Effect of brush cleaning on defect generation in post copper CMP

Chemical Mechanical Polishing (CMP) has been utilized for surface topography control and planarization since it was introduced in semiconductor fabrication. However, the concept of CMP now encompasses defect control process. Post CMP in-situ cleaning has employed brush scrubber and brush scrubber is considered as highly effective method for particle removal. CMP-induced defects are well defined and easy to identify such as scratches, slurry abrasive particles, metal residue, corrosion and organic residues. Most of them are yield-detracting defects. In this paper, defect generation during the copper (Cu) CMP in-situ cleaning process is explored and the investigation focus is cross contamination by the brush cleaning process. Experiments were conducted with blanket oxide wafers and Cu pattern wafers. Brush gap, brush life, and brush cleaning time were variables for the experiments. After brush cleaning experiment, wafer surface charge characterization was performed by mercury probe method. The experiment results in this paper underscore surface charge variation during the brush cleaning process playing a critical role in defect generation. This is a new finding as to how brush cross contamination occurs during brush cleaning, and results in this paper will provide insights on defect reduction strategy in CMP process development. • Brush loading and cross contamination is source of defect generation in post CMP in-situ cleaning process. • The behavior of cross contamination of pattern wafer is different from blanket wafer. • Surface charge plays an important role in defect re-deposition. • Defect removal, defect trap in the brush (loading), re-deposit to wafer, physical force and surface charge interaction determines post brush cleaning defectivity.