Are There Any Limitations in Terms of Minimizing an RFID Tag?

Is a chip in nanometer scale conceivable?

—Thanks, Toralf

———

Toralf,

RFID transponders usually contain a microchip and an antenna (there are also chipless RFID systems, but I am not sure those would be relevant in this scenario). There are two issues related to shrinking a transponder's size that you need to consider. The first is that the chip can only be reduced so much in size and still maintain circuitry. Hitachi has been able to reduce its chip to 0.15 millimeter (0.006 inch) square (see Hitachi Shrinks Smallest RFID Chip). That's pretty tiny. It might be possible to reduce chip size even further, but at some point, you would not be able to decrease size and still etch all of the necessary circuits into the silicon.

Another issue is the size of the antenna. Passive tags harvest energy emitted by a reader. This is stored briefly on the chip, and is used to power the circuitry and reflect back a signal to the reader antenna. The smaller you shrink the antenna, the less power it can harvest, so the read range becomes increasingly shorter. Hitachi's µ-chip (pronounced "mu-chip") uses an antenna etched into silicon, so it is as small as the chip, with no external antenna (see Hitachi Unveils Smallest RFID Chip and Hitachi Unveils Integrated RFID Tag). This keeps the device very small, but limits the read range to just a few millimeters. So as you shrink the antenna, you transform the tag into something that almost has to be touched by the reader antenna to be interrogated—and, of course, if the chip is microscopic, it is difficult to touch since you cannot see it.

So while nanoscale chips are conceivable, I do not think they would be very practical, except perhaps for anti-counterfeiting. One use for the µ-chip is the anti-counterfeiting of paper, including possibly money (see When Will RFID-Embedded Paper Be Available?). You could embed a nanoscale chip in paper and place that paper on a reader antenna to confirm its authenticity. But it would not be useful for inventory management.

—Mark Roberti, Founder and Editor, RFID Journal