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.     

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.     

三氯氢硅和氢气系统中多晶硅化学气相沉积的数值模拟

本文建立了三氯氢硅和氢气系统中混合气体动量、热量和质量同时传递,并且耦合气相反应、表面反应的多晶硅气相沉积模型,利用流体力学计算软件(Computational Fluid Mechanics, CFD)Fluent6.2数值分析了气体进口速率、反应压力、表面温度和气体组成对硅化学气相沉积特性的影响,数值结果表明计算结果与相关实验数据吻合较好.分析表明在一定的条件下,硅沉积速率随温度、压力的升高而增加,在氢气浓度较高的情况下,硅沉积速率随氢气浓度增加而线性地降低.     

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.     

硅烷热解多晶硅气相沉积反应模型分析与验证

在综述现有硅烷热解反应机理的基础上,针对Ho等人提出的气相和表面反应机理,采用二维边界层反应模型和CHEMKIN软件,对水平单基片CVD反应器进行模拟分析,计算结果与文献报道的实验数据拟合良好;通过改变硅烷进气浓度和进气温度,分析沉积速率的变化和各表面反应的贡献率,得到硅微粉再沉积过程随浓度和温度的变化规律;使用上述机理模型,计算了硅烷流化床对应的操作温度和硅烷浓度条件下的沉积速率,与文献报道测量结果比较,误差在合理范围,表明该机理适用于硅烷流化床化学气相沉积过程的CFD耦合模拟.     

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.     

PECVD法制备不同衬底微晶硅薄膜的研究

采用等离子体增强化学气相沉积(PECVD)法分别在玻璃衬底和p型薄膜硅衬底上制备了微晶硅薄膜。使用拉曼谱仪、紫外-可见分光光度计、傅里叶红外光谱仪等对微晶硅薄膜进行检测,重点研究了硅烷浓度、衬底温度对薄膜沉积速率和晶化率的影响。实验结果表明:两种衬底上薄膜的沉积速率均随硅烷浓度的增大、衬底温度的升高而变大。硅烷浓度对两种衬底的薄膜晶化率影响规律相同,即均随其升高而降低;但两种衬底的衬底温度影响规律存在差别:对玻璃衬底而言,温度升高,样品晶化率减小;而p型薄膜硅衬底则在温度升高时,样品晶化率先增大后减小。此外还发现,晶化率与薄膜光学性能及含氧量存在较密切关联。     

脉冲激光沉积碳薄膜生长中氢气的作用

采用石墨靶,通过脉冲激光沉积技术在温度为20℃的玻璃和硅衬底上沉积出厚度为100nm的碳薄膜,所用的激光源是ArF激光(λ＝193nm, 24ns). 通过调节氢气流量使反应室的压力在1.33×10-5～133Pa之间变化. 拉曼光谱测量显示有一1550cm-1为中心的宽峰, 这与用其他方法制备的典型类金刚石碳(DLC)膜相类似, 随着增大氢气压力,膜的吸收系数减小, 而光带隙增大. 在氢气压力为133Pa下沉积的薄膜具有大于2.5eV的光带隙, 比无氢气气氛下沉积的薄膜的光带隙大1倍. 结果表明, 氢气对蚀刻sp2键是有效的. 在PLD法中, 从靶中喷射的等离子体物质和氢分子预先被离解成原子氢, 与CVD法的情况相同,这些原子氢必定起到蚀刻sp2键的作用.     

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.     

工艺参数对CVD ZnS沉积速率的影响

本文报道了CVD法制备ZnS晶体的制备工艺,系统地研究了气体流量、工作气压、基板温度等主要工艺参数对沉积速率的影响规律.实验表明,随着H2S(s)/Zn摩尔流量比的增加,沉积速率逐渐增大;基板温度升高,沉积速率加快;工作气压增大,沉积速率变化不大.在本实验研究的条件下认为,采用合适的H2S(s)/Zn摩尔流量比和沉积温度,在较低的工作气压下生长晶体,能保证较稳定的沉积速率,生长出高质量的晶体.     

On Chemical Kinetics of Silicon Deposition from Silane (V) The Effect of Hydrogen Formation

In consequence of hydrogen formation during silane pyrolysis total gas volume increases, when the reaction proceeds at constant total pressure. Any mole of silane decomposed produces two moles of hydrogen. In the present paper expressions are derived for 1^st and 0.5^th reaction order describing axial growth rate distribution of the isothermally proceeding reaction for the condition of constant total pressure. Those theoretically expected distributions are compared with results obtained by way of experiment on the one hand and those theoretically expected for the condition of constant gas volume on the other. It is concluded that the experimental results discussed rather agree with constant gas volume than with constant total pressure conditions. So, a compensating increase of total pressure along the tube axis might be supposed.     

Thermodynamic analysis for silicon contamination of VPE GaAs

A thermodynamic analysis for silicon contamination in VPE GaAs is described. The analysis is carried out for the inert gas-hydrogen mixed carrier system. It is shown that silicon contamination is related, among other things, to the temperature difference between the source and the substrate and the hydrogen mole fraction in the carrier gas. An explanation is given for the impurity decrease in the single flat temperature zone (SFT) method.     

喷淋式MOCVD反应器中AlN的生长速率和化学反应路径的数值模拟研究

利用数值模拟方法,结合反应动力学和气体输运过程,研究喷淋式MOCVD反应器中AlN的生长速率和气相反应路径与反应前体流量(NH3和H2)、进口温度、压强、腔室高度等参数的关系.研究发现:薄膜生长前体和纳米粒子前体的浓度决定了不同的生长速率和气相反应路径.在低Ⅴ/Ⅲ比(2000)、高H2流量(12 L/min)、高进口温...     

The effects of argon gas flow rate and furnace pressure on oxygen concentration in Czochralski silicon single crystals grown in a transverse magnetic field

The effects of the argon gas flow rate and furnace pressure on the oxygen concentration in a transverse magnetic field applied Czochralski (TMCZ) silicon single crystals were examined through experimental crystal growth. A gas controller which had been proposed by Zulehner was used for this series of experiments. In the TMCZ gas-controlled crystals, a decrease in the oxygen concentration with a decrease in furnace pressure was found. A clear relationship between the oxygen concentration and the argon gas flow rate was not obtained due to the limited experimental conditions. The relationships between the oxygen concentration and the furnace pressure and the argon gas flow rate previously observed for Czochralski (CZ) crystals by a similar gas controller were confirmed by the present gas controller. The oxygen concentration changes in the TMCZ and the CZ crystals were analyzed in terms of the calculated flow velocity of the argon gas between the gas controller and the silicon melt surface. In contrast with the CZ gas-controlled crystals, the oxygen concentration was decreased with an increase in the flow velocity of argon gas in the TMCZ gas-controlled crystals. The surface temperature model and the melt flow pattern model which had been proposed in the previous report are discussed again in light of the present experimental results.     

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.     

On chemical kinetics of silicon deposition from silane (III). LPCVD poly silicon formation in the temperature range 900–950 K

LPCVD poly Silicon deposition form silane has been investigated for limited conditions regarding temperature, silane input and pumping speed. It has been found that layer growth is controlled by a chemical reaction of 0.5^th-order in consequence of which growth rate linearly decays along the axis of an open isothermal reactor tube. The slope of that decay is determined not only by the reaction rate constant but also by linear gas velocity within the tube and that part of total substrate surface area that is effectively exposed to silane at each wafer position. In conseqence growth rate decay is the steeper not only the higher temperature will be chosen but also the slower gas velocity is adjusted and the smaller wafers are separated to each other. The kind of how axial layer growth rate distribution is effected by changing wafer spacing is a proof for the heterogeneous reaction mechanism. The silicon forming reaction is characterised by an activation energy of about 52 kcal/mole.     

Computational modeling of SiC epitaxial growth in a hot wall reactor

A computational model for chemical vapor deposition (CVD) of silicon carbide (SiC) in a hot-wall reactor is developed, where the susceptor is tapered with a rectangular cross-section. The present work focuses on the advection–diffusion-reaction process in the susceptor. The precursors are propane and silane, and the carrier gas is hydrogen with mass fraction higher than 99%. Computed growth rates under different system pressures and precursor concentrations are compared to the experimental data measured on samples grown in the Linköping CVD reactor. The gas composition distribution in the susceptor and the growth rate profile on the susceptor floor are shown and analyzed. Dependence of the growth rate on precursor concentrations is investigated. It is demonstrated that the growth rate of SiC may either be carbon transport limited or silicon controlled, depending on the input carbon-to-silicon ratio.     

Analytical model for chemical vapor deposition of SiO2 films using tetraethoxysilane and ozone

A theoretical model has been developed to analyze chemical vapor deposition (CVD) of SiO₂ from tetraethoxysilane (TEOS) and ozone. The model incorporates both homogeneous gas phase reactions and heterogeneous surface reactions. Two new kinetic mechanisms which include parasitic gas phase reactions are proposed to explain the observed decrease in deposition rate of SiO₂ films as the temperature is increased. The predicted values from the proposed model are found to agree well with all available experimental results over a wide range of experimental conditions. The effect of parasitic gas phase reactions becomes significantly more pronounced with increasing pressure and temperature. Correlations of experimental data on etch rate with surface concentrations predicted by the model at 60 Torr show that one can improve the film quality by increasing the ratio of O₃ to TEOS at the wafer surface, (O₃/TEOS)_wafer, and the wafer temperature.     

Study of the chemical reactions' influence on semiconductor films structure formation by the Monte-Carlo method

The investigation by the Monte-Carlo method of the growth of the silicon epitaxial film at a chloride CVD system has allowed to find out the composition of adsorption layer, the micromechanism of the reactions of Si atoms building-in into the growing crystalline layer and the growth conditions influence on the growth rate and film surface roughness. The change of adsorptive layer composition in the system SiCl₄—HCl—H₂ (fraction of adaatoms, silicon atoms built-in a crystal and molecules SiCl₂) depending on temperature has been determined. The change of silicon film growth rate depending on temperature and concentration change of SiH₂Cl₂ has been established and the contribution of growth mechanism (with participation of adatom, silicon atoms and molecules SiCl₂) into the total rate of film growth has been shown.