A method for manufacturing a semiconductor device having a field plate structure with a gradual thickness in a trench

Abstract

A method for manufacture a semiconductor device having a field plate structure with a gradual thickness in a trench includes forming a trench on a surface of a wafer; Filling the trench with siliconoxide by deposition; Removing a part of the surface by etching the silicon oxide in the trench; Forming a silicon oxide corner structure at a corner at the top of the trench by thermal oxidation; Depositing nitrogen-containing compounds on the wafer surface; Dry etching nitrogen-containing compound, silicon oxide corner structure surface forms nitrogen-containing compound sidewall residue extending into the trench; A surface part of that silicon oxide in the trench is remove by etching with the residual nitrogen-containing compound sidewall as a mask; Repeating the above three steps until thesilicon oxide in the trench is etched to the desired bottom silicon oxide thickness; Removing nitrogen compounds from trenches and fill the trenches with polycrystalline silicon. The invention reducesthe oxidation time and improves the production efficiency. And the backward diffusion of the substrate impurity to the epitaxial layer is reduced, and the process is simple.

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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