Silicon dioxide SAB removing method

Abstract

The invention discloses a silicon dioxide SAB removing method which comprises the following steps: providing a flash memory wafer, wherein a device on the flash chip is covered by silicon dioxide SAB; reacting NH3 and HF steam with silicon dioxide SAB on the flash memory wafer to generate (NH4)2SiF6; and heating the reacted flash memory wafer to volatilize (NH4)2SiF6 to obtain a flash memory wafer of which silicon dioxide SAB is removed. According to the method, first, NH3 and HF steam are reacted with a silicon dioxide SAB film on the flash memory wafer to generate (NH4)2SiF6, and then, the flash memory wafer is heated to remove the silicon dioxide SAB film, thereby reducing undercut and avoiding leakage risks.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for removing silicon dioxide SAB. Background technique [0002] At present, with the development of semiconductor devices, self-aligned metal silicides such as self-aligned nickel silicon and titanium silicon are introduced to produce silicides that can be well integrated with exposed sources, drains, and polysilicon gates. Silicon (Si) alignment. This is because metallic nickel (Ni), titanium (Ti) or cobalt (Co) can react with silicon, but not with silicon oxides such as silicon dioxide (SiO 2 ), silicon nitride such as silicon nitride (Si 3 N 4 ) or silicon oxynitride (SiON) reaction. Therefore, Ni, Ti or Co will only find the part of silicon to react, and for silicon oxides such as silicon dioxide (SiO 2 ), silicon nitride such as silicon nitride (Si 3 N 4 ) or the part covered with silicon oxynitride (SiON) will not react, just like Ni, Ti or Co will...

AI Technical Summary

Problems solved by technology

Due to the difference in thickness and properties of silicon dioxide film in different regions after dry etching, for example, the silicon dioxide on the side wall and bottom of the side wall of the cell area of ​​the memory unit is easier to be etched by hydrofluoric acid, and has a faster etching rate. rate, while the high-voltage device area contains a thick thermal silicon dioxide film, which has a low etch rate and is not easy to be removed

In order to be able to remove it, it is necessary to add a considerable amount of etching, and this will inevitably cause an excessive amount of etching in the Cell region of the memory unit, resulting in over-etching.

Due to the isotropy of silicon dioxide etching, after the silicon dioxide on the sidewall is etched, the silicon dioxide at the bottom of the sidewall will continue to be etched, forming a relatively large undercut, resulting in leakage consequences

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