Method to prevent spalling defect of ono structure

Abstract

The method for preventing ONO structure peeling defects of the present invention includes: providing a semiconductor substrate; depositing a front-side ONO structure and a back-side ONO structure on the front-side and back-side of the semiconductor substrate respectively; selectively etching the front-side ONO structure, and retaining part of the The bottom oxide layer of the front ONO structure; perform wet etching for the first time, and etch the remaining part of the bottom oxide layer of the front ONO structure and the top oxide layer of the back ONO structure; do not carry out the drying process, directly A second wet etch is performed. In the present invention, the second etching is directly performed without the drying process after the first etching, so that the underlying oxide layer exposed by the front ONO structure etching and the nitride layer with the back ONO structure peeled off during the first etching process A water film remains between, so that it can be washed away during the second etching process without sticking to the front side of the device, thereby improving the performance of the device.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preventing peeling defects of an ONO structure. Background technique [0002] In the existing flash memory process, such as figure 1 As shown, an oxide layer 501, a nitride layer 502, and an oxide layer 503 are sequentially deposited on a semiconductor substrate 1 to form a front-side ONO structure 5. Due to process characteristics, a back-side ONO with a consistent structure will be formed on the back of the semiconductor substrate 1 at the same time. structure6. Next, a photoresist pattern 7 is formed on the front ONO structure 5, and the front ONO structure 5 is etched. In order to prevent over-etching, part of the oxide layer 501 is retained during the etching process. Afterwards, wet etching is used to remove the remaining part of the oxide layer 501 and the photoresist pattern 7 . [0003] However, during the wet etching process, the etching solution ...

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Problems solved by technology

[0003] However, during the wet etching process, the etching solution will also etch the back ONO structure 6 when etching the front side. After the wet etching process, the oxide layer 603 on the top layer of the back ONO structure 6 is removed. etched away, therefore, the middle nitride layer 602 is easily peeled off and formed on the front side of the device, such as figure 1 In the part where A is located, after the drying process, the nitride layer peeling defect formed on the front side of the device is difficult to remove, which affects the performance of the device

In the prior art, the defect is usually cleaned by adding one step of cleaning process, but the cleaning efficiency of the added cleaning process is lower than 30%, and the increase of process steps affects the throughput of the process

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