Non-reactive Sputtering Research Articles

Sputter deposition of ultrahard coatings within the system Ti-B-C-N

Ultrahard (hardness greater than 4000 HV 0.05) coatings derived from TiB 2 were investigated as thin, wear-protective coatings for cutting tools. Deposition methods were based on non-reactive as well as reactive sputter deposition employing d.c. magnetron sputtering from TiB 2 targets. Coatings were deposited onto molybdenum, niobium and cemented carbide substrates. Very fine-columned films with an (001)-oriented TiB 2 phase are formed by means of non-reactive sputtering of TiB 2 targets. Coatings deposited reactively in Ar-N 2-C 3H 8 atmospheres exhibit very fine-grained to fracture-amorphous structures. In the case of reactive sputtering in Ar-N 2 gas mixtures a hexagonal TiB 2− x N y phase appears at low N 2 flows. An increase of the N 2 flow results in the formation of an additional phase based on TiN. Reactive deposition in Ar- C 3 H 8 atmospheres leads to the existence of mixed-phase structures with phases based on TiB 2 and TiC. Quarternary films grown in Ar-N 2-C 3H 8 mixtures show multiphase structures consisting of phases based on TiB 2 as well as TiC and TiN. Vickers microhardness measurements on coatings 3 - 5 μm thick on cemented carbide inserts gave the following maximum HV 0.05 values: Ti-B films 4000; Ti-B-N 4800; Ti-B-C 4000; Ti-B-C-N 4200. Stresses were found to be compressive with values up to 4 GPa. The results of scratch tests indicate very good adherence. Ti-B-coated cemented carbide inserts have been tested in the turning of aluminum alloys with promising results.

Radio-frequency sputter deposition of boron nitride based thin films

Thin films (≊2 μm) of boron nitride, titanium boron nitride, and titanium aluminum boron nitride have been grown on molybdenum, niobium, and cemented carbide substrates employing nonreactive as well as reactive rf magnetron sputter deposition from either a BN, a TiN-BN, or a TiN–AlN–BN target. Substrates have been rf biased, with dc potentials up to −200 V. By means of nonreactive sputtering mixed-phase structures with dominant phases B48B2N2 (using a BN target), or B48B2N2 and hexagonal Ti–B–N (using a TiN–BN or a TiN–AlN–BN target) are formed. Reactive deposition leads to the existence of hexagonal BN in all deposition modes. In the cases of Ti–B–N and Ti–Al–B–N films this phase is accompanied by fcc Ti–B–N. SEM cross sections revealed very fine grained to fracture-amorphous film structures. Hardness measurements gave the following maximum HV 0.02 values: B–N films 2800, Ti–B–N films 2750, and Ti–Al–B–N films 1650.

Effect of ion bombardment during growth on the electrical resistivity of magnetron-sputtered carbon films

Thin carbon films were grown by non-reactive sputtering of a graphite target in argon in a d.c. planar magnetron system. The influence of the deposition conditions (negative substrate bias, argon pressure and discharge power) on the resistivity of the films was investigated. The charged particle fluxes to the substrate were characterized by electron-to-neutral and ion-to-neutral arrival rate ratios. The film resistivity was found to vary in a very wide range: ten orders of magnitude. When the negative substrate bias was changed at constant argon pressure and discharge power a maximum of the resistivity was observed around the value of the floating potential. Low energy ion bombardment is a favourable condition for obtaining high resistivity films while the intense electron bombardment leads to the formation of low resistivity graphite-like films. The resistivity of the films deposited on floating substrates was found to increase with increasing argon pressure and decreasing discharge power. Extremely high resistivity (greater than about 10 9 Ωcm) carbon films are obtained by ion-assisted thin film growth at high working pressures and (4– Pa) and relatively low power densities (about 5 W cm -2 or less) and deposition rates (about 5 nm min -1 or less).

Reactive and non-reactive high rate sputter deposition of Tungsten carbide

Tungsten carbide coatings were deposited onto molybdenum and cemented carbide substrates using d.c. and r.f. magnetron sputtering. Tungsten targets were used in reactive (argon plus acetylene) atmospheres and tungsten carbide targets were used in non-reactive (argon) atmospheres. Substrates were r.f. biased with d.c. potentials of up to -1000 V. Sputtering from WC targets produced carbon-deficient mixed-phase structures with β-WC 1- x as the main component. Reactive deposition led to highly disordered W-C films which X-ray studies showed to be almost amorphous. Fractograms revealed very fine-grained to fractured amorphous film structures in all deposition modes. Hardness values higher than 3000 HV 0.05 were reached using non-reactive d.c. sputtering.

Zirconium Nitride Thin-Film Resistors With High Thermal Durability

A ZrN thin-film resistor is proposed as a promising heating resistor for a future thermal printing head used in high-resolution highspeed printing. The ZrN film is prepared by nonreactive sputtering with a hot-pressed ZrN target. The present method is able to control the film characteristics mainly through the nitrogen content in the sputtering atmosphere as well as achieve good reproducible results. Practical films, which have a small resistance change with temperature as well as during aging tests, are provided with resistivities of 0.5 to 5 m <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Omega</tex> .cm. Thermal printing element test pieces with 16-dot/mm resolution are fabricated to examine the thermal durability of the ZrN thin-film resistor when applied to high-speed printing. The results of heat pulse life tests make clear that the elements are applicable to high-speed (a 0.3-ms duration and a 1.0-ms repetition interval) printing of excellent quality and sufficient thermal durability.

Elaboration and characterization of a sputtered copper-stainless steel-amorphous carbon solar selective surface for use in evacuated collectors

A spectrally solar selective surface for use in evacuated tubular collectors has been fabricated by successively depositing: an opaque copper layer, a thin film of stainless steel and an amorphous carbon layer, by non-reactive magnetron sputtering. The obtained material is particularly selective ( α s > 0.90; ϵ(300°C) < 0.05) and stable up to 500°C. All these properties, associated with an easy setting to work allows to consider the use of this selective surface for mass production of high performance evacuated collectors.

New dry etch for Al and Al-Cu-Si alloy: Reactively masked sputter etching with SiF4

A new technique, ‘‘reactively masked sputter etching’’ of Al, is described here. This process can pattern fine lines in Al or in Al-Cu-Si alloy but does not have many of the problems associated with presently available reactive sputter etching methods. The technique combines deposition and etching in the one process; Al2O3, Al, and Al-Cu-Si alloy are etched, while all other materials are coated with a layer of SiOx. This results in essentially infinite (Al/mask) and (Al/substrate) etch rate ratios. In addition, the etch gas contains no Cl, which is a common cause of corrosion and undercut. In effect, the etch combines the advantages of both reactive and nonreactive sputter etching. The gas described here is a SiF4/O2 mixture, and it is shown that additions of most impurity gases have very little effect on the etch. However, water or H2 addition significantly improves the performance of the etch, and typical profiles are shown for a SiF4/O2/H2 mixture with a photoresist masking layer.

CrSi resistive films produced by magnetron-plasmatron sputtering

We investigated the feasibility of plasmatron sputtering for the manufacture of resistive films and produced stable CrSi layers. Non-reactive sputtering is suitable for films with a sheet resistance of below 500 Ω/□. Sheet resistances of up to 1000 Ω/□ were implemented by partially reactive sputtering. The reproducibility of the process was substantially improved by isolating the target space from the condensation space. This was accomplished with a rate-reducing slit diaphragm and spatially separated intakes for the reactive and inert gases. Near-zero temperature coefficients of resistivity and high long-term stability were obtained by a three-step annealing procedure.

A sputtered copper-carbon selective absorbing surface for evacuated collectors

A new sputtered selective surface for use in evacuated collectors is described. The surface, consisting of a graded copper-carbon cermet on a copper base layer, is produced by non-reactive sputtering in argon, and reactive sputtering in argon and acetylene, of a single copper electrode. Optical properties of the surface change slightly after bakeout in vacuum for ≈ 1 h at 500°C. Auger depth profiling of the surface before and after bakeout indicates that diffusion of copper occurs in the film during bakeout. The surface exhibits absorptance 0.94 and emittance 0.04 (at 120°C) in a completely assembled evacuated collector. The requirement of a single sputter electrode results in relatively simple construction and operation of a sputtering for coating batches of glass tubes.

Surface compositional modifications during O+2 bombardment of binary alloys

Surface compositional modifications of binary alloys during 15-keV O+2 bombardment under 45° incidence were studied using Auger electron spectroscopy under ultrahigh vacuum conditions. For A1-Ni, Cr-Ni, Fe-Ni, and Pd-Ni alloys, the reactive preferential sputtering by O+2 causes a surface enrichment of the alloy component which has the smaller metal-oxygen bond energy per metal atom. For Cu-Ni and Ag-Pd alloys, where oxidation by the O+2 beam was slight, the surface compositions after O+2 bombardment were qualitatively similar to those caused by nonreactive preferential sputtering with Ar+.

Graded metal carbide solar selective surfaces coated onto glass tubes by a magnetron sputtering system

A solar selective absorbing surface consisting of mixed iron, chromium, and nickel carbides on copper has been deposited onto 1.5 m long, 22 mm o.d. glass tubes by reactive and nonreactive dc sputtering. Grading the properties of the metal carbide from metal rich at the copper substrate to dielectric at the surface results in solar absorptances ∠93% and emittances ∠4% at 300 K (both properties averaged along the length of a tube). Aging experiments show that absorptances deteriorate slowly at 300°C in vacuum due to diffusion in the graded film. Emittances at elevated temperature for copper and for the selective surfaces deposited onto tubes have been determined using a calorimetric technique.

The dc sputter coating of solar-selective surfaces onto tubes

A device for coating tubes using reactive or nonreactive dc sputtering is described. The coating of glass tubes with a solar selective surface consisting of a layer of metallic carbides on copper is used as an example. Uniformity of thickness and composition are demonstrated. The cylindrical design of the coating equipment and low manufacturing tolerances make this a low-cost system.