Facing Targets Sputtering Apparatus Research Articles

Microstructure and noise characteristics of Co–Cr–Ta films deposited in low Ar pressure

Co 85Cr 13Ta 2/Cr/C films for longitudinal recording disks were deposited by plasma-enhanced facing targets sputtering apparatus on 2.5 in and ultra-flat substrates of glass ceramics, to obtain low-noise media for high-density recording systems. In this study, the dependence of the microstructure on the sputtering conditions, such as Ar pressure ( P Ar) of 0.07 mTorr in the background pressure of 1×10 −7 was investigated. As a result, better microstructure with very loosely, magnetically coupled grains was observed by TEM, compared with that in P Ar of 0.2 mTorr. This suggests that a proposed media is suitable for ultra-high-density recording systems.

Noise origin of Co–Cr–Ta films on ultra-flat glass-ceramic and Si substrates for longitudinal recording disks

Co 85Cr 13Ta 2/Cr bilayered films for longitudinal recording disks were deposited by plasma-enhanced facing targets sputtering apparatus on 2.5 in and ultra-flat disk substrates of glass-ceramic and single-crystal silicon. Their noise and read/write characteristics were almost comparable with those of the high-performance disks using Co–Cr–Pt films, with coercivity H c of 2.4 kOe, as a reference disk, even though the Co–Cr–Ta films exhibited macroscopic H c of only 800 Oe. Co 85Cr 13Ta 2 films are known as low-noise media. This study addresses the problem of how to obtain low-noise media, using excellent sputtering apparatus and disk substrate materials, to allow practical applications in ultra-high-density recording systems, including 1 in microdrives for mobile applications.

Thin film properties by facing targets sputtering system

In this study, film thickness distribution and c-axis crystalline orientation of deposited thin films were studied after preparing Co–Cr thin films, a promising ultra-high density perpendicular magnetic recording media, with a facing targets sputtering (FTS) apparatus. Electrical discharge characteristics needed for the optimum operation of sputter device was also studied in order to prepare thin films of superior c-axis crystalline orientation with FTS method (apparatus) in which thin film of fine quality can be formed because temperature increase of substrate due to the bombardment of high-energy particles can be restrained. As a result of the study, it is confirmed that the FTS method can give stable working under broad magnetic field and range of gas pressure and stable electrical discharge under low Ar gas pressure. Film thickness of prepared thin film shows fairy regular distribution and could obtain good thin films whose dispersion angle of c-axis crystalline orientation is about 3.5°.

Increase of coercivity and squareness ratio of by ferrite thin films by adding SiO/sub 2/ and substituting Al for Fe

Simple Ba ferrite (BaM) and SiO/sub 2/-added BaM (BaM:SiO/sub 2/) and Al substituted BaM (Al-BaM) films were deposited using the facing targets sputtering apparatus on SiO/sub x//Si wafers with Pt seed layers to enhance the c-axis orientation perpendicular to the film plane. Magnetic characteristics of the three kinds of BaM films were investigated and compared. Perpendicular coercivity H/sub c/spl perp// and squareness ratio S/sub /spl perp// of BaM:SiO/sub 2/ films increased to 4.2 kOe and 0.83, respectively, H/sub c/spl perp// and S/sub /spl perp// of Al-BaM films increased to 3.2 kOe and 0.89, but saturation magnetization M/sub s/ decreased to 2.9 kc. The magnetization reversal mechanism of BaM:SiO/sub 2/ and BaM films is not in coherent rotation mode but seems to be in the curling mode. The reason for high H/sub c/spl perp// of BaM:SiO/sub 2/ films is different from that of Al-BaM ones.

Al substituted Ba ferrite films with high coercivity and excellent squareness for low noise perpendicular recording layer

Al substituted BaM (Al–BaM) ferrite films with composition of BaAlxFe12−xO19 (x=0,1,2) were deposited using facing targets sputtering apparatus on SiOx/Si wafers with a Pt seed layer. A postannealing process is necessary to crystallize the films. It was confirmed that the substrate temperature Ts is also one of the important parameters for the magnetic properties of the postannealed films. Al–BaM ferrite films exhibit the Ts dependence of magnetic properties different from that of simple BaM ones. With increase of the Al content x in Al–BaM ferrite films, 4πMs decreased, while Hc and the anisotropy field HA increased. It was found that acicular shape grains formed more easily in Al–BaM ferrite films than in simple BaM ones. The squareness S⊥ increased largely by substitution of Al for Fe. The Al–BaM ferrite films with high Hc⊥ (∼3 kOe) and large S⊥(∼0.9) may be applicable as perpendicular magnetic recording layers with low noise level.

Deposition of perpendicular magnetic recording Co–Cr layers with nanosize domains using a plasma enhanced type of sputtering apparatus

Co–Cr thin films for perpendicular magnetic recording layers were deposited using a new type of facing targets sputtering apparatus by optimizing the film thickness tF, the substrate temperature Ts, and the sputtering Ar pressure PAr. The Co76Cr24 films with tF of 50 nm were deposited on glass disks at Ts of 230 °C and PAr of 0.03 Pa. These films were composed of highly c-axis oriented hcp crystallites, in which isolated ferromagnetic areas with lower Cr content CCr were uniformly distributed in the paramagnetic host matrix with higher CCr. The diameter of grains was 5–20 nm with voidless grain bounderies and the diameter of lower CCr areas was as small as 3–5 nm. The perpendicular coercivities Hc⊥ in initial growth regions, the whole film and surface regions were 1100, 1900, and 2700 Oe, respectively. Transmission electron microscope images of these specimens showed that ferromagnetic areas of highly c-axis oriented hcp crystallites with large uniaxial magnetic anisotropy constant are particulate-like. Consequently, the deposition of Co–Cr thin films with much higher Hc⊥ from the initial growth region to that of a surface may be the key technology for preparing perpendicular magnetic recording layers at ultrahigh density above 20 Gbit/in.2

Relationship between coercivity and deposition conditions of Ba ferrite films prepared by facing targets sputtering apparatus

At first, Ba ferrite films were deposited by the facing targets sputtering apparatus and the control of their coercivity was examined by substituting Fe 3+ ions to Ni 2+(F −) and Al 3+ ones and by changing crystallite size. The critical temperature for c-axis orientation T crit increased with increase of the substitution content x for both of BaO·6((1− x)Fe 2O 3· xNi 2OF 2) and BaO·6((1− x)Fe 2O 3· xAl 2O 3) films. The perpendicular coercivity H c⊥ of Ni 2+(F −) substituted Ba ferrite films decreased and that of Al 3+ substituted ones increased with increase in x and were about 0.32 and 3.3 kOe, respectively, at x of 0.17. Next, Ba ferrite films were deposited on Pt(1 1 1) underlayers and then, post-annealed at 800°C in air for 15 min. The value of H c⊥ corresponds to the crystallite size at T s up to 450°C. It has been founded that H c of BaM films were adjustable by substituting Fe 3+ ions to others such as Ni 2+(F −) and Al 3+ ions, and by controlling the crystallite size.

Annealing effect on magnetic characteristics on (La,Sr)MnO/sub 3/ sputtered films

A perovskite type of (La,Sr)MnO/sub 3/ films were deposited on SiO/sub 2//Si substrates with amorphous surface by using the facing targets sputtering apparatus. Although the film as-deposited at P(O/sub 2/) of 0.3 mTorr was not fully crystallized and the MR ratio was as small as 0.03% at the applied field of 5 kOe, it increased up to 2.5% for the film post-annealed at 850/spl deg/C in air for 10 min. The partial O/sub 2/ pressure P(O/sub 2/) strongly affected their crystallinity as well as the Mn content C/sub Mn/. The film as deposited at P(O/sub 2/) of 0.03 mTorr was composed of crystallites with excellent (100) orientation at relatively low substrate temperature T/sub s/ up to 500/spl deg/C and the large MR ratio of 3.8% was attained even at room-temperature measurement. Since this MR response exhibits excellent linearity, these LSMO films seem to be applied for magnetic sensor devices. It is clarified that the annealing process in preparation of LSMO film effectively increases the MR ratio of the film with insufficient crystallinity, and is not effective for the fully crystallized film.

Analysis of stray magnetic field at the substrate and effect of applying external magnetic field in facing targets sputtering

The distribution of magnetic field in a facing targets sputtering (FTS) apparatus and the effect of applying external magnetic field along the film plane were investigated. When ferromagnetic Co–Zr–Ta plates were used as the targets, the magnetic field at the center of the target surface was stronger than that of the surface of paramagnetic Al targets because of the high permeability of the Co–Zr–Ta targets, although the weaker one was needed for uniform sputtering yield of the target surface. Furthermore, when Co–Zr–Ta targets were used, slightly broader distribution of magnetic field was found around the central plane between the two targets. Thus, the magnetic field of about 20 Oe was applied at the surface of the substrate and uniaxial in-plane magnetic anisotropy was induced in the amorphous Co–Zr–Ta films deposited by the FTS apparatus. Therefore, the external field along the film plane was applied transversely to the direction of plasma confining field during deposition of the films. The soft magnetic properties of the Co–Zr–Ta films were improved by applying the external field and magnetic anisotropy of the films could be easily controlled regardless of the direction of the plasma confining field.

Novel facing targets sputtering apparatus with uniform magnetic field and plasma-free substrates

Facing targets sputtering (FTS) systems are known to have excellent characteristics such as plasma-free substrates and low working gas pressures in the order of 0.013 Pa. Thus, very smooth and uniform thin films suitable for high-density magnetic recording media can be obtained. In this study, the magnetic field strength in the plasma necessary to obtain a real plasma-damage-free environment around substrates was investigated, focusing on how the magnetic field was distributed in the plasma and thus how the plasma was sufficiently confined by a magnetic field applied perpendicular to both of the target planes. For this purpose, an auxiliary magnet was designed for each target and placed at a distance from the main magnet, which was located behind the target. The purpose of the auxiliary magnet was to confine and boost the magnetic fields generated by the main Al–Ni–Co magnet. An Fe–Nd–B magnet was used for the auxiliary magnet, because it was mechanically thin and had strong magnetic characteristics. To evaluate the plasma density distribution, the distribution of the electric potential was measured with a probe. The substrate voltage was also measured with a voltmeter to confirm that the environment around the substrates was plasma-free. One result of the design was that the electric potential distribution had much better uniformity than before (from −6 to −2 V); another was that the substrate voltage was slightly positive, indicating that the substrates were plasma-free. An FTS system with the above features is currently being used in various engineering experiments to fabricate plasma-damage-free thin films that have excellent magnetic and recording characteristics for magnetic recording media.

Plasma diagnosis and low-substrate-temperature deposition of Ba ferrite films in a damage-free sputtering apparatus with mixed gases

Ba ferrite films have been sputter-deposited from BaO · 6.5(Fe 2O 3) targets in Ar mixture (Ar of 0.18–0.0 Pa, Xe of 0.0–0.18 Pa and O 2 of 0.02 Pa) and Kr mixture (Kr of 0.18–0.0 Pa, Xe 0.0–0.18 Pa and O 2 0.02 Pa) by using facing targets sputtering apparatus and the plasma characteristics such as the electron density N e and the electron temperature T e on the Xe partial pressure P Xe were evaluated by using Langmuirs probe method. The discharge voltage increased from 490–700 V and 610–680 V for Ar mixture and Kr mixture, respectively, with the increase of P Xe . N e took minimum value at P Xe of 0.10 Pa and T e was almost constant at the neighborhood of the anode ring, while N e and T e monotonically increased and decreased with the increase of P Xe at the center of plasma. Ba ferrite films deposited at P Xe of 0.10 Pa in Ar mixture, possessed excellent surface smoothness and good magnetic characteristics such as the saturation magnetization 4πM s of 5.1 kG and the anisotropy constant K u of 4.23 J/m [3]. On the other hand, surface smoothness of Ba ferrite films deposited in Kr mixture was not improved and the maximum 4πM S of 4.0 kG was smaller than that of the films deposited in Ar mixture. These results seemed to be caused due to smaller kinetic energy of sputtered atoms at substrate surface.

Compact sputtering apparatus for depositing Co–Cr alloy thin films in magnetic disks

Co–Cr films deposited at excessively low Ar pressure P Ar often reveal critically poor c-axis orientation for the magnetron sputtering system. It has been found that high energy Ar atoms recoiled from the target plane would bombard heavily the growing films and degrade films' crystallographic characteristics. On the other hand, the facing targets sputtering (FTS) system could deposit the Co–Cr films with the excellent c-axis orientation even at P Ar as low as 0.02 Pa by optimizing the distance between targets D t–t. For example, the optimum value of D t–t was 105 mm for the targets of 100×100 mm 2 in size. The optimum conditions in FTS system were described for deposition of the Co–Cr films with the fine microstructure and the excellent c-axis orientation preferable as perpendicular recording layers, and the compact FTS apparatus of 250×250×200 mm 3 in size was designed in this study.

Preparation and characteristics of Co-Zn ferrite rigid disks without protective layers for high density recording

Spinel type of Co-Zn ferrite films were deposited on glass ceramic disk substrates of 1.89 inch diameter by using a facing targets sputtering apparatus without post-annealing process. Films deposited at substrate temperature T/sub s/ of 200 and 400/spl deg/C were composed of crystallites with clear (111) and (311) orientation, respectively. Disks with (111) orientation (Disk(111)) possessed larger perpendicular component of magnetization than that with (311) orientation (Disk(311)). The center-line average roughness R/sub s/ of Disk(111) and Disk(311) were 1.1 and 4.0 nm, respectively. Their read/write characteristics were examined without protective layer by using a merged type of magnetoresistive (MR) head with shield gap length of 0.27 /spl mu/m. The linear recording density D/sub 50/ increased with decrease of the thickness of recording layer for both disks and the highest D/sub 50/ was 1.36 kfrpi for Disk(111) 50 nm thick and 86 kfrpi for Disk(311) 35 nm thick, respectively.

A Ba Ferrite Disk Deposited at Low Temperature and Its Read/Write Characteristics

Magnetoplumbite-type Ba ferrite (BaM) layers were deposited on ZnO (002) and Pt (111) underlayers by using a facing-targets sputtering apparatus in a gas mixture of Ar, Xe, and O2 at various substrate temperatures Ts. A Ba ferrite layer as-deposited on a ZnO underlayer at Ts values above 475°C and one as-deposited on a Pt (mmm) under-layer at Ts values above 500°C revealed clear c-axis oientation. The saturation magnetization 4πMs was 5.1 kG and 4.0 kG for ZnO and Pt underlayers, respectively. Both underlayers exhibited high perpendicular coercivity Hc⊥ and low in-plane coercivity Hc// of about 2.4 and 0.2 kOe, respectively. A Ba ferrite layer deposited at a relatively low Ts of 300°C and annealed at 800°C in air also revealed excellent c-axis orientation and exhibited a relatively low perpendicular coercivity Hc⊥ of 0.6 kOe. A clear di-pulse was observed for the isolated wave form of a BaM/Pt film as-deposited at Ts of 600°C owing to the perfect perpendicular magnetization orientation, and a relatively high linear recording density D50 of 123 kFRPI was achieved.

Excellent crystallographic and perpendicular magnetic characteristics of Ba ferrite films deposited by gas mixture of Ar, Xe and O 2

Ba ferrite films with good c-axis orientation and magnetic characteristics were deposited on ZnO underlayer at substrate temperature T s from 475 to 600°C in the gas mixture of Xe (0.10 Pa), Ar (0.08 Pa) and O 2 (0.02 Pa) using the facing targets sputtering apparatus. The film deposited at T s of 600°C was composed of BaM and spinel ferrite crystallites and exhibited saturation magnetization 4 πM s of 5.1 kG and perpendicular anisotropy constant K u1 of 4.23 × 10 5 J m −3 which were larger than those of bulk BaM ferrite of 4.8 kG and 3.30 × 10 5 J m −3, respectively. c-axis orientation was observed even for the film deposited at low T s of 475°C and its values of 4 πM s, perpendicular coercivity H c and in-plane one H c⊥ were 4.7 kG, 2.38 kOe and 0.19 kOe, respectively.

Improving of the Permeability of Ni-Fe/Co67Cr33 Multilayers by Applying a Field during Deposition

To control the soft magnetic properties and the magnetic anisotropy of Ni-Fe/Co67Cr33 multilayers, an external field Hex of about 80 Oe was applied to films grown by using a facing-targets sputtering (FTS) apparatus during the deposition of the multilayers. The relative permeability μr of Ni79Fe21/Co67Cr33 multilayers without a Co67Cr33 underlayer was drastically improved in any direction when Hex was applied to the layers in the FTS apparatus. On the other hand, Ni79Fe21/Co67Cr33 multilayers with a Co67Cr33 underlayer revealed good (111) orientation of Ni-Fe crystallites, which had higher μr only in the Hex direction.

Improvement of soft magnetic properties of ferromagnetic Fe-Co-Ta:N/M films multilayered with paramagnetic Ti, Co/sub 67/Cr/sub 33/ and Fe/sub 82/Co/sub 9/Ta/sub 9/:N interlayers

[Fe-Co-Ta:N/paramagnetic layer] multilayers were deposited using a facing targets sputtering apparatus. Soft magnetic properties were optimized by adjusting the N content in paramagnetic interlayers of Ti, Co/sub 67/Cr/sub 33/ Fe/sub 82/Co/sub 9/Ta/sub 9/:N. The addition of a small amount of N atoms into the Ti interlayer was effective in maintaining a relatively high /spl mu//sub r/ even after annealing at 280/spl deg/C. Fe/sub 82/Co/sub 9/Ta/sub 9/:N/Ti-N multilayers revealed soft magnetic properties before and after the annealing process.

Preparation of Ferrite Rigid Disks with Isotropy and Read/Write Characteristics

Co-Zn ferrite films were deposited using the facing targets sputtering apparatus and their read/write characteristics were investigated as well as crystallographic and magnetic ones. Co-Zn ferrite films deposited at substrate temperature Ts of 100 and 400 °C revealed very smooth surface and the minimum center-line average roughness Ra were 2.5 and 3.0 nm, respectively. They were composed of crystallites with (111) and (311) orientation and possessed an isotropy and in-plane magnetic anisotropy. High linear recording density of about 114 kFRPI was achieved for specimen disks with (111) orientation which were deposited on fused quartz disk substrate using MIG type head with gap length of 0.27 μm.

Improvement of micromagnetism of Ni-Fe/Co/sub 67/Cr/sub 33/ multilayers for backlayers of perpendicular magnetic recording media

The multilayers composed of soft magnetic Ni/sub 79/Fe/sub 21/ layers and very thin paramagnetic Co/sub 67/Cr/sub 33/ layers were deposited using the facing targets sputtering (FTS) apparatus. When the external field H/sub ext/ of 100 Oe transverse to the direction of the plasma confining field H/sub p/ of about 20 Oe in the FTS apparatus was applied during layer deposition, the soft magnetic characteristics for the [Ni/sub 79/Fe/sub 21//Co/sub 67/Cr/sub 33/]/sub 2/ multilayers were improved. Furthermore, the relative permeability /spl mu//sub r/ of the multilayers was extremely and isotropically increased especially when the multilayers were deposited at extremely low Ar pressure P/sub Ar/ of 0.4 mTorr.

Ba ferrite films with large saturation magnetization and high coercivity prepared by low-temperature sputter deposition

Ba ferrite films were deposited in a mixture of Xe, Ar, and O2 by using facing targets sputtering apparatus with sintered targets of Fe-excessive BaM ferrite. By using Xe as sputtering gas, the bombardment of energetic Ar atoms recoiled from target to film surface was sufficiently suppressed and Fe content in Ba ferrite crystallites was significantly increased. It was found that the segregation of spinel crystallites among BaM ones were not observed and these BaM crystallites revealed the excellent c-axis orientation normal to film plane and clear perpendicular magnetic anisotropy. At substrate temperature Ts of 600 °C, saturation magnetization 4πMs of 5.1 kG, which is larger than that of BaM ferrite single crystal, and perpendicular coercivity Hc⊥ of 2.4 kOe were obtained. BaM ferrite films composed of well c-axis oriented crystallites with large perpendicular magnetic anisotropy constant, large saturation magnetization 4πMs of 4.7 kG and high perpendicular coercivity Hc⊥ of 2.4 kOe were obtained at substrate temperature Ts as low as 475 °C.