Trench etching method

Abstract

The invention discloses a trench etching method. The trench etching method comprises the following steps: forming a bottom hard mask layer and a top hard mask layer on the surface of a semiconductor substrate, wherein the top hard mask layer is formed by superposing a first polycrystalline semiconductor material layer, a first dielectric layer and a second polycrystalline semiconductor material layer; forming a photoresist pattern; etching for the first time to transfer the photoresist pattern into the second polycrystalline semiconductor material layer; etching for the second time to transferthe pattern structure into the first dielectric layer; etching for the third time to remove the second polycrystalline semiconductor material layer and the first polycrystalline semiconductor material layer in the opening area; etching for the fourth time to remove the hard mask layer at the bottom of the open area; and etching for the fifth time to form a trench in the semiconductor substrate. According to the invention, the thickness of the photoresist can be reduced, so that the opening width of the groove can be reduced, the opening size of the groove can be accurately controlled, and meanwhile, the thickness of the hard mask layer can be increased, so that the depth of the groove can be increased.

Description

technical field [0001] The invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a groove etching method. Background technique [0002] The depth of trenches in super junction devices or deep trench capacitive devices often reaches tens of microns, so the trenches of super junction devices or deep trench capacitive devices are usually also called deep trenches. In application scenarios such as super junction devices or deep trench capacitor devices, the etching of deep trenches is a critical and even decisive process. Deep trenches are usually formed in semiconductor substrates such as silicon substrates. Deep trenches are usually realized by etching silicon on the silicon substrate. In order to etch the silicon substrate, it is usually necessary to etch the silicon substrate A hard mask layer (HM) is formed on the surface. In the existing methods, an oxide layer (Oxide), a nitride layer (Nitride) and an oxide layer (ONO) or a ...

AI Technical Summary

Problems solved by technology

But in the deep trench etching scenario, there are many limitations

The HM of the deep trench has requirements on the shape, so its etching has a poor selection ratio for Oxide and Nitride, and Nitride is not suitable for growing too thick, so it is not applicable

[0005] The selection ratio of polysilicon (Poly) to Oxide and Nitride of HM in commonly used semiconductor films is relatively good, but the problem is that the Poly on the surface of HM cannot remain after the HM is opened, because the residual Poly will affect the trench etching atmosphere, which will lead to trench etching. Abnormal corrosion morphology

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