A process method for increasing the cell density of trench mosfet and the structure of trench mosfet

Abstract

The invention discloses a process method for increasing the cell density of a trench MOSFET and a trench MOSFET structure, comprising the following steps: step S4: deposit polysilicon, remove polysilicon outside the trench, and remove the first nitride Silicon, forming a first doped region and a third doped region in the epitaxial layer, depositing second silicon nitride, etching the second silicon nitride, forming sidewalls on the sidewalls of the polysilicon, the The widths of the sidewalls formed by the left and right side walls of the polysilicon are equal; step S5: implant boron atoms or phosphorus atoms into the first doped region to form a second doped region, and the doping concentration of the second doped region is 20-100 times the doping concentration of the first doping region, removing the sidewall, removing the polysilicon protruding from the surface of the first oxide layer, depositing a dielectric layer and removing the dielectric layer and silicon in the set area, A source contact hole is formed. The process method for increasing the cell density of the trench MOSFET and the structure of the trench MOSFET provided by the invention have the advantages of realizing more uniform threshold voltage and on-resistance.

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...

AI Technical Summary

Problems solved by technology

[0005] The invention provides a process method and a trench MOSFET structure for increasing the cell density of the trench MOSFET, aiming to solve the problem of large on-resistance per unit area of ​​the chip

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