UV surface pre-treatment and wet cleaning of Ruthenium MP18 semi-damascene structures

Abstract

Ru post dry-etch surfaces are exposed to UV irradiation and subsequent wet cleaning, to remove post etch residues. The nature of these residues, their removal efficiency and mechanisms are investigated. The post etch surface consists of native oxides of Ru and Ti along with Cl-impurities. Both UV and UV + wet cleaning processes are found to reduce the native oxide and Cl-residues, increase the hydrophilicity of the surface and improve the residue removal efficiency by improving the wetting of the small trenches (9 nm CD) in the patterned structures (18 nm metal pitch). Leakage measurements show an improvement in the leakage yield from ~30% to ~50% at a current of 1x10-11 A.