Production method of a 3D NAND wire hole including silicon-rich silicon nitride isolating dielectric layer

Abstract

Provided is a production method of a 3D NAND wire hole. The wire hole is formed in a string selection region and is filled with tungsten to allow wire connection; before a pre-cleaning step, a silicon-rich silicon nitride layer is deposited in the wire hole to serve as an isolating dielectric layer. In the production method, the silicon-rich silicon nitride deposition process is used to replace traditional silicon nitride deposition, so that top-bottom non-uniformity of the isolating dielectric layer in the wire hole caused by NH3 decomposition or reaction is relieved; therefore, etching problem caused by the distribution non-uniformity of the isolating dielectric layer is avoided, and process stability and reliability are improved.

Description

technical field [0001] The present application relates to the technical field of three-dimensional (3D) memory, and more specifically, relates to a preparation method of a 3D NAND wiring hole including a silicon-rich silicon nitride isolation dielectric layer. Background technique [0002] With the rapid development of flash memory, the structure of 3D flash memory has been developed rapidly, and NAND flash memory is a better storage device than hard disk drives. As people pursue non-volatile storage products with low power consumption, light weight and good performance , 3D NAND flash memory has been widely used in electronic products. [0003] In the 3D NAND structure, in the current process, a plurality of wire holes are formed by multiple etching in the SS (string selection) region, and metal tungsten is filled in the wire holes by chemical vapor deposition (CVD), so as to realize wire connection, Figure 1(a) and 1(b) Schematic diagrams of wire holes and tungsten wire...

AI Technical Summary

Problems solved by technology

[0005] The above-mentioned silicon nitride layer can protect the silicon on the side wall of the wire hole and the tungsten metal on the bottom layer during pickling, and can prevent the wire hole from expanding due to pickling corrosion. However, NH is generally used when growing silicon nitride according to the traditional process. 3 gas, while due to heavy metals on NH 3 The decomposition has a catalytic effect, and there may be heavy metals W and NH 3 Therefore, the step coverage of the formed SiN layer will be poor, and it will affect the resistance of the wire

This will cause the problem of uneven thickness of the upper and lower silicon nitride layers in the wire hole, as shown in Figure 4. Figure 4(a)-4(c) They are the SiN layer surveying drawings of the upper, middle and bottom of the wire hole respectively. As can be seen from the figure, the thickness of the SiN layer formed as the wire hole goes down becomes thicker, and the thickness of the SiN layer at the bottom of the wire hole is nearly twice the thickness of the top

The above-mentioned thickness distribution of the SiN layer has a certain influence on the subsequent etching of SiN at the bottom of the wire hole, so that the etching of the SiN layer requires more energy or time, and due to the high hardness of SiN, in step 3 (c) The etching energy required to open the deposited SiN at the bottom is relatively large, which will increase the probability of excessive etching, so that the metal W at the bottom will be damaged, which will bring certain stability and reliability to the process. difficulty

according to Figure 5 The energy dispersive spectroscopy (EDS) map shown after bottom etching shows that the SiN layer prepared by the prior art will have obvious nitrogen residues after bottom etching

and Image 6 Then it shows the lead hole after over-etching, such as Image 6 The wire hole shown in the dotted box, due to over-etch, can cause wire connection errors and affect the electrical performance of the device

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