STI (shallow trench isolation) structure and production method thereof

Abstract

The invention provides an STI (shallow-trench isolation) structure and a production method thereof. Compared with the traditional STI structure made of silicon oxide, the STI structure is characterized in that a second silicon nitride layer, greater than the silicon oxide in density and hardness, is formed at the bottom and provided with tensile stress or pressure stress, thereby changing component of the STI structure and improving tensile stress of an N-type channel or pressure stress of a P-type channel; at the meanwhile, the surface of the STI structure is the silicon oxide layer without the residual second silicon nitride layer, the silicon oxide layer releases irregularity, caused by stress of the second silicon nitride layer, of the surface of the STI structure, so that leak currents, caused by contact of polysilicon gates on the second silicon nitride layer, are avoided during the following processes. The STI structure and the production method have the advantages that at the premise that the leak currents are maintained, channel stress is improved to increase carrier mobility, and work current of the device is enhanced so as to improve operating characteristic thereof.

Description

technical field [0001] The invention belongs to the technical field of semiconductor devices, and relates to a shallow trench isolation structure and a preparation method thereof. Background technique [0002] With the development of semiconductor technology, the feature size of devices in integrated circuits has become smaller and smaller, and the speed of devices and systems has increased accordingly. After the semiconductor process enters the deep submicron stage, in order to realize high-density, high-performance ULSI devices and circuits, the isolation and planarization process becomes more and more important. [0003] At present, methods for forming isolation regions mainly include local oxidation isolation process (LOCOS) or shallow trench isolation process (STI). [0004] The LOCOS process is to deposit a layer of silicon oxide on the surface of the wafer, and then perform etching to oxidize and grow silicon oxide in part of the recessed area, and the active device ...

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Problems solved by technology

However, the LOCOS process has a series of disadvantages: 1) There is a phenomenon of "bird's beak" (bird's beak) growing on the edge of silicon nitride, and the "bird's beak" takes up the actual space and increases the volume of the circuit. The "mouth" makes the field silicon oxide invade the active area; 2) The field implantation redistributes during the high temperature oxidation process, causing the narrow width effect of the active device (narrow width effect); 3) The field silicon oxide becomes thinner in the narrow isolation area; 4) Uneven surface shape

[0008] It is difficult to further increase the operating current at the same threshold voltage by using the existing doping method in traditional devices, so that the carrier mobility and the operating current of the channel can meet the technical requirements of the next generation of smaller-sized devices. However, by adjusting the angle of the channel stress, the carrier mobility and the operating current of the channel can be further improved

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