Improvement in Reliability of 0.25 μ m 15F² FRAM Using Novel MOCVD PZT Technology

Abstract

We report on the measurements of reliability of 0.25 μ m 15F² cell FRAM using novel MOCVD PZT technology. The MOCVD PZT capacitors were prepared using a pre-purging process and successfully integrated into the 32 Mb FRAM process with double EBL technology and optimal ILD/IMD scheme. After full integration, the 0.44 μ m² MOCVD PZT capacitors with a 2Pr value of 35 μ C/cm² at an applied voltage of 2.7 V show superior retention properties. The MOCVD PZT cells have large sensing windows of 420 mV at an operation voltage of 2.7 V. The sensing windows show only a slight decrease during 100 hours of baking at a temperature of 150°C, after which not a single cells is observed to fail. Therefore, it is clearly demonstrated that using the novel MOCVD PZT capacitors, high reliability of 0.25 μ m 15 F² cell FRAM can be achieved.

Keywords:

• FRAM
• MOCVD PZT
• reliability
• retention
• sensing window