NV-SRAM: a nonvolatile SRAM with back-up ferroelectric capacitors

This paper demonstrates new circuit technologies that enable a 0.25-/spl mu/m ASIC SRAM macro to be nonvolatile with only a 17% cell area overhead (NV-SRAM: nonvolatile SRAM). New capacitor-on-metal/via-stacked-plug process technologies make it possible for a NV-SRAM cell to consist of a six-transistor ASIC SRAM cell and two back-up ferroelectric capacitors stacked over the SRAM portion. A Vdd/2 plate line architecture makes read/write fatigue virtually negligible. A 512-byte test chip has been successfully fabricated to show compatibility with ASIC technologies.