Mathematical modeling and interpretation of reactive plasma chemistry

A problem of much recent technological interest is the analysis and interpretation of the chemistry of audiofrequency plasma enhanced chemical vapor deposition of thin films. In this process, low pressure methane gas is input into a reactor chamber and a low-current, high-voltage audiofrequency electric discharge applied. The energetic electrons thus produced bombard the methane molecules, fragmenting them, and causing radical and ion formation. These new species go on to form a range of products under various operating conditions from soot-like amorphous carbon, to diamond-like carbon. Despite the increasing experimental understanding of reactive organic plasma dynamics, the chemical kinetics of the reactions in the gas phase is still not completely understood: quite different species densities are found in different regions of the discharge system implying spatially inhomogeneous physiochemical processes. The experimental problem is first outlined, and a simple physiochemically-motivated reaction-advection-diffusion model of the reactive plasma chemistry described. Results of the kinetics models are presented and discussed in terms of the input model parameters and related to surface deposition.     

Isochronal Studies of α‐Si:H Crystallization and the Performance of it's Schottky Barriers

Hydrogenated amorphous silicon films (α‐Si:H) were crystallized employing a metal induced crystalline (MIC) technique. Structural changes during annealing these films at 300 °C for different periods (0‐300 minutes) were obtained by XRD. Al was used as a metal induced crystalline for α‐Si:H produced by ultra high vacuum (UHV) plasma enhanced chemical vapor deposition (PECVD). XRD shows that crystallization of the interacted α‐Si:H film underneath Al initiates at 300 °C for 15 minutes. A complete crystallization was obtained after annealing for 60 minutes. A gold dot was evaporated onto α‐Si:H films, which annealed for different periods to form Schottky barriers. Electrical properties of Au/α‐Si:H were calculated such as the ideality factor, n, barrier height, Φ_B, donor concentration, N_D, and the diffusion voltage, V_d, as a function of the annealing time of α‐Si:H films. All these parameters were carried out through the current voltage characteristics (J‐V) and the capacitance voltage measurements (C‐V). The results were presented a discussed on the basis of XRD performance and the thermionic emission theory.     

PECVDSi3N4/InP界面特性的研究

本文利用Auger分析技术和C-V测量方法,详细地研究了PECVDSi₃N₄/InP界面特性,Auger能谱分析表明热处理使界面面发生互扩散,同时InP的热分解导致P元素穿过Si₃N₄薄膜到达表面。C-V测量表明Ag/Si₃N₄/InPMIS结构可以实现载流子的堆积、耗尽和反型。     

Plasma reaction of group VI metal carbonyls

The hexacarbonyl compounds of Cr, Mo, and W have been used as precursors in plasma-enhanced chemical vapor depositions (PECVD). They form films of good adherence on glass, ceramics, and a variety of polymers. The nature of the deposits depends very much on the composition of the gas, which forms the plasma. When pure argon is used, the resulting films contain considerable amounts of oxygen and carbon. Films deposited in hydrogen/argon mixtures consist of the metal and/or the carbide. With Ar/O₂ mixtures, Mo(CO)₆ and W(CO)₆ are converted into films of MoO₃ and WO₃, respectively. When H₂S/H₂ mixtures are used as plasma gas, Mo(CO)₆ yields films consisting of MoS_x.     

PECVD在多晶硅上沉积氮化硅膜的研究

氮化硅薄膜作为一种新型的太阳电池减反射膜已被工业界认识和应用.应用PECVD(等离子体增强化学气相沉积)系统, 以硅烷、氨气和氮气为气源在多晶硅片上制备了具有减反射作用的氮化硅薄膜.并研究了在沉积过程中, 衬底温度、硅烷与氨气的流比以及射频功率对薄膜质量的影响.     

PECVD技术制备多波段渐变减反膜

介绍了利用傅里叶变化法设计多波段渐变减反膜的原理和方法,研究了采用该方法设计多波段减反膜时Q函数的优选流程,给出了最优Q函数。设计优化得到了在350~5000nm波段范围平均透过率大于90%的多层渐变减反膜系结构,并采用等离子体增强化学气相沉积(PECVD)技术完成了样片的制备。实验结果表明,镀制的样片在350~5000nm波段范围的平均透过率为90.55%,满足光谱特性的要求。     

Raman characterization of the structural evolution in amorphous and partially nanocrystalline hydrogenated silicon thin films prepared by PECVD

Hydrogenated silicon (Si:H) thin films were obtained by plasma‐enhanced chemical vapor deposition (PECVD). Raman spectroscopy was used to investigate the structural evolution in phosphor‐doped n‐type amorphous hydrogenated silicon thin films, which were prepared under different substrate temperatures and gas pressures. Meanwhile, the effect of nitrogen doping on the structure of P‐doped thin films was also investigated by Raman spectroscopy. Moreover, the transition from the amorphous state to the nanocrystalline state of undoped Si:H films deposited through low argon dilution was studied by Raman spectroscopy, X‐ray diffraction, and transmission electron microscopy. The results show that Raman spectroscopy can sensitively detect the structural evolution in hydrogenated silicon thin films deposited under different conditions in a PECVD system. Copyright © 2010 John Wiley & Sons, Ltd.     

Plasma‐enhanced chemical vapor deposition of 99.95% 28Si in form of nano‐ and polycrystals using silicon tetrafluoride precursor

The process of plasma chemical deposition of silicon was investigated from its tetrafluoride containing 99.99% of ²⁸Si isotope in the form of thin layer of nano‐crystalline silicon on silicon substrate and of thick layer of polycrystalline silicon on the inner surface of quartz reactor. The layers are characterized by the methods of X‐ray diffraction and Raman spectroscopy. Using the SIMS method the mechanism of isotopic dilution was investigated in the PECVD process (the content of ²⁸Si isotope in layers was 99.95‐99.98%). A necessity is indicated in thorough special preparation of the reactor for minimization of isotopic dilution in case of fabrication of silicon containing ≥99.9% of ²⁸Si. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

氮化硅薄膜中硅纳米颗粒的形成机制研究

采用等离子体增强化学气相沉积技术,以SiH₄作为硅源, NH₃和N₂共同作为氮源,在单晶硅衬底上制备了不同的氮化硅薄膜. X射线衍射分析薄膜晶体结构,通过计算晶格尺寸大小证明了纳米硅颗粒的存在. 傅里叶变换红外光谱分析了薄膜中的键合作用的变化并结合化学反应过程对氮化硅薄膜中纳米硅颗粒的形成机制进行了研究,发现Si—Si键作为硅纳米颗粒的初始位置, 当反应朝着生成Si—Si的方向进行时,可以促进氮化硅薄膜中硅纳米颗粒的形成. X射线衍射分析和光致发光实验结果表明Si—Si键浓度增大时, 所形成的纳米硅颗粒的尺寸和浓度都随之增大.     

Experimental design and modelling in the investigation of PECVD parameters effects on the structural and gas transport properties of plasma polysiloxane membranes

The experimental design method was used to investigate the PECVD parameters effects on the properties of plasma polysiloxane membranes synthesized using octamethylcyclotetrasiloxane or hexamethyldisiloxane as monomers. On a wide experimental range and with a minimum number of experiments, the use of such a statistical tool enabled us to set up complete and reliable correlations, in the form of polynomial models connecting the gas transport properties (H₂ permeability coefficient, H₂/N₂ ideal selectivity) and the structural properties (growth rate, density, organic/inorganic nature) of synthesized films with the two most influent synthesis parameters of the PECVD process: the input power (represented by the input voltage) and the monomer flux. The polynomial models enabled us not only to statistically confirm the effects of the PECVD parameters displayed by previous classical experimental studies, but also to model, in the mathematical sense, the evolution of each property of materials taking into account the first and second orders effects of both PECVD synthesis parameters. By the use of a performing statistical tool, we managed to improve the knowledge of relations between synthesis parameters/structure/properties relative to our process.