Method for making peripheral circuit device grid in flash memory

Abstract

The invention provides a method for making a peripheral circuit device grid in a flash memory, comprising the following steps: providing a semi-conductor substrate, wherein the semi-conductor substrate comprises a storage unit area and a peripheral circuit area; etching a shallow trench isolation structure of the storage unit area; etching a floating-gate polysilicon layer to form a floating gate and further form a stack grid for the flash memory; growing a first polysilicon layer; growing a medium layer; growing a second polysilicon layer; polishing the second polysilicon layer; removing the exposed medium layer; forming the grid of the peripheral circuit area by an etching process; and etching the surface of the shallow trench isolation structure in the peripheral circuit area before growing the first polysilicon layer. The invention has the advantage that using an etching method reduces the height difference between the oxide surface of the shallow trench isolation structure and the silicon active area of an adjacent area within the range of over-corrosion depth of a polishing process, and ensures to obtain the complete grid in a subsequent process.

Description

【Technical field】 [0001] The invention relates to the field of integrated circuit manufacturing, in particular to a method for making gates of peripheral circuit devices in flash memory. 【Background technique】 [0002] Flash memory is a common integrated circuit storage device, which belongs to a non-volatile memory and is widely used in various occasions. The characteristic of non-volatile memory is that when the working voltage disappears, the memory can still save data for a long time without loss. [0003] Split-gate (Split-Gate) flash memory and stack-gate flash memory devices are two common flash memory devices. Compared with stacked gate flash memory devices, split gate flash memory has the advantages of small size and low power consumption. Regarding the manufacturing method of the split-gate flash memory, reference may be made to the content described in US Pat. No. 6,538,277. A typical flash memory chip includes memory cells and peripheral circuits. The devices...

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Problems solved by technology

[0016] As can be seen from the above description, due to the remaining second dielectric layer in the prior art, the polysilicon layer cannot be etched through during the process of etching the gate, so a complete gate cannot be obtained.

Obviously, with Figure 11 The device gate of the shown peripheral circuit cannot perform its electrical function in the subsequent process, which will directly lead to the failure of the flash memory device

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