Shape evolution of electrodeposited bumps with additive

Bumps with anisotropic conductive film are promising interconnections for m icroelectronics. The bumps having humps on their surroundings decreases the interconnection resistivity, since a greater number of conductive particle s in the anisotropic conductive film can be trapped. The anodic current density-voltage curves show the increase of i(0) and alp ha(c) by adding selenic acid. The bump has flat shape without the selenic a cid. However, the bump surroundings have humps and the hump height becomes larger with selenic acid of 200 and 1000 g/m(3). The hump heights at the su rroundings decreases along with the decrease in current density of 1734, 60 0 and 350 A/m(2). The bump center height increases and the surrounding hump heights decrease with the decrease of cathode diameter. These changes in b ump shapes corresponds well with the numerical analysis of current density in two dimensions. The additive of selenic acid increase i(0) and alpha(c) and hence decrease the charge transfer resistance. The ohmic resistance becomes larger than th e charge transfer resistance, This converts the secondary to the primary cu rrent distributions and causes the bumps with humps in their surroundings. (C) 1999 Elsevier Science Ltd. All rights reserved.