Process method of shielding gate trench type device

Abstract

The invention provides a process method of a shielding gate trench type device. The process method comprises the steps of providing a substrate; forming a first trench on the substrate; sequentially forming a first oxide layer and a second oxide layer in the first trench, and obtaining a second trench, wherein the density of the first oxide layer is greater than that of the second oxide layer; forming a shielding gate in the second trench; forming a third oxide layer on the shielding gate, wherein the density of the third oxide layer is greater than that of the second oxide layer; and partially etching the first oxide layer, the second oxide layer and the third oxide layer to enable the thicknesses of the first oxide layer, the second oxide layer and the third oxide layer to be reduced, enabling the surface topography of the remaining second oxide layer and the remaining third oxide layer to be the same as the surface topography of the shielding gate, and enabling the thickness of thecombination formed by the remaining first oxide layer, the second oxide layer and the third oxide layer to be uniform, and thus improving the electric leakage performance between a control gate and the shielding gate.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a process method for shielding gate trench type devices. Background technique [0002] In the field of medium and low voltage devices with a withstand voltage above 60V, Shield Gate Trench (SGT) devices are widely used because of their low specific on-resistance and low gate-drain coupling capacitance. The gate structure of shielded gate trench devices includes shielded polysilicon and polysilicon gate. Shielded polysilicon is usually also called source polysilicon, which are all formed in the trench. According to the different settings of shielded polysilicon and polysilicon gate in the trench, it is usually divided into upper and lower gates. structure and left-right structure. In the upper and lower structure, the shielding polysilicon is located at the bottom of the trench, the polysilicon gate is located at the top of the trench, and the polysilicon gate and the shie...

AI Technical Summary

Problems solved by technology

[0004] One of the difficulties in process control of shielded gate trench devices is the thickness of the third oxide layer, the first oxide layer and the second oxide layer between the control gate and the shielded gate. If it is too thin, it will cause leakage between the control gate and the shielded gate. become larger and affect the performance of the device

In the preparation process of shielded gate trench devices, the surface of the shielded gate formed by etching polysilicon usually forms a topography with high edges and low middle, so the leakage performance from the control gate to the shielded gate will be caused at the edge of the shielded gate. Poor, which in turn affects the leakage performance of the entire device

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