Plasma etching of Si and SiO/sub 2/: The effect of oxygen additions to CF/sub 4/ plasmas
The plasma etching of silicon and silicon dioxide in CF/sub 4/-O/sub 2/ mixtures has been studied as a function of feed-gas composition in a 13.56-MHz plasma generated in a radial-flow reactor at 200 W and 0.35 Torr. Conversion of CF/sub 4/ to stable products (CO, CO/sub 2/, COF/sub 2/, and SiF/sub 4/) and the concentration of free F atoms ((F)) in the plasma were measured using a number of different diagnostics. The rate of etching, the concentration of F atoms, and the intensity of emission from electronically excited F atoms (3s/sup 2/P--3p/sup 2/P/sup 0/ transition at 703.7 nm) each exhibit a maximum value as a function of feed-gas composition ((O/sub 2/)); these respective maxima occur at distinct oxygen concentrations. For SiO/sub 2/, the variation in etching rate with (O/sub 2/) is accounted for by a proportional variation in (F), the active etchant. The etching of silicon also occurs by a reaction with F atoms, but oxygen competes with F for active surface sites. A quantitative model which takes oxygen adsorption into account is used to relate the etch rate to (F). The initial increase of (F) with (O/sub 2/) is accounted for by a sequence of reactions initiating with the production of CF/sub 3/ radicals by electron impact and followed by a reaction of CF/sub 3/ with oxygen. When (O/sub 2/) exceeds approx.23% (under the present discharge conditions), (F) decreases due, probably, to a decrease in electron energy with an increase of oxygen in the feed gas.
- Research Organization:
- Bell Laboratories, Murray Hill, New Jersey 09794
- OSTI ID:
- 6927381
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 49:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SILICON
ETCHING
ADSORPTION
CARBON FLUORIDES
CHEMICAL REACTION KINETICS
EMISSION SPECTRA
EXCITED STATES
FLUORINE
GLOW DISCHARGES
OXYGEN
PLASMA DIAGNOSTICS
RADICALS
SILICON OXIDES
SURFACES
CARBON COMPOUNDS
CHALCOGENIDES
CRYOGENIC FLUIDS
ELECTRIC DISCHARGES
ELEMENTS
ENERGY LEVELS
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
KINETICS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SEMIMETALS
SILICON COMPOUNDS
SORPTION
SPECTRA
SURFACE FINISHING
700102* - Fusion Energy- Plasma Research- Diagnostics