Key factors to sustain the extension of a MHM-based integration scheme to medium and high porosity PECVD low-k materials

Interconnect solutions for advanced technology nodes using PECVD techniques for low-k deposition require the use of porogen-based process with post deposition UV cure. By using two different UV cure lamps (A, B) in combination with different porogen loads, three different micro-porous low-k films are developed: Aurora® ELK HM (k~2.5; porosity (P) ~25%), Aurora® ELK A (k~2.3; P~34%) and Aurora® ELK B (k~2.2; P~37%). Integrating these materials is complex and challenging. We discuss key factors that are instrumental to the extension of a metal hard mask (MHM)-based integration scheme to these 3 low-k films. Our findings: (I) for sub-100nm dimensions, patterning and low-k interactions affect the dynamic of organic residue formation and thereby impact electrical yield; (II) choosing the right ash, etch and clean sequence is mandatory to control plasma damage, profile, residues and corrosion on top of the MHM; (III) Cu reduction plasmas must be adjusted when porosity is increased to mitigate field damage.