Papers by Author: You Yin

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Authors: You Yin, Sumio Hosaka
Abstract: In this work, we investigate the effect of the N-doping on microstructure and electrical properties of chalcogenide Ge2Sb2Te5 (GST) films for application to multilevel-storage phase change memory (PCM). Crystal size can be markedly reduced from 16 nm to 5 nm by N-doping into GST. The crystal growth suppression is believed to be controlled by distributed fine nitride particles. The resistivity of N-GST as a function of annealing temperature exhibits a gradual change due to the crystal growth suppression. The characteristics imply that N-GST is suitable for application to multilevel-storage PCM as the next-generation nonvolatile memory.
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Authors: Hui Zhang, Takuro Tamura, You Yin, Sumio Hosaka
Abstract: We have studied on theoretical electron energy deposition in thin resist layer on Si substrate for electron beam lithography. We made Monte Carlo simulation to calculate the energy distribution and to consider formation of nanometer sized pattern regarding electron energy, resist thickness and resist type. The energy distribution in 100 nm-thick resist on Si substrate were calculated for small pattern. The calculations show that 4 nm-wide pattern will be formed when resist thickness is less than 30 nm. Furthermore, a negative resist is more suitable than positive resist by the estimation of a shape of the energy distribution.
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Authors: Takuro Tamura, Yasunari Tanaka, Takashi Akahane, You Yin, Sumio Hosaka
Abstract: In this study, we investigated the possibility of forming the fine Si dot arrays by means of electron beam (EB) lithography and dry etching technique for the future’s devices with nano-scale structures. We examined the properties of Ar ion milling for the fabrication of nanometer sized Si dot arrays on a Si substrate. We have succeeded in forming 40 nm pitched Si dot arrays with a diameter of <20 nm using dot array patterns of the calixarene resist as a mask. We also obtained the Ar ion milling property that there exists the horizontal milling rate as well as the vertical milling rate. We formed Si dot arrays with a dot diameter of about 10 nm using this property. It was clarified that Ar ion milling and EB lithography with calixarene resist has the potential to form Si nano dot arrays for the nano devices.
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Authors: Miftakhul Huda, Takuro Tamura, You Yin, Sumio Hosaka
Abstract: In this work, we studied the fabrication of 12-nm-size nanodot pattern by self-assembly technique using high-etching-selectivity poly (styrene)-poly (dimethyl-siloxane) (PS-PDMS) block copolymers. The necessary etching duration for removing the very thin top PDMS layer is unexpectedly longer when the used molecular weight of PS-PDMS is 13.5-4.0 kg/mol (17.5 kg/mol total molecular weight) than that of 30.0-7.5 kg/mol (37.5 kg/mol total molecular weight). From this experimental result, it was clear that PS-PDMS with lower molecular weight forms thicker PDMS layer on the air/polymer interface of PS-PDMS film after microphase separation process. The 22-nm pitch of nanodot pattern by self-assembly holds the promise for the low-cost and high-throughput fabrication of 1.3 Tbit/inch2 storage device. Nanodot size of 12 nm also further enhances the quantum-dot effect in quantum-dot solar cell.
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Authors: Takashi Akahane, Miftakhul Huda, You Yin, Sumio Hosaka
Abstract: In this paper, we report two kinds of guide patterns precisely created by electron beam drawing. These guide patterns are expected to precisely control the arrangement of nanodots self-assembled from block copolymer (BCP) in order to obtain long-range-order nanofabrication. The first guide pattern is comprised only of a post lattice. The second guide pattern adds guide lines to the post lattice. The added guide lines are expected to better control the location and orientation of the BCP nanodots. We succeeded in fabricating these two kinds of guide patterns for 22-nm- and 33-nm-pitch BCP nanodots.
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Authors: Takashi Akahane, Miftakhul Huda, Takuro Tamura, You Yin, Sumio Hosaka
Abstract: We have studied functionalization of guide pattern with brush treatment. Especially, the effect of brush treatment on ordering of nanodots formed on the guide pattern was investigated. We used polydimethylsiloxane (PDMS) as brush modification to form self-assembled nanodots on the guide pattern using polystyrene (PS) - PDMS as block copolymer. The brush treatment using toluene solvent made guide patterns of the electron beam (EB) drawn resist behave like PDMS guide patterns and good ordering of the nanodots has been achieved. It was demonstrated that the brush treatment enabled the PDMS nanodots to be regularly located in the desired positions defined by the EB drawn guide patterns.
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Authors: You Yin, Sumio Hosaka
Abstract: Performance of lateral phase change memories (LPCMs) is investigated by both electrical characterization and finite element analysis. Ge2Sb2Te5 lateral PCMs (GST-LPCMs) exhibit a low reset current but a bad endurance. By replacing GST with Sb2Te3 (ST) and adding a TiN layer between ST and electrodes, the ST-TiN-LPCMs are demonstrated to have a much improved endurance. Finite element analysis of the LPCMs with electric-thermal structural interaction shows that thermal confinement makes GST-LPCMs low-power consumptive but that high level stress makes them readily broken. In contrast, ST-TiN-LPCMs experience low level stress during operation but high power consumption is required.
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Authors: You Yin, Tomoyuki Noguchi, Hiroki Ohno, Sumio Hosaka
Abstract: Reliability (or stability) of multi-level storage (MLS) is the critical characteristics for multi-level cells. In order to improve reliability of MLS of phase-change memory, there are two effective approaches, (i) enlargement of the ratio between resistance levels and (ii) reduction of scattering of resistance level. On the basis of our experimental results, it is demonstrated that the Ge2Sb2Te5-based double-layered cell has a high ratio of highest to lowest levels up to two-to-three orders of magnitude, implying high reliability. The cells exhibit the possibility of stable switching for four-level storage.
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Authors: Sumio Hosaka, Takayuki Takizawa, Daisuke Terauchi, You Yin, Hayato Sone
Abstract: We have studied a step-in mode non-contact atomic force microscopy (NC-AFM) for precise measurement of fine and steep structure with nanometer resolution in air. When a high aspect structure is measured using step-in mode AFM with the sharpened and slim probe, it is required that AFM control has to be performed at a force of <1 nN in pico-Newton range to suppress the bending and slipping of the probe on slop. Using a home-made step-in mode NC-AFM using a quadrature frequency demodulator for resonant frequency shift of the cantilever, the NC-AFM demonstrated that Si steep structure was faithfully observed at about 2 pN in air.
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Authors: You Yin, Sumio Hosaka
Abstract: Lateral rectangular (R-) and step-like (S-) channel phase-change memory (PCM) cell structures are numerically analyzed for multi-state storage based on their temperature distributions and their programming characteristics. The S-PCM cell is characterized by the sequentially melted sub-channel and step-like programming characteristics. From the viewpoint of the performance for multi-state storage, the step-like characteristics indicate high controllability for its application of multi-state storage.
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