AVS 49th International Symposium
    Plasma Science Monday Sessions
       Session PS1-MoA

Paper PS1-MoA1
Role of Fluorocarbon Radicals and Ions in SiO@sub 2@ Surface Etching Mechanism in Fluorocarbon-Based Discharges

Monday, November 4, 2002, 2:00 pm, Room C-103

Session: Dielectric Etch I
Presenter: G.S. Oehrlein, University of Maryland, College Park
Authors: X. Hua, University of Maryland, College Park
L. Ling, University of Maryland, College Park
X. Li, University of Maryland, College Park
G.S. Oehrlein, University of Maryland, College Park
M. Barela, University of New Mexico
H.M. Anderson, University of New Mexico
Correspondent: Click to Email
To provide information on the synergistic and respective roles of FC radical and ion fluxes in SiO@sub 2@ and Si surface etching mechanisms, we measured the surface chemical changes of deposited/steady-state fluorocarbon (FC) films, etching rates of FC, SiO@sub 2@ and Si, and determined the absolute gas phase density of CF, CF@sub 2@ and COF@sub 2@ radicals as a function of RF bias and gas composition of C4F8/Ar inductively coupled discharges. Ar addition to C@sub 4@F@sub 8@ strongly increases the plasma density relative to pure C@sub 4@F@sub 8@ (~ 4x at 90% Ar), and results in a dramatic increase of the ion/neutral flux ratio for C@sub 4@F@sub 8@/90%Ar discharges relative to C@sub 4@F@sub 8@ (>20). Nevertheless, the x-ray photoelectron spectra of FC films formed on SiO@sub 2@ and Si surfaces without RF bias remain remarkably similar to those of films produced in pure C@sub 4@F@sub 8@ discharges at much lower ion/neutral ratio. Upon applying an RF bias, etching of FC, SiO@sub 2@ or Si commences. The C1s spectra of FC surface films for C@sub 4@F@sub 8@/90%Ar discharges become strongly fluorine-deficient relative to conditions without RF bias, whereas the C1s spectra of FC films formed in C@sub 4@F@sub 8@ change little. Infrared laser absorption spectroscopy was used to determine CF, CF@sub 2@ and COF@sub 2@ densities over SiO@sub 2@ and Si surfaces, with and without RF bias, and as a function of gas mixture. Without RF bias (FC deposition), the CF, CF2 and COF@sub 2@ densities do not vary with substrate type. With an RF bias, the CF@sub 2@ density over a SiO@sub 2@ surface is strongly reduced relative to a Si surface, and the change reflects the relative SiO@sub 2@/Si etch rate ratio. The composite of the results provide a fairly detailed view of the dominant surface etching mechanism and ion/neutral synergy.