Preparation method of groove type power device

Abstract

The invention provides a preparation method of a groove type power device. The preparation method comprises the following steps of: providing a substrate which comprises a device unit region and an electrode connection region, and forming an ONO layer on the substrate; etching the substrate so as to form a plurality of first grooves in the device unit region and a plurality of second grooves in the electrode connection region; forming first dielectric layers on the inner walls of the first groove and the second groove; forming a shield gate layer and an electrode connecting layer on the first dielectric layer in each of the first groove and the second groove; performing wet etching on the first dielectric layer in the first groove by taking the ONO layer as a mask to enable the top part of the first dielectric layer in the first groove to be lower than the top part of the shield gate layer; and removing the ONO layer, and sequentially forming a second dielectric layer and a polycrystalline silicon layer on the substrate. The preparation method improves the reliability of the groove type power device.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preparing a trench power device. Background technique [0002] The shielded gate trench power device is a typical trench MOSFET, which has the advantages of low conduction loss of the traditional trench MOSFET, so the shielded gate trench power device is widely used. In the prior art, in the manufacturing process of shielded gate trench power devices, an oxide layer is first formed in the trenches of the electrode connection area and the device unit area, and the oxide layer will cover the electrode connection area and the trenches of the device unit area. The inner wall and the surface of the substrate, and then form a shielding gate layer on the oxide layer of the device unit area, the shielding gate layer fills the trench, and then use a wet etching process to remove part of the oxide layer in the trench in the device unit area; Wet etching is isotropic et...

AI Technical Summary

Problems solved by technology

In the prior art, in the manufacturing process of shielded gate trench power devices, an oxide layer is first formed in the trenches of the electrode connection area and the device unit area, and the oxide layer will cover the electrode connection area and the trenches of the device unit area. The inner wall and the surface of the substrate, and then form a shielding gate layer on the oxide layer of the device unit area, the shielding gate layer fills the trench, and then use a wet etching process to remove part of the oxide layer in the trench in the device unit area; Wet etching is isotropic etching. Wet etching will cause undercutting of the oxide layer in the trench in the electrode connection area. When polysilicon is deposited in the trench in the device unit area in the subsequent process, the polysilicon will also Deposited in the position where undercutting occurs in the electrode connection area, resulting in residual polysilicon in the trench in the electrode connection area, the residual polysilicon may be short-circuited with the electrode connection layer in the electrode connection area, which will easily cause a short circuit in the device, thus affecting the device reliability

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