AVS 45th International Symposium
    Plasma Science and Technology Division Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM7
Plasma Kinetics of Silicon Dioxide Etching with Fluorocarbon

Tuesday, November 3, 1998, 10:20 am, Room 318/319/320

Session: Oxide Etching
Presenter: H. Chae, Massachusetts Institute of Technology
Authors: H. Chae, Massachusetts Institute of Technology
H. Sawin, Massachusetts Institute of Technology
M.T. Mocella, DuPont Fluoroproducts
Correspondent: Click to Email
Plasma kinetics of silicon dioxide etching was studied in various conditions: i) oxide cleaning after PECVD(plasma enhanced chemical vapor deposition) ii) oxide etching in an inductively coupled plasma. Chamber cleaning after PECVD of silicon dioxide is known to be one of the major emission sources of perfluorocompounds (PFCs) which have high global warming potentials and very long atmospheric lifetimes. Silicon dioxide etching mechanism in the cleaning condition was studied in this work with various kinds of fluorine containing compounds such as C@sub 2@F@sub 6@, CF@sub 3@CF@sub 2@OCF=CF@sub 2@ (PEVE), NF@sub 3@, F@sub 2@. Silicon dioxide was etched in high temperature of 400@degree@C in parallel plate plasma reactor after TEOS (tetraethyl-orthosilicate) oxide deposited by PECVD. The kinetic study using actinometry measurement of atomic F shows linear correlation between silicon dioxide etching rate and F atom concentration. Arrhenius plots show low activation energies about 0.05 eV below 100 @degree@C and about 0.16 eV above 200@degree@C. The activation energy measurement indicates that ion-enhanced etching is dominant mechanism below 100@degree@C and F atom spontaneous chemical etching is dominant above 200@degree@C. Silicon dioxide etching in high-density plasma can provide high etching rate and good directionality without device damage. However, there are a lot of concerns about RIE(reactive ion etching) lag, inverse RIE lag, etch stop and low photoresist selectivity. Profile evolution modeling can reveal the mechanism of the concerns mentioned above as well as other detail feature profiles like bowing, trenching and faceting. However, parameters for the profile modeling are not available. In this study an inductively couple plasma reactor was built with diagnostic capabilities of mass spectrometer and quartz crystal microbalance. Oxide etching and fluorocarbon deposition rate dependence on ion energy, ion-to-neutral flux ratio, ion impingement angle, and surface temperature were measured. At the same time, ion composition was measured with mass spectrometer.