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.     

Effect of Ar gas pressure on growth, structure, and mechanical properties of sputtered Ti, Al, TiAl, and Ti3Al films

Single layers of Ti, Al, TiAl and Ti₃Al were sputter deposited on to 2″ oxidized Si 111 wafers and 7059 Corning Glass to study the effect of film thickness, temperature, and sputtering gas pressure on the mechanical and physical properties. In the present investigation, sputtering gas pressure was varied from 2 mT to 10 mT. The film thickness was varied from 1000 Å to 2 μm. The as-deposited Ti, Al and Ti₃Al films are well crystallized over the entire thickness range. Ti and Ti₃Al films show preferred orientation in the 0002 direction. On the other hand, Al films are random polycrystalline. TiAl films are nearly amorphous for all the thicknesses under consideration. TiAl films show formation of Ti (Al) solid solution phase with increasing Ar pressure. All the materials under consideration, show average film stress to be independent of thickness for thicker films. The nature of the stress (compressive or tensile) depends upon working gas pressure, sputtering power and the target material used. A definite trend is observed in the film stress as a function of Ar gas pressure. Both power and gas pressure influence the energetic bombardment of ions/atoms which in turn influence the average film stress. The nature of the intrinsic stress is explained by the atomic peening model. The Young's modulus of thin films is calculated by using the slope of the stress-temperature plots. The E values seem to change with deposition conditions, however, there is no obvious trend between the sputtering gas pressure and the Young's modulus of these thin films.     

SiNx-Submikrometerschichten – Parameteroptimierung –

SiN_x-submicrometer coatings – Optimization of the film properties – The influence of the deposition conditions on the properties of SiN_x-coatings was investigated. The characterized SiN_x-coatings were deposited by the help of reactive magnetron sputtering. Gas pressure and film thickness were varied. Scanning electron microscopic views of the cross sections show a columnar structure varying with the deposition parameters. The different structures are comparable to the known structure zone models. There is a transition from dense structures to open columnar structures with increasing gas pressure. The Microstructure of coatings also changes with increasing film thickness. Especially deposition conditions promoting shadowing effects lead to a large growth of the column diameter with increasing thickness. The intrinsic stresses and the ultramicrohardness of the coatings change with changing gas pressure, too. Dense structures have high intrinsic stresses and a high hardness while coarse columnar structures have low intrinsic stresses and a low hardness. The influence of the deposition parameters on wear behaviour and adhesion of the SiN_x-coatings was investigated by cavitation tests. Dense coatings with high intrinsic stresses show adhesion failures, and coatings with lower stresses and coarse columnar structures fail because of their lower intrinsic stability. Thus, there is an optimum gas pressure, at which the best properties are reached. It can be shown that with decreasing film thickness adhesion increases.     

氧分压对RF磁控溅射ZrO2薄膜生长特性的影响

采用反应射频(RF)磁控溅射法在n型(100)单晶S基片上沉积了ZrO2膜,研究了氧分压与ZrO：薄膜的表面粗糙度和沉积速率、SiO2中间界层的厚度以及ZrO2薄膜的折射率之间关系。结果表明：随着氧分压增高,薄膜的沉积速率降低,表面粗糙度线性地增加;在低的氧分压情况下,Si基片表面的本征SiO2层的厚度增加幅度较小,在高的氧分压情况下,Si基片表面的本征SiO2层的厚度有较大幅度地增加;在O2／Ar混和气氛下,溅射沉积的ZrO2薄膜的折射率受氧分压的影响不显著,而在纯氧气气氛环境下,ZrO2薄膜的折射率明显偏低,薄膜的致密性变差。     

Monte Carlo simulation of a control for cathodic sputtering

Subject is a set-up for gas pressure and discharge power regulation of a cathodic sputtering plant. It comprises two film thickness monitors and a control unit. The film thickness monitors measure the deposition rate at target and substrate level. By means of a computer the control unit calculates a quotient from the monitor data and compares it with a set value. Any change in gas pressure or discharge power leads to a deviation of the quotient from the set value. The control unit eliminates the deviation by a regulation of gas pressure or discharge power. The Monte Carlo method makes it possible to calculate the pressure dependence of the set-sup. It was not possible to determine a relationship between discharge power and the output signal of the control unit by the used theoretical model.     

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。     

Intrinsic stress of magnetron-sputtered niobium films

The stresses in niobium films were studied and the following preliminary results were obtained. (1) Niobium films can be prepared in any stress state (tensile, stress free or compressive) by varying the argon sputtering pressure. (2) As the bias voltage increases, more argon is incorporated into the film; both T_c and R/R₀ decrease; and the stress becomes more compressive and seems to saturate at about 1.5 × 10¹⁰ dyn cm^?2 at higher bias voltages (at an argon sputtering pressure of 1.9 Pa). (3) The lattice parameters show a close relation to the film stresses. (4) Lowering the sputtering rate results in a higher argon content in the bias-sputtered films. (5) The as-deposited film surface is smoother when deposited at lower pressures; the film has a columnar structure and intercolumnar gaps at higher pressures. (6) The film prepared at a higher bias voltage has a smoother as-deposited surface and a much smaller column size.From this study of the behavior of the stresses in niobium films, it appears that the stress is determined mainly by the microstructure and the energetic particle bombardment. Energetic particle bombardment may promote compressive stress by the incorporation of argon, by the formation of a more dense microstructure and by a “shot-peening” action.     

Magnetron sputter deposition of low-stress, carbon-containing cubic boron nitride films using Ar―N2―CH4 gas mixtures

Cubic boron nitride (c-BN) films produced by PVD and plasma-assisted CVD techniques typically exhibit undesired high compressive stresses. One of the effective and feasible methods to reduce stress and hence improve film adhesion has been a controlled addition of a third element into the film during deposition. In the present study, BN films were grown on to silicon substrates using reactive magnetron sputtering with a hexagonal BN target. An auxiliary flow of methane was mixed into argon and nitrogen as the working gas. The deposition was conducted at various methane flow rates at 400 °C substrate temperature, 0.2 Pa total working pressure, and − 250 V r.f. substrate bias. The microstructure of the deposited films was then examined in dependence of the methane flow rate. With increasing methane flow rate from 0 to approx. 2.0 sccm, the fraction of the cubic BN phase in the deposited films decreased gradually down to approx. 75 vol.%, whereas the film stress was reduced much more rapidly and almost linearly in relation to the methane flow rate. At 2.1 sccm methane, the stress became approx. 3 times reduced. Owing to the significantly decreased film stress, adherent, micrometer thick, cubic-phase dominant films can be allowed to form on silicon substrate. The microstructure of the films will be illustrated through FTIR and XRR.     

Internal stress and structure of evaporated chromium and MgF2 films and their dependence on substrate temperature

The internal stress in chromium and MgF₂ films was measured by the cantilever beam method. The substrate temperature, which was kept constant during the film deposition, could be varied up to 500°C. At room temperature both materials exhibit only tensile stress over the whole thickness range. At higher temperature for both materials compressive as well as tensile stresses are found as the film thickness increases. Similar stress versus thickness curves have previously been obtained for the low melting point metals silver, copper and gold deposited at room temperature. The model for the origin of the internal stress proposed to interpret the stress curves of the metals of the copper group is again applicable. Thus the changes in the stress curves obtained at different substrate temperatures can again be correlated with changes in the growth mode and thus the structure of the respective films. The structure determined on the basis of the stress model agrees with the film structure visible in the electron microscope.     

铝靶脉冲反应溅射沉积氧化铝薄膜中的迟滞回线的研究

采用脉冲磁控反应溅射工艺进行氧化铝薄膜的沉积实验 ,对该工艺过程中溅射电压和沉积速率与氧流量的“迟滞回线”现象进行了研究。通过给出靶面刻蚀区氧化层厚度与氧分压之间的关系 ,解释了薄膜沉积速率变化的原因。     

Kinetic process of phase separation in Co-SiO2 thin films and preparation of mesoporous SiO2 thin films with mesopore channels aligned perpendicularly to substrate surfaces

A physical co-sputter deposition process under a relevant working gas pressure condition was used to produce a multi-component thin film with a longitudinally self-organized microstructure. In this paper, Co-Si-O thin films were prepared by radio frequency (RF) magnetron sputtering, and their growth structures were studied by means of SEM, TEM, XRD and XPS. The microstructural changes in the Co-Si-O thin film and their dependence on Ar working gas pressure were investigated; the formation of Co-Si-O thin films, having a regular array of needle-like Co columns aligned perpendicularly to the substrate surfaces, was observed with appropriate Ar working gas pressure, and the diameter of the columns increased with increasing Ar pressure. Mesoporous silica thin films having perpendicular mesopore channels were obtained by chemical etching of the columnar Co parts in the Co-Si-O thin films. Through experimental observations, we propose that the phase separation and resultant microstructures in the thin films are determined by the surface mobility of the two components (Co and silica) on the film surface. A simple model, incorporating a diffusion process in the simultaneous deposition of two components, is presented. The model demonstrates the general trends of a kinetically self-organized microstructure in a two-component thin film.     

磁控反应溅射制备GexC1-x薄膜的特殊性分析

利用射频磁控反应溅射法 ,以 Ar,CH4 为原料气体 ,在较宽的工艺参数范围内制备出了 Gex C1- x薄膜 ,用干涉法测量了薄膜的厚度 ,对 Gex C1- x薄膜的沉积速率和 Ge原子百分比进行了研究。结果表明 ,Gex C1- x薄膜的沉积速率并没有随着靶中毒后而显著下降 ,甚至略有提高 ,而且 Ge原子百分比可以任意变化 ,表现出与通常磁控反应溅射法不同的特征 ,这与靶中毒之后反应气体粒子在靶面和基片上的反应特点有关。这一结论对磁控反应溅射法制备碳化物有普遍意义。     

Reactive sputtering of precursors for Cu2ZnSnS4 thin film solar cells

The quaternary semiconductor Cu₂ZnSnS₄ (CZTS) is a possible In-free replacement for Cu(In,Ga)Se₂. Here we present reactive sputtering with the possibility to obtain homogeneous CZTS-precursors with tunable composition and a stoichiometric quantity of sulfur. The precursors can be rapidly annealed to create large grained films to be used in solar cells. The reactive sputtering process is flexible, and morphology, stress and metal and sulfur contents were varied by changing the H₂S/Ar-flow ratio, pressure and substrate temperature. A process curve for the reactive sputtering from CuSn and Zn targets is presented. The Zn-target is shown to switch to compound mode earlier and faster compared to the CuSn-target. The precursors containing a stoichiometric amount of sulfur exhibit columnar grains, have a crystal structure best matching ZnS and give a broad peak, best matching CZTS, in Raman scattering. In comparing process gas flows it is shown that the sulfur content is strongly dependent on the H₂S partial pressure but the total pressures compared in this study have little effect on the precursor properties. Increasing the substrate temperature changes the film composition due to the high vapor pressures of Zn, SnS and S. High substrate temperatures also give slightly denser and increasingly oriented films. The precursors are under compressive stress, which is reduced with higher deposition temperatures.     

Influence of the nitrogen partial pressure on the properties of d.c.-sputtered titanium and titanium nitride films

The properties of titanium and titanium nitride films deposited onto biased substrates in a d.c. sputtering system were studied as a function of the partial nitrogen pressure. The deposition rate was deduced from film thickness measurements. The film composition was determined by Rutherford backscattering analysis and the structure was studied using X-ray diffraction. The resistivity was measured by the four-probe method and the temperature coefficient of resistivity (TCR) was determined in the temperature range from ?196 to 25 °C.Around a critical nitrogen pressure p_c of 4 × 10^-2 Pa the deposition rate decreases rapidly, the film structure changes from h.c.p. titanium to nearly stoichiometric f.c.c. TiN. At the same pressure, the film resistivity and the TCR present minimum values.A general sputtering model which takes into account the gettering action of the deposited material is proposed. This model allows the calculation of the surface coverage of the target by the reactive gas or the metallic compound and the determination of the deposition rate as a function of the reactive partial pressure. A good agreement is found with the deposition rates measured experimentally.     

Substrate geometry effect on the uniformity of amorphous carbon films deposited by unbalanced magnetron sputtering

A chromium doped amorphous carbon (a-C) film was deposited by an unbalanced magnetron sputtering. A special designed double-V shaped stainless steel model in simulating a plastic injection mold gateway was used as the substrate to investigate the geometric effect on the uniformity of the film. It was found that, on both the side wall and bottom plane of the double-V shaped substrate, the film properties strongly depended on a geometric parameter, geometric aspect ratio, defined as the depth over width of the simulated gateway at the points under measurement. With the increase of the aspect ratio, i.e. approaching to the narrow end and/or closer to the bottom plane of the gateway, the film thickness and hardness decreased and the intensity ratio of the Raman sub-bands D over G increased. With the increase of the aspect ratio, the micro hardness of the a-C film decreased far more significantly on the side wall than that on the bottom plane. With increasing working gas pressure, the film thickness decreased consistently, and the hardness uniformity on both the side wall and bottom plane was improved. When the substrate negative bias voltage was changed from −70 to −100 V, the film uniformity (for both the thickness and hardness) was improved on the bottom plane, but degraded on the side wall.     

Influence of deposition parameters on preferred orientation of RF magnetron sputtered BST thin films

Ba_0.65Sr_0.35TiO₃ (BST) thin films have been deposited by radio frequency magnetron sputtering. The effects of the deposition parameters on the crystallization and microstructure of BST thin films were investigated by X-ray diffraction and field emission scanning electron microscopy, respectively. The crystallization behavior of these films was apparently affected by the substrate temperature, annealing temperature and sputtering pressure. The as-deposited thin films at room temperature were amorphous. However, the improved crystallization is observed for BST thin films deposited at higher temperature. As the annealing temperature increased, the dominant X-ray diffraction peaks became sharper and more intense. The dominant diffraction peaks increased with the sputtering pressures increasing as the films deposited at 0.37–1.2 Pa. With increasing the sputtering pressure up to 3.9 Pa, BST thin films had the (110) + (200) preferred orientation. Possible correlations of the crystallization with changes in the sputtering pressure were discussed. The SEM morphologies indicated the film was small grains, smooth, and the interface between the film and the substrate was sharp and clear.     

Optical properties and residual stress in aluminum nitride films prepared by alternating-current dual reactive magnetron sputtering

Aluminum nitride films were deposited by alternating-current dual reactive magnetron sputtering. The influence of different nitrogen flow and working pressures at a sputtering power of 5 kW on the refractive index, extinction coefficient, crystalline structure, residual stress, and surface roughness of aluminum nitride films was discussed. The aluminum nitride film would have high refractive index, low extinction coefficient and small residual stress at suitable nitrogen flow rate and low working pressure.     

磁控溅射镀膜中工作气压对沉积速率的影响

沉积速率是磁控溅射镀膜技术中的一项重要指标,它由许多因素决定.为了定性地了解沉积速率与工作气压之间的关系,通过实验测定了不同工作气压下的沉积速率,发现存在一个最大值,并对应有一个最佳工作气压.运用气体放电理论对这一现象进行了分析.这个结论为提高薄膜制备效率指明了方向,并为进一步建立沉积速率与工作气压之间的数学模型打下了基础.     

Structural and morphological investigations on DC-magnetron-sputtered nickel films deposited on Si (100)

Pure nickel thin films were deposited on Si (100) substrates under different conditions of sputtering using direct current magnetron sputtering from a nickel metal target. The different deposition parameters employed for this study are target power, argon gas pressure, substrate temperature and substrate-bias voltage. The films exhibited high density of void boundaries with reduction in <111> texture deposited under high argon gas pressures. At argon gas pressure of 5 mTorr and target power of 300 W, Ni deposition rate was ~40 nm/min. In addition, coalescence of grains accompanied with increase in the film texture was observed at high DC power. Ni films undergo morphological transition from continuous, dense void boundaries to microstructure free from voids as the substrate-bias voltage was increased from −10 to −90 V. Furthermore, as the substrate temperature was increased, the films revealed strong <111> fiber texture accompanied with near-equiaxed grain structure. Ni films deposited at 770 K showed the layer-by-layer film formation which lead to dense, continuous microstructure with increase in the grain size.     

白宝石上生长SiO2薄膜的工艺

用射频磁控反应溅射法,以高纯Si为靶材,高纯O2为反应气体,在白宝石上制备SiO2薄膜。对影响薄膜生长的工艺参数进行了分析,测试了薄膜的成分,并研究了薄膜的红外光学性能。结果表明,制备的薄膜中Si和O形成SiO2化学键,计算出的O与Si的原子比接近2:1,采用射频磁控反应溅射法在白宝石上能够沉积出SiO2薄膜。制备出的SiO2薄膜对白宝石衬底有较好的增透作用。