No abstract

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.

In the chemical mechanical polishing (CMP) of Cu, the Cu surface is oxidized and is concurrently removed by the mechanical function of an abrasive. Surface oxidation can lead to severe surface corrosion, and to prevent this, a corrosion inhibitor is added to slurries. Accurate understanding of the competition between oxidation and passivation is essential for advanced Cu CMP technologies. In this work, layer formation on clean Cu surfaces in benzotriazole (BTA), H2O2, and BTA–H2O2 aqueous solutions was studied by in situ spectroscopic ellipsometry. Time changes of ellipsometric parameters are discussed with respect to BTA and H2O2 concentrations. It was found that the BTA adsorbs onto the Cu surface and the adsorbed BTA transforms into a Cu–BTA complex in about 3 min after the onset of adsorption. The BTA/complex layer passivates the Cu surface against oxidation by H2O2.

PVA brush scrubbing techniques are widely used in cleaning processes for semiconductor device manufacturing. These cleaning processes are typically monitored by measuring the forces or torques generated during PVA brush scrubbing. In this paper, we discuss whether these measured parameters reflect the real contact conditions during scrubbing. We measured the shear forces generated by brush sliding. The shear forces were strongly correlated with brush deformation. In addition, brush rotation greatly suppressed brush deformation and shear force. This result indicates that a portion of the shear force was generated by brush deformation and not contact conditions. We also measured the torque generated by the PVA brush rotation on a surface. We concluded that these types of measurements, which reduced brush deformations, were suitable for evaluating contact conditions.