Circuit for encoding identification information on circuit dice using

Abstract

A programmable circuit for inclusion in an integrated circuit die for encoding information identifying or otherwise relating to such die, such circuit utilizing a plurality of single bit information storage and reading bit cells, each bit cell including a MOSFET or IGFET capacitor structure as a bit storage element. A gate of the MOSFET or IGFET acts as a positive voltage plate of the capacitor, while a source and drain are both connected to ground and act as ground plates of the capacitor. Normally, an open circuit is present between the gate and the source and drain, however, when a programming high voltage is applied to the gate, the capacitor structure physically breaks down and a conduction path is formed between the gate and the source or drain. The presence or absence of this conduction path enables the MOSFET or IGFET capacitor structure to act as a binary bit. Read circuitry selectively senses the presence or absence of the conduction path of each bit cell, and a multiplexer can be employed to connect the read circuitry to the successive bit cells sequentially. Protection circuitry is provided to prevent the read circuitry from being damaged by the applied programming voltage. The programmable circuit can be fabricated by the same integrated circuit fabrication techniques used to fabricate the remaining circuits on the die.