低能Cl原子刻蚀Si(100)表面的分子动力学模拟

使用分子动力学模拟方法研究了不同能量(0.3—10 eV)的Cl原子对表面温度为300 K的Si(100)表面的刻蚀过程.模拟中采用了Tersoff-Brenner势能函数来描述Cl-Si体系的相互作用.模拟结果显示,随着入射Cl原子在表面的吸附达到饱和,Si表面形成一层富Cl反应层.这和实验结果是一致的.反应层厚度随入射能量增加而增加.反应层中主要化合物类型为SiCl,且主要分布于反应层底部.模拟结果发现随初始入射能量的增加,Si的刻蚀率增大.在入射能量为0.3,1和5 eV时,主要的Si刻蚀产物为Si 关键词： 分子动力学 Cl刻蚀Si 分子动力学模拟 微电子机械系统     

分子动力学模拟H原子与Si的表面相互作用

通过分子动力学模拟了入射能量对H原子与晶Si表面相互作用的影响. 通过模拟数据与实验数据的比较, 得到H原子吸附率随入射量的增加 呈先增加后趋于平衡的趋势. 沉积的H原子在Si表面形成一层氢化非晶硅薄膜, 刻蚀产物(H₂, SiH₂, SiH₃和SiH₄)对H原子吸附率趋于平衡有重要影响, 并且也决定了样品的表面粗糙度. 当入射能量为1 eV时, 样品表面粗糙度最小. 随着入射能量的增加, 氢化非晶硅薄膜中各成分(SiH, SiH₂, SiH₃)的量以及分布均有所变化. 关键词： 分子动力学 吸附率 表面粗糙度 氢化非晶硅薄膜     

低能原子沉积在Pt(111)表面的分子动力学模拟

采用嵌入原子方法的原子间相互作用势,利用分子动力学方法模拟了六种贵金属原子(Ni,Pd,Pt,Cu,Ag,Au)分别在Pt(111)表面低能沉积的动力学过程.结果表明:随着入射能量从0.1eV升高到200eV,基体表面原子是按层迁移的,沉积过程对基体表面的影响和沉积原子在基体表层的作用均存在两个转变能量(ET1≈5eV,ET2≈70eV).当入射能量低于5eV时,基体表面几乎没有吸附原子和空位形成,沉积原子在基体表层几乎没有注入产生;当入射能量在5—70eV范围内时,沉积原子在基体表层有注入产生,其注入深度小于两个原子层,即为亚注入,此时吸附原子主要由基体表层原子形成,基体表面第三层以下没有空位形成;当入射能量高于70eV时,沉积原子的注入深度大于两个原子层,将会导致表面以下第三层形成空位,并且空位产额随入射能量的升高而急剧增加.基于分子动力学模拟的结果,对低能沉积作用下的薄膜生长以及最优沉积参数的选择进行了讨论.     

C2团簇在金刚石(111)表面吸附结构的分子动力学模拟

利用Brenner(#2)半经验多体相互作用势和分子动力学模拟方法研究荷能的C₂在金刚石(111)表面的化学吸附过程.模拟300 K时,初始入射动能分别为1,20,30 eV的C₂团簇从6个不同位置轰击金刚石(111)表面,观察到C₂团簇在金刚石(111)表面形成的吸附结构,表面C原子键的打开以及C₂团簇与表面C原子成键等物理过程,并讨论不同入射位置和入射能量对沉积团簇的结构特性的影响.结果表明,对于表面不同的局部构型,C₂团簇发生不同的碰撞过程,C₂团簇入射能量的提高有利于成键过程的发生,从原子尺度模拟沉积机制.     

入射能量对Au/Au(111)薄膜生长影响的分子动力学模拟

利用分子动力学模拟了Au原子在Au(111)表面低能沉积的动力学过程.采用嵌入原子方法的原子间相互作用势,通过对沉积层原子结构的分析和薄膜表面粗糙度、层覆盖率的计算,研究了沉积粒子能量对薄膜质量的影响及其机制.结果表明:当入射能量Ein25 eV时,沉积层和基体表层均呈现规则的单晶面心立方(111)表面的排列,沉积原子仅注入到基体最表面两层,随着入射能量的增加,薄膜表面粗糙度降低,薄膜越趋于层状生长,入射能量的增加有利于薄膜的成核和致密化;当Ein 25 eV时,沉积层表面原子结构出现了较为明显的晶界,沉积原子注入到基体表面第三层及以下,随着入射能量的增加,薄膜表面粗糙度增加,沉积层和基体表层原子排列越不规则,载能沉积会降低基体内部的稳定性,导致基体和薄膜内部缺陷的产生,降低薄膜质量.此外,当基体内部某层沉积原子数约等于该层总原子数的一半时,沉积原子将能穿过该层进入到基体内部更深层.     

低能Cu原子簇沉积薄膜的分子动力学模拟

用分子动力学计算机模拟研究了能量为5—20eV/atorn,结构为正二十面体的(Cu)₁₃原子簇在Cu（001）表面的沉积过程.采用紧束缚势同Moliers势的结合描述Cu原子间相互作用通过原子簇-衬底相互作用的“快照”研究沉积的动态过程．结果表明,当入射能量较低时,轰击弛豫后,入射原子簇在衬底表面发生重构,生成很好的外延层,靶没有任何损伤．随着轰击能量的增加,原子簇原子穿入靶的深度增加.当入射能量达到20eV/atom时,原子簇完全穿入靶并开始造成辐照损伤,表面出现空位,靶内产生间     

入射能量对H2+与SiC表面相互作用影响的分子动力学模拟

用分子动力学方法研究了入射能量对 H2+与 SiC 样品表面相互作用的影响.模拟结果表明,在 H2+轰击 SiC 样品表面的初始阶段,样品中 H 原子的滞留量增加较快,其后,增加的速率减慢,并逐渐趋于饱和.入射能量越大,样品中 H 原子的滞留量也就越大.样品在 H2+的轰击下,样品 Si、C 原子会发生刻蚀.入射能量越...     

F等离子体刻蚀Si中Lag效应的分子动力学模拟

通过分子动力学模拟的方法对感应耦合等离子体刻蚀中Lag效应的产生机理进行了研究. 研究结果表明,在刻蚀过程中普遍存在Lag效应,宽槽的刻蚀率明显比窄槽的刻蚀率要高,这是由于宽槽更有利于产物从槽中的逸出;窄槽中产物从槽中逸出的速率较低,较多的产物拥挤在窄槽中降低了入射的F等离子体入射的速度,从而降低了F等离子体到达Si表面的能量,而相同条件下,刻蚀率随能量的降低而降低;另一方面,窄槽中入射的等离子体与槽壁的距离较近,使得入射的F更容易与槽壁表面的Si的悬挂键结合沉积在槽壁表面,使刻蚀出的槽宽度变窄,进一步影响到后继粒子的入射;Lag 效应随槽宽的减小而增强,随温度的升高而减弱,随入射粒子能量的升高而增强. 关键词： 分子动力学 Lag效应 刻蚀 刻蚀率     

Pt(111)表面低能溅射现象的分子动力学模拟

利用嵌入原子方法的原子间相互作用势，通过分子动力学模拟，详细研究了贵金属原子在Pt (111)表面的低能溅射现象.模拟结果显示：对于垂直入射情况，入射原子的质量对Pt (11 1)表面的溅射阈值影响不大.当入射原子的能量小于溅射阈值时，入射原子基本以沉积为主 ；当入射原子的能量大于溅射阈值时，溅射产额随入射原子能量的增加而线性增大；当入射 原子能量达到200 eV时，各种入射原子的溅射产额都达到或接近1，此时入射原子主要起溅 射作用.溅射原子发射的角分布概率和溅射花样与高能溅射相类似.研究表明：与基于二体碰 撞近似的线性级联溅射理论不同，当入射原子能量大于溅射阈值时，低能入射原子的溅射产 额正比于入射原子的约化能量和入射原子与基体原子的质量比.通过对低能入射原子的钉扎 能力分析，提出了支配低能溅射的入射原子反射物理机理. 关键词： 分子动力学模拟、低能溅射     

Al(001)表面上沉积Ti薄膜的分子动力学模拟

采用分子动力学模拟方法,研究了Ti原子连续沉积于Al(001)表面上的薄膜生长过程,分析了入射能量为0.1、5 eV和衬底温度为300、700 K时的界面结合及微观结构.模拟结果表明,增加入射能量和衬底温度,使Ti薄膜的表面越光滑;通过径向分布函数和键对分析技术对薄膜微观结构进行分析,发现衬底温度时薄膜微观结构影响较大,温度300 K及以下时,Ti薄膜主要是FCC结构,随着温度升高,FCC结构成分减少,无序结构成分增加,而入射能量则对薄膜微观结构没有明显影响.     

Etching of SiC by energetic F2: Molecular dynamics simulation

Molecular dynamics (MD) simulations were performed to investigate F₂ continuously bombarding silicon carbide (SiC) surfaces with energies in the range of 50-200 eV at normal incidence and room temperature. The Tersoff-Brenner form potential was used. The simulation results show that the uptake of F atoms, the etch yields of C and Si from the initial substrate, and the surface structure profile are sensitive to the incident energy. Like occurrence in Si etching, steady-state etching is observed and an F-containing reaction layer is formed through which Si and C atoms are removed. A carbon-rich surface layer after bombarding by F₂ is observed which is in good agreement with experiments. In the reaction layer, SiF in SiF₂ species are dominant; with increasing incident energy, the total fraction of SiF and SiF₂ increases, while the amount of SiF₃ and SiF₄ decreases. Finally, etching mechanisms are discussed.     

Molecular dynamics study of particle emission by reactive cluster ion impact

Molecular dynamics (MD) simulations of sputtering process with fluorine cluster impact onto silicon targets were performed. By iterating collisional simulations on a same target, accumulation of incident atoms and evolution of surface morphology were examined as well as emission process of precursors. When (F₂)₃₀₀ clusters were sequentially irradiated on Si(1 0 0) target at 6 keV of total incident energy, column-like surface structure covered with F atoms was formed. As the number of incident clusters increased, sputtering yield of Si atoms also increased because the target surface was well fluoridised to provide SiF_x precursors. Size distribution of emitted particles showed that SiF₂ was the major sputtered particle, but various types of silicon-fluoride compounds such like Si₂F_x, Si₃F_x and very large molecules consists of 100 atoms were also observed. This size distribution and kinetic energy distribution of desorbed materials were studied, which showed that the sputtering mechanism with reactive cluster ions is similar to that under thermal equilibrium condition at high-temperature.     

Molecular dynamics simulation of deposition and etching of Si bombarding by energetic SiF

In this study, SiF interaction with amorphous Si surface at normal incidence was investigated using molecular dynamics simulation at 300 and 600 K. The incident energies of 50, 100 and 200 eV were used. The results show that the deposition rate is not sensitive to the incident energy, while with increasing the surface temperature, the deposition rate decreases. The etch yield is sensitive to the incident energy and the surface temperature. The etch yield increases with increasing incident energy and temperature. After bombarding, a Si_xF_y interfacial layer is formed. The interfacial layer thickness increases with increasing incident energy mainly through enhanced penetration of the silicon lattice. In the interfacial layer, for SiF_x (x = 1-3) species, SiF is dominant and only little SiF₃ is present. At the outmost and innermost of the interfacial layer, SiF species is dominant. Most of SiF₃ species is concentrated above the initial surface.     

样品温度对CF3+ 与Si表面相互作用影响的分子动力学模拟

利用分子动力学模拟方法研究了不同温度下CF_x层对CF⁺₃刻蚀Si表面过程的影响.由模拟数据可知,温度对C和F的沉积有显著的影响,通过提高样品的温度,物理刻蚀得到了加强,而化学刻蚀被减弱.同时,随着温度的升高,Si的刻蚀率相应增加.刻蚀产物中的SiF,SiF₂的量随温度的增加而增加,SiF₃的量与基体温度没有直接的关系.Si刻蚀率的增加主要是通过提高SiF,SiF_{2相似文献}   

First principles study of Si etching by CHF3 plasma source

A model of CF₃ etching Si (2 × 4) surface has been developed based on density functional theory. We find that the reconstruction Si surface tends to be fully F-terminated. Meanwhile, C-C chain forms spontaneously on the top of the surface to resist further F-Si interacting. Over-saturated Si bonds could still be stable as well due to the strong F-Si bonding, however, it needs to overcome an energy barrier of 1.85 eV to achieve this doubly saturated bonding. Two reaction paths are found to investigate chemical reaction of CF₃ with the full F-terminated Si surface. The first path displays that all fully saturated F-Si bonds could be over-saturated and thus produce F-Si-F bonds with an energy barrier of ∼1.85 eV. For this path, there is no product of SiF₄; the second path indicates a formation of SiF₄ with a much lower surface energy than the first path. The formation of SiF₄ shows the possible etching mechanism.     

E.S.R. spectra of SiF3 radicals produced in a single crystal of SiF4

E.S.R. spectra of a γ-irradiated single crystal of SiF₄ were investigated. The spectra observed were attributed to SiF₃ radicals having ²⁸Si (I=0) and ²⁹Si (I=1/2) atoms. From the angular dependence of the spectral lines on rotation of the single crystal, hyperfine tensors were determined for three fluorine atoms and the ²⁹Si atom of the SiF₃ radical. The three fluorine atoms in the radical are equivalent, whereas the directions of their hyperfine tensors are different from one another owing to the pyramidal structure of the radical. In addition to the hyperfine analysis, the analysis of the superhyperfine structure due to neighbouring fluorine atoms gave information on the orientation of the radicals in the crystal and the mechanism of radical formation. The structure of the radical is discussed in comparison with that of the CF₃ radical.     

Theoretical total ionization cross-sections of CH x,CF x,SiH x,SiF x ( ) and CCl 4 targets by electron impact

Total ionization cross-sections of electron impact are calculated for the molecular targets CH_x, CF_x, SiH_x, SiF_x (x = 1-4) and CCl₄ at incident energies 20-3 000 eV. The calculation is based on Complex Scattering Potential approach, as developed by us recently. This leads to total inelastic cross-sections, from which the total ionization cross-sections are extracted by reasonable physical arguments. Extensive comparisons are made here with the previous theoretical and experimental data. The present results are satisfactory except for the CF_x and SiF_x (x = 1-3) radicals, for which the experimental data are lower than most of the theories by more than 50%. Received 23 May 2002 / Received in final form 24 October 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: knjoshipura@yahoo.com     

Molecular dynamics simulations of reactive etching of SiC by energetic fluorine

Molecular dynamics simulations were performed to investigate F continuously bombarding Si-terminated 3C-SiC(001) surfaces with incident energies of 10, 100 and 200 eV at normal incidence and room temperature. For an energy of 10 eV, deposition only occurs on the surface. For energies larger than 10 eV, accompanying the saturation of F uptake, a balance between F deposition from the incident atoms and F removal from the fluorinated substrate is established, while the steady-state etching is reached. The simulated results demonstrate that Si atoms in SiC are preferentially etched, which is in good agreement with experiments. The preferential etching of Si results in formation of a C-rich interfacial layer whose thickness increases with increasing incident energy. The analysis shows that Si-containing etch products are dominant. PACS 52.65.Yy; 81.65.Cf; 52.77.Dq     

Interaction of germanium with silicon dioxide

The interaction of germanium (Ge) adatoms with SiO₂ (silica) plays an important role in selective, heteroepitaxial growth of Ge(100) through windows created in silica on Si(100) and in the selective growth of Ge nanoparticles on hafnia, located at the bottom of pores etched through silica. Both processes rely on the inability of Ge to accumulate on silica. In hot wire chemical vapor deposition of Ge nanoparticles from GeH₄, etching of the silica has been invoked as one path to prevent accumulation of Ge on silica; whereas dense silica is not etched when Ge atoms are incident on the surface in molecular beam processes. Surface studies were conducted to determine the nature of oxidized Ge on SiO₂, to reconcile the etching claim with GeH₄, and to look for the additional etching product that must accompany GeO, namely SiO. Etching of silica is not found with GeH₄ or GeH_x fragments. A more complete examination of the Ge isotopes reveals instead the m/e 90 signal, previously attributed to GeO, originates from interactions between iron oxide impurities in the molybdenum holder, and hydrogen and GeH_x fragments. Coating the Mo with gold eliminates m/e 90 from Ge TPD spectra. The high temperature m/e 74 and m/e 2 peaks observed from 800 to 900 K are attributed to GeH_x decomposition to Ge and H followed by their desorption, while the appearance of GeO_x is attributed to possible reactions between GeH_x species with hydroxyl groups and/or oxidation of Ge clusters by background oxidants.