Effect of Dissolved Oxygen on Removal of Benzotriazole from Co during a Post-Co CMP Cleaning

Abstract

A systematic study of the adsorption of benzotriazole on Co surface and its removal in aqueous solutions was carried out for post-CMP cleaning application. Static etch rate (SER) measurements and electrochemical impedance spectroscopy (EIS) were employed. The experimental results show that BTA adsorbed well on Co surface when it exposed to BTA solution at neutral and alkaline pH. BTA did not adsorb due to active Co dissolution at acidic pH. The effect of dissolved oxygen (DO) concentration in de-ionized (DI) water on the removal of Co-BTA complex layer was investigated. At DI water rinse process after BTA treatment, Co-BTA layer was maintained on Co surface when DO concentration of DI water was low. Interestingly, BTA was removed by DI water with high DO concentration.

Effect of Slurry Additives on Co-BTA Complex Stability and Inhibition Property During Co CMP Process

“…Figure 12 shows that the R p value is increased ∼6 times when the DO level changes from 10 to 2 ppm. 15,17…”

“…However, Ryu et al found that the BTA complex is not stable and can be easily removed after the DIW rinsing step. 17 The study showed that the Co-BTA complex could be formed at different cobalt surfaces, thus passivating the surfaces from corrosion. The authors also mentioned that the BTA could be easily removed from all the metallic or oxidized surfaces during the DIW rinsing.…”

“…18,19 In another study, the authors also worked on increasing the stability and passivation of the Co-BTA complex by decreasing the dissolved oxygen (DO) levels in DIW at the rinsing step. 17,20 The present study focuses on the fundamental mechanism of Co-BTA and Co oxide stability in the presence of slurry additives such as oxidizers and complexing agents. In addition, the stability of the Co-BTA complex during DIW rinsing was studied by changing the DO levels during the DIW rinse step.…”