Low Cost Writable RFID Tag with MRAM Memory

The objective of this work was to show proof of concept for a writable RFID tag that used an integrated antenna and MRAM nonvolatile memory to store data. Circuit designs for the reader/writer unit and the the tag IC were completed during the work, and showed that the design concept was feasible. MRAM memory cells specifically designed for this low energy application were constructed and tested, and are clearly suitable for use in this application. These memory cells offer bipolar signals for easier sensing during the read cycle, and are denser than the ROMs normally used in read-only RFID tags, leading to a lower IC cost. Four different integrated antennas, using two IC processes developed specifically for this work, were constructed during the course of the program. The processes were developed to be used on top of existing circuitry, so the antennas would pose no area penalty on the IC. Problems with the new processes prevented successful fabrication of any of the antenna designs; however, extensive failure analysis was performed on the completed parts, and the processing problems have been conclusively identified. Good parts are expected with a mask modification and several minor process modifications. NVE considers the program a major success, and will submit a Phase II proposal.