Nonvolatile memories with shaped floating gates

Abstract

In a nonvolatile memory using floating gates to store charge, individual floating gates (230) are L-shaped. Orientations of L-shaped floating gates may alternate in the bit line direction and may alsoalternate in the word line direction. L-shaped floating gates are formed by etching conductive portions using etch masks of different patterns to obtain floating gates of different orientations.

Description

technical field [0001] This application relates to non-volatile memory and methods of forming non-volatile memory. In particular, the present application relates to floating gate shaping and different arrangements of shaped floating gates in non-volatile memory. Background technique [0002] There are many commercially successful non-volatile memory products in use today, especially in the form of compact cards, which use arrays of flash EEPROM (Electrically Erasable and Programmable Read-Only Memory) cells. In one type of architecture (NAND array), a series of strings of more than two (eg, 16 or 32) memory cells are connected to each other so that the source of one is also the drain of the other to form a series of cells . Typically, each NAND string composed of, for example, 32 floating gate memory cells in series is terminated with two select transistors, one at each end of the string. The source diffusion of the drain side select transistor is the same as the drain of...