Forming method for 3D NAND memory

Abstract

A forming method for a 3D NAND memory comprises the following steps: providing a semiconductor substrate, wherein stack structures are formed on the semiconductor substrate, each stack structure comprises a plurality of sacrificial layers and a plurality of isolating layers which are alternately stacked, the stack structures are respectively provided with a first channel hole and a second channelhole which are communicated with each other, the second channel hole has an alignment offset relative to the first channel hole, a step is formed at the junction of the first channel hole and the second channel hole, and the first channel hole is filled with a sacrificial material layer; after a side wall is formed, carrying out etching-back to remove the sacrificial material layer with a part ofthe thickness; carrying out etching on the step, so that the gradient of the step is reduced; forming charge storage layers on the side walls and at the bottoms of the first channel hole and the second channel hole; forming channel hole sacrificial layers on the charge storage layers; and sequentially carrying out etching on the channel hole sacrificial layer and the charge storage layer at the bottom of the first channel hole, so that an opening is formed. The method provided by the invention has the advantages that the charge storage layer at the step can be prevented from being broken or damaged during the etching, so that failure of the memory can be avoided.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for forming a 3D NAND memory. Background technique [0002] NAND flash memory is a better storage device than hard disk drives, and it has been widely used in electronic products as people pursue non-volatile storage products with low power consumption, light weight and high performance. At present, the NAND flash memory with a planar structure is close to the limit of practical expansion. In order to further increase the storage capacity and reduce the storage cost per bit, a 3D NAND memory with a 3D structure is proposed. [0003] The manufacturing process of the existing 3D NAND memory includes: providing a substrate on which a stacked structure in which isolation layers and sacrificial layers are alternately stacked; etching the stacked structure to form an exposed substrate surface in the stacked structure channel hole; form a storage structure in the cha...

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Problems solved by technology

[0004] In order to further increase the storage capacity, when forming the stack structure in the prior art, a multi-layer stack structure is usually formed, and each layer stack structure includes several alternately stacked sacrificial layers and isolation layers. In the multi-layer stack structure A channel hole is formed; a storage structure is formed in the channel hole, but this storage structure still has the problem of failure

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