Effects of various oxidizers on chemical mechanical polishing performance of nickel for microelectromechanical system applications

Nickel and nickel-based alloys are known candidates to realize movable structures for microelectromechanical system (MEMS) application. Chemical mechanical polishing (CMP) has found extensive application in the fabrication of MEMS. In this study, the CMP of nickel was performed using the commercial slurry with the various ratios of different oxidizers and alumina particle as an abrasive. Moreover, the potentiodynamic polarization behaviors were discussed to evaluate the effects of nickel-CMP performance and electrochemical characteristics between nickel and the various oxidizers. As an experimental result, the removal rate of nickel reached a maximum at 1.0 vol % of H₂O₂ concentration. An addition of 5.0 wt % alumina (Al₂O₃) abrasive could improve the removal rate of nickel; however, many scratches were observed. For the case of Fe(NO₃)₃ addition as an oxidizer, both the removal rate and the surface topography were insufficient for MEMS applications. The potentiodynamic polarization results indicated that the surface chemistry and electrochemical characteristics of nickel play an important role in controlling the polishing behavior of nickel.