Method of making flash eprom with conductive sidewall spacer contacting

Abstract

Contactless flash EPROM cell and array designs, and methods for fabricating the same result in dense, segmentable flash EPROM chips. Also, an extended floating gate structure, and method for manufacturing the extended floating gate allow for higher capacitive coupling ratios in flash EPROM circuitry with very small design rules. The floating gates are extended in a symmetrical fashion in a drain-source-drain architecture, so that each pair of columns of cells has a floating gate which is extended in opposite directions from one another. This allows one to take advantage of the space on the cell normally consumed by the isolation regions, to extend the floating gates without increasing the layouts of the cells. Also, an easily scalable design is based on establishing conductive spacers on the sides of floating gate deposition layers which are used for self-alignment of the source and drain. According to this structure, a floating gate deposition is first laid down and used for establishing self-aligned source and drain diffusion regions. After deposition of the source and drain, conductive spacers are deposited on the sides of the first floating gate structure. These conductive spacers can be deposited in a symmetrical fashion, and are easily scalable to large scale arrays of flash EPROM designs.