Method for manufacturing flash memory

Abstract

The invention provides a method for manufacturing a flash memory. A floating gate is formed only on the surfaces of shallow trench isolations, and is no longer across the surfaces of the shallow trench isolations and an oxide layer. In the subsequent etching of a control gate, the floating gate does not need to be etched. Therefore, the etched layer is highly uniform, etching is easy to control, damage to or residue on a semiconductor substrate is avoided, and the yield of the flash memory is improved.

Description

Technical field [0001] The present invention relates to the field of semiconductor manufacturing, in particular to a method for manufacturing a flash memory. Background technique [0002] As a major non-volatile memory, flash memory has a wide range of uses in smart cards, microcontrollers and other fields. [0003] Please refer to Figure 1a to Figure 3a with Figure 1b to Figure 3b , Figure 1a to Figure 3a Is a top view of the flash memory manufacturing process in the prior art, Figure 1b to Figure 3b for Figure 1a to Figure 3b A schematic cross-sectional view along the dotted line; the flash memory manufacturing method in the prior art includes: [0004] S1: A semiconductor substrate 10 is provided. A shallow trench isolation (STI) 20 is formed in the semiconductor substrate 10, and an oxide layer 11 is formed on the surface of the semiconductor 10, such as Figure 1a with Figure 1b Shown [0005] S2: A strip-shaped floating gate (FG) 30 is formed on the surface of the shallow tr...

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Problems solved by technology

[0008] However, in step S4, when the control gate 50, the dielectric layer 40, and the floating gate 30 located on the surface of the oxide layer 11, the surface of the entire control gate 50 is uneven, and there is only one layer of control gate 50 in some areas, therefore , the degree of etching cannot be accurately controlled during etching. If the degree of etching is insufficient (Under Etch), residues 60 are likely to be left on the surface of the oxide layer 11, such as Figure 3b As shown; if the etching degree is relatively deep (Over Etch), because the oxide layer 11 is thin, it is usually very easy to be etched away, thereby causing damage to the semiconductor substrate 10

[0009] In summary, the flash memory manufacturing method in the prior art has a narrow process window and cannot meet the needs of the process.

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