Rf Diode Sputtering System Research Articles

Formation process of Ni–N films by reactive sputtering at different substrate temperatures

Ni–N thin films are prepared by reactive sputtering in an rf diode sputtering system. Deposition parameters, such as nitrogen flow ratio, substrate temperature and substrate holder potential were changed and their effects were investigated. When the substrate was heated at 220°C, Ni and Ni 3N phases were observed by XRD. In the case of substrate temperature being room temperature (RT), Ni 2N phase also appeared and characteristic nitrogen incorporation into Ni lattice was seen. In addition, when the substrate holder was set to the float potential, nitrogen content of the film which is thought to be lower than the case of ground potential, caused stronger resputtering effect. Because it was observed that the formation phase and nitrogen content of the film depend on the substrate temperature, the nitrogenizing reaction on the deposit surface was considered to rule the film formation. This was also supported by the results on the target surface analysis after sputtering and plasma emission spectroscopy measurements.

Preparation and properties of Pb(Zr, Ti)O 3 thin films deposited on Ir electrodes using a sputtering apparatus

Pb(Zr, Ti)O 3 films were prepared on Ir/SiO 2/Si substrates at the substrate temperatures from 450°C to 600°C by a conventional rf diode sputtering system using a ZrTi+ xPbO composite target. X-ray diffraction analysis showed that the crystallinity of films deposited with a ZrTi+24% PbO target was better than that of films deposited with a ZrTi+30% PbO target. The dielectric properties of the PZT films deposited on an Ir/SiO 2/Si substrate at 600°C with a ZrTi+24% PbO target with Au top electrodes were evaluated before and after the annealing at 400°C 10 min in an O 2 atmosphere. The value of remanent polarization obtained from the P– E hysteresis loop characteristics improved from 4.2 μC/cm 2 before annealing to 16.2 μC/cm 2 after annealing at an electric field of 180 kV/cm. The Ti buffer layer improved the crystallinity and/or microstructure of the PZT and Ir films, as evaluated by X-ray diffraction analyses, and reduced the leakage current of the PZT thin films.

Control of the preferred orientation of AlN thin films by collimated sputtering

The effects of collimation on the crystallographic orientation of sputtered aluminum nitride thin films have been studied. The AlN films were deposited on glass at a total gas pressure of 15 mTorr using a rf-diode sputtering system. Collimators with angular widths varying from 31° to 140° were used to decrease the range of impingement angles of the flux of species sputtered and reflected from the sputtering target that arrive on the film surface. The three-dimensional crystallographic orientation of the films was studied by the x-ray pole figure method. All the AlN thin films were deposited under similar conditions, with and without collimators, and produced polycrystalline structures with the c-axis (0001) direction perpendicular to the substrate surface. A comparison of the films’ preferential orientations showed that, as the angular width of the collimator decreases, the full width at half maximum (FWHM) of the χ scan profile of the 0002 diffraction peak decreases linearly, indicating a better alignment of the crystallites in the collimated samples. For a film deposited with a collimator of angular width of 31°, the FWHM is 16°, compared to 33° for a noncollimated deposited film under otherwise identical conditions. For films deposited with a rectangular collimator, crystallites orient in an asymmetric distribution which is directly related to the asymmetry of the collimator opening.

Carbon nitride thin films prepared by reactive sputtering: Elemental composition and structural characterization

Amorphous carbon nitride thin films (a-CNx) have been deposited onto Si (100) substrates by using a rf diode sputtering system. The films were deposited in reactive nitrogen-argon atmospheres. The partial pressure of nitrogen ranged from 0% to 100% at two different deposition pressures (Pd=2 Pa and Pd=8 Pa). The film composition was determined by ion beam techniques: Rutherford backscattering spectrometry and nuclear reaction analysis. The relative amount of carbon and nitrogen in the films is nearly independent of the nitrogen partial pressure in the reactive plasma. The maximum nitrogen content is 48 at. %. The structural characterization was performed by means of Raman and infrared spectroscopies. Raman spectra revealed the presence of the D and G bands, typical of disordered carbon based materials, and a third band, at about 680 cm−1, also attributed to film disorder. Infrared spectroscopy results showed the D and G Raman bands, IR allowed due to the nitrogen incorporation in the carbon network, the presence of a band at 2220 cm−1 due to C≡N bonds, and a broadband at 3300 cm−1 that can be attributed to the O–H stretching of water molecules absorbed in the films’ voids. A linear correlation between the density and the internal stress of the films was also determined and the maximum values of the film density and the mechanical internal stress were measured for films deposited at 50% of nitrogen partial pressure (Pd=8 Pa).

Surface nanostructure and its relation to deposition conditions of thin carbonaceous films as measured by an atomic force microscope

Hard carbonaceous films (a-C:H) were grown by dissociating butane in an RF-diode sputtering system. The effects of dilution of the butane with argon, target bias, and deposition time on surface structure and final film thickness have been monitored by means of an atomic force microscope with lateral force capability and by Tolansky interference microscopy.

スパッタビーム法によるFe膜の結晶構造と磁気特性

Film deposition by means of a beam of sputtered particles was studied. The sputtered particles are ejected from a sputtering chamber and deposited on a substrate in another evacuated chamber. The method makes uses of the gettering effect of high-rate sputtering, together with a cold-wall effect that suppresses desorption of impure gases from chamber walls. The crystal structure and magnetic properties of Fe films thus deposited were studied. The films exhibit higher crystal growth, higher electrical conductivity, and lower coercivity than films deposited by a conventional RF diode sputtering system. These results suggest that, by further improvement of the system, the method may be applied to the production of various multi-element single-crystal films of high quality.

Deposition Rate Monitoring using Laser Induced Fluorescence

ABSTRACTUltra thin films (< 10 nm) prepared using sputtering or other deposition techniques are becoming more technologically important, with promise of increased importance in the future, particularly in certain magnetic structures. For example, giant-magnetoresistive structures may incorporate individual layers having a thickness < 1 nm. Such a small thickness is commonly associated with relatively short deposition times (∼10 s) and may place limits on the reproducibility and accuracy of the conventional techniques for in situ thickness monitoring or integrated rate monitoring. Experiments have been performed to use laser induced fluorescence (LIF) as a rate monitoring technique for ultra thin films. An RF diode sputtering system was combined with a YAG-pumped, frequency-doubled dye laser to monitor the deposition rale of copper over a range of conditions. When coupled with an absolute calibration reference, the LIF signal gave a reproducible, well-behaved output over a range of pressure and temperature. The technique is potentially advantageous for depositions where rapid (∼1 s) measurements are needed. LIF is also projected to be a valuable tool for detecting very low deposition rates, and it offers the potential of sensitive, real time, spatially-resolved detection in time regimes extending to the nanosecond regime.

Structure and magnetic properties of compositionally modulated Tb-Fe thin films (abstract)

Artificially layered structures have attracted attention because of their unique structural and magnetic characteristics. It has been reported that in these structures the anisotropic distribution of atomic pairs can play an important role in determining their magnetic anisotropy.1 Our previous work showed that the application of substrate bias in a rf diode sputtering system was effective in producing dense and stable amorphous compositionally modulated films (CMFs).2 In this work, we studied the interrelationships of the structural and magnetic properties of amorphous Tb-Fe CMFs deposited under various substrate bias conditions (0, −70, −90 V) in a multitarget rf diode sputtering system. Although considerable research has been conducted on the effect of ion bombardment during deposition on the film structure, it has been difficult to independently control the film structure and the composition in such experiments because of the preferential backsputtering of atoms. Accordingly, in this research we systematically prepared Tb-Fe CMFs by independently controlling the rf voltage ratio of both the Tb and Fe targets, thereby allowing the composition of the film to be held constant as the substrate bias was changed. In contrast to alloy films, atomic clustering was observed in ultrathin layered films and produced anomalous structural and magnetic property changes, e.g., a shift in the room-temperature compensation composition (25 at. % Tb for −70 V biased films and 23 at. % Tb for −90 V biased films), higher Curie temperatures, and an increased compositional range over which amorphous phase was stable. The atomic arrangements in layered films were modified by a variation of deposition parameters such as layer periodicity, substrate bias, and composition. Although all the bias-sputtered CMF films, except those with small Tb content (<18 at. % Tb), had a dense and featureless amorphous structure, electron diffraction revealed significant differences in atomic short-range ordering for different Tb compositions. The results indicated that the magnetic moments of the Fe atoms in the CMF were increased by an enhanced pair ordering of like atoms produced by the alternate deposition of ultrathin layers. This result was consistent with the observed anomalies in magnetic properties.

Optical emission studies and preparation of high T c Tl Ca Ba Cu O thin films

Abstract Thin films of Tl Ca Ba Cu oxide were sputter-deposited from dual oxide targets using a symmetrical RF diode sputtering system. Spatially resolved optical emission spectra obtained using a scanning optical fiber for CuO, BaO-doped CuO, and Tl Ca Ba Cu O targets suggest no significant bombardments of the growing film by energetic particles in the plasma, resulting in a film composition close to that of the sputtering targets used. The superconducting properties of these films were found to depend strongly on the post-annealing conditions as a result of a substantial loss of thallium during annealing. Highly textured c-axis oriented films comprised mostly of Tl2Ca2Ba2Cu3Ox, with a zero resistance Tc of 122 K have been synthesized on MgO substrates by annealing in a sealed quartz tube of films wrapped in gold foil with Tl2Ca2Ba2Cu3Ox powders.

A substrate temperature measurement system for use during rf diode sputtering

A substrate temperature measurement system is described, which has proved useful for measuring substrate temperature in situ in an rf diode sputtering system. This temperature measurement system mimics the true deposition materials, geometry, and thermal contact as much as possible. The measurement electronics are quite insensitive to rf interference and allow for cancellation of lead resistance and thermoelectric voltages.

Effect of bias sputtering on magnetic properties and structure of compositionally modulated Tb/sub 32/Fe/sub 68/ films

Amorphous Tb/sub 32/Fe/sub 68/ compositionally modulated films were prepared in a multitarget RF diode sputtering system. Independent control of the RF voltage ratios of both the Tb and the Fe target allowed the composition of the film to be held constant as the substrate bias was changed. Cross-sectional transmission electron microscopy showed that small-scale atomic clusters were aligned in layers. Bias sputtering appeared to enhance the magnetic and magnetooptical properties and modified the film structure from a columnar void to a dense, featureless morphology. The surface magnetic properties and magnetooptical responses of the unbiased films were dominated by selective oxidation of Tb. Films deposited with 70-V bias, however, exhibited stable magnetic properties and uniform magnetooptical responses throughout the film thickness. >

Effect of oxygen on compositionally modulated Gd-Co thin films

We report on a study of the effect of oxygen on the chemical and structural stability of compositionally modulated Gd-Co multilayer films. Films with bilayer periods (BP) from 10 to 300 Å were prepared by alternate deposition in a multitarget RF diode sputtering system. Oxygen incorporation in the films was controlled during deposition by the application of rf substrate bias, and after deposition by annealing. Oxygen preferentially accumulated in the Gd layer and blocked its diffusion. Co columnar grain growth in samples with large BP appears to be associated with the asymmetric diffusion between the Gd and Co layers. TEM of samples with small BP showed a void network structure in the samples sputtered with 0 V substrate bias, but showed a phase separated amorphous structure in the samples sputtered with 65 V substrate bias. Annealing suppressed the growth of crystalline Gd and Co in samples with oxygen but enhanced the nucleation of GdCo2. A strong growth of Co and Gd grains occurred in annealed samples with low oxygen content but GdCo2 was not observed. Cross-section TEM showed that the growth of these grains was limited by the layer boundaries.

Characterization of reactively sputtered WNx film as a gate metal for self-alignment GaAs metal–semiconductor field effect transistors

Properties of reactively sputtered WNx films on a GaAs substrate have been investigated by electrical and physical analyses. WNx films were deposited from a pure W target by using three types of sputtering systems: (1) Magnetron sputtering system equipped with rf and dc mode; (2) S-gun sputtering system; (3) rf diode sputtering system. The composition of WNx films was easily and reproducibly controlled by changing the N2 content in Ar–N2 mixed ambient gas. The WNx–GaAs system was both electrically and metallurgically stable even after high-temperature annealing of up to 800 °C. The Schottky barrier height to n-type GaAs was more than 0.8 V, which is the highest value obtained so far among any other refractory metals. Self-aligned GaAs MESFET’s were successfully fabricated using a WNx gate. The transconductance was typically 150 mS/mm for 1.5 μm gate length.

Ba-ferrite thin film rigid disk for high density perpendicular magnetic recording

A magnetoplumbite type of hexagonal Ba-ferrite films, whose c-axis of crystallites is well oriented perpendicularly to the film plane, have been prepared by means of a conventional rf diode sputtering system. Morphological and crystallographic characteristics of sputtered Ba-ferrite films depend strongly on preparation conditions such as the distance between target and substrate d T-S and partial pressure of oxygen gas P O2 during the deposition. Ba-ferrite films with smooth surface are prepared at the extended d T-S in the region of low P O2 . Read/write characteristics of Ba-ferrite thin film deposited on thermally oxidized silicon wafer with radius of two inches were evaluated with ring type head. Recording density D 50 of Ba-ferrite thin film rigid disk depends strongly on Δθ 50 . In this work, D 50 of 110 and 190 kfrpi for Δθ 50 of 4.8 and 2.8°, respectively, have been attained.

Effect of magnetic field in rf sputtering on the crystal orientation and magnetic properties of Co-Cr perpendicular anisotropy films

Co–23-wt. %-Cr alloy films with thicknesses of 0.3 to 2.5 μm were deposited using a conventional rf diode sputtering system when a magnetic field Hs less than 90 Oe is applied during deposition. As Hs increases, the hcp c-axis orientation normal to the film plane develops and the half-angle width of the rocking curve of the (002) line Δθ50 reaches to 3.5 deg at Hs more than 40 Oe. The development of the orientation is strongly related to the concentration of O in the films, which is lower in the films deposited in a magnetic field than those in a nonmagnetic field. The magnetic properties such as perpendicular coercive force Hc⊥ and saturation magnetization Ms strongly depend on the substrate temperature rather than Hs.

Mechanism of rf reactive sputtering

The reactive mechanism of rf reactive sputtering has been investigated by mass spectrometry in an rf diode sputtering system. The result indicates that the gettering action of the sputtered active atom deposits influences the progress of reactive sputtering in addition to the target reaction. A model, taking the gettering action into consideration, is presented for the reactive sputtering of a metal. This model shows that an abrupt steplike decrease in the sputtering rate may occur at a definite partial pressure of a reactive gas p* in the plasma. The pressure p* is determined from the gettering rate of the sputtered deposits relative to the throughput of the reactive gas. The value of the pressure p* calculated on this model is in good agreement with the experimental results.

Mass Spectrometric Analysis in RF Reactive Sputtering Discharge

The reaction mechanism of rf reactive sputtering has been investigated by mass spectrometry in an rf diode sputtering system. The sputtering was carried out in the atmosphere of argon-nitrogen, argon-oxygen, and argon-methane mixtures, using a spherical titanium cathode as the target to avoid the edge effect of the planer one. The current of ion species impinging on the substrate was observed as a function of the concentration of the reactive gas. The experimental results show that the reaction process predominantly on the substrate surface rather than both on the target and in the discharge space.

Rf diode sputtering system

Rf diode sputtering system

The effects of pressure on the deposition rate in rf sputtering processes

The purpose of these experiments was to determine the dependence of deposition rate on gas pressure in a typical rf diode sputtering system and to interpret the observed results in terms of the changes in the sputtering conditions. It was found that the deposition rate increased as the pressure was raised from 3 × 10 −3 (0.4 Nm −2 to 10 −2 torr (1.33 Nm −2, for Cu, Ti, Ta but not for Al which remained almost constant. It was also found as the pressure was raised from 3 × 10 −3 (0.4 Nm −2) that the percentage increase in deposition rate was greatest for the sputtered material with highest atomic weight; an explanation of this phenomenon is suggested.

The operation and performance of an rf diode sputtering system in relation to its use as a research facility

The system used consisted of an MRC SM8500 rf diode sputtering module mounted on a standard Genevac coating plant. Metal, insulator and metal-insulator compound films have been prepared in the system and these are discussed in terms of sputtering rates and the uniformity of deposited material. Thickness uniformity was measured using 5 3-in. × 1-in. soda glass substrates laid side by side across the 5-in. dia substrate table, with a metal strip laid across a diameter giving rise to a step. Measurements of thickness were then made using multiple beam interferometery. The effects of gas pressure and electrode separation on thickness uniformity are discussed. The provision of a movable substrate table has made the system ideal for obtaining experimental evidence of theoretical relationships of the effects of temperature on the strain sensitivity of thin films without exposing the films to air. A straining rig has been constructed inside the vacuum system and measurements of both the strain coefficient of resistance and the temperature coefficient of resistance in vacuum are described.