Preparation method for split gate trench MOSFET(metal-oxide-semiconductor-field-effect-transistor)

Abstract

The invention provides a preparation method for a split gate trench MOSFET (metal-oxide-semiconductor-field-effect-transistor). The preparation method comprises the following steps: (1) providing a substrate, and growing an epitaxial layer on the surface of the substrate; (2) etching the epitaxial layer to form a trench with a first depth, depositing a nitride layer on the surface of the trench, then corroding off the nitride layer at the bottom of the trench, and retaining the nitride layer on the side wall; (3) continuously etching the epitaxial layer material at the bottom of the trench to reach a second depth, and thermally growing an oxide layer attached to the side wall and the bottom of the trench which is not covered by the nitride layer; (4) filling the lower part of the trench with a first conductive material, removing the nitride layer on the side wall, and manufacturing an isolating layer on the surface of the first conductive material; (5) growing a gate oxide layer covering the exposed side wall of the upper part of the trench, and filling the upper part of the trench with a second conductive material to form the split gate trench MOSFET with the narrower upper part and the wider lower part. The device structure prepared by the preparation method disclosed by the invention can acquire a larger source region area and a larger source region contact hole; the avalanche characteristic is enhanced; furthermore, the density of the trench can be increased, and lower RSP can be obtained.

Description

technical field [0001] The invention relates to the preparation of a semiconductor device, in particular to a preparation method of a split gate type trench MOSFET. Background technique [0002] For semiconductor devices commonly used in power electronic systems and power management, the power Metal-Oxide-Semiconductor-Field-Effect-Transistor MOSFET (Metal-Oxide-Semiconductor-Field-Effect-Transistor), or Insulated Gate Field-Effect Transistor, is widely introduced . [0003] Trench power MOSFET is a new high-efficiency and power switching device developed after MOSFET. It adopts trench gate structure field effect transistor, which not only inherits the high input impedance of MOS field effect transistor (≥10 8 Ω), small driving current (about 0.1μA), and also has excellent characteristics such as high withstand voltage, large working current, high output power, good transconductance, and fast switching speed. It is precisely because it combines the advantages of electron t...

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Problems solved by technology

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a split-gate trench MOSFET, which is used to solve the problem of small contact area of ​​the source region, poor avalanche performance, and trench MOSFET prepared in the prior art. Problems such as low slot density

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