Features of the electron exchange under grazing scattering of H− ions from a thin aluminum disk

The electron exchange under grazing scattering of a negative hydrogen ion from a thin Al disk is analyzed via the wave packet propagation method that does not use the perturbation theory. The probability of H^? ion fraction formation is calculated as a function of the ion velocity component (v_‖) parallel to the surface. It is shown that the yield of negative hydrogen ions has a bell-like dependence on the value of v_‖ under grazing scattering from a thin disk. The negative ion yield under grazing scattering from a disk is very close to the H^? ion yield under scattering from a film. The maximum of the probability of H^? fraction formation calculated for a thin disk is shifted to smaller values of v_‖ with respect to the maximum of the probability of H^? formation for a thin film.     

Correlation of process parameters and properties of TiO<Subscript>2</Subscript> films grown by ion beam sputter deposition from a ceramic target

The correlation between process parameters and properties of TiO₂ films grown by ion beam sputter deposition from a ceramic target was investigated. TiO₂ films were grown under systematic variation of ion beam parameters (ion species, ion energy) and geometrical parameters (ion incidence angle, polar emission angle) and characterized with respect to film thickness, growth rate, structural properties, surface topography, composition, optical properties, and mass density. Systematic variations of film properties with the scattering geometry, namely the scattering angle, have been revealed. There are also considerable differences in film properties when changing the process gas from Ar to Xe. Similar systematics were reported for TiO₂ films grown by reactive ion beam sputter deposition from a metal target [C. Bundesmann et al., Appl. Surf. Sci. 421, 331 (2017)]. However, there are some deviations from the previously reported data, for instance, in growth rate, mass density and optical properties.     

Ionized physical vapor deposited Al2O3 films: Does subplantation favor formation of α‐Al2O3?

The broad energy distributions of the condensing particles typically encountered in ion assisted vapor deposition techniques are often a drawback when attempting to understand the effect of the energetic bombardment on the film properties. In the current study, a monoenergetic Al⁺ beam generated by a filtered cathodic arc discharge is employed for the deposition of alumina (Al₂O₃) films at well defined Al⁺ ion energies between 4 eV and 200 eV at a substrate temperature of 720 °C. Structural analysis shows that Al⁺ energies of 40 eV or larger favor the formation of the thermodynamically stable α‐Al₂O₃ phase at the expense of other metastable Al₂O₃ polymorphs. The well defined ion energies are used as input for Monte‐Carlo based simulations of the ion–surface interactions. The results of these simulations reveal that the increase of the Al⁺ ion energy leads to an increase in the fraction of ions subplanted into the growing film. These findings underline the previously not considered role of subsurface processes on the phase formation of ionized physical vapor deposited Al₂O₃ films. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Wettability and crystalline orientation of Cu nanoislands on SiO<Subscript>2</Subscript> with a Cr underlayer

Cu thin films were grown by sputter deposition on SiO₂ substrates with a Cr underlayer that is known to improve the adhesion between Cu and SiO₂. The initial stage of Cu growth was investigated using transmission electron microscopy. Results showed that non-wetting spherical Cu nanoislands were formed with a random crystalline orientation on Cr/SiO₂, and evolved into a randomly oriented polycrystalline thin film. These results were then compared with our previous results on the initial growth of Cu on SiO₂ with and without a Ti underlayer. A quantitative model was proposed to explain the difference in dependence of the wettability of microscopic nanoislands and that of the adhesion of macroscopic thin films on interfacial interactions and surface energies. PACS 61.46.+w; 68.35.Md; 68.35.Np     

Ion beam sputter deposition of TiO<Subscript>2</Subscript> films using oxygen ions

TiO₂ thin films were grown by ion beam sputter deposition (IBSD) using oxygen ions, with the ion energy and geometrical parameters (ion incidence angle, polar emission angle, and scattering angle) being varied systematically. Metallic Ti and ceramic TiO₂ served as target materials. The thin films were characterized concerning thickness, growth rate, surface topography, structural properties, mass density, and optical properties. It was found that the scattering geometry has the main impact on the film properties. Target material, ion energy, and ion incidence angle have only a marginal influence. Former studies on reactive IBSD of TiO₂ using Ar and Xe ions reported equivalent patterns. Nevertheless, the respective ion species distinctively affects the film properties. For instance, mass density and the refractive index of the TiO₂ thin films are remarkably lower for sputtering with oxygen ions than for sputtering with Ar or Xe ions. The variations in the thin film properties are tentatively attributed to the angular and the energy distribution of the film-forming particles, especially, to those of the backscattered primary particles.     

Electron irradiation induced reduction of magnesium chloride thin films deposited on gold: XPS and ISS study

The ion and electron beam stimulated desorption from MgCl₂ ultra-thin films is reported. The films are prepared by gas phase deposition of MgCl₂ on a polycrystalline Au foil in ultra-high vacuum conditions. The MgCl₂ film, held at 330 K, is uniformly bombarded with Ar-ions or electrons of 1 keV of energy. The chemical composition of the film is monitored by XPS and ISS. The ionic film surface is terminated by Cl atoms, as shown by ISS. The ion bombardment sputters the MgCl₂ film, without changing the chemical composition of the film surface. In contrast, the electron beam damages markedly the film, with the reduction of Mg²⁺ to the metallic state. Only 10% of the original Cl is left in the film after 30 min of electron bombardment. The ISS analysis shows that Mg atoms appear on the film surface after electron irradiation.     

CVD金刚石中的氮对等离子体刻蚀的影响

采用非对称磁镜场电子回旋共振等离子体分别对沉积过程中掺氮和未掺氮的化学气相沉积金刚石膜进行了刻蚀研究, 结果表明: 掺氮制备的金刚石膜的刻蚀主要集中在晶棱处, 经过4h刻蚀后其表面粗糙度由刻蚀前的4.761 μm下降至3.701 μm, 刻蚀对金刚石膜的表面粗糙度的影响较小; 而未掺氮制备的金刚石膜的刻蚀表现为晶面的均匀刻蚀, 晶粒坍塌,刻蚀4h后其表面粗糙度由刻蚀前的3.061 μm下降至1.083 μm. 刻蚀导致表面粗糙度显著降低. 上述差别的主要原因在于金刚石膜沉积过程中掺氮导致氮缺陷在金刚石晶棱处富集, 晶棱处电子发射加强, 引导离子向晶棱运动并产生刻蚀, 从而加剧晶棱的刻蚀. 而未掺氮金刚石膜,其缺陷相对较少且分布较均匀 ,刻蚀时整体呈现为 (111) 晶面被均匀刻蚀继而晶粒坍塌的现象. 关键词： 掺氮 金刚石膜 刻蚀 非对称磁镜场     

Excimer-laser etching on silicon

Studies have been made of poly- and single Si etching induced by excimer-laser irradiation of the silicon surfaces in halogenated gases. Etching was investigated for different conduction types, impurity concentrations and crystallographic planes. Chlorine atoms accept electrons generated in photoexcited, undoped p-type Si, thus becoming negative ions which are pulled into the Si. However, the n⁺-type Si is etched spontaneously by Cl^– as a result of the availability of conduction electrons. Fluorine atoms, with the highest electronegativity, take in electrons independent of whether the material is n- or p-type. And thus, the easy F^– ion penetration into Si causes spontaneous etching in both types. New anisotropic etching for n⁺ poly-Si is investigated because of its importance to microfabrication technology. Methyl methacrylate (MMA) gas, which reacts with Cl atoms, produces a deposition film on the n⁺ poly-Si surface. The surface, from which the film is removed by KrF (5 eV) laser irradiation, is etched by Cl atoms, while the film remains on the side wall to protect undercutting. However, with the higher photon energy for the ArF (6.4 eV) laser, the Si-OH bonds are broken and electron traps are formed. These electrontrapping centers are easily annealed out in comparison to the plasma-induced centers. Pattern transfer etching for n⁺ poly-Si has been realized using reflective optics. The problems involved in obtaining finer resolution etching are discussed.     

Investigation of interface roughness cross-correlation properties of optical thin films from total scattering losses

The interface roughness and interface roughness cross-correlation properties affect the scattering losses of high-quality optical thin films. In this paper, the theoretical models of light scattering induced by surface and interface roughness of optical thin films are concisely presented. Furthermore, influence of interface roughness cross-correlation properties to light scattering is analyzed by total scattering losses. Moreover, single-layer TiO₂ thin film thickness, substrate roughness of K9 glass and ion beam assisted deposition (IBAD) technique effect on interface roughness cross-correlation properties are studied by experiments, respectively. A 17-layer dielectric quarter-wave high reflection multilayer is analyzed by total scattering losses. The results show that the interface roughness cross-correlation properties depend on TiO₂ thin film thickness, substrate roughness and deposition technique. The interface roughness cross-correlation properties decrease with the increase of film thickness or the decrease of substrates roughness. Furthermore, ion beam assisted deposition technique can increase the interface roughness cross-correlation properties of optical thin films. The measured total scattering losses of 17-layer dielectric quarter-wave high reflection multilayer deposited with IBAD indicate that completely correlated interface model can be observed, when substrate roughness is about 2.84 nm.     

The effects of surface terminal bonds and microstructure of SiO2 aerogel films on dry etching

The effects of microstructure and surface terminal bonds of SiO₂ aerogel films on dry etching were investigated using Ar, SF₆, and C₂F₆ plasma gases. With Ar plasma etching, physical effect of ion bombardment on porous film was found. In residue-free SF₆ plasma etching, reactive etchant transport and high-mass ion bombardment were observed. With C₂F₆ plasma etching, fluorocarbon residue layer was revealed to maintain surface morphology as acting a barrier to radical transport and ion bombardment. An etching of 450°C-annealed SiO₂ aerogel showed that a dense surface induced the decrease in reaction area, inhibition of etchant transport, and then uniform etching.     

Surface morphology and surface chemical states of epitaxial Pb(Zr0.95Ti0.05)O3 thin films grown on SrTiO3(100) by sputter deposition

0.95 Ti_0.05)O₃ thin films of an orthorhombic perovskite structure were obtained on SrTiO₃(100) substrates by radio frequency sputter deposition. The surface morphology of the films was investigated with atomic force microscopy, scanning electron microscopy, and reflection electron microscopy. It is shown that the film surfaces are rather bumpy. There are undulations of about 400 nm in length in an in-plane direction. The mean roughness perpendicular to the surface is 39.6 nm, for the film thickness of 0.45 μm. The surface roughening was probably caused by island-shaped nucleation and growth during the film growth. It has also been found that some gorges and a number of small pits remain at the film surfaces. The surface chemical states of the films were characterized by using X-ray photoelectron spectroscopy. A Pb enrichment layer and a large amount of adsorbed oxygen have been found at the surfaces of the films. Near the film surface Pb and Zr exist mainly in the forms of, besides Pb(Zr,Ti)0₃, metal Pb, metal Zr, oxygen-chemisorbed Pb, and various lead oxides. In addition, a small amount of lead, whose binding energy of Pb 4f_7/2 is much lower than that of metal Pb, was observed at the film surfaces, but its chemical state is unknown up to now. Received: 2 June 1997/Accepted: 22 September 1997     

Investigation of epitaxial Nd1.85Ce0.15CuO4 − y film surface by low energy electron diffractometry

The surface of epitaxial Nd_1.85Ce_0.15CuO_{4 ? y} (001) (NCCO) film has been studied by low energy electron diffractometry (LEED) and photoelectron spectroscopy. Ar⁺ ion etching of a surface with subsequent annealing in oxygen at atmosphere pressure has been found to lead to the ordered structure restoration of surface layers with the symmetry type and lattice parameters corresponding to the NCCO phase. Annealing in vacuum at temperatures close to the boundary of thermodynamic phase stability results in the formation of epitaxial Ce_0.5Nd_0.5O_1.75 phase on a surface that is indicated in the LEED pattern as additional spots corresponding to the surface lattice (√2 × √2)R45°.     

非聚焦电子束照射SiO2薄膜带电效应

采用考虑电子散射、俘获、输运和自洽场的三维数值模型, 模拟了低能非聚焦电子束照射接地SiO₂薄膜的带电效应. 结果表明, 由于电子的迁移和扩散, 电子会渡越散射区域产生负空间电荷分布. 空间电荷呈现在散射区域内为正, 区域外为负的交替分布特性. 对于薄膜负带电, 电子会输运至导电衬底形成泄漏电流, 其暂态过程随泄漏电流的增加趋于平衡. 而正带电暂态过程随返回二次电子的增多而趋于平衡. 在平衡态时, 负带电表面电位随薄膜厚度、陷阱密度的增大而降低, 随电子迁移率、薄膜介电常数的增大而升高;而正带电表面电位受它们影响较小.     

X-ray spectroscopic examination of thin HfO<Subscript>2</Subscript> films ALD- and MOCVD-grown on the Si(100) surface

HfO₂ films 5 nm thick grown on Si(100) substrates by the methods of MOCVD hydride epitaxy and atomic layer deposition (ALD) are studied using X-ray photoelectron spectroscopy combined with Ar⁺ ion etching and X-ray reflectometry. It is found that (i) the ALD-grown HfO₂ films are amorphous, while the MOCVD-grown films show signs of a crystal structure; (ii) the surface of the ALD-grown films is more prone to contamination and/or is more reactive; and (iii) the amount of interfacial silicon dioxide in the case of the MOCVD-grown film is greater than in the case of the films synthesized by ALD. It is also shown that the argon ion etching of the HfO₂ film results in the formation of a metallic hafnium layer at the interface. This indicates that HfO₂ can be used not only as a gate dielectric but also as a material suitable for fabricating nanodimensional conductors by direct decomposition.     

Magnetic properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> surface

The magnetic properties of the magnetite Fe₃O₄(110) surface have been studied by spin resolved Auger electron spectroscopy (SRAES). Experimental spin resolved Auger spectra are presented. The results of calculation of Auger lines polarization carried out on the basis of electronic state density are presented. Problems related to magnetic moments of bivalent (Fe²⁺) and trivalent (Fe³⁺) ions on the Fe₃O₄(110) surface are discussed. It is established that the deposition of a thin bismuth film on the surface results in significant growth of polarization of iron Auger peaks, which is due to additional spin-orbit scattering of electrons by bismuth atoms.     

Influence of electron irradiation of the NOVER-1 vacuum resist on its resistance to ionbeam etching

The influence of electron irradiation on the resistance of the NOVER-1 resist to ion-beam etching is studied. Etching is carried out by argon ions with energies between 300 and 2500 eV. It is found that, depending on the energy and angle of incidence of the ions on the surface of the resist, electron irradiation may either speed up or slow down the NOVER-1 etching. A clear correlation is observed between the penetration depth of the ions in the resist and the influence of the electron irradiation on the resistance of the resist to etching. At ion energies higher than 500 eV (ion penetration depth ≳3.5 nm) the resistance decreases, passes through a minimum at low electron irradiation doses, and returns to the etching rate of the initial resist at high doses. For glancing etching angles (∼ 70° to the surface normal) and low ion energies (300 eV), i.e., small ion penetration depths (≲2.5 nm), an electron-irradiated resist is etched more slowly than the initial resist at all the electron irradiation doses studied. This effect may be used to enhance the resistance of resist structures whose height exceeds their width, which in this case is determined mostly by the rate of etching of the inclined facets. Zh. Tekh. Fiz. 68, 140–142 (January 1998)     

Arc plasma jet cleaning of the silicon surface before CoSi2/Si contact formation

Cleaning of the silicon surface before Co film deposition is a key procedure in the synthesis of silicide (CoSi₂) and, hence, in the production of the metal-semiconductor contact. This study deals with a new method of surface cleaning using arc plasma jet treatment (APJT) at atmospheric pressure. The results show that cleaning of the Si surface using APJT (Ar/CCIF₃) improves the Schottky barrier contact parameters in comparison with conventional wet HF final cleaning and additional cleaning using in situ Ar-ion-beam sputter etching. Moreover, substantially longer time of wafer exposure to air between final cleaning and metal deposition is acceptable. Auger electron spectroscopy shows that APJT removes oxygen from the Si surface.     

Atomic force microscopy investigation of surface roughness generated between SiO2 micro-pits in CHF3/Ar plasma

The present paper investigates the surface roughness generated by reactive ion etching (RIE) on the location between silicon dioxide (SiO₂) micro-pits structures. The micro-pit pattern on polymethyl methacrylate (PMMA) mask was created by an electron beam lithography tool. By using PMMA as a polymer resist mask layer for pattern transfer in RIE process, the carbon (C) content in etching process is increased, which leads to decrease of F/C ratio and causes domination of polymerization reactions. This leads to high surface roughness via self-organized nanostructure features generated on SiO₂ surface which was analyzed using atomic force microscopy (AFM) technique. The etching chemistry of CHF₃ plasma on PMMA masking layer and SiO₂ is analyzed to explain the polymerization. The surface root-mean-square (RMS) roughness below 1 nm was achieved by decreasing the RF power to 150 W and process pressure lower than 10 mTorr.     

Surface chemistry: from vibrational spectroscopy to photoemission spectromicroscopy

Vibrational spectroscopy and core-level photoelectron spectroscopy are two of the most powerful tools for surface chemical analysis. We have used both techniques in conjunction with others to study hydrocarbon radical interactions with metal and semiconductor surfaces as well as thin film deposition processes. These include the investigations of CH₂ and CH₃ reactions on Cu by high resolution electron energy loss spectroscopy (HREELS), and GaN formation from Ga(CH₃)₃ and NH₃ on SiC by SR-PES. The vibrational analysis has revealed rich surface chemistry of the radicals while the photoemission study has led us to develop new approach for probing ultrafine structures. The effort involves the construction of a scanning photoemission spectromicroscope (SPEM) coupled to a synchrotron radiation light source. Recent results are presented in this brief report.     

Formation of CrSi2 nanoislands on Si(111)7 × 7 and epitaxial growth of silicon overlayers in Si(111)/CrSi2 nanocrystallites/Si heterostructures

Low-energy electron diffraction and differential reflectance spectroscopy are used to study the self-formation of chromium disilicide (CrSi₂) nanoislands on a Si(111) surface. The semiconductor properties of the islands show up even early in chromium deposition at a substrate temperature of 500°C, and the two-dimensional growth changes to the three-dimensional one when the thickness of the chromium layer exceeds 0.06 nm. The maximal density of the islands and their sizes are determined. The MBE growth of silicon over the CrSi₂ nanoislands is investigated, an optimal growth temperature is determined, and 50-nm-thick atomically smooth silicon films are obtained. Ultraviolet photoelectron spectroscopy combined with the ion etching of the specimens with embedded nanocrystallites demonstrates the formation of the valence band, indicating the crystalline structure of the CrSi₂. Multilayer epitaxial structures with embedded CrSi₂ nanocrystallites are grown.