Browse DORAS
Browse Theses
Latest Additions
Creative Commons License
Except where otherwise noted, content on this site is licensed for use under a:

Radio-frequency discharge power measurement with emphasis on collisionless electron heating in capacitive sheaths

Gahan, David (2006) Radio-frequency discharge power measurement with emphasis on collisionless electron heating in capacitive sheaths. PhD thesis, Dublin City University.

Full text available as:

PDF - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader


Many of today’s processing plasma tools are operated at low pressures to achieve high etch directivity and reduce side erosion on the wafer. At these pressures electron-neutral collisions are rare and the electrons cannot gain energy through the Ohmic heating process. Instead the heating mechanism is attributed to a stochastic process between the electrons and the sheath electric field. Theoretical models of this stochastic process include the hard wall approximation and the pressure heating effect. The former is inconsistent with electron current conservation at the sheath whilst the later shows a difference in power absorption when electron loss to the electrodes is considered. This thesis examines the effects of electron current on power coupling in a capacitive sheath by controlling this current with an additional DC bias applied to an rf biased electrode. Experimental and particle-in-cell model results for a low pressure argon plasma are compared and presented. Results show th a t the electron power absorption is more effective when the electron conduction current is removed, as predicted by the earlier theoretical work. The model also shows a high harmonic content on the sheath voltage which is attenuated by removing the electron current. These high frequency harmonics are measured in the experiment, with an unbiased probe connected to a spectrum analyzer, and their correlation with the electron current is in agreement with the model results. It is found th a t the high frequency oscillations do not contribute to the power absorption in an average sense. Finally a novel rf power sensor is presented and compared with an industrial standard power meter. The design incorporates directional coupler and I-V probe techniques to determine the power. This sensor is found to out perform the standard meter over a wide range of conditions. Its ability to measure the power at the fundamental as well as harmonic frequencies makes it a particularly useful plasma diagnostic.

Item Type:Thesis (PhD)
Date of Award:2006
Supervisor(s):Hopkins, Michael B. and Turner, Miles M.
Uncontrolled Keywords:semiconductor manufacture; plasma etching; sheath electric field; capacitive sheaths
Subjects:Engineering > Electronic engineering
Engineering > Electronics
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Physical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
ID Code:17255
Deposited On:22 Aug 2012 14:48 by Fran Callaghan. Last Modified 20 Apr 2017 12:21

Download statistics

Archive Staff Only: edit this record