Method for improving surface roughness of shielding gate

Abstract

The invention provides a method for improving the surface roughness of a shielding gate. The method comprises the steps of providing a substrate, and forming a graphical hard mask on the substrate; taking the graphical hard mask as a mask, and etching the substrate to form a first trench; forming a gate dielectric layer in the first trench, and obtaining a second trench; filling the second trenchwith polycrystalline silicon, and covering the gate dielectric layer and the residual hard mask; executing a grinding process, and stopping grinding on the surface of the hard mask to flatten the surface of the polycrystalline silicon; performing dry etching on the polycrystalline silicon for the first time, and removing the polycrystalline silicon above the second trench; and carrying out seconddry etching on the polycrystalline silicon subjected to the first dry etching to form a shielding gate, wherein the surface of the shielding gate is flat. The problem that the surface of the formed shielding gate is rough can be solved, so that a process window of a dielectric layer formed between the shielding gate and the control gate is increased, and the electric leakage performance between the control gate and the shielding gate is improved.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for improving surface roughness of a shielding grid. Background technique [0002] In the field of medium and low voltage devices with a withstand voltage of 100v and below, 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...

AI Technical Summary

Problems solved by technology

However, with the development of the process, the size of the opening of the second trench is gradually reduced. When etching polysilicon to form the shield gate 130, the surface of the shield gate 130 will appear uneven, even in the depth of the first trench. When the width ratio is greater than or equal to...

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