Effect of scattering of sputtered atoms on the growth rate of films fabricated by magnetron sputtering

The results of the theoretical calculations of the fraction of unscattered sputtered atoms in magnetron sputtering are presented. The experimentally obtained pressure dependence of the growth rate of silicon films reveals a correlation with the theoretically calculated dependence of the fraction of unscattered sputtered atoms. If the pressure is raised from 1.5 to 8.5 mTorr, the growth rate of silicon films decreases by 25%, while the fraction of unscattered sputtered atoms over the cathode–substrate distance decreases by as much as 90%.     

薄膜溅射沉积过程中的原子喷丸效应

原子喷丸效应是薄膜溅射沉积过程中的普遍现象，是指反弹工作气体原子和溅射原子构成的荷能粒子流对生长膜面的轰击作用。这些荷能粒子在向基片输运的过程中受到工作气体原子的散射。原子喷丸效应与靶材和工作气体的原子质量比以及工作气体压强密切相关。以平面磁控溅射Co－Cr，Ni-Fe和Gd－Fe等二元合金薄膜为对象，研究其内应力与Ar工作气体压强的关系，并探讨原子喷丸效应对应力的影响。在靶材原子质量较大并且工作气体压强较低的情形下，可导致薄膜中呈压应力。     

Effect of oxygen concentration and system geometry on the current-voltage relations during reactive sputter deposition of titanium dioxide thin films

Current-voltage relations at different magnetron sputtering systems and gas mixtures were studied during reactive sputter deposition of titanium dioxide thin films. The main goal of this work was to investigate the influence of reactive gas mixture (Ar + O₂) and system geometry on the electrical characteristics of the discharge. The geometries utilized were the conventional magnetron sputtering, hollow cathode magnetron sputtering and triode magnetron sputtering. A change in the system geometry leads to a change in the electric field distribution, which alters the working range of the discharge voltage and magnetron efficiency. It is noticed that the discharge voltage at constant current can be reduced when the geometry is altered from conventional magnetron to hollow cathode magnetron or triode magnetron, at the same time the magnetron efficiency is increased when hollow cathode magnetron or triode magnetron are used instead of conventional magnetron sputtering.     

The preparation of permalloy 80/20 thin films using a pulsed DC discharge in a hollow cathode

Permalloy thin films have many applications as sensors and actuators but the preparation of magnetic films by magnetron sputtering is problematic since the target material reduces or changes the magnetic configuration of the magnetron. Hollow cathode discharges can produce similar or greater plasma densities to that found in magnetron sputtering and can therefore be operated over a similar pressure range. Pulsed DC sputtering has been seen to have some advantages compared to DC or RF sputtering. In this paper we report the use of a combination of pulsed DC sputtering with a hollow cathode system to prepare thin films of Permalloy. The deposition rate was found to strongly depend on the gas flow used to prepare the thin films. Combinations of the experimental conditions were found to produce films with a (111) preferential crystal orientation and that the grain size of the crystals was mainly determined by the deposition rate. Furthermore, changes in the degree of ion bombardment did not appear to have any significant affect on the structure of the deposit.     

RF磁控溅射工艺对TiNi(1-x)Cux合金薄膜组织形貌的影响

采用RF磁控溅射技术制备了TiNi(1-x)Cux合金薄膜，利用扫描电镜，电子能谱仪和XRD技术分析研究了RF磁控溅射工艺对TiNi(1-x)Cux合金薄膜组织形貌的影响规律。结果表明：在基片不加热的条件下溅射薄膜组织结构为非晶，并呈柱状形貌垂直于基片生长；经650-720℃，3min退火处理后，薄膜均发生晶化转变；在他它条件相同的情况下，溅射功率和工作气压对薄膜组织形貌有很大影响；薄膜的柱状单胞直径，薄膜厚度和生长速度均随溅射功率的增长而增长，但当溅射功率一定时，工作气压增加使柱状单胞直径，薄膜厚度和薄膜的生长速率显著减小，RF磁控溅射过程中，沉积原子的活性及其沉积速率是影响薄膜组织形貌的主要原因。     

铝靶脉冲反应溅射沉积氧化铝薄膜中的迟滞回线的研究

采用脉冲磁控反应溅射工艺进行氧化铝薄膜的沉积实验 ,对该工艺过程中溅射电压和沉积速率与氧流量的“迟滞回线”现象进行了研究。通过给出靶面刻蚀区氧化层厚度与氧分压之间的关系 ,解释了薄膜沉积速率变化的原因。     

A method to fabricate nanorod films on aluminum lattice membrane by magnetron sputtering

The development of the process of fabricating well-aligned nanostructures materials is one of the interesting subjects in current material science. This paper describes a new method to fabricate high-density, vertically-aligned nanorods of metal and metal compound by magnetron sputtering on aluminum lattice membrane (ALM). The ALM was formed by chemical etching of the hexagonal arrays of pore layer from the anodic aluminum oxide membrane, resulting in unnumbered hemisphere nanopits with uniform protuberant nanodots on the surface of aluminum. The ALM was employed as a substrate to fabricate well-aligned Ni, Cu, WC nanorod films by magnetron sputtering. Scanning electron microscopy images showed that the sputtered atoms have been absorbed preferentially onto the protuberant nanodots of ALM in the process of magnetron sputtering, and have begun to nucleate and grow into nanorods. The diameter of the nanorods depends on the diameter of hemisphere on the surface of the substrate, while the thickness of thin films can be controlled by deposition time.     

偏压对直流磁控溅射Fe-N薄膜结构及性能的影响

为了揭示偏压对溅射态Fe-N薄膜磁学行为的影响规律及机理,采用直流磁控溅射工艺在不同偏压下制备了Fe-N薄膜.利用掠入射X射线衍射、小角X射线散射技术和振动样品磁强计研究了薄膜的相结构、厚度、表面粗糙度以及磁性能.结果表明,增加偏压有利于薄膜中非晶的形成,且随着偏压的增大,薄膜的厚度增加,表面粗糙度降低.Fe-N薄膜的磁性能表明,随着偏压的增加,薄膜的饱和磁化强度和矫顽力均有不同程度的减小.偏压的增加导致Fe-N薄膜由晶态向非晶态转变,从而引起磁性能的改变.     

Breakdown in planar magnetron discharges of argon on copper

In magnetrons the magnetic field confines partially the electron swarm in a trap near the cathode increasing sputtering yield and deposition rates. The magnetic field also decreases the ignition voltage even at relatively low pressures thus allowing sputtering at lower pressures. Under this conditions fewer collisions, less diffusion and less thermalization of the sputtered atoms occur during the transport to the substrates. Atoms arrive at substrates with larger energy and at higher rates.We present an experimental study of the magnetic field influence on the breakdown voltage in planar magnetron abnormal glow discharges for argon on copper. A magnetron cathode was constructed, with a finely tuneable magnetic configuration. The experimental curves of the breakdown voltage as a function of the discharge pressure at constant “confinement power” show minima similar to those occurring in Paschen's law. At lower pressures the breakdown voltage has a strong dependence on magnetic configuration and changes from 750 to 250 V can be found. At higher pressures the breakdown voltage is less sensitive to the magnetic field.Paschen's law could not be fitted to the experimental results and as alternative an empirical expression is proposed and its parameters discussed.The results can be understood by the increased length of the average electron path both in helical and cycloid type trajectories near the cathode and by the reduction of the electron drift towards the anode and the walls of the chamber. In the Townsend regime, before breakdown and fixed voltage the electron density near the cathode increases with the confinement power. This causes a higher flux and energy of the ions that strike on the cathode for the same applied voltage. The voltage needed to get the self-sustained discharge is strongly reduced.     

Friction and adhesion properties of fluorocarbon polymer thin films prepared by magnetron sputtering

Fluorocarbon polymer thin films were deposited onto a SUS302 substrate with a poly(tetrafluoroethylene) (PTFE) target by three different types of r.f. magnetron sputtering systems with strong, weak and unbalanced magnetic fields. Friction and adhesion properties of these polymer thin films were evaluated.Friction coefficient of polymer thin films prepared with strong magnetic field, unbalanced magnetron and without magnetron (r.f. sputtering) was almost the same level, however, that prepared with the weak magnetic field was slightly lower than those of other thin films. Wear durability of polymer thin film increased with increase of the magnetic field.Adhesion strength between these thin films and SUS302 substrate and shear stress were measured by SAICAS. Both of the adhesion strength and shear stress of polymer thin films prepared with r.f. sputtering (without magnetron) were slightly higher than those prepared by magnetron sputtering systems.     

Annealing dependence of residual stress and optical properties of TiO2 thin film deposited by different deposition methods

Titanium oxide (TiO(2)) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 degrees C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. TiO(2) films deposited by sputtering were generally more stable during annealing than those deposited by evaporation.     

Deposition pressure and rate effects on the microstructure and magnetic properties of sputtered tape media

Sputtered magnetic tape media were prepared by DC magnetron sputtering on polyimide substrates at different deposition conditions. The structure, texture and magnetic properties of the sputtered films were systematically studied using transmission electron microscopy, X-ray diffraction and alternating gradient magnetometer. The microstructure of sputtered media is greatly influenced by the deposition conditions, such as deposition pressure and rate. High sputtering pressure and slow deposition rate produced high coercivity and low delta M films. The sputtered tape media have the desired grain segregation structure which is essential for low-noise media fabrication. X-ray diffraction analysis revealed that the stress of film is closely related to the deposition pressure. The stress of the film stack can be tuned for specific applications and good magnetic properties can be obtained under optimized deposition condition.     

Characterization of copper oxide nanolayers deposited by direct current magnetron sputtering

Direct current reactive magnetron sputtering was used to deposit the thin layers of copper oxide (Cu₂O) on glass substrates. A solid disc of pure copper as the target was sputtered in an argon gas under sputtering pressures varying from 0.133 to 4 Pa. The effects of the sputtering power and pressure on the structural and optical properties of Cu₂O thin films were systematically studied. The deposited layers were characterized using X-ray diffraction, atomic force microscopy, profilometry and spectrophotometry. The optical transmission of the films was measured in the visible region. The increase in pressure resulted in a higher growth rate than increasing sputtering power. The increase in power produced Cu₂O thin films that were detrimental to the optical transmission of the films.     

Rotatable magnetron sputtering of aluminium in continuous and high power pulse modes using different strength magnetic arrays

This paper reports preliminary results of industrial size (152 mm target O.D.) rotatable magnetron sputtering of Al target in direct current (DC) and High Power Impulse Magnetron Sputtering (HIPIMS) modes using two standard commercially available magnetic arrays: standard strength array (as used for DC and AC processing) and a lower strength ‘RF’ array [i.e. as used for radio frequency (RF) magnetron sputtering]. A comparison of processes resulted in by combining the different magnetic arrays and power modes is made in terms of magnetic field distribution on the cathode surface, magnetron characteristics, process characteristics and deposition rates.Optical emission spectroscopy (OES) revealed enhanced sputtered Al flux ionisation in the HIPIMS discharge monitored 64 mm away from the target surface when using the ‘RF’ array. Importantly, the results of this work (at the processing conditions investigated) demonstrate that at the same average power the deposition rate of Al using HIPIMS in conjunction with the ‘RF’ array is substantially the same as that obtained for the ‘standard’ strength balanced array and DC power. This indicates that the magnetic field design of the ‘RF’ magnetic array affects favourably the sputtered flux transport perpendicular to the target surface by altering mass transport direction and minimising effects that reduce deposition rate (e.g. ion return effect). Arc rate is also reduced significantly (approximately ten times) if the low strength ‘RF’ array is used.     

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)。     

Enhancement of the crystalline quality of reactively sputtered yttria-stabilized zirconia by oxidation of the metallic target surface

Yttria-stabilized zirconia (YSZ) thin films were fabricated on glass substrates by direct current magnetron reactive sputtering. We found out that the crystalline quality of the YSZ film was improved by an oxidation process of the metallic target surface prior to the sputtering deposition process. It is speculated that, at the initial stage of the sputtering, the sputtered particles from the oxidized target surface form a layer with higher degree of crystallization on the substrate, compared with those particles from the metallic target surface. This crystallized layer can enhance the crystallization of the film deposited subsequently. Other sputtering conditions such as sputtering pressure, oxygen flow rate, substrate temperature, and Y₂O₃ content in the film were investigated, for optimization of the crystalline quality of the deposited YSZ film.     

离轴溅射法中最佳几何参量的预测

为提高磁控溅射薄膜的厚度均匀性,采用理论计算的方法分析了离轴溅射薄膜的厚度分布,结果表明最佳偏心距及对应的有效薄膜尺寸都与靶基距呈线性增大的关系。溅射原子的角分布、溅射环的宽度以及膜厚均匀性要求都会影响该线性关系。针对以上变化因子,本文归纳出了普适的公式,可方便地对实际工作进行指导。     

In-situ analyses on the reactive sputtering process to deposit Al-doped ZnO films using an Al-Zn alloy target

The kinetic energies of generated ions were investigated during the reactive sputtering process to deposit Al-doped ZnO (AZO) films using an Al-Zn alloy target. The sputtering system was equipped with specially designed double feedback system to stabilise the reactive sputtering processes and analysis was performed with a quadrupole mass spectrometer combined with an energy analyser. Negative ions O⁻, O₂⁻, AlO⁻ and AlO₂⁻ with high kinetic energies corresponding to cathode voltage are generated at the partially oxidised target surface, after which some of the ions undergo subsequent charge exchange and/or dissociation. Positive ions O⁺, Ar⁺, Zn⁺ and Al⁺ with lower kinetic energies (around 10 eV) are generated by charge exchange of sputtered neutral O, Ar, Zn and Al atoms, respectively. As the target surface oxidises, cathode voltage decrease, the flux of high-energy negative ions increases and the electrical properties of the AZO degrade by ion bombardment as well as the AZO films that are deposited by conventional magnetron sputtering using an AZO target.     

Stable deposition of silicon oxynitride thin films with intermediate refractive indices by reactive sputtering

The deposition stability of silicon oxynitride thin films with intermediate refractive indices was investigated as a function of argon concentration in the process gas mixture. The silicon oxynitride thin films were deposited by pulsed dc reactive magnetron sputtering in a mixture of argon, nitrogen and oxygen. The refractive indices of the silicon oxynitride thin films gradually decreased with oxygen percentage in the reactive gas mixture when high argon concentrations were used. It is proposed that many silicon atoms were sputtered from the target and reached the substrates in high argon concentrations; consequently, drastic oxidation of the thin films did not occur.     

磁控溅射Ni-Mn-Ga薄膜的磁致应变

采用直流磁控溅射的方法,在NaCl基底上沉积了Ni-Mn-Ga薄膜,对薄膜进行了形貌观察、微区成分及结构分析,并测量了薄膜的磁致应变.结果表明,薄膜表面可见大小不一的团簇颗粒,具有明显的岛状结构,表明Ni-Mn-Ga薄膜的形成为典型的核生长型机制.热处理前的薄膜具有部分非晶存在,热处理后薄膜晶化为多晶形态.无约束薄膜在磁场下呈现负的磁致应变,在1.3T磁场下,其最大应变值可达-0.008%,并且可以完全恢复.