Metal barrier induced damage in self-assembly based organosilica low-k dielectrics and its reduction by organic template residues

This study describes the damage caused by physical vapor deposition of TaN/Ta barriers on porous self-assembled organosilica low-k dielectrics for IC applications. It is demonstrated that the ion bombardment associated with TaN layer sputtering strongly influences the metal species in-diffusion and modifies the bulk dielectric and pore sealing characteristics. The modulation of the pore structure via controlled decomposition of the organic template, prior to the barrier deposition step, allows to mitigate this damage. The reduction of open porosity, from nominal 39% down to 26%, is realized by partial retention of the sacrificial organic porogen phase in the pores of the low-k dielectric, resulting in the suppression of deep Ta penetration and in the recovery of pore sealing. This approach is successfully tested in a 45 nm half-pitch damascene vehicle. The compatibility of the organic template residues with the subsequent steps of the interconnects integration process flow, such as hard-mask deposition and patterning, are discussed.