Key technologies for high density FeRAM applications

Ferroelectric random access memories (FeRAMs) are new types of memory devices especially suitable for mobile applications due to their unique properties such as non-volatility, small cell size especially with chain cell design, fast read and write as well as low voltage/low power behavior. Although standard CMOS processes can be used for frontend processes, FeRAM technology development has to overcome major challenges due to new materials used for capacitor formation. In this paper the advantages and disadvantages of different ferroelectric materials, especially in terms of low thermal budget for crystallization and capacitor formation, are discussed. In addition, major development issues for high-density applications like different capacitor encapsulation concepts to protect the capacitor form backend process damage and degradation by hydrogen are presented. Results from a recently developed 1T/1C 8Mb FeRAM are discussed. The FeRAM is based on a 0.25mum CMOS process. Due to the chain cell architecture a chip size of 76mm(2) was achieved using 2 metal layers.