Growth kinetics of Cu surface layers in H₂O₂–BTA aqueous solutions

Abstract

Slurries for the chemical mechanical polishing of Cu contain both an oxidizer and a corrosion inhibitor, in addition to abrasives. To understand the chemistry of the Cu surface exposed to slurries, Cu surfaces in benzotriazole (BTA)–hydrogen peroxide (H2O2) aqueous solutions were studied using in situ spectroscopic ellipsometry. A microfluidic optical cell was used so that processing solutions could be changed during in situ observations and the initial surface processes could be successfully observed. A thin surface layer was observed to grow on Cu in the solutions. The growth rate of surface layers on Cu was inversely proportional to the thickness of the growing layer, and the growth then stopped in a self-limiting manner. The growth mechanism is discussed in view of Cu out-diffusion.

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

“…In contrast, in the case copper, this decrease was much faster and the continuous layer thickening was not observed. 20) In order to determine the physicochemical nature of the layer, we employed Ψ-Δ trajectory analysis. 19,20,23) In this analysis, the experimental sets of Ψ and Δ at 633 nm are plotted and are compared with those calculated for various thicknesses and complex refractive indices.…”

“…20) In order to determine the physicochemical nature of the layer, we employed Ψ-Δ trajectory analysis. 19,20,23) In this analysis, the experimental sets of Ψ and Δ at 633 nm are plotted and are compared with those calculated for various thicknesses and complex refractive indices. Before doing this, the refractive index of our clean cobalt surface must be determined; this was carried out using the Ψ and Δ at 408 s ("before solution supply") and the determined value at 633 nm was 2.53 + 4.31i which was in a proper agreement with a reported value.…”

“…The details of the microfluidic cell was described in our previous paper. 20,21) The ellipsometer used is a JA Woollam RC2 dual rotating compensator ellipsometer. The spectra of wavelengths in the range of 200-1000 nm were acquired approximately every second on average and those in the range of 400-1000 nm were used for in situ analyses.…”

“…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.…”

“…This arrangement allows one to study the kinetics of the film growth which is not easily carried out in other techniques. In the previous paper, 20) we reported on the growth kinetics of a passivation layer on Cu surface layers in BTA-H 2 O 2 aqueous solutions. In this paper, we report the film growth on a Co surface in BTA-H 2 O 2 aqueous solutions.…”