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容性耦合等离子体技术广泛应用在半导体工业、生物医药、环境等领域, 是不可替代的核心处理技术. 基于电非对称双频源驱动的容性耦合等离子体因其可以实现离子能量和离子通量的相对独立调控而一直被寄予厚望. 本文采用一维流体耦合蒙特卡罗模型和刻蚀槽模型, 对基于电非对称效应的双频容性耦合CF4/Ar混合气体放电进行了模拟研究. 研究表明, 随着电极间距的增大, 自偏压的绝对值和电负性均减小. 此外, 由于放电区域变大但边界损失保持不变, 会导致外部馈入功率显著增加和等离子体密度增大. 本文采用CF4/Ar混合气体, 其中Ar含量很高, 气体电负性不是很高, 因此放电模式在不同的电极间距下都是 α 模式和双极扩散模式的共同作用. 在电极间距逐渐变大的过程中, 因为自偏压的变化导致离子能量分布中最大离子能量减小并且离子能量展宽变窄, 功率极板处离子通量的变化不明显, 中性基团通量的增大十分显著, 这些变化最终导致相同时间内的刻蚀速率和形貌发生改变. 所以, 在未来研究中, 不仅离子能量和通量的独立控制, 优化离子通量和中性基团通量的协同作用达到调节刻蚀速率、改善刻蚀形貌同样是重要研究内容.
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关键词:
- 电非对称效应 /
- 离子和中性基团的协同作用 /
- 电极间距 /
- 放电模式
The capacitive CF4/Ar discharges driven by a dual frequency source based on the electrical asymmetry effect (EAE) are studied by using a one-dimensional fluid coupled with Monte-Carlo (MC) model and a two-dimensional trench model. The effects, induced by varying the relative gap distance, on self-bias voltage, electronegativity, ion flux, neutral flux and other plasma characteristics are systematically discussed. In this asymmetric discharge, as the gap distance increases, the absolute value of the self-bias voltage and electronegativity decrease. Meanwhile, the plasma density and absorption power increase accordingly because the effective discharge area expands but the boundary loss is still limited. In addition, both$ \mathrm{\alpha } $ mode and drift-ambipolar (DA) mode can play their important roles in the discharges with different gap distances, though DA mode is weakened in large gap discharge. Owing to the fact that the self-bias is larger and electronegativity is stronger for the case of smaller gap distance, the sheath expansion electric field at the powered electrode and the bulk electric field heat the electrons, leading the ionization rate to greatly increase near the collapse of the sheath at the grounded electrode. Besides, at the larger gap distance, the maximum value of the ionization rate decreases due to the reduction of electrons with relatively high-energy, and the ionization rate near the grounded electrode is reduced evidently. Moreover, with the increase of the gap distance, the maximum ion energy decreases and the ion energy distribution width becomes smaller due to the reduction of the self-bias voltage. Meanwhile, the etching rate increases a lot since the neutral flux increases significantly near the powered electrode. However, as the gap distance increases to 5 cm, the etching rate stops increasing and the trench width at the bottom becomes narrow because the neutral flux increases greatly compared with ion flux, forming a thick layer of polymer. So, besides separately controlling the ion energy and flux, optimizing the synergistic effect of ion flux and neutral group flux to adjust the etching rate and improve the etching morphology is also an interesting topic in the asymmetric CF4/Ar discharges.-
Keywords:
- electrical asymmetry effect /
- the synergy of ions and neutrals /
- gap distance /
- discharge mode
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[36] Tinck S, Boullart W, Bogaerts A 2009 J. Phys. D. Appl. Phys. 42 095204Google Scholar
[37] Brandt S, Berger B, Schüngel E, et al. 2016 Plasma Sources Sci. Technol. 25 045015Google Scholar
[38] Vasenkov A V, Li X, Oehrlein G S, Kushner M J 2004 J. Vac. Sci. Technol. A 22 511Google Scholar
[39] Zhao S X, Gao F, Wang Y N, Bogaerts A 2012 Plasma Sources Sci. Technol. 21 025008Google Scholar
[40] Huard C M, Sriraman S, Paterson A, Kushner M J 2018 J. Vac. Sci. Technol. A 36 06B101Google Scholar
[41] Schulze J, Derzsi A, Dittmann K, Hemke T, Meichsner J, Donkó Z 2011 Phys. Rev. Lett. 107 275001Google Scholar
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[1] Makabe T, Petrović Z 2006 Plasma Electronics: Applications in Microelectronic Device Fabrication (London: Taylor and Francis) pp3−9
[2] Lieberman M A, Lichtenberg A J 2005 Principles of Plasma Discharges and Materials Processing (New York: Wiley) pp1−750
[3] Agarwal A, Kushner M J 2009 J. Vac. Sci. Technol. A 27 37Google Scholar
[4] Sherpa S D, Ranjan A 2016 J. Vac. Sci. Technol. A 35 01A102Google Scholar
[5] Sekine M 2002 Appl. Surf. Sci. 192 270Google Scholar
[6] Kanarik K J, Tan S, Gottscho R A 2018 J. Phys. Chem. Lett. 9 4814Google Scholar
[7] Kanarik K J, Hudson E A, Gottscho R A, et al. 2015 J. Vac. Sci. Technol. A 33 020802Google Scholar
[8] Huang S, Huard C, Shim S, Nam S K, Song I C, Lu S, Kushner M J 2019 J. Vac. Sci. Technol. A 37 031304Google Scholar
[9] Takayoshi T, Hiroki K, HoriMasaru Z M, Akiko K, Toshihisa N, Nobuyoshi K 2016 J. Vac. Sci. Technol. A 35 01A103Google Scholar
[10] Booth J P, Cunge G, Chabert P, Sadeghi N 1999 J. Appl. Phys. 85 3097Google Scholar
[11] Williams K L, Martin I T, Fisher E R 2002 J. Am. Soc. MASS Spectrom. 13 518Google Scholar
[12] Flamm D L, Herb G K 1989 WITHDRAWN: Plasma Etching Technology—An Overview (Pittsburgh: Academic Press) pp1−89
[13] Sankaran A, Kushner M J 2004 J. Vac. Sci. Technol. A 22 1260Google Scholar
[14] Gasvoda R J, Van De Steeg A W, Bhowmick R, Hudson E A, Agarwal S 2017 ACS Appl. Mater. Interfaces 9 31067Google Scholar
[15] Stoffels W W, Stoffels E, Tachibana K 1998 J. Vac. Sci. Technol. A 16 87Google Scholar
[16] Cunge G, Booth J P 1999 J. Appl. Phys. 85 3952Google Scholar
[17] Zhang D, Kushner M J 2000 J. Vac. Sci. Technol. A 18 2661Google Scholar
[18] Metzler D, Engelmann S, Bruce R L, Oehrlein G S, Joseph E A, Li C 2015 J. Vac. Sci. Technol. A 34 01B101Google Scholar
[19] Winters H F, J.W.Coburn 1992 Surf. Sci. Rep. 14 161Google Scholar
[20] Sasaki K, Furukawa H, Suzuki C, Kadota K 1999 J. Appl. Phys. 38 954Google Scholar
[21] Kimizuka M, Ozaki Y, Watanabe Y 1997 J. Vac. Sci. Technol. B 15 66Google Scholar
[22] Capps N E, Mackie N M, Fisher E R 1998 J. Appl. Phys. 84 4736Google Scholar
[23] Fendel P, Francis A, Czarnetzki U 2005 Plasma Sources Sci. Technol. 14 1Google Scholar
[24] Booth J P, Abada H, Chabert P, Graves D B 2005 Plasma Sources Sci. Technol. 14 273Google Scholar
[25] Kanarik K J, Tan S, Yang W, et al. 2017 J. Vac. Sci. Technol. A 35 05C302Google Scholar
[26] Huard C M Sriraman S, Kanarik K J, Zhang Y, Kushner M J, Paterson A 2017 J. Vac. Sci. Technol. A 35 031306Google Scholar
[27] Heil B G, Czarnetzki U, Brinkmann R P, Mussenbrock T 2008 J. Phys. D. Appl. Phys. 41 165202Google Scholar
[28] Zhang Y, Kushner M J, Sriraman S, Marakhtanov A, Holland J, Paterson A 2015 J. Vac. Sci. Technol. A 33 031302Google Scholar
[29] Zhang Y, Zafar A, Coumou D J, Shannon S C, Kushner M J 2015 J. Appl. Phys. 117 233302Google Scholar
[30] Zhang Y R, Hu Y T, Gao F, Song Y H, Wang Y N 2018 Plasma Sources Sci. Technol. 27 55003Google Scholar
[31] Zhang Y R, Hu Y T, Wang Y N 2020 Plasma Sources Sci. Technol. 29 84003Google Scholar
[32] Schulze J, Derzsi A, Donkó Z 2011 Plasma Sources Sci. Technol. 20 045008Google Scholar
[33] Brandt S, Berger B, Donkó Z, Derzsi A, Schüngel E, Koepke M, Schulze J 2019 Plasma Sources Sci. Technol. 28 95021Google Scholar
[34] Wang X F, Jia W Z, Song Y H, Zhang Y Y, Dai Z L, Wang Y N 2017 Phys. Plasmas 24 113503Google Scholar
[35] Phelps A V, Petrović Z L 1999 Plasma Sources Sci. Technol. 8 06B101Google Scholar
[36] Tinck S, Boullart W, Bogaerts A 2009 J. Phys. D. Appl. Phys. 42 095204Google Scholar
[37] Brandt S, Berger B, Schüngel E, et al. 2016 Plasma Sources Sci. Technol. 25 045015Google Scholar
[38] Vasenkov A V, Li X, Oehrlein G S, Kushner M J 2004 J. Vac. Sci. Technol. A 22 511Google Scholar
[39] Zhao S X, Gao F, Wang Y N, Bogaerts A 2012 Plasma Sources Sci. Technol. 21 025008Google Scholar
[40] Huard C M, Sriraman S, Paterson A, Kushner M J 2018 J. Vac. Sci. Technol. A 36 06B101Google Scholar
[41] Schulze J, Derzsi A, Dittmann K, Hemke T, Meichsner J, Donkó Z 2011 Phys. Rev. Lett. 107 275001Google Scholar
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