Manufacturing method of semiconductor device with field plate structure with gradient thickness in trench

Abstract

Disclosed is a method for manufacturing a semiconductor device having a field plate structure with gradually varying thickness in a trench, the method comprising: step A, forming a trench in a surface of a wafer; step B, filling the trench with silicon oxide by means of deposition; step C, removing a portion of the surface of the silicon oxide in the trench by means of etching; step D, forming a silicon oxide corner structure at a corner at the top of the trench by means of thermal oxidation; step E, depositing a nitrogen-containing compound on the surface of the wafer; step F, carrying out dry etching on the nitrogen-containing compound to form, on a surface of the silicon oxide corner structure, nitrogen-containing compound sidewall residues extending to the inside of the trench; step G, taking the nitrogen-containing compound sidewall residues as a mask, and removing a portion of the surface of the silicon oxide in the trench by means of etching; successively repeating step E to step G until the silicon oxide in the trench is etched to be of the thickness required for bottom silicon oxide; step H, removing the nitrogen-containing compound in the trench; and step I, filling the trench with polycrystalline silicon.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for manufacturing a semiconductor device with a field plate structure with a gradually changing thickness in a trench. Background technique [0002] In order to reduce energy consumption and save energy, low-voltage power metal oxide semiconductor field effect transistor (MOSFET) technology is undergoing continuous technical improvement, and device structures such as field plates and super junctions are also transplanted from high-voltage power devices to low-voltage devices and improved. and optimized to reduce the specific on-resistance of low-voltage power devices. [0003] Among them, MOSFETs with a trench field plate structure based on a constant thickness are particularly common. However, the uneven distribution of potential and electric field due to the constant thickness of the field plate dielectric makes it difficult to optimize the device characteri...

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Problems solved by technology

[0006] However, this manufacturing method includes multiple times of oxidation and etching back, which increases the reverse diffusion of impurities from the substrate to the epitaxial layer to a certain extent, increases the process time, and reduces the production efficiency.

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