三氯氢硅和氢气系统的气相沉积三维模拟

建立了氢气和三氯氢硅系统的多晶硅气相沉积反应模型,通过Chemkin4.0耦合气相反应、表面反应机理,利用流体力学软件Fluent 6.3.26数值求解.根据模拟结果绘制了进气温度、进气组成、沉积表面温度以及反应压力与硅沉积速率的关系曲线,阐述了这些条件对于硅沉积速率的影响,同时把模拟结果与文献中的实验数据和计算结果进行对比.结果表明,硅沉积速率随反应温度和反应压力的提高而提高,随进气温度的提高而提高,当氢气摩尔组成低于0.8时,与氢气物质的量组成成正比,氢气物质的量组成大于0.8时,与氢气摩尔组成成反比.     

硅烷热分解生产多晶硅的三维模拟

本文建立了硅烷和氢气体系中气体动量、热量和质量同时传递,并且耦合硅烷热分解反应的多晶硅气相沉积模型,选择适宜的物理模型和边界条件通过流体力学软件Fluent 6.3.26进行数值模拟.之后模拟了进气组成、反应温度、反应压力及进口速度等因素对沉积特性的影响,得到结论:当进气组成、反应温度和反应压力增大时,硅的沉积速率增大、单位能耗降低;当进气速度增大时,硅的沉积速率和单位能耗均呈增大趋势;在进口区域硅沉积速率随着硅棒延伸增大,在离进口较远的区域,硅沉积速率随着硅棒延伸而减小.     

钟罩式硅烷反应器内流动与传热的数值模拟

针对硅烷热分解生产多晶硅的过程,建立了基于动量、质量、能量同时传递并耦合硅烷热分解反应的硅烷-氢气化学气相沉积模型,采用计算流体力学方法分析了传统钟罩式硅烷反应器内的流场、温度场和浓度场.针对普通反应器内存在的死区以及沉积速率不均匀的问题,提出了新型的带出气筒的反应器结构,并对结构进行了数值模拟.计算结果表明,与普通钟罩式硅烷反应器相比,新型反应器的流场、温度场以及硅烷浓度分布更加合理,有效减小了反应器内的漩涡,缓解了气体在进出口间的“短路”现象,使硅棒表面的沉积速率更加均匀.     

多晶硅化学气相沉积反应的三维数值模拟

建立了多晶硅化学气相沉积反应的三维模型,同时考虑质量、能量和动量传递,利用CFD软件对炉内的流动、传热和化学反应过程进行了数值模拟,并分析了硅沉积速率、SiHC13转化率、硅产率以及单位能耗随H2摩尔分数的变化规律.结果表明:计算结果与文献数据吻合较好;随着硅棒高度的增加,硅沉积速率不断增大;最佳的进气H2摩尔分数范围为0.8 ～0.85.     

氢气浓度对掺氮超纳米金刚石薄膜的影响

采用微波等离子体化学气相沉积法,以甲烷和氮气为气源,通过改变反应气体中氢气的浓度,在硅衬底上沉积出掺杂氮的超纳米金刚石膜.并利用扫描电子显微镜,拉曼光谱仪,X射线衍射仪,霍尔效应测试仪分别对掺杂氮的超纳米金刚石膜的表面形貌,组成结构及导电性能进行了进行表征,重点研究了氢气浓度对薄膜特性的影响.结果表明:随着氢气浓度的增加,薄膜的晶粒尺寸逐渐增大;薄膜的质量提高,且由G峰漂移引起的压应力逐渐减小;薄膜导电性变差.     

衬底温度对nc-Si∶H薄膜微结构和氢键合特征的影响

采用射频等离子体增强型化学气相沉积(RF-PECVD)技术,以H2和SiH4作为反应气体源,在不同的衬底温度下沉积了nc-Si∶H薄膜.采用Raman散射、X射线衍射、红外吸收等技术分析了薄膜的微结构和氢键合特征.结果表明,随衬底温度的升高,nc-Si∶H薄膜的沉积速率不断增大,晶化率和晶粒尺寸增加,纳米硅颗粒呈现出Si(111)晶面的择优生长趋势.键合特性显示,薄膜中的氢含量随衬底温度升高而逐渐减小,薄膜均匀性先增大后减小.     

蒙特卡罗模拟金刚石薄膜化学气相沉积过程中甲烷浓度的影响

本工作采用蒙特卡罗模拟,研究了以CH4/H2气体混合物作为源料气体的电子辅助热丝化学气相沉积中甲烷浓度对气相沉积过程的影响.计算了典型实验条件下电子能量分布,研究了电子平均能量、碎片H及CH3数目的空间分布、H与CH3的比值及CH3携带的能量随甲烷浓度的变化.结果表明:当电子能量为2-3eV时,电子的数密度达到一峰值;平均电子能量随着甲烷浓度的增加而增加;电子与气体分子碰撞产生的碎片H、CH3和CH2的数密度随距热丝的距离而变化;随着甲烷浓度的增加,原子氢H的数目缓慢下降,然而,官能团CH3和CH2的数目缓慢上升;H与CH3的数量比随甲烷浓度的增加而减少;碎片CH3携带的能量处于1～5eV范围之内,且当甲烷浓度为1.3;时,该能量达到一最值.     

流态化多晶硅化学气相沉积过程的数值模拟

利用基于欧拉-欧拉两相流模型,建立硅烷热分解的均相和非均相反应模型,模拟了二维流态化的多晶硅化学气相沉积过程,以及硅烷、硅烯和硅沉积速率在反应器中的分布规律.模拟结果表明多晶硅的沉积主要发生在流化床中的密相区及气泡的周围,浓度相对较小的硅烯非均相反应对多晶硅沉积的贡献约为硅烷的10;.分析了硅烷入口浓度和反应温度对硅沉积速率及转化率的影响,模拟的硅沉积速率与文献中的实验数据做了比较.     

多晶硅化学气相沉积过程气相与表面反应模拟验证

针对SiHCl3-H2体系下硅的化学气相沉积过程,采用边界层反应模型和Chemkin模拟软件,耦合不同气相与表面化学反应机理,对不同条件下硅的沉积速率,高温下HCl气体对硅表面的侵蚀速率进行了模拟计算.与文献报道的三组实验数据进行对比,验证现有反应机理的模拟精度,确定一套修正化学反应机理可以较为准确地预测工业级西门子多晶硅还原炉条件下多晶硅的沉积速率.     

优化沉积参数对微晶硅薄膜太阳电池性能的影响

本文主要采用甚高频等离子体增强化学气相沉积技术制备了不同硅烷浓度、辉光功率和反应气体流量的单结微晶硅薄膜太阳电池。电池的I-V测试结果表明:电池的开路电压随功率的降低、硅烷浓度和气体流量的增加而增加,而对应的短路电流密度在一定的硅烷浓度条件下达到最大,填充因子也在逐渐的增加。文中对具体内容进行了详细的分析。     

Polycrystalline silicon carbide film deposition using monomethylsilane and hydrogen chloride gases

A polycrystalline silicon carbide film is formed on a silicon surface by chemical vapor deposition using monomethylsilane gas along with hydrogen chloride gas in ambient hydrogen at atmospheric pressure. The film deposition is performed near 1000 K, at which temperature the monomethylsilane maintains a chemical bond between the silicon and carbon present in the molecular structure. The excess amount of silicon on the film surface is reduced using the hydrogen chloride gas. Although the film deposition stops within 1 min after beginning the supply of the monomethylsilane gas and hydrogen chloride gas, annealing at 1273 K in ambient hydrogen after the film deposition allows further deposition so that a thick silicon carbide film can be obtained.     

High-density silicon and silicon nitride cones

High-density cone-shaped silicon and silicon nitride have been synthesized on Si(1 0 0) substrates via plasma-assisted hot-filament chemical vapor deposition using a gas mixture of nitrogen, hydrogen and methane. Aligned silicon cones containing 3–10 at% C and N have been formed with less than 1 h growth. Further growth can lead to the increase of cone size and density, as well as to the formation of polycrystalline silicon nitride films on the tip and surface. The formation of these materials is thought to be due to the remodification of Si substrates under the effect of plasma and active C and N species. Different nucleation and growth styles were obtained under different growth conditions and reactive gas mixtures.     

多晶硅的反应离子刻蚀(R IE)制绒绒面研究

实验基于反应离子刻蚀(Reaction Ion Eatching RIE)技术进行的多晶硅片纳米绒面制备,这种结构的绒面可明显降低晶体硅电池反射率,提高电池短路电流.实验具体指将多晶硅片在同一条件混酸溶液中腐蚀去除表面损伤,然后利用RIE制绒技术进行不同尺寸纳米绒面制备,根据绒面变化分别调整工艺进行清洗及电池制备,发现绒面小到一定程度时RIE制绒过程造成的损伤不易清洗去除且抗反射SiNx膜沉积困难.所以多晶硅片RIE制绒不可单纯的追求小绒面和低反射率,实验证明纳米绒面凹坑尺寸最小应控制在240~360 nm才能更稳定地匹配清洗、沉积抗反射膜等工艺从而制备出高光电转换效率的多晶硅电池.     

以高性价比颗粒硅带为衬底多晶硅薄膜的二次引铝低温制备法

本文报道了在廉价的颗粒硅带上用PECVD法并两次引入铝的工艺制备多晶硅薄膜.第一次引入铝是为了去除薄膜上过多的杂质;第二次引入铝是为了实现低温诱导结晶.通过对薄膜样品的拉曼谱和X射线衍射(XRD)谱分析,我们认为金属低温诱导结晶成功与否跟诱导前薄膜的结构密切相关.采用该工艺成功地制备了结晶度92;左右、可应用于太阳能电池的高纯优质多晶硅薄膜.     

Crystal structure of the growth surface of silicon carbide obtained by sublimation

Structural study of polycrystalline silicon carbide obtained by sublimation performed via X-ray luminescence and X-ray diffraction analysis. It is shown that chemical vapor deposition of silicon carbide results in the formation of grains with the (00.1), (01.1), and (12.3) crystallographic planes parallel to the growth surface. The grains with the (00.1) growth planes are characterized by perfect structure and by red luminescence. Domains with yellow luminescence have a mosaic structure with the (01.1) and (12.3) growth planes.     

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)     

Synthesis of polycrystalline silicon thin films with ‘icosahedral’ symmetry by ceramics hot wire chemical vapor deposition

We report on synthesis and materials physics of polycrystalline silicon thin films deposited on glass with rarely observed ‘five-fold’ symmetry or ‘icosahedral’ symmetry. We invented these ‘novel form’ of polycrystalline silicon thin films by ceramics hot wire chemical vapor deposition (hot-wire CVD). A new physical effect in hot-wire CVD technology has been proposed that controls the nucleation and growth of silicon thin films on glass substrate.     

Deposition Efficiency Reducing Reactions in Silicon Deposition from Silane at Low Pressure

Silane pyrolysis at polysilicon low-pressure-deposition conditions is analyzed along the reactor-tube axis with respect to the existence of competing decomposition reactions leading to the formation of silicon-containing gaseous byproducts. The presence of such a parallel reaction is indicated by a difference between silane decomposition efficiency η_SiH4 and silicon deposition efficiency η_si. The rate of such a competing parallel reaction is influenced by the variation of deposition temperature and/or substrate area of silicon deposition. It is drastically accellerated by the presence of phosphine in the gas phase. For the latter case the competing parallel reaction is shown to occur as a homogeneous reaction.