Preparation method of shallow trench isolation structure

Abstract

The invention provides a preparation method for a shallow trench isolation structure. The method comprises the steps of forming a trench in a semiconductor substrate, forming a linear oxidation layer in the trench, filling the trench with an isolation dielectric layer and conducting high temperature annealing. According to the step of forming the linear oxidation layer, a nitride layer is deposited on the inner surface of the trench, the nitride layer is oxidized, and a nitrogen oxide layer is formed on the inner surface of the trench. After the nitride layer is deposited, oxidation is carried out, the surface of the trench can be smoothed, stress inside the trench is relieved, serious losses, caused by oxidation directly carried out on the side wall of the trench, of materials of the side wall of the trench can be avoided, and then difficulty of diffusing of oxygen-containing groups or H2O formed in the follow-up annealing process into the semiconductor substrate is increased; the nitrogen oxide layer can be used as transitional materials with which the trench is filled in the follow-up process and can also effectively prevent the oxygen-containing groups or H2O formed in the follow-up annealing process from diffusing to the substrate of the side wall of the trench, the active area boundary is prevented from being oxidized, and therefore shrinkage of the critical size of the active area is reduced.

Description

Technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preparing a shallow trench isolation structure. Background technique [0002] With the development of integrated circuits, modern CMOS chips usually integrate millions of active devices (ie, NMOS transistors and PMOS transistors) on a common silicon substrate material, and then realize various complex types through specific connections. Logic function or analog function, and in addition to these specific functions, in the circuit design process, it is usually assumed that there is generally no other mutual influence between different devices. Therefore, it is necessary to isolate the devices in the manufacture of integrated circuits, which requires isolation technology. [0003] With the development of devices toward deep sub-micron, isolation technology has evolved from a local oxidation of silicon (LOCOS) process to a shallow trench isolation (STI) technology. Th...

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Problems solved by technology

[0005] In the existing method for growing a linear oxide layer, it usually includes: oxidizing the side wall of the trench to form a thin linear oxide layer. Since the oxidation process is directly performed in the trench to form an oxide layer, the silicon on the side wall of the trench will be formed. A large loss of material, and subsequent oxygen-containing groups in the isolation dielectric layer or the formation of H 2 O is particularly easy to diffuse to the boundary of the active region to oxidize it, thereby reducing the critical dimension of the active region

The reduction of the critical dimension of the active region will affect the saturation current of the device, which in turn will affect the performance of the entire device

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