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In this paper, we report a novel Cr/TaOx/Al (top to bottom) Resistive Random Access Memory (RRAM) which works as a bipolar switching device. The RRAM devices have demonstrated excellent memory performance including small magnitude of switching voltages (about 2 V), a tight distribution of Vset and Vreset, low switching current, large off/on resistance ratio R of up to 107, and good retention characteristics...
Crystallization properties of the phase change materials GeSbxTe and GexSb2Te were studied. For GeSbxTe we found that for large x = 6 the crystallization was very fast but crystallization temperature was low while for small x = 1 crystallization was slow but crystallization temperature was high. An alloy with a good compromise between crystallization time and temperature can be found at x = 4.6, with...
A phase-change random access memory device, consisting of GeSb9 based chalcogenide, TiW electrode and SiO2 dielectric layer, was fabricated in order to investigate the electrical characteristic and failure mechanism. Amorphous Si-doped GeSb9 with high crystallization temperature (235°C) exhibits extremely good thermal stability. Ten year data retention of 164°C shows the remarkable device reliability...
The thermal conductivity of nitrogen-doped Ge2Sb2Te5 (N-GST) was analyzed using Frequency Domain Thermoreflectance (FDTR). The thermal conductivity of amorphous N-GST (∼0.15 W/m-K) was not found to change significantly as the nitrogen concentration was raised from 0 at% to ∼6 at%, possibly due to the huge amount of phonon scattering in the disordered films. The thermal conductivity of crystalline...
Glassy alloys with composition of Ge20ZnxTe80-x (x=0, 5, 10, 15at%) were prepared by conventional melt-quenching method, which were subsequently used as target for thermal evaporation (TE) technique under vacuum. The Ge-Te-Zn chalcogenide thin films were characterized with XRD and Transmittance spectra. XRD measurements indicate that there is an amorphous-to-crystalline phase transition. The GeTe...
A novel read-while-write (RWW) algorithm for phase change memory (PCM) is proposed. It performs the verify operation for last cell, the write operation for current cell and the pre-read operation for next cell simultaneously. Therefore, it can reduce the timing cost by the data-comparison write (DCW) algorithm and the program & verify (P&V) algorithm. The performance analysis and simulation...
In this paper, a 128Mb phase change random access memory based on phase change Ge2Sb2Te5 alloy has been designed in 40nm 4 metal level CMOS technology. Memory cell is the dual trench epitaxial pn junction diode. According to the feature of the 1D1R memory cell structure, array architecture and chip architecture have been optimized. The read access time is 30ns in simulation. The layout area is 6.6mm...
Films of crystalline and amorphous Fe12(Ge2Sb2Te5)88 were prepared using laser synthesis from a stoichiometric target. The crystalline film, prepared at 300 °C was found to be in the hexagonal close packed (HCP) structure while the film prepared at room temperature was found to be amorphous. The crystalline film showed clear magnetic hysteresis, while the amorphous and the 220 °C prepared film exhibited...
Switchable metal-insulator-metal (MIM) structures are the key elements for future non-volatile resistive RAM (RRAM) devices. Recently this type of memory device has attracted considerable interest due to the prospect of non-volatile data storage combined with low power consumption, excellent scalability and very fast write/read operation. However the physical processes responsible for the fast resistive...
In this paper, we proposed an additional post-deposition annealing PDA processes by inserting a pre-treatment before high temperature annealing in N2 ambience, which has been demonstrated to efficiently optimize the performance of Metal/Al2O3/Si3N4/SiO2/Si (MANOS) devices. By using low-energy plasma oxygenic ions bombardment to the surface of ONA stack, the retention and erase speed obtain a better...
This paper describes chemical vapor deposition (CVD) of GeSbTe (GST) film for fabricating phase change memory, especially for the back end of line memory application. We successfully controlled the film composition including stoichiometric Ge2Sb2Te5 by changing deposition conditions. The deposited films had a significantly smooth surface and it was possible to fill a high aspect hole. The mechanism...
A novel phase-change memory cell with a heating layer structure (HLS) was proposed in this work. By having an additional Titanium Nitride (TiN) layer under the bottom electrode, the heat loss can be effectively prevented. A three-dimensional finite element model for phase change memory (PCM) is established to simulate thermal and electrical behaviors. Compared with the traditional structure (TS) PCM...
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