Effects of oxidizing agent and hydrodynamic condition on copper dissolution in chemical mechanical polishing electrolytes

摘要

The effects of H_2O_2 and Fe(NO_3)_3 on the electrochemical behavior, dissolution rate and surface characteristics of Cu in static and under rotating conditions were investigated. Rotating cylinder electrodes were used for potentiodynamic polarization curves measurements in 0.0078 M citric acid (CA) base electrolytes with various concentration of H_2O_2 (0-12 vol.%) and Fe(NO_3)_3 (0-0.2 M). The rotating speed was varied in the range of 0-3000 rpm. The dissolution rates of Cu were determined using Tafel extrapolation, inductively coupled plasma-mass spectrometry (ICP) solution analysis, and weight loss measurements, depending on the electrolytes involved. The surfaces of specimens after immersion in the electrolytes for a certain period of time were characterized with Auger electron spectroscopy (AES), X-ray photo-electron spectroscopy (XPS), and atomic force microscopy (AFM). The experimental results showed that H_2O_2 with sufficient concentration could promote passivation of Cu in the CA base electrolyte, which was confirmed by AES and XPS. The addition of Fe(NO_3)_3 into the CA base electrolyte did not cause the formation of passive film and its presence enhanced the dissolution rate of Cu. In both H_2O_2 and Fe(NO_3)_3 containing electrolyte, the dissolution rates increased with increasing electrode rotating speed.