VDMOS transistor and preparation method thereof

Abstract

The invention discloses a VDMOS transistor and a preparation method thereof and belongs to the field of semiconductors. The VDMOS transistor comprises a first conduction type substrate, a first conduction type epitaxial layer, a second conduction type injection region, a first conduction type highly doped source region and a grid structure, the second conduction type injection region and the first conduction type highly doped source region are arranged in the epitaxial layer, and the grid structure comprises a grid insulating layer, a semi-insulating polycrystalline silicon layer, a silicon oxynitride layer and a polycrystalline silicon layer. The grid insulating layer is arranged above a drift region of the epitaxial layer, the semi-insulating polycrystalline silicon layer is arranged above the grid insulating layer, the silicon oxynitride layer is arranged above a channel region, and the polycrystalline silicon layer is covered on the semi-insulating polycrystalline silicon layer and the silicon oxynitride layer. A heat nitriding silicon oxynitride layer is introduced into the preparation method, a traditional silica layer which is used as a gate medium layer on a channel is replaced, and the semi-insulating polycrystalline silicon layer is added on an oxide layer which is arranged above the drift region of the epitaxial layer. The VDMOS transistor and the preparation method thereof can obviously reduce grid-drain capacitance and achieve overcoming the defects that insulating performance of the grid insulating layer is poor, current leaking of a grid electrode is increased, and degeneration of the VDMOS performance is unreliable.

Description

technical field [0001] The invention relates to the field of semiconductor devices, in particular to a VDMOS transistor and a preparation method thereof. Background technique [0002] Vertical conductive double-diffused field effect transistor (VDMOSFET, hereinafter referred to as VDMOS) is a semiconductor power device with high input impedance, high thermal stability, fast switching speed, small driving current, small dynamic loss, and small distortion. , industrial control, automotive electrical appliances and other fields have been widely used. [0003] figure 1 It is a schematic diagram of a cross-sectional structure of a traditional N-channel VDMOS transistor. Such as figure 1 As shown, taking the N-channel MOS transistor as an example, the vertical double-diffused MOS transistor is in the highly doped N + A layer of low-doped N - The doping level of the epitaxial layer 111 and the epitaxial region largely determines the breakdown voltage of the device. There is a...

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Problems solved by technology

[0007] The existing technology has not clearly aimed at overcoming the significant increase in gate leakage current caused by the long-term operating temperature rise of the device, and the degradation of VDMOS performance and reliability.

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