A three-step copper chemical mechanical planarization model including the dissolution effects of a commercial slurry

The etching behavior of copper oxide by diluted oxidant-free slurry as a function of temperature was characterized and a three-step copper removal rate model was proposed. Pre-oxidized wafers were exposed to the diluted slurry for times up to 500 s for three temperatures and mass loss was monitored. For the highest temperature, 60 °C, all of the oxide available for reaction was etched in 90 s, however the 25 and 40 °C results did not reach saturation. Measurements up to saturation were used for modeling. A one-dimensional model was proposed where the diffusion of the complexant through a byproduct film found to exist on the wafer surface after etching controlled the process. The model fits the data well with two parameters, E_a and A, which were found to be 86.9 kJ mol^{- 1} and 4.12 × 10^{- 2} mol cm^{- 1} s^{- 1}, respectively. Similar to a previous copper oxidation study, the rate of copper consumption from dissolution was found to be a function of a characteristic reaction byproduct film thickness. However, the dissolution rates demonstrated a much weaker function of film thickness than the oxidation profiles. For this slurry, the etching process controls the combined oxidation and etching system and static oxidation-dissolution experiments agreed well with the dissolution model. The methodology and modeling developed in this work can be directly applied to other commercial or experimental slurry formulations to quantify the dissolution characteristics of the formulation. Once the static dissolution characteristics of a slurry formulation are quantified, use of the proposed three-step removal rate model will provide a more accurate depiction of the relative chemical and mechanical contributions of a given consumable set.