Geometrical factors of argon incorporation in SiO2 films deposited by ion beam sputtering

The geometrical conditions for argon incorporation in SiO₂ films prepared by ion beam sputter deposition were studied experimentally. The main factor was the ejection angular dependence of the incorporated argon from the fused silica target, which was found to be quite different from that of sputtered particles such as silicon. By a judicious choice of the ejection angle and the angle of incidence of the ion beam to the target, it was found that sputter depositions with amounts of incorporated argon differing by a factor of 10 can be achived under the same deposition rate. An immersion test in a 10% aqueous solution of NaOH maintained at 70°C revealed that the SiO₂ film deposited onto an Si(100) substrate under conditions of low argon incorporation flaked off within several minutes, while the sample with a high incorporation of argon showed good adhesion even after a 40 min soak. The results indicated that the conventional idea that ion beam sputter deposition yields films with good adhesion to the substrate and a low incorporation of impurities is not generally valid; instead these characteristics depend markedly on the geometrical conditions of deposition.     

Columnar grain structure in thick sputtered nickel

The same two types of columnar growth structures were observed in sputtered nickel as have been observed in sputtered chromium. Transmission electron microscopy showed that columnar boundaries oriented perpendicular to the substrate surface were actually grain boundaries originating from rotational mismatch between adjacent grains about a common axis ([110] Ni direction) perpendicular to the substrate surface. No porosity or reduced density was observed in these columnar grain boundaries or in an interface 100–200 Å thick that was produced by an interruption in the sputter deposition experiment.     

Sputter deposition technology as a materials engineering

Sputter deposition is currently being widely used in the microelectronics industry for the production of silicon integrated circuits. Recently interest has been focused on sputter deposition as a new materials processing technique. The highly energetic sputtered atoms enhance crystal growth and/or sintering during film growth. This results in lowering of the growth temperature of high temperature materials including cubic diamonds. Single crystals of complex ceramics materials could be prepared by sputter deposition through epitaxial growth process. Atomically controlled deposition using multi-target sputter enables to make man-made superlattice including high-T _C superconductors of layered perovskite. At present sputter deposition is one of key materials technologies for the coming century.     

Sputter deposition of ZnS:Mn/SrS:Ce multilayered thin film white phosphor

A full color thin film electroluminescent (TFEL) display can be fabricated by using color filters in combination with a high efficiency ‘white’ phosphor, such as a thin film multilayered stack of ZnS:Mn and SrS:Ce (denoted ZnS:Mn/SrS:Ce). To date, deposition of these multilayers has been limited to vacuum evaporation techniques and atomic layer epitaxy, both of which require different substrate temperatures for growth of high quality ZnS:Mn and SrS:Ce. This repeated thermal cycling during multilayer deposition can adversely affect electroluminescent (EL) performance and manufacturability. Sputter deposition of ZnS:Mn and SrS:Ce produces high quality phosphors for a wider range of substrate temperatures. We have determined a common set of radio frequency (rf) sputter deposition parameters for ZnS:Mn and SrS:Ce that result in high performance, multilayered white phosphors for use in TFEL devices. The EL performance of our samples is comparable to the best performance reported for evaporated multilayered samples. The major improvement is that the rf sputtered ZnS:Mn and SrS:Ce layers were deposited at the same substrate temperature. We report on the effects of sputter deposition parameters on the resultant composition and morphology of ZnS:Mn and SrS:Ce thin films and multilayers. Their EL performance was evaluated and correlated to composition and morphology.     

The use of camera obscura in sputter deposition

Camera obscura or pinhole camera is an optical device where object is recorded through a small pinhole. A similar experiment was performed in a sputter deposition system. A shield with small aperture (1 mm in diameter) was positioned between the target and the glass substrate. Only the material sputtered in direction of the aperture was deposited on the substrate. In this way a direct image of the target was recorded (similar to a camera obscura). The thickness profile of the image made by the camera obscura is proportional to the flux of emitted particles from the target. Experiments were conducted in a triode sputtering system and in a magnetron sputtering system. The camera obscura was used to study sputtering from different two-element segmental targets: Ti-Al, Al-W, Al-Cu, Ti-W, Ni-C. The thickness profiles of deposits were measured by profilometer. These simple experiments were performed to give a better understanding of the sputtering process.     

Structural and compositional studies of magnetron-sputtered Nd–Fe–B thin films on Si(100)

The structure and composition of the Nd–Fe–B thin films deposited on Si(100) have been investigated. Films have been prepared by direct-current magnetron sputtering in pure argon and xenon sputter media separately. Deposition has been carried out keeping the substrates at room temperature and 360°C. These films were subjected to the post-deposition annealing to a temperature of 60O°C in a vacuum of 5×10–7 Torr. The stoichiometry and structure of these films were analysed and correlated to the deposition and annealing conditions. Films deposited in xenon sputter medium showed better crystalline properties than those sputtered in pure argon. This difference was attributed to the presence of reflected high-energy neutral gas particles in the argon medium. Films deposited in xenon were found to be relatively rich in boron compared with argon-sputtered films. Post-deposition annealing resulted in the interdiffusion at the interface between the film and substrate. The use of a SiO2 film as a barrier layer between the silicon substrate and the Nd–Fe–B film has been explored. Thermally grown SiO2 was found to be an effective diffusion barrier. © 1998 Chapman & Hall     

Inhomogeneous character of the initial stage of ion beam deposition of ultrathin gold films

Gold films with thicknesses ranging from below 1 nm to 3 nm have been simultaneously deposited by the ion beam sputter technique onto the surface of glass substrates smooth on a subnanometer level and onto Si(001) substrates with nanodimensional inhomogeneities in the form of germanium atomic islands. Irrespective of the substrate surface nature, gold deposition initially leads to the formation of a stable layer with a thickness of several atomic monolayers. The gold films with thicknesses above 2 nm are continuous and homogeneous. Terminated in an intermediate stage, the sputter deposition of gold may result in the formation of an inhomogeneous layer of the island type. The results are interpreted taking into account the well-known fact that a high-energy component is present in the flux of the ion beam sputtered target material.     

Analysis of the energy input during wire coating from a cylindrical magnetron source

In order to deposit thin films on a substrate several techniques can be used, e.g. chemical vapour deposition, atomic layer deposition or sputter deposition, depending on their specific advantages and disadvantages due to the related application. A significant parameter is the energy incident upon the substrate by the specific technique, especially when the heat capacitance of the substrate is low. Within this paper we analyse the energy transported into a thin wire (few 10 μm in diameter) during a dynamic inline aluminium sputter process in a cylindrical magnetron source. The evoked heating is important for the tensile strength of the wire and uniformity of the sputtered layer. Therefore, mathematical models were created to estimate the energy input into the wire supported by monte-carlo-simulations of the sputtering process using the TRIM-simulation (Transport and Range of Ions in Matter). Measurements with a Langmuir probe and the corresponding deposition rate were used to quantify these models, showing that at an aluminium coating process of a gold wire, the significant energy input is only due to electrons and ions of the processing gas (argon). Using the heat equation based on the sputtering apparatus' parameters, it was also possible to determine the energy input into the wire with in situ electrical resistance measurements. Both methods did show similar results, whereby the resistance results were more stable. The determined energy input made it possible to calculate the temperature profile during the wire-coating process which can be useful for estimations about film diffusion and process optimisation.     

The high power impulse magnetron sputtering discharge as an ionized physical vapor deposition tool

Various magnetron sputtering tools have been developed that provide a high degree of ionization of the sputtered vapor referred to as ionized physical vapor deposition (IPVD). The ions can be controlled with respect to energy and direction as they arrive to the growth surface which allows for increased control of film properties during growth. Here, the design parameters for IPVD systems are briefly reviewed. The first sputter based IPVD systems utilized a secondary plasma source between the target and the substrate in order to generate a highly ionized sputtered vapor. High power impulse magnetron sputtering (HiPIMS) is a recent sputtering technique that utilizes IPVD where a high density plasma is created by applying high power pulses at low frequency and low duty cycle to a magnetron sputtering device. A summary of the key experimental findings for the HiPIMS discharge is given. Measurements of the temporal and spatial behavior of the plasma parameters indicate electron density peak, that expands from the target with a fixed velocity. The discharge develops from an inert sputtering gas dominated to a sputtered vapor dominated during the pulse. The high electron density results in a high degree of ionization of the deposition material.     

The high power impulse magnetron sputtering discharge as an ionized physical vapor deposition tool

Various magnetron sputtering tools have been developed that provide a high degree of ionization of the sputtered vapor referred to as ionized physical vapor deposition (IPVD). The ions can be controlled with respect to energy and direction as they arrive to the growth surface which allows for increased control of film properties during growth. Here, the design parameters for IPVD systems are briefly reviewed. The first sputter based IPVD systems utilized a secondary plasma source between the target and the substrate in order to generate a highly ionized sputtered vapor. High power impulse magnetron sputtering (HiPIMS) is a recent sputtering technique that utilizes IPVD where a high density plasma is created by applying high power pulses at low frequency and low duty cycle to a magnetron sputtering device. A summary of the key experimental findings for the HiPIMS discharge is given. Measurements of the temporal and spatial behavior of the plasma parameters indicate electron density peak, that expands from the target with a fixed velocity. The discharge develops from an inert sputtering gas dominated to a sputtered vapor dominated during the pulse. The high electron density results in a high degree of ionization of the deposition material.     

Thick magnesium films produced by deposition techniques

Thick magnesium alloy films were prepared by both vapor deposition and sputter deposition techniques. It was found that the properties of the deposited films depend on the substrate material, deposition temperature and release agent, as well as substrate motion. Processing parameters were related to the physical integrity of the deposited film. A direct comparison between an alloy film produced by vapor deposition and an alloy film produced by sputter deposition was also made. It is concluded that sputter deposition is superior to vapor deposition, as the former method can produce a film not only more uniform in thickness, but also with much closer control of chemical composition.     

Magnetron sputter deposition as visualized by Monte Carlo modeling

The Monte Carlo code SIMTRA, simulating the transport of atoms from the source to the substrate during physical vapor deposition (PVD), is used in several case studies to highlight important issues related to thin film sputter deposition. Atom collisions during gas-phase transport affect the energy distribution and the deposition profile of sputtered atoms. The model is compared with published models for the thermalization of sputtered atoms, and some features of this process are discussed. The vacuum chamber design can be easily implemented in the Monte Carlo code, and this possibility is used to discuss the use of shutters and masks, and the influence of the deposition geometry. The code can also be used to predict the composition when combing different sources, segmented targets, and during combinatorial synthesis of thin films. As the details of the transport are described, the velocity and the density of the gas-phase atoms can be calculated which can assist in the interpretation of several spectroscopic techniques such as laser induced fluorescence. Not only the energy loss of the transported atoms, but also their remaining energy upon arrival at the substrate is important as the incident energy strongly influences thin film growth. To illustrate the latter, the model is also used to study the growth of biaxially aligned thin films. The key parameters influencing the level of alignment can easily be retrieved using SIMTRA.     

Electroless deposition,post annealing and characterization of nickel films on silicon

Electroless deposition of nickel (EN) films on n-type silicon has been investigated under different process conditions. The interface between the film and substrate has been characterized for electrical properties by probing the contact resistances. X-ray diffraction and atomic force microscopy have been performed to obtain information about the structural and morphological details of the films. As a comparative study, nickel films have also been sputter deposited on silicon substrates. An as-deposited electroless film is observed to form non-ohmic contact while in a sputtered film prepared without the application of substrate heating, the formation of metal-insulating-semiconductor type junction is seen.     

The Effect of Sputter Cathode Design on Deposition Parameters

Recent advances in the classic magnetron sputter cathode design have enabled higher quality thin films and improved deposition rates. New designs that have eliminated traditional sputter target hold down fixtures and the retraction of the dark space shield have greatly increased the available sputter target surface area while reducing the probability of re‐deposition of target material on cathode components that could lead to shorting and contamination. Hermetic sealing strategies have mitigated gas permeation through the sputter cathode and enabled lower operating pressures which substantially reduces process gas inclusions in sputtered films.     

直流溅射工艺参数对Mo薄膜结构及电性能的影响

采用直流磁控溅射法在SLG衬底上沉积Mo薄膜,对不同溅射功率和溅射工作气压下沉积的薄膜进行X射线衍射、SEM(扫描电子显微镜)、电阻率测试,讨论了工艺参数对沉积Mo薄膜相结构、表面微观形貌、薄膜沉积速率和电学性能的影响。结果表明,随着溅射功率的增加,薄膜的结晶性能变好,沉积速率提高,在沉积功率范围内薄膜均匀致密,表面无空隙,电阻率较低;随着溅射工作气压增加,薄膜结晶性能变差,沉积速率先增加后降低,在沉积工作气压范围内,薄膜致密;随气压降低,电阻率急剧减小。因此,较高的溅射功率和较低的工作气压沉积的Mo薄膜更适合作CIGS薄膜太阳电池的BC层(背接触层)。     

离子束溅射沉积羟基磷灰石涂层钛种植体材料的制备和表征

采用Ａｒ＾＋离子束溅射沉积技术和钛基体上沉积羟基磷灰石薄膜涂层,Ａｒ＾＋离子束的能量分别为０．９ｋｅＶ、１．２ｋｅＶ和１．５ｋｅＶ。利用Ｘ射线衍射（ＸＲＤ）、扫描电（ＳＥＭ０、透射电镜（ＴＥＭ）和红外光谱（ＦＴＩＲ）等检测方法,对制备的羟基磷灰石薄膜涂层进行了表征。Ｘ射线衍射和透射电结果表明该薄膜涂层为非晶态;红外光谱中无羟基（ＯＨ）特征峰存在,ＣＯ３根吸收峰的出现说明制备过程中会引入ＣＯ３根;扫     

Effect of substrate temperature and deposited thickness on the formation of iron silicide prepared by ion beam sputter deposition

Ion beam sputter deposition (IBSD) method was employed to find optimum conditions for the formation of epitaxial β-FeSi₂ films on Si(100) substrate. It was found that crystal structure of the films as determined by X-ray diffraction (XRD) analysis is dependent on the substrate temperature as well as on the deposited thickness of sputtered Fe. The film with best crystal properties was obtained either at 873 K with the deposited Fe thickness of 15 nm, or at 973 K with the deposited Fe thickness of 30 nm. The obtained results indicate the importance of Fe and/or Si diffusion in determining the crystal properties of β-FeSi₂ film.     

Sputtered Ni-Cr-based resistors terminated on sputtered aluminum and screeen-printed Pt-Ag conductors

The standard technology to fabricate thin film resistors is to deposit a layer of resistive material, usually by evaporation or sputtering, followed by thin layers of nickel and gold. Gold plating is then used to augment the thickness of the gold layer, typically to 1 μm. The three-layer structure is then selectively etched to yield resistors with terminations suitable for wire bonding and soldering. We have used a somewhat unconventional approach in which a film 1–2 μm thick of aluminum is first sputtered onto 99.5% Al₂O₃ substrates, then etched to produce the desired conductor pattern. Isotropic (wet) etching is used to produce sloping edges to contact better the Ni-Cr based resistor material which is sputter deposited and patterned using a lift-off technique.We have also combined the thin and thick film technologies by terminating our thin film resistors on Pt-Ag conductors which are screen printed onto the substrate prior to sputter deposition of the resistors.Aluminum terminations can be wire bonded, or, when soldering is required, coated with sputtered or plated nickel. When a layer of suitable adhesion promoter is sputtered between aluminum and nickel, adhesion of aluminum to nickel is greatly improved.The use of a sputtering target made of an Ni-Cr-based alloy has enabled us to obtain resistors in the 50 Ω/□ range which can be mass produced with near-zero temperature coefficient of resistance (TCR). Such resistors show stability within better than 0.02% after 1000 h at 398 K under load. Also reported are resistance spread and shift, due to annealing, as a function of aspect ratio (ratio between length and width of resistor) for both aluminum and Pt-Ag terminations, as well as TCR as a function of annealing temperature.     

Differential sputter yield measurements using cavity ringdown spectroscopy

The first use of cavity ringdown spectroscopy (CRDS) to measure differential (angular) sputter yield profiles of sputtered particles is reported. Owing to the path-integrated nature of CRDS, inversion techniques are required. Our approach is to scan the optical axis relative to the source of sputtered particles and to measure the spatial profile of the CRDS signals. Modeling is then used to determine the differential sputter yield profile from the measured CRDS spatial profile. Demonstrative measurements are made with a Nd:YAG pumped optical parametric oscillator laser system for 750 eV argon ions normally incident on a molybdenum target. At these conditions we find an under- cosine sputtering distribution characterized by alpha = 0.22 +/- 0.07 in good agreement with past quartz crystal microbalance measurements (alpha = 0.19).     

Investigation of Tin films reactively sputtered using a sputter gun

TiN films were prepared by reactive sputtering of titanium in a gas mixture of argon and nitrogen using a sputter gun. The properties of the sputtered films were investigated with Rutherford backscattering spectrometry, electrical resistivity and optical reflectivity measurements, X-ray diffractometry and transmission electron microscopy. For a given input power to the sputter gun the film properties depend on the gas composition, the bias voltage applied to the substrates and oxygen contamination during sputtering. In addition, it was found that powering the sputter gun with r.f. causes an iron contamination in the films by material sputtered off the plasma confinement shield. This contamination is very much reduced when d.c. is employed to power the sputter gun.