AVS 53rd International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS1-WeA

Paper PS1-WeA4
Influence of Bombarding Energy on Stabilization of Radical Density of Fluorocarbon Plasma

Wednesday, November 15, 2006, 3:00 pm, Room 2009

Session: Plasma-Wall Interactions and Plasma Sources
Presenter: K. Kumagai, Chubu University, Japan
Authors: K. Kumagai, Chubu University, Japan
T. Tatsumi, Sony Corporation, Japan
K. Oshima, Sony Corporation, Japan
K. Nagahata, Sony Corporation, Japan
K. Nakamura, Chubu University, Japan
Correspondent: Click to Email
Fluorocarbon discharges have been widely used for etching processes of dielectric thin films for microfabrication. However, these have suffered from various problems, in particular, repeatability of the etching characteristics. The problem becomes recently severe due to narrow process margin for next generation ULSI devices. One of the major origins is plasma-surface interaction on polymer-deposited vessel wall, leading to significant time-variation of radical composition of the plasma. Alternating ion bombardment (AIB) method has been proposed to reduce such interactions by applying an RF bias to the chamber wall. We reports on suppression of the temporal density variation of fluorocarbon radicals caused by removal of the deposited polymer with ion bombardment as well as effects of ion bombarding energy on the density variation. 13.56 MHz inductively-coupled plasmas were produced in Ar-diluted C@sub 4@F@sub 8@ gases in a stainless steel chamber in which two semi-cylindrical electrodes were set. Oxygen plasma pretreatments were performed before each the discharge. A 400 kHz RF source served alternating negative bias to the electrodes, and the AIB could control the deposition rate of the polymer on the biased wall. When the polymer deposition was suppressed with the AIB, the radical density reached a steady state more quickly after the discharge initiation. However the rise time of the radical density was seriously influenced by the ion bombarding energy. Significant polymer deposition occurred at the wall at a too low ion bombarding energy. On the other hand, when the ion bombarding energy is too high for suppression of the polymer deposition, thickness of fluorocarbon reaction layer formed on the wall surface increased, resulting in longer time to be required to reach steady state surface conditions. Thus, there was an optimal ion bombarding energy for fast stabilization of the surface condition and the radical density.