Method for forming shallow trench isolation structure

Abstract

The invention provides a method for forming a shallow trench isolation structure, comprising the following steps: providing a substrate, wherein a pad oxide layer and a silicon nitride layer are sequentially formed on the substrate, and openings exposing the substrate are formed in the pad oxide layer and the silicon nitride layer; forming shallow trenches on the substrate along the openings; forming a protective oxide layer covering the surfaces of the shallow trenches; forming a first oxide layer covering the protective oxide layer and filling the shallow trenches; back-etching the first oxide layer; forming a supplementary oxide layer covering part of the protective oxide layer; forming a second oxide layer covering the protective oxide layer and the supplementary oxide layer; flattening the first oxide layer, the second oxide layer and the protective oxide layer until the silicon nitride layer is exposed; and removing the silicon nitride layer. The method can avoid the change of electrical properties of devices caused by damage of silicon oxide on the top of side walls, improve the insulating performance of STI, and prevent electric leakage of devices.

Description

【Technical field】 [0001] The invention relates to the technical field of semiconductor design and manufacture, in particular to a method for forming a shallow trench isolation structure. 【Background technique】 [0002] With the continuous shrinking of the feature size of semiconductor devices, the isolation area between devices must also be reduced accordingly. For components below 0.18μm, STI (shallow trench isolation, shallow trench isolation) isolation technology is mostly used. The steps mainly include the etching of the STI, the growth of silicon oxide on the sidewall of the active region, and the filling of silicon oxide in the STI. For some high-voltage device products, such as deep STI trenches (>8000 Angstroms), it is difficult to fill the silicon oxide in the STI. If only one-step filling is used, there will be holes in the STI. Therefore, for this type of product , the filling process is refined into three sub-steps, the schematic diagram of which is shown in ...

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Problems solved by technology

This damage will cause changes in the electrical properties of the device, reduce the insulation performance of STI, cause device leakage, and affect the yield

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