Flash memory and preparation method thereof

Abstract

The invention relates to a flash memory and a preparation method thereof. A manufacture method comprises that follow steps of: forming a floating gate oxide layer, a floating gate polycrystalline layand a barrier layer on a semiconductor substrate in sequence; etching the barrier layer in turn, and forming a window on the floating gate polycrystalline layer, and the extending the window into thefloating gate polycrystalline layer; exposing the floating gate polycrystalline layer in the window region so that the floating gate polycrystalline layer is depressed in the direction of the floating gate oxide layer, and the depth of the depressions decreases from the center position of the window region to the edges of both sides; Forming a first field oxide layer and filling a window locatedin the floating gate polycrystalline layer; Etching to form a floating gate with a discharge tip. The method pretreats the floating gate polycrystalline layer exposed in the window region, so that thethickness of the exposed floating gate polycrystalline layer is low in the middle position and high in the edge positions on both sides, the subsequent floating gate polycrystalline layer is oxidizedto form a field oxide layer, and the discharge sharp angle formed by etching is sharper than that formed by the traditional method.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a flash memory and a preparation method thereof. Background technique [0002] The heating and erasing mechanism of the flash memory is realized by applying a high voltage on the select gate and tunneling (Fowler Nordheim, FN). When the tip of the floating gate is sharper, the electric field is larger, the barrier width is smaller, and the electrons are easier to tunnel. The erase performance of flash memory is better. [0003] In the traditional process of manufacturing a floating gate, an oxidation window is etched into the mask layer of the floating gate, and the depth of the oxidation window is slightly greater than the thickness of the mask layer of the floating gate. At the oxidation window, the floating gate polycrystalline layer is oxidized to form a silicon dioxide layer. Since the floating gate polycrystalline layer at the oxidation window is a plane, during th...

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Problems solved by technology

[0004] Based on this, it is necessary to provide a flash memory with sharp discharge corners and good erasing performance and a preparation method thereof for the blunt discharge corner of the floating gate.

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