Novel low-k dielectrics based on DLC materials

Hydrogenated diamondlike carbon (DLC) and fluorine containing DLC (FDLC) were investigated for their potential applications as low-k dielectrics for the back end of the line (BEOL) interconnect structures in ULSI circuits. It was found that the dielectric constant (k) of DLC can be varied between <2.7 and >3.4 by changing the deposition conditions. The thermal stability of the DLC films was found to be correlated to the values of the dielectric constant, decreasing with decreasing k. Only DLC films having dielectric constants k>3.3 appeared to be stable to anneals of 4 hours at 400 degrees C in a nonoxidizing environment. However these films were characterized by stresses higher then 600 MPa. FDLC films, thermally more stable at 400 degrees C than the DLC films with k>3.3, could be prepared with dielectric constants below 2.7 and internal stresses <200 MPa. Such FDLC films are thus promising candidates as a low-k interconnect dielectric.