the dispersion 31 a drying step is performed to remove the solvent or liquid in the via 30 the drying step may be conducted at a temperature between about 30 u00b0 c and about 100 u00b0 c in air vacuum or inert gas after the drying step copper particles 32 settle down and partially fill the via 30 as shown in fig3 b subsequent application or applications of the dispersion followed by drying step s in a cyclical process eventually results in complete filling of the via 30 with copper particles 32 as shown in fig3 c in the illustrated embodiment no copper is shown on the top surface or field regions 33 in fig3 c while there may actually be some copper particles remaining on the top surface 33 preferably substantially all of the copper particles are within the vias 30 or other features preferably 2 to 4 cycles can be performed depending on the size of a feature to be filled the size of nanoparticles and the weight ratio of nanoparticles 32 in the dispersion 31 there may also be annealing see next section performed between or part of the deposition cycles after the deposition step s the feature s filled with copper particles is subjected to an annealing or densification step at which the copper particles are fused together thereby forming a substantially dense copper plug 60 as shown it should be noted that the density of the copper plug may be controlled by choosing the shape and size of the particles in the dispersion while spherical particles or flat particles in the form of plates may yield high density particles with random shapes and forms yield lower density mixing relatively large particles.