Untersuchung dünner Schichten mittels Röntgenreflektometrie

Thin film characterization by means of X‐ray reflectometry X‐ray reflectometry and diffractometry are widely used non‐destructive methods to characterize thin films in the total thickness range which is typically between 2nm and approximately 500nm. On special arrangements a resolution up to 1000nm layer thickness has been demonstrated. Layer stack morphology, surface topography, layer structure, material density, single layer or period thickness and surface and interface roughness are the typical structural parameters both of single layers and of multilayers which can be described by the measured data. The performance of the measurement setup is mainly influenced by the parameters of the incident X‐ray beam like beam divergence, monochromatism and photon energy. In the following the influence of the optical components in the beam path to angle and energy resolution of X‐ray reflectometry is discussed.     

铝诱导晶化法低温制备多晶硅薄膜

为了满足在普通玻璃衬底上制备多晶硅薄膜晶体管有源矩阵液晶显示器,低温（＜６００℃）制备高质量多晶硅薄膜已成为研究热点．本文研究了一种低温制备多晶硅薄膜的新工艺：金属诱导非晶硅薄膜低温晶化法．在非晶硅薄膜上蒸镀金属铝薄膜,并光刻形成铝膜图形,而后于氮气保护中退火．利用光学显微镜和拉曼光谱等测试方法,研究了Ａｌ诱导下非晶硅薄膜的晶化过程,结果表明;在５６０℃退火６ｈ后;铝膜下的非晶硅已完全晶化,确定了所制备的是多晶硅薄膜．初步探讨了非晶硅薄膜金属诱导横向晶化机理．     

A low‐cost dehydrogenation system of amorphous silicon thin films used for fabricating low‐temperature polycrystalline silicon

Low‐temperature polycrystalline silicon thin‐film transistors were widely employed in active‐matrix flat‐panel displays and giant microelectronics. In general, a‐Si thin films prepared by plasma‐enhanced chemical vapor deposition contain hydrogen. To prevent the ablation caused by sudden hydrogen eruption during excimer laser crystallization (ELC), two dehydrogenation systems are developed in this study to reduce hydrogen content before excimer laser crystallization. One is a ceramic heater‐based dehydrogenation system and the other is a quartz tube radiant heater‐based dehydrogenation system. The hydrogenated amorphous silicon (a‐Si : H) thin films prepared by plasma‐enhanced chemical vapor deposition are dehydrogenated by both systems. Fourier‐transform infrared absorption spectra revealed that the hydrogen content reduces after dehydrogenation processing. Raman measurements confirmed that the a‐Si : H thin films are still amorphous phase. The major potential advantages of quartz tube radiant heater‐based dehydrogenation system include rapid heating speed, good dehydrogenation quality, small footprint and low cost. Two‐steps temperature rise method is a good candidate for dehydrogenation processing because it provides sample with low thermal distortion.     

Roughness of amorphous, polycrystalline and hemispherical-grained silicon films

We have performed atomic-force-microscopy studies of the roughness and spatial and correlation properties of the surface for three typical LPCVD films of silicon: amorphous and polycrystalline films with a relatively smooth surface, as well as polycrystalline films with hemispherical grains (HSG-Si) having considerable surface roughness. As follows from analysis of the correlation function and power spectral density function, the model of a self-affine surface is suitable for describing morphology of amorphous and polycrystalline silicon films, while the model of a mounded surface is preferable for HSG-Si films.     

Growth of polycrystalline-silicon thin films on glass

Borosilicate glass was chosen as a substrate for solution growth of silicon due to its potential role as the superstrate of a solar module. The deposition of polycrystalline silicon on glass from solutions containing aluminium or magnesium is reported. Island growth was usually obtained when the deposition temperature was below 750 C. Large-grain, continuous, silicon thin films with an area of 10 cm² were grown on glass substrates at temperatures around the softening points of the glass. The growth of silicon on glass can be explained on the basis that the presence of aluminium and magnesium in the solution reduces SiO₂ and exposes silicon on the glass surface. The silicon-rich surface improves the wetting of the glass by the solution and acts as seeding sites for silicon nucleation. The periodic-regrowth technique was used to improve the quality of the polycrystalline silicon thin films deposited on the glass substrates. Periodic repetition of the melt-back and regrowth procedures removed the small-grained crystals, suppressed the rapid growth of crystals perpendicular to the substrate and enhanced the growth of slower-growing crystals in the lateral direction. This process markedly improved the smoothness, the grain size, the crystal quality and the (1 1 1) preferred orientation of the silicon thin films. Diode characteristics were obtained for p-n junction devices made on these polycrystalline silicon thin films deposited on glass substrates.     

Exciton Recombination in Formamidinium Lead Triiodide: Nanocrystals versus Thin Films

The optical properties of the newly developed near‐infrared emitting formamidinium lead triiodide (FAPbI₃) nanocrystals (NCs) and their polycrystalline thin film counterpart are comparatively investigated by means of steady‐state and time‐resolved photoluminescence. The excitonic emission is dominant in NC ensemble because of the localization of electron–hole pairs. A promisingly high quantum yield above 70%, and a large absorption cross‐section (5.2 × 10^?13 cm^?2) are measured. At high pump fluence, biexcitonic recombination is observed, featuring a slow recombination lifetime of 0.4 ns. In polycrystalline thin films, the quantum efficiency is limited by nonradiative trap‐assisted recombination that turns to bimolecular at high pump fluences. From the temperature‐dependent photoluminescence (PL) spectra, a phase transition is clearly observed in both NC ensemble and polycrystalline thin film. It is interesting to note that NC ensemble shows PL temperature antiquenching, in contrast to the strong PL quenching displayed by polycrystalline thin films. This difference is explained in terms of thermal activation of trapped carriers at the nanocrystal's surface, as opposed to the exciton thermal dissociation and trap‐mediated recombination, which occur in thin films at higher temperatures.     

双纳米硅p层优化非晶硅太阳能电池

采用等离子体增强化学气相沉积(Plasma Enhanced Chemical Vapor Deposition,PECVD)技术在高功率密度、高反应气压和低衬底温度下制备出不同氢稀释比RH的硅薄膜.高分辨透射电镜(High-Resolution Transmission Electron Microscopy,HRT...     

Fabrication of diamond microstructures for microelectromechanical systems (MEMS) by a surface micromachining process

Selective polycrystalline diamond thin film has been grown on a silicon dioxide/silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950°C. A simple process flow has been developed to fabricate diamond microstructures such as diamond beams and cantilever beams using surface micromachining and photolithography for the first time. Scanning electron and optical microscopy has been used to characterize the surface micromachined diamond microstructures.     

Characterization of hypervelocity impact craters on chemical vapour-deposited diamond and diamond-like carbon films

Microwave plasma chemical vapour-deposited (CVD) process has been used to grow polycrystalline diamond films over silicon substrates. Diamond-like carbon (DLC) thin films were grown over silicon substrates using a microwave plasma disc reactor. Reactant gases of CH4 and H2 were used in both CVD processes. Some preliminary feasibility tests were performed on the possible applicability of diamond and diamond-like carbon thin films for space-protective applications against artificially simulated electrically actuated plasma drag hypervelocity impact of olivine particles. As-deposited films were analysed by Raman for their chemical nature. The morphology and dimensions of hypervelocity impact craters in diamond and DLC films was also studied by scanning electron microscopy (SEM) and optical microscopy. The velocity of debris particles was determined by high-speed photography using a streak camera. The size of the impact particles was determined by measuring the size of the holes formed in the mylar sheet mounted just above the target diamond and DLC film/silicon and coordinates of the impact sites were determined using the same apparatus. This revised version was published online in November 2006 with corrections to the Cover Date.     

溅射功率对ZnO：Si透明导电薄膜性能的影响

采用直流磁控溅射法在室温玻璃基片上制备出了掺硅氧化锌（ZnO：Si）透明导电薄膜,研究了溅射功率对ZnO：Si薄膜结构、形貌、光学及电学性能的影响,实验结果表明,溅射功率对ZnO：Si薄膜的生长速率、结晶质量及电学性能有很大影响,而对其光学性能影响不大。实验制备的ZnO：LSi薄膜为六方纤锌矿结构的多晶薄膜,且具有垂直于基片方向的c轴择优取向。当溅射功率从45W增加到105W时,薄膜的晶化程度提高、晶粒尺寸增大,薄膜的电阻率减小;当溅射功率为105W时,薄膜的电阻率达到最小值3．83~104n·cm,其可见光透过率为94．41％。实验制备的ZnO：Si薄膜可以用作薄膜太阳能电池和液晶显示器的透明电极。     

基于光谱干涉椭偏法的薄膜厚度测量

薄膜厚度的测量在芯片制造和集成电路等领域中发挥着重要作用。椭偏法具备高测量精度的优点,利用宽谱测量方式可得到全光谱的椭偏参数,实现纳米级薄膜的厚度测量。为解决半导体领域常见的透明硅基底上薄膜厚度测量的问题并消除硅层的叠加信号,本文通过偏振分离式光谱干涉椭偏系统,搭建马赫曾德实验光路,实现了近红外波段硅基底上膜厚的测量,以100 nm厚度的二氧化硅薄膜为样品,实现了纳米级的测量精度。本文所提出的测量方法适用于透明或非透明基底的薄膜厚度测量,避免了检测过程的矫正步骤或光源更换,可应用于化学气相沉积、分子束外延等薄膜制备工艺和技术的成品的高精度检测。     

ZnO transparent thin films for gas sensor applications

Zinc oxide (ZnO) transparent thin films were deposited onto silicon and Corning glass substrates by dc magnetron sputtering using metallic and ceramic targets. Surface investigations carried out by Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) have shown a strong influence of deposition technique parameters on film surface topography. Film roughness (RMS), grain shape and dimensions are correlated with the deposition technique parameters as well as with the target material. XRD measurements have proven that the dc sputtered films are polycrystalline with the (002) as preferential crystallographic orientation. AFM analysis of thin films sputtered from a ceramic target has shown a completely different surface behavior compared with that of the films grown from a metallic target. This work demonstrates that the target material and the growth conditions determine the film surface characteristics. The gas sensing characteristics of these films are strongly influenced by surface morphology. Thus correlating the optical and electrical film properties with surface parameters (i.e. RMS and Grain Radius) can lead to an enhancement of the material's potential for gas sensing applications.     

Characterization of vapor-deposited l-leucine nanofilm

X-ray reflective measurements (XRR), atomic force microscopy and single wavelength ellipsometry were used to investigate the optical properties of thin l-leucine films deposited onto silicon substrates. The ellipsometry data (Ψ,Δ) were fitted with a four-layer-model, and the optical refractive index of the l-leucine film measured with ellipsometry was determined to be 1.37. With the conventional effective medium approximation theory and the ellipsometry results, the density of the l-leucine nanofilm was determined to be 70% (0.81 g/cm³) of crystalline l-leucine. This value was in good agreement with the density of 69% (0.80 g/cm³) obtained with XRR measurement. The ellipsometry measurements also enabled us to estimate the surface roughness or absorption layer of the film. This procedure of combined XRR and ellipsometry measurements could be a powerful tool for the determination of the (otherwise hard-to-determine) refractive index in thin organic material films with a rough surface layer.     

Silicon Wafer Surface-Temperature Monitoring System for Plasma Etching Process

A thermoreflectance temperature measuring system was developed with the aim to realize monitoring of the silicon wafer surface temperature during plasma etching. The thermoreflectance detects variations in temperature through changes in optical reflectance. To overcome such difficulties as low sensitivity and limitation in installation space and position for in situ measurements, the differential thermoreflectance utilizing two orthogonal polarizations was introduced. Noise such as fluctuations in the incident beam intensity or changes of loss in the optical path would affect both polarizations equally and would not affect the measurement. The large angle of incidence of the beam allows measurement to be performed from outside the viewing ports of existing plasma etching process chambers through the gap between the plasma electrode and the silicon wafer. In this article, an off-line measurement result is presented, with results for bare wafers as well as for wafers with metal depositions. A prototype system developed for tests in plasma etching facilities in a production line is described.     

Effect of post annealing on structural and optical properties of ZnO thin films deposited by vacuum coating technique

We report the effect of annealing temperature on structural, electrical and optical properties of polycrystalline zinc oxide thin films grown on p-type silicon (100) and glass substrates by vacuum coating technique. The XRD and AFM measurements confirmed that the thin films grown by this technique have good crystalline hexagonal wurtzite structures and homogenous surfaces. The study also reveals that the rms value of thin film roughness increases from 6 to 16 nm, the optical band gap increases from 3.05 to 3.26 eV and resistivity from 0.3 to 5 Ωcm when the post-deposition annealing temperature is changed from 400 to 600 °C. It is observed that ZnO thin film annealed at 600 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.     

Investigation of the substrate effect for Zr doped ZnO thin film deposition by thermionic vacuum arc technique

ZnO is a fundamental wide band gap semiconductor. Especially, doped elements change the optical properties of the ZnO thin film, drastically. Doped ZnO semiconductor is a promising materials for the transparent conductive oxide layer. Especially, Zr doped ZnO is a potential material for the high performance TCO. In this paper, ZnO semiconductors were doped with Zr element and microstructural, surface and optical properties of the Zr doped ZnO thin films were investigated. Zr doped ZnO thin films were deposited thermionic vacuum arc (TVA) technique. TVA is a rapid and high vacuum deposition method. A glass, polyethylene terephthalate and Si wafer (111) were used as a substrate material. Zr doped ZnO thin films deposited by TVA technique and their substrate effect investigated. As a results, deposited thin films has a high transparency. The crystal orientation of the films are in polycrystal formation. Especially, substrate crystal orientation strongly change the crystal formation of the films. Substrate crystal structure can change the optical band gap, microstructural properties and deposited layer formation. According to the atomic force microscopy and field emission scanning electron microscopy measurements, all deposited layer shows homogeneous, compact and low roughness. The band values of the deposited thin film were approximately found as to be 3.1–3.4 eV. According to the results, Zr elements created more optical defect and shifted to the band gap value towards to blue region.     

Comparative study of physical properties of vapor chopped and nonchopped Al2O3 thin films

Aluminium oxide being environmentally stable and having high transmittance is an interesting material for optoelectronics devices. Aluminium oxide thin films have been successfully deposited by hot water oxidation of vacuum evaporated aluminium thin films. The surface morphology, surface roughness, optical transmission, band gap, refractive index and intrinsic stress of Al₂O₃ thin films were studied. The cost effective vapor chopping technique was used. It was observed that, optical transmittance of vapor chopped Al₂O₃ thin film showed higher transmittance than the nonchopped film. The optical band gap of vapor chopped thin film was higher than the nonchopped Al₂O₃, whereas surface roughness and refractive index were lower due to vapor chopping.     

单层二氧化铪（HfO2）薄膜的特性研究

利用电子束蒸发、离子束辅助沉积和离子束反应溅射三种制备方法制备了单层HfO2薄膜,对薄膜样品的晶体结构、光学特性、表面形貌以及吸收特性进行了研究。实验结果表明,薄膜特性与制备工艺有着密切的关系。电子束蒸发和离子束反应溅射制备的薄膜为非晶结构,而离子束辅助制备的薄膜为多晶结构。电子束蒸发制备的薄膜折射率较低,薄膜比较疏松,表面粗糙度较小,吸收相对较小,而离子束辅助以及离子束反应溅射制备的薄膜折射率较高,薄膜的结构比较致密,但表面粗糙度较大,吸收相对较大。不同制备工艺条件下薄膜的光学能隙范围为5.30～5.43eV,对应的吸收边的范围为228.4～234.0nm。     

氧化铟薄膜制备及其特性研究

采用射频磁控溅射法在玻璃衬底上制备氧化铟薄膜,通过测试原子力显微镜、X射线衍射、X射线光电子谱、紫外可见分光光度计以及霍尔效应,研究了氧化铟薄膜的结构和光、电特性.实验发现,氧化铟薄膜表面粗糙度随着生长温度的升高而增大.X射线衍射结果表明薄膜为立方结构的多晶体,并且随着生长温度的升高,可以看到氧化铟薄膜的晶粒变大以及半高宽减小,这也说明结晶质量的改善.在可见光范围的透射率超过90%.同时,在氩气氛围下制备的薄膜迁移率最大,其电阻率、霍尔迁移率和电子浓度分别达到了0.31Ω.cm、9.69 cm2/(V.s)和1×1018cm-3.退火处理可以改善氩氧氛围下制备的薄膜的电学性能.     

Influence of DC magnetron sputtering parameters on the properties of amorphous indium zinc oxide thin film

Amorphous or crystalline indium zinc oxide (IZO) thin films, which are highly transparent and conducting, were deposited by DC magnetron sputtering. X-Ray diffraction technique was used for analyzing microstructures of the films, and also differential thermal analysis was performed for observing their crystallization behavior. The IZO thin films prepared were crystallized at much higher temperature than ITO films were. The crystallized samples showed (222) preferred orientations. By varying process parameters, the optimum conditions for the highest electrical conductivity and optical transmittance, and the lowest surface roughness were found. The resistivity of IZO films decreased as the deposition temperature increased until 250 °C, but sharp rise occurred at or above 300 °C. The extinction coefficients diminished in the films prepared with the conditions of higher deposition temperature, sputtering gas of light mass, and heat treatment. However, excessive amount of oxygen flow during deposition brought about the increase of the extinction coefficients. The variations of extinction coefficients mainly influenced the transmittance of the samples. On the basis of X-ray photoelectron spectroscopy analysis, atomic force microscopy measurement, spectroscopic ellipsometry and spectrophotometer measurement, several characteristics of IZO thin films were discussed comparing with those of ITO thin films. Very low surface roughness of IZO thin films could satisfy the requirement for organic light-emitting diode.