AVS 46th International Symposium
    Plasma Science and Technology Division Wednesday Sessions
       Session PS-WeA

Paper PS-WeA4
Chemical Bonding Arrangement Approach for Selective Radical Generation in High-density, Low-pressure Fluorocarbon Plasma

Wednesday, October 27, 1999, 3:00 pm, Room 609

Session: Dielectric Etching
Presenter: S. Samukawa, NEC Corporation, Japan
Authors: S. Samukawa, NEC Corporation, Japan
T. Mukai, NEC Corporation, Japan
Correspondent: Click to Email
Generally, SiO@sub 2@ etching is done with fluorocarbon gases so that a fluoropolymer layer is deposited on the underlying silicon to enhance the etching selectivity for SiO@sub 2@ over silicon and silicon nitride. CF@sub 2@ radicals have been used as the main gas precursor for polymer deposition, and CF@sub 3@@super +@ ions have been the dominant etchant for SiO@sub 2@ films. The CF@sub 3@@super +@ ions are mainly generated from CF@sub 3@ radicals. Thus, to realize high-performance SiO@sub 2@ etching, precise control of CF@sub 2@ and CF@sub 3@ radicals in the fluorocarbon gas plasmas is indispensable. In this paper, we discuss how the efficiency of radical generation is affected by the chemical bonding of gas molecules in the fluorocarbon gas plasma. We found that dissociation of the C=C and C-I bonds are 5 times and 6 times higher than that of the C-C bond in a fluorocarbon gas plasma. As a result, a C@sub 2@F@sub 4@ plasma could generate a higher density of CF@sub 2@ radicals than a C@sub 4@F@sub 8@ plasma. The CF@sub 3@I is also efficient source of CF@sub 3@ radicals (CF@sub 3@@super +@ ions). By changing the gas-flow ratio of the CF@sub 3@I and C@sub 2@F@sub 4@ mixture, the density ratios of CF@sub 2@ and CF@sub 3@ (CF@sub 3@@super +@) could be independently controlled and high performance SiO@sub 2@ etching could be obtained. The appropriate choice of chemical bonding in the fluorocarbon gases is a useful way to control the generation of radicals and ions for SiO@sub 2@ etching.