Effect of surfactant on package substrate in chemical mechanical planarization

Abstract

The demand for pattern miniaturization on package substrates has been steadily increasing. One technical innovation for the package substrate manufacturing process was chemical mechanical planarization (CMP). In conventional wiring, it was possible to remove extraneous copper through only the etching process. However, etching defects occur with narrower line widths. As the package substrate has a Cu hybrid structure through Cu plating and copper clad laminate (CCL) removal, it is necessary to apply the CMP to remove excess copper. However, defects are generated by the CMP process due to mechanical and chemical effects from the slurry. This study investigated the surfactant effect on Cu dishing and erosion in patterns with approximately 10/10 µm line width and spacing. The conventional Cu slurry without a surfactant had severe erosion (0.58 µm) in Cu patterns of 4/6 µm and deep dishing (4.2 µm) in Cu patterns of 14/16 µm. However, the experimental results showed that the friction force during CMP decreased, with smaller dishing and erosion as surfactant concentration increased. Finally, globally planarized Cu patterns were realized with an erosion range of 0.22 µm to 0.35 µm and a dishing range of 0.37 µm to 0.69 µm with 3 wt.% surfactant.