Forming method of semiconductor structure and forming method of MOS transistor

Abstract

The invention discloses a forming method of a semiconductor structure and a forming method of an MOS transistor. The forming method of the semiconductor structure comprises the steps that a semiconductor substrate is provided; a semiconductor layer is formed on the surface of the semiconductor substrate; from the surface of the semiconductor substrate to the surface of the semiconductor layer, the concentration of first impurity ions in the semiconductor layer decreases at first, reaches the lowest concentration, and then increases; and first ion implantation is carried out in the semiconductor layer by using the same impurity ions, wherein the first ion implantation depth is less than the thickness of the semiconductor layer. From the surface of the semiconductor substrate to the surface of the semiconductor layer, the concentration of second impurity ions formed by ion implantation increases at first, and then decreases, while the concentration of the first impurity ions in-situ doped in the semiconductor layer decreases at first, reaches the lowest concentration, and then increases. The uniformity of the overall concentration formed by adding the concentration of the first impurity ions of all depths in the semiconductor layer and the concentration of the second impurity ions is high, which is conducive to improving the electrical properties of the semiconductor structure.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for forming a semiconductor structure and a method for forming a MOS transistor. Background technique [0002] In the existing semiconductor manufacturing process, ion doping is a very important and common process. Ion doping mainly includes three methods: diffusion, ion implantation and in-situ doping. The first two methods require a high-temperature process, and the ion implantation process may also cause damage to the surface of the semiconductor structure to be implanted, while the in-situ doping is directly doped with the required impurities during the epitaxial growth process. Since the in-situ doping is completed in the epitaxial growth process, no other process is required, especially without high temperature, it can be applied in the formation process of many semiconductor devices, and the in-situ doped dopant ions The concentration is controllable, ...

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Problems solved by technology

[0004] But in situ doping has its limitations

Since the doping concentration of in-situ doping is usually limited by the solid solubility of the material, it cannot reach a very high doping concentration, and may not meet the manufacturing requirements of some semiconductor structures.

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