Process for making identification alphanumeric code markings for mask ROM devices

Abstract

A process for fabricating identification alphanumeric code markings on the substrate of mask ROM devices is disclosed. The fabrication process comprises first forming a deposited layer on the substrate of the mask ROM device. A photoresist layer is then formed on the deposited layer. A photomask layer by is then shaped by forming a pattern on the photoresist layer that reveals the channel regions of the memory cell transistors to be programmed into the blocking state, as well as reveals the graphical pattern of the alphanumeric code marking. An etching procedure then removes the portion of the deposited layer revealing the graphical pattern of the alphanumeric code markings. The photomask layer is then removed. A code implantation procedure may precede or follow the etching procedure to facilitate the programming of the memory cells of the mask ROM device.

Dependencies are inferred from the claim text.