IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Tuesday Sessions
       Session PS1-TuA

Paper PS1-TuA1
Gas Phase and Surface Diagnostic Measurements of High-density Plasma-based Etching Processes for Dielectrics Based on C@sub 4@F@sub 8@ Gas Mixtures with Ar, O@sub 2@ and N@sub 2@

Tuesday, October 30, 2001, 2:00 pm, Room 103

Session: Dielectric Etch I
Presenter: X. Li, University of Maryland
Authors: X. Li, University of Maryland
M. Fukasawa, Sony Corporation, Japan
G.S. Oehrlein, University of Maryland
M. Barela, University of New Mexico
H.M. Anderson, University of New Mexico
Correspondent: Click to Email
High-density plasma etching of dielectric films, e.g. SiO2 and low dielectric constant films, is an important process steps in integrated circuit manufacturing. Etching selectivity relative to the etching mask and insulating etch stop materials is required for these processes. Frequently gas mixtures rather than pure fluorocarbon gases are being employed. In this work we have studied the effect of adding O2 and Ar, two important gas additives, to C4F8 discharges produced using an inductively coupled plasma source. We measured fluorocarbon deposition and etching rates, SiO2, resist and silicon etching rates as a function of gas composition. In parallel, the absolute partial pressures of CF2, CF and COF2 radicals were measured using infrared laser absorption spectroscopy. Mass spectrometry was used to establish the importance of other gas phase species. In-situ ellipsometry and x-ray photoemission spectroscopy were used to obtain information on the surface processes for the various thin film materials. The effect of admixing O2 or Ar is shown to produce dramatic and non-obvious changes in the gas phase and surface chemistry, and enables to better address the technological objectives of the etching process. For instance, we have observed that the SiO2/resist and SiO2/Si etching selectivity can be increased by more than a factor of 3x at 20 mTorr by adding about 50% of Ar to C4F8. The infrared absorption measurements show that the partial pressures of CF and CF2 are increased by the addition of Ar despite the lower partial pressure of C4F8, and thicker fluorocarbon surface reaction layers are produced on silicon surfaces during steady-state etching.