Comparison of CH, C3, CHF, and CF2 Surface Reactivities during Plasma-Enhanced Chemical Vapor Deposition of Fluorocarbon Films

Abstract

The overall character of films deposited using plasma-enhanced chemical vapor deposition relies on the interactions of gas-phase molecules with the depositing film surface. The steady-state surface interactions of CH, C3, CHF, and CF2 have been characterized at the interface of depositing fluorocarbon (FC) films using the imaging of radicals interacting with surfaces (IRIS) technique. IRIS measurements show that the relative gas-phase densities of CH, C3, CHF, and CF2 in mixed FC plasmas depend on the CH2F2/C3F8 ratio. Similar results are found using optical emission spectroscopy to monitor the production of excited-state plasma species. The effects of plasma parameters, such as the feed gas composition and substrate bias on the radical surface, were measured. Under all conditions, the surface reactivity for CH radicals is near unity, whereas those for C3, CHF, and CF2 exhibit very low surface reactivity but also show some dependence on experimental parameters. Under some conditions, CF2 and CHF are generated at the surface of the depositing film. Surface reactivity measurements indicate that CF2, CHF, and C3 may contribute to FC growth only when adsorbing at reactive sites at the film surface. Moreover, the low surface reactivities of singlet species such as C3, CF2, and CHF may be related to the electronic configuration of the molecules.