Plasma etching of Si and SiO/sub 2/: The effect of oxygen additions to CF/sub 4/ plasmas

Journal Article · Sat Jul 01 04:00:00 EDT 1978 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.325382· OSTI ID:6927381

Mogab, C J; Adams, A C; Flamm, D L

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), Journal Name: J. Appl. Phys.; (United States) Vol. 49:7; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102* -- Fusion Energy-- Plasma Research-- Diagnostics
ADSORPTION
CARBON COMPOUNDS
CARBON FLUORIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CRYOGENIC FLUIDS
ELECTRIC DISCHARGES
ELEMENTS
EMISSION SPECTRA
ENERGY LEVELS
ETCHING
EXCITED STATES
FLUIDS
FLUORIDES
FLUORINE
FLUORINE COMPOUNDS
GLOW DISCHARGES
HALIDES
HALOGEN COMPOUNDS
HALOGENS
KINETICS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PLASMA DIAGNOSTICS
RADICALS
REACTION KINETICS
SEMIMETALS
SILICON
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
SURFACE FINISHING
SURFACES