A new cell structure for sub-quarter micron high density flash memory

Abstract

A new cell structure named ACT (Asymmetrical Contactless Transistor) is proposed for high density data storage applications which require low voltage, low power consumption and fast program/erase. The ACT cell with a lightly doped source and heavily doped drain realizes a simple virtual ground array using the Fowler-Nordheim (FN) tunneling mechanism for both program and erase. A self-aligned floating-gate wing technology is introduced to increase gate coupling ratio in word-line direction without sacrificing cell area. A cell area as small as 0.39 /spl mu/m/sup 2/ with a coupling ratio of 0.55 is obtained using 0.3 /spl mu/m process technology. The low programming current of the ACT cell enables multiple programming to be used and thus it is possible to achieve fast programming (<1 /spl mu/s/byte) with a low single supply voltage (<3 V). A good disturb immunity in program, erase and read modes is also obtained.