Molybdenum Silicide Films Research Articles

Fast and efficient detection of a single photon with hole-patterned superconductor microstrips

In this Letter, we report on pattern engineering in superconducting microstrips to achieve a fast and efficient detection of a single-photon over a large detection area. The proposed detector is composed of hole-patterned superconductor microstrips fabricated with a 5-nm-thick amorphous molybdenum silicide film. It exhibits a saturated internal detection efficiency at 1550 nm with a negligible dark count rate and a recovery time of 9 ns with a large detection area (50 × 50 μm2). The simulation reveals that the holes patterned in the superconductor microstrip stimulate the nucleation of the vortex, which constitutes a major key to achieving the efficient detection of photons. This work paves the way for the facile and prolonged regulation of vortex nucleation in superconductors, which shows promise for developing high-performance large-area superconductor single-photon detectors.

Physical properties of amorphous molybdenum silicide films for single-photon detectors

We systematically investigated the physical properties of amorphous Mo x Si1−x films deposited by magnetron co-sputtering. The critical temperature T c of Mo x Si1−x films increases gradually with the Mo stoichiometry x, and the highest T c = 7.9 K was found in Mo0.83Si0.17, where homogeneous films with the maximum Mo content can be obtained. The thick films of Mo0.83Si0.17 show surprising degradation in which the onset of zero-resistivity is suppressed below 2 K. The thin Mo0.83Si0.17films, however, reveal robust superconductivity even with thickness d ≈ 2 nm. We also characterized wide microwires based on the 2 nm thin Mo0.8Si0.2 films with wire widths 40 and 60 μm, which show single-photon sensitivity at 780 nm and 1550 nm wavelength.

Enhancement of Superconductivity by Amorphizing Molybdenum Silicide Films Using a Focused Ion Beam.

We have used focused ion beam irradiation to progressively cause defects in annealed molybdenum silicide thin films. Without the treatment, the films are superconducting with critical temperature of about 1 K. We observe that both resistivity and critical temperature increase as the ion dose is increased. For resistivity, the increase is almost linear, whereas critical temperature changes abruptly at the smallest doses and then remains almost constant at 4 K. We believe that our results originate from amorphization of the polycrystalline molybdenum silicide films.

Surface morphology of molybdenum silicide films upon low-energy ion beam sputtering

The surface morphology of molybdenum silicide (MoxSi1−x) films has been studied after low-energy Ar+ ion beam sputtering (IBS) to explore eventual pattern formation on compound targets and, simultaneously, gather information about the mechanisms behind silicide-assisted nanopatterning of silicon surfaces by IBS. For this purpose, MoxSi1−x films with compositions below, equal and above the MoSi2 stoichiometry (x = 0.33) have been produced by magnetron sputtering, as assessed by Rutherford backscattering spectrometry (RBS). The surface morphology of silicon and silicide films before and after IBS has been imaged by atomic force microscopy (AFM), comprising conditions where typical nanodot or ripple patterns emerge on the former. In the case of irradiated MoxSi1−x surfaces, AFM shows a marked surface smoothing at normal incidence with and without additional Mo incorporation (the former results in nanodot patterns on Si). The morphological analysis also provides no evidence of ion-induced phase separation in irradiated MoxSi1−x. Contrary to silicon, MoxSi1−x surfaces also do not display ripple formation for (impurity free) oblique irradiations, except at grazing incidence conditions where parallel ripples emerge in a more evident fashion than in the Si counterpart. By means of RBS, irradiated MoxSi1−x films with 1 keV Ar+ at normal incidence have also been used to measure experimentally the (absolute) sputtering yield and rate of Si and MoxSi1−x materials. The analysis reveals that, under the present working conditions, the erosion rate of silicides is larger than for silicon, supporting simulations from the TRIDYN code. This finding questions the shielding effect from silicide regions as roughening mechanism in metal-assisted nanopatterning of silicon. On the contrary, the results highlight the relevance of in situ silicide formation. Ripple formation on MoxSi1−x under grazing incidence is also attributed to the dominance of sputtering effects under this geometry. In conclusion, our work provides some insights into the complex morphological evolution of compound surfaces and solid experimental evidences regarding the mechanisms behind silicide-assisted nanopatterning.

Swift heavy ion induced effects at Mo/Si interface and silicide formation

AbstractSwift heavy ion (SHI) induced modification at metal/Si interfaces has emerged as an interesting field of research due to its large applications. In this study, we investigate SHI‐induced mixed molybdenum silicide film with ion fluences. The molybdenum thin films were deposited on silicon substrates using e‐beam evaporation at 10−8 torr vacuum. Thin films were irradiated with Au ions of energy 120 MeV to form molybdenum silicide. The samples were characterized by grazing incidence X‐ray diffraction (GIXRD) technique for the identification of phase formation at the interface. Rutherford backscattering spectrometry (RBS) was used to investigate the elemental distribution in the films. The mixing rate calculations were made and the diffusivity values obtained lead to a transient melt phase formation at the interface according to thermal spike model. Irradiation‐induced effects at surface have been observed and roughness variations at the surface were calculated using atomic force microscopy (AFM) technique. Copyright © 2009 John Wiley & Sons, Ltd.

Characteristics of ion-beam-synthesized molybdenum silicide film

This parametric study investigates the characteristics of ion-beam-synthesized molybdenum silicide film with various ion fluences, silicon orientations and post-annealing conditions. The implantation of molybdenum ions into silicon substrate was performed using a metal vapor vacuum arc at 40kV, while the rapid thermal annealing method was subsequently applied to form the molybdenum silicide film. The film characteristics were determined using X-ray diffractometry, resistometry, Rutherford backscattering spectrometry, transmission electron microscopy and secondary ion mass spectrometry. The results revealed that a flat and continuous molybdenum silicide film with superior properties could be obtained when implanted at an ion fluence of 3×1017cm−2 into 〈100〉 silicon substrate at 100°C and then rapid-thermal-annealed at a temperature greater than 800°C for 30s.

Deposition of Conductive Films on Semiconductor Substrates via Molybdenum Hexacarbonyl Decomposition in Glow Discharge

The properties of films deposited via molybdenum hexacarbonyl decomposition in glow discharge are found to depend strongly on the nature of the substrate and the sign of bias. Molybdenum films are obtained on SiO2 /Si at any bias and on Si, GaAs, InP, and InAs substrates at positive bias. At negative bias, molybdenum silicide films are produced on Si. The films deposited at positive bias have the highest electrical conductivity. X-ray diffraction, Auger electron spectroscopy, and sheet resistance data are used to elucidate the mechanism of film deposition via molybdenum hexacarbonyl decomposition in glow discharge.

Step Coverage of Molybdenum Silicide Sputtering Films Investigated by Monte Carlo Method

The step coverage of molybdenum silicide films deposited using a MoSi2.5 target was observed by Auger analysis and scanning electron microscopy. The composition of the films deposited on substrates placed parallel or perpendicular to the target was also measured by the Rutherford backscattering spectroscopy (RBS) method. It was found that the films deposited on the sidewall of the steps or the substrates placed perpendicular facing the outside of the sputtering chamber were very rich in Si compared with the target with Si/Mo ratio of 2.5. The compositions of those films could take values as large as 5. A considerable part of this excess Si was ascribed to the turning around of Si atoms due to scattering by Ar gas. In order to understand the experimental results, simulation of film deposition was carried out, where the scattering effect by Ar gas was considered using the Monte Carlo method.

Corrosion properties of thin molybdenum silicide films

The corrosion properties of sputtered molybdenum and molybdenum silicide films in hydrochloric acid (HCl) have been studied by means of potentiodynamic measurements. Contributions from the substrate to the corrosion behaviour was avoided by depositing the films on inert aluminium oxide (Al 2O 3). The compositions studied were Mo, MoSi 0.58, MoSi 1.04, MoSi 1.4 and MoSi 1.9–2.1. Characterisation of the sampies was made by X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after corrosion. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to analyse the polarised films. Corrosion of M 3Si was found in the molybdenum-rich samples (MoSi 0.58) containing the two phases Mo 3Si and Mo 5Si 3. Polarisation curves for these films showed one passivation peak at 228 mV vs. the saturated calomel electrode (SCE). The MoSi 1.9–2.1 films had the best corrosion properties of the films studied. This composition had three passivation peaks, at about 154, 305 and 1850 mV SCE, respectively. In the silicon-rich samples, containing the phases MoSi 2 and Mo 5Si 3, preferentiai corrosion of Mo 5Si 3 was found. All the samples containing the disilicide phase showed at least two passivation peaks. XPS and AES studies on the passive films formed on the samples at the two first passivation peaks indicate that both peaks are due to oxidation of silicon- and molybdenum-containing species. The amount of molybdenum in the outermost layer is increased after the second peak.

Study of Biaxial Stress Induced by Cosputtered Thin Molybdenum Silicide Films in Silicon Single-Crystal Substrates

Bending of 25 mm-diameter (100) silicon wafers produced by 100 nm-thick cosputtered molybdenum–silicon films has been investigated just after deposition, after rapid thermal annealing and after etching of the deposits. Values of biaxial stress in the films were determined by the use of a widely used relation. The Mo:Si ratio in the as-deposited films was 89:11. Radii of curvature of substrates were measured by a double-crystal X-ray diffractometer. Blank wafers with three widely different radii of curvature (33, 62 and 250 m) were chosen as specimens and their curvatures were taken into account in the determination of the value of biaxial stress in wafers with deposits. All the wafers were convex when viewed from the polished surface side on which the films were deposited. Values of σ for wafers with as-deposited films were in the range 3 × 108 to 14 × 108 Nm−2 (tensile). Wafers with higher initial bending showed higher values of stress. Deposition led to degradation of perfection, as revealed by broadening of the diffraction curves and the contrast in the topographs. Rapid thermal annealing at 1273 and 1373 K (3–4 min) led to formation of the MoSi2 phase and to a notable relaxation of stress. The values of σ were in the range 1 × 107 to ~6 × 108 N m−2 (tensile). The value of the stress was lowest for the blank wafer with smallest bending. Annealing also improved the degree of crystalline perfection of the silicon. Experiments performed after etching of the annealed specimens showed no significant change in the radii of curvature.

High-performance VLSI photomask with a molybdenum silicide film

A molybdenum silicide (MoSi) film deposited on a quartz substrate offers major advantages as a high-performance photomask material for VLSI fabrication. There is no missing pattern due to exfoliation after ultrasonic cleaning with a frequency of 28 kHz and 300 W of power, and after being scrubbed over fifteen cycles with a high-pressure water jet. Reflectivity and optical density of the MoSi film are not affected by acidic chemicals. Dry etching with CF 4 + O 2 gas plasma can be performed at a rate of 70 nm/min, which is about five times as fast as the etch rate for chromium (Cr) masks. Moreover fabrication of submicron patterns using poly(buten-1 sulfone) (PBS) resist, a positive electron beam resist with very poor resistance to dry etching, has been realized. In addition a photomask with a MoSi film is easier to repair by focused ion beam than one with a Crfilm because of the higher sputter yields for a MoSi film.

Fabrication technologies for advanced 5X reticles for 16M-bit dynamic random access memory

Fabrication technologies for advanced photomasks with a molybdenum silicide (MoSi) film have been developed by using a variable-shaped electron-beam (e-beam) system. These technologies were applied to the fabrication of 5X reticles for 16M-bit DRAMs. The variable-shaped e-beam system is very effective in increasing the throughput for writing reticles which have a great number of figures, such as 16M-bit DRAMs. The average writing time was 100 min, which was ∼ (1)/(3) of the time when using a conventional raster-scan e-beam system. Photomasks with the MoSi film have advantages in comparison with those with conventional chromium (Cr) film. Pattern defects did not appear during the photomask cleaning because of strong adhesion of the MoSi film to the quartz substrate. Moreover, an accurate feature size on the photomasks was obtained, because the MoSi film was easily dry etched. The feature size accuracy obtained was 0.03 μm in 3σ all over the 5 in. blanks.

Effects of substrate bias on the resistivity and microstructure of molybdenum and molybdenum silicide films

Effects of substrate bias on the resistivity and microstructure of molybdenum and molybdenum silicide films

Chemical Vapor Deposition of Molybdenum Silicide

A cold‐wall reactor has been used to deposit molybdenum silicide films from a mixture of and . The composition of the resulting films can be controlled by the deposition temperature, and stoichiometry is obtained with a substrate temperature of 200°C. The film composition is independent of reactant gas ratios in the range of 1–10. The as‐deposited films are generally amorphous as determined by x‐ray analysis. Annealing at 950°C in argon converts the films to tetragonal polycrystalline .

Effects of substrate bias on the resistivity and microstructure of molybdenum and molybdenum silicide films

A continuous series of Mo-Si alloys (Mo x Si 1− x ), with 0.3 ⩽ x ⩽ 1, have been deposited by reactive magnetron sputtering of molybdenum in silane and argon plasma. The effects of sputter deposition parameters such as the deposition rate, substrate temperature, substrate bias and gas flow conditions on the resistivity of molybdenum and molybdenum silicide films are reported. The resistivity of molybdenum films shows a pronounced decrease with an increase in the negative substrate bias and the rate of film growth. An electrical resistivity as low as 7.8 μΩ cm has been obtained in molybdenum films by optimizing the deposition conditions. The resistivity of MoSi 2 films, measured after annealing them at 1000°C for 1 h in nitrogen ambient, shows a broad minimum at −75 V bias. However, the effect of bias is not as pronounced as for molybdenum. The changes in the resistivity of molybdenum and MoSi 2 films are attributed to the degree of oxygen contamination and microstructural modifications during growth.

High performance very large scale integrated photomask with a silicide film

A molybdenum silicide (Mo-silicide) film deposited on a quartz glass substrate offers major advantages as a high performance photomask material for very large scale integrated (VLSI) fabrication. There is no pattern missing due to exfoliation after ultrasonic cleaning with frequency of 28 kHz and 300 W of power, and after being scrubbed over 10 cycles with a high pressure water jet. Reflectivity and optical density of the Mo-silicide film are not affected by acidic chemicals. Moreover, dry etching can be done at a rate of 50 nm/min; more than five times as fast as etching of a chromium (Cr) mask.

Optical Characterization of Amorphous and Crystalline Molybdenum Silicide Films

The optical spectra of the silicides of Mo are investigated and compared with existing band structure information. The molybdenum-silicon layers have been prepared by sputtering from sintered Mo-Si samples onto quartz substrate, by deposition of Mo on Si substrate and annealing, or by Si/sup +/ implantation in Mo layers. Amorphous as well as crystalline layers have been studied. The film thickness varied from 40 to 400 nm. Transmission measurements were carried out on thin samples. Nearly normal incidence reflectivity measurements were performed on thicker samples. The absorption coefficient ..cap alpha.. as a function of photon energy for amorphous, partially crystalline, and polycrystalline hexagonal and tetragonal MoSi/sub 2/ layers are plotted yielding an optical pseudo-gap in the density of states at the Fermi energy of 1.3 eV. It seems that a similarity exists in the band structure of the group VI disilicides.

Properties of MoSi 2 films deposited from a composite target

Thin molybdenum silicide films were deposited from a cold-pressed, vacuum-sintered composite target in a Varian 3180 sputtering system onto silicon wafers 100 mm in diameter. The argon pressure was varied from 4 to 15 mTorr and the substrate temperature from ambient to 450°C. The deposition rate, ratio of silicon to molybdenum, phase and thickness uniformity were found to be independent of these deposition variables. A minimum post-sintered resistivity of 82 μΩ cm was obtained on samples deposited at ambient temperature. Pressure and especially temperature affect the resistivities, and these effects may be explained from the impurity and grain size results.

Tensile stress in sputtered molybdenum silicide films

Isothermal changes in tensile stresses depending on the amount of MoSi2 formed in sputter deposited films which have multilayered structures of molybdenum and silicon (atomic ratio, Si/Mo=2) have been investigated. The amount of MoSi2 formed in the films was controlled isothermally by changing a layer thickness parameter t* from 0 to 220 Å which was the sum of both the molybdenum layer and silicon layer thicknesses. The films were deposited on oxidized silicon wafers and sintered in the temperature range 440–1000 °C. The tensile stress increases to 1.5×10 10 dyn cm−2 linearly with increasing 1/t* and saturates with further increase in 1/t*. Since 1/t* is proportional to the amount of MoSi2 formed in the films, the stress is found to increase with an increasing amount of crystallized MoSi2 in the films and to saturate when the whole multilayered films are completely converted into MoSi2 films. Furthermore, it is suggested that relaxation of the tensile stress occurs in proportion to the amount of crystallized MoSi2.

ChemInform Abstract: PROPERTIES OF MOLYBDENUM SILICIDE FILM DEPOSITED BY CHEMICAL VAPOR DEPOSITION

Chemischer InformationsdienstVolume 14, Issue 46 Preparative Inorganic Chemistry ChemInform Abstract: PROPERTIES OF MOLYBDENUM SILICIDE FILM DEPOSITED BY CHEMICAL VAPOR DEPOSITION S. INOUE, S. INOUESearch for more papers by this authorN. TOYOKURA, N. TOYOKURASearch for more papers by this authorT. NAKAMURA, T. NAKAMURASearch for more papers by this authorM. MAEDA, M. MAEDASearch for more papers by this authorM. TAKAGI, M. TAKAGISearch for more papers by this author S. INOUE, S. INOUESearch for more papers by this authorN. TOYOKURA, N. TOYOKURASearch for more papers by this authorT. NAKAMURA, T. NAKAMURASearch for more papers by this authorM. MAEDA, M. MAEDASearch for more papers by this authorM. TAKAGI, M. TAKAGISearch for more papers by this author First published: November 15, 1983 https://doi.org/10.1002/chin.198346038Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue46November 15, 1983 RelatedInformation