Method for forming shallow trench isolation structure

Abstract

The invention provides a method for forming a shallow trench isolation structure. After a first oxidation layer is formed through an SACVD (Sub-atmospheric Chemical Vapor Deposition) process, fragile surfaces in the first oxidation layer are eliminated by carrying out a dry method back-etching process, and subsequently a second oxidation layer is formed through an HDPCVD (High Density Plasma Chemical Vapor Deposition) process. Besides, after the first oxidation layer formed through the SACVD process, a thermal treatment process is carried out, and the first oxidation layer and the second oxidation layer formed through the HDPCVD process after the thermal treatment are closely approximate to a thermal oxide in density, so that the oxides inside the trench are consistent and matched in characteristics as a whole, and no difference is caused in later procedures. Therefore, the shallow trench isolation structure formed by using the method is good in isolation effect, a semiconductor with the shallow trench isolation structure is good in stability, and electric leakage and breakdown are unlikely to happen.

Description

technical field [0001] The invention relates to the technical field of integrated circuit manufacturing, in particular to a method for forming a shallow trench isolation structure. Background technique [0002] As the semiconductor technology enters the deep sub-micron era, most components below 0.18 microns (such as between the active regions of CMOS integrated circuits) are mostly fabricated using shallow trench isolation (STI) for lateral isolation. With the continuous reduction of the feature size of the semiconductor device, the size of the shallow trench isolation structure used for device isolation also becomes smaller, and correspondingly, the aspect ratio of the isolation trench used to form the shallow trench isolation structure becomes larger. [0003] In the existing advanced manufacturing process, starting from the 45nm technology node, its shallow trench isolation process has begun to use sub-atmospheric pressure chemical vapor deposition (SACVD) process for tr...

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Problems solved by technology

However, compared with the traditional high-density plasma (HDPCVD) process, although the filling capacity of the SACVD process has been greatly improved, but at the same time when this process is applied, a new integration problem arises: in the middle of the trench oxide, a a vulnerable surface (such as figure 1 As shown by the dotted circle in the middle), this fragile surface is very susceptible to erosion by the subsequent wet process, which makes it difficult to control the uniformity of the subsequent process, resulting in poor isolation performance of the shallow trench isolation structure, including the shallow trench isolation structure. Semiconductor devices are prone to leakage, which seriously affects the stability of semiconductor devices containing shallow trench isolation structures

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