Annealing effects on microstructure and properties of Ta-Al thin film resistors

The Ta-Al thin film resistor has been used as a heating element of the thermal bubble inkjet printhead with several millions of thermal cycle operations between room temperature and about 350 °C. In this paper, the thermal stability of Ta-Al alloy films was investigated by the variation of phase transformation, microstructure and resistivity at annealing temperatures of 450-650 °C for 1 h. Three kinds of Ta-Al films were prepared with average Ta/Al atomic composition ratios of about 2/1, 1/1 and 1/2, respectively. The Ta-Al film with composition ratio of about 1/1 exhibits amorphous-like microstructure with nanocrystalline grains embedded in an amorphous matrix. The thermal stability is strongly related to the composition and microstructure in Ta-Al alloy. The best thermal stability of Ta-Al films occurs in Ta-rich alloy up to 650 °C and the worst occurs in Al-rich alloy with phase transformation as low as 450 °C. The amorphous-like Ta-Al alloy is stable up to 550 °C, but then exhibits polycrystalline multiphase formation at 650 °C. The resistivity of Ta-Al films is also related to the annealing temperature. The resistivity of Ta-rich Ta-Al film increases to about 13.5% from as-deposited to after annealing at 450 °C while that is doubled in the Al-rich Ta-Al film. In contrast, the resistivity of the amorphous-like Ta-Al film increased by about 6.1% at 450 °C and then remains nearly stable at 1.5% variation on annealing at 450-550 °C. The as-deposited amorphous-like Ta-Al film has the merits of high resistivity, smooth morphology and good thermal stability at annealing temperatures of up to 550 °C. These attributes are beneficial for the thermal bubble inkjet application with thermal cycling at maximum temperatures below 400 °C.     

化学镀 Ni-Mo-P 合金镀层的组织结构与防垢性能研究

目的采用材料测试方法和防垢实验,研究不同工艺条件下的化学镀Ni-Mo-P合金镀层的组织结构与防垢性能。方法在化学镀Ni-P镀层基底上,添加含有钼酸根离子杂多酸盐,在不同工艺条件下化学沉积Ni-Mo-P合金镀层,研究化学镀Ni-Mo-P合金镀层的表面形貌和组织结构,分析镀液中硼酸含量和钼酸铵含量对镀层沉积速率的影响,观测镀层在结垢实验后的表面形貌并分析结垢速率。通过SEM,XRD和EDS对化学镀Ni-Mo-P合金镀层的表面形貌和组织结构进行检测,研究在酸性镀液中硼酸含量对化学镀Ni-Mo-P工艺条件的影响。采用防垢实验测试化学镀Ni-Mo-P合金镀层的防垢性能。结果在化学镀Ni-Mo-P过程中,钼酸根离子杂多酸盐具有稳定作用。化学镀Ni-Mo-P合金镀层的化学沉积镀液的最佳工艺条件为:Ni SO4·6H_2O 16.5 g/L,Na H_2PO_2·H_2O 20 g/L,钼酸钠0.5~0.8 g/L,硼酸2 g/L,乙酸钠7.5 g/L。化学镀Ni-Mo-P合金镀层的结垢速率明显低于化学镀Ni-P镀层,具有良好的防垢能力,形成了非晶态的镀层。结论采用化学镀Ni-P镀层基底上沉积得到非晶态的Ni-Mo-P合金镀层,硼酸具有调节镀液p H值和络合作用,非晶态的Ni-Mo-P合金镀层平均结垢速率最小值为0.58μm/h,具有良好的阻垢能力。     

Temperature dependence of copper diffusion in different thickness amorphous tungsten/tungsten nitride layer

The amorphous W/WN films with various thickness (10, 30 and 40 nm) and excellent thermal stability were successfully prepared on SiO₂/Si substrate with evaporation and reactive evaporation method. The W/WN bilayer has technological importance because of its low resistivity, high melting point, and good diffusion barrier properties between Cu and Si. The thermal stability was evaluated by X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM). In annealing process, the amorphous W/WN barrier crystallized and this phenomenon is supposed to be the start of Cu atoms diffusion through W/WN barrier into Si. With occurrence of the high-resistive Cu₃Si phase, the W/WN loses its function as a diffusion barrier. The primary mode of Cu diffusion is the diffusion through grain boundaries that form during heat treatments. The amorphous structure with optimum thickness is the key factor to achieve a superior diffusion barrier characteristic. The results show that the failure temperature increased by increasing the W/WN film thickness from 10 to 30 nm but it did not change by increasing the W/WN film thickness from 30 to 40 nm. It is found that the 10 and 40 nm W/WN films are good diffusion barriers at least up to 800°C while the 30 nm W/WN film shows superior properties as a diffusion barrier, but loses its function as a diffusion barrier at about 900°C (that is 100°C higher than for 10 and 40 nm W/WN films).     

AgMgAl metallic glassy and intermetallic thin films for electric contact applications

The AgMgAl thin films, in an attempt in replacing the expensive pure Au contact films, are prepared by co-sputtering. The surface morphology, roughness, amorphous or crystalline atomic structure, grain size, and electric resistivity are systematically examined. Depending on the film compositions, the films can be fully amorphous or fully nanocrystalline, or a composite with the mixture of nanocrystalline phases dispersed in the amorphous matrix. Under the as-sputtered condition, the crystalline group has the lowest resistivity, ranging from 27 to 37 μΩ·cm, the composite group lies in the middle, 31–70 μΩ·cm, and the fully amorphous group possesses the highest resistivity, 87–122 μΩ·cm. Appropriate short thermal annealing for the amorphous films can drastically lower the resistivity down to as low as 9 μΩ·cm, already compatible to pure Au (3–7 μΩ·cm). This study demonstrates the feasibility of the AgMgAl films in replacing the pure Au.     

Gas detonation spray forming of Fe-Al coatings in the presence of interlayer

The present paper reports that gas detonation sprayed (GDS) NiAl and NiCr intermediate layers underneath of the intermetallic Fe-Al type coatings on plain carbon steel substrate form bilayer coating system interacting with external environment and/or metal elements. The interface layers are responsible for hardness, bond strength, thermal stability and adhesive strength of the whole GDS structure. The physical-chemical properties of the intermediate layers, combined with unique, very dense and pore free intermetallic Fe-Al coating obtained from self-decomposing powders resulted in new, beneficial features of the whole GDS structure which became more complex, enabled independent control of its functional properties and considerably reduced negative gradients of stress and temperature influencing the substrate and increasing adhesion strength.The achievement of homogenous and refined structure (comprising of small (< 1 µm) and equiaxed sized grains) creates a thermal barrier based on high-melting point intermetallic phases containing Al₂O₃ ceramics which is responsible for properties of the GDS bilayer coatings. The application properties were investigated and the specific multilayer structure of the GDS coating was analyzed such as the phase composition, the degree of order, grain morphology, the quality of substrate/interlayer/external coating bonds, and first of all the influence of hardness of the NiAl or NiCr intermediate layers on the hardness and thermal stability of the FeAl coating after gas detonation spraying and additional heating at 750 °C and 950 °C for 10 h.     

Thermal stability of Ta-Si-N nanocomposite thin films at different nitrogen flow ratios

Ta-Si-N thin films were applied as diffusion barriers for Cu interconnections or hard coatings in mechanical application. The resistivity, hardness and thermal stability were the important issues in the interconnections and hard coatings, respectively. In this paper, we investigated the relationship between the microstructures, resistivity, nanohardness and thermal stability of the Ta-Si-N thin films at different nitrogen flow ratios of 0-30% (N₂% = N₂ / (Ar + N₂) × 100%) by magnetron reactive co-sputtering. The Ta-Si-N films were annealed at 600, 750 and 900 °C at about 6 × 10⁻³ Pa for 1 h, respectively, to examine their thermal stability. The microstructures of Ta-Si-N films at low N₂% of 2-10% still retained the amorphous-like phase with nanocrystalline grains in an amorphous matrix at annealing of 600-900 °C. The nanohardness of amorphous-like Ta-Si-N film at N₂% of 3% was measured to be 15.2 GPa much higher than that of polycrystalline film of 10.1 GPa at N₂% of 20%. The average nanohardness of both films is stable up to 900 °C and varied in the range of 0.43-0.83 GPa. The resistivity of the as-deposited Ta-Si-N films increase with increasing N₂ flow rate. It is small around 220-540 μΩ cm for low N₂% of 2-10% while it increases abruptly to about 7700-43,000 μΩ cm at high N₂% of 20-30%. The best thermal stability of resistivity of Ta-Si-N film occurs at the N₂% of 2% in the range of 220 to 250 μΩ cm from RT to 900 °C.     

Thermally induced decomposition of B4C barrier layers in Mo/Si multilayer structures

We investigate the influence of the Mo crystalline state (quasi-amorphous or crystalline) on the thermal stability of Mo/Si thin film multilayers with B₄C diffusion barrier layers at either of the two interfaces. We find that multilayers containing amorphous Mo layers are more stable than those containing crystalline layers. This observation is in contrast to the case where Si₃N₄ diffusion barriers are used. Using X-ray diffraction, X-ray reflection and X-ray photo-electron spectroscopy we show that this difference can be attributed to the dissociation of B₄C followed by diffusion of B in Mo. Due to the favorable thermodynamic properties of Mo_xB_y compounds, the boron atoms react with the Mo layer, forming a Mo_xB_y layer that effectively improves the multilayer thermal resistance.     

Thermal stability of tungsten nitride films deposited by reactive magnetron sputtering

The studies of thermal stability of nitride coatings are important since their structural, thermal, electrical and optical properties are drastically modified by the oxidation layer formed on the top of these coatings. Tungsten nitride films were deposited from metallic tungsten target using reactive pulsed d. c. magnetron sputtering. The films were annealed in air at different temperatures for 1 h. The structural, electrical resistivity and optical properties of the annealed films were analyzed. Besides the film analysis, powder of tungsten nitride was obtained by scratching the coating from the glass substrates. The oxidation kinetics of the scratched powder was studied using simultaneous thermal gravimetric/deferential thermal analysis measurements. X-ray diffraction patterns revealed that W₂N oxidizes to the two different phases WO₃ and WO_2.92. The oxide diffraction peaks appeared upon annealing at 773 K and the relative intensities increased with annealing temperature. The tungsten nitride was found to oxidize according a parabolic relation between mass gain and oxidation time. The activation energy of oxidation was evaluated by analyzing the Arrhenius relation from the temperature dependence of the weight gain. The obtained value was 1.76 eV. The activation energies of crystallization of the two phases were calculated. The electrical resistivity was found to increase drastically upon oxidation. The optical properties of the films are very sensitive to the oxidation temperature. The optical band gap values for the film oxidized at 773 K and 823 K are 2.71 and 2.58 eV, respectively.     

Modification of the electrical properties of polyimide by irradiation with 80 keV Xe ions

We modify the electrical properties of polyimide (PI) films by irradiation with 80 keV Xe ions. The surface resistivity of irradiated PI film at room temperature decreases remarkably from 1.2 × 10¹⁴ Ω/□ for virgin PI film to 3.15 × 10⁶ Ω/□ for PI film irradiated by 5.0 × 10¹⁶ ions/cm², and the temperature dependence of the resistivity of the treated films is well-fit using Mott's Equation. The irradiated PI film structure is studied using Raman spectroscopy, X-ray diffraction, and Rutherford Backscattering Spectrometry. The concentration of O in the irradiated layer decreases with increasing fluence, while the variation of N concentration is negligible. Graphite-like carbon-rich phases are created in the irradiated layers, leading to the modification of the electrical properties.     

酸性Ni-Mo-P/Ni-P双层化学镀工艺研究

对酸性Ni-Mo-P／Ni—P双层直接连续化学镀的工艺进行了试验研究。通过对钼酸根与次磷酸根加量比对镀速的影响，络合剂与pH对镀速及成分影响的研究，优化得到一种双层化学镀的酸性镀液的组成。试验研究了钼含量对镀层结构的影响，进而确定了具有非晶结构的双层镀的最佳工艺并对其性能进行了研究。     

Improvement in oxidation resistance of a Ni3Al-based superalloy IC6 by rhenium-based diffusion barrier coatings

The oxidation behavior of a Ni₃Al-based superalloy IC6 coated with a duplex Re–Cr–Ni–Mo diffusion barrier layer and an Al reservoir layer was investigated in air at 1423 K for up to 1080 ks. The diffusion barrier layer was formed by electroplating Re(Ni) and Ni films on the alloy, followed by Cr pack cementation at 1573 K, and as a result, forms a continuous inner Re–Cr–Ni–Mo diffusion barrier layer and an outer Ni(Cr,Mo,Al) layer. Then a Ni film was electroplated on the Ni(Cr,Mo,Al) layer, followed by Al-pack cementation at 1273 K for 18 ks, to form an Al reservoir layer with a duplex Ni₂Al₃ and γ-Ni(Cr,Mo,Al) layers. After oxidation at 1423 K in air for 1080 ks, the Al reservoir layer changed to a γ-Ni–4Cr–5Mo–12Al (all in at%) layer, on which a protective α-Al₂O₃ scale formed. The Re–Cr(Mo)–Ni layer was stable and effectively retarded the interdiffusion between the Al reservoir layer and the alloy, as a result, the depth of the microstructural change zone of the alloy was less than 15 μm. In contrast, the bare and the coated IC6 superalloy only with an Al reservoir layer were significantly oxidized, accompanied by serious spallation of oxide scales. After oxidation at 1423 K for 1080 ks, the depth of the microstructural change zone of the alloy was about 200 μm for the bare and coated alloy only with an Al reservoir layer. These results indicate that the oxidation resistance of IC6 superalloy can be effectively improved by coating with a Re–Cr–Ni–Mo diffusion barrier layer and an Al reservoir layer.     

The influence of the transformation of electronic structure and micro-structure on improving the thermoelectric properties of zinc antimonide thin films

Measurements of electronic structure, microstructure and thermoelectric properties of zinc antimonide thin films prepared by direct current magnetron co-sputtering were carried out. The as-deposited zinc antimonide thin film had a very high resistivity similar to insulating ceramics, which was due to a low binding energy of both zinc and antimony, with the electron scattering increases and impedes the current transport. With the increase in annealing temperature, the films became more crystalline and the thermoelectric properties were also improved. The resistivity of the film decreased rapidly with its crystallinity when the annealing temperature was above 350 °C. The Seebeck coefficients of the thin films were positive, indicating that the films were P-type. The Seebeck coefficient of those samples increased with increasing annealing temperature. The thin film annealed at 400 °C has an optimal power factor of 1.87 × 10⁻³ Wm⁻¹ K⁻² with a Seebeck coefficient of 300 μVK⁻¹ and a resistivity of 4.82 × 10⁻⁵ Ωm at 573 K.     

Thermal stability under air of tungsten–titanium diffusion barrier layer between silica and platinum

The present work investigated the thermal stability of tungsten–titanium diffusion barrier layers intercalated between SiO₂ substrate and platinum thin film. The resulting structures were annealed under air in the temperature range 400–600 °C for annealing times up to 100 h. Chemical and structural characterizations at different stages of the treatment evidenced several phenomena occurring during annealing under air, especially the complete oxidation of the adhesive layer, the diffusion of tungsten oxide through platinum film at particle boundaries as well as the sublimation process of tungsten oxide. The results of film surface chemistry and microstructure were correlated with diffusion phenomena.     

Effects of the lanthanum content on the microstructure and properties of the molybdenum alloy

The effects of the lanthanum content on the microstructure and properties of molybdenum alloy were investigated. The molybdenum powders with various lanthanum contents were prepared by a solid-liquid doping method and reduction under hydrogen atmosphere, which could be processed into sintered molybdenum and rotary swaged molybdenum. The results indicated that the grain sizes of the alloys became finer and the tensile strength increased with increasing La content. The La₂O₃ particles could adsorb impurity elements that existed on the grain boundary and generate the amorphous structure around the particle. The rotary swaged Mo with 0.1 wt.% La was the highest tensile strength, and the rotary swaged Mo with 0.03 wt.% La possessed the highest elongation to failure of 42%. In addition, the electrical resistivity of the rotary swaged Mo increased at first and later decreased with increasing La content.     

SiO 2基底上化学镀Ni-Mo-P薄膜的生长和形成机理

采用化学镀方法在SiO2/Si 基底上制备Cu互联线用阻挡层材料Ni-Mo-P薄膜。采用场发射扫描电子显微镜、电子分散能谱仪、原子力显微镜分析不同沉积时间样品的表面形貌和成分,并对Ni-Mo-P薄膜的形成过程进行研究。Ni-Mo-P薄膜的形成过程分为3个阶段：催化阶段,先前还原的Pd颗粒成为Ni还原的催化形核中心,诱导Ni沉积;覆盖阶段,Ni颗粒诱导Mo、P与之进行共沉积;自生长阶段,Ni-Mo-P薄膜共同沉积,颗粒生长。阐述了还原剂被氧化后产物为3-4PO 的的反应机理。     

Electrodeposition of CoMoP thin film as diffusion barrier layer for ULSI applications

CoMoP thin films were fabricated by electrodeposition technique from citrate based bath onto Cu sheets for the application as diffusion barriers and metal capping layers in the copper interconnect technology. The study focused on the effect of (NH₄)₆Mo₇O₂₄·4H₂O concentrations in the plating solution on the plating rate and chemical composition of the deposited layer. It was found that the Mo wt.% in the deposited layer increased from 13 to 22 wt.% with increasing (NH₄)₆Mo₇O₂₄·4H₂O concentration. The influence of deposition current density, solution pH and deposition temperature at certain (NH₄)₆Mo₇O₂₄·4H₂O concentration in the plating bath on the plating rate and chemical composition was studied. Polarization behavior of induced co-deposition of CoMoP at various electrolyte pH values was studied using cyclic voltammetry and chronoamperometry to estimate the current efficiency (CE%) of the plating solutions and the optimum pH for the plating process. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques have been applied to characterize the morphology and chemical composition of the deposited layer. CoMoP alloys of high P wt.% as-deposited films showed irregular microcracks amorphous structure and of low P wt.% showed amorphous/nanocrystalline structure while, after annealing at 400 °C for 1 h, the films deposited with low and high P wt.% converted into polycrystalline structure. The results of oxidation property showed that, the Co-13.2 wt.% Mo-10.3 wt.% P alloy has highest stability against oxidation and lowest electrical resistance values (100-150 µΩ). The ferromagnetism nature of coated materials has been studied by hysteresis loop measurements. The electrochemical corrosion results were calculated from polarization studies for as-plated and annealed CoMoP coatings in 3.5% NaCl solution.     

Evaluation of the properties of anodized aluminum 6061 subjected to thermal cycling treatment using electrochemical impedance spectroscopy (EIS)

The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated for 30 days during exposure to 3.5 wt% NaCl using EIS. Thermal cycling treatments at 120, 160 and 200 °C have been applied for the two types of samples. The degradation of the properties of the anodized layers has been determined by thorough analysis of the EIS data for control samples and samples that had undergone thermal cycling. Scanning electron microscopy has been used to evaluate the damage to the anodized aluminum layers due to thermal cycling. It was found that the thermal treatment produced considerable damage of both the porous layer and the barrier layer. The EIS data suggest that some cracks extended into the bare metal. The damage of the oxide layers increased with increasing thermal cycling temperature for both types of samples. Self-sealing of the porous layer and the barrier layer occurred during immersion in NaCl.     

The role of Mg2Si formation in the hydrogenation of Mg film and Mg nanoblade array on Si substrates

In this paper, both an Mg film and an Mg nanoblade array have been first fabricated directly on Si substrates and hydrogenated under 20 bar hydrogen pressure at temperatures ranging from 200 °C to 350 °C. It is found that Mg₂Si alloy starts to form at T = 200 °C in both the Mg samples, which produces a two-layered structure in the hydrogenated films with the bottom dense layer of Mg₂Si. To prevent Mg alloying with Si, a layer of 200 nm thick Ti film was deposited in between the Mg samples and Si substrates as a diffusion barrier, and their hydrogenation results show that Mg₂Si formation is suppressed greatly and even eliminated in nanoblades, though Mg₂Si hillock defects are observed in the hydrogenated films, which could be formed progressively through the pinholes in the Ti film. To improve the diffusion barrier, a unique structure, consisting of layers of Ti nanorod array and Ti film, has been designed for Mg-based nanostructure deposition. The hydrogen cycling study demonstrates that the structure of 450 nm Ti nanorods on 1 μm Ti film can endure enough number of cycles for the hydrogen storage kinetic and thermodynamic study of film-based Mg nanostructures with/without nanocatalyst, and thus one can gain a fundamental understanding of hydrogen interacting with Mg intrinsic nanostructures and nanocatalysts.     

Thermal properties of MoSi2 with minor aluminum substitutions

Mo(Si_1−xAl_x)₂ compositions (x = 0–0.1) have been prepared by a modified SHS route under uniaxial hydrostatic pressure. Oxidation studies carried out by thermal analysis and sheet resistivity indicate an improvement in the low temperature (700–900 K) oxidation resistance with increasing aluminum addition. Dilatometric results show a decrease in the α value up to x = 0.05 substitution. With the aluminum substitution, both thermal expansion coefficient and thermal conductivity show decrease in their values except in the biphasic region. The x = 0.05 composition containing both C11_b and C40 phases is a promising material for high temperature thermal barrier coating as it shows higher oxidation resistance and a similar K/α value as compared to pure MoSi₂.     

Formation and thermal stability of amorphous Ni-Mo-P alloys

The experimental researches on the chemical deposition of Ni-Mo-P amorphous alloys were carried out by adding Na2 MoO4 into acidic solutions. The optimum technology conditions were obtained by orthogonal design experiments. The structures and the relationship between compositions and their thermal stability were studied by energy spectrum (EC), scanning electron micrograph and X-ray diffraction spectrum. Compared with Ni-P amorphous alloys, the Ni-Mo-P amorphous alloys have high crystallization temperature and thermal stability, and the hardness reaches its peak when the annealing temperature is 500 ℃. With the increase of the heat treatment temperature, the surface morphology of the alloys changes.