Localized Corrosion of Sputtered Aluminum and Al-0.5%Cu Alloy Thin Films in Aqueous HF Solution Part II: Inhibition by CO sub 2.

In Part I, we reported the conditions under which aluminum metallizations on integrated circuits are susceptible to pitting corrosion at their edges following etching in ethylene-glycol/hydrofluoric acid solution and then rinsing. Here we investigate the CO sub 2 inhibition of this pitting corrosion on both aluminum and Al-0.5%Cu alloy thin films. Micropitting of these metallizations in dilute HF solutions is inhibited by sparging the solution with CO sub 2. DC and AC electrochemical measurements indicate that sparging results in passivation of the second-phase Al sub 2 Cu precipitates in the alloy, producing a more homogeneous, defect-free oxide film, which is also thinner than the film formed in the absence of CO sub 2.