an etching method

Abstract

The application discloses an etching method. After the protective layer at the bottom of the channel hole is removed by a dry etching process, the memory layer at the bottom of the channel hole is removed by a wet etching process or a gas etching process. , due to the isotropic characteristics of the wet etching process, when wet removing the memory layer at the bottom of the channel hole, the wet etching process will not only corrode the memory layer downward along the vertical direction of the channel hole, but also Etch the memory layer laterally along the lateral direction of the channel hole, so that the lateral dimension of the etched memory layer is larger than the lateral dimension of the protective layer etched by the previous dry etching process, and finally remove the sidewall of the channel hole After the protective layer on the top, a large lateral space will be formed at the bottom of the trench hole. The larger lateral space is conducive to the connection of the subsequently deposited polysilicon to the epitaxial structure at the bottom of the channel hole, thereby improving the performance of the 3D NAND memory.

Description

technical field [0001] The present application relates to the technical field of semiconductor manufacturing, and in particular to an etching method. Background technique [0002] 3D NAND memory is a flash memory device with a three-dimensional stack structure, and its storage core area is composed of alternately stacked metal gate layers and insulating layers combined with vertical channel holes. Under the condition of the same area, the more metal gate layers stacked vertically, the higher the storage density and capacity of the flash memory device. The number of stacked layers of word lines in the common memory structure can reach tens to hundreds of layers. [0003] During the manufacturing process of 3D NAND memory, it is necessary to remove part of the memory layer formed at the bottom of the channel hole. The existing method of removing part of the memory layer at the bottom of the channel hole is generally realized by a dry etching process. However, due to the ani...

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Problems solved by technology

However, due to the anisotropic characteristics of the dry etching process, the plasma can only etch downward along the vertical direction of the channel hole, and in 3D NAND memory, the depth of the channel hole is relatively deep, resulting in The critical dimension at the bottom of the etched channel hole is small, so that the connection between the subsequently formed channel layer and the epitaxial structure at the bottom of the channel hole is poor, thus affecting the performance of 3D NAND memory

[0004] In addition, when the 3D NAND memory is an overall structure formed by multiple sub-stack structures, the plasma will also destroy the film at the docking position of the stack structure adjacent to the sub-stack structure, reducing the performance of the 3D NAND memory.

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