High-rate Reactive Magnetron Sputtering Research Articles

Growth and characterization of chromium carbide films deposited by high rate reactive magnetron sputtering for electrical contact applications

Chromium carbide films with different phase contents were deposited at 126±26°C by industrial high rate reactive magnetron sputtering, using both direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). Film structure and properties were studied by SEM, XRD, TEM, XPS, NRA, Raman spectroscopy, nanoindentation, unlubricated reciprocating sliding experiments, and a laboratory setup to measure electrical contact resistance. The films consisted of amorphous a-CrCy, a nanocrystalline minority phase of metastable cubic nc-CrCx, and a hydrogenated graphite-like amorphous carbon matrix (a-C:H). The DCMS and HiPIMS processes yielded films with similar phase contents and microstructures, as well as similar functional properties. Low elastic modulus, down to 66GPa, indicated good wear properties via a hardness/elastic modulus (H/E) ratio of 0.087. Unlubricated steady-state friction coefficients down to 0.13 were obtained for films with 69 at.% carbon, while the electrical contact resistance could be reduced by two orders of magnitude by addition of a-C:H phase to purely carbidic films. The present films are promising candidates for sliding electrical contact applications.

Enhanced Deposition Rate of Photo-Induce Hydrophilic TiO<sub>2</sub> Thin Films Prepared by Pulsed DC Reactive Magnetron Sputtering

Based on recent discovery of high-rate reactive magnetron sputtering, which was a key requirement for production of coating industry, this study focused on enhanced deposition rate of TiO2 films for photo-induce hydrophilic applications. The TiO2 thin films were reactively sputtered, which a pulsed DC source, from high-purity (99.995%) titanium (Ti) target on glass and silicon (100) and wafer substrates. During the deposition, a mesh grid cover was installed on the sputtering source with varying argon gas flow rates. Properties of the TiO2 films were compared between deposition with and without a mesh grid cover. The microstructure of the TiO2 films was studies by grazing-incidence X-ray diffraction (GIXRD) and field-emission scanning electron microscope (FE-SEM). The optical properties were determined by UV-Vis spectrophotometer. The contact angle measurement was used to determine the hydrophilicity of the films after exposing to UV light. For using the mesh grid during film deposition, it was found that the deposition rate of the TiO2 films was increased in oxide mode with a small grain size. In this case, the TiO2 films showed high transparent and good photo-induced hydrophilic properties.

High rate reactive magnetron sputtering of ZnO:Al films from rotating metallic targets

Aluminum doped zinc oxide (ZnO:Al) films were reactively sputtered at a high discharge power from dual rotating metallic targets (Zn:Al = 99.5:0.5 wt.%). Deposition conditions like substrate temperature and working points were varied in order to prepare high quality ZnO:Al films. The influences on electrical and optical ZnO:Al thin film properties and surface texture before and after chemical etching in diluted HCl were studied in order to achieve light scattering films as front contact for solar cells. High dynamic deposition rate close to 90 nm m/min and high Hall mobility of up to 47 cm 2/Vs were obtained. Transmission of more than 85% in the visible spectral range is obtained for all ZnO:Al films in this study. In addition, the absorption in near infrared region is low due to low doping. Surface texture after etching is usually much rougher than before. However, some films reveal after etching small surface features that are similar to initial surface features. We propose a relationship between initial and post-etched surface textures.

Progress in High Throughput Processing of Long-Length, High Quality, and Low Cost IBAD MgO Buffer Tapes at SuperPower

High rate reactive magnetron sputtering at transition mode were developed to deposit Al2O3 and Y2O3 layers at a routine production speed of 750 m/h (all speeds in this paper are the equivalent speed of 4 mm wide tape.) with excellent process stability over kilometer length and from run to run, and with same texture and critical current as our previous ion beam sputtering process. For the IBAD MgO process, a reactive ion beam sputtering process with higher deposition rate and long time stability has been developed and routine production speed has been increased to 360 m/h. The tape driving system has been upgraded from 6 wraps to 11 wraps in our Pilot Buffer system. Homo-epitaxial MgO process has been re-tuned with the routine production speed increased to 340 m/h. The LaMnO3 routine process speed has been increased to 450 m/h by reactive sputtering of a La-Mn alloy target. Throughput was further improved by reducing total buffer process from 5 steps to 3 steps. The routine processing length of single pieces of buffer tape was increased to 1,400 m. The actual production capacity is 500 km/year now. We developed a new Direct LMO process with same Ic as our standard IBAD buffer stack and dramatically increased the yield which makes it a very promising manufacturing process.

High Yield and High Throughput Reactive IBAD MgO Process for Long-length, HTS Wire Production at SuperPower

AbstractSuperPower's IBAD (ion beam assisted deposition) MgO process has been changed to reactive ion beam sputtering of Mg metal target instead of MgO ceramic target, which gives ∼ 60 % increase in deposition rate. The process speed was increased from 195 m/h to 360 m/h. Texture of IBAD MgO tapes by this reactive process was found to degrade faster during long length run. This uniform issue was resolved with feedback control during long run and from run to run. The bottleneck of alumina layer process due to slow ion beam sputtering deposition was removed by new high rate reactive magnetron sputtering at transition mode. The new alumina process speed can be as high as 3,000 m/h in our Pilot Buffer system. The yttria layer process was also changed to high rate reactive magnetron sputtering at transition mode with achievable speed as high as 10,000 m/h in our Pilot Buffer system. The routine production speed of alumina and yttria is 750 m/h due to limitation of tape driving system. The high rate magnetron-sputtered alumina/yttria yields the same texture of IBAD MgO as ion beam sputtered alumina/yttria. Now we are routinely producing IBAD MgO template tapes of ∼ 1.4 km with a uniform in-plane texture ∼ 6-7 degrees. Record high critical current of 813 A/cm over a one meter length and a world record critical current times length value of > 233,8100A-m was obtained with our routinely-produced high throughput IBAD MgO buffers. The requirements for a better IBAD texturing layer than IBAD MgO are also suggested.

Pressure stability in reactive magnetron sputtering

In high rate reactive magnetron sputtering the film deposition results in a substantial pumping rate of the reactive gas. When the depositing film is substoichiometric, the film's consumption of the reactive gas is limited by the arrival rate of that gas and so consumption increases with reactive gas partial pressure. When the film is saturated with gas, the reactive gas consumption is limited by the metal arrival rate. As the reactive gas pressure is increased reaction products form on the target (it is “poisoned”) and the metal flux falls, leading to a decreasing consumption of the reactive gas. At pressures where a stoichiometric film is formed the consumption of the reactive gas by the film will be falling. This can lead to an uncontrollable transition between a metallic and a poisoned target that makes the control of optimum deposition conditions difficult. We have investigated this instability and its causes and our results indicate various means of getting a stable deposition system.

Reactively magnetron sputtered Hf-N films. II. Hardness and electrical resistivity

The microhardness and electrical resistivity have been measured on thin Hf-N films, covering the entire composition range from pure Hf to overstoichiometric HfN. Influence of substrate bias on the properties of stoichiometric HfN films has also been studied. All films have been prepared by high-rate reactive magnetron sputtering at a substrate temperature of 400 °C. Both hardness and resistivity increase as nitrogen is added to the α-Hf phase. For the cubic HfN phase the hardness has a maximum, ≊3500 HV, and the resistivity a minimum, 225 μΩ cm, at a composition close to stoichiometry. However, both values are considerably higher than those reported for bulk samples. This is explained in terms of nonequilibrium growth conditions, giving rise to high densities of dislocations and interstitially incorporated nitrogen atoms. For films with a nitrogen content above 50 at. % a very high-resistivity value is found, 2.0 Ω cm at maximum. By applying a low substrate bias voltage the resistivity of stoichiometric HfN was decreased with a factor of about 3, and simultaneously a grain growth and/or reduced defect concentration was observed. At higher bias voltages the resistivity increases and the grain sizes decrease.