In situ ellipsometry of Cu surfaces immersed in benzotriazole–hydrogen peroxide solutions

Abstract

In the chemical mechanical polishing (CMP) of Cu, the Cu surface is oxidized and is concurrently removed by the mechanical function of an abrasive. Surface oxidation can lead to severe surface corrosion, and to prevent this, a corrosion inhibitor is added to slurries. Accurate understanding of the competition between oxidation and passivation is essential for advanced Cu CMP technologies. In this work, layer formation on clean Cu surfaces in benzotriazole (BTA), H2O2, and BTA–H2O2 aqueous solutions was studied by in situ spectroscopic ellipsometry. Time changes of ellipsometric parameters are discussed with respect to BTA and H2O2 concentrations. It was found that the BTA adsorbs onto the Cu surface and the adsorbed BTA transforms into a Cu–BTA complex in about 3 min after the onset of adsorption. The BTA/complex layer passivates the Cu surface against oxidation by H2O2.

Structures of Cu surfaces developing in benzotriazole solutions: Effect of pH

“…Such changes in Ψ and Δ correspond to the change in the Cu surface, which involves the formation of an adsorption layer and=or oxide, as we have shown in our previous work. 23) In ellipsometry, the refractive index or thickness of the film cannot be determined from Ψ and Δ analytically. A thin film structure stacked on a substrate is modeled, its Ψ and Δ values are calculated numerically, and the numerical results are compared with the actual data to determine the film structure and optical properties of the stack.…”

“…After the citric acid treatment, Ψ decreased to 44.41 ± 0.013 and Δ decreased to 112.09 ± 0.154 owing to the removal of the native oxide layer. 23) The specimen was then placed in an optical cell filled with 20 cm 3 of an aqueous BTA or an aqueous BTA-H 2 O 2 solution. The concentration of BTA was fixed at 0.001, 0.01, or 0.1 M. The concentration of H 2 O 2 was fixed at 0.089, 0.89, or 8.9 M; the concentrations were nominal values calculated from the reagent composition.…”

“…16,[20][21][22] In a previous study, we carried out in situ ellipsometry of the surface layers formed on Cu in BTA-H 2 O 2 solutions so as to clarify the physical structures and thicknesses of the layers. 23) The dependences of BTA and H 2 O 2 concentrations were our previous concern and the pH of the solutions was not adjusted intentionally. In this work, the effect of pH was studied.…”

Thin layer growth on cobalt surface in solutions simulating slurry chemistry for chemical mechanical polishing

“…We have studied the growth of a passivation layer on Cu in aqueous solutions of a corrosion inhibitor and an oxidizer using spectroscopic ellipsometry, [18][19][20] where benzotriazole (C 6 H 4 N 3 H, CAS 95-14-7) was used as a corrosion inhibitor and hydrogen peroxide was used as an oxidizer. Ellipsometry is a powerful tool to enable fast and real-time measurements of films on a specimen surface in a liquid and allows us to determine the physical structures and properties of the film.…”

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

“…BTA has been widely used for copper corrosion inhibition due to its better absorption and inhibition properties. 15,16 Similarly, adsorption of BTA and its complex formation has been investigated on cobalt surfaces and found to be better at neutral and slightly alkaline pH conditions. However, Ryu et al found that the BTA complex is not stable and can be easily removed after the DIW rinsing step.…”