Preparation method of epitaxial layer

Abstract

The invention provides a preparation method of an epitaxial layer. The preparation method comprises the following steps: providing a substrate; forming a first epitaxial layer on the substrate; sequentially forming a plurality of intrinsic epitaxial layers on the first epitaxial layer, and after one intrinsic epitaxial layer is formed every time, carrying out ion implantation on the intrinsic epitaxial layer, wherein all the intrinsic epitaxial layers after ion implantation form a second epitaxial layer; and forming a third epitaxial layer on the second epitaxial layer. According to the invention, the control capability and uniformity of impurities in the epitaxial layer are improved.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preparing an epitaxial layer. Background technique [0002] In the high-end Split Gate Trench MOSFET tube process, it is necessary to manufacture graded epitaxy, which makes the shape of the electric field formed by charge balance in the vertical distribution controllable, thereby improving the UIS (Unclamped Inductive Switching) performance and reliability of MOSFET devices . In the prior art, the formation of graded epitaxy generally adopts the method of vapor phase deposition. When the epitaxial layer is formed, the impurity diffusion is introduced into the epitaxial layer to dope the epitaxial layer, so as to grow multiple epitaxial layers, and then use the thermal process in the epitaxial manufacturing. And the thermal process in the subsequent processing process redistributes the impurities to form the required impurity distribution morphology. In the ...

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Problems solved by technology

In the method in the prior art, the first-grown epitaxial layer has experienced more thermal processes than the later-grown epitaxial layer, so the transition region between each layer of epitaxy is not the same, which will cause the impurity distribution to not follow the approximate ideal The linear gradient distribution makes the follow-up process thermal process debugging and design matching extremely difficult; and the diffusion method of the existing technology is used to do the doping when forming the epitaxial layer. Due to the complexity of the epitaxial growth process, the thickness of each epitaxial layer The doping concentration is difficult to simulate and control the doping concentration through various process simulation software, and it is difficult to ensure the uniformity of impurity doping by diffusion. After forming a multi-layer epitaxial layer, the uniformity error will increase

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