Effects of sputtering pressure and nitrogen concentration on the preferred orientation of AIN thin films

Aluminium-nitride films were prepared on glass substrates by reactive radio frequency (r.f.) magnetron sputtering in argon/nitrogen gas mixtures containing 25 ~ 75 1/2; nitrogen at substrate temperatures below 150C. It is important to control the crystallographic orientation and the surface morphology of the films with the deposition parameters for surface-acoustic-wave (SAW) devices. The change of crystallographic orientation with the sputtering pressure and the nitrogen concentration was calculated from the texture coefficient of the (0002) plane based on X-ray diffraction (XRD) patterns. It was found that a change of the c-axis from a parallel to a normal orientation, with respect to the substrate surface, occurred with a decrease in the sputtering pressure and an increase in the nitrogen concentration. From observations of the cross-section and the surface morphology, aluminium-nitride films exhibited a columnar structure and the grain size at the film surface increased an increase in the sputtering pressure and with a decrease in the nitrogen concentration.     

Mo电极形貌对AIN薄膜择优取向生长的影响

采用射频磁控溅射方法在不同形貌的Mo电极上制备了(002)择优取向的AlN薄膜。采用XRD、FESEM表征了Mo电极及AlN薄膜的结构、表面形貌及择优取向。结果表明,Mo电极的形貌影响AlN薄膜的择优取向生长,在较高溅射气压下沉积的Mo电极晶粒细小、分布均匀,有助于AlN薄膜(002)择优取向生长。     

Influence of deposition parameters on preferred orientation of RF magnetron sputtered BST thin films

Ba_0.65Sr_0.35TiO₃ (BST) thin films have been deposited by radio frequency magnetron sputtering. The effects of the deposition parameters on the crystallization and microstructure of BST thin films were investigated by X-ray diffraction and field emission scanning electron microscopy, respectively. The crystallization behavior of these films was apparently affected by the substrate temperature, annealing temperature and sputtering pressure. The as-deposited thin films at room temperature were amorphous. However, the improved crystallization is observed for BST thin films deposited at higher temperature. As the annealing temperature increased, the dominant X-ray diffraction peaks became sharper and more intense. The dominant diffraction peaks increased with the sputtering pressures increasing as the films deposited at 0.37–1.2 Pa. With increasing the sputtering pressure up to 3.9 Pa, BST thin films had the (110) + (200) preferred orientation. Possible correlations of the crystallization with changes in the sputtering pressure were discussed. The SEM morphologies indicated the film was small grains, smooth, and the interface between the film and the substrate was sharp and clear.     

Electrical,morphological and structural properties of RF magnetron sputtered Mo thin films for application in thin film photovoltaic solar cells

Molybdenum (Mo) thin films were deposited using radio frequency magnetron sputtering, for application as a metal back contact material in “substrate configuration” thin film solar cells. The variations of the electrical, morphological, and structural properties of the deposited films with sputtering pressure, sputtering power and post-deposition annealing were determined. The electrical conductivity of the Mo films was found to increase with decreasing sputtering pressure and increasing sputtering power. X-ray diffraction data showed that all the films had a (110) preferred orientation that became less pronounced at higher sputtering power while being relatively insensitive to process pressure. The lattice stress within the films changed from tensile to compressive with increasing sputtering power and the tensile stress increased with increasing sputtering pressure. The surface morphology of the films changed from pyramids to cigar-shaped grains for a sputtering power between 100 and 200 W, remaining largely unchanged at higher power. These grains were also observed to decrease in size with increasing sputtering pressure. Annealing the films was found to affect the resistivity and stress of the films. The resistivity increased due to the presence of residual oxygen and the stress changed from tensile to compressive. The annealing step was not found to affect the crystallisation and grain growth of the Mo films.     

Preparation of highly oriented aluminum nitride thin films on molybdenum bottom electrodes using metal interlayers

We have investigated the influence of metal interlayers on the crystallinity and crystal orientation of aluminum nitride (AlN) thin films prepared on molybdenum (Mo) bottom electrodes. The interlayres were prepared between the Mo bottom electrodes and silicon substrates. Although the sputtering conditions of AlN films and Mo electrodes were the same, the Au/Ti interlayer drastically increased the XRD intensity of the (0002) AlN and (110) Mo planes, and decreased the full width at half maximum (FWHM) of the rocking curves of the (0002) AlN peaks from 9.22 to 3.02. The Au/Ti interlayers were effective for the improvement in the crystallinity and crystal orientation of AlN films deposited on Mo bottom electrodes. Furthermore, we clarified that the crystallinity and orientation of AlN films and Mo electrodes strongly depend on those of the Au interlayers, and the Au interlayers influence the morphologies of the Mo electrodes.     

Effects of nitrogen partial pressure on microstructure,morphology and N/Ti ratio of TiN films deposited by reactive magnetron sputtering

Abstract

TiN films were deposited on Si(111) substrates at different nitrogen partial pressures with reactive magnetron sputtering. The crystal structure and preferred growth orientation of the films were determined using X-ray diffraction (XRD) analysis. Their morphology and composition were analysed using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). It is found that with the increase in nitrogen partial pressure, the growth of TiN films varies from the {111} preferred orientation to the {100} preferred orientation and the deposition rate of TiN films decreases. When the {111} preferred orientation is presented, TiN films reveal a kind of surface morphology of triangular pyramid with right angles; while the {100} orientation is dominant, TiN films characterise another kind of domelike surface morphology. Furthermore, the N/Ti ratio of the TiN films first increases, then decreases and increases again as nitrogen partial pressure enlarges.     

Preparation of highly oriented AlN thin films on glass substrates by helicon plasma sputtering and design of experiments

Aluminum nitride (AlN) thin films were deposited by a helicon plasma sputtering system with a radical cell. We investigated the effects of eight sputtering control factors on the crystal orientation of the films by design of experiments and the analysis of variance (ANOVA) in order to prepare highly oriented AlN thin films on silica glass substrates. Consequently, it was proved statistically that the distance between a target and a substrate, the sputtering pressure and the substrate temperature are significant control factors for the crystal orientation of the films. Especially, the distance is the most important factor of the eight control factors, which has not been reported so far. On the other hand, the effects of the cathode r.f. coil power, the radical cell power, the nitrogen concentration, the sputtering time and the cathode power are not statistically significant. Moreover, a detailed investigation of the dependence of the orientation on the three important control factors was carried out to optimize the sputtering conditions. The full width at half-maximum (FWHM) of the X-ray rocking curve of the film deposited under the optimized sputtering conditions is 2.4° (σ=1.3°). This orientation is the highest in the AlN thin films deposited on amorphous substrates reported to our knowledge.     

Growth of highly c-axis oriented aluminum nitride thin films on β-tantalum bottom electrodes

We have investigated the influence of tantalum (Ta) bottom electrodes on the crystallinity and crystal orientation of aluminum nitride (AlN) thin films. AlN thin films and Ta electrodes were prepared by using rf magnetron sputtering method. The crystal structure of the Ta electrodes was tetragonal (β-Ta, a metastable phase) at room temperature. The crystallinity and orientation of the AlN thin films and Ta electrodes strongly depended on sputtering conditions. Especially, the crystallinity and crystal orientation of the Ta electrodes were influenced by their film thickness and the substrate temperature. When the thickness of the Ta bottom electrodes was 200 nm and the substrate temperature was 100 °C, the AlN thin films indicated high c-axis orientation (the full width at half maximum of rocking curve of 3.9°). The crystal orientation of the AlN film was comparable to that of AlN thin films deposited on face centered cubic (fcc) lattice structure metal, such as Au, Pt and Al, bottom electrodes.     

氮分压对ZrN薄膜结构及颜色的影响

采用直流反应磁控溅射法,通过改变反应气体N2分压(5%、10%、20%、30%、40%、50%、60%),在SiO2/Si(111)基片上制备ZrN薄膜。利用XRD、SEM、EDS分析了薄膜的物相、结构、形貌以及成分,使用分光光度计测量了薄膜的反射光谱,并进一步确定了薄膜颜色在L*a*b*色度坐标中的位置,研究了氮分压对薄膜颜色的影响,以及ZrN薄膜颜色与薄膜成分、结构之间的关系。分析结果表明:在不同的氮分压下,ZrN薄膜具有较好的成膜质量;随着氮分压的增加,薄膜沉积速率降低、N含量增加;薄膜结晶度先升高后降低、且在氮分压为10%时,薄膜出现(111)的择优取向;薄膜颜色随薄膜成分结构的改变而发生明显的变化(颜色由银色向金色、暗金、深褐色以及非本征颜色转变)。当反应气体N2分压较低时,分压的增加使得锆与氮更容易键合,导致薄膜中N含量增加,使ZrN结晶度增大并出现择优取向。当N2分压超过10%后,薄膜中多余的氮处于晶格的间隙位置,使得薄膜晶格间距变大且结晶度降低,薄膜成分结构的改变导致了薄膜颜色的变化。     

Effect of pressure and substrate temperature on the deposition of nano-structured silicon-carbon-nitride superhard coatings by magnetron sputtering

A systematic investigation on the deposition of silicon-carbon-nitride (Si-C-N) films under varying deposition conditions such as pressure, substrate temperature and nitrogen content was carried out by radio frequency and direct current magnetron sputtering techniques. Significant role of the different deposition parameters on hardness and structure in the film was observed. It was observed that there was a certain range of nitrogen to argon partial pressure ratio (90:10 to 98:2) for which the particle size was reduced and the films were smooth with fine particle growth, beyond this limit the films had larger particle growth and roughness. The hardness of the deposited film varied between 4400 Hv and 473 Hv depending on deposition condition. Si-C-N film with hardness above 4400 Hv by reactive RF magnetron sputtering from SiC-C composite target in nitrogen-argon was obtained. X-ray diffraction studies revealed the amorphous nature of the deposited films, whereas nano-crystallinity of the particles was noticed during atomic forced microscopy observations. X-ray photoelectron spectroscopy analysis showed the presence of C-N and Si-N bonds in the harder films. It was found that the presence of β-C₃N₄, Si₃N₄ and graphite phases and the particle growth in the deposited films control the hardness of the film.     

High quality epitaxial ZnO films grown on solid-phase crystallized buffer layers

High quality epitaxial ZnO films on sapphire (110) plane have been fabricated on ZnO homo-buffer layers crystallized via solid-phase epitaxially (SPE). The SPE-ZnO films are fabricated by annealing of amorphous ZnON (a-ZnON) films deposited by RF magnetron sputtering. During annealing, the a-ZnON films are oxidized and converted to ZnO crystal. X-ray diffraction (XRD) analysis shows that the resultant films are epitaxially grown on the sapphire substrates. By using the SPE-ZnO films as homo-buffer layers, the ZnO films with high crystallinity, which are deposited by RF magnetron sputtering, are fabricated. The full width at half-maximum of XRD patterns for 2θ-ω and ω scan of (002) plane are 0.094° and 0.12°, respectively, being significantly small compared with 0.24° and 0.55° for the films without buffer layers. Thus utilizing SPE buffer layers is very promising to obtain epitaxial ZnO films with high crystallinity.     

Effects of vapor annealing on the properties of the ZnO films prepared by spray pyrolysis

Zinc oxide (ZnO) films were deposited on (0 0 0 1) sapphire substrates from a solution containing zinc acetate. The films were deposited in a vertical type hot wall reactor by the pyrolysis of an aerosol produced by an ultrasonic generator. To increase the resistivity of the films, copper doping and annealing in an ambient of water vapor (vapor annealing) were carried out. The resistivity of a 0.5 wt % copper doped ZnO film was around 24 cm. The vapor annealing resulted in a 10⁷-fold increase in the resistivity. After annealing, the crystallinity of the films was improved, as determined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). All the films annealed at 600°C for 2 h exhibited a strong (0 0 2) orientation with a smooth surface The crystallinity, surface morphology, composition and electrical properties of the as-deposited and vapor-annealed films were investigated.     

Effect of substrate temperature on the structure and optical properties of ZnO thin films deposited by reactive rf magnetron sputtering

Zinc Oxide films were deposited on quartz substrates by reactive rf magnetron sputtering of zinc target. The effect of substrate temperature on the crystallinity and band edge luminescence has been studied. The films deposited at 300 °C exhibited the strongest c-axis orientation. AFM and Raman studies indicated that the films deposited at 600 °C possess better overall crystallinity with reduction of optically active defects, leading to strong and narrow PL emission.     

Sputter deposition of semicrystalline tin dioxide films

Tin dioxide is emerging as an important material for use in copper indium gallium diselenide based solar cells. Amorphous tin dioxide may be used as a glass overlayer for covering the entire device and protecting it against water permeation. Tin dioxide is also a viable semiconductor candidate to replace the wide band gap zinc oxide window layer to improve the long-term device reliability. The film properties required by these two applications are different. Amorphous films have superior water permeation resistance while polycrystalline films generally have better charge carrier transport properties. Thus, it is important to understand how to tune the structure of tin dioxide films between amorphous and polycrystalline. Using X-ray diffraction (XRD) and Hall-effect measurements, we have studied the structure and electrical properties of tin dioxide films deposited by magnetron sputtering as a function of deposition temperature, sputtering power, feed gas composition and film thickness. Films deposited at room temperature are semicrystalline with nanometer size SnO₂ crystals embedded in an amorphous matrix. Film crystallinity increases with deposition temperature. When the films are crystalline, the X-ray diffraction intensity pattern is different than that of the powder diffraction pattern indicating that the films are textured with (101) and (211) directions oriented parallel to the surface normal. This texturing is observed on a variety of substrates including soda-lime glass (SLG), Mo-coated soda-lime glass and (100) silicon. Addition of oxygen to the sputtering gas, argon, increases the crystallinity and changes the orientation of the tin dioxide grains: (110) XRD intensity increases relative to the (101) and (211) diffraction peaks and this effect is observed both on Mo-coated SLG and (100) silicon wafers. Films with resistivities ranging between 8 mΩ cm and 800 mΩ cm could be deposited. The films are n-type with carrier concentrations in the 3 × 10¹⁸ cm^− 3 to 3 × 10²⁰ cm^− 3 range. Carrier concentration decreases when the oxygen concentration in the feed gas is above 5%. Electron mobilities range from 1 to 7 cm²/V s and increase with increasing film thickness, oxygen addition to the feed gas and film crystallinity. Electron mobilities in the 1-3 cm²/V s range can be obtained even in semicrystalline films. Initial deposition rates range from 4 nm/min at low sputtering power to 11 nm/min at higher powers. However, deposition rate decreases with deposition time by as much as 30%.     

Effects of surface roughness of substrates on the c-axis preferred orientation of ZnO films deposited by r.f. magnetron sputtering

The c-axis preferred orientation of ZnO film is the most important factor for its successful application in piezoelectric devices. The effects of surface roughness of the substrate on the c-axis preferred orientation of ZnO thin films, deposited by radio frequency magnetron sputtering, were investigated. During sputtering, the oxygen content in the argon environment used was varied from 0 to 70% at a total sputtering pressure of 10 mTorr. Very smooth Si, smooth evaporated Au/Si, smooth evaporated-Al/Si, and rough sputtered-Al/Si were used as substrates. Their r.m.s. roughnesses, as measured by atomic force microscopy, were 1.27, 17.1, 21.1 and 65-118 Å, respectively. The crystalline structure and the angular spread of the (0 0* 2) plane normal to the ZnO films were determined using X-ray diffraction and X-ray rocking curves, respectively. The crystallinity and the preferred c-axis orientation of the ZnO films were strongly dependent on the surface roughness of the substrates rather than on the oxygen content of the working environment or on the chemical nature of the substrate.     

Optical emission, electron temperature, and microstructure of Cu film prepared by magnetron sputtering

Cu films are deposited on Si (001) substrates under various Ar deposition pressures by radio frequency (RF) magnetron sputtering. The crystallinity and orientation of Cu films is characterized by employing X-ray diffraction technique. It is found that the intensities of Cu peaks change with Ar pressure systematically, and ~ 5 Pa is the most favorable Ar pressure to get highly (111) oriented Cu films. Electron temperature and optical emission spectrum (OES) of plasma plume are measured using the double Langmuir probes, a monochromator and a PMT detector. We found that the electron temperature decreases exponentially with increasing deposition pressure, and there are strong correlations of optical emission, electron temperature, and the microstructure of Cu films. We define a Cu atomic relevant coefficient to describe the crystallinity and orientation of Cu films prepared under various pressures. This work may provide a method to understand the crystallinity and orientation evolution of the film prepared by sputtering via investigating optical emission and electron temperature.     

Effect of oxygen plasma treatment on bonding states for columnar structured a-CNx thin films prepared by reactive sputtering

Amorphous carbon nitride (a-CN) thin films were deposited on silicon single crystal substrates by rf-reactive sputtering method using a graphite target and nitrogen gas. The substrate temperature was varied from room temperature (RT) to 853 K. After deposition, the effect of oxygen plasma treatment on bonding structures of the film surface has been studied by using an oxygen discharge at 16 Pa and rf power of 85 W. The chemical bonding states and film composition were analyzed by X-ray photoelectron spectroscopy (XPS), while film thickness was obtained from scanning electron microscopy (SEM) and ellipsometer. XPS study revealed that the films have NO₂ and NO₃ bonding structures when the films are deposited at temperatures higher than 673 K. After exposure to oxygen plasma, carbon in the film surface was etched selectively and this phenomenon was observed in all films. In contrast, the surface concentration of nitrogen was ket at constant values before and after oxygen plasma treatment. The NO₃ bonding state had dramatically increased after oxygen plasma treatment for films deposited at higher deposition temperatures. The film surfaces have been observed to change the function from hydrophobic to hydrophilic after oxygen plasma treatment.     

溅射工艺对BST薄膜取向行为的影响

采用射频磁控溅射法在Si(100)衬底上沉积了Ba0.65Sr0.35TiO3薄膜.借助XRD、AFM和SEM研究了衬底温度、退火温度、溅射气压等不同的溅射参数对Ba0.65Sr0.35TiO3薄膜的晶化行为和显微结构的影响.在室温下沉积并未经退火处理的Ba0.65Sr0.35TiO3 薄膜是无定形态,在较高温度下沉积的薄膜晶化相对较好;随着在氧气气氛中退火温度的升高,X射线衍射峰的半峰宽变窄,衍射峰强度增强;在0.37～1.2Pa气压下沉积的Ba0.65Sr0.35TiO3薄膜有(110)和(200)主衍射峰,且其强度随溅射气压的增加而增强;当溅射气压继续升到3.9Pa,(110)和(200)衍射峰明显增强,说明Ba0.65Sr0.35TiO3 薄膜具有(110) (200)择优取向.AFM和SEM结果显示薄膜晶粒细小均匀、结构致密、表面平整,且无裂纹、无孔洞.分析结果显示优化工艺参数制备的Ba0.65Sr0.35TiO3 薄膜是用以制备非致冷红外探测器的优质材料.     

On the processing-structure-property relationship of ITO layers deposited on crystalline and amorphous Si

Indium-tin-oxide (ITO) antireflection coatings were deposited on crystalline Si (c-Si), amorphous hydrogenated Si (a-Si:H) and glass substrates at room temperature (RT), 160 °C and 230 °C by magnetron sputtering. The films were characterised using atomic force microscopy, transmission electron microscopy, angle resolved X-ray photoelectron spectroscopy, combined with resistance and transmittance measurements. The conductivity and refractive index as well as the morphology of the ITO films showed a significant dependence on the processing conditions. The films deposited on the two different Si substrates at higher temperatures have rougher surfaces compared to the RT ones due to the development of crystallinity and growth of columnar grains.     

Optical characterization of BCN films deposited at various N2/Ar gas flow ratios by RF magnetron sputtering

We present the deposition and optical characterization of amorphous thin films of boron carbonitride (BCN). The BCN thin films were deposited in a radio frequency magnetron sputtering system using a B₄C target. Films of different compositions were deposited by varying the ratio of argon and nitrogen gas in the sputtering ambient. X-ray photoelectron spectroscopy was used to perform surface characterization of the deposited films and a change in composition with nitrogen flow ratio was observed. The effect of gas flow ratios on the optical properties of the films was also investigated. It was found that the transmittance of the films increases with nitrogen incorporation. The optical band gap of the films ranged from 2.0 eV to 3.1 eV and increased with N₂/Ar gas flow ratio except at the highest ratio.