Process method for improving cell density of trench MOSFET and trench MOSFET structure

Abstract

The invention discloses a process method for improving the cell density of a trench MOSFET and a trench MOSFET structure. The method comprises the following steps: depositing polycrystalline silicon,removing the polycrystalline silicon outside a trench, removing first silicon nitride, forming a first doped region and a third doped region in an epitaxial layer, depositing second silicon nitride, etching the second silicon nitride, and forming side walls on the side walls of the polycrystalline silicon, wherein the widths of the side walls formed by the left side wall and the right side wall ofthe polycrystalline silicon are equal; injecting boron atoms or phosphorus atoms into the first doped region to form a second doped region, wherein the doping concentration of the second doped regionis 20-100 times that of the first doped region, removing the side walls, removing polycrystalline silicon protruding out of the surface of the first oxide layer, depositing a dielectric layer, removing the dielectric layer and silicon in a set region, and forming source region contact holes. The process method for improving the cell density of the trench MOSFET and the trench MOSFET structure provided by the invention have the advantages of being capable of realizing more uniform threshold voltage and conduction resistance and the like.

Description

technical field

[0001] The invention relates to the technical field of semiconductors, in particular to a process method for increasing the cell density of a trench MOSFET and a trench MOSFET structure. 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...

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