A lead developer of Hitachi’s µ-chip explains the SOI benefits.
By using SOI, we could make an ultra-small RFID chip. In particular, its excellent isolation capability enabled successful miniaturization of the analog circuits in the front-end of the part. Also, BOX (Buried OXide) acts as an etch-stop layer in the self-controlled process, resulting in an ultimately-thin chip, which is as thin as 7.5 microns (including the multi-layered interconnection). A cross-sectional view of the ultra-thin chip is shown in the figure, where the chip is sandwiched in the antenna by using ACF (anisotropic conductive film). All of these contribute to the realization of low-cost, reliable, and widely-applicable RFIDs.