Control of coercive force of Co-Cr sputtered films

The role of c-axis orientation of the crystallites in the sputtered Co-Cr thin films has been investigated aiming for the control of the coercive force of the film. It has been confirmed that the c-axis orientation plays a very important role to control the coercive force, Hcperpand Hcparellel. When the c-axis of the film is well oriented, only Hcperpchanges with the increase of the substrate temperature Ts leaving Hcparellelrather constant. However, both Hcperpand Hcparellelchange together with the increase of Ts when the film is poorly oriented. It has been considered that Ts is only the factor adjustable for controlling Hc of the films, but the results in this study indicate that the c-axis orientation is the another factor to control Hcperpand Hcparellel, separately.     

The role of atomic mobility during film growth in the structural and magnetic properties of CoCr

We have studied the morphological, crystallographic, and magnetic properties of CoCr thin films sputtered at different substrate temperatures and pressures. Conditions which produce high adatom mobility on the surface of the growing film lead to good c-axis orientation and magnetic anisotropy normal to the substrate, while low mobility leads to poor c-axis orientation and anisotropy. These results are explained in terms of van der Drift's model of the evolutionary growth of vapor-deposited films. The perpendicular coercivities of our samples depend only on the substrate temperature and we find no correlation with the film morphology or grain size.     

Co-Cr perpendicular magnetic recording tape by vacuum deposition

The relation between the incident angle and the crystallographic orientation of a vacuum deposited Co-Cr film is discussed. Also presented are the magnetic properties and the orientation of both a Ni-Fe underlayer and the Co-Cr film for the double layer medium, and the experimental results about the composition distribution in the co-cr film. The films were deposited on a transporting polymer substrate by continuous vacuum deposition. It is found that the orientation of the Co-Cr film is determined only by the incident angle at the initial point of the film formation, and that deposition efficiency more than 50% can be achieved easily. A double layer medium with Ti film under the Ni-Fe film (Co-Cr/Ni-Fe/Ti medium), which is suitable for perpendicular magnetic recording, is produced by vacuum deposition. Auger depth profile in radial direction of the column of the Co-Cr film shows directly that there is Cr segregation near the columnar grain boundaries.     

Inclining columnar structure in Co-Cr films prepared by roll magnetron sputtering

Co-Cr films, sputtered onto continuously transported substrates, exhibit columnar structure bowing according to incident angle variation during deposition. Surface grains were found to be elongated along the substrate moving direction. This factor seems to be related with the relative film motion. The column inclination is well approximated by the incident angle of the atom beam vector sum, considering the incidence probability from the two line target sources. It was found, by analysing the surface grain shapes using a high speed image processor, that the Co-Cr grains exhibited a sharp normal probability distribution in regard to diameter.     

Growth and characterization of high resistivity c-axis oriented ZnO films on different substrates by RF magnetron sputtering for MEMS applications

In the present work, we report the deposition of high resistivity c-axis oriented ZnO films by RF magnetron sputtering. The deposition parameters such as RF power, target-to-substrate spacing, substrate temperature, and sputtering gas composition affect the crystallographic properties of ZnO films, which were evaluated using XRD analysis. The self-heating of the substrate in plasma during film deposition was investigated and we report that highly “c-axis oriented” ZnO thin films can be prepared on different substrates without any external heating under optimized deposition parameters. The post-deposition annealing of the film at 900 °C for 1 h in air ambient increases the intensity of (002) peak corresponding to c-axis orientation in addition with the decrease in full width at half maxima (FWHM). Bond formation of ZnO was confirmed by FTIR analysis. Grains distribution and surface roughness have been analyzed using SEM and AFM. The DC resistivity of the films prepared under different deposition conditions was measured using MIS/MIM structures and was found to be in the range of 10¹¹–10¹² Ω cm at low electric field of 10⁴ V/cm. The ZnO film of 1 μm thickness has transmittance of over 85% in the visible region. Applications of these films in MEMS devices are discussed.     

Magnetic properties and microstructure of sputtered Co-Cr films

Microscopic structural parameters of sputter-deposited Co-Cr films, such as the effective crystallite size along the thickness direction Deff(=coherent length), the strain < ε²>^1/2, and the lattice spacing d00.2have been systematically studied by means of X-ray analysis and transmission electron microscopy (TEM) in conjunction with the magnetic properties. Cross-sectional observations by TEM revealed that a number of slip bands exist in the poorly oriented films. Slip and deformation bands interrupt the coherency along the c-axis in films, giving a spread to the orientation of the c-axis across the band boundaries. The effective crystallite size Defffor such poorly oriented films was found to be less than 200 Å, which is consistent with the period of contrast observed by TEM. When a film was annealed, Deffwas found to increase and the saturation magnetization Ms decreased, implying that Cr segregation as well as slip bands decreased throughout the thickness.     

Cr掺杂ZnO薄膜晶体结构及光学性能的研究

采用磁控溅射法在载玻片上制备了不同Cr掺杂浓度的ZnO薄膜,并对其紫外发光性能做了初步研究.XRD结果表明,所制备的样品具有纤锌矿结构,呈c轴择优取向生长;透射谱表明,改变Cr掺杂浓度可以使ZnO薄膜的吸收边向短波方向移动,并且薄膜的禁带宽度连续可调;光致发光(PL)谱表明,所有样品的PL谱由发光中心位于370nm的紫外发光峰组成,且该峰的峰位蓝移,与吸收边缘移动的结果吻合.2.0%(原子分数,下同)的Cr掺杂可以提高ZnO的紫外发光强度,而过量的Cr掺杂反而会降低其紫外发光强度.     

Dependence of segregated microstructure in sputter-deposited CoCr film on deposition conditions

The compositional segregation of sputter-deposited CoCr films prepared under substrate temperatures Ts of 90-160°C and Ar gas pressures PAr of 4-30 mTorr are studied by transmission electron microscopy. The segregated microstructure depends on Ts and PAr. The degree of the segregation increases as Ts increases, and is maximized at a medium PAr. Saturation magnetization increases as the degree of the segregation increases. Vertical coercivity in film with the same degree of the c-axis orientation increases as the degree of segregation increases.     

Effect of chelating agents on the preferred orientation of ZnO films by sol-gel process

The effect of chelating agents of ZnO precursor solutions on crystallization behavior was investigated. Two different additives, monoethanolamine (MEA) and diethanolamine (DEA), and crystalline Pt (111)/Si and amorphous SiN _x /Si substrates, were used for this study. ZnO film grown on SiN _x /Si from a DEA-chelated precursor solution shows a poorly oriented microstructure with weak crystallization peaks, while ZnO film grown on Pt(111)/Si shows a c-axis preferred orientation. In the case of ZnO films prepared with a MEA-chelated precursor solution, all films show a strong preferred orientation irrespective of substrate type. This result clearly demonstrates the role of the chelating agent on the crystallographic orientation and crystallization behavior of sol-gel processed ZnO films.     

An orientation competition in yttria-stabilized zirconia thin films fabricated by ion beam assisted sputtering deposition

A previously found orientation competition in ion beam sputtered yttria-stabilized zirconia thin films was studied in detail. The effects of sputtering energy and deposition angle were analyzed in ion sputtered films without assisting ions bombardment. It is found that for normally deposited films, (001) and (011) orientations are favored at low and high sputtering energy respectively. For inclined substrate deposited films, as deposition angle increases, (001), (011) and (111) orientations are advantaged in turn. The results can be attributed to the in-plane energy exchange of deposition atom and adatoms. In ion beam assisting deposited YSZ films of low assisting ions energy and current, a (001) oriented biaxial texture is gradually induced as ion energy increased. In the case of ion beam assisted inclined deposition of 45°, (001) orientation is enhanced and two preferential in-plane orientations are found coexist.     

薄膜溅射沉积过程中的原子喷丸效应

原子喷丸效应是薄膜溅射沉积过程中的普遍现象，是指反弹工作气体原子和溅射原子构成的荷能粒子流对生长膜面的轰击作用。这些荷能粒子在向基片输运的过程中受到工作气体原子的散射。原子喷丸效应与靶材和工作气体的原子质量比以及工作气体压强密切相关。以平面磁控溅射Co－Cr，Ni-Fe和Gd－Fe等二元合金薄膜为对象，研究其内应力与Ar工作气体压强的关系，并探讨原子喷丸效应对应力的影响。在靶材原子质量较大并且工作气体压强较低的情形下，可导致薄膜中呈压应力。     

Studies on sputtering process of multicomponent Zr-Ti-Cu-Ni-Be alloy thin films

Sputter deposition process of a multicomponent Zr-Ti-Cu-Ni-Be metallic alloy has been studied experimentally and by numerical simulations. Monte-Carlo simulations were performed using a model based on thermalization and diffusion of sputtered atoms. Incident energy and angle of sputtered atoms on substrate were obtained from simulations. The incident angular distribution was observed to be a normal distribution at all sputtering pressures. Average incident kinetic energy of the condensing atoms on the substrate was observed to be 0.2-0.3 eV indicating most of them are thermalized. Simulations were extended to predict compositional variations in films prepared at various process conditions. These results were compared with composition of films determined experimentally using Rutherford Backscattering Spectrometry (RBS). Contents of Zr, Ti, Cu and Ni quantified using RBS were in moderate agreement with the simulated composition. Be could not be quantified accurately by RBS largely due to very low energy peak of Be in the spectrum. These studies are shown to be useful in understanding the complexities in multicomponent sputtering.     

Effects of the Ar–N2 sputtering gas mixture on the preferential orientation of sputtered Ru films

We have investigated the influence of N₂ addition to the Ar sputtering gas on the crystal orientation of sputtered Ru films. An rf magnetron sputtering apparatus with a Ru target (99.9%) and a glass substrate heated to 100 °C or 300 °C was used for the deposition. The crystal structure, chemical composition and electrical properties of the resultant films were investigated. X-ray diffraction (XRD) revealed the dominant orientation at 0% N₂ to be the c-axis. With increasing proportion of N₂ in the sputtering gas at a substrate temperature of 100 °C, the intensity of the (002) peak decreased, finally disappearing at 50% N₂. This c-axis-suppressed Ru film sputtered at 50% N₂ was found to contain nitrogen by Auger electron spectroscopy (AES), but by annealing the film in vacuum at 400 °C, the nitrogen in the film was completely removed. The film orientation remained the same as before annealing. Thus, we have demonstrated a new method for depositing Ru films with a controlled preferential orientation of either c-axis oriented or c-axis suppressed.     

Growth of textured LiNbO3 thin film on Si (111) substrate by pulsed laser deposition

Highly c-axis oriented LiNbO₃ thin films have been deposited on Si (111) substrates by pulsed laser deposition. A stoichiometric sintered LiNbO₃ is used as the target. The c-axis orientation and stoichiometry of LiNbO₃ films are strongly influenced by substrate temperature and oxygen pressure. The substrate temperature 600 °C and oxygen pressure 20–30 Pa are found to be optimized parameters for the growth of textured film. The results showed that the size and the density of droplets decreased with increasing substrate temperature, and droplets would disappear when substrate temperature is increased above 600 °C. The surface microstructures of LiNbO₃ films under optimized conditions are fine, uniform and dense. The AFM images ensured that the as-grown films are good enough to be integrated with the semiconductor devices.     

Influence of deposition conditions and substrate structure on the structure of sputtered tellurium films

A study has been made of the growth of tellurium films sputtered onto four substrate materials (cover glass, spinel, quartz and alumina), unheated as well as heated to 100°, 150°, 200° and 250°C. It was found that the structure of the substrate exerted no measurable influence on the structure of the films. However, sputtering conditions do influence the preferred orientation. Tellurium films sputtered onto unheated substrates have a preferred orientation of the (100) type (i.e. with the (100) planes parallel to the substrate). Those on heated substrates show a preferred orientation of the (101) type. Furthermore, thickness is an important factor. Tellurium films with thickness less than 6000 Å have a (100)-type preferred orientation, but thicker films have a (101) orientation. All the observations can be explained in terms of recrystallization taking place during deposition due to heating of the film.     

Structure and electrical properties of ITO thin films deposited at high rate by facing target sputtering

High rate deposition of ITO thin films at a low substrate temperature was attempted by using a facing target sputtering (FTS) system. Deposition rate as high as 53 nm/min was realized on polycarbonate film substrate of 80-μm thickness. When the film was deposited at a deposition rate above 80 nm/min, polycarbonate film substrate was thermally damaged. The film deposited by FTS has much smaller compressive film stress than the film deposited by conventional magnetron sputtering. The film stress was reduced significantly by increasing the sputtering gas pressure and stress-free films can be obtained by adjusting the sputtering gas pressure. This may be mainly caused by the fact that bombardment by high energy negative oxygen ions to substrate surface during deposition can be completely suppressed in the FTS. Film structure and electrical properties changed little with substrate position, and uniform films were obtained by the FTS.     

射频磁控溅射沉积高质量ZnO薄膜的工艺研究

在室温下利用射频磁控溅射法在硅(100)基片上制备ZnO薄膜,利用X射线衍射(XRD)和扫描电子显微镜(SEM)对其结晶性能进行分析。研究了制备条件对薄膜沉积速率的影响。分析了薄膜沉积速率对薄膜结晶状况的影响及源气体中的氧气和氩气的流量比对薄膜结晶状况的影响。研究结果表明,薄膜的生长速率强烈依赖于射频功率和工作气压,薄膜的结晶性能强烈依赖于薄膜的沉积速率和反应气体中氧气和氩气的流量比。制备高结晶质量的ZnO薄膜的最佳工艺参数为靶到衬底的距离为4cm,输入功率为250W,源气体中氩气和氧气的流量比n(Ar)∶n(O2)为5∶20,溅射工作气压为2Pa。在最佳工艺条件下所制备的薄膜表面平整致密,接近单晶,在可见光区的透射率高达90%。     

Plasma effects on the Co-Cr deposition in opposing targets sputtering method

It is well known that Co-Cr films show a high perpendicular magnetic anisotropy, coercivity of 1000 oe or above and other properties suitable for perpendicular magnetic recording media. In this report, Co-Cr films, deposited by the bombardment of ions extracted from plasma using a new type of cathode sputtering apparatus with opposing targets, which will be called opposing targets sputtering hereafter, were investigated on morphology, crystal structure and magnetic properties. It was found that in the Co-Cr films of suitable magnetic properties for recording media, the morphology changes and the degree of C-axis orientation of Co-Cr hcp crystal, Δθ50is a constant value as low as about 3° with the increase of ion bombardment energy during deposition. Both morphology and the dependency of Δθ50on thickness of the Co-Cr films deposited by the opposing targets sputtering considerably differ from those by RF sputtering. There was no columnar structure observed in the cross section of the Co-Cr films suitable for perpendicular magnetic recording media prepared by the opposing targets sputtering, whereas columnar structure is reported to be observed clearly in the case of both RF sputtering and vacuum vapor deposition.     

SAW器件用金刚石基c轴取向LiNbO3压电薄膜的制备

采用脉冲激光沉积技术,在以c轴取向ZnO作为缓冲层的金刚石/硅基底上制备出了结晶良好的高c轴取向LiNbO3薄膜。利用X射线衍射对薄膜的结晶质量和c轴取向性进行了研究,结果表明制得的LiNbO3薄膜具有高度c轴取向且结晶质量良好。采用扫描电子显微镜和原子力显微镜对薄膜的表面形貌进行了分析,发现薄膜表面光滑,晶粒尺寸均匀,薄膜表面粗糙度约为20nm。