Reliable Pzt Cmp Technology For Novel Fram Capacitors

In this paper, we report novel (TE-free) FRAM capacitors using reliable PZT CMP process in order to improve ferroelectric properties and enhance mass productivity by simplifying integration of processes. FRAM capacitors were prepared using a PZT film for a stopping layer in ILD CMP using a high selective slurry having a very low PZT removal rate relative to oxide removal rate. Noble metal electrode (TE) and contact (TEC) of conventional (TE/FE/BE) capacitors are not desirable for integration of high-density FRAM device and mass production due to contact etch damage and poor etch and deposition properties of Ir.We investigated the structural and electrical characteristics of MOCVD PZT films grown on Ir bottom electrode before and after PZT CMP process. Even though some degradation in polarization hysteresis of polished PZT capacitors was observed compared to as-deposited capacitors due to interface effect between PZT film and top electrode, electrical properties such as leakage current and fatigue were not sensitive to CMP process variables including down pressure, table speed and polishing time, indicating enough process margin in application of PZT CMP technology. In addition, PZT film roughness was dramatically reduced to result in decrease of leakage current due to the reduction of valley area. In this study, we claimed that new CMP technology with high selective slurry to PZT film was a useful approach in achieving novel FRAM capacitors by simplifying integration processes of FRAM device.