Improved wet etching method for selectively removing silicon nitride

Abstract

The invention provides an improved wet etching method for selectively removing silicon nitride, and relates to the technical field of semiconductors, and the method comprises the steps: S1, providing a wafer, and enabling a silicon nitride layer and a silicon oxide layer to grow on the upper surface of the wafer; s2, providing a phosphoric acid mixed solution, and heating the phosphoric acid mixed solution to a preset temperature; and S3, spraying the phosphoric acid mixed solution to the upper surface of the wafer, and performing wet etching on the upper surface of the wafer so as to remove the silicon nitride layer and reserve the silicon oxide layer at the same time. The method has the beneficial effects that phosphoric acid and ultrapure water are mixed to form a phosphoric acid mixed solution, the phosphoric acid mixed solution is heated to form a high-temperature phosphoric acid mixed solution, and selective cleaning and etching are performed by adopting a spraying mode, so that high selectivity is realized, impurity accumulation of the phosphoric acid mixed solution and cross infection of wafers are effectively avoided, and the quality of a prepared product is effectively improved.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to an improved wet etching method for selectively removing silicon nitride. Background technique [0002] The surface sacrificial layer technology refers to that in the process of forming the cavity of the micromechanical structure or the movable microstructure, first deposit various special structural parts required by structural materials on the underlying film, and then use chemical etchant to deposit the required special structures. The first layer of thin film is etched away, but the microstructure is not damaged, and then the upper thin film structure (cavity or microstructure) is obtained. Since the removed lower film only acts as a separation layer, it is called a sacrificial layer (thickness about 1-2 μm). In semiconductor devices, silicon nitride is often used as a sacrificial layer and is formed adjacent to or close to the silicon oxide layer. [0003] Existing m...

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Problems solved by technology

Among them, reactive ion etching can be used for dry etching, however, reactive ion etching for silicon nitride lacks high selectivity to silicon oxide layer and will degrade silicon oxide layer or silicon substrate in the form of surface pitting; wet etching usually Etching is carried out in an acid bath, that is, the si

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