Method for preparing shallow trench isolation (STI)

Abstract

The invention discloses a method for preparing shallow trench isolation (STI), which comprises the followings steps of: 1, growing a substrate oxide film, a nitriding film and a top oxide film on a silicon substrate sequentially to form a hard mask layer; 2, etching the hard mask layer to the silicon substrate; 3, etching a shallow trench by a photoetching method; 4, performing lateral back etching on the nitriding film layer by taking the top oxide film layer as the mask layer; 5, peeling and cleaning the top oxide film; and 6, growing the substrate oxide film and filling a high-density plasma oxide film in the shallow trench sequentially. In the method, the top oxide film layer is added on the traditional hard mask layer, and when the nitriding film is subjected to back etching, the top oxide film layer can serve as the mask layer of the nitriding film, so that the problem of uneven height caused by the back etching of the nitriding film is solved, and a cavity is prevented from forming at the angle of the STI.

Description

technical field [0001] The invention relates to the field of semiconductor integrated circuit manufacturing, in particular to a shallow trench isolation preparation method. Background technique [0002] Shallow trench isolation (STI) is an important structure in the field of semiconductor integrated circuits. In the shallow trench isolation module, if the traditional process does not add the process of etching back the nitride film, then in the subsequent HDP filling process, there will be Two defects: 1. Voids are easily formed on the corners of STI. Due to the existence of a large number of wet etching oxide film processes in the integrated circuit manufacturing process, this cavity is easy to be continuously enlarged in subsequent processes. If there are process steps of nitride film or polysilicon growth and etching in the subsequent process, the film grown in this cavity can hardly be etched away, forming a residue; 2. It is easy to form a groove on the corner of STI (...

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Problems solved by technology

[0002] Shallow trench isolation (STI) is an important structure in the field of semiconductor integrated circuits. In the shallow trench isolation module, if the traditional process does not add the process of etching back the nitride film, then in the subsequent HDP filling process, there will be Two defects: 1. Voids are easily formed on the corners of STI

[0004] In addition, in the traditional nitride film etching process, since phosphoric acid directly contacts the silicon substrate, and the silicon substrate is often a water-repellent surface, it is difficult to remove phosphoric acid in the subsequent cleaning process, resulting in a large number of defects.

[0005] That is, the existing nitride film etching back process is unstable, resulting in the highly uneven amount of residual film of the nitride film, and there is also the problem of defects after phosphoric acid is treated on the surface of the silicon substrate.

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