Fabrication of low-resistivity and gold-colored TiN films by halide chemical vapor deposition with a low [NH3]/[TiCl4] flow ratio

This work describes the preparation of titanium nitride (TiN) films on Si (111) substrates by atmospheric pressure halide chemical vapor deposition (AP-HCVD). Various TiN films were obtained by exploiting TiCl₄ + NH₃ gas chemistry with flow ratios [NH₃]/[TiCl₄] from 0.2 to 1.4, and deposition temperatures (T_d) from 600 to 900 °C. When T_d = 800 °C gold-colored films with electrical resistivities of under 100 μΩ cm were formed at almost all of the investigated [NH₃]/[TiCl₄] flow ratios. In particular, a lowest resistivity of about 23.7 μΩ cm, which is quite close to that of bulk TiN, was achieved using an [NH₃]/[TiCl₄] flow ratio of 0.3. Atomic force microscopy indicated that the root mean square surface roughness of that film was only about 5.1 nm. Under the same [NH₃]/[TiCl₄] flow ratio as above, X-ray diffraction analyses revealed the presence of a cubic TiN phase with a preferred orientation of (200) for T_d ≤ 800 °C, while additional (111) and (220) orientations emerged when the film was deposited at 900 °C. In conclusion, a low resistivity (< 100 μΩ cm) TiN film can be formed by AP-HCVD with very low [NH₃]/[TiCl₄] flow ratios 0.3-1.4.     

Influence of magnetic annealing on high-frequency magnetic properties of FeCoNd films

FeCoNd thin film with thickness of 166 nm has been fabricated on silicon (1 1 1) substrates by magnetron co-sputtering and annealed for one hour under magnetic field at different temperatures (T_a) from 200 °C to 700 °C. The As-deposited and annealed FeCoNd film samples at T_a ≤ 500 °C were amorphous while the ones obtained at T_a ≥ 600 °C were crystallized. We found that the perpendicular anisotropy field gradually decreases as the annealing temperature increases from room temperature to 300 °C. A well induced in-plane uniaxial anisotropy is achieved at the annealing temperature between 400 and 600 °C. The variation of the dynamic magnetic properties of annealed FeCoNd films can be well explained by the Landau-Lifshitz equation with the variation of the anisotropy field re-distribution and the damping constant upon magnetic annealing. The magnetic annealing might be a powerful post treatment method for high frequency application of magnetic thin films.     

Temperature effect on structure and surface morphology of indium tin oxide films deposited by reactive ion-beam sputtering

Indium tin oxide (ITO) films were deposited by reactive ion-beam sputtering. The relationship among the surface morphology, the resistivity ρ of the films, the substrate temperature T_S and the film thickness t_F was investigated. The heat power from the ion source during the sputtering was 265 W. T_S increased from 30 to 145 °C with an increase of t_F. The films thinner than 187 nm at T_S lower than 120 °C were amorphous, the film surface was as smooth as the substrate. The films deposited at T_S in the range between 135 and 145 °C were polycrystalline. So, the films thicker than 375 nm were in a multilayer structure of a polycrystalline layer on an amorphous layer. The surface of the polycrystalline films became rough. ρ of the films suddenly decreased at t_F of 375 nm, where the structure of the films changed. Next, the amorphous films with t_F of 39 nm were annealed in the atmosphere. The film structure changed to a polycrystalline structure at annealing temperature T_A of 350 °C. However, the surface roughness of all the films was almost same. As a result, the substrate temperature during the sputtering was important for the deposition of the films with a very smooth surface.     

Deposition of WNxCy thin films for diffusion barrier application using the dimethylhydrazido (2) tungsten complex (CH3CN)Cl4W(NNMe2)

Tungsten nitride carbide (WN_xC_y) thin films were deposited by chemical vapor deposition using the dimethylhydrazido (2⁻) tungsten complex (CH₃CN)Cl₄W(NNMe₂) (1) in benzonitrile with H₂ as a co-reactant in the temperature range 300 to 700 °C. Films were characterized using X-ray diffraction (XRD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy and four-point probe to determine film crystallinity, composition, atomic bonding, and electrical resistivity, respectively. The lowest temperature at which growth was observed from 1 was 300 °C. For deposition between 300 and 650 °C, AES measurements indicated the presence of W, C, N, and O in the deposited film. The films deposited below 550 °C were amorphous, while those deposited at and above 550 °C were nano-crystalline (average grain size < 70 Å). The films exhibited their lowest resistivity of 840 µΩ-cm for deposition at 300 °C. WN_xC_y films were tested for diffusion barrier quality by sputter coating the film with Cu, annealing the Cu/WN_xC_y/Si stack in vacuum, and performing AES depth profile and XRD measurement to detect evidence of copper diffusion. Films deposited at 350 and 400 °C (50 and 60 nm thickness, respectively) were able to prevent bulk Cu transport after vacuum annealing at 500 °C for 30 min.     

Post deposition annealing temperature effect on silicon quantum dots embedded in silicon nitride dielectric multilayer prepared by hot-wire chemical vapor deposition

The preparations of the 20-period of a Si quantum dot (QD)/SiN_x multilayer in a hot-wire chemical vapor deposition (HWCVD) chamber is presented in this paper. The changes in the properties of Si-QDs after the post deposition annealing treatment are studied in detail. Alternate a-Si:H and SiN_x layers are grown in a single SiN_x deposition chamber by cracking SiH₄, and SiH₄ + NH₃, respectively at 250 °C. The as-deposited samples are annealed in the temperature range of 800 °C to 950 °C to grow Si-QDs. All the samples are characterized by confocal micro Raman, transmission electron microscope (TEM), and photoluminescence (PL) to study the changes in the film structures after the annealing treatment. The micro Raman analysis of the samples shows the frequency line shifting from 482 cm^− 1 to 500 cm^− 1 indicating the Si transition from an amorphous to a crystalline phase. The TEM micrograph inspection indicates the formation of Si-QDs of size 3 to 5 nm and a density of 5 × 10¹²/cm². The high resolution TEM micrographs show an agglomeration of Si-QDs with an increase in the annealing temperature. The PL spectra show a peak shifting from 459 nm to 532 nm with increasing the annealing temperature of the film.     

Grazing incidence X-ray study of Ge-nanoparticle formation in (Ge:SiO2)/SiO2 multilayers

We present the study of formation of Ge-nanoparticles (Ge-NP) in germanosilicate (Ge:SiO₂) multilayer (ML) films under thermal treatment. In anticipation of controllable formation of Ge-NP, ML films were prepared by magnetron deposition at room temperature as 20 bi-layer stacks, each bi-layer comprised of a 7 nm thick layer of (Ge + SiO₂) (molar ratio: 60:40) succeeded by a 7 nm thick layer of pure SiO₂, and then annealed for 1 h, up to T_a = 900 °C. Formation and morphology of Ge-NP were analyzed by combining the information obtained from the grazing incidence small angle X-ray scattering and X-ray diffraction. It was found that precipitation of Ge-NP starts at T_a = 600 °C, while high degree of in-plane confinement and lateral ordering of rather uniform precipitated particles is achieved at T_a =  700-800 °C range. At still higher annealing temperature T_a > 800 °C, volume fraction of precipitated Ge-NP in SiO₂ matrix diminishes due to the out-diffusion of Ge atoms from the film, while Ge-NP are no more well confined to (Ge + SiO₂) layers.     

Characteristics of high-k gate oxide prepared by oxidation of multi-layered Hf/Zr/Hf/Zr/Hf metal films

We investigated the physical and electrical properties of Hf-Zr mixed high-k oxide films obtained by the oxidation and annealing of multi-layered metal films (i.e., Hf/Zr/Hf/Zr/Hf, ∼ 5 nm). We demonstrated that the oxidation of multi-layered metal films results in two distinctive amorphous layers: That is, Hf-Zr mixed oxide film was formed on the top of silicate film due to inter-diffusion between Hf and Zr layer. This film shows the improved dielectric constant (k) and the raised crystallization temperature. Compared with HfO₂ and ZrO₂ gate dielectric, the crystallization temperature of Hf-Zr mixed oxides was raised by more than 200 °C. Using AES and XPS, we observed that Zr oxide has more fully oxidized stoichiometry than Hf oxide, irrespective of annealing temperatures. We also found that the thickness of an interfacial layer located between Hf-Zr mixed oxide and Si substrate also increases as annealing temperature increases. Especially, the thin SiO_x interfacial layer starts to form if annealing temperature increases over 700 °C, deteriorating the equivalent oxide thickness.     

Heat treatment effects on the formation of lanthanum-modified lead zirconate titanate thin films

The microstructural and compositional properties of lanthanum-modified lead zirconate titanate (PLZT) thin films deposited on platinum coated Si substrates by RF magnetron sputtering have been studied. The heat treatment processes of substrate heating during deposition and post deposition furnace and rapid thermal annealing were compared as processes for obtaining the desired pervoskite phase. PLZT thin films deposited with in-situ substrate heating showed little evidence of micro-cracking. The XRD data obtained showed the formation of pervoskite phase at 550 °C and indicated the suppression of the pyrochlore phase for increasing temperatures. The RBS analysis revealed a film thickness of 140 nm and composition of (Pb_0.91La_0.09)(Zr_0.6Ti_0.4)O₃. Deposition performed with in-situ substrate heating at 650 °C resulted in highly (110) pervoskite orientated thin films with an average grain size around 160 to 200 nm and an RMS roughness of 3 nm.     

Optical recording characteristics of molybdenum oxide films prepared by pulsed laser deposition method

Molybdenum-oxide (MoO₃)films were deposited on glass substrates (Corning #7059 with an area of 26 × 38 mm²) by pulsed laser deposition using an ArF excimer laser. It was found that after annealing at 340 °C for 10 min, the film thickness became 2.3 times that (approximately 30 nm) of the as-deposited film thickness. The difference in the transmittance, ΔT, between the annealed state and the as-deposited state was about 40% at a wavelength of 400 nm. X-ray diffraction spectra indicated that oxygen was absorbed into the MoO₃ films through the annealing process. From revolution testing of 30 nm-thick MoO₃ films without a protective layer deposited on a polycarbonate DVD-R disk substrate (120 mm?, 0.6 mm thickness), a write peak-power dependence of carrier-to-noise ratio (CNR) (recording on-land, at λ = 406 nm, NA = 0.65) of the 3T signal (58.5 MHz) was measured at a linear velocity of 5 m/s and a read power of 0.6 mW. Consequently, CNR near 50dB was obtained in the wide write-power margin ΔP of 7 mW (at peak powers between 3.5 and 10.5 mW). From SEM observations, it was recognized that bits of 0.25-0.30 μm size, corresponding to a storage capacity of 7-10GB/in² in the case of NA = 0.65, were formed. For the sample structure with an Al₂O₃ protective layer of ~ 20 nm thickness, a CNR near 50dB was obtained in the peak-power margin ΔP of 12 mW (at peak powers between 6.0 and 18.0 mW). Larger values of the CNR can be obtained if the film thickness of each layer including both the active and protective layers is optimized.     

The structure of Ta nanopillars grown by glancing angle deposition

Regular arrays of Ta nanopillars, 200 nm wide and 500 nm tall, were grown on SiO₂ nanosphere patterns by glancing angle sputter deposition (GLAD). Plan-view and cross-sectional scanning electron microscopy analyses show dramatic changes in the structure and morphology of individual nanopillars as a function of growth temperature T_s ranging from 200 to 700 °C. At low temperatures, T_s ≤ 300 °C, single nanopillars develop on each sphere and branch into subpillars near the pillar top. In contrast, T_s ≥ 500 °C leads to branching during the nucleation stage at the pillar bottom. The top branching at low T_s is associated with surface mounds on a growing pillar that, due to atomic shadowing, develop into separated subpillars. At high T_s, the branching occurs during the nucleation stage where multiple nuclei on a single SiO₂ sphere develop into subpillars during a competitive growth mode which, in turn, leads to intercolumnar competition and the extinction of some nanopillars.     

Reversibility of silicidation of Ta filaments in HWCVD of thin film silicon

If tantalum filaments are used for the hot wire chemical vapour deposition (HWCVD) of thin film silicon, various types of tantalum silicides are formed, depending on the filament temperature.Under deposition conditions employed for device quality amorphous and microcrystalline silicon (T_wire ≈ 1750 °C) a Ta₅Si₃ (as determined by XRD) shell is formed around the Ta core. After 8 h of accumulated deposition time this shell has a thickness of around 20 μm. Upon annealing of the filament in vacuum at 2100-2200 °C the tantalum silicide shell becomes thinner, while a Ta layer is reappearing at the surface of the wire. After 4 h of annealing the silicide is completely removed, whereas the total diameter of the wire has not significantly changed. The resistance of the filament has been monitored and after the annealing procedure, it completely recovered to that of a fresh wire. This regeneration procedure greatly helps to avoid frequent replacement of the filaments.     

Modification of AZO thin-film properties by annealing and ion etching

Effects of annealing and ion etching on the structural, electrical and optical properties of sputtered ZnO:Al (AZO) thin films were investigated. The post-deposition annealing at temperatures T_A = 200-400 °C in the forming gas (80% N₂/20% H₂) for 1 h and ion RF-sputter etching after annealing were used. Ion-sputter etching rate was 7 nm/min. The surface topography changed noticeably after ion-sputter etching: the surface of the sample was rougher (R_a = 33 nm) in comparison with annealed sample only (R_a = 9 nm). After the post-deposition annealing temperature T_A = 400 °C and ion-sputter etching thin films have higher integral transmittance (in the range of λ = 400-1000 nm) than non-etched samples. The figure of merit (F) became higher with increase of annealing temperature and the maximum value was F = 8%/Ω at T_A = 400 °C (R_s = 10 Ω, T_int = 86%).     

Effect of structural transformation on the electrical properties for Ge1Sb2Te4 thin film

Dependence of electrical properties of phase change Ge₁Sb₂Te₄ thin film on structural transformation was investigated. The electrical resistivity of the film decreases with increasing annealing temperature with a steep drop at ∼ 230 °C (the second crystallization temperature), at which the structure of Ge₁Sb₂Te₄ changes from face-centered cubic to trigonal state. The steep drop of resistivity at the second crystallization temperature is mainly due to the increase of hole density within the p-type film, according to Hall measurement. The crystallization process has been followed by in situ resistance measurement at various annealing temperatures. Transmission electron microscope and atomic force microscope were also employed to study the film.     

The electrical and optical properties of indium zinc tin oxide thin films with different Sn/Zn ratio

Indium zinc tin oxide (IZTO) thin films with two different chemical compositions, i.e. IZTO15 and IZTO25, where In content was fixed at 60 at.% and Sn content was 15 and 25 at.%, respectively, were deposited onto alkaline-free glass substrate at temperature from 37 °C to 600 °C. The deposition process was carried out in argon using an RF magnetron sputter. After deposition, the films were annealed in argon atmosphere at 450 °C for 30 min. The effect of substrate temperature and annealing treatment was investigated, and the minimum resistivity value of 3.44 × 10^− 4Ω.cm was obtained from the film deposited at 400 °C using IZTO25 target followed by rapid thermal annealing at 450 °C for 30 min. The average optical transmittance was kept fairly high over 80%. It was proven that both substrate temperature and thermal annealing were important parameters in lowering the electrical resistivity without deteriorating optical properties.     

Influence of annealing treatments for ZnO-doped Zr0.8Sn0.2TiO4 thin films by RF magnetron sputtering

Zirconium tin titanium oxide doped 1 wt.% ZnO thin films on n-type Si substrate were deposited by rf magnetron sputtering at a fixed rf power of 300 W, a substrate temperature of 450 °C, a deposition pressure of 5 mTorr and an Ar/O₂ ratio of 100/0 with various annealing temperatures and annealing times. Electrical properties and microstructures of 1 wt.% ZnO-doped (Zr_0.8Sn_0.2)TiO₄ thin films prepared by rf magnetron sputtering on n-type Si(100) substrates at different annealing temperatures (500 °C-700 °C) and annealing times (2 h-6 h) have been investigated. The structural and morphological characteristics analyzed by X-ray diffraction (XRD) and atomic force microscope (AFM) were sensitive to the treatment conditions such as annealing temperature and annealing time. At an annealing temperature of 600 °C and an annealing time of 6 h, the ZnO-doped (Zr_0.8Sn_0.2)TiO₄ thin films possess a dielectric constant of 46 (at f = 10 MHz), a dissipation factor of 0.059 (at f = 10 MHz), and a low leakage current density of 3.8 × 10^− 9 A/cm² at an electrical field of 1 kV/cm.     

Overview about the optical properties and mechanical stress of different dielectric thin films produced by reactive-low-voltage-ion-plating

Thin films of Ta₂O₅, Nb₂O₅, and HfO₂ were deposited by reactive-low-voltage-ion-plating (RLVIP) on unheated glass and silicon substrates. The film thickness was about 200 nm. Optical properties as well as mechanical film stress of these layers were investigated in dependence of various deposition parameters, i.e. arc current and oxygen partial pressure. For an arc current in the range between 40 and 50 A and an oxygen partial pressure of at least 11 · 10^− 4 mbar good results were obtained. The refractive index and film thickness were calculated from spectrophotometric transmission data using the Swanepoel theory. For example at 550 nm wavelength the refractive index for thin RLVIP-Nb₂O₅-films was found to be n₅₅₀ = 2.40. The optical absorption was obtained by photo-thermal deflection spectrometry. For the investigated materials absorption coefficients in the range of k = 5 · 10^− 4 at 515 nm wavelength were measured. The mechanical film stress was determined by measuring the difference in bending of silicon substrates before and after the deposition process. For dense films, i.e. no water vapour sorption on atmosphere, the mechanical film stress was always compressive with values of some hundred MPa. In case of films deposited with higher arc currents (I_arc > 60A) and lower oxygen pressure (< 15 · 10^− 4 mbar) the influence of a post deposition heat treatment at 350 °C for 4 h on air was also investigated. For these films the properties could clearly be improved by such treatment. However, by using lower arc currents and higher oxygen partial pressure during the ion plating process, immediately dense and environmental stable films with good optical as well as mechanical properties could be achieved without post deposition heat treatment. All the results obtained will be presented in graphs and diagrams.     

The effect of annealing on Al-doped ZnO films deposited by RF magnetron sputtering method for transparent electrodes

In this study, transparent conducting Al-doped zinc oxide (AZO) films with a thickness of 150 nm were prepared on Corning glass substrates by the RF magnetron sputtering with using a ZnO:Al (Al₂O₃: 2 wt.%) target at room temperature. This study investigated the effects of the post-annealing temperature and the annealing ambient on the structural, electrical and optical properties of the AZO films. The films were annealed at temperatures ranging from 300 to 500 °C in steps of 100 °C by using rapid thermal annealing equipment in oxygen. The thicknesses of the films were observed by field emission scanning electron microscopy (FE-SEM); their grain size was calculated from the X-ray diffraction (XRD) spectra using the Scherrer equation. XRD measurements showed the AZO films to be crystallized with strong (002) orientation as substrate temperature increases over 300 °C. Their electrical properties were investigated by using the Hall measurement and their transmittance was measured by UV-vis spectrometry. The AZO film annealed at the 500 °C in oxygen showed an electrical resistivity of 2.24 × 10^− 3 Ω cm and a very high transmittance of 93.5% which were decreased about one order and increased about 9.4%, respectively, compared with as-deposited AZO film.     

ZnO thin films prepared by atomic layer deposition and rf sputtering as an active layer for thin film transistor

Recently, the application of ZnO thin films as an active channel layer of transparent thin film transistor (TFT) has become of great interest. In this study, we deposited ZnO thin films by atomic layer deposition (ALD) from diethyl Zn (DEZ) as a metal precursor and water as a reactant at growth temperatures between 100 and 250 °C. At typical growth conditions, pure ZnO thin films were obtained without any detectable carbon contamination. For comparison of key film properties including microstructure and chemical and electrical properties, ZnO films were also prepared by rf sputtering at room temperature. The microstructure analyses by X-ray diffraction have shown that both of the ALD and sputtered ZnO thin films have (002) preferred orientation. At low growth temperature T_s ≤ 125 °C, ALD ZnO films have high resistivity (> 10 Ω cm) with small mobility (< 3 cm²/V s), while the ones prepared at higher temperature have lower resistivity (< 0.02 Ω cm) with higher mobility (> 15 cm²/V s). Meanwhile, sputtered ZnO films have much higher resistivity than ALD ZnO at most of the growth conditions studied. Based upon the experimental results, the electrical properties of ZnO thin films depending on the growth conditions for application as an active channel layer of TFT were discussed focusing on the comparisons between ALD and sputtering.     

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.     

Stability and effect of annealing on the optical properties of plasma-deposited Ta2O5 and Nb2O5 films

Tantalum and niobium oxide optical thin films were prepared at room temperature by plasma-enhanced chemical vapor deposition using tantalum and niobium pentaethoxide (M(OC₂H₅)₅) precursors. We studied the evolution of their optical and microstructural properties as a result of annealing over a broad temperature range from room temperature up to 900 °C. The as-deposited films were amorphous; their refractive index, n, and extinction coefficient, k, at 550 nm were n = 2.13 and k < 10^− 4 for Ta₂O₅, and n = 2.24 and k < 10^− 4 for Nb₂O₅. The films contained a small amount of residual carbon (∼ 2-6 at.%) bonded mostly to oxygen. During annealing, the onset of crystallization was observed at approximately T_C1 = 650 °C for Ta₂O₅ and at T_C1 = 450 °C for Nb₂O₅. Upon annealing close to T₁ (300 °C for Nb₂O₅ and 400 °C for Ta₂O₅), n at 550 nm decreased by less than 1%. This was correlated with the decrease of carbon content, as suggested by Fourier transform infrared spectroscopy, elastic recoil detection and static secondary ion mass spectroscopy (SIMS) results. During annealing, we observed phase transition from the δ- (hexagonal) phase to the L- (orthorhombic) phase between 800 °C and 900 °C for Ta₂O₅, and between 600 °C and 700 °C for Nb₂O₅. The structural changes were also marked by silicon diffusion from the substrate into the oxide layer at annealing temperatures above 500 °C for Ta₂O₅ and above 400 °C for Nb₂O₅. As a consequence of oxygen, silicon and metal interdiffusion, the interface between the Si substrate and the metal oxide (Ta₂O₅ or Nb₂O₅) is characterized by its broadening, well documented by spectroscopic ellipsometry and SIMS data.