CMOS ROM arrays programmable by laser beam scanning

A CMOS PROM array with a novel programming method has been developed. Memory cells consist of two n-channel transistors and a p-n junction diode which is built by a p-moat in an n-well. Programming is accomplished by scanning green laser beams in diodes to decrease minority-carrier lifetime, without disturbing passivation after the fabrication is complete. This innovation has application where post-fabrication personalization of circuits is desirable. Also, the memory contents are not easily discovered through visual inspection or reverse engineering.