Method and structures are provided for conformal lining of dual damascene structures in integrated circuits, and particularly of openings formed in porous materials. Trenches and contact vias are formed in insulating layers. The pores on the sidewalls of the trenches and vias are blocked, and then the structure is exposed to alternating chemistries to form monolayers of a desired lining material. In exemplary process flows chemical or physical vapor deposition (CVD or PVD) of a sealing layer blocks the pores due to imperfect conformality, and is followed by an atomic layer deposition (ALD), particularly alternately pulsed metal halide and ammonia gases injected into a constant carrier flow. An alternating process can also be arranged to function in CVD-mode within pores of the insulator, since the reactants do not easily purge from the pores between pulses. Self-terminated metal layers are thus reacted with nitrogen. Near perfect step coverage allows minimal thickness for a diffusion barrier function, thereby maximizing the volume of a subsequent filling metal for any given trench and via dimensions.