A Method for Eliminating Sharp Angles at the Top of Groove

Abstract

The invention discloses a method for eliminating a shaft corner at the top end of a groove. The method comprises the steps of 1, enabling oxide-nitride-oxide (ONO) to grow, 2, enabling the ONO to be etched, 3, enabling the groove to be etched, wherein the ONO serves as hard mask for dry etching, 4, enabling middle silicon nitride of the hard mask to be etched by a transverse wet method, wherein the sharp corner at the top end of the groove is required to be exposed completely, 5, enabling top layer oxidation film remained on the hard mask to be etched in a complete mode, and meanwhile enabling bottom oxidation film of the hard mask to be etched in transverse mode, 6, conducting homodromous etching at the bottom of the groove, and meanwhile conducting transverse etching and vertical etching for the sharp corner at the top end of the groove so as to reduce the sharp corner at the top end, 7, enabling a sacrificed oxide layer to grow inside the groove, enabling the sharp corner at the top end of the groove to be completely oxidized and to be disappeared, 8, enabling the sacrificed oxide layer to be etched in the wet method, enabling the silicon nitride to be etched in the wet manner, and keeping part of the silicon nitride serving as a barrier layer for helix destabilizing protein (HDP) chemical mechanical lapping. According to the method for eliminating the shaft corner at the top end of the groove, the sharp corner at the top end of the groove can be eliminated, and the fact that trailing HDP can fill the groove without holes is guaranteed.

Description

technical field [0001] The invention belongs to the field of semiconductor integrated circuit manufacturing, and in particular relates to a method for manufacturing a trench power MOS device, in particular to a method for eliminating sharp corners at tops of trenches. Background technique [0002] For trench power MOS, the bottom of the trench is usually filled with a uniform thickness of SiO2 to reduce the gate-drain capacitance, thereby increasing the operating frequency of the device. The SiO2 at the bottom of the trench is usually made of HDP ( H high D density P lasma SiO2, high-density plasma silicon dioxide) to achieve non-porous filling. When sharp corners appear at the top of the trench, HDP-filled SiO2 will have voids in the trench (see figure 1 ), will lead to poor uniformity of the bottom SiO2. The existing process generally includes the following steps: [0003] 1. ONO growth: from bottom to top:—— thermal oxygen / SiN / APM (Atmospheric Pressure Chemi...

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Problems solved by technology

[0009] Because the HDP filling ability has a strong correlation with the topography of the trench, the sharp corner of the top will cause small holes in the HDP filled in the trench (see figure 1 ), resulting in poor uniformity of the oxide film at the bottom of the trench

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