Properties Of Mo Thin Films Research Articles

Properties of ultrathin molybdenum films for interconnect applications

The structural and electrical properties of Mo thin films with thicknesses between 3 and 50 nm, deposited by physical vapor deposition, have been evaluated in order to assess the potential of Mo as an alternative to Cu or W for nano-interconnect applications. Mo films deposited on SiO2/Si (100) were polycrystalline with randomly oriented grains close to the interface and the progressive formation of a (110) texture above 5 nm film thickness. Adhesion between Mo and low-κ dielectrics was strong with adhesion energies above 5 J/m2. The films showed intrinsic tensile stress of ∼1 GPa, which decreased with increasing thickness. The Mo resistivity showed a weaker thickness dependence than Cu, which rendered Mo competitive with conventional TaN/Cu/TaN metallization below metal thicknesses of 8 nm. Semiclassical resistivity modeling found that the thin film resistivity was limited by grain boundary scattering with a reflection coefficient of R = 0.46 ± 0.03. Furthermore, the effects of Mo deposition on different dielectric and metallic substrates and of post-deposition annealing up to 950ºC were investigated. Crystallinity, impurity concentration, and resistivity were all affected by the substrate. Post-deposition annealing in H2 led to continuous grain growth, followed by recrystallization at 860ºC. Furthermore, annealing at 650°C led to compressive stress in the films. By contrast, annealing in H2/N2 led to the incorporation of N and ultimately to Mo nitride formation above 500ºC. The results indicate that Mo can be a promising candidate for advanced interconnect metallization schemes if surface oxidation as well as impurity incorporation can be kept under control.

Optimization of low resistivity molybdenum thin films for high-temperature microheater applications

In this paper, we discuss the optimal DC magnetron sputtering deposition conditions needed to obtain low resistivity Molybdenum (Mo) thin films for high-temperature (800 °C) microheater applications. The influence of Ar gas pressure (2–10 mTorr), sputtering power (80–160 W), and annealing temperature (200–1000 °C) on the resistivity and adhesive properties of Mo thin films were investigated. The structural, morphological, and electrical properties of as-deposited and annealed Mo thin films were characterized by X-ray diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, and four-point probe techniques. The thin films deposited at 120 W, 6 mTorr, and annealed at 1000 °C showed low resistivity (18 μΩ-cm) and good adhesive properties. Suspended-membrane microheaters were fabricated using as-deposited and annealed Mo thin films, and their performance characteristics were compared. The impact of thin-film resistivity on power consumption and on the maximum operating temperature of Mo microheater was also investigated.

Effect of photon annealing and cryogenic temperature on the microstructure, optical and electrophysical properties of Mo thin films

Mo films were deposited on a polyimide substrate by dual magnetron sputtering in an UniCoad 200 vacuum unit with an unbalanced magnetic system. The dependence of the characteristics of the obtained Mo films on photon annealing and cryogenic temperature was studied. The photonic annealing of Mo films was carried out at temperatures of 200 °C and 300 °C. For cooling Mo films, liquid nitrogen was used (t = -190°С). The characteristics of the films were investigated using X-ray diffraction, scanning electron microscopy and scanning probe microscopy. The results are presented on the change in specific electrical resistance, diffuse reflection spectra and adhesion strength of Mo films. It is shown that photon annealing at different temperatures does not affect the intensity of the X-ray diffractogram peaks of the Mo coating. After exposure, at a cryogenic temperature, an insignificant change in the X-ray diffractogram occurs, a shift of the diffractogram peak (110) is observed to large angles 2θ from 40.72° to 40.89°. The obtained Mo coating has a columnar structure in the form of tightly packed polycrystallites, oriented perpendicular to the substrate of the polyimide film. Mo coating on a polyimide substrate is resistant to sudden thermal exposure at temperatures not higher than 300 °C. Processing the resulting coating with liquid nitrogen leads to strong cracking of the Mo coating. At the same time, on samples with a coating thickness of 380–400 nm, exfoliation of the Mo coating, in the place of fracture, is not observed. The adhesive strength of the Mo coating with a polyimide film is quite high – 1.11 ± 0.05 GPa. Photon annealing does not reduce the adhesive strength of the Mo coating. The Mo film under conditions of cryogenic temperature (0.89 ± 0.08 GPa) has the worst adhesion strength.

Physical and electrical properties of molybdenum thin films grown by DC magnetron sputtering for photovoltaic application

DC magnetron sputtering was utilized to grow thin layers of molybdenum (Mo) on top of soda lime glass substrates. Deposition power was varied for suitable characteristics of films grown at various DC powers, i.e. 100 W, 150 W and 200 W. Thin Mo film of approximately 580 nm thickness was successfully grown at DC power of 100 W at room temperature. Structural, morphological, electrical and optical properties of Mo thin films were analyzed. XRD patterns revealed Mo films to be monocrystalline in nature and only one peak was observed corresponding to the (1 1 0)cub reflection plane at 2θ = 40.5°. Exceptionally dense microstructure was found for surface morphology observation by AFM and FESEM. Increasing deposition power resulted in coarser surface of the grown films. The minimum average surface roughness was found to be around 0.995 nm. Scotch tape adhesion test was performed to validate adhesion. Grown Mo films were found metallic in nature with electrical resistivity of 2.64 × 10−5 Ω-cm. Furthermore, it was found that by increasing deposition power, the electrical resistivity could further be reduced.

Effects of Heating Mode and Temperature on the Microstructures, Electrical and Optical Properties of Molybdenum Thin Films.

In this paper, molybdenum (Mo) thin films are deposited on soda-lime glass (SLG) substrates by direct current magnetron sputtering and heated in three different modes at different temperatures, including substrate heating, annealing treatment, and both substrate heating and annealing treatment. The effects of heating temperature and heating mode on the structures, morphology, optical and electrical properties of Mo thin films were systematically investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), atomic force microscope (AFM) and UV-visible spectrophotometer (UV-vis spectra). It is shown that as the substrate and annealing temperature increase, the crystallinity of Mo thin films is improved, and the grain sizes become bigger. Especially in the mode of both substrate heating and annealing treatment at higher temperature, the obtained Mo thin films show higher crystallinity and conductivity. Moreover, with the increase of substrate and annealing temperature in different heating modes, both the surface compactness of Mo films and the optical reflectance increase correspondingly. Furthermore, the Mo film, prepared at the substrate heating temperature of 400 °C and annealed at 400 °C, showed excellent comprehensive performance, and the resistivity is as low as 1.36 × 10−5 Ω·cm. Using this optimized Mo thin film as an electrode, copper indium gallium selenium (CIGS) solar cells have a maximum photo-conversion efficiency of 12.8%.

Electrical, structural, and topographical properties of direct current (DC) sputtered bilayer molybdenum thin films

Renewable energy sources offer a viable green energy solution to the increasing global energy demands, and the photovoltaics offers a means of tapping into the abundance of the solar energy. Molybdenum (Mo) thin film has been used as a back-contact electrode in high-efficiency solar cells mainly due to its ohmic nature with the absorber material (especially with chalcopyrites and kesterites), low resistivity, adequate reflectance, and porosity to alkali materials. Mo thin films used in solar cells are deposited by direct current (DC) sputtering under argon ion atmosphere. The present work deals with the effects of the sputtering deposition conditions (i.e., working pressure and power) on the electrical properties of Mo thin films deposited on soda-lime glass using DC magnetron sputtering at different working pressures (5–20 mTorr) and deposition powers (100–800 W). Optimized deposition power and sputtering pressure were used to deposit a Mo bilayer thin film intended for solar cells application. X-ray diffractometric studies showed the (110) plane corresponding to the body-centered cubic structure of the Mo material. Calculated values were used to estimate other parameters of the deposited films (e.g., stress, dislocation density), as these properties affect the potential diffusion of sodium (Na) through the soda-lime glass into the absorber layer that is important as the moderate inclusion of Na improves the cell efficiency. The cross-section of the deposited film was analyzed using a field-emission scanning electron microscopy, to confirm the successful deposition of the bilayer. The surface of the films plays a vital role in the Mo interface with the absorber layer. Atomic force microscopy was used to acquire the topographical information from the sputtered bilayer film. The resistivity, as measured using a four-point probe, of the Mo films deposited at different conditions was in the order of 10−6 Ω m while the resistivity of the bilayer was 0.60 × 10−6 Ω m.

两种钼靶材溅射钼薄膜的组织性能研究

两种钼靶材溅射钼薄膜的组织性能研究

Role of Pre-Layer Mo Films in Microstructural and Morphological Properties of Over-Layer CIGS Films

ABSTRACTThis study focuses on establishing a microstructural and morphological correlation between CIGS films and its precursor layer of Molybdenum (Mo) coated soda-lime glass (SLG). Therefore, variations in the morphology and microstructural properties of Mo thin films, using DC planar magnetron sputtering, were induced systematically by varying the sputtering pressure from 0.6 to 16 mT with a sputtering power density of 1.2 W/cm2. Subsequently, under fixed deposition conditions (deposition rate and substrate temperature), a growth of Cu(In,Ga)Se2 (CIGS) films was carried out on the Mo-coated SLG substrates, using the 3-stage growth process of the physical vapor deposition (PVD) technique.High-Resolution Scanning Electron Microscopy (HRSEM) was used to examine the Mo and CIGS films morphology. X-Ray Diffraction (XRD) was applied to study in detail the microstructure of Mo and CIGS films. Where, the films’ crystal structure including the preferred orientation and the lattice parameters were determined by the θ/2θ XRD technique and by applying Cohen’s least-square method. Furthermore, Atomic Force Microscopy (AFM) was used to determine the root-mean-square (RMS) surface roughness of the CIGS films.

Improvement of the adhesion of the backside Mo electrode in a copper indium gallium selenide solar cell with good electrical properties

Molybdenum thin films are widely used as the back electrode for copper indium gallium selenide solar cells. In this paper, the crystal structures and electrical and mechanical properties of Mo thin films were studied as a function of working gas pressure. It was found that the numerous micro-voids appearing in the surface of the Mo thin film deposited at high working gas pressure could be attributed to the low kinetic energy of sputtered atoms on the glass substrate. In addition, Mo thin films with large grain sizes and better crystallinity can also be obtained in the low working gas pressure owing to the high diffusivity of Mo atoms on the glass substrate. The residual stress of Mo thin film changed from compressive stress to tensile stress when the working gas pressure was increased from 2·5 to 15 mTorr. The electrical resistivity of Mo thin films increased monotonously with working gas pressure. This can be explained by the increase in the number of grain boundaries and micro-voids in the Mo thin film deposited at high working gas pressure, which alleviate grain boundary scattering and increase the carrier lifetime.

The effect of deposition parameters and post treatment on the electrical properties of Mo thin films

In this study, we deposited low-resistivity molybdenum (Mo) thin films on soda-lime glass substrates with good adhesion. We adjusted various deposition parameters such as the sputtering power (52–102W), working distance (5.5–9cm) and annealing temperature (26–400°C) to investigate their impact on the sheet resistance. By using a DC magnetron sputtering system, we obtained Mo thin films having the lowest sheet resistance of 0.190Ω/□ with a sputtering power of 82W, working distance of 6.5cm, and annealing temperature of 400°C; in addition, these films had good adhesivity. These Mo thin films were suitable for use as the Mo back contact in Cu(In,Ga)Se2-based solar cells.

Oxidation of Molybdenum Thin Films and its Impact on Molybdenum Field Emitter Arrays

AbstractOxidation of emitter surfaces can be a serious problem for Mo field emitter arrays. We studied the oxidation and related changes in the electronic properties of Mo thin films as a function of annealing temperature. Experiments were done on Mo thin films prepared on Si and sodalime glass substrates. These films were thermally oxidized and characterized using a variety of techniques including x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and thermal desorption spectroscopy (TPD) methods. For films oxidized below 400°C, partial oxidation was observed, with MoO3(110) being the principal oxide phase. However, at a temperature of 500°C and above, oxidation of the film was complete. Electrical characteristics of the films undergo a rapid transition from semiconductive to highly insulating at temperatures between 475 to 500°C. Temperature programmed desorption spectra showed that the oxides are stable at elevated temperature with only a principal O2 desorption peak at approximately 786°C.