Selective etchant for 3D NAND structure sheets

Abstract

The present invention provides a selective etching solution for 3D NAND structure sheets. The etching solution includes phosphoric acid, silane additive 1, silane additive 2, and the remainder is water. The etching solution of the present invention has etching selectivity for silica film and silicon nitride film, can selectively remove silicon nitride film, improve the service life of the etching solution, and can be adapted to etching stacked structures.

Description

[Technical Field]

[0001] The present invention is in the field of electronic chemicals, and specifically relates to a selective etchant for silica and silicon nitride. [Background technology]

[0002] 3D NAND is a key process technology for flash memory chips. It uses vertical stacking technology to build more storage units in a smaller space, resulting in more storage data units, three times that of similar NAND technologies, and is also the current mainstream trend in development.

[0003] However, when etching a 192-layer 3D NAND structure with an etchant, due to the structure being an alternating layer of silica and silicon nitride, etching the silicon nitride while also slightly etching the silica. Therefore, the etchant must have high selectivity to silica, so that while etching the silicon nitride, it also slightly etches the silicon oxide. During the etching process, as the silicic acid content in the solution increases, once a certain silicon content is reached, silicon redeposition occurs in the silica layer, simultaneously increasing the grain size of the wafer surface, resulting in poor electrical performance and reduced chip yield.

[0004] To solve the above problem, it is necessary to add a composite additive to phosphoric acid, which can inhibit and stabilize the etching of silica with increasing silicon content, reduce the re-deposition of silica on the surface, and at the same time maintain the etching rate of silicon nitride. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a selective etching solution for silica and silicon nitride that can suppress and stabilize the etching of silica with increasing silicon content, reduce the surface redeposition of silica, and at the same time maintain the etching rate of silicon nitride, and is suitable for NAND structures.

[0006] In one aspect, the present invention relates to a selective etching solution for silica and silicon nitride, the composition of the etching solution comprising 1.5 to 2.0 mass % of silane. Coupling Agent 1. 2.0 to 2.5 mass% silane Coupling Agent 2. The content is 83 to 86 mass% phosphoric acid, the remainder is water.

[0007] In the selective etching solution according to the present invention, the silane coupling agent 1 is any one of 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-epoxypropyloxypropyl)silane.

[0008] The main function of silane coupling agent 1 is to adjust the selectivity between silicon nitride and silica. Its mechanism of action is the hydrolysis of the silane coupling agent in phosphoric acid, which allows the chemical bond of the silicon-oxy-silicon structure to attach to the silica surface. At the same time, the larger the terminal group, the greater the steric hindrance effect, which prevents the etching of the silica surface by phosphoric acid and water. Thus, the synergistic effect of the two effects inhibits the etching of silica.

[0009] In the selective etching solution according to the present invention, the silane coupling agent 2 is any one of 2-cyanoethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

[0010] The main function of Silane Coupling Agent 2 is to prevent silicic acid from re-adhering to the silica surface. Through hydrolysis of the carbon-nitrogen bond, it forms chemical bonds such as hydroxyl and carboxyl groups, which are highly water-soluble. This allows Silane Coupling Agent 2 to bond with silicic acid and prevent it from re-adhering to the silica surface. Silane Coupling Agent 1 can effectively adhere to the silica surface, making it easier to adhere to the silica surface after bonding with silicic acid. Furthermore, Silane Coupling Agent 2 can interact with Silane Coupling Agent 1, reducing its ability to adhere to the silica surface. When the silicon content in the solution is high, silica etching can also achieve a positive etching effect.

[0011] In the etching solution of the present invention, the content of phosphoric acid and water has a significant effect on the initial etching rate of silica and silicon nitride, that is, the higher the content of phosphoric acid, the lower the content of water, and the faster the etching rate of silica.However, if the concentration of phosphoric acid is too high, it will easily cause dehydration and carbonization of the silane coupling agent, making it ineffective, and the etching rate of silica will increase too quickly, and if the concentration of phosphoric acid is too low, it will not meet the need for a stable content of high-temperature etching water.

[0012] The mass ratio of phosphoric acid to water in the etching solution according to the present invention is 6 to 8, and preferably 7 to 7.5.

[0013] The 3D NAND structure sheet has a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer has a thickness of 500 to 1000 Å, the silica film layer has a thickness of 50 to 500 Å, and the number of layers in the laminated structure is 150 to 250.

[0014] In another aspect, the present invention provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: Silane coupling agent 1 and 2 and a method for preparing a selective etching solution for 3D NAND structure sheets, comprising: uniformly mixing the above at room temperature and adding them together to a phosphoric acid solution to obtain an etching solution.

[0015] Preheat the phosphoric acid solution to 80-100°C. Silane coupling agent 1 and 2 After uniformly mixing, both are added to a phosphoric acid solution at 80 to 100°C, then heated again to 110 to 120°C, kept at that temperature for 0.5 to 1 hour, and cooled to room temperature to obtain an etching solution.

[0016] In the preparation process, when the preparation is carried out under room temperature conditions, the gel mass phenomenon is easily achieved, Silane coupling agent 1 and 2 After uniformly mixing, add to the phosphoric acid aqueous solution at room temperature, then slowly heat to 80-100°C, more preferably 80°C, 90°C, or 100°C. If the temperature is then increased to 110-120°C, the formed gel mass may not completely disappear and may be mixed into the resulting mixed solution. After further increasing the temperature to 110°C or 120°C, the formed etching solution is completely dissolved.

[0017] The aforementioned Silane coupling agent 1 The mass content of is 1.5 to 2.0%.

[0018] silane coupling agent 2 The mass content of is 2.0 to 2.5%.

[0019] The mass content of phosphoric acid is 83 to 86%, with the remainder being water, and the mass content ratio of phosphoric acid to water in the etching solution is 6 to 8, preferably 7 to 7.5.

[0020] The silane Coupling Agent 1 is any one of 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-epoxypropyloxypropyl)silane.

[0021] The silane Coupling Agent 2 is any one of 2-cyanoethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

[0022] The 3D NAND structure sheet has a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer has a thickness of 500 to 1000 Å, the silica film layer has a thickness of 50 to 500 Å, and the number of layers in the laminated structure is 150 to 250.

[0023] In another aspect, the present invention provides a method for etching a 3D NAND structure sheet using a selective etching solution for the 3D NAND structure sheet, which is characterized by etching a stacked structure of a silica film and a silicon nitride film in the selective etching solution at an operating temperature of 156 to 164°C, more preferably 160±0.5°C. With the etching solution of the present invention, as the temperature increases, the etching rates of both silicon nitride and silica increase, but the etching rate of silica increases more than that of silicon nitride, and the etching selectivity decreases. As the temperature decreases, the selectivity increases, but silica becomes more susceptible to redeposition.

[0024] The selective etching solution contains the following ingredients:

[0025] The aforementioned Silane coupling agent 1 The mass content of is 1.5 to 2.0%.

[0026] silane coupling agent 2 The mass content of is 2.0 to 2.5%.

[0027] The mass content of phosphoric acid is 83 to 86%, with the remainder being water, and the mass content ratio of phosphoric acid to water in the etching solution is 6 to 8, preferably 7 to 7.5.

[0028] The silane Coupling Agent 1 is any one of 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-epoxypropyloxypropyl)silane.

[0029] The silane Coupling Agent2 is any one of 2-cyanoethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

[0030] The 3D NAND structure sheet has a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer has a thickness of 500 to 1000 Å, the silica film layer has a thickness of 50 to 500 Å, and the number of layers in the laminated structure is 150 to 250.

[0031] The silicon content in the etching process is 0 to 500 ppm.

[0032] When the content of added silicon in the etching solution is 0 ppm, the etching rate of silicon nitride is more than 2000 Å / 30 min, the etching rate of silica is less than 0.8 Å / 30 min, and the etching rate selectivity of silicon nitride / silica is more than 2500.

[0033] When the content of added silicon in the etching solution is 300 ppm, the etching rate of silicon nitride exceeds 1800 Å / 30 min, and the etching rate of silica exceeds 0.3 Å / 30 min.

[0034] In the present invention, etching experiments are carried out by slicing silica and silicon nitride to verify the etching effect of a selective etching solution.

[0035] In the present invention, in order to verify the etching effect of the selective etching solution, silica and silicon nitride are sliced ​​and an etching experiment is performed.

[0036] All of the reagents and raw materials used in the present invention can be purchased commercially.

[0037] In accordance with common knowledge in the art, the above-mentioned preferred conditions can be combined to provide a more excellent example of the etching effect of the present invention.

[0038] The advantage of the present invention, compared to the prior art, is that the present invention provides an etching solution that is selective to silicon nitride and silica and inhibits etching of silica while at the same time having a long etching life.

[0039] (1) The initial etching rate of the etching solution of the present invention for silicon nitride exceeds 2000 Å / 30 min, and the etching selectivity exceeds 2500.

[0040] (2) The etching solution of the present invention extends the etching life and silicon content window of the solution through the hydrolysis group with good water solubility, and achieves a positive silica etching effect mainly by preventing the redeposition of silicic acid. At a silicon content of 300 ppm, the etching rate of silicon nitride exceeds 1800 Å / 30 min, and the etching rate of silica exceeds 0.3 Å / 30 min.

[0041] (3) The etching solution of the present invention is used to etch a 192-layer 3D NAND structure sheet, and the toothed structure is clear and complete, there is no adhesion between layers, and there is no redeposition on the silica layer with a silicon content of 300 ppm. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 is an SEM image of the 3D NAND structure sheet of Example 3 after etching when the silicon content is 0 ppm.

[0043] [Figure 2] FIG. 2 is an SEM image of the 3D NAND structure sheet of Example 3 after etching when the silicon content is 100 ppm.

[0044] [Figure 3] FIG. 3 is an SEM image of the 3D NAND structure sheet of Example 3 after etching when the silicon content is 200 ppm.

[0045] [Figure 4] FIG. 4 is an SEM image of the 3D NAND structure sheet of Example 3 after etching when the silicon content is 300 ppm.

[0046] [Figure 5] FIG. 5 is an SEM image of the 3D NAND structure sheet of Comparative Example 1 after etching when the silicon content is 300 ppm. DETAILED DESCRIPTION OF THE INVENTION

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention, and the above embodiments are only some of the embodiments of the present invention, not all of the embodiments. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present invention without any creative efforts fall within the scope of protection of the present invention.

[0048] 1. Preparation of etching solution

[0049] Silane coupling agents 1 and 2 are mixed uniformly at room temperature, and then added to an approximately 86.5% aqueous solution of phosphoric acid at 80°C. After the silane coupling agents are completely dissolved in the phosphoric acid, the mixture is heated to 120°C and kept at this temperature for 1 hour, and then cooled to room temperature.

[0050] 2. Etching experiment

[0051] 2.1 Etching rate detection method

[0052] Wafer etching: The deposition thicknesses of the two film materials on the silicon semiconductor wafer, silica film and silicon nitride film, are 300 Å and 1000 Å, respectively, and the wafer is sliced ​​into 1.5 cm x 3 cm strips for the experiment.

[0053] Etching temperature: 160±0.5℃.

[0054] Etching time: Silica film is etched for 3600 s, and silicon nitride film is etched for 300 s.

[0055] Etching rate calculation method: Using ellipsometry, measure the thickness of the silica and silicon nitride films before and after etching, and divide the difference between the initial and post-etching thicknesses by the etching time, i.e., the etching rate. The etching selectivity is the ratio of the silicon nitride etching rate (SiN E / R) to the silica etching rate (SiO E / R).

[0056] 2.2 Method for detecting etching service life

[0057] During etching of the silicon nitride layer, the silicon content in the etching solution is gradually increased to inhibit the etching of silica and silicon nitride. The initial silicon content of the etching solution is 0 ppm, and silicon nitride is dissolved therein to prepare etching solutions with silicon contents of 100 ppm, 200 ppm, and 300 ppm, and the etching rates and selectivities of silica and silicon nitride are tested respectively to characterize the service life of the etching solution.

[0058] 2.3 Etching test of laminated structure

[0059] Etching experiment: The 3D NAND structure sheet was etched using etching solutions with silicon contents of 0 ppm, 100 ppm, 200 ppm, and 300 ppm, respectively. The etching conditions were the same as those for speed detection, and the etching time was 20 min.

[0060] Detection method: The etching effect and redeposition status are analyzed by taking high-resolution SEM images of the cross section of the 3D NAND structure sheet.

[0061] Examples 1 to 11 and Comparative Examples 1 to 7 are shown in Table 1, where the contents of phosphoric acid and silane coupling agent are expressed as mass percent, with the remainder being water.

[0062] [Table 1] TIFF0007777685000001.tif210170

[0063] When the initial silicon content was set to 0 ppm, the etching rates and selectivity ratios of the etching solutions in Examples 1 to 11 and Comparative Examples 1 to 7 for the silica film and the silicon nitride film are shown in Table 2.

[0064] [Table 2] TIFF0007777685000002.tif114170

[0065] In the experiment of Example 11, the boiling point was low, the boiling conditions were unstable, and the heating time was long, causing some of the water to evaporate at the same time, so the experimental conditions did not reach a stable state. The initial selectivity of Example 10 did not meet the corresponding requirements, and it was more preferable to use the ratio of Example 1, and the entire experiment was mainly centered on the ratio of Example 1.

[0066] When the silicon content was set to 100 ppm, the etching rates and selectivity ratios of the etching solutions in Examples 1 to 9 and Comparative Examples 1 to 7 for the silica film and silicon nitride film are shown in Table 3.

[0067] [Table 3] TIFF0007777685000003.tif103170

[0068] When the silicon content was set to 200 ppm, the etching rates and selectivity of the etching solutions in Examples 1 to 9 and Comparative Examples 1 to 7 for the silica film and silicon nitride film are shown in Table 4.

[0069] [Table 4] TIFF0007777685000004.tif103170

[0070] NOTE: Negative numbers indicate the rate at which the silica film thickens when the silicon content is high.

[0071] When the silicon content was set to 300 ppm, the etching rates and selectivity of the etching solutions in Examples 1 to 9 and Comparative Examples 1 to 7 for the silica film and silicon nitride film are shown in Table 4.

[0072] [Table 5] TIFF0007777685000005.tif103170

[0073] From the above experimental data, it can be seen that silane coupling agent 1 in Comparative Examples 1 to 3 has a high initial selectivity, but with a continuous increase in silicon content, its silica etching rate rapidly decreases, and redeposition occurs when the silicon content reaches 300 ppm. Silane coupling agent 2 in Comparative Examples 4 to 6 does not have a good initial selectivity, but with a continuous increase in silicon content, positive etching is maintained. Examples 1 to 9 combine the advantages of the two silane coupling agents, and when the silicon content is 0 to 300 ppm, the silica etching rate is maintained at 0.3 to 0.8 Å / 30 min, and the silicon nitride etching rate is maintained at 1800 to 2100 Å / 30 min, and redeposition does not occur. In Examples 10 and 11, the mass fraction ratio of phosphoric acid to water is adjusted. When the mass ratio of phosphoric acid to water is less than 7, the boiling state of the solution in Example 11 is unstable during the etching process, which is not suitable for practical use. When the mass ratio of phosphoric acid to water is greater than 8, the etching speed of silica in Example 10 is too fast, and the selectivity cannot meet the requirements of this patent. Therefore, the ratio should preferably be 7-7.5 to ensure stable etching results.

[0074] From the SEM images of the structure sheet, it can be seen that in Example 3, when the silicon content was 300 ppm, the 192-layer 3D NAND structure sheet after etching appeared as a transparent toothed structure without adhesion, and there was no re-deposition reduction on the silica layer, which is clearly improved compared to the results of pure phosphoric acid etching. Furthermore, the other examples all achieved similar etching results for the structure sheet when the silicon content was 0 to 300 ppm. The diagrams for Examples 1, 2, and 3-9 are similar to the diagram for Example 3. The diagrams for Comparative Examples 1-3, when the silicon content was 300 ppm, are similar to the diagram for Comparative Example 1.

[0075] Although the selective etching solution for silica and silicon nitride of the present invention has been described in detail above, the above content is merely a specific example of the present invention and is not intended to limit the scope of protection of the present invention. It will be apparent to those skilled in the art that some modifications or improvements can be made to the present invention based on the present invention. Therefore, as long as they do not deviate from the spirit of the present invention, all such modifications and improvements are within the scope of protection claimed by the present invention.

Claims

1. In parts by mass, 1.5 to 2.0% of a silane coupling agent 1, 2.0 to 2.5% of a silane coupling agent 2, It contains 83-86% phosphoric acid and the rest water. The silane coupling agent 1 is any one of 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-epoxypropyloxypropyl)silane; The selective etching solution for a 3D NAND structure sheet, wherein the silane coupling agent 2 is any one of 2-cyanoethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

2. 2. The selective etching solution for 3D NAND structure sheets according to claim 1, wherein the mass ratio of phosphoric acid to water in the etching solution is 6 to 8.

3. 2. The selective etching solution for a 3D NAND structure sheet according to claim 1, wherein the 3D NAND structure sheet has a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer having a thickness of 500 to 1000 Å, the silica film layer having a thickness of 50 to 500 Å, and the number of layers in the laminated structure being 150 to 250.

4. Silane coupling agents 1 and 2 were mixed uniformly at room temperature and added to the phosphoric acid solution. The phosphoric acid solution is preheated to a temperature of 80-100°C, and silane coupling agents 1 and 2 are mixed uniformly. Both are then added to the 80-100°C phosphoric acid solution, which is then heated again to 110-120°C, kept at this temperature for 0.5-1 hour, and cooled to room temperature. The mass content of the silane coupling agent 1 is 1.5 to 2.0%; The mass content of the silane coupling agent 2 is 2.0 to 2.5%; the mass content of phosphoric acid is 83 to 86%, the remainder being water, and the mass ratio of phosphoric acid to water in the etching solution is 6 to 8; The silane coupling agent 1 is any one of 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-epoxypropyloxypropyl)silane; The method for preparing a selective etching solution for a 3D NAND structure sheet, wherein the silane coupling agent 2 is any one of 2-cyanoethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

5. 5. The method of claim 4, wherein the 3D NAND structure sheet is a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer has a thickness of 500-1000 Å, the silica film layer has a thickness of 50-500 Å, and the number of layers in the laminated structure is 150-250.

6. Etching the stack of silica and silicon nitride films in a selective etchant at an operating temperature of 156-164°C; Selective etchants include: a silane coupling agent 1 having a mass content of 1.5 to 2.0%; a silane coupling agent 2 having a mass content of 2.0 to 2.5%; It contains 83-86% by mass of phosphoric acid, the rest being water. the mass ratio of phosphoric acid to water in the etching solution is 6 to 8; The silane coupling agent 1 is any one of 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-epoxypropyloxypropyl)silane; the silane coupling agent 2 is any one of 2-cyanoethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane; the 3D NAND structure sheet has a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer has a thickness of 500 to 1000 Å, the silica film layer has a thickness of 50 to 500 Å, and the laminated structure has 150 to 250 layers.

7. 7. The method of claim 6, wherein the 3D NAND structure sheet is a laminated structure of a silica film and a silicon nitride film, the silicon nitride film layer has a thickness of 500-1000 Å, the silica film layer has a thickness of 50-500 Å, and the number of layers in the laminated structure is 150-250.

8. The silicon content during the etching process is 0-500 ppm; When the content of additional silicon in the etching solution is 0 ppm, the etching rate of silicon nitride is more than 2000 Å / 30 min, the etching rate of silica is less than 0.8 Å / 30 min, and the etching rate selectivity of silicon nitride / silica is more than 2500; 8. The method of claim 7, wherein when the content of additional silicon in the etching solution is 300 ppm, the etching rate of silicon nitride is greater than 1800 Å / 30 min, and the etching rate of silica is greater than 0.3 Å / 30 min.

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