Alternate metal virtual ground EPROM array implemented in a 0.8 mu m process for very high density applications

The alternate metal virtual ground EPROM array (AMG) is introduced as a new scaling concept. This array dramatically reduces cell size by making poly pitch the only limitation in both X and Y directions. The AMG concept scales cell size by sharing one metal line per two diffusion bit lines and relies on a segmentation scheme and fieldless array to achieve the poly pitch limited cell. The cell size in 0.8- mu m technology is 2.56 mu m/sup 2/, which is considerably smaller than the standard EPROM cell in 0.6- mu m technology. A major advantage of this array is reduction of drain turn-on induced punch-through. This reduction allows scaling of effective channel length to as low as 0.25 mu m, resulting in high read current and fast programming time.<
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