Changes in the ion flux and the time-averaged ion distribution functions are reported for pulsed, inductively coupled RF plasmas (ICPs) operated over a range of duty cycles. For helium and argon plasmas, the ion flux increases rapidly after the start of the RF pulse and after about 50 μs reaches the same steady state value as that in continuous ICPs. Therefore, when the plasma is pulsed at 1 kHz, the ion flux during the pulse has a value that is almost independent of the duty cycle. By contrast, in molecular electronegative chlorine/chlorosilane plasmas, the ion flux during the pulse reaches a steady state value that depends strongly on the duty cycle. This is because both the plasma chemistry and the electronegativity depend on the duty cycle. As a result, the ion flux is 15 times smaller in a pulsed 10% duty cycle plasma than in the continuous wave (CW) plasma. The consequence is that for a given synchronous RF biasing of a wafer-chuck, the ion energy is much higher in the pulsed plasma than it is in the CW plasma of chlorine/chlorosilane. Under these conditions, the wafer is bombarded by a low flux of very energetic ions, very much as it would in a low density, capacitively coupled plasma. Therefore, one can extend the operating range of ICPs through synchronous pulsing of the inductive excitation and capacitive chuck-bias, offering new means by which to control plasma etching.
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March 2013
Research Article| February 05 2013
Ion flux and ion distribution function measurements in synchronously pulsed inductively coupled plasmas
Melisa Brihoum;
Melisa Brihoum
Laboratoire des Technologies de la Microélectronique CNRS
, Grenoble Cedex 9, Isere 38054, France
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Gilles Cunge;
Gilles Cunge a)
Laboratoire des Technologies de la Microélectronique CNRS
, Grenoble Cedex 9, Isere 38054, France
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Maxime Darnon;
Maxime Darnon
Laboratoire des Technologies de la Microélectronique CNRS
, Grenoble Cedex 9, Isere 38054, France
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David Gahan;
David Gahan
Impedans Ltd., Dublin 17,
Ireland
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Olivier Joubert;
Olivier Joubert
Laboratoire des Technologies de la Microélectronique CNRS
, Grenoble Cedex 9, Isere 38054, France
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Nicholas St. J. Braithwaite
Nicholas St. J. Braithwaite
Department of Physical Sciences, The Open University
, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
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a)
Electronic mail: gilles.cunge@cea.fr
J. Vac. Sci. Technol. A 31, 020604 (2013)
Article history
Received:
December 21 2012
Accepted:
January 18 2013
Citation
Melisa Brihoum, Gilles Cunge, Maxime Darnon, David Gahan, Olivier Joubert, Nicholas St. J. Braithwaite; Ion flux and ion distribution function measurements in synchronously pulsed inductively coupled plasmas. J. Vac. Sci. Technol. A 1 March 2013; 31 (2): 020604. https://doi.org/10.1116/1.4790364
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