Diamond and Related Materials 11 (2002) 1831–1836 0925-9635/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0925-9635 Ž 02 . 00167-X Fluorinated a-C:H films investigated by thermal-induced gas effusion L.G. Jacobsohn , S.S. Camargo Jr. , F.L. Freire Jr. * a b a, Departamento de Fısica, Pontifıcia Universidade Catolica do Rio de Janeiro, Rua Marques de Sao Vicente, 225-Gavea, Caixa Postal 38071, a ´ ´ ´ ˆ ˜ ´ 22452-970 Rio de Janeiro, RJ, Brazil Programa de Engenharia Metalurgica e de Materiais, COPPE, Universidade Federal do Rio de Janeiro, Caixa Postal 68505, b ´ 21945-970 Rio de Janeiro, RJ, Brazil Received 2 January 2002; received in revised form 8 April 2002; accepted 17 June 2002 Abstract Using thermal-induced gas effusion the decomposition of plasma deposited fluorinated a-C:H films has been investigated. The main contributions to the effusion spectra were found to come from hydrogen, hydrocarbons, CF and HF. It is observed that 4 hydrogen-related effusion is progressively substituted by the effusion of CF -related species as the fluorine content is increased, 4 confirming that fluorine atoms substitute hydrogen in the amorphous network. At low fluorine contents (-10 at.%) the material is relatively compact and the effusion of hydrogen-related species (hydrogen molecules and hydrocarbons) dominate. For high enough fluorine concentrations a strong change in the effusion characteristics indicates that an interconnected network of voids is present. Strong effusion of CF -related species is found to be consistent with a surface desorption process and can be observed 4 when CF bonds are present in the film microstructure and the void network dimensions are large enough, i.e. for films with the n highest fluorine contents (;20 at.%). The effusion results can be correlated to a structural transition from diamond-like to polymer-like film.  2002 Elsevier Science B.V. All rights reserved. Keywords: Amorphous hydrogenated carbon; Fluorine; Mass spectrometry; Structure 1. Introduction Hydrogenated amorphous carbon (a-C:H) is a very interesting material due to its outstanding properties like high hardness, chemical inertness and low friction w1x. A way to further improve the properties of this material is by the incorporation of other elements. Among the many possibilities already investigated, the incorporation of fluorine has recently attracted the attention of the scientific community due to the possibility of lowering the internal stress w2x, to suppress the CH absorption n bands w3x and to reduce the friction coefficient of a-C:H films w4x. In fact, fluorinated a-C:H (a-C:F:H) films present many possible applications such as wide-trans- parency window for optical devices operating in the infrared part of the spectrum w3x, low friction and low *Corresponding author. Tel.: q55-21-53114-1272; fax: q55-21- 3114-1275. E-mail address: lazaro@vdg.fis.puc-rio.br (F.L. Freire Jr.). surface energy coatings w4,5x and low dielectric constant material for interconnect dielectrics w6x. In fact, dielec- tric constants as low as 2.1 were achieved in plasma deposited film w7x. The structure of a-C:F:H films has been investigated by several techniques which revealed that a progressive structural change from a diamond- like to a polymer-like material occurs when the concen- tration of fluorine-containing precursor gas in the deposition atmosphere is increased w2,8x. Moreover, it was observed that fluorine is incorporated into the films at the expense of hydrogen atoms w2x. As regards application as an interconnect dielectric material, thermal stability is of major importance since the interconnect layer is submitted to thermal annealing during subsequent integrate circuit manufacturing steps. A Raman spectroscopy investigation has shown that progressive graphitization occurs at high annealing tem- peratures w9x. Another study showed that an annealing- induced fluorine loss occurs by removing free radicals