AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS+MS-TuM

Paper PS+MS-TuM11
Dependence of Radical Densities on Fluorocarbon Feed Gases in a Dielectric Etch Plasma

Tuesday, November 5, 2002, 11:40 am, Room C-105

Session: Plasma Diagnostics and Sensors
Presenter: E.A. Hudson, Lam Research Corp.
Authors: E.A. Hudson, Lam Research Corp.
J. Luque, Lam Research Corp.
N. Bulcourt, Ecole Polytechnique, France
J.P. Booth, Ecole Polytechnique, France
Correspondent: Click to Email
Unsaturated fluorocarbon gases are increasingly important for critical dielectric etch applications. Under typical plasma etch conditions, these feed gases promote the deposition of fluorocarbon polymer films. Using process parameters to tune the polymer deposition characteristics, one can control the critical dimension and profile of the etched feature, and minimize the loss of the photoresist mask. Different unsaturated fluorocarbon gases produce different process results, for reasons which are poorly understood. In an effort to better understand these differences, the plasma radical composition has been analyzed for a range of feed gases including the unsaturated fluorocarbons octofluorocyclobutane(C@sub 4@F@sub 8@) and octafluorocyclopentene (C@sub 5@F@sub 8@), and also a saturated compound, perfluoroethane (C@sub 2@F@sub 6@). Optical emission spectroscopy (OES) and broad-band UV absorption spectroscopy (UVAS) have been used to measure radical densities in a dual-frequency, capacitively-coupled, dielectric etch reactor. Species detected include CF, CF@sub 2@, and F. Notable variations in radical densities were observed for a series of processes based on Ar, O@sub 2@, and one of the fluorocarbon feed gases. CF@sub 2@ density, in particular, showed a strong dependence on fluorocarbon feed gas. The F/CF2 density ratio increased by more than a factor of 2 when C@sub 2@F@sub 6@ was substituted for C@sub 5@F@sub 8@. For each fluorocarbon feed gas, the sensitivity to changes in the O@sub 2@ flow has been evaluated. Results suggest that the role of oxygen in controlling polymer film thickness in and around etched features is related to polymer formation as well as polymer removal.