小型感应耦合等离子体源及其等离子体特性
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摘要
等离子体小型化后往往会产生一些新的特点。如具有更高的等离子体密度,相对较低的电子温度等。小型等离子体源的发展进一步拓展了低温等离子体在许多领域中的特殊应用,如气体分析仪、离子推进器、微区消毒、等离子体显示、紫外光源等。众多小型等离子体的产生方式中,小型感应耦合方式由于其易加工,低成本等原因而备受人们关注。
本文介绍了一个自制的小型感应耦合等离子体源,天线绕制方式为圆筒螺旋线圈型,其感应线圈被绕制在一个外径为8mm、内径为6mm的石英管上,当线圈通以一定功率的射频信号时在石英管中激发产生低气压氩等离子体放电,激发产生等离子体下游羽辉长度超过了500mm。我们采用13.56MHz,27.12MHz和40.68MHz等三种频率激发产生等离子体,并利用朗缪尔探针和发射光谱技术对不同放电条件下所产生的小型感应耦合等离子体进行了测量与分析。
朗缪尔探针的实验结果表明,激发频率或射频输入功率的增加导致了功率耦合系数的增强,致使等离子体功率吸收的增强,从而引起了感应耦合等离子体的离子密度增大和电子温度下降。放电气压的增大会导致等离子体中电子和中性粒子碰撞频率的增强,从而提高了等离子体功率的吸收,有利于离子密度的增大,但是气压的进一步上升会导致等离子体中电子或离子能量扩散系数的下降,使得等离子体离子密度趋于饱和。由于双极扩散场以及强电磁场的局域,轴向方向上的离子密度和电子温度基本维持不变,低频激发条件下离子密度略有下降。利用气体追踪发射光谱法测量了感应放电的气体温度。可以发现,由于电子诱导加热的作用,气体温度随放电气压和输入功率的增加而增加,激发频率的提高也有助于等离子体气体温度的上升。等离子体轴向方向上,当远离激发线圈时,气体温度呈缓慢下降趋势。当放电气压,射频输入功率或激发频率增加时,电子激发温度均呈现下降趋势,同时,等离子体轴向方向上电子激发温度基本保持不变。
As a plasma source is scaled down, some unique characteristics of the plasma appear such as high gas temperature, high plasma density, etc. The development of Miniaturized Plasma Sources have extended their applications in many fields, such as gas analysers, ion thrusters, sterilizers, plasma displays, UV light source, etc. Among numerous Mini-plasma Sources, much attention of miniaturized inductively coupled plasma source has been paid due to easy fabrication, low cost, etc.
A kind of miniaturized inductively coupled plasma sources (mICP) has been presented in this paper. The antenna with certain turns depending on the driving frequency, is winded around a quartz tube with a outside diameter of 8mm and inside diameter of 6mm, argon plasma with a low pressure can be excited as rf signal with a certain input power applied on the antenna. Characteristics for the miniaturized inductively coupled plasma with different driving frequency of 13.56MHz, 27.12MHz and 40.68MHz, respectively, are investigated by using Langmuir probe and optical emission spectroscopy (OES) techniques.
From experimental measurements of Langmuir probe, it can be found that, due to enhancing power coupling coefficiency, the increase of rf input power and/or driving frequency causes the enhancement of plasma power absorption, hence leads to a rise in ion density and a drop in electron temperature in bulk plasma. Due to the rise of collisional between electron and neutral particles, the increasing pressure of Ar also improves the rf power absorption and is favor of increasing ion density. However, further increase of Ar pressure will lead to the drop in the electron/ion energy diffusion coefficient, thus cause the plasma density to be saturated. Due to strong confinement of ambipolar field and electromagnetic field, plasma density and electron temperature remain basically unchanged along the axis of plasma, only a slight drop in ion density occurs at low driving frequency. The gas temperature of mICP has been measured by using gas traced OES. It is found that, due to electron induced heating, rather than ion induced one, the gas temperature increases with rf input power and total pressure. In addition, the higher driving frequency helps to the increase in gas temperature in the plasma. Electron excitation temperature is increased by raising gas pressure, rf input power or dirving frequency, a drop in gas temperature and a constant in electron excitation temperature are also found away from the discharge region along the axis of plasma.
本文介绍了一个自制的小型感应耦合等离子体源,天线绕制方式为圆筒螺旋线圈型,其感应线圈被绕制在一个外径为8mm、内径为6mm的石英管上,当线圈通以一定功率的射频信号时在石英管中激发产生低气压氩等离子体放电,激发产生等离子体下游羽辉长度超过了500mm。我们采用13.56MHz,27.12MHz和40.68MHz等三种频率激发产生等离子体,并利用朗缪尔探针和发射光谱技术对不同放电条件下所产生的小型感应耦合等离子体进行了测量与分析。
朗缪尔探针的实验结果表明,激发频率或射频输入功率的增加导致了功率耦合系数的增强,致使等离子体功率吸收的增强,从而引起了感应耦合等离子体的离子密度增大和电子温度下降。放电气压的增大会导致等离子体中电子和中性粒子碰撞频率的增强,从而提高了等离子体功率的吸收,有利于离子密度的增大,但是气压的进一步上升会导致等离子体中电子或离子能量扩散系数的下降,使得等离子体离子密度趋于饱和。由于双极扩散场以及强电磁场的局域,轴向方向上的离子密度和电子温度基本维持不变,低频激发条件下离子密度略有下降。利用气体追踪发射光谱法测量了感应放电的气体温度。可以发现,由于电子诱导加热的作用,气体温度随放电气压和输入功率的增加而增加,激发频率的提高也有助于等离子体气体温度的上升。等离子体轴向方向上,当远离激发线圈时,气体温度呈缓慢下降趋势。当放电气压,射频输入功率或激发频率增加时,电子激发温度均呈现下降趋势,同时,等离子体轴向方向上电子激发温度基本保持不变。
As a plasma source is scaled down, some unique characteristics of the plasma appear such as high gas temperature, high plasma density, etc. The development of Miniaturized Plasma Sources have extended their applications in many fields, such as gas analysers, ion thrusters, sterilizers, plasma displays, UV light source, etc. Among numerous Mini-plasma Sources, much attention of miniaturized inductively coupled plasma source has been paid due to easy fabrication, low cost, etc.
A kind of miniaturized inductively coupled plasma sources (mICP) has been presented in this paper. The antenna with certain turns depending on the driving frequency, is winded around a quartz tube with a outside diameter of 8mm and inside diameter of 6mm, argon plasma with a low pressure can be excited as rf signal with a certain input power applied on the antenna. Characteristics for the miniaturized inductively coupled plasma with different driving frequency of 13.56MHz, 27.12MHz and 40.68MHz, respectively, are investigated by using Langmuir probe and optical emission spectroscopy (OES) techniques.
From experimental measurements of Langmuir probe, it can be found that, due to enhancing power coupling coefficiency, the increase of rf input power and/or driving frequency causes the enhancement of plasma power absorption, hence leads to a rise in ion density and a drop in electron temperature in bulk plasma. Due to the rise of collisional between electron and neutral particles, the increasing pressure of Ar also improves the rf power absorption and is favor of increasing ion density. However, further increase of Ar pressure will lead to the drop in the electron/ion energy diffusion coefficient, thus cause the plasma density to be saturated. Due to strong confinement of ambipolar field and electromagnetic field, plasma density and electron temperature remain basically unchanged along the axis of plasma, only a slight drop in ion density occurs at low driving frequency. The gas temperature of mICP has been measured by using gas traced OES. It is found that, due to electron induced heating, rather than ion induced one, the gas temperature increases with rf input power and total pressure. In addition, the higher driving frequency helps to the increase in gas temperature in the plasma. Electron excitation temperature is increased by raising gas pressure, rf input power or dirving frequency, a drop in gas temperature and a constant in electron excitation temperature are also found away from the discharge region along the axis of plasma.
引文
[1]国家自然科学基金委员会编著,《等离子体物理学》,科学出版社,1994
[2] A. R. Reinberg, US Patent, 1973, 3, 757, 733,
[3]菅井秀郎编著,《等离子体电子工程学》,科学出版社, 2002
[4] W. Hittorf, Wiedemanns Ann Phys., 1884, 21, 90
[5] L. Delzeit, L. McAninch, and B. A. Cruden, J. Appl. Phys., 2002, 91, 9, 6027-6033
[6] J. H. Yen, I. C. Leu, and C. C. Lin, Appl. Phys. A, 2005, 80, 415-421
[7] K. Teii, and T. Yoshida, J. Appl. Phys., 1999, 85, 3, 1864-1870
[8] Y. X. Wu, and M. A. Lieberman, Appl. Phys. Lett., 1998, 72, 7, 777-779
[9] S. J. Jung, K. N. Kim, and G. Y. Yeom, Thin Solid Films, 2006, 506– 507, 460-463
[10] Y. Yin, J. Messier, and J. Hopwood, IEEE TRANSACTIONS ON PLASMA SCIENCE, 1999, 27, 5, 1516-1524
[11] F. Iza, and J. Hopwood, Plasma Sources Sci. Technol., 2002, 11, 229-225
[12] C. S. Corr, J. Zanger, and R. W. Boswell, Appl. Phys. Lett., 2007, 91, 241501
[13] A. Dunaevsky, Y. Raitses, and N. J. Fisch, Appl. Phys. Lett., 2006, 88, 251502
[14] T. Ichiki, R. Taura, and Y. Horiike, J. Appl. Phys., 2004, 95, 1, 35-39
[15] H. Shairai, Y. Sakurai, and M. Yeo, Thin Solid Films, 2008, 516, 4456-4461
[16] F. F. Chen, Langmuir Probe Diagnostics, Mini-Course on Plasma Diagnostics, IEEE-ICOPS meeting, Jeju, Korea, June 5, 2003
[17] V. A. Godyak, R. B. Piejak, and B. M. Alexandrovich, Plasma Sources Sci. Technol., 1992, 1, 36-58
[18] O. B. Minayeva, and J. Hopwood, J. Appl. Phys., 2003, 94(5), 2821-2828
[19] D. M. Phillips, J. Phys. D: Appl. Phys., 1975, 8, 507-521
[20] R. A. Porter, and W. R. Harshbarger, J. Electrochem. Soc.:SOLID-STATE SCIENCE AND TECHNOLOGY, 1979, 460-464
[21] S. Popescu, Y. Ohtsu, and H. Fujita, J. Appl. Phys., 2007, 102, 093302
[22] M. Tuszewski, and J. A. Tobin, J. Vac. Sci. Technol. A, 1996, 14(3), 1096-1101
[23] M. Tuszewski, J. Appl. Phys., 2006, 100, 053301
[24] V. A. Godyak, R. B. Piejak, and B. M. Alexandrovich, Plasma Sources Sci. Technol., 2002, 11, 525-543
[25]甑汉生编著,《等离子体加工技术》,清华大学出版社,1990
[26]项志遴,俞昌旋编著,《高温等离子体诊断技术》,上海科学技术出版社,1982
[27]魏振澄,陈新坤,杨增田,杨宝仲等编著,《原子发射光谱分析原理》,天津科学技术出版社,1991
[28]辛仁轩编著,《等离子体发射光谱分析》,化学工业出版社,2005
[29]张家良,《低温等离子体发射光谱学研究》,大连理工大学博士学位论文,2002
[30] Hiden Analytical, Plasma Diagnostics ESPION Technical Information
[31] I. D. Sudit, and R. C. Woods, J. Appl. Phys., 1994, 76(8), 4488-4498
[32] M. A. Lieberman, and A. J. Lichtenberg, Principles of Plasma Discharges and Materials Processing (New York,Wiley), 1994
[33] X. J. Huang, Y. Xin, and Q. H. Yuan, Phys. Plasmas, 2008, 15, 073501
[34] S. Nunomura, and M. Kondo, J. Appl. Phys., 2007, 102, 093306.
[35] A. Chingsungnoen, J. I. B. Wilson, and V. Amornkitbamrung, Plasma Sourses Sci. Technol., 2007, 16, 434-440
[2] A. R. Reinberg, US Patent, 1973, 3, 757, 733,
[3]菅井秀郎编著,《等离子体电子工程学》,科学出版社, 2002
[4] W. Hittorf, Wiedemanns Ann Phys., 1884, 21, 90
[5] L. Delzeit, L. McAninch, and B. A. Cruden, J. Appl. Phys., 2002, 91, 9, 6027-6033
[6] J. H. Yen, I. C. Leu, and C. C. Lin, Appl. Phys. A, 2005, 80, 415-421
[7] K. Teii, and T. Yoshida, J. Appl. Phys., 1999, 85, 3, 1864-1870
[8] Y. X. Wu, and M. A. Lieberman, Appl. Phys. Lett., 1998, 72, 7, 777-779
[9] S. J. Jung, K. N. Kim, and G. Y. Yeom, Thin Solid Films, 2006, 506– 507, 460-463
[10] Y. Yin, J. Messier, and J. Hopwood, IEEE TRANSACTIONS ON PLASMA SCIENCE, 1999, 27, 5, 1516-1524
[11] F. Iza, and J. Hopwood, Plasma Sources Sci. Technol., 2002, 11, 229-225
[12] C. S. Corr, J. Zanger, and R. W. Boswell, Appl. Phys. Lett., 2007, 91, 241501
[13] A. Dunaevsky, Y. Raitses, and N. J. Fisch, Appl. Phys. Lett., 2006, 88, 251502
[14] T. Ichiki, R. Taura, and Y. Horiike, J. Appl. Phys., 2004, 95, 1, 35-39
[15] H. Shairai, Y. Sakurai, and M. Yeo, Thin Solid Films, 2008, 516, 4456-4461
[16] F. F. Chen, Langmuir Probe Diagnostics, Mini-Course on Plasma Diagnostics, IEEE-ICOPS meeting, Jeju, Korea, June 5, 2003
[17] V. A. Godyak, R. B. Piejak, and B. M. Alexandrovich, Plasma Sources Sci. Technol., 1992, 1, 36-58
[18] O. B. Minayeva, and J. Hopwood, J. Appl. Phys., 2003, 94(5), 2821-2828
[19] D. M. Phillips, J. Phys. D: Appl. Phys., 1975, 8, 507-521
[20] R. A. Porter, and W. R. Harshbarger, J. Electrochem. Soc.:SOLID-STATE SCIENCE AND TECHNOLOGY, 1979, 460-464
[21] S. Popescu, Y. Ohtsu, and H. Fujita, J. Appl. Phys., 2007, 102, 093302
[22] M. Tuszewski, and J. A. Tobin, J. Vac. Sci. Technol. A, 1996, 14(3), 1096-1101
[23] M. Tuszewski, J. Appl. Phys., 2006, 100, 053301
[24] V. A. Godyak, R. B. Piejak, and B. M. Alexandrovich, Plasma Sources Sci. Technol., 2002, 11, 525-543
[25]甑汉生编著,《等离子体加工技术》,清华大学出版社,1990
[26]项志遴,俞昌旋编著,《高温等离子体诊断技术》,上海科学技术出版社,1982
[27]魏振澄,陈新坤,杨增田,杨宝仲等编著,《原子发射光谱分析原理》,天津科学技术出版社,1991
[28]辛仁轩编著,《等离子体发射光谱分析》,化学工业出版社,2005
[29]张家良,《低温等离子体发射光谱学研究》,大连理工大学博士学位论文,2002
[30] Hiden Analytical, Plasma Diagnostics ESPION Technical Information
[31] I. D. Sudit, and R. C. Woods, J. Appl. Phys., 1994, 76(8), 4488-4498
[32] M. A. Lieberman, and A. J. Lichtenberg, Principles of Plasma Discharges and Materials Processing (New York,Wiley), 1994
[33] X. J. Huang, Y. Xin, and Q. H. Yuan, Phys. Plasmas, 2008, 15, 073501
[34] S. Nunomura, and M. Kondo, J. Appl. Phys., 2007, 102, 093306.
[35] A. Chingsungnoen, J. I. B. Wilson, and V. Amornkitbamrung, Plasma Sourses Sci. Technol., 2007, 16, 434-440