AVS 52nd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuM

Paper PS-TuM2
Effects of Polymer Deposition on Density Stabilization and Loss Rate of Radical Species in Fluorocarbon Plasmas

Tuesday, November 1, 2005, 8:40 am, Room 304

Session: Plasma Surface Interactions I
Presenter: K. Kumagai, Chubu University, Japan
Authors: K. Kumagai, Chubu University, Japan
K. Nakamura, Chubu University, Japan
K. Oshima, Sony, Japan
T. Tatsumi, Sony, 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.@footnote 1@ We reports on the effects of polymer deposition on the density variation and loss rate of radical species in fluorocarbon plasma reactors. 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 are set. A 400 kHz RF source serves alternating negative bias to the electrodes, and the AIB could control the deposition rate of the polymer on the biased wall. The radical density reached a steady state more quickly when the polymer deposition was suppressed with the AIB. In order to investigate the mechanism, as a parameter of thickness of the polymer, we measured a decay time of the radical density immediately after only the bias was turned off keeping the plasma-existing conditions. The delay time corresponding to a loss rate of the radical species increased with an increase in the polymer thickness, suggesting that the polymer deposition affected the loss rate. To keep the polymer thickness will be crucial for stabilization of the radical density. @FootnoteText@ @footnote 1@K. Nakamura et al: J. Vac. Sci. Techonol. A 18 (2000) 137.