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Threshold Voltage Fluctuation of the Scaling-down NOR Flash Cells
안호중,송윤흡 대한전자공학회 2010 대한전자공학회 학술대회 Vol.2010 No.6
The random telegraph signal (RTS) for the NOR flash cell scaling is investigated. An innovative ethod to suppress the RTS, based on the device engineering, is proposed. By optimizing the channel doping profile, it is confirmed from three-dimensional (3-D) simulation, that the Vth amplitude, due to RTS, is significantly suppressed. From this result, it is expected that the proposed method to suppress the RTS amplitude is essential for further cell size scaling in Flash memory.
양형준,송윤흡 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.5
The three-dimensional (3-D) NAND flash structure with fully charge storage using edge fringing field effect is presented, and its programming characteristic is evaluated. We successfully confirmed that this structure using fringing field effect provides good program characteristics showing sufficient threshold voltage (VT) margin by technology computer-aided design (TCAD) simulation. From the simulation results, we expect that program speed characteristics of proposed structure have competitive compared to other 3D NAND flash structure. Moreover, it is estimated that this structural feature using edge fringing field effect gives better design scalability compared to the conventional 3D NAND flash structures by scaling of the hole size for the vertical channel. As a result, the proposed structure is one of the candidates of Terabit 3D vertical NAND flash cell with lower bit cost and design scalability.
이정민,송윤흡,Yuta Saito,Yuji Sutou,Junichi Koike 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.9
A selective switching device utilizing a phase-change material was investigated. In this work, we present a new concept to realize serially a selective switching and memory operation in a multiple phase-change memory with only phase-change materials without any semiconductor switching device. A phase-change material for selective switching can be expected to have a higher resistance amorphous phase and to show lower melting and crystallization temperatures than a phase-change material for a memory. Here, we present a structural method to obtain the above requirements. In addition, we confirm the switching operation by a selective current pulse for multiple phase-change materials from the experiment. From these results, we expected that one of the multiple phasechange materials can be replaced in a switching device without the need for an additional selective device, and that such a device would be feasible for 3-dimensional PCM architecture.
이정민,송윤흡 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.6
The reliability of a magnetic tunnel junction (MTJ) with an MgO tunnel barrier was evaluated. In particular, various voltage tests were used to investigate the effects of the barrier thickness andthe temperature on the resistance drift. We compared the resistance change during a constantvoltage stress (CVS) test and confirmed a trap/detrap phenomenon during the interval stress fordifferent barrier thicknesses and temperatures. The resistance drift representing degradation andthe time to breakdown (TBD) representing the breakdown characteristic were better for a thickerbarrier and lower temperature, but were worse for a thinner barrier and a higher temperature. Theresults suggest that breakdown and degradation due to trap generation strongly depend on boththe barrier thickness and the temperature. Furthermore, as the TBD varies at steady rates withchanging barrier thickness, temperature, and electric field, we assume that a MTJ with an adnormalthin layer of MgO can be screened effectively based on the predicted TBD. As a result, the barrierthickness and the temperature are very important in determining the reliability of a MTJ, and thisstudy is expected to be helpful in understanding the degradation and the breakdown of a MTJ.
김규범,오영택,송윤흡 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.12
In this work, we present the results of an investigation of the impact of the stress on a poly-silicon channel induced by the neighboring layers in three-dimensional vertical NAND (3D V-NAND) flash memories. Using 3D process simulations, we confirmed the distributions of the residual stress after each process step in the cross-section of a NAND flash unit cell. To investigate the impact of the stress on the poly-silicon channel, we also studied the residual stress after changing the intrinsic stresses of the oxide-nitride-oxide (ONO) layer and the tungsten layer used as a gate. We found that the amplitude of the residual stress in the applied layer became larger as the intrinsic stress increased. In addition, the intrinsic tensile/compressive stresses in the outer layers affected the residual stresses of the previously deposited layers in an opposite nature of the stresses. The cylindrical poly-silicon channel was influenced by the intrinsic stresses of the oxide layers adjacent to the nitride and the tungsten films, with the intrinsic stress of the tunnel oxide having the greater effect on the residual stress in the channel. Because such stresses affect the electrical properties of the devices, optimized deposition conditions are required to control them. Such conditions would aid in improving the performances of 3D NAND flash memories.
노일표,김상현,송윤흡,송진동 한국물리학회 2017 Current Applied Physics Vol.17 No.3
We designed and fabricated an Al0.9Ga0.1Sb/In0.4Ga0.6Sb/Al0.9Ga0.1Sb quantum well (QW) with a balanced band offset for channel materials in future complementary metal-oxide-semiconductor (CMOS) circuits. The QW design was carried out by one-dimensional SchrodingerePoisson equation system. The QW was grown by molecular beam epitaxy and the crystallinity and the surface morphology were characterized using a transmission electron microscope (TEM) and atomic force microscope (AFM), respectively. The results showed good crystalline behaviors and morphologies without any identifiable morphological defects. Furthermore, we investigated the strain characteristics in In0.4Ga0.6Sb by measuring the Raman shift. We found that In0.4Ga0.6Sb has high compressive strain of 1.74% and the strain distribution was uniform.
이정민,길규현,이개훈,최철민,송윤흡,Hiroaki Sukegawa,Seiji Mitani 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.8
The reliability of a magnetic tunnel junction (MTJ) based on a Co2FeAl (CFA) full-Heusler alloywith a MgO tunnel barrier was evaluated. In particular, the effect of a Mg insertion layer underthe MgO was investigated in view of resistance drift by using various voltage stress tests. Wecompared the resistance change during constant voltage stress (CVS) and confirmed a trap/detrapphenomenon during the interval stress test for samples with and without a Mg insertion layer. TheMTJ with a Mg insertion layer showed a relatively small resistance change for the CVS test anda reduced trap/detrap phenomenon for the interval stress test compared to the sample without aMg insertion layer. This is understood to be caused by the improved crystallinity at the bottomof the CFA/MgO interface due to the Mg insertion layer, which provides a smaller number of trapsite during the stress test. As a result, the interface condition of the MgO layer is very importantfor the reliability of a MTJ using a full-Heusler alloy, and the the insert of a Mg layer at the MgOinterface is expected to be an effective method for enhancing the reliability of a MTJ.
3차원 낸드 플래시 채널 홀의 Vertical Profile 개선을 위한 에칭 공정 조건 연구
박상우(Sangwoo Park),송윤흡(Yunheub Song) 대한전자공학회 2020 대한전자공학회 학술대회 Vol.2020 No.8
In this paper, in order to establish the conditions in the etching process even in difficult process problems, after depositing the stacked films Oxide―Poly―Oxide (OPO), E―beam lithography was used to draw the desired pattern and experiment on channel hole etching was performed. ICP power, chuck power, pressure, and gas were controlled using equipment to proceed with the process. Through this, the vertical profile was secured under certain conditions and the etch stop was confirmed using SEM, FIB, and TEM as analytical equipment and conditions were established.