Magnetron Cathode Research Articles

Measurement of ionic and neutral densities in amplified magnetron discharges by pulsed absorption spectroscopy

Resonant absorption diagnostic has been used to estimate densities of neutral and ionic titanium, both in ground and metastable states, in a rf coil amplified magnetron sputtering process. The conventional optical source dc supply has been replaced by a high voltage pulsed power supply to allow absorption experiments onto ionic and neutral species, in a broad range of discharge conditions (500 W are applied onto the magnetron cathode and 0–500 W on the rf coil, for a 30 mTorr argon pressure). The obtained densities are used to compare the magnetron and the amplified discharges. The total ionization degree of the metallic vapor is found to increase from ∼3% in the magnetron regime to ∼24% in the amplified magnetron discharge. The Ti (a5F) neutral metastable density is found to be partially enhanced when the rf coil is power supplied.

Improved film deposition of carbon and carbon nitride materials on patterned substrates by ionized magnetron sputtering

This work is mainly devoted to the study of thin film deposition by ionized magnetron sputtering (IMS). This process is based on a standard magnetron cathode sputtering deposition assisted by an induced r.f. discharge generated by an r.f. powered coil (antenna), placed between the substrate and the cathode (target). A very different deposition behavior is obtained compared to a classical magnetron process. We have used IMS for carbon and carbon nitride deposition in order to improve the relatively low deposition rate obtained by magnetron sputtering. In this paper, the ability of IMS to fill holes and trenches of micronic and sub-micronic size with amorphous carbon and carbon nitride films is particularly studied. Several patterns realized onto silicon substrates have been used: holes and trenches of different width. In particular, the influence of the substrate bias voltage is studied by determining the deposition rate at the top and the bottom of the holes and trenches. Moreover, the investigation by scanning electron microscopy of the film morphology has revealed the growth of original structures.

Ion source with a cold magnetron cathode and magnetic plasma compression

The operating principles, design, and characteristics of an ion source with a cold magnetron cathode and magnetic plasma compression are described. The source is intended for the injector of a linear proton accelerator.

New type of plasma reactor for thin film deposition: magnetron plasma process assisted by microwaves to ionise sputtered vapour

A new type of plasma reactor for thin film deposition has been designed: a magnetron-sputtering device assisted by microwave applicators to ionise the sputtered vapour of the magnetron. Ionizing the vapour has several advantages: improvement of the film quality, deposition on substrates with complex shapes, enhancement and control of the reactivity. The reactor consists of a planar rectangular magnetron cathode (22 cm×9 cm) and of two coaxial-type microwave applicators located perpendicularly to the substrate–magnetron axis, on both sides of the sputtered vapour flow. This reactor can operate on a wide pressure range: from 0.2 to 60 Pa. Several in-situ diagnostics have been performed to characterise the process in argon gas with chromium and titanium targets. Electron density of the order of 10 11–10 12 cm −3 and electron temperature of 1.5–2 eV were measured in the microwave plasma by a cylindrical Langmuir probe; emission of metallic ions (Cr +, Ti +) was clearly identified when the microwave plasma is turned on; concentration of Cr or Ti atoms was measured by absorption spectroscopy, a decrease of this concentration is observed when the microwave power is increased. Characterisation of thin titanium films was performed ex-situ by Rutherford backscattering spectroscopy (RBS) for Ti content and nuclear reaction analysis (NRA) for oxygen contamination. Film density was deduced from RBS and NRA measurements and X-ray reflectometry. Oxygen contamination in the film is clearly decreased when microwave plasma is turned on and with a bias applied to the substrate.

Electrochemical behavior of the Ti–6Al–4V alloy coated with a-C:H films

In this work diamond-like carbon films were deposited on the Ti–6Al–4V alloy, which has been used in aeronautics and biomedical fields, by electrical discharges using a magnetron cathode and a 99.999% graphite target in two different atmospheres, the first one constituted by argon and hydrogen and the second one by argon and methane. Films deposited using the argon/hydrogen mixture were called a-C:H, while films deposited using the argon/methane mixture were called DLC. Raman spectroscopy was used to study the structure of the films. The Raman spectra profile of the a-C:H films is quite different from that of the DLC films. The disorder degree of the graphite crystalline phase in a-C:H films is higher than in DLC films (a-C:H films present small values for the the I D / I G ratio). Potentiodynamic corrosion tests in 0.5 mol l −1 NaCl aqueous solution, pH 5.8, at room temperature (≈25 °C) were carried out as for the a-C:H as for the DLC coated surfaces. Comparison between the corrosion parameters of a-C:H and DLC coated surfaces under similar deposition time, showed that DLC coated surfaces present bigger corrosion potential ( E corr) and polarization resistance than those coated with a-C:H films. Electrochemical impedance spectroscopy (EIS) was also used to study the electrochemical behavior of a-C:H and DLC coated surfaces exposed to 0.5 mol l −1 aqueous solution. The EIS results were simulated with equivalent electrical circuit models for porous films. The results of these simulations showed similar tendency to the one observed in the potentiodynamic corrosion tests. The DLC film resistance and the charge transfer resistance ( R ct) for the DLC coated surface/electrolyte interface were bigger than the ones determined for the a-C:H coated surfaces.

Determination of Ti+-flux and Ar+-flux of ionized physical vapor deposition of titanium from multiscale model calibration with test structures

In this article we determine physical parameters characterizing the ionized physical vapor deposition of titanium in a Hollow Cathode Magnetron by comparing experimental results obtained from suitable submicron test structures with a multiscale model. The model includes the reactor scale, the plasma sheath and presheath scale, and the feature scale. The reactor scale model delivers the energy and angular distribution of the neutral sputtered particles from the reactor geometry and an energy dependent collision model. The sheath and presheath model calculates the energy and angular distribution of the ions from the reactor model and a subsequent scattering model describes collisions in the presence of magnetic fields. The levelset-based feature scale simulator propagates the front according to local growth velocities which are calculated from Monte Carlo particle flux and reaction kinetics (derived from molecular dynamics calculation). The calibration is performed in two steps with help from bottle-shaped test structures as well as technologically relevant structures. First, hi-fill and ultra-hi-fill magnetron sputter processes of titanium are investigated in order to verify the transport model for the neutral particles. Second, a Hollow Cathode Magnetron sputter process of titanium is analyzed in order to verify the transport model for postionized particles. This analysis is performed for a floating substrate process and a process with rf-driven substrate bias. The postionized flux fraction of titanium in this technology is not calculated from a plasma model but treated as a free parameter. The prediction of the model and the comparison with the experimental data allow us to determine this value as 0.7±0.1 under a standard condition. The ionized flux of argon relative to the ionized flux of titanium is determined as 2. The results show that the bottom and sidewall coverage of the process depends significantly on the angular dependence of the ionized component which is essentially a result of processes in the presheath. The validity of the model covers a variety of plasma and process conditions. It can be applied to other reactor concepts and materials.

A cross-corner effect in a rectangular sputtering magnetron

Electron trajectories, ionization distribution, and magnetic field in a conventional rectangular sputtering magnetron cathode are simulated in order to understand the mechanism of a cross-corner effect, which is a common phenomenon associated with rectangular magnetron cathodes and which limits the target utilization. It is found that once the magnetic field in end region of the cathode is different from that in straightway, the cross-corner effect exists. Using a fourth-order Runge–Kutta method, the electron trajectories are simulated, showing that the electrons may drift much faster in the end region than in the straightway and pass quickly to cross-corner region. A Monte-Carlo method is employed to simulate ionization distribution and to quantitatively predict target erosion. The results show denser ionization in the cross-corner region, causing more intensive erosion in that area. We demonstrate that by properly modifying the magnet field in the end region, the electron drift velocity and ionization distribution can be controlled and the cross-corner effect may be significantly reduced.

Impedance Control of Reactive Sputtering Process in Mid-Frequency Mode with Dual Cathodes to Deposit Al-Doped ZnO Films

Aluminum-doped zinc oxide (AZO) films were deposited on glass substrates at 300°C by reactive mid-frequency (mf, 50 kHz) magnetron sputtering using dual magnetron cathodes with aluminum–zinc alloy targets. In order to keep the very high deposition rate stable in the transition region of the reactive sputtering system, the reactive gas (O2) flow was controlled using the “discharge impedance feedback system”, where the discharge current value was used to control the O2 flow. The highest deposition rate for the transparent conductive AZO films achieved by this dual magnetron sputtering (DMS) system was 242 nm/min, which was higher by one order of magnitude than that achieved by the conventional reactive sputtering system. The lowest resistivity of the AZO film obtained by such a high deposition rate was 4.4×10-4 Ωcm. The structure and electrical properties of the films varied systematically by controlling the discharge current in the transition region using this system.

1210 超電導バルク磁石を用いたスパッタガンの開発

We fabricated large single-domain Sm-Ba-Cu-O bulk superconductors 60mm in diameter, which can trap magnetic fields exceeding 2 T at 77 K. We have proposed the construction of a superconducting bulk magnet (SBM) system by using the extremely powerful bulk superconductor cooled by a refrigerator. As one of promising applications, we have constructed a magnetron sputtering device by replacing a conventional Nd-Fe-B permanent magnet with an SBM. In our system, the magnetic field parallel to the target surface reached 0.6 T, which is more than ten times stronger than that of a conventional magnetron cathode. This strong magnet field enabled us to deposit films from various targets including a 3mm thick Fe at pressures lower than 1×(10)^<-2> Pa. To the best of our knowledge, the present magnetron sputtering is the only one which can be operated under such a low pressure range. For example, plasma damage-free films can be prepared by extending the target to substrate distance to 30-50cm, since the mean free path of sputtered particles becomes so long that they can reach the substrate without involving repeated collisions during their flight.

Rapid chemical and structural characterization of metastable thin‐film libraries by a combination of electron probe microanalysis and scanning x‐ray diffraction

AbstractThe increasing complexity of modern coatings leads to the demand for a cost‐effective tool for the development of new products in the advanced materials industry. One possible approach to this question is the adaptation of combinatorial methods to the specific requirements of the coatings industry.In this paper, the deposition and characterization of two‐dimensionally laterally graded (Ti,Al,Si)N hard coatings deposited by a triple cathode magnetron sputtering arrangement is presented. The three cathodes, equipped with aluminium, silicon and titanium targets, respectively, were adjusted at a low angle to the surface. Additionally, a system of apertures was mounted between the cathodes. The relation between composition and structure of the resulting materials library was investigated by a combination of electron probe microanalysis (EPMA) and scanning x‐ray diffraction. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Aluminum oxide films deposited in low pressure conditions by reactive pulsed dc magnetron sputtering

The reactive pulsed dc sputtering technique is widely used for the deposition of oxide films. The operating pressure for sputtering is commonly above 0.13 Pa. In this study, however, aluminum oxide (alumina) films were deposited at operating pressures from 0.06 to 0.4 Pa using a sputtering system equipped with a scanning magnetron cathode and a pulsed dc power supply. The pulsed dc power was found to be useful not only to reduce arcing, but also to sustain the discharge at low pressure. The electrical breakdown field, intrinsic stress, O/Al ratio, refractive index, and surface roughness were investigated. Both a low intrinsic stress and an O/Al ratio around the stoichiometry were required to get the film having a high breakdown field. A low operating pressure of 0.1 Pa was found to provide the necessary stress and O/Al ratio targets. A 50-nm-thick alumina film having a maximum breakdown field of 7.4 MV/cm was obtained.

Effects of gas pressure and r.f. power on the growth and properties of magnetron sputter deposited amorphous carbon thin films

We discuss the effects of both the electrical power supplied to an r.f. magnetron discharge and the Ar gas pressure on the growth of amorphous carbon (a-C) films on silicon substrates by sputtering of a graphite target. The power applied to the magnetron cathode was provided in a continuous wave mode as well as in a pulsed mode where the amplitude of the r.f. signal was square-wave modulated. In the continuous wave deposition mode the power was varied from 100 to 300 W at a fixed pressure of 0.2 Pa, and the pressure from 0.2 to 2 Pa at a constant power of 300 W. The pulsed mode processes were performed by varying the r.f. peak power from 200 to 400 W at 100 Hz of modulating frequency and 20% of duty cycle. At 0.2 Pa pressure the deposition rate increased from 1 to 6 nm/min with increasing power, and decreased to 2 nm/min as pressure was increased up to 2 Pa. The compressive stress was approximately 3 GPa for films grown at low pressure and low power, and decreased below 1 GPa at higher pressure or power. Raman analysis revealed that increasing pressure favours the growth of a-C films with more disordered sp2 domains, whereas the increase in r.f. power first leads to a reduction and then to an increase in the number and clustering of sp2 sites into ordered rings. The friction coefficient measured using a ball-on-disk tribometer ranged between 0.1 and 0.2, being the films deposited at higher power levels that possessed the lowest values. These results were discussed in terms of the effects induced by pressure and power on the energy and flux of the species impinging the film-growing surface.

Effects of ion flux on the properties of dc magnetron-sputtered stainless steel films

We have studied the effect of ion flux on the properties of sputtered stainless steel films. To investigate the effect of ion flux, films have been deposited onto glass substrates using dc planar magnetron-sputtering apparatus, which is equipped with an external magnetic coil. As the external coil current changes, the magnetic field of the magnetron cathode changes from balanced to unbalanced mode smoothly. Targets used were commercial SUS304 and SUS310S steel disks. The applied dc power and Ar pressure were kept constant at 140 W and 0.5 Pa, respectively. The difference of the composition between as-deposited films and the target material appeared to be small. Films deposited using SUS304 target showed a bcc structure with (1 1 0) preferred orientation though the target material was metastable, austenitic stainless steel. When SUS310S steel with stable austenite was used as target material, as-deposited films consisted of a mixture of fcc and bcc phase. The ion flux showed very small effect on the structure and the composition of deposited SUS304 films. In the SUS310S films, however, the ion flux affected the volume ratio of fcc to bcc phase. Both films were superior in the corrosion resistance and the hardness as compared with bulk material.

Al-Doped ZnO Films Deposited by Reactive Magnetron Sputtering in Mid-Frequency Mode with Dual Cathodes

Aluminum-doped zinc oxide (AZO) films were deposited on heated (300°C) glass substrates by reactive mid-frequency (mf, 50 kHz) magnetron sputtering using dual magnetron cathodes with aluminum–zinc alloy targets. In order to keep the very high deposition rate, reactive gas control using plasma emission was carried out to stabilize the discharge in the “transition region” of the reactive sputtering system. The highest deposition rate for the transparent conductive AZO films by this dual magnetron sputtering (DMS) system was 290 nm/min, which was higher than that for the conventional reactive sputtering system by one order of magnitude. The lowest resistivity of the AZO film was 3.9×10-4 Ω cm. The structure and electrical properties of the films could be controlled systematically by the reactive gas control system in the transition region.

Preparation of B-C-N Films by RF Magnetron Sputtering.

B-C-N films were prepared on single crystal silicon substrates by RF magnetron sputtering using a composite target of diamond and cBN powder. The target was mounted on a RF magnetron cathode, then sputtered by nitrogen and hydrogen gases. The hardness of the B-C-N film increased with increasing hydrogen flow rate, corresponding to a maximum at 10 cm3/min, followed by a drop above 30 cm3/min. The film was stable for a long time when it was deposited at the substrate temperature of 500°C. Auger electron spectroscopy and elastic recoil detection analysis revealed that the carbon content in the B-C-N film decreased with increasing the substrate temperature. Furthermore the B-C-N film didn't show the significant weight change under the heat treatment test at 500°C in the air, and the hardness of the B-C-N film remained constant up to 500°C, whereas the DLC films were disappeared after the test at 500°C. These results suggest that the B-C-N film has the potential to be applied to the tribological coatings under relatively high temperature conditions.

Deposition of Multilayers Using Fast Switching Triple Ring Magnetron Cathode

Magnetic Co/Pd superlattices have been sputter deposited using special triple concentric ring magnetron cathode. Magnetic layer properties are investigated as function of argon/krypton sputter gas pressure and of Co layer thickness showing maximum coercivity at 0.2 nm Co thickness. Coercivity is approximately linear function of sputter pressure with highest value of 7 kOe at 40μbar Kr. Special software to control sputter time and power allow deposition times of less than 0.1 s for an individual layer of the superlattice. Power ratio dependent co-sputtering of two cathodes enables preparation of stoichiometrically varying TbFeCo layers giving therefore a tool for efficient investigations of magnetic properties on layer composition.

Cylindrical hollow magnetron cathode. Al–N selective coatings for solar collector absorbers

Hollow magnetron cathodes are particularly useful in coating parts with cylindrical symmetry and when deposition must be centripetal; this is the case when coating the outside of tubular and long substrates. A hollow magnetron cathode and its vacuum system has been designed and constructed to coat 2 m long heat pipe absorbers and fluid pipe absorber tubes with a selective film of aluminum nitride. The pipe absorbers will be used in vacuum and non-vacuum compound parabolic concentrators (CPC) of different models for thermal solar collectors. The long copper substrates are displaced through the DC reactive glow discharge inside the hollow cathode. Coating occurs in a single run. Adequate values of discharge voltage and pressure were chosen and the relative nitrogen dose was optimized to get maximum absorbance of the film in the solar spectrum for several substrates. Reflectivities of less than 1% at the wavelength of 550 nm and excellent adhesion were obtained. In these last tests the pull method has been used.

Argon temperature and density versus the input power in a high pressure planar magnetron discharge

Experimental and theoretical studies of sputtered atoms transport, between target and substrate, give some understanding about the behaviour of the deposition rate in magnetron cathode glow discharges. The present work refers to an experimental study about the dependence of deposition rate, R, on pressure, in an Ar magnetron discharge on a Cu target, at a pressure range extending from 10 to 67 Pa. The experimental results show that R is inversely proportional to pressure, supporting the predictions of a diffusive model for the transport of the sputtered atoms, from the cathode to the substrate, proposed by Helmer and Wickersham. From the results and extending that model, the argon temperature and density, as well as the mean free path of target atoms in the region between cathode and substrate, have been obtained as a function of discharge power.

Influence of high power densities on the composition of pulsed magnetron plasmas

The application of high power pulses with peak voltage of −2 kV and peak power density of 3 kW cm −2 to magnetron plasma sources is a new development in sputtering technology. The high power is applied to ordinary magnetron cathodes in pulses with short duration of typically some tens of microseconds in order to avoid a glow-to-arc transition. High plasma densities are obtained which have been predicted to initiate self-sputtering. This study concerns Cr and Ti cathodes and presents evidence of multiply charged metal ions as well as of Ar ions in the dense plasma region of the high power pulsed magnetron discharge and a substantially increased metal ion production compared to continuous magnetron sputtering. The average degree of ionisation of the Cr metal deposition flux generated in the plasma source was 30% at a distance of 50 cm. Deposition rates were maintained comparable to conventional magnetron sputtering due to the low pressure of operation of the pulsed discharge—typically 0.4 Pa (3 mTorr) of Ar pressure was used. Observations of the current–voltage characteristics of the discharge confirmed two modes of operation of the plasma source representing conventional pulsed sputtering at low powers (0.2 kW cm −2) and pulsed self-sputtering at higher powers (3 kW cm −2). The optical emission from the various species in the plasma showed an increase in metal ion-to-neutral ratio with increasing power. The time evolution within a pulse of the optical emission from Ar 0, Cr 0, Cr 1+, and Cr 2+ showed that at low powers Cr and Ar excitation develops simultaneously. However, at higher powers a distinct transition from Ar to Cr plasma within the duration of the pulse was observed. The time evolution of the discharge at higher powers is discussed.

Characterization of Ge–Sb–Te thin films deposited using a composition-spread approach

Ge–Sb–Te Thin films for rewritable phase change optical data storage applications were deposited by magnetron sputtering using a composition-spread approach. The deposition took place in an UHV chamber by cosputtering of three magnetron cathodes equipped with pure Ge-, Sb- and Te-targets in a DC–argon plasma. To investigate the influence of the chemical composition of the phase change material on its optical properties, films with lateral compositional gradients of up to 30 at.% were deposited. The composition, binding states and structure of the films were investigated by EPMA mappings, XPS, AES, RHEED and GIXRD on plain Si wafers, whereas the phase change velocity of Ge–Sb–Te was determined on Si–Al–SiO 2 stacks. The change between amorphous and crystalline phases of the films was induced and characterized with a static tester consisting of an optical microscope with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity photo detector. Depending on the composition, the duration for the initial crystallization was determined between 220 and 500 ns, while the re-amorphization required between 20 and 120 ns. Structural analyses proved the existence of two crystalline phases with cubic and hexagonal structure in the initialized films.