate flash product.Additional RTO annealing between FGSP2 oxide deposition and FGSP2 etching could reduce chlorine concentration,and improve FGSP2 oxide film quality,and then get better data retention.

Reliability evaluation on sense-switch p-channel flash

In this paper,the reliability of sense-switch p-channel flash is evaluated extensively.The endurance result indicates that the p-channel flash could be programmed and erased for more than 10000 cycles;the room temperature read stress shows negligible influence on the p-channel flash cell;high temperature data retention at 150℃ is extrapolated to be about 5 years and 53 years corresponding to 30% and 40% degradation in the drive current,respectively.Moreover,the electrical parameters of the p-channel flash at different operation temperature are found to be less affected.All the results above indicate that the sense-switch p-channel flash is suitable to be used as the configuration cell in flash-based FPGA.

Integration of high-performance spin-orbit torque MRAM devices by 200-mm-wafer manufacturing platform

We demonstrate in-plane field-free-switching spin-orbit torque(SOT)magnetic tunnel junction(MTJ)devices that are capable of low switching current density,fast speed,high reliability,and,most importantly,manufactured uniformly by the 200-mm-wafer platform.The performance of the devices is systematically studied,including their magnetic properties,switch-ing behaviors,endurance and data retention.The successful integration of SOT devices within the 200-mm-wafer manufactur-ing platform provides a feasible way to industrialize SOT MRAMs.It is expected to obtain excellent performance of the devices by further optimizing the MTJ film stacks and the corresponding fabrication processes in the future.

Phase transformation in Mg Sb_3Te thin films

Mg-doped Sb3Te films are proposed to improve the performance of phase-change memory （PCM）. We prepare Mg- doped Sb3Te films and investigate their crystallization behaviors, structural, optical and electrical properties. We find that Mg-doping can increase the crystallization temperature, enhance the activation energy, and improve the 10-year data retention of Sb3Te. Especially Mg25.19（Sb3Te）74.81 shows higher Tc （~ 190℃） and larger Ea （~ 3.49 eV）, which results in a better data retention maintaining for 10 yr at ~ 112 ℃. Moreover Ra/Rc value is also improved. These excellent properties make Mg-Sb-Te material a promising candidate for the phase-change memory （PCM）.

The correlation between molecular structure parameters of O-ethyl N-isopropyl phosphoro(thioureido)thioates and their retention data in RP-HPLC

A retention prediction system(RPS)of seven O-ethyl N-isopropyl phosphoro(thioureido)- thioates in reversed phase HPLC was investigated.The system is based on the solvent selectivity triangle concept.Three molecular structure parameters(hydrophobicity Ⅱ,substituent length L, and substituent maximum width B_5)were used to describe the quantitative structure-retention relation- ships.With these quantitative relationships,the retention behaviours of other eight homologs for different mobile phase composition were predicted.The predicted values were consistent with the measured values within relative error of 10%,which means that it is possible to apply the reported method to predict retention values for qualitative purposes for different mobile phase compositions.

6T SRAM cell analysis for DRV and read stability

The present paper analyzes the hold and read stability with temperature and aspect ratio variations. To reduce the power dissipation, one of the effective techniques is the supply voltage reduction. At this reduced supply voltage the data must be stable. So, the minimum voltage should be discovered which can also retain the data. This voltage is the data retention voltage（DRV）. The DRV for 6T SRAM cell is estimated and analyzed in this paper.The sensitivity analysis is performed for the DRV variation with the variation in the temperature and aspect ratio of the pull up and pull down transistors. Cadence Virtuoso is used for DRV analysis using 45 nm GPDK technology files. After this, the read stability analysis of 6T SRAM cell in terms of SRRV（supply read retention voltage） and WRRV（wordline read retention voltage） is carried out. Read stability in terms of RSNM can be discovered by accessing the internal storage nodes. But in the case of dense SRAM arrays instead of using internal storage nodes,the stability can be discovered by using direct bit line measurements with the help of SRRV and WRRV. SRRV is used to find the minimum supply voltage for which data can be retained during a read operation. Similarly, WRRV is used to find the boosted value of wordline voltage, for which data can be retained during read operation. The SRRV and WRRV values are then analyzed for different Cell Ratios. The results of SRRV and WRRV are then compared with the reported data for the validation of the accuracy of the results.