Preparation method of shallow trench isolation structure

Abstract

The invention discloses a preparation method of a shallow trench isolation structure, which comprises the following steps: forming a scalar silicon nitride appearance used as a mask for etching a shallow trench through three etching technologies, and realizing that a top angle is smoothed to prepare smoother silicon and silicon oxide interfaces by utilizing thinner silicon oxide with a poorer oxidation shielding property when the inner surface of a shallow trench is subsequently oxidized.

Description

technical field [0001] The invention relates to a method for preparing a shallow trench isolation structure in semiconductor manufacturing. Background technique [0002] Shallow trench isolation (STI) is a relatively common isolation technology in semiconductor manufacturing, which mainly uses deposited silicon dioxide to backfill etched trenches to form isolation oxide regions. The preparation process of conventional shallow trench isolation structure (see Figure 1 to Figure 6 )for: [0003] 1) Deposit silicon oxide and silicon nitride sequentially on the silicon substrate; [0004] 2) Perform photolithography and development of shallow trenches, post-etch to form shallow trenches, and perform cleaning after etching (see image 3 ); [0005] 3) Oxidation treatment of the inner surface of the shallow trench forms a pad oxide layer (see Figure 4 ); [0006] 4) High-density plasma silicon oxide fills shallow trenches (see Figure 5 ); [0007] 5) planarization to form...

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Problems solved by technology

[0008] Using the above-mentioned traditional preparation method, since the upper surface of the shallow trench is covered by silicon nitride, and the side is exposed, when the pad is oxidized, the side is oxidized quickly, and the surface is oxidized slowly. The biggest difference in oxidation speed is at Figure 4 At the middle sharp corner, it is easy to cause the silicon surface to be sharper after oxidation, resulting in the thinning of gate oxide and the concentration of electric field.

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