EFFECT OF BENZOTRIAZOLE ON THE ANISOTROPIC ELECTROLYTIC ETCHING OF COPPER

Electrolytic etching of copper foil at the base of cavities formed by patterned photoresist was investigated in 0.5 M: sulfuric acid solutio ns which either contained 40 mM benzotriazole (BTA) or were free of BT A. It was found that undercutting (metal dissolution beneath the photo resist) was minimized by the action of surface films in both solutions . It was also found that the nature of the surface films and the mecha nism by which they enhanced etch anisotropy differed. In additive-free solutions, anisotropic etching was observed under conditions of appli ed potential and flow for which mass transfer was suppressed in the in terior corner regions of cavities. Such operating conditions in additi ve-free solutions displayed characteristic current transients. In BTA- containing solutions, the etch profiles were highly dependent on appli ed potential. In contrast to the additive-free solutions, the flow con ditions in BTA-containing solutions had Little effect on the current t ransients or on the degree of undercutting within the region of applie d potential in which anisotropic etching was achievable.