Polyvinyl acetal (PVA) brush cleaning is one of the most important processes in the post chemical mechanical planarization (CMP) cleaning process. However, PVA brush could be severely contaminated due to strong direct contact with a large amount of abrasive particles during the long-time post CMP cleaning, and the particles on the brush can be easily transported to the next wafer substrate. In this study, we tested four different types of conditioning processes to remove the particles from the brush to increase the cleaning efficiency of post CMP process and comparatively evaluated using FE-SEM. The physical scrubbing method showed higher cleaning efficiency than the chemically dipping method, but some abrasive particles remained on the non-contacted surface. The flow-through method using pH 11 showed the higher removal ability than pH 3 and 7 due to strong repulsive force between silica abrasive particle and PVA brush, but some abrasive particles remained due to non-uniform flow of chemicals. The ultrasonication method with DIW was found to be very effective to remove the particles completely from the brush without damage. Consequently, the new developed conditioning process provides an environmentally friendly and cost effective alternative conditioning process to the existing conditioning process of contaminated PVA brushes.

Corrosion inhibitors play a key role in obtaining global planarization and protecting against corrosion during copper CMP. However, these inhibitors leave organic residues and increase particle contamination after the CMP process, which can directly affect the device yield. Cu CMP is usually performed with a slurry containing silica particles and a BTA corrosion inhibitor. High levels of organic defects and particle contamination are produced due to the high concentration of BTA used to meet CMP requirements. In this work a suitable corrosion inhibitor, 5-methyl-benzotriazole (MBTA), is proposed and used at an optimized concentration to remove organic residues and particle contamination effectively during the post-CMP process. The optimum inhibitor concentration was estimated for BTA and MBTA. Based on etching and EIS studies, it was found that a lower concentration of MBTA (relative to BTA) is needed to provide the conditions required for CMP. The passivation layer formed by MBTA can be removed easily during the post-CMP process. Thus, our results indicate that it is possible to reduce the concentration of the inhibitor while maintaining the same corrosion inhibition efficiency, thereby reducing the particle and organic defect levels.

Different cobalt surfaces (as-received, metallic, and oxidized Co) were characterized by contact angle measurements, FTIR (Fourier-transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy) and EIS (electrochemical impedance spectroscopy) to investigate the interaction of these surfaces with benzotriazole (BTA). A new sequential EIS technique was used to study the inhibition capabilities of BTA on the cobalt surface and its stability under de-ionized (DI) water rinsing. It was found that a Co-BTA complex passive layer was formed when exposed to a BTA solution for all types of Co surfaces. It was hypothesized that BTA could actively form a Co-BTA complex on metallic Co as well as on the Co oxide surface. Interestingly, most Co-BTA complexes could be easily removed by simply rinsing with DI water, which indicates that BTA might not produce an organic residue issue after the chemical mechanical planarization (CMP) process. This was also well supported by potentiodynamic studies.