Effect of high temperature annealing on the electrical performance of titanium/platinum thin films

In this study, the influence of post deposition annealing steps (PDA) on the electrical resistivity of evaporated titanium/platinum thin films on thermally oxidised silicon is investigated. Varying parameters are the impact of thermal loading with maximum temperatures up to T_PDA = 700 °C and the platinum top layer thickness ranging from 24 nm to 105 nm. The titanium based adhesive film thickness is fixed to 10 nm. Up to post deposition annealing temperatures of T_PDA = 450 °C, the film resistivity is linearly correlated with the reciprocal value of the platinum film thickness according to the size effect. Modifications in the intrinsic film stress strongly influence the electrical material parameter in this temperature regime. At T_PDA > 600 °C, diffusion of titanium into the platinum top layer and its plastic deformation dominate the electrical behaviour, both causing an increase in film resistivity above average.     

Electrical properties of thin metal zinc films

Thin metal zinc films 40 to 200 nm thick are deposited by thermal evaporation at room temperature onto glass substrates with a deposition rate of 0.2 to 0.7 nm sec^–1. The electrical resistivity is measured as a function of film thickness, deposition rate and annealing temperature. The experimental results show that electrical resistivity decreases as the film thickness, deposition rate and annealing temperature increase, while the temperature coefficient of resistivity increases with the increase in the film thickness. The calculated values of the activation energy for the conduction electrons increases as the film thickness and deposition rate increase. The well known Fuchs-Sondheimer model is applied for zinc films. The theoretically calculated values for the electrical resistivity and the temperature coefficient of resistivity are in good agreement with the experimental results.     

The electrical resistivity and resistance-temperature characteristics of thin titanium films

In this communication are described the results on the electrical resistivity and resistance-temperature characteristics of titanium films, measured in vacuum. They were evaporated onto soda glass microscope slides at room temperature in a sputter-ion pumped glass belljar vacuum system at about 5×10^-8 torr. The films varied in their thickness from 50 to 1100 Å, and the resistivity was very high for the thinnest films but for the thickest ones it approached approximately double the bulk value. The measured resistivities for the continuous freshly prepared films are too high to be explained on the basis of the Fuchs-Sondheimer theory^{1, 2} for diffuse scattering, and are attributed to porosity and the gaseous impurities taken down during and after their formation. The temperature coefficient of resistance (TCR) was negative for films less than 50–60 Å thick but positive for thicker ones. A bulk mean free path of 285 Å in titanium was calculated at room temperature.     

Oxidation of thin titamium films in ambient conditions

The room temperature oxidation of vapor-deposited titanium films was investigated as a function of film thickness by resistivity and ellipsometric measurements. The thickness of the films ranged from 3.0 to 120 nm. The electron mean free path in the films varied from 11.3 to 26.0 nm, and the product of the bulk resistivity and the electron mean free path was 1.5 × 10^-10Ω cm². The values of the surface electron scattering parameter in the films were between 0.2 and 0.6 and decreased to 0.18 at the onset of oxidation. The best value for the complex refractive index of titanium was found to be 3.61-i4.06. The refractive index of the oxide film was 2.75. After a 1 d exposure of the films to room air at atmospheric pressure both the resistance and ellipsometric measurements indicated a residual oxide thickness of 2.6±0.3 nm, regardless of the original metal film thickness. These results disagree with the theoretical and experimental results of Mindel and Pollack, which implied a rapid decrease in oxide thickness with decreasing titanium film thickness.     

Structural and electrical properties of RuO2 thin films prepared by rf-magnetron sputtering and annealing at different temperatures

Conductive ruthenium oxide (RuO₂) thin films have been deposited at different substrate temperatures on various substrates by radio-frequency (rf) magnetron sputtering and were later annealed at different temperatures. The thickness of the films ranges from 50 to 700 nm. Films deposited at higher temperatures show larger grain size (about 140 nm) with (200) preferred orientation. Films deposited at lower substrate temperature have smaller grains (about 55 nm) with (110) preferred orientation. The electrical resistivity decreases slightly with increasing film thickness but is more influenced by the deposition and annealing temperature. Maximum resistivity is 861 μΩ cm, observed for films deposited at room temperature on glass substrates. Minimum resistivity is 40 μΩ cm observed for a thin film (50 nm) deposited at 540°C on a quartz substrate. Micro-Raman investigations indicate that strain-free well-crystallized thin films are deposited on oxidized Si substrates.     

H-assisted plasma CVD of Cu films for interconnects in ultra-large-scale integration

H-assisted plasma CVD (HAPCVD), in which Cu(hfac)₂ is supplied as the source material, realizes control of qualities of Cu films, since H irradiation is effective in purifying the Cu films, increasing the grain size, and reducing the surface roughness. Conformal deposition in fine trenches can be realized by decreasing dissociation degree of Cu(hfac)₂ using the HAPCVD. Cu(hfac) is identified as the radical mainly contributing to the deposition. Based on the results, we proposed a model in which Cu(hfac) and H react on surfaces to deposit Cu films. We also demonstrated conformal deposition of smooth Cu films of 30 nm thickness and 1.9 μΩ cm resistivity and almost complete Cu filling in trenches 0.35 μm wide and 1.6 μm deep using the HAPCVD.     

Comparative study of resistivity characteristics between transparent conducting AZO and GZO thin films for use at high temperatures

This paper compares in detail the resistivity behavior of transparent conducting Al-doped and Ga-doped ZnO (AZO and GZO) thin films for use in an air environment at high temperatures. AZO and GZO thin films with thicknesses in the range from approximately 30 to 100 nm were prepared on glass substrates at a temperature of 200 °C by rf superimposed dc or conventional dc magnetron sputtering deposition, pulsed laser deposition or vacuum arc plasma evaporation techniques. In heat-resistance tests, the resistivity was measured both before and after heat tests for 30 min in air at a temperature up to 400 °C. The resistivity stability of AZO thin films was found to be always lower than that of GZO thin films prepared with the same thickness under the same deposition conditions, regardless of the deposition technique. However, the resistivity of all AZO and GZO thin films prepared with a thickness above approximately 100 nm was stable when heat tested at a temperature up to approximately 250 °C. It was found that the resistivity stability in both GZO and AZO thin films is dominated by different mechanisms determined by whether the thickness is below or above approximately 50 nm. With thicknesses above approximately 100 nm, the increase in resistivity found in GZO and AZO films after heat testing at a temperature up to 400 °C exhibited different characteristics that resulted from a variation in the behavior of Hall mobility.     

The effect of substrate temperature,deposition rate and annealing on the electrical resistivity of thin yttrium films

The effect of substrate temperature, deposition rate and annealing on the electrical resistivity of thin yttrium films in the thickness range 10 to 80 nm is reported. The resistivity of films decreases at higher deposition rates and substrate temperatures. These experimental results are analysed using the Fuchs—Sondheimer and Mayadas—Shatzkes theories. The annealing behaviour of yttrium films is in agreement with the Vand theory.     

Electrical conduction and transmission electron microscopy studies of CdSe0.8Te0.2 thin films

Electrical resistance of CdSe_0.8Te_0.2 thin films were found to be dependent on various film parameters such as substrate temperature, film thickness, deposition rate and post-deposition heat treatment in different environments. A decrease in film resistivity was observed for thicker films and for those heat treated in vacuum. Films deposited at higher substrate temperatures and faster rates showed an increase in film resistivity. A spectrum of activation energies was observed in the films which fell within either of the activation energies observed in CdSe or CdTe films. Films heated in an oxygen environment showed an increase in film resistivity with a different activation energy. Transmission electron microscopy (TEM) of the films showed an improvement in crystallinity with increasing film thickness and substrate temperature, and a reduction in crystallinity with increasing deposition rate.     

Preparation and study of thickness dependent electrical characteristics of zinc sulfide thin films

Zinc sulfide thin films have been deposited onto glass substrates by chemical bath deposition. The various deposition parameters such as volume of sulfide ion source, pH of bath, deposition time, temperature etc are optimized. Thin films of ZnS with different thicknesses of 76–332 nm were prepared by changing the deposition time from 6–20 h at 30° C temperature. The effect of film thickness on structural and electrical properties was studied. The electrical resistivity was decreased from 1.83 × 10⁵ Ω-cm to 0.363 × 10⁵ Ω-cm as film thickness decreased from 332 nm to 76 nm. The structural and activation energy studies support this decrease in the resistivity due to improvement in crystallinity of the films which would increase the charge carrier mobility and decrease in defect levels with increase in the thickness.     

Resistivity and structure of evaporated polycrystalline molybdenum films

Molybdenum films of thickness 20–2600 nm were evaporated at a substrate temperature of 650°C and were then vacuum annealed at 900°C. The mean grain size of films increased with increasing thickness and it became saturated at about 130 nm for films thicker than 1000 nm. Using this result, the Mayadas-Shatzkes model of grain boundary scattering was used for the interpretation of the observed thickness dependence of the resistivity of the films. Values of the grain boundary electron reflection coefficient, which increase with decreasing film thickness, were used to fit the experimental data to theoretical curves.     

Very thin poly-SiC films for micro/nano devices

We report characterization of nitrogen-doped, very thin, low-stress polycrystalline silicon carbide (poly-SiC) films suitable for fabricating micro/nano devices. The poly-SiC films are deposited on 100 mm-diameter (100) silicon wafers in a large-scale, hot-wall, horizontal LPCVD furnace using SiH2Cl2 and C2H2 as precursors and NH, as doping gas. The deposition temperature and pressure are fixed at 900 degrees C and 4 Torr, respectively. The deposition rate increases substantially in the first 50 minutes, transitioning to a limiting value thereafter. The deposited films exhibit (111)-orientated polycrystalline 3C-SiC texture. HR-TEM indicates a 1 nm to 4 nm amorphous SiC layer at the SiC/silicon interface. The residual stress and the resistivity of the films are found to be thickness dependent in the range of 100 nm to 1 microm. Films with thickness less than 100 nm suffer from voids or pinholes. Films thicker than 100 nm are shown to be suitable for fabricating micro/nano devices.     

Preparation of regularly structured nanotubular TiO2 thin films on ITO and their modification with thin ALD-grown layers

Nanotubular titanium dioxide thin films were prepared by anodization of titanium metal films evaporated on indium tin oxide (ITO) coated glass. A facile method to enhance the adhesion of the titanium film to the ITO glass was developed. An optimum thickness of 550 nm for the evaporated titanium was found to keep the film adhered to ITO during the anodization. The films were further modified by growing amorphous titania, alumina and tantala thin films conformally in the nanotubes by atomic layer deposition (ALD). The optical, electrical and physical properties of the different structures were compared. It was shown that even 5 nm thin layers can modify the properties of the nanotubular titanium dioxide films.     

Stability of nano-thick transparent conducting oxide films for use in a moist environment

The stability of nano-thick transparent conducting oxide thin films in a high humidity environment was investigated. The stability of ITO and impurity-doped ZnO thin films prepared with a thickness in the range from approximately 20 to 100 nm on glass substrates at a temperature below 200 °C by a pulsed laser deposition was evaluated in air at a relative humidity of 90% and a temperature of 60 °C. The resistivity of all Al- and Ga-doped ZnO thin films tested was found to increase markedly with test time, whereas that of ITO remained relatively stable; the stability (resistivity increase) of the doped ZnO thin films was considerably affected by film thickness but was relatively independent of the deposition substrate temperature. In particular, doped ZnO thin films with a thickness below approximately 50 nm were very unstable under the test conditions. The resistivity increase of doped ZnO films is mainly attributed to the grain boundary scattering resulting from the adsorption of oxygen on the grain boundary.     

Ru thin film grown on TaN by plasma enhanced atomic layer deposition

Ru thin films were sequentially deposited onto TaN (5 nm) by plasma enhanced atomic layer deposition using Ru(EtCp)₂ and NH₃ as precursors. The effect of growth temperature on the electrical resistivity and morphology of the Ru films were studied. It was found that the Ru films can achieve a low resistivity of 14 µΩ cm and a low root-mean-square roughness at a growth temperature of 270 °C. The thickness of the underlying TaN film was found to affect the Ru film growth. The oxidation of the very thin TaN film was correlated with the island growth of Ru. Ex and in-situ X-ray diffraction was employed to verify the copper diffusion barrier properties of a Ru (3 nm)/TaN (5 nm) bi-layer structure.     

Properties of Reactive Magnetron Sputtered ITO Films without in-situ Substrate Heating and Post-deposition Annealing

1. Introductiontransparent conductive indium tin oxide (ITO)films have been extensively used in a variety of electronic and opto--electronic applications because oftheir high transmission in the visible range, high infrared (IR) reflection, and low electrical resistivity.A variety of deposition techniques have been appliedto fabricate ITO films such as CVD, spray pyrolysisand sputteringll'2]. However, sputtering is the mostextensively used technique especially in industry. Recelltly, targe…     

Effect of spatial relationship between arc plasma and substrate on the properties of transparent conducting Ga-doped ZnO thin films prepared by vacuum arc plasma evaporation

The effect of the spatial relationship between the arc plasma flow and the substrate surface on the resulting film thickness and electrical properties is investigated in transparent conducting Ga-doped ZnO (GZO) thin films deposited by a vacuum arc plasma evaporation (VAPE) method. It was found that the resulting electrical properties of GZO thin films produced by a VAPE deposition on a fixed substrate were considerably dependent on both the film thickness and the location on the substrate surface, extending from the area nearest the arc plasma source to that at the opposite end of the substrate in a direction parallel to the arc plasma flow; with GZO thin films deposited with various thicknesses in the range from 20 to 200 nm, the films exhibited a thickness dependence of resistivity that was considerably affected by the location on the substrate surface. The variation of resistivity relative to the location on the substrate surface was related to that of carrier concentration, which is mainly attributed to the distribution of the amount of oxygen reaching the substrate surface. In GZO thin films deposited with a thickness of 30-40 nm at a substrate temperature of 250 °C, a resistivity as low as 4 × 10^− 4 Ω cm was obtained in the area of the substrate nearest the arc plasma source.     

Effect of deposition process parameters on resistivity of metal and alloy films deposited using anodic vacuum arc technique

Thin solid films of copper, aluminum and nichrome have been deposited on glass substrates with thickness ranging from 20 nm to 200 nm, using the anodic vacuum arc deposition technique. Electrical resistivity and average grain size of deposited thin films have been measured and their dependence on the deposition process parameters has been investigated. Thickness dependence of resistivity has also been compared with numerically generated results using Fuchs-Sondheimer theory and Mayadas-Shatzkes theory which has been found to be in good agreement for film thickness greater than 80 nm. The resistivity values of Cu, Al and NiCr has been found to take a minimum value (approaching that of corresponding bulk material) of 80 A arc current and a substrate bias of around − 50 V.     

Electrical resistivity of Ti-Zn mixed oxide thin films deposited by atomic layer deposition

Ti-Zn mixed oxide thin films, with thickness less than 50 nm, were grown with atomic layer deposition (ALD) technique at low temperature (90 °C) varying the composition. ALD is a powerful chemical technique to deposit thin films with thickness of few atomic layers. ALD oxide material growth is achieved by dosing sequentially the metal precursor and the oxidizing agent. Thanks to ALD nature of layer by layer growth it was possible to realize mixed metal, Ti and Zn, oxide thin films with controlled composition, simply by changing the number of cycles of each metal oxide layer. Structural and electrical properties of the prepared thin films were studied as a function of their composition. Synchrotron radiation X-ray diffraction technique was used to follow thin film crystallization during sample annealing, performed in situ. It was observed that the onset temperature of crystallization raises with Ti content, and sample structure was Zn₂TiO4 phase. Electrical resistivity measurements were performed on crystalline samples, annealed at 600 °C, revealing an increase in resistivity with Ti content.     

Lattice distortion energy spectra of thin evaporated silver films

Thin silver films (thickness, 12.5–160 nm) were evaporated under ultrahigh vacuum conditions onto clean glass substrates (substrate temperature, 225 K). During the growth process a large number of lattice defects were incorporated (condensation rate, 0.2 and 0.01 nm s^-1). The films were subjected to heat treatment (constant heating rate, 0.1 K s^-1) and the variation in the electrical resistance was measured as a function of temperature. Using Vand's theory the initial lattice distortion energy spectra of the films were determined from the resistance-temperature data. The lattice distortion energy function has maximum values. While the number of distortions with a decay energy of about 0.8 eV increases rapidly with decreasing film thickness, the number of distortions with a decay energy of about 0.93 eV varies only slightly.