Plasma-enhanced deposition of fluorocarbon films was performed at 120°C from a mixture of pentafluoroethane (CF 3 CHF 2) and argon in a parallel plate plasma reactor. Mass spectrometry of the reactor effluent was used to gain an understanding of the plasma chemistry of this monomer. The monomer primarily dissociated into CF 3 • and CHF 2 • in the plasma. The results from mass spectrometry indicated that CHF 2 * was the primary precursor for deposition and that the fluorine radicals in the plasma were primarily scavenged as CF 4 and HF. Monomer conversion ͑fraction of monomer fragmented͒ in the plasma was determined based on mass spectrometer partial pressure analysis of CH 3 CHF ϩ fragments ͑parent molecule: CF 3 CHF 2 ͒ before and after plasma ignition. The conversion correlated directly with both the applied power and the deposition rate. The overall gas phase reactions did not change significantly with rf power within our range of operation, indicating a common reaction mechanism at all powers. No significant change in the composition of the deposited films was found, as measured by x-ray photoelectron spectroscopy ͑XPS͒, supporting the common mechanism conclusion. Further, XPS studies showed a fluorine-to-carbon ratio between 1.05 and 1.15 suggesting extensive crosslinking of the polymer. Infrared spectra of the deposited films showed negligible CH x concentration despite the presence of hydrogen in the monomer.

Effect of plasma interactions with low-κ films as a function of porosity, plasma chemistry, and temperature J. Synthesis of organically modified mesoporous silica as a low dielectric constant intermetal dielectricFluorocarbon films are deposited from mixtures of pentafluoroethane ͑PFE͒/argon and octafluorocyclobutane/argon in a parallel plate reactor at pressures of 0.75 and 1 Torr and substrate temperatures between 120 and 240°C. These monomers are compared in terms of plasma dissociation chemistries as well as chemical structure and properties ͑electrical, thermal, chemical, and optical͒ of the resulting films. Deposition rates with C 4 F 8 are significantly higher than CF 3 CHF 2 . With both monomers, the deposition rate decreases with an increase in substrate temperature, indicative of an adsorption limited process. Films deposited from both monomers are analyzed using Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy ͑XPS͒, thermogravimetric analysis ͑TGA͒, and capacitance measurements. XPS analyses indicate a higher flourine to carbon ratio for films deposited from C 4 F 8 . Likewise, these films have lower refractive indices (nϳ1.38-1.39) and lower dielectric constants (kϳ2.18-2.33) than PFE films (nϭ1.41, kϭ2.23-2.55). Films deposited from both monomers exhibit high dielectric losses (ϳ10 Ϫ2 -10 Ϫ3 ) at deposition temperatures Ͼ200°C. TGA analyses of films deposited from both monomers indicate comparable thermal stabilities up to a temperature of 300°C. However, the decomposition rate is much higher for C 4 F 8 films in the temperature range between 300 and 425°C. Thermal stability of films deposited from both monomers is enhanced at higher deposition temperatures. However, the sensitivity of thermal stability to deposition temperature is lower for films deposited from C 4 F 8 . A tradeoff exists between the electrical properties and thermal stability of films deposited from both monomers.

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Fluorocarbon films were deposited from pentafluoroethane/argon mixtures in a parallel-plate reactor at a pressure of 1 Torr and substrate temperatures between 120 and 210ЊC. Films deposited on substrates placed on the heated, grounded electrode as well as films formed on the powered electrode were analyzed using infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Polymer deposition rates decreased with an increase in substrate temperature indicating that reactant adsorption is the rate-limiting step. Films deposited on the powered electrode had an O/C ratio of 0.14, which was significantly higher than that of films deposited on the grounded electrode at elevated temperatures. Likewise, IR spectra of films on the powered electrode also showed significant contributions from CϭO related groups. TGA data indicated that the powered electrode films had ϳ3% weight loss at 250ЊC, while films deposited on the grounded electrode had ϳ1% weight loss at 250ЊC. The thermal stability of films deposited on the grounded electrode was significantly enhanced when deposited at higher substrate temperatures. XPS analyses indicated a decrease in the F/C ratio of the deposited films with an increase in substrate temperature. TGA analyses indicated that weight loss below 250ЊC was due primarily to the outgassing of low-molecular weight species from the fluorocarbon films. The higher weight loss region between 320 and 425ЊC was ascribed to polymer degradation due to scission of main chain C-C bonds and to evolution of HF and CO 2 .

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