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.     

Deposition of YBCO films on both sides of substrate by magnetron sputtering

We have studied features of the formation of YBa₂Cu₃O_{7 − δ} (YBCO) films on both sides of sub-strates by magnetron sputtering in the on-axis geometry. During sputter deposition onto the first (front) side, a thin film is simultaneously formed on the second (rear) side, which can provide a high-quality sublayer for the final coating of preset thickness deposited at the subsequent stage. It is shown that, by monitoring the properties of a sublayer formed on the rear side of substrate during YBCO layer growth on the front side, it is possible to optimize technological parameters of the process.     

Energy deposition during molecular depth profiling experiments with cluster ion beams

The role of the location of energy deposition during cluster ion bombardment on the quality of molecular depth profiling was examined by varying the incident angle geometry. Cholesterol films approximately 300 nm in thickness deposited onto silicon substrates were eroded using 40-keV C60(+) at incident angles ranging from 5 degrees to 73 degrees with respect to the surface normal. The erosion process was evaluated by determining at each incident angle the total sputtering yield of cholesterol molecules, the damage cross section of the cholesterol molecules, the altered layer thickness within the solid, the sputter yield decay in the quasi-steady-state sputter regime, and the interface width between the cholesterol film and the silicon substrate. The results show that the total sputtering yield is largest relative to the product of the damage cross section and the altered layer thickness at 73 degrees incidence, suggesting that the amount of chemical damage accumulated is least when glancing incident geometries are used. Moreover, the signal decay in the quasi-steady-state sputter regime is observed to be smallest at off-normal and glancing incident geometries. To elucidate the signal decay at near-normal incidence, an extension to an erosion model is introduced in which a fluence-dependent decay in sputter yield is incorporated for the quasi-steady-state regime. Last, interface width calculations indicate that at glancing incidence the damaged depth within the solid is smallest. Collectively, the measurements suggest that decreased chemical damage is not necessarily dependent upon an increased sputter yield or a decreased damage cross section but instead dependent upon depositing the incident energy nearer the solid surface resulting in a smaller altered layer thickness. Hence, glancing incident angles are best suited for maintaining chemical information during molecular depth profiling using 40-keV C60(+).     

Influence of cathode voltage on electrical property and crystal structure of sputter-deposited Ag thin films

The resistivity and crystal structure of Ag thin films were investigated as a function of the cathode voltage during the Ag sputter deposition. Low emissivity (low-e) coatings with a layered construction of glass/dielectric/Ag/dielectric were deposited by magnetron sputtering. It was found that the Ag layers in the low-e coatings showed lower resistivity when lower cathode voltage was applied. Furthermore, the X-ray diffraction measurement revealed that the crystallite of the Ag layer became larger with the decrease of the cathode voltage. It can be seen from these results that the Ag deposition resulting from low cathode voltage contributes to preferred crystal growth of the Ag layer. This improvement of the Ag crystallinity can be explained by the decrease in the kinetic energy of the Ar atoms backscattered on the Ag sputter target surface.     

Monte Carlo simulation of the particle transport process in sputter deposition

The essential features of the transport of sputtered particles from a target to a substrate during sputter deposition were studied by calculation using the Monte Carlo technique. The study takes into consideration the change in momentum as well as the kinetic energy loss of sputtered particles in their collisions with ambient gas molecules, to gain an understanding of the effects of these factors and of the number of sputtered particles arriving at a substrate on the mechanism of growth of a thin film by sputter deposition. Some theoretical predictions using the above calculation were made for several selected conditions of sputter deposition.     

Highly conductive and transparent ZnO:Al thin films prepared on high-temperature substrates by d.c. magnetron sputtering

Highly conductive and transparent aluminium-doped ZnO (AZO) thin films have been prepared on high-temperature substrates using d.c. magnetron sputtering. In AZO films, the spatial distribution of resistivity across substrates placed parallel to the target was improved by deposition at substrate temperatures above 300 °C. AZO films with resistivities of 2−5 x 10⁻⁴ Ω cm were prepared under sputter gas pressures of between 0.6 and 3.0 Pa and at a substrate temperature of 350 °C. In addition, milky AZO films with a textured surface were prepared on high-temperature substrates under sputtering conditions which suppressed the c-axis orientation. A total transmittance of 72% and a haze factor of 63% at a wavelength of 500 nm and a sheet resistance as low as 2.0 Ω sq⁻¹ were obtained in milky AZO films 3 μm thick prepared at a sputter gas pressure of 12 Pa and a substrate temperature of 350 °C.     

磁控过程的计算机模拟

本文基于蒙特卡罗方法,并结合SRIM软件,编制程序跟踪模拟了磁控溅射各物理过程的粒子状态.以铝靶材为例,得到了粒子在磁控溅射各物理过程的状态分布,讨论了工作参数对薄膜沉积过程的影响.模拟结果表明:溅射原子的能量主要分布在20 eV以下,当原子沉积到基片表面时,其能量主要分布在15 eV以下,但有两个分布峰值,两个分布峰值对应着快慢两种不同形式的沉积过程.原子沉积到基片 表面的位置大致服从正态分布,气压p和靶基距离d影响正态分布的方差,也即影响沉积原子在基片表 面分布的均匀性.功率与沉积速度呈良好的线性关系,在工作气压为1 Pa,靶基距离为60mm的条件下,当入射粒子的能量为250 eV时,模拟得到的功率效率最大.     

Radio frequency sputtering and the deposition of high-temperature superconductors

This paper reviews the background to glow-discharge sputter deposition of thin films and the deposition of YBCO superconducting thin films in particular. The background to sputtering is briefly reviewed with reference to the recent literature on analytical and numerical techniques for investigating radiofrequency (r.f.) plasmas, magnetron sputtering and hysteretic behaviour in reactive sputtering. Low-energy, ion-assisted deposition techniques are briefly reviewed, and the effect of ion-beam interactions on film nucleation and growth is also discussed. The background to the sputter deposition of high-temperature superconductors (HTS) is given along with the choice of sputtering system for HTS deposition. Resputtering effects, off-axis andin-situ/ex-situ processing are also discussed. The sputter deposition of YBa₂Cu₃O _x is considered in detail along with theP-T-x oxidation conditions and the tetragonal/orthorhombic line. Typical experimental arrangements and results for YBCO sputtered onto SrTiO₃ and MgO are given. The problem of producing high-critical-current-density polycrystalline films by sputtering is also discussed.     

Use of the ring gap plasmatron for high rate sputtering

The application of ring gas plasmatron discharges for high rate sputtering using a model PPS-5 planar plasmatron sputter source is discussed. Characteristic sputter rates of the order of 0.1 g min^-1 kW^-1, i.e. rates similar to those of electron beam evaporators with water-cooled crucibles, are obtained. The working pressure giving the highest sputter rates is 0.5 Pa but discharge pressure levels down to about 0.07 Pa are possible. Any damage to the substrates is prevented by the underlying discharge mechanism, especially by the low energy charge carriers in the plasma and the concentration of the latter on the target. In addition, carrier impingement on the substrates can be avoided without difficulty.When using the plasmatron for sputtering, the specific energy expended is about three times lower than that expended with conventional sputtering techniques, e.g. with diode sputtering. With bias sputtering, the PPS-5 planar plasmatron sputter source (at a discharge power of 5 kW) gives a bias current of approximately 1 A even at a substrate bias voltage of only a few volts.Typical performance parameters of the high rate sputter source are a discharge voltage of 500 V, a discharge current of 10 A, a sputter rate for copper in argon of 0.7 g min^-1 and, at a distance of 50 mm, a condensation rate of 25 000 Å min^-1.     

Effects of sputtering power on mechanical properties of Cr films deposited by magnetron sputtering

Abstract

Chromium (Cr) films were deposited on plain carbon steel sheets by dc and rf magnetron sputtering as well as by electroplating. Effects of dc or rf sputtering power on the deposition rate and properties such as, hardness, adhesion strength, surface roughness and corrosion resistance of the Cr films were investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microcopy (SEM) analyses were performed to investigate the crystal structure, surface roughness, thickness of the Cr films. Salt fog tests were used to evaluate the corrosion resistance of the samples. The deposition rate, hardness and surface roughness of the Cr film deposited by either dc or rf sputtering increase with the increase in sputtering power but the adhesion strength is nearly independent of the sputtering power. The deposition rate, hardness and adhesion strength of the Cr film deposited by dc sputtering are higher than those of the Cr film deposited by rf sputtering, but rf sputtering offers smoother surface and higher corrosion resistance. The sputter deposited Cr film is harder and has a smoother surface than the electroplated one. The sputter deposited Cr film also has higher corrosion resistance than the electroplated one, which may be attributed to the smoother surface of the sputter deposited film.     

磁控溅射制备硅铝阻隔膜的研究

采用磁控溅射技术以10%Si～90%Al合金为靶材,通入O2将Si氧化成SiO2,Al氧化成Al2O3,在普通PET薄膜表面制备具有高阻隔性无机阻隔薄膜层,以增加其阻隔性.传统的磁控溅射法制备SiO2膜工艺,大多采用射频溅射法,但其成本较高,效率较低,无法充分满足大面积工业化镀膜生产的需要.而采用10%Si～90%Al合金不仅可以实现直流溅射工艺,而且测量结果表明,薄膜的阻隔性得到大幅度提高.     

蒸发、磁控溅射沉积真空对铀薄膜组成和结构的影响

用 X-光电子能谱仪(XPS)、扫描透射电镜(STEM)分析了蒸发、磁控溅射沉积真空对铀薄膜组成和结构的影响。结果表明,在沉积真空2Pa 下,蒸发、磁控溅射沉积的铀薄膜已完全氧化;在沉积真空2×10~(-1)Pa 下,磁控溅射沉积的铀薄膜由金属铀和二氧化铀组成,薄膜呈微晶或无定形结构。     

Influence of temperature on magnetic properties of ion-beam sputter-deposited perpendicular magnetic media

Co-Cr perpendicular magnetic media deposited by ion-beam sputter methods show magnetic properties similar to those obtained by radio frequency (RF) sputtering. Coercivity, ratio of perpendicular to parallel squareness, and X-ray orientation are strikingly improved when the substrate is heated. Independent control of substrate temperature makes ion-beam sputter deposition an attractive candidate for deposition of perpendicular magnetic films.     

Sputter deposition of self-organized nanoclusters through porous anodic alumina templates

Silver nanoparticles were sputter deposited through self organized hexagonally ordered porous anodic alumina templates that were fabricated using a two-step anodization process. The average pore diameter of the template was 90 nm and the interpore spacing was 120 nm. Atomic force microscope studies of the sputter-deposited silver nanoparticle array on a Si substrate indicate an approximate replication of the porous anodic alumina mask. The nature of the deposition depends strongly on the process parameters such as sputtering voltage, ambient pressure and substrate temperature. We report a detailed study of the sputtering conditions that lead to an optimal deposition through the template.     

Epitaxial growth of rhenium with sputtering

We have grown epitaxial Rhenium (Re) (0001) films on α-Al₂O₃ (0001) substrates using sputter deposition in an ultra high vacuum system. We find that better epitaxy is achieved with DC rather than with RF sputtering. With DC sputtering, epitaxy is obtained with the substrate temperatures above 700 °C and deposition rates below 0.1 nm/s. The epitaxial Re films are typically composed of terraced hexagonal islands with screw dislocations, and island size gets larger with high temperature post-deposition annealing. The growth starts in a three dimensional mode but transforms into two dimensional mode as the film gets thicker. With a thin (∼2 nm) seed layer deposited at room temperature and annealed at a high temperature, the initial three dimensional growth can be suppressed. This results in larger islands when a thick film is grown at 850 °C on the seed layer. We also find that when a room temperature deposited Re film is annealed to higher temperatures, epitaxial features start to show up above ∼600 °C, but the film tends to be disordered.     

Moisture-resistant MoS2-based composite lubricant films

The moisture resistance of sputter-coated composite films of MoS₂ can be markedly increased when the MoS₂ is sputter deposited with water-repellent additives. To increase the adhesion of such coatings and to prevent corrosive attack of the substrate, generally steel, a thin corrosion-resistant sulphide-forming intermediate layer is applied previously on the functional surface and serves as an interlayer.With a sputtering process coatings of these lubricants, which are durable in the Earth's atmosphere and adhere well to their support, are obtained. Friction and wear results for such composite lubricant films on different interlayers and various substrates, which were obtained in dry and humid air from pin and disc experiments and from functional bearing elements of precision engineering systems, confirm the improvements.     

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.     

Magnetron sputter‐deposition on atom layer scale

For many applications there is an increasing request to control the deposition process on an atom layer scale. This offers a lot of advantages like in accuracy, layer homogeneity and tailoring of layer properties. On the other hand the speed and throughput of the process should not suffer from the control on an atom layer scale as it is the case for classical atom layer deposition (ALD). For optical applications especially high‐end interference filter coatings we developed a plasma assisted reactive magnetron sputtering process in combination with a high speed drive for the substrates. This combination allows controlling the layer thicknesses and layer properties on an atom layer scale while maintaining a high deposition rate. The advantages of this process are demonstrated on single layer results of SiO2, HfO2, ZrO2, Ta2O5 and mixed oxides of SiO2‐Nb2O5. Morphology, surface roughness, film stress, refractive index and losses are controlled by the oxygen partial pressure, the substrate temperature, the energy input by the sputtering ‐and assist process and by cosputtering. The outstanding performance of high‐end interference filter coatings like a multi notch filter for fluorescence microscopy is achieved by the very stable and reproducible deposition process in combination with an advanced thickness control strategy based on in‐situ optical thickness control and time control.     

TEM characterization of Co-Al-O nano-granular TMR film

Co-Al-O film was fabricated using the reactive r.f. magnetron sputtering technique. A maximum magnetoresistance (MR) of approximately 7% was established through optimizing the sputter deposition conditions such as sputter power and gas flow rate. TEM characterization of the film revealed a nano-granular structure that consisted of ferromagnetic grains with grain diameters on the order of several nm together with non-magnetic grain boundary layers with the thickness on the order of less than 1 nm. The large MR was attributed to electron tunneling thorough this very thin grain boundary layer between individual ferromagnetic grains.