3D NAND deep hole structure etching solution
By using a mixture of formamidin and pyridine or pyridine derivatives with phosphoric acid, the etching rate was adjusted, solving the problem of the mismatch between the bottom and top etching rates in the deep hole etching of 3D NAND flash memory chips. This resulted in a uniform etching effect and improved chip performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUBEI SINOPHORUS ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2025-12-22
- Publication Date
- 2026-04-28
AI Technical Summary
Existing technologies struggle to match the etching rates at the bottom and top in deep-hole etching of 3D NAND flash memory chips, resulting in poor etching morphology and impacting chip performance.
A 3D NAND deep hole structure etching solution is used, which is a mixed solution of formamidine, pyridine or pyridine derivatives, phosphoric acid and ultrapure water. By adjusting the etching rate, the etching rate at the top is made greater than that at the bottom, forming an etching morphology that is narrow at the bottom and wide at the top.
It achieves a higher top etching rate than bottom etching rate during the wet etching process of 3D NAND memory chips, resulting in a complete and uniform deep hole structure. The etching rate has good stability and is suitable for deep hole structures with aspect ratios of 100-2000.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electronic chemicals, specifically relating to a 3D NAND deep hole structure etching solution and its application. Background Technology
[0002] Since Toshiba Memory invented NAND flash memory in 1987, NAND flash memory has undergone technological evolution from two-dimensional to three-dimensional. Samsung, as the creator of 3D NAND flash memory, still holds the top position in both technology and production capacity. NAND stands for "NOTAND," meaning a circuit unit that performs NAND logic operations.
[0003] In flash memory chip technology, 3D NAND technology vertically stacks multiple layers of data storage cells, accommodating more storage cells in a smaller space. Its process has progressed from 128 layers to stacked structures of over 300 layers. When the aspect ratio of the stacked structure exceeds a certain value, plasma etching cannot achieve a vertical etching pattern at the bottom of the deep via, thus affecting chip performance. In deep via etching, most etching solutions can only achieve a bottom-wide, top-narrow etching morphology, and very few solutions can achieve parallel etching. However, with the increasing number of Si3N4 / SiO2 layers in the development of 3D NAND, the deep via morphology has an increasingly significant impact on flash memory chip performance.
[0004] To address the above problems, it is necessary to develop an etching solution that alters the etching morphology, specifically an etching solution with a narrow bottom and a wide top. Summary of the Invention
[0005] To address the above problems, this invention provides a 3D NAND deep hole structure etching solution and its application. The 3D NAND deep hole structure etching solution is suitable for etching deep hole structures.
[0006] To achieve the above objectives, the present invention provides a 3D NAND deep-hole etching solution, wherein the deep-hole etching solution is composed of a formamidinium-based substance, pyridine or pyridine derivatives, phosphoric acid, and ultrapure water, wherein: (1) Formamidines with a mass content of 1-15%; (2) 0.5-10% by mass of pyridine or pyridine derivatives; (3) Phosphoric acid with a mass content of 58-70% (85%); (4) The remainder is ultrapure water.
[0007] The formamidines include, but are not limited to, one or a combination of several of the following: 4-trifluoromethylbenzamidin, 3,4-difluorobenzamidin, 4-amino-2-fluorobenzamidin, p-chlorobenzamidin, and 2-chloro-4-fluorobenzamidin.
[0008] The pyridine or pyridine derivatives include one or a combination of several of the following: 2,6-pyridinedicarboxaldehyde, 2-bromo-3-methoxypyridine, 4-pyridinepropanol, pyrrolidone, 2-benzoylpyridine, pyridine-2-sulfonic acid, 3-bromo-2-pyridinecarboxylic acid, 2-chloro-5-fluoronicotinic acid, and methyl 2-pyridineacetate.
[0009] Preferably, the phosphoric acid of the present invention has a mass fraction greater than 85%, and more preferably, the phosphoric acid is 85% phosphoric acid.
[0010] Preferably, the ultrapure water described in this invention is ultrapure water with a resistivity of 15-18 MΩ*cm at 25°C.
[0011] The method for preparing the etching solution includes the following steps: (1) Mix formamidin with water and set aside; (2) Add the hydrolysate from (1) to phosphoric acid and stir until homogeneous to obtain the etching solution.
[0012] The present invention also provides an application of a 3D NAND deep hole structure etching solution in 3D NAND deep hole structures.
[0013] Preferably, the aspect ratio of the deep hole structure is 100-2000; in some preferred cases, the aspect ratio is 500-2000; and in some preferred cases, the aspect ratio is 1000-2000.
[0014] Preferably, the etching temperature is 20-65℃.
[0015] The beneficial effects of this invention are as follows: 1. In the wet etching process of 3D NAND memory chips, side etching sometimes occurs, which causes the etching rate at the bottom to be greater than that at the top. This etching solution can effectively solve this problem by adding formamidin-like substances to make the top etching rate greater than the bottom etching rate.
[0016] 2. Pyridine or pyridine derivatives partially complex with the precipitated silicic acid in solution, preventing silicic acid agglomeration, enhancing its diffusion performance in deep-pore structures, preventing the reaction products from inhibiting etching, and ensuring that the top etching rate in deep-pore structures is greater than the bottom etching rate, thus ultimately achieving the effect that the top etching rate is greater than the bottom etching rate. 3. The 3D NAND deep-hole structure etching solution prepared by this invention exhibits an initial etching rate greater than 5 A / min for silicon oxide wafers and greater than 5 A / min for silicon nitride wafers. When the added silicon content is 1000 ppm, the etching rate decreases by no more than 5% compared to the initial etching rate. When etching 3D NAND structure layers with deep holes (aspect ratio of 100-2000), it can etch a complete and uniform structure, with a difference in etching width between upper and lower layers exceeding 50%. Detailed Implementation
[0017] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.
[0018] (1) Etching wafers: The etching solution prepared according to the above ratio was used to etch silicon oxide and silicon nitride wafers on a silicon substrate at 30°C (the silicon oxide wafers and silicon nitride wafers were cut into regular rectangles with a size of 1*2cm); the oxide layer was first removed by cleaning with a hydrofluoric acid solution and isopropanol solution with a volume ratio of 200:1 for 30s, and then placed in the etching solution prepared in the example or comparative example to etch the deep hole structure of silicon nitride and silicon oxide; the etching temperature was 25±0.5°C and the etching time was 20min; (2) Calculation of etching rate: The thickness of silicon oxide and silicon nitride films before and after etching is detected by elliptic polarization spectrometer. The difference between the initial thickness and the thickness after a certain time is divided by the etching time to obtain the etching rate. (3) Etching experiment of the structural sheet (the structural sheet was cut into regular squares of 1*2cm). The etching conditions were the same as in (1). The etching rate was measured by the top etching amount divided by the etching time. The pore diameter of the deep hole structure layer was 50nm and the pore depth was 50μm. The etching effect was characterized after etching.
[0019] The specific formula is shown in Table 1 below: Table 1 Raw materials and formulation of 3D NAND deep hole structure etching solution
[0020] The preparation method for the etching solution is as follows: A hydrolysate is prepared by mixing formamidin, pyridine or pyridine derivatives with water for later use. The hydrolysate was added to phosphoric acid and stirred until homogeneous to obtain a 3D NAND deep hole structure etching solution.
[0021] Component content of each embodiment and comparative example: Example 1 It contains 78% phosphoric acid (85%), 10% 4-trifluoromethylbenzamide, 7% 2,6-pyridinedicarboxaldehyde, and the remainder is water.
[0022] Example 2 It contains 78% phosphoric acid (85%), 10% 3,4-difluorobenzomidine, 7% 2-bromo-3-methoxypyridine, and the remainder is water.
[0023] Example 3 It contains 78% phosphoric acid (85%), 10% 4-amino-2-fluorobenzomidine, 7% 4-pyridinepropanol, and the remainder is water.
[0024] Example 4 It contains 78% phosphoric acid (85%), 10% p-chlorobenzoamide, 7% pyrrolidone, and the remainder is water.
[0025] Example 5 It contains 78% phosphoric acid (85%), 10% 2-chloro-4-fluorobenzoamide, 7% 2-benzoylpyridine, and the remainder is water.
[0026] Example 6 It contains 78% phosphoric acid (85%), 10% 3,4-difluorophenylacetamidine, 7% pyridine-2-sulfonic acid, and the remainder is water.
[0027] Example 7 It contains 78% phosphoric acid (85%), 10% 3,4-difluorophenacetin, 7% 3-bromo-2-pyridinecarboxylic acid, and the remainder is water.
[0028] Example 8 It contains 78% phosphoric acid (85%), 10% 3-chloro-4-fluorobenzoamide, 7% 2-chloro-5-fluoronicotinic acid, and the remainder is water.
[0029] Example 9 It contains 78% phosphoric acid (85%), 10% 2,6-dichlorophenazine, 7% methyl 2-pyridine acetate, and the remainder is water.
[0030] Example 10 It contains 78% phosphoric acid (85%), 10% 4-benzylpiperazine-1-formamidinium, 7% 5-bromo-2-carboxypyridine, and the remainder is water.
[0031] Comparative Example 1 It contains 10% 3,4-difluorobenzomidine, 7% 4-pyridinepropanol, and the remainder is water.
[0032] Comparative Example 2 It contains 78% phosphoric acid (85%), 7% 4-pyridinylpropanol, and the remainder is water.
[0033] Comparative Example 3 It contains 10% phosphoric acid (85%), 10% 3,4-difluorobenzomidine, 7% 4-pyridinepropanol, and the remainder is water.
[0034] Comparative Example 4 It contains 83% phosphoric acid (85%), 10% 3,4-difluorobenzomididine, and 7% 4-pyridinepropanol.
[0035] Table 2. Etching effect of 3D NAND deep hole structure etching solution with different ratios.
[0036] The above provides a detailed description of a 3D NAND deep-hole structure etching solution according to the present invention. The above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Modifications or improvements can be made to the present invention, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A 3D NAND deep-hole structure etching solution, characterized in that, The 3D NAND deep hole structure etching solution contains the following raw materials: (1) Formamidines with a mass content of 1-15%; (2) 0.5-10% by mass of pyridine or pyridine derivatives; (3) Phosphoric acid with a mass content of 58-70%; (4) The remainder is ultrapure water.
2. The 3D NAND deep-hole structure etching solution according to claim 1, characterized in that: The formamidines include, but are not limited to, one or a combination of several of the following: 4-trifluoromethylbenzamidin, 3,4-difluorobenzamidin, 4-amino-2-fluorobenzamidin, p-chlorobenzamidin, and 2-chloro-4-fluorobenzamidin.
3. The 3D NAND deep-hole structure etching solution according to claim 1, characterized in that: The pyridine or pyridine derivatives include one or a combination of several of the following: 2,6-pyridinedicarboxaldehyde, 2-bromo-3-methoxypyridine, 4-pyridinepropanol, pyrrolidone, 2-benzoylpyridine, pyridine-2-sulfonic acid, 3-bromo-2-pyridinecarboxylic acid, 2-chloro-5-fluoronicotinic acid, and methyl 2-pyridineacetate.
4. The 3D NAND deep-hole structure etching solution according to claim 1, characterized in that: The electronic-grade phosphoric acid must have a metal ion content of ≤200 ppb and a phosphoric acid mass fraction greater than 85%.
5. The 3D NAND deep hole structure etching solution according to claim 1, characterized in that: The water in question is ultrapure water with a resistivity of 15-18 MΩ*cm at 25℃.
6. The method for preparing the 3D NAND deep hole structure etching solution according to any one of claims 1-5, characterized in that: The method for preparing the etching solution includes the following steps: (1) Mix formamidin, pyridine or pyridine derivatives and water to form a hydrolysate for later use; (2) Add the hydrolysate from (1) to phosphoric acid and stir until homogeneous to obtain 3D NAND deep hole structure etching solution.
7. The application of a 3D NAND deep hole structure etching solution as described in any one of claims 1-5 in deep hole structures.
8. The application as described in claim 6, characterized in that: The aspect ratio of the deep hole structure is 100-2000.