Preparation method of flash memory device

Abstract

The invention provides a preparation method of a flash memory device. The preparation method comprises the following steps: providing a substrate, a floating gate polycrystalline silicon layer and a first silicon nitride layer which are stacked, and forming a groove on the substrate; forming an OON layer and a barrier layer; depositing a tungsten layer in the groove; performing an etching-back process on the tungsten layer; and executing at least N rounds of tungsten deposition process and tungsten back etching process so as to obtain a tungsten source line with the Nth thickness in the groove, wherein N is an integer greater than or equal to 1. The traditional CMP process does not need to be executed between the first deposition process and the first back etching process, and at least N turns of tungsten deposition process and tungsten back etching process are continuously executed for the groove after the first back etching process to obtain the final tungsten source line. The situation that the second silicon oxide layer in the OON layer on the first silicon nitride layer around the groove is removed by mistake through grinding due to the CMP technology is avoided, and meanwhile the uniformity of the thickness of the tungsten source line in the groove is improved.

Description

technical field [0001] The invention relates to the technical field of flash memory device manufacturing, in particular to a preparation method of a flash memory device. Background technique [0002] In the current semiconductor industry, Super Flash (Super Flash) technology, as a mainstream storage technology, has developed rapidly in recent years. High, ultra-fast access speed and easy to erase and many other advantages, so it has been widely used in many fields such as microcomputers and automatic control. [0003] In Super Flash, its source line structure generally includes a substrate, a floating gate polysilicon layer, a silicon nitride layer, and a silicon oxide layer, wherein the floating gate polysilicon layer, silicon nitride layer, and silicon oxide layer are formed with trenches, OON sidewalls and barrier layers are formed on the sidewalls of the trenches. When preparing the tungsten source line, tungsten metal is first deposited in the trench, and then the sur...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a method for preparing a flash memory device, so as to solve the problem that the silicon oxide layer around the top of the groove where the tungsten source line is deposited is easily misground when preparing the tungsten source line of the flash memory device

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