X-ray determination of the residual stresses in thin aluminum films deposited on silicon substrates

Results of x-ray strees measurements on highly [111] textured thin aluminum films deposited on [100] silicon wafers were reported. Due to the texturing the conventional sin²ϕ technique for polycrystalline materials was found to be difficult to use. X-ray stress measurements were thus made as if the thin films were single crystals with [111] planes parallel to the substrate. The calculated stresses for unannealed specimens were found to be compressive and small, approximately -20 to -30 MPa. The calculated stresses for specimens annealed at 450°C were found, after a waiting time of 34 days, to be tensile and larger, approximately 120 to 140 MPa.     

Relaxation of extrinsic and intrinsic stresses in germanium substrates with silicon films

Si films were deposited on Ge substrates at 400°C by two different Physical Vapor Deposition techniques: (A) ion beam sputtering and (B) magnetron sputtering. The intrinsic stresses in the as-deposited films were measured to be compressive and much greater in samples (A), about −1500 to −2000 MPa than in samples (B), about −300 to −500 MPa. The substrates were subsequently exposed to thermal treatments for varying times at 800°C. In the lower stressed (B) samples, the films had relaxed and reduced the overall curvature of the structure whereas in the high stresses (A) samples, an irreversible large increase in the substrate curvature was found to occur. This indicated that plastic deformation in the Ge substrates itself had occurred.     

Correlation between surface whisker growth and interfacial precipitation in aluminum thin films on silicon substrates

When subjected to thermal excursions, aluminum thin films on silicon substrates often show whisker or hillock growth on the film surface, along with formation of Si precipitates at the interface. This study demonstrates that the two effects are related, and that interfacial Si precipitation directly influences the growth of Al whiskers on the film surface during isothermal annealing at 300–550 °C. The density of whiskers and hillocks not only increases with increasing annealing temperatures where the film is under greater compressive stress, but also during longer hold times which should relieve the stress. At high temperatures and long annealing times, extensive Si precipitation, eventually leading to a bi-modal precipitate size distribution, occurs continuously at the interface. The total amount of Si precipitates far exceeds the solubility limit of Si in the Al thin film, and can generate enough compressive stress in the film to drive surface whisker growth. By continuously augmenting film stress, interfacial Si precipitation supplies the driving force for whisker/hillock formation on the Al-film surface.     

Frequency dependence of superfluid onset temperature of4He films on oscillating substrates

We have studied the frequency dependence of the superfluid onset for⁴He films on Mylar substrates using a two-torsional-oscillators technique. A peak of the dissipation accompanied by the superfluid onset appears at higher temperatures for 2009 Hz than for 530 Hz. The temperature difference T_p between the two peaks is 2.0 ± 0.5 mKfor coverages with the onset temperature T_c of 1.4 K, and increases by a factor of three with decreasing T_c from 1.4 to 0.95 K. In the temperature dependence of the dissipation, the dissipation width also increases by a factor of three with decreasing T_c from 1.4 to 0.95 K. The T_c dependencies of T_p and the dissipation width indicate that an intrinsic parameter D/r₀ ² of a vortex decreases with the superfluid onset temperature, where D is a diffusion constant and r₀ a core radius.     

热丝CVD法低温制备的多晶硅薄膜质量对衬底依赖性的研究

以SiH4和H2作为反应气体,采用HWCVD的方法分别在石英玻璃、AZO、Si（100）和Si（111）衬底上制备了多晶硅薄膜。利用X射线衍射（XRD）,拉曼（Raman）光谱和傅里叶红外（FT-IR）吸收光谱研究了不同衬底对多晶硅薄膜的择优取向、晶化率和应力的影响,用SEM观察了多晶硅薄膜的表面形貌。研究发现在4种衬底上生长的多晶硅薄膜均为（111）择优取向。单晶硅片对多晶硅薄膜有很强的诱导作用,并且Si（111）的诱导作用优于Si（100）的诱导作用。AZO对多晶硅薄膜生长也有一定的诱导作用。通过计算薄膜晶态比,得到除以石英为衬底的样品外,其它3种样品的晶态比均在90%以上,尤其以单晶硅片为衬底的样品更高。石英玻璃、AZO和Si（100）上生长的多晶硅薄膜中均存在压应力。     

Nanocrystalline silicon thin films on PEN substrates

We study the structural and electrical properties of intrinsic layer growth close to the transition between amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H), deposited on glass and PEN without intentional heating. These samples showed different behaviour in Raman shift and XRD spectra when compared with that of samples deposited at 200 °C. Electrical properties of these films also reflect the transition between a-Si:H and nc-Si:H, and put in evidence some differences between the microstructure of the films grown on PEN and on glass.P- and n-doped layers were deposited onto glass substrate without intentional heating and at 100 °C with thicknesses ranging from 1000 nm to 35 nm. Conductivity measurements indicate the capability of doping this material, but, for very thin layers, substrate heating was found to be essential.     

Optical interference phenomena in silicon films on oxidized silicon and similar two-film systems

In certain thickness ranges, the curves of reflectivity versus wave number for silicon films deposited on oxidized silicon, and for other similar two-film systems, resemble beats. If the oxide thickness is not too large, the values of the wave number at the extremes of the reflectivity can be described in terms of almost quarter odd-order numbers and an additional thickness for the optically effective thickness of the silicon film. A simple graphical evaluation method for the thickness of the silicon film with known refractive index is derived. If the oxide thickness is not too small, it too can be measured.     

Facile fabrication of stable superhydrophobic films on aluminum substrates

Compact and uniform layered double hydroxides thin films were fabricated on aluminum substrates using a simple solution-immersion process; upon chemical modification with perfluorosilane, the wettability of the aluminum surface changed from hydrophilic to superhydrophobic. The products were characterized by scanning electron microscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy. It is confirmed that the synergic effect of the surface morphology and the surface free energy contribute to this unique surface water repellence. In addition, the superhydrophobic films possess long-term storage stability and good adhesion strength to aluminum substrates, which enhance their potential practical applications.     

Growth of CdTe films on Ni-coated microtextured silicon substrates

Based on modeling and calculation results and using appropriate photomasks, we produced microtextured Si substrates, which were then coated with a Ni layer. Next, polycrystalline CdTe films were produced on the Ni by quasi-closed space growth. Their surface morphology was examined by optical microscopy and scanning electron microscopy. We calculated the stress induced in such CdTe/Ni/Si structures by the lattice mismatch and thermal expansion mismatch between the materials in contact.     

Structure of diamond polycrystalline films deposited on silicon substrates

The article presents results of structural studies of polycrystalline diamond thin films deposited by hot filament CVD on silicon substrates. The films were characterized using Scanning Electron Microscopy (SEM), Raman Spectroscopy (RS), Electron Backscattered Diffraction (EBSD), Energy Dispersive Spectroscopy (EDS) and Secondary Ion Mass Spectroscopy (SIMS). Both the EBSD patterns and Raman spectra confirm that the grains visible in the electron micrographs are diamond micro-crystallites. The residual stress in the films is found to be in the range between −4.29 GPa and −0.56 GPa depending on the sample thickness. No evidence of lonsdalite and graphite has been registered in the polycrystalline material of the investigated samples. Evidence of the existence of silicon carbide at the diamond/silicon interface is presented. It is also suggested that an amorphous carbonaceous film covers the silicon surface in the regions of holes in the thin diamond layers.     

The plasma anodization to exhaustion of thin aluminium films on silicon substrates

Plasma anodization is a low temperature process that is of interest in the preparation of insulating films on semiconductors because of its effect in reducing the possibility of dissociation of the semiconductor.It has previously been applied to the formation of aluminum oxide layers on silicon and it is now demonstrated that the onset of substrate oxidation can be recognized electrically during the anodization. A model for the anodic process is presented in terms of electron and ion transport through the growing layer. Chemical information is presented and sources of contamination are identified. The films have high resistivities and breakdown strengths and MOS measurements are presented.It is expected that this monitoring technique could be applied to other material systems.     

Amplitude-dependent internal friction in copper thin films on silicon substrates

Internal friction in copper thin films 0.2–1.5 μm thick on silicon substrates has been measured between 180 and 340 K as a function of strain amplitude. Analysis of the amplitude-dependent internal friction in the copper films shows the relation between the plastic strain of the order of 10⁻⁹ and the effective stress on dislocation motion. The stress–strain curves thus obtained for the copper films tend to shift to a higher stress with decreasing film thickness and also with decreasing temperature, both indicating a suppression of microplastic flow. It is concluded that the microflow stress at a constant level of the plastic strain varies inversely with the film thickness at all temperatures examined. The film thickness effect in the microplastic range can be explained on the basis of a dislocation-bowing model.     

Diffusion of aluminum into silicon nitride films

Aluminum diffusion into silicon nitride films at temperatures in the range 450–530°C was studied by Auger electron spectroscopy in conjunction with depth profiling. The activation energy for the diffusion of aluminum and the diffusion coefficient were found to be 2.0±0.3 eV and (7.3±3.5) x 10^-3 cm² s^-1, respectively. The chemical effects in the KLL aluminum Auger spectra together with the compositional depth profiles suggest that the migration of aluminum is dominated by volume diffusion which involves the reaction of aluminum with oxygen.     

The nature of stresses in hot-filament chemical vapour deposited diamond thin films on WC substrates

The nature of film stresses in hot-filament chemical vapour deposited (HFCVD) diamond thin films on tungsten carbide substrates, is reported. Commercial WC substrates were subjected to various surface treatments. Subsequently, they were coated with a diamond film and examined for stresses using X-ray diffraction. All but one of the stress measurements indicated various levels of compressive stresses in the film and at the film–substrate interface. These stresses are compared with those obtained by other researchers. Intrinsic film stresses were also computed for diamond films and found to be tensile. WC drills, of 0.125 in. diameter, were also diamond coated and the stress levels measured along drill flanks and flutes. Significant variations were found in these stresses, and the results were analysed from a film–substrate adhesion perspective.     

Influence of a methane atmosphere on the temperature dependence of the conductivity of polycrystalline silicon films

The possibility of using polycrystalline silicon films in gas sensors is investigated. An analysis is made of the influence of a small quantity of methane admitted into the surrounding medium on the temperature dependence of the layer resistivity of films doped with acceptor impurities. It is established that the resistivity increases appreciably in the temperature range between 470 and 500°. Pis’ma Zh. Tekh. Fiz. 24, 16–19 (May 26, 1998)     

Control of the structure in zone-melted silicon films on amorphous substrates

In situ observations of a crystallization front (solid-liquid interface) during zone-melting recrystallization of thin silicon films on amorphous substrates by laser beams are described. Cellular structure of the front is investigated, and a transition from faceted to rounded front depending on thickness of the film is noted.     

Si diffusion in magnetron sputtered silicon carbide films deposited on silicon and carbon substrates

Self-diffusion of silicon in magnetron sputtered silicon carbide films deposited on different substrates (crystalline silicon and glassy carbon) is investigated. Since crystallization of amorphous silicon carbide films strongly depends on the substrate, the diffusivity of silicon is expected to depend on the substrate as well. Isotope hetero-structures and secondary ion mass spectrometry were used for analysis. For amorphous samples an upper limit of the diffusivity of 1 × 10^− 21 m²/s is derived at 1100 C°. For crystallized films diffusivities between 1350 °C and 1600 °C are found to be not significantly different for the two types of substrates. For samples deposited on glassy carbon substrates an activation enthalpy ΔH_D = (8.7 ± 0.9) eV was found for the self-diffusion of Si. The consequences of our findings for crystallization are discussed.     

Characterization of laser annealed polycrystalline silicon films on various substrates

The structure and property of eximer laser annealed poly-Si films on various substrate materials such as MoW, Cr, were studied. It was found that the crystallinity of the film depended on the recrystallization energy density and substrate materials. The crystallinity of the film on substrate was the highest quality, and the higher the thermal conductivity of the substrate, the poorer the crystallinity of the poly-Si films at the same laser energy density. In the lower laser energy region than optimum, the grain size and surface roughness were increased with increasing laser power due to the increase of the crystallinity and decreased intrinsic stress. On the other hand, in the higher power region than optimum, with the increase of laser power, X-ray intensity and grain size were decreased due to the fast solidification velocity. There was no metal diffusion into poly-Si film but small amount of Si, less than 3 atomic percent, diffused into the metal film during the recrystallization process.     

水热法制备Si基片状ZnO微晶薄膜

采用真空蒸镀法在Si(100)基底上制备了六角片状Zn微晶薄膜,并由N2H4·H2O-水热体系制备了Si基片状ZnO微晶薄膜。XRD、SEM及EDS测试与分析结果表明,纤锌矿结构片状ZnO微晶长度约1μm、厚度约100nm,几乎垂直于Si基面,且在基面上随机组合成连续薄膜。联系室温Si基Zn微晶薄膜氧化物形貌,以"氢氧化锌脱水"反应解释了Si基片状ZnO微晶薄膜的生长机制。光致发光谱测试分析表明,ZnO微晶薄膜有强的近带边紫外光发射和弱的缺陷发射。