Study and Optimization of PECVD Films Containing Fluorine and Carbon as Ultra Low Dielectric Constant Interlayer Dielectrics in ULSI Devices



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A V S Amer Inst Physics


Fluorinated amorphous carbon films that are thermally stable at 400 ⁰C have been deposited in a plasma enhanced chemical vapor deposition system using tetrafluorocarbon and disilane (5% by volume in helium) as precursors. The bulk dielectric constant (k) of the film has been optimized from 2.0/2.2 to 1.8/1.91 as-deposited and after heat treatment, by varying process parameters including power density, deposition temperature, and wall temperature. Films, failing shrinkage rate requirements, possessing promising k-values have been salvaged by utilizing a novel extended heat treatment scheme. Film properties including chemical bond structure, F/C ratio, refractive index, surface planarity, contact angle, dielectric constant, flatband voltage shift, breakdown field potential and optical energy gap have been evaluated by varying process pressure, power, substrate temperature, and flow rate ratio of processing gases. Both x-ray photoelectron spectroscopy and FTIR results confirm that the stoichiometry of the ultralow k film is close to that of CF₂ with no oxygen. C-V characteristics indicate the presence of negative charges that are either interface trapped charges or bulk charges. Average breakdown field strength was in the range of 2-8 MV/cm while optical energy gap varied between 2.2 and 3.4 eV.



Chemical vapor deposition, Fluorocarbons, Thin films, Silicon oxide films, Plasma-enhanced chemical vapor deposition

This work was partially supported by Lockheed Martin and the University of Texas at Dallas.


©2015 American Institute of Physics