Thermal gas evolution studies on a-C:H:Ta films

Abstract

Thermal induced gas evolution studies were performed on a-C:H:Ta films deposited by a sputtering process using a tantalum target and an argon-hydrocarbon gas mixture. Decreasing hydrocarbon concentration of the plasma atmosphere during the deposition results in an increasing tantal carbid (TaC) volume fraction, perceptible by x-ray diffraction measurements, while the a-C:H volume fraction decreases. Gas evolution spectra, similar to those of a-C:H and a-Si:C:N:H films, suggesting the presence of an a-C:H matrix with a void network structure. TaC forms precipitations in this matrix. The degree of crosslinking of the carbon atom network of the a-C:H matrix, which increases with an increasing volume fraction of TaC in the films, determines the thermal gas evolution concerning temperature and amount of hydrocarbons and argon. As shown also by gas effusion measurements, a more crosslinked matrix can also be obtained by reduction of the hydrogen content of the hydrocarbon gas, for instance, by substitution of methane by ethylene. Since the argon effusion temperature does not depend on film thickness, the argon effusion temperature may serve as a material property, which renders the comparison of different a-C:H materials possible, also in two phase systems like a-C:H:metal. The released hydrocarbon molecules were formed during the heating by alkyl group cleavage. Hydrocarbon gas release temperature is found to depend on the volume fraction of TaC, since bonding states of carbon atoms are influenced by the presence of tantalum, as indicated by x-ray-photoelectron-spectroscopy.

Factors affecting an efficient sealing of porous low-k dielectrics by physical vapor deposition Ta(N) thin films

“…In the literature, several references can be found that report the formation of Ta-C bonds at the interface when Ta or Ta͑N͒ compounds are deposited on substrates containing carbon, 16 due to the high formation enthalpy of the Ta-C bond (⌬ f H 0 (TaC) ϭϪ34.44 kcal/mol). 17,18 In this XPS study, no evident chemical shifts that directly prove the formation of a TaC compound have been observed. Note, however, that no significant shifts are expected in the Ta 4 f emission peak between the -N and the -C bonded Ta.…”

Influence of Deposition Parameters on the Composition and Structure of Reactively Sputtered Nanocomposite TaC/a-C:H Thin Films

“…TaC/a-C:H films were among the first to be demonstrated for use in tribological applications. 4,5,9,10,12,20,21 These works highlighted the low friction coefficient, high wear resistance, and high hardness that are achievable with TaC/a-C:H films. The present study demonstrates a statistical design of experiments approach to evaluate composition and structure trends in TaC/a-C:H films as a function of acetylene flow rate (Q C2H2 ), applied dc bias voltage (V b ), and substrate rotation rate ( Rot ).…”

Integration of Low‐ k Dielectric Films in Damascene Processes

“…A strong correlation was found between the carbon content of the dielectric and the sealing effi ciency of PVD Ta(N) fi lms on porous low-k fi lms. Higher carbon concentrations lead The tendency of Ta to react with carbon at the dielectric surface can lead to the formation of Ta-C [120,121]. Iacopi et al [119] proposed a model based on the formation of a transition layer at the Ta (N)/dielectric interface where Ta acts as a catalyst that locally promotes cross-linking (i.e., densifi cation) of the matrix.…”