Platinum chemical mechanical polishing (CMP) characteristics for high density ferroelectric memory applications

The key component of ferroelectric random access memory (FeRAM) is a capacitor including a ferroelectric thin film and electrode materials. Platinum is one of the suitable metals which meet requirements such as low resistivity, high thermal stability, and good oxygen resistance. Generally, the ferroelectric and the electrode materials were patterned by a plasma etching process. The application possibility of chemical mechanical polishing (CMP) processes to the patterning of ferroelectric thin film instead of plasma etching was investigated in our previous study for improvement of an angled sidewall which prevents the densification of FeRAM. In this study, the characteristics of platinum CMP for FeRAM applications were also investigated by an approach as bottom electrode materials of ferroelectric material in CMP patterning. The removal rate was increased from 24.81 nm/min by the only alumina slurry (0.0 wt% of H2O2 oxidizer) to 113.59 nm/min at 10.0 wt% of H2O2 oxidizer. Electrochemical study of platinum and alumina slurry with various concentrations of H2O2 was performed in order to investigate the change of the removal rate. The decreased particle size in the alumina slurry with an addition of 10.0 wt% H2O2 oxidizer made the improved surface roughness of the platinum thin films. Micro-scratches were observed in all polished samples.