Silicon nitride etching solution, preparation method and application thereof
By using an etching solution containing fluorinated reagents and silane coupling agents in a hydrofluoric acid system, the problems of insufficient selectivity and rate in silicon nitride etching in the prior art are solved, achieving high selectivity and high etching rate, suitable for silicon nitride thin film etching of 3D NAND memory.
Patent Information
- Application Number
- CN202511015719.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-10-28
AI Technical Summary
Existing silicon nitride etching solutions are insufficient in terms of etching selectivity and rate, especially in the multilayer stacked structure of 3D NAND memory, where it is difficult to effectively remove silicon nitride films.
An etching solution containing a fluorinating agent and a silane coupling agent, with a ratio of 0.01%-1% fluorinating agent, 0.1%-10% silane coupling agent and water, is used to etch silicon nitride films in a hydrofluoric acid system to achieve high selectivity and high etching rate.
The etching rate ratio of silicon nitride to silicon oxide reached (45-900):1, especially (280-810):1, which significantly improved the etching efficiency.
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Abstract
Description
Technical Field
[0001] This invention relates to a silicon nitride etching solution, its preparation method, and its application. Background Technology
[0002] NAND flash memory is a superior storage device compared to hard disk drives. With the pursuit of low-power, lightweight, and high-performance non-volatile storage products, NAND flash memory has been widely used in electronic products. Currently, the storage capacity of planar NAND flash memory is nearing its practical expansion limit. To further increase storage capacity and reduce the cost per bit, 3D (three-dimensional) NAND memory has been proposed. In 3D NAND memory structures, a stacked 3D NAND memory structure is achieved by vertically stacking multiple layers of data storage cells. This stacked structure includes alternately grown silicon nitride and silicon oxide films, and selective etching or selective corrosion of these alternating layers to form the desired structure. Currently, the nitride layer is selectively removed using a wet etching process, with the selective etching solution typically consisting of a high concentration of phosphoric acid and deionized water. However, this selective etching solution composition is not ideal in terms of etching rate selectivity. Furthermore, the more layers stacked in the NAND, especially from 32 to 128 layers, the more difficult it is to selectively etch the silicon nitride film. Summary of the Invention
[0003] The technical problem this invention aims to solve is to overcome the low selectivity and slow etching rate of existing etching solutions. This invention provides a silicon nitride etching solution, its preparation method, and its applications. The silicon nitride etching solution provided by this invention, in a hydrofluoric acid system, can achieve a high etching selectivity and a high silicon nitride etching rate.
[0004] The present invention solves the above-mentioned technical problems through the following technical solutions.
[0005] This invention provides an etching solution comprising the following components by mass fraction: 0.01%-1% fluorinating agent, 0.1%-10% silane coupling agent, and water; the sum of the mass fractions of each component is 100%; the mass fractions are the percentage of each component's mass relative to the total mass of all components.
[0006] Wherein, the silane coupling agent is ;
[0007] R 1 、R 2 and R 3 Each is independently H, -OH, or Cl-C. 10 Alkyl, C1-C 10 Alkyl group, -NH2, -COOH or -NHC(O)NH2, and R1 、R 2 and R 3 At least one of them is C1-C 10 Alkyl group.
[0008] In one aspect of the present invention, R 1 、R 2 and R 3 Each can be independently methoxy, ethoxy, propoxy, butoxy, isobutoxy, tert-butoxy, -NH2, or -COOH.
[0009] In one embodiment of the present invention, the silane coupling agent is... .
[0010] In one embodiment of the present invention, the fluorinating agent is selected from one or more of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, fluoroaluminic acid, fluoroboric acid and fluorosilicic acid, preferably hydrofluoric acid.
[0011] In one aspect of the present invention, the water is conventional water in the art, preferably deionized water.
[0012] In one embodiment of the present invention, the mass fraction of the fluorinating agent is 0.049%-0.49%, preferably 0.049%-0.147%, more preferably 0.045%-0.052%, and most preferably 0.049%.
[0013] In one embodiment of the present invention, the mass fraction of the silane coupling agent is 0.1%-3%, preferably 1%-3%, more preferably 2.7-3.2%, and most preferably 3%.
[0014] In one embodiment of the present invention, the mass fraction of the fluorinating agent is 0.049%-0.147%; the mass fraction of the silane coupling agent is 0.1%-3%; and the silane coupling agent is... Preferably, the fluorinating agent has a mass fraction of 0.045-0.052%; and the silane coupling agent has a mass fraction of 1%-3%.
[0015] In one embodiment of the present invention, the etching solution is composed of the following components: 0.01%-1% of a fluorinating agent, 0.1%-10% of a silane coupling agent, and water.
[0016] In one aspect of the present invention, the etching solution is composed of any of the following formulations:
[0017] Formula A: 0.49% hydrofluoric acid, 10%... and 89.51% water;
[0018] Formula B: 0.147% hydrofluoric acid, 3% And 96.853% water;
[0019] Formula C: 0.049% hydrofluoric acid, 3% And 96.951% water;
[0020] Formula D: 0.049% hydrofluoric acid, 1% And 98.951% water;
[0021] Formula E: 0.049% hydrofluoric acid, 0.1% And 99.851% water.
[0022] The present invention also provides a method for preparing an etching solution as described in any embodiment of the present invention, comprising the following steps: mixing the fluorinating reagent, the silane coupling agent and water to obtain the etching solution; wherein the mass fraction of each component is as described in any embodiment of the present invention.
[0023] The present invention also provides the application of the etching solution as described in any embodiment of the present invention in etching silicon nitride thin films.
[0024] In one aspect of the invention, the silicon nitride film is, for example, a silicon nitride film in 3DNAND.
[0025] In one aspect of the present invention, the etching temperature is 60-95°C, preferably 90°C.
[0026] In one aspect of the present invention, in the application, the etching rate ratio of the etching solution to silicon nitride and silicon oxide is (45-900):1, for example (80-810):1, preferably (280-810):1, and more preferably 810:1.
[0027] In this invention, room temperature refers to ambient temperature, such as 15-35℃.
[0028] Without violating common sense in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.
[0029] The reagents and raw materials used in this invention are all commercially available.
[0030] The positive and progressive effects of this invention are as follows: the silicon nitride etching solution provided by this invention can achieve a high etching selectivity and a high silicon nitride etching rate in a hydrofluoric acid system. Detailed Implementation
[0031] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.
[0032] Preparation Examples 1-5 and Comparative Example 1
[0033] Preparation of etching solution
[0034] Raw materials for preparation: hydrofluoric acid aqueous solution (concentration 49%), silane coupling agent, and deionized water; wherein the structural formula of the silane coupling agent is as follows: .
[0035] Preparation method: At room temperature, add hydrofluoric acid aqueous solution, silane coupling agent and deionized water to a container according to the amount of each raw material component in Table 1, and stir mechanically at room temperature until uniform to obtain etching solution.
[0036] Table 1. Feed amounts of each raw material component of the etching solution
[0037]
[0038] Application Examples
[0039] The etching solutions described in Examples 1-5 and Comparative Example 1 were applied to silicon nitride etching.
[0040] 1. Etching selectivity:
[0041] (1) Silicon nitride etching rate
[0042] Etching rate test sample: SIN wafer, 40*40mm.
[0043] Etching conditions: 90±2℃.
[0044] Etching time: 10 minutes;
[0045] Etching container: Quartz tank etching machine.
[0046] Speed measurement method:
[0047] Etching rate: The thickness of the sample was measured before and after etching using a thin film thickness measuring device (UNICORN TECHNOLOGY, F50). The etching rate was calculated by dividing the difference between the initial thickness and the thickness after etching by the etching time (minutes).
[0048] (2) Silicon oxide etching rate
[0049] Etching rate test sample: TEOS wafer, 40*40mm.
[0050] Etching conditions: 90±2℃.
[0051] Etching time: 30 minutes;
[0052] Etching container: Quartz tank etching machine.
[0053] Speed measurement method:
[0054] Etching rate: The thickness of the sample was measured before and after etching using a thin film thickness measuring device (UNICORN TECHNOLOGY, F50). The etching rate was calculated by dividing the difference between the initial thickness and the thickness after etching by the etching time (minutes).
[0055] (3) Selectivity: Selectivity represents the ratio of silicon nitride etching rate to silicon oxide etching rate.
[0056] The etching rates of etching solutions 1-5 in Examples 1-5 and 1-2 in Comparative Examples 1-2 are shown in Table 2.
[0057] Table 2
[0058]
Claims
1. An etching solution, characterized in that, It comprises the following components by mass fraction: 0.01%-1% fluorinating agent, 0.1%-10% silane coupling agent, and water; the sum of the mass fractions of all components is 100%. Wherein, the silane coupling agent is ; R 1 、R 2 and R 3 Each is independently H, -OH, or Cl-C. 10 Alkyl, C1-C 10 Alkyl group, -NH2, -COOH or -NHC(O)NH2, and R 1 、R 2 and R 3 At least one of them is C1-C 10 Alkyl group.
2. The etching solution as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) R 1 、R 2 and R 3 Each can be independently methoxy, ethoxy, propoxy, butoxy, isobutoxy, tert-butoxy, -NH2, or -COOH; (3) The fluorinating agent is selected from one or more of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, fluoroaluminic acid, fluoroboric acid and fluorosilicic acid, preferably hydrofluoric acid; (4) The water mentioned is deionized water; (5) The mass fraction of the fluorinating agent is 0.049%-0.49%, preferably 0.049%-0.147%, more preferably 0.045%-0.052%, and most preferably 0.049%; (6) The mass fraction of the silane coupling agent is 0.1%-3%, preferably 1%-3%, more preferably 2.7-3.2%, and most preferably 3%.
3. The etching solution as described in claim 2, characterized in that, The silane coupling agent is .
4. The etching solution as described in claim 1, characterized in that, The fluorinating agent has a mass fraction of 0.049%-0.147%; the silane coupling agent has a mass fraction of 0.1%-3%; the silane coupling agent is... .
5. The etching solution as described in claim 4, characterized in that, The fluorinating agent has a mass fraction of 0.045-0.052%; the silane coupling agent has a mass fraction of 1%-3%.
6. The etching solution as described in claim 1, characterized in that, The etching solution consists of the following components: 0.01%-1% fluorinating agent, 0.1%-10% silane coupling agent, and water.
7. The etching solution as described in claim 1, characterized in that, The etching solution is composed of any of the following formulations: Formula A: 0.49% hydrofluoric acid, 10%... and 89.51% water; Formula B: 0.147% hydrofluoric acid, 3% And 96.853% water; Formula C: 0.049% hydrofluoric acid, 3% And 96.951% water; Formula D: 0.049% hydrofluoric acid, 1% And 98.951% water; Formula E: 0.049% hydrofluoric acid, 0.1% And 99.851% water.
8. A method for preparing an etching solution as described in any one of claims 1-7, characterized in that, It includes the following steps: The fluorinating agent, the silane coupling agent, and water are mixed to obtain the etching solution; The mass fraction of each component is as described in any one of claims 1-7.
9. The use of an etching solution as described in any one of claims 1-7 in etching silicon nitride thin films.
10. The application as described in claim 9, characterized in that, It satisfies one or more of the following conditions: (1) The silicon nitride film is the silicon nitride film in 3DNAND; (2) The etching temperature is 60-95℃, preferably 90℃; (3) The etching rate ratio of the etching solution to silicon nitride and silicon oxide is (45-900):1, for example (80-810):1, preferably (280-810):1, and more preferably 810:1.