A 60-ns 1-Mb nonvolatile ferroelectric memory with a nondriven cell plate line write/read scheme

This paper proposes three circuit technologies For achieving mega-bit-class nonvolatile ferroelectric RAM's (NVFRAM's). The proposed nondriven cell plate line write/read scheme (NDP scheme) accomplishes fast write/read operation equivalent to that of DRAM's. Problems and countermeasures in introducing this scheme into NVFRAM's are also discussed. A proposed optimized C_B/C_S cell array design method provides a relationship between bit line capacitance C_B and memory cell capacitance C_S, which must be satisfied for read operations. Also reported is a reference voltage generator circuit that uses a dummy memory cell. This circuit can generate an accurate reference voltage despite the variety of capacitors with differing characteristics that are contained in the NVFRAM. A 1-Mb NVFRAM prototype featuring the above technologies has been fabricated, using a 1.0-μm CMOS process. This chip has an access time of 60 ns and a die size of 15.7 × 5.79 mm².