Molecular dynamics simulations of Si etching in Cl- and Br-based plasmas: Cl+ and Br+ ion incidence in the presence of Cl and Br neutrals
Molecular dynamics simulations of Si etching in Cl- and Br-based plasmas: Cl+ and Br+ ion incidence in the presence of Cl and Br neutrals
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DOI：
10.1063/1.4937449
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发表时间：
2015-12-21
影响因子：
3.2
通讯作者：
Ono, Kouichi
中科院分区：
文献类型：
--
作者：
Nakazaki, Nobuya;Takao, Yoshinori;Ono, Kouichi
采用经典分子动力学（MD）方法模拟了Cl ~+和Br ~+离子入射到Si（100）表面时Cl和Br中性粒子的作用，以更好地理解Cl和Br基等离子体刻蚀Si时离子增强的表面反应动力学.离子以E-i = 20-500 eV范围内的平移能垂直入射到表面上，并且E-n = 0.01 eV的低能中性粒子也以γ（0）（n）/γ（0）（i）= 0-100范围内的中性粒子与离子通量比垂直入射到其上，其中改进的Stillinger-Weber势形式用于所关注的原子间势。目前模拟的蚀刻产率和阈值与先前报道的Cl-2和Br-2等离子体以及Cl+，Cl-2（+），和Br+束中的Si蚀刻的实验结果一致，并且模拟的产物化学计量与在Cl-2中Ar+束入射到Si上期间观察到的结果一致。此外，卤素原子的表面覆盖率，卤化层厚度，表面化学计量比，和深度分布的表面产物模拟的γ（0）（n）/γ（0）（i）= 100是在良好的协议与观察依赖于E-i报道的Si蚀刻在Cl-2等离子体。分子动力学还表明，Si/Br体系的产率、覆盖率和表面层厚度均小于Si/Cl体系，而产物和表面化学计量中的高级卤代物种的百分比在Si/Br体系中较大。分子动力学进一步表明，在两个体系中，从表面脱附的产物和卤素吸附物的平动能分布都近似于两个温度T-1（约2500 K）和T-2（约7000- 40000 K）的Maxwell分布。这些能量分布讨论的解吸或蒸发的热点形成通过化学增强的物理溅射和物理增强的化学溅射，这到目前为止被推测都发生在离子增强的表面反应动力学的等离子体蚀刻。(C)2015 AIP Publishing LLC.
Classical molecular dynamics (MD) simulations have been performed for Cl+ and Br+ ions incident on Si(100) surfaces with Cl and Br neutrals, respectively, to gain a better understanding of the ion-enhanced surface reaction kinetics during Si etching in Cl-and Br-based plasmas. The ions were incident normally on surfaces with translational energies in the range E-i = 20-500 eV, and low-energy neutrals of E-n = 0.01 eV were also incident normally thereon with the neutral-to-ion flux ratio in the range Gamma(0)(n)/Gamma(0)(i) = 0-100, where an improved Stillinger-Weber potential form was employed for the interatomic potential concerned. The etch yields and thresholds presently simulated were in agreement with the experimental results previously reported for Si etching in Cl-2 and Br-2 plasmas as well as in Cl+, Cl-2(+), and Br+ beams, and the product stoichiometry simulated was consistent with that observed during Ar+ beam incidence on Si in Cl-2. Moreover, the surface coverage of halogen atoms, halogenated layer thickness, surface stoichiometry, and depth profile of surface products simulated for Gamma(0)(n)/Gamma(0)(i) = 100 were in excellent agreement with the observations depending on E-i reported for Si etching in Cl-2 plasmas. The MD also indicated that the yield, coverage, and surface layer thickness are smaller in Si/Br than in Si/Cl system, while the percentage of higher halogenated species in product and surface stoichiometries is larger in Si/Br. The MD further indicated that in both systems, the translational energy distributions of products and halogen adsorbates desorbed from surfaces are approximated by two Maxwellians of temperature T-1 approximate to 2500K and T-2 approximate to 7000-40 000 K. These energy distributions are discussed in terms of the desorption or evaporation from hot spots formed through chemically enhanced physical sputtering and physically enhanced chemical sputtering, which have so far been speculated to both occur in the ion-enhanced surface reaction kinetics of plasma etching. (C) 2015 AIP Publishing LLC.