Method for forming floating gate

Abstract

The present invention provides a method of forming a floating gate. The method includes the following steps that: a substrate is provided, the substrate includes a memory region and a peripheral circuit region, wherein the storage region and the peripheral circuit region each include an isolation structure; a polysilicon layer is formed on the substrate, wherein the polysilicon layer covers the storage region and the peripheral circuit region; chemical mechanical polishing is performed on the polysilicon layer, so that a part of the polysilicon layer can be left on the isolation structure of the peripheral circuit region; and back-etching is performed on the polysilicon layer and the isolation structure until a part of polysilicon layer of a certain thickness can be left. According to themethod of the invention, the uniformity of the polysilicon layer of the storage region and the peripheral circuit region after chemical mechanical polishing is performed can be improved, and the performance and yield of the product can be improved.

Description

technical field [0001] The invention relates to the technical field of semiconductor manufacturing, in particular to a method for forming a floating gate. Background technique [0002] In recent years, among storage devices of semiconductor integrated circuits, the development of flash memory is particularly rapid. The main feature of flash memory is that it can keep stored information for a long time without power on, and has the advantages of high integration, fast access speed, easy erasing and rewriting, etc., so it has been widely used in many fields such as microcomputer and automatic control a wide range of applications. A typical flash memory uses doped polysilicon to make a floating gate (Floating Gate) and a control gate (Control Gate). The floating gate is used to store data, and the control gate is connected to a word line to control the floating gate. [0003] In the existing flash memory process, the floating gate is formed by chemical mechanical polishing af...

AI Technical Summary

Problems solved by technology

However, due to the difference in grinding rate in different regions, there will be a step difference in the remaining polysilicon thickness in the storage area and the peripheral circuit area. It is easy to cause damage to the silicon in the active area during removal, which will cause the device to fail to open normally, and even cause the device to fail

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