Low-temperature process steps for realization of non-volatile memory devices

In this work, the low-temperature process steps required for the realization of nano-crystal non-volatile memory cells are discussed. An amorphous silicon film, crystallized using a diode pumped solid state green laser irradiating at 532 nm, is proposed as an active layer. The deposition of the subsequent functional layers (e.g., gate oxide) can be done using CVD and ALD reactors in a cluster tool. We show that a high nanocrystal density (Si-NC), required for a good functionality of the memory device, can be obtained by using disilane (Si2H6) or trisilane (Si3H8, known as Silcore®) as precursors for LPCVD instead of silane, at a deposition temperature of 325 °C. The nanocrystals are encapsulated with an ALD-Al2O3 layer (deposited at 300 °C), which serves as oxidation barrier. The passivation of the realized structure is done with an ALD-TiN layer deposited at 425 °C. In this work, we realized Al/TiN/Al2O3/Si-NC/SiO2/Si(100) multilayer floating-gate structures, where the crystallized amorphous silicon film was for the time being replaced by a mono-crystalline silicon wafer, and the gate oxide was thermally grown instead of a low-temperature PECVD oxide. The structures were characterized in terms of their performance as memory cells. In addition, the feasibility to use laser crystallization for improving the amorphous silicon films (prior to the gate oxide deposition) was explored

Drainage System of Tegalsari Polder for Handling Flood and Tide in Tegal City Indonesia

Although in 2019 the local government of Tegal city Indonesia had constructed a retention basin at drainage system of Siwatu, Tegal Barat, Tegal city with a catchment area of 226 ha, the areas around the system still experienced flood and inundation. This study belonged to a descriptive qualitative research aimed to evaluate the performances of Siwatu drainage system and Tegalsari retention basin. Data of the study included field data and technical data from institutions. Based on the 15-year rainfall data (2014 – 2018) from Pemali - Comal PSDA Office, Central Java Province, Indonesia, the statistical parameters of Cs: 0.0027, Ck: 1.904, Sd: 15.91, Cv: 0.144 were obtained and so Gumbel method distribution was applied in the study, the return period rainfall of 10 years was 138 mm, the flood discharge for Qr.10 years was 9.63 m3/sec., the addition of long storage was 8×2,50×500 m, and the combination of pump addition was of 1 m3/sec. with the long storage of 8×2.00×500 m. By implementing one of the alternative choices, either flood or inundation could be resolved

Electrical properties of plasma-deposited silicon oxide clarified by chemical modeling

Our study is focused on Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon dioxide films at low temperatures (< 150 oC) using Inductively Coupled (IC) High-Density (HD) plasma source. We recently fabricated Thin Film Transistors (TFTs) with high-quality ICPECVD gate oxides, which exhibited a competitive performance. For better understanding of the influence of deposition parameters on both the deposition kinetics and oxide quality, we have modeled the Ar-SiH4-N2O plasma system with 173 chemical reactions. We simulated concentrations of 43 reactive species (such as e.g. SiHx radicals and SiHx + (x=0-3) ions, polysilanes, SiO, SiN, SiH3O, SiH2O, HSiO, etc., as well as atomic hydrogen, nitrogen and oxygen) in plasma. We further used our simulations to qualitatively explain (in terms of concentrations of the reactive species) the influence of SiH4/N2O gas-flow ratio and total gas pressure on film electrical properties and deposition rate

Proximity effects in the superconductor / heavy fermion bilayer system Nb / CeCu_6

We have investigated the proximity effect between a superconductor (Nb) and a 'Heavy Fermion' system (CeCu_6) by measuring critical temperatures $T_c$ and parallel critical fields H_{c2}^{\parallel}(T) of Nb films with varying thickness deposited on 75 nm thick films of CeCu_6, and comparing the results with the behavior of similar films deposited on the normal metal Cu. For Nb on CeCu_6 we find a strong decrease of T_c with decreasing Nb thickness and a finite critical thickness of the order of 10 nm. Also, dimensional crossovers in H_{c2}^{\parallel}(T) are completely absent, in strong contrast with Nb/Cu. Analysis of the data by a proximity effect model based on the Takahashi-Tachiki theory shows that the data can be explained by taking into account both the high effective mass (or low electronic diffusion constant), {\it and} the large density of states at the Fermi energy which characterize the Heavy Fermion metal.Comment: 7 pages, 2 figure. Manuscript has been submitted to a refereed journa

Langmuir-probe characterization of an inductively-coupled remote plasma system intended for CVD and ALD

We measured electron density and electron energy distribution function (EEDS) vertically through our reactor for a range of process conditions and for various gases. The EEDF of Ar plasma in the reactor could largely be described by the Maxwell-Boltzmann distribution function, but it also contained a fraction (~10-3) of electrons which were much faster (20-40 eV). At low pressures (6.8-11 µbar), the tail of fast electrons shifted to higher energies (Emax ~50 eV) as we measured more towards the chuck. This tail of fast electrons could be shifted to lower energies (Emax ~30 eV) when we increased pressure to 120 µbar or applied an external magnetic field of 9.5 µT. Addition of small amounts of N2 (1-10%) or N2O (5%) to Ar plasma lowered the total density of slow electrons (approx. by a factor two) but did not change the shape of the fast-electron tail of the EEDF. The ionization degree of Ar-plasma increased from 2.5 104 to 5 104 when an external magnetic field of 9.5 µT was applied

The MUSE-Faint survey. IV. Dissecting Leo T, a gas-rich relic with recent star formation

Leo T ($M_V = -8.0$) is both the faintest and the least massive galaxy known to contain neutral gas and to display signs of recent star formation. We analyse photometry and stellar spectra to identify member stars and to better understand the overall dynamics and stellar content of the galaxy and to compare the properties of its young and old stars. We use data from the Multi Unit Spectroscopic Explorer (MUSE) on the VLT. We supplement this information with spectroscopic data from the literature and with Hubble Space Telescope (HST) photometry. Our analysis reveals two distinct populations of stars in Leo T. The first population, with an age of $\lesssim 500~\mathrm{Myr}$, includes three emission-line Be stars comprising 15% of the total number of young stars. The second population of stars is much older, with ages ranging from $>5~\mathrm{Gyr}$ to as high as $10~\mathrm{Gyr}$. We combine MUSE data with literature data to obtain an overall velocity dispersion of $\sigma_{v} = 7.07^{+1.29}_{-1.12}~\mathrm{km\ s^{-1}}$ for Leo T. When we divide the sample of stars into young and old populations, we find that they have distinct kinematics. Specifically, the young population has a velocity dispersion of $2.31^{+2.68}_{-1.65}\,\mathrm{km\ s^{-1}}$, contrasting with that of the old population, of $8.14^{+1.66}_{-1.38}\,\mathrm{km\ s^{-1}}$. The fact that the kinematics of the cold neutral gas is in good agreement with the kinematics of the young population suggests that the recent star formation in Leo T is linked with the cold neutral gas. We assess the existence of extended emission-line regions and find none to a surface brightness limit of~$< 1\times 10^{-20}\,\mathrm{erg}\,\mathrm{s}^{-1}\,\mathrm{cm}^{-2}~\mathrm{arcsec}^{-2}$ which corresponds to an upper limit on star formation of $\sim 10^{-11}~\mathrm{M_\odot~yr^{-1}~pc^{-2}}$, implying that the star formation in Leo T has ended.Comment: Accepted for publication in A&A on 04-08-2023. 17 pages, 17 figures, 3 table

The MUSE-Faint survey. V. Constraining Scalar Field Dark Matter with Antlia B

Aims. We use stellar line-of-sight velocities of Antlia B, a faint dwarf galaxy in the NGC 3109 association, to derive constraints on the fundamental properties of scalar field dark matter originally proposed to solve the small-scale problems faced by cold dark matter models. Methods. We use the first spectroscopic observations of Antlia B, a distant (d $\sim$ 1.35 Mpc) faint dwarf ($M_\text{V} = -9.7$, M$_\star \sim 8\times10^5$M$_\odot$), from MUSE-Faint - a survey of ultra-faint dwarfs with the Multi Unit Spectroscopic Explorer. Through measurement of line-of-sight velocities for stars in the $1'\times 1'$ field-of-view, we identify 127 stars as members of Antlia B, allowing us to model its dark matter density profile with the Jeans modelling code GravSphere. We implement a model for scalar field dark matter into GravSphere and use this to place constraints on the self-coupling strength of this model. Results. We find a virial mass of ${M_{200} \approx 1.66^{+2.51}_{-0.92}\times 10^9}$ M$_\odot$ and a concentration parameter of ${c_{200}\approx 17.38^{+6.06}_{-4.20}}$ for Antlia B. These results are consistent with the mass-concentration relations in the literature. We constrain the characteristic length scale of the repulsive self-interaction $R_{\text{TF}}$ of the scalar field dark matter model to $R_{\text{TF}} \lesssim 180$ pc (68% confidence level), which translates to a self-coupling strength of $\frac{g}{m^2c^4}\lesssim 5.2 \times 10^{-20}$ eV$^{-1}$cm$^3$. The constraint on the characteristic length scale of the repulsive self-interaction is inconsistent with the value required to match the observations of cores of dwarf galaxies in the Local Group, suggesting that the cored density profiles of those galaxies are not caused by scalar field dark matter.Comment: Accepted for publication in A&A on 21-07-2023. 17 pages, 22 figures, 4 table