Manufacturing method of trench MOSFET

Abstract

The invention discloses a manufacturing method of a trench MOSFET. The manufacturing method comprises the following steps: growing an epitaxial layer on the upper surface of a substrate; forming a trench in the epitaxial layer; growing a gate oxide layer on the surface of the trench by adopting a high-temperature oxidation process method, and then depositing polycrystalline silicon; removing the polycrystalline silicon outside the groove, then injecting boron atoms into the surface layer of the epitaxial layer, and injecting arsenic atoms or(and)antimony atoms into the surface layer of the epitaxial layer in a preset area; performing high-temperature annealing to form a P-type diffusion area and an N-type diffusion area, wherein the N-type diffusion area is located in the surface layer ofthe P-type diffusion area; the manufacturing method has the beneficial effects that a high-temperature treatment process is reduced, so that diffusion of doped substances in the substrate into the epitaxial layer in the high-temperature treatment process is reduced, and therefore, breakdown voltage higher than that in the prior art can be obtained, or smaller on-resistance per unit area can be obtained under the condition of realizing the same breakdown voltage.

Description

technical field [0001] The invention belongs to the technical field of semiconductor device manufacturing, and in particular relates to a method for manufacturing a trench MOSFET. Background technique [0002] The MOSFET chip is a discrete device, which belongs to the category of semiconductor power devices, and belongs to the field of semiconductor chips with integrated circuits. The most critical index parameters of MOSFETs include breakdown voltage (especially drain-source breakdown voltage), on-resistance and threshold voltage ( It is also called turn-on voltage in spoken language), usually, the larger the breakdown voltage, the better, and the smaller the on-resistance, the better. In order to achieve its nominal breakdown voltage, the internal structure of the MOSFET chip uses an epitaxial layer with a specific resistivity and a specific thickness to bear the pressure. Usually, the higher the breakdown voltage required to achieve, the resistivity of the epitaxial layer...

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Problems solved by technology

[0007] Disadvantages of the prior art: the process flow includes at least three high-temperature treatment processes (high-temperature oxidation to form a gate oxide layer, high-temperature annealing to form a body region, and high-temperature annealing to form a source), during these high-temperature treatment processes, the dopant in the substrate Impurities diffuse into the epitaxial layer because their doping concentration is higher than that of the epitaxial layer, resulting in a decrease in the resistivity of the epitaxial layer, and consequently a decrease in the breakdown voltage of the MOSFET. In this case, in order to achieve the goal Breakdown voltage, the initial resistivity or (and) initial thickness of the epitaxial layer needs to be increased to offset the influence of the diffusion of dopant substances in the substrate into the epitaxial layer, which leads to an increase in the on-resistance per unit area of ​​the chip Larger, so a larger chip area is required to achieve the target on-resistance, and the chip cost increases

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