서강대학교

초록/요약

Embedded Ferroelectric Random Access Memory (FeRAM) Radio Frequency Identification (RFID) Tag Chip provides many advantages over Electrically Erasable Programmable Read Only Memory (E2PROM) counter parts. The FeRAM delivers fast write (program equivalent in E2PROM), low voltage and low power operation. Especially, the low voltage operation, down to 1.2V, will enhance the endurance, and meet 108 cycles easily. And, due to its very high unit area capacitance, the metal-ferroelectric-metal (MFM) capacitors are utilized for very large value on chip reservoir capacitors and decoupling capacitors for stable power supplies generated from the RF power. The capacitor over bitline (COB) FeRAM process allows the MFM capacitors to be layed out on top of other active circuit areas. These two features, together with the smaller memory periphery without high voltage generator, have reduced the size of RFID tag chip with encryption engine by 60%, compared with E2PROM based chip. The FeRAM write operation is ~ 103 times faster and consumes ~90% less power than the currently adopted E2PROM for RFID tag chips. The embedded 512 bit memory size facilitated extremely low power design approach, such that small 16 cells x 8 cells array granularity yielded low capacitive loading, and very low power consumption. The low power design techniques in other circuit blocks also helped the chip to provide higher energy transformation efficiency. The measurement results showed power consumption of below 10？W, operation distance of upto 7m, and the write sensitivity of -18 dBm. In simulating the memory, the capacitor model should cover the hysteretic characteristics from its remanent state to active for signal development, and polarization switching time, with a good accuracy for transient response estimation. As to internal power supply regulation function of MFM capacitors, the power ripple could be described along a local hysteresis loop. The two hysteresis loops, major one for cell operation and local one for power supplies, provide precise functioning of the chip. The characteristics changes with applied field and temperature, but there is no reasonable model available to describe all these conditions.