Sputtering Voltage Research Articles

Morphology of brass films sputtered on celloidin substrate towards high-gloss pigment

Film-transition technique is put forward to manufacture high-gloss metallic pigment. The effect of chamber pressure, target-to-substrate distance and sputtering voltage on morphology of brass film sputtered on celloidin substrate has been studied with atomic force microscopy and surface glossmeter. Polycrystalline films with different roughness are obtained through changing the sputtering conditions. The results show that all of the brass films have ellipsoidal surface, well-ordered grain orientation, large grain size and uniform grain distribution, resulting in low surface roughness and high surface luster of brass films. At the condition of chamber pressure 15 Pa, target-to-substrate distance 3.4 cm, sputtering voltage 1.5 kV and sputtering time 30 min, the brass film with thickness 41 nm, Cu content 69.5–73.6%, surface roughness 4.85 nm and surface gloss 136.7 Gs is deposited, revealing the great possibility for high-gloss metallic pigment.

プラズマスパッタ法によるＰｔ‐Ｃ複合薄膜の作製と構造評価

Nano-particle of Pt is essential for a fabrication of high performance catalysts. It was tried to control particle size of nano-particle of Pt by preparing platinum and carbon (Pt-C) composite thin films. Pt-C composite thin films have been deposited by plasma sputtering method using methane/argon mixture gas. The sputtering voltage varied from 100 to 1000 V, the partial pressure of the methane gas varied from 0 to 1.0×10-1 Pa, the total gas pressure of the methane and argon mixture was fixed at 1.8×10-1 Pa. A high-purity platinum metal was used as a sputtering target. The electrical property of Pt-C composite thin films can be changed from metallic to dielectric according to the preparation conditions of the sputtering voltage and the partial pressure of the methane. These composite thin films have various structures, consist of nano-scale particles of Pt crystallites. The designed catalysts of the Pt-C composite thin films comprising nano Pt particles will be possibly obtained by optimizing the partial pressure of the methane and the sputtering voltage.

反応性電子サイクロトロン共鳴（ＥＣＲ）スパッタ法によるフェライト薄膜の低温高速作製

A reactive sputtering apparatus utilizing electron cyclotron resonance (ECR) was developed for the deposition of thick oxide or nitride films usable in electric devices. A high deposition rate of 44 nm/min. was achieved using a conic alloy target and the deposited soft ferrite thin films were successfully crystallized without heat treatment during film deposition. Magnetic and physical properties for the film were analyzed in terms of saturation magnetization, coercivity, uniformity of film thickness, and inner stress. Obtained properties were consistent with soft magnetic films. The result confirms the oxygen partial pressure ratio to deposition rate strongly affected the magnetic properties. Well crystallized, ultra thin 3-nm-thick Ni-Zn ferrite (100) films, were also successfully deposited on MgO (100) underlayers. These results imply the ECR sputtering method is one of the most effective deposition methods for highly crystallized polycrystalline thick and thin films. Crystal orientation was improved by low target voltage sputtering as well as a relatively low deposition rate. Further improvement is considered to be possible by deposition at lower base pressures.

量産対応型ＥＣＲスパッタ装置によるフェライト薄膜の低温高速製造技術の開発

Reactive sputtering apparatus utilizing electron cyclotron resonance (ECR) microwave plasma was developed for deposition of ferrite thin-films. High deposition rate of 44 nm/min. was achieved using a conic alloy target, and the deposited soft ferrite thin films successfully crystallized without heat treatment during film deposition and post annealing. Magnetic and physical properties for the films were analyzed in terms of saturation magnetization, coercivity, uniformity of film thickness, and inner stress. These properties were proved to be good enough as soft magnetic films. The result described that the oxygen partial pressure ratio to deposition rate strongly affected the magnetic properties. Well crystallized ultra thin (3-nm-thick) ferrite films were also successfully deposited on MgO(100) underlayer. These results imply that ECR sputtering method is one of the most effective deposition methods for highly crystallized polycrystalline thick and thin films. Low target voltage sputtering as low as −100 V successfully improved crystal orientation of the ferrite films by suppressing the affect of recoiled argon ion bombardment to the substrate.

ステンレス鋼および合金鋼のスパッタエッチングによる円錐状表面炭化物の生成

Surfaces of solution-treated SUS304, SUS430, SCM435 and SKD5 steels were sputter-etched by Argon ions in an R.F. magnetron sputtering apparatus for 7.2, 14.4 and 28.8 ks. The observation using FIB and SIM shows that the conical carbides are formed on the surfaces of all the steels examined, and they are growing from the surface towards inside during sputter-etching. The carbides precipitate more along grain boundaries than in grains for SUS430 and SUS304 steels with low carbon content, while they uniformly precipitate in grains for SCM435 and SKD5 steels with high carbon content. The aspect ratios of conical carbides change within the range from 2 to 4 depending on sputter-etching time, sputter voltage, kinds of steels, size and density of carbides. The precipitation of carbides occurs under the balance of carbon diffusion velocity and sputter-etching rate. The size and density of conical carbides increase with increasing sputter-etching time. They eventually disappear, but many small carbides newly precipitate after long time sputter-etching.

Sputtering-growth of Cu/Zn alloy nanofilms on acrylics substrate

Sputtering-growth of Cu/Zn nanofilms on acrylics substrate has been investigated. Through experimental investigation of the effect of sputtering voltage, target-to-substrate distance, chamber pressure and sputtering time on the concentration, growth rate and surface morphology of Cu/Zn alloy nanofilms, it is found that Cu concentration in Cu/Zn alloy nanofilms change by no more than 6.23 wt.% compared with Cu/Zn alloy target. High sputtering voltage and short target-to-substrate distance can improve the growth rate of alloy film. There exist an optimal chamber pressure where growth rate reaches to a maximum value. Low sputtering voltage, high target-to-substrate distance and low chamber pressure are vital to prepare high-quality alloy nanofilms. The Cu/Zn alloy film prepared under the condition of sputtering voltage 1.6 kV, target-to-substrate distance 2.5 cm, chamber pressure 10 Pa and sputtering time 20 min, possessed high qualities, such as smooth and uniform surface, thickness 41 nm and Cu concentration 71.0 wt.%.

膜堆積中と後にＡｒイオン衝撃を加えたＦｅ薄膜の構造と磁気特性

Three kinds of Fe films, without Ar bombardment [BNON], with Ar bombardment after deposition [BAFT], and with Ar bombardment during deposition [BDUR], were prepared by dual ion-beam sputtering. The relationship between the morphology and the magnetic characteristics of the Fe films was investigated as a function of the film thickness tF in the wide range between 0.5 and 600 nm. The sputtering voltage and current were fixed at 1200 V and 50 mA, respectively. The Ar bombardments for BAFT and BDUR were carried out at an ion acceleration voltage of 200 V. The features of the film growth were very different according to the type of bombardment. The BNON films changed from an island structure to a layer structure at tF between 8.0 and 16 nm. The BAFT and BDUR films were revealed smoother surfaces than BNON and echibited a layer structure at tF above 1.0 nm. However, the saturation magnetization 4πMS of BDUR abruptly decreased at tF below 8.0 nm, since the Ar bombardment knocked Fe atoms into the surface region of the glass substrate during the initial growth stage. On the other hand, 4πMS of BNON and BAFT took an almost constant value of 21.5 kG with a fluctuation of about 5%. The coercivity Hc of BAFT had lowest value all the films at tF below 4.0 nm. These results indicate that Ar bombardment after deposition is useful for preparing ultrathin Fe films with excellent soft magnetic properties.

傾斜型対向ターゲット（Ｖ型カソード）による高速成膜へのアプローチ

Facing targets sputter deposition provides defect-less quenched films, which do not sustain plasma damage so much. In order to improve its low efficiencies of target erosion and deposition rate, gradient facing targets system, V cathodes, is proposed. Through this improvement the sputtering voltage is reduced about 5%, the deposition rate is doubled and the film thickness becomes more uniform in comparison with those for conventional facing targets.

Study on In2O3–SnO2 transparent and conductive films prepared by d.c. sputtering using high density ceramic targets

The influence of SnO2 concentration in the target on the film characteristics was studied in order to make the useful database for the device design when low discharge voltage sputtering method and a high density In2O3–SnO2 ceramic targets were used. In the case of the films deposited on unheated substrate, X-ray diffraction profile showed amorphous structure. Minimum resistivity of 358 μΩ cm was obtained by In2O3 film with mobility of 40.1 cm2 (V s)−1 and carrier density of 4.35E+20 cm−3. With the increase of SnO2 contents, resistivity of the films increased because of the decrease in both carrier density and mobility. Whereas, the films deposited on heated substrates showed polycrystalline structure. Resistivity was reduced, ranging from 5 to 20 wt.% SnO2, and minimum resistivity of 136 μΩ cm was obtained at 15 wt.% with mobility of 40.5 cm2 (V s)−1 and carrier density of 1.13E+21 cm−3. Transmittance and reflectance of these films strongly depend on carrier density.

Study on In 2O 3–SnO 2 transparent and conductive films prepared by d.c. sputtering using high density ceramic targets

The influence of SnO 2 concentration in the target on the film characteristics was studied in order to make the useful database for the device design when low discharge voltage sputtering method and a high density In 2O 3–SnO 2 ceramic targets were used. In the case of the films deposited on unheated substrate, X-ray diffraction profile showed amorphous structure. Minimum resistivity of 358 μΩ cm was obtained by In 2O 3 film with mobility of 40.1 cm 2 (V s) −1 and carrier density of 4.35E+20 cm −3. With the increase of SnO 2 contents, resistivity of the films increased because of the decrease in both carrier density and mobility. Whereas, the films deposited on heated substrates showed polycrystalline structure. Resistivity was reduced, ranging from 5 to 20 wt.% SnO 2, and minimum resistivity of 136 μΩ cm was obtained at 15 wt.% with mobility of 40.5 cm 2 (V s) −1 and carrier density of 1.13E+21 cm −3. Transmittance and reflectance of these films strongly depend on carrier density.

Dependence of interface layer thickness in FeCo–Si multilayers on sputtering parameters

The thickness dependence of interface layers in FeCo–Si multilayers on sputtering voltage, argon pressure and substrate bias potential was examined. The multilayers were characterised by in situ kinetic ellipsometry, X-ray reflection, X-ray diffraction, polarized neutron reflection and atomic force microscopy. A minimum thickness for the sum of both interface layers per period between 23 Å and 24 Å was found for different combinations of production parameter values. For an argon pressure of 1.3×10 −3 mbar the minimum interface thickness was found at a sputtering voltage of 708 V, and for an argon pressure of 2.3×10 −3 mbar at 880 V. These values were determined for a floating substrate potential of approximately +60 V relative to ground. Applying a substrate bias potential of −70 V the minimum interface thickness occurred for a sputtering voltage of 880 V at an argon pressure of 1.3×10 −3 mbar. This study confirmed the results of the former empirical optimisation. By revealing the existence of several sets of optimum parameters it opens up a further parameter to adjust other properties like stress. The interface layer on top of the FeCo layer is 16% thicker than the one on top of the Si layer due to the larger roughness of the FeCo layers.

Plasma diagnostic of ion and plasma PVD processes

The aim of this work was to compare different plasma PVD processes in respect to their plasma properties in dependence on the process parameters. The processes under investigation were reactive d.c. pulsed magnetron sputtering magnetically assisted, arc source ion plating, reactive multi plasma supported d.c. magnetron sputtering and reactive low voltage ion plating. The experiments were carried out in specially designed plants under variable vacuum and plasma conditions. The plasma properties, like ion mass, ion energy distribution, ion and electron densities of the different processes were investigated by mass spectroscopy with additional energy distribution analysis (PPM421-Inficon) and a Langmuir probe system (Smart Probe-Scientific Systems). The magnetically forced and medium frequency pulsed biased d.c. magnetron sputter deposition variants, showed a relatively large amount of single and double charged positive ions with kinetic energies up to 55 and 95 eV, as consequence of the applied modifications. The arc source process, even when performed at high pressures of approximately 10 −1 mbar, showed a remarkable amount of ions with energies up to 75 eV.

Magnetic characteristics of ultrathin Fe films with Ar bombardment during and after deposition

The three kinds of Fe films, without Ar bombardment (BNON), with Ar bombardment after deposition (BAFT), and with Ar bombardment during deposition (BDUR) were prepared by dual ion beam sputtering. The relationship between the morphology and the magnetic characteristics of the Fe films has been investigated as a function of the film thickness tF in the wide range between 0.5 and 600 nm. The sputtering voltage and current were fixed at 1200 V and 50 mA, respectively. The Ar bombardments for BAFT and BDUR were carried out at the ion acceleration voltage of 200 V for the period. The features of the film growth were very different among them. The films of BNON changed from island structure to layer structure at tF between 8 and 16 nm. The films of BAFT and BDUR revealed smoother surfaces than that of BNON and were in layer structure at tF above 1 nm. However, the saturation magnetization 4πMS of BDUR abruptly decreased at tF below 8 nm, since the Ar bombardment knocked Fe atoms into the surface region of glass substrate at the initial growth stage. On the other hand, 4πMS of BNON and BAFT took almost constant value of 21.5 kG with a fluctuation of about 5%. The coercivity HC of BAFT took the minimum value among them at tF below 4 nm. These results indicate Ar bombardment after the deposition is useful for preparing the ultrathin Fe films with excellent soft magnetic properties.

Influence of inert gases on ionized magnetron plasma deposition of carbon nitride thin films

Carbon nitride films were deposited by ionized magnetron sputtering in gas mixtures containing helium, neon, argon or krypton plus nitrogen. Sputtering voltages and deposition rates were measured, and the films were characterized by Fourier transform infrared (FTIR) spectroscopy, Rutherford back-scattering and nano-indentation. Application of an inductive plasma decreased the sputtering voltage, suggesting a decrease in the impedance of the discharge. A stable discharge was only obtained at pressures above 8 Pa in helium/nitrogen mixtures. The deposition rates increased with nitrogen content in neon, argon or krypton mixtures, both with and without an inductive plasma. The deposition rates with an inductive plasma in krypton/nitrogen were much higher than those in argon/nitrogen and neon/nitrogen mixtures with the same nitrogen contents. IR absorption bands at 1250, 1500 and 2200 cm −1 indicated the presence of disordered sp 2 hybridized carbon, graphite-like sp 2 carbon, and nitrile/isocyanate groups, respectively. In addition, amide-like vibration between 2800 and 3700 cm −1 was pronounced on application of the inductive plasma. FTIR results suggest that less dense films were synthesized with the inductive plasma. The N:C ratio was <0.3 in films deposited with no inductive plasma in the different inert gas mixtures, and increased with the inductive plasma in helium or argon mixtures. The film deposited in neon/nitrogen showed a low hardness (4.5 GPa) but high modulus (100.6 GPa). Deposition in argon/nitrogen with an inductive plasma produced the highest hardness.

Erosion rate measurements for GD-OES

For GD-OES the sputtering rate of standard reference materials is needed for calibration purposes. A modern optical profilometer is used to measure 3D crater profiles. The crater volume, the erosion and the sputtering rate is calculated. A series of measurements was performed at reference materials and different plasma conditions. The plot of the reduced sputtering rates versus voltage proves the validity of the Boumans formula.

Multistate per-cell magnetoresistive random-access memory written at Curie point

A multistate per-cell magnetoresistive random-access memory (MRAM) that writes data by a thermally assisted technique and reads data using the angular-dependent magnetoresistance is proposed. A hard magnetic layer or pinned ferromagnetic layer (CoFe-IrMn) is used as the recording layer. The free layer serves as the read layer. Before reading, the free layer's magnetization is set to the initial state. For the N states per-cell MRAM, the magnetization angle of the ith state (i=0 to N-1) between the free layer and recording layer can be set to be acos(1-2*i/(N-1)). For example, in the four-state per-cell MRAM, the magnetization angle can be set to be acos(1), acos(1/3), acos(-1/3), and acos(-1), which represent the four states, respectively. More states can be obtained if the signal-to-noise ratio is sufficient. At near Curie point, a small external field can be used to record the signal. In order to verify the idea, a spin-valve giant-magnetoresistance memory cell was fabricated using e-beam lithography and ultrahigh voltage sputtering. A 25-mA heating current and a small external field are enough to assist the writing process. A four-state per-cell memory is realized by this method.

Small cluster ions from source of negative ions by cesium sputtering

We investigated the delivery of small cluster ions using a source of negative ions by cesium sputtering (SNICS). The negative cluster ions of B n , C n , Si n , Co n , Cu n , Ge n , Au n , GeB n and SiB n have been extracted by SNICS. Adequate beam current of some small clusters was obtained by changing several parameters for cluster ion yield. After a comprehensive study of the operation parameters, such as target material selection, target geometry, sputtering voltage and current, the small cluster ion current can be increased by several orders of magnitude, with little change on the monomer ion yield.

Novel method of low-vacuum plasma triode sputtering

A novel sputtering method based on a triode-sputtering set-up is presented. This low-vacuum plasma method enables sputtering of thin films at a pressure range 0.2–5mTorr, using a supported gas discharge. The new method is capable of an independent control of the sputtering rate vs. sputtering voltage. Temperature distribution of electrons in the plasma was experimentally studied, using the Langmuir probe. Experimental sputtering results of Ti and Si layers, using this method, are described.

Preparation of TiO 2 thin films by sputtering applying electron cyclotron resonance plasma produced in arched magnetic mirrors

We have been able to produce electron cyclotron resonance plasmas for large-area processing in arched magnetic mirrors. Applying the plasmas to deposition of titanium dioxide thin films by reactive sputtering, we study the uniformity of deposition and crystal structures of the thin films by controlling the state of plasma. Sputtering voltage and target current are separately varied by changing the power of microwave. The deposition rate of films is lower at the center and higher at the edges of target. The crystal structure is in the rutile phase at the center and tends to be in the anatase phase at the edges. This tendency is changed by changing the state of plasma.

Application of electron cyclotron resonance plasma in arched magnetic mirrors to deposition of TiO2 thin films

We have been able to produce electron cyclotron resonance plasmas for large-area processing in arched magnetic mirrors. Applying the plasmas to deposition of titanium dioxide thin films by reactive sputtering, we study the uniformity of deposition and crystal structures of the thin films by controlling the state of the plasma. Sputtering voltage and target current are varied separately by changing the power of microwave. The deposition rate of films is almost uniform within an area of magnets forming the mirrors. It is slightly higher at the center and lower at the edges of target. The crystal structure of thin films is changed by the sputtering conditions. At the slow deposition rates of films, the films are mostly in the rutile phase. At the high deposition rates, the anatase phase shows up together with the rutile one. We suppose that the crystal structure is related to the plasma profile.