• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.66-79
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• 2008

Several oxides have recently been reported to have resistance-switching characteristics for nonvolatile memory (NVM) applications. Both binary and ternary oxides demonstrated great potential as resistive-switching memory elements. However, the switching mechanisms have not yet been clearly understood, and the uniformity and reproducibility of devices have not been sufficient for gigabit-NVM applications. The primary requirements for oxides in memory applications are scalability, fast switching speed, good memory retention, a reasonable resistive window, and constant working voltage. In this paper, we discuss several materials that are resistive-switching elements and also focus on their switching mechanisms. We evaluated non-stoichiometric polycrystalline oxides ($Nb_2O_5$, and $ZrO_x$) and subsequently the resistive switching of $Cu_xO$ and heavily Cu-doped $MoO_x$ film for their compatibility with modem transistor-process cycles. Single-crystalline Nb-doped $SrTiO_3$ (NbSTO) was also investigated, and we found a Pt/single-crystal NbSTO Schottky junction had excellent memory characteristics. Epitaxial NbSTO film was grown on an Si substrate using conducting TiN as a buffer layer to introduce single-crystal NbSTO into the CMOS process and preserve its excellent electrical characteristics.

• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.7-12
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• 2011

The flash memory has been remarked as the next generation media of portable and desktop computers' storage devices. Their features include non-volatility, low power consumption, and fast access time for read operations, which are sufficient to present flash memories as major data storage components for desktop and servers. The purpose of our study is to upgrade a traditional mirroring scheme based on SSD storages due to the relatively slow or freezing characteristics of write operations, as compared to fast read operations. For this work, we propose a new storage management scheme called Memory Mirror-Switching based on traditional mirroring scheme. Our Mirror-Switching scheme improves flash operation performance by switching write-workloads from flash memory to RAM and delaying write operations to avoid freezing. Our test results show that our scheme significantly reduces the write operation delay and storage freezing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.318-318
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• 2012

A graphene layer is most important materials in resent year to enhance the electrical properties of semiconductor device due to high mobility, flexibility, strong mechanical resistance and transparency[1,2]. The resistance switching memory with the graphene layer have been reported for next generation nonvolatile memory device[3,4]. Also, the graphene layer is able to improve the electrical properties of memory device because of the high mobility and current density. In this study, the resistance switching memory device with metal-oxide nano-particles embedded in polyimide layer on the graphene mono-layer were fabricated. At first, the graphene layer was deposited $SiO_2$/Si substrate by using chemical vapor deposition. Then, a biphenyl-tetracarboxylic dianhydride-phenylene diamine poly-amic-acid was spin coated on the deposited metal layer on the graphene mono-layer. Then the samples were cured at $400^{\circ}C$ for 1 hour in $N_2$ atmosphere after drying at $135^{\circ}C$ for 30 min through rapid thermal annealing. The deposition of aluminum layer with thickness of 200 nm was done by a thermal evaporator. The electrical properties of device were measured at room temperature using an HP4156a precision semiconductor parameter analyzer and an Agilent 81101A pulse generator. We will discuss the switching mechanism of memory device with metal-oxide nano-particles on the graphene mono-layer.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.113-118
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• 1986

Nowdays switching software designs are based on the concept of maximizing efficiency. This idea is to put through the most call, in the fastest time, using the fewest possible resources. So the memory usages are embossed one of the most important part to be considered in the switching software. This paper discusses the general concepts of switching software at first, then describes the switching data base from the view point of the access time, memory efficiency, and call processing environment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.234-237
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• 1996

The amorphous chalogenide semiconductors are new material in semiconductor physics. Their properties, especially electronic and optical properties are main motives for device application. Amorphous As$_{10}$Ge$_{15}$ Te$_{75}$material has the stable ac conductivity at high frequency and the dc memory switching property. At higher frequency than 10MHz, ac conductivity of As$_{10}$Ge$_{15}$ Te$_{75}$ thin film is much higher than below frequency and independent of temperature and frequency. If the dc voltages are applied between edges of thin film, one can see the dc memory switching phenomenon, in other words the dc conductivity increases quite a few of magnitude after the threshold voltage is applied. Using the stable ac conductivity at high frequency and the increase of conductivity after dc memory switching, As$_{10}$Ge$_{15}$ Te$_{75}$thin film is considered as new material for microwave switch devices.vices.es.vices.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.28.2-28.2
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• 2011

Resistance random access memory (ReRAM) is a promising candidate for next-generation nonvolatile memory because of its advantageous qualities such as simple structure, superior scalability, fast switching speed, low-power operation, and nondestructive readout. We investigated the resistive switching behavior of tantalum oxide that has been widely used in dynamic random access memories (DRAM) in the present semiconductor industry. As a result, it possesses full compatibility with the entrenched complementary metal-oxide-semiconductor processes. According to previous studies, TiN is a good oxygen reservoir. The TiN top electrode possesses the specific properties to control and modulate oxygen ion reproductively, which results in excellent resistive switching characteristics. This study presents fully room temperature fabricated the TiN/$TaO_x$/Pt devices and their electrical properties for nonvolatile memory application. In addition, we investigated the TiN electrode dependence of the electrical properties in $TaO_x$ memory devices. The devices exhibited a low operation voltage of 0.6 V as well as good endurance up to $10^5$ cycles. Moreover, the benefits of high devise yield multilevel storage possibility make them promising in the next generation nonvolatile memory applications.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.147-152
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• 2016

In this study, we fabricated Ag-based electrochemical metallization memory devices which is also called conductive-bridge random-access memory (CBRAM) in order to investigate the resistive switching behavior depending on the bottom electrode (BE). RRAM cells of two different layer configurations having $Ag/Si_3N_4/TiN$ and $Ag/Si_3N_4/p^+$ Si are studied for metal-insulator-metal (MIM) and metal-insulator-silicon (MIS) structures, respectively. Switching voltages including forming/set/reset are lower for MIM than for MIS structure. It is found that the workfunction different affects the performances.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.368.1-368.1
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• 2014

We proposed amorphous GeSe-based ReRAM device of metal-insulator-metal (M-I-M) structure. The operation characteristics of memory device occured unipolar switching characteristics. By introducing the concepts of valance-alternation-pairs (VAPs) and chalcogen vacancies, the unipolar resistive switching operation had been explained. In addition, the current transport behavior were analyzed with space charge effect of VAPs, Schottky emission in metal/GeSe interface and P-F emission by GeSe bulk trap in mind. The GeSe ReRAM device of M-I-M structure indicated the stable memory switching characteristics. Furthermore, excellent stability, endurance and retention characteristics were also verified.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.7
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• pp.400-403
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• 2016

The resistive memory switching characteristics of resistive random access memory (ReRAM) using the amorphous GeSe thin film have been demonstrated at Al/Ti/GeSe/$n^+$ poly Si structure. This ReRAM indicated bipolar resistive memory switching characteristics. The generation and the recombination of chalcogen cations and anions were suitable to explain the bipolar switching operation. Space charge limited current (SCLC) model and Poole-Frenkel emission is applied to explain the formation of conductive filament in the amorphous GeSe thin film. The results showed characteristics of stable switching and excellent reliability. Through the annealing condition of $400^{\circ}C$, the possibility of low temperature process was established. Very low operation current level (set current: ~ ${\mu}A$, reset current: ~ nA) was showed the possibility of low power consumption. Particularly, $n^+$ poly Si based GeSe ReRAM could be applied directly to thin film transistor (TFT).

• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.2
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• pp.10-16
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• 1977

Memory switching of the amorphous chalcogenide Ge-Te-Si memory devices were observed at various thicknesses and temperatures. For a given thickness, the distribution of threshold voltages shows a strong peaks, which is attributed to the intrinsic switching mechanism. The plot of Vth versus thickness indicates that threshold voltages were lowered and switching fields were raised as thickness was decreased. And threshold voltage sagged as temperature was raised and the fact that threshold voltage can be lowered at the temperature range under Tg was obtained.