AVS 52nd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA2
Application of the Shaped Electrode Technique to a Large Area Rectangular Capacitively-Coupled Plasma Reactor to Suppress Standing Wave Non-Uniformity

Thursday, November 3, 2005, 2:20 pm, Room 304

Session: Plasma Sources and Equipment
Presenter: L. Sansonnens, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
Authors: L. Sansonnens, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
C. Ellert, UNAXIS-Balzers AG, Liechtenstein
A. Buechel, UNAXIS-Balzers AG, Liechtenstein
H. Schmidt, EPFL, Switzerland
A.A. Howling, EPFL, Switzerland
C. Hollenstein, EPFL, Switzerland
Correspondent: Click to Email
The use of VHF (very high frequency) instead of the standard 13.56 MHz excitation frequency in capacitively-coupled plasma reactors has been shown to be a promising technique for plasma-enhanced chemical vapor deposition of thin films such as amorphous or microcrystalline silicon used for the production of photovoltaic solar cells or thin film transistors for flat screens. In particular, the use of VHF has been shown to increase the deposition rate and to reduce the sheath voltage and maximum ion energy bombardment at constant plasma power. Both effects favor deposition at higher rates without degrading the thin film electronic properties. However, these advantages have generally been demonstrated in small area plasma reactors, and it has been shown that electromagnetic standing wave effects becomes the main source of non-uniformity limiting the use of VHF in large area reactors exceeding 1 m@super 2@ required for industrial applications. Recently, it has been proposed to use a shaped electrode (together with a thin dielectric plate in order to confine the plasma in a constant interelectrode gap) in place of the conventional flat electrode in order to suppress the standing wave non-uniformity. In this work, the application of the shaped electrode technique for standing wave suppression in a large area rectangular industrial reactor (substrate area: 1.1 m x 1.25 m) will be presented. In particular, film thickness uniformities for amorphous silicon deposited with and without shaped electrode at an excitation frequency of 41 MHz will be compared, and some of the implementation difficulties of the shaped electrode technique for industrial processes will be discussed.