1.  Field of the Invention
This invention relates to verifying the authenticity of integrated circuits (IC's) and more specifically to recording a unique signature from an IC at manufacturing then using that signature to perform verification as necessary. 
2.  Background of the Invention
Counterfeit IC's have become a significant problem for nearly every industry that relies on electronics for data communication, data management, and data processing.  For example, the banking industry uses IC's for security purposes that need to be safe from counterfeiting; government programs, such as defense, have a high security requirement on circuitry to prevent technology from falling into adverse possession; and high volume consumer electronics with large profit margins are subject to counterfeiting such as gaming boxes, routers, and cellular telephones. 
Some counterfeit IC's have additional logic which secretly routes data from the IC to adverse persons such as hackers and snoopers who can obtain secure information such as credit card numbers, account numbers, and passwords from the IC's. 
Counterfeiters typically reverse engineer an existing IC by processes such as delamination or delayering.  The authentic IC is delayered one layer at a time and the circuit configuration of that particular layer is copied as a new schematic layout which can be used for manufacturing the counterfeit IC.  Other reverse engineering techniques include the use of scanning electron microscopes (SEM's) and backside imaging which requires that the chip be polished very thinly so that the photon emission from electrons can be seen through the substrate and recorded.