Amphiphilic ionic liquid, polysilicon etching solution containing the same, preparation method and application

Abstract

The present invention relates to an amphiphilic ionic liquid, and a polysilicon etching liquid containing the same, a preparation method and an application. The ionic liquid has both a hydrophilic polyhydroxyl group and a hydrophobic polyfluorine group. The polysilicon etching liquid comprises an amphiphilic ionic liquid, hydrofluoric acid, an oxidizing acid and ultrapure water as components. During multiple circulation filtration processes, the etching liquid of the present invention has no significant difference in surface tension and etching performance, has an excellent service life, and has an excellent etching selectivity ratio for polysilicon and silicon oxide stacks, and can be applied in the field of polysilicon etching of 3D flash memory chips.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor manufacturing technology, and in particular relates to an amphiphilic ionic liquid, and a polysilicon etching solution containing the amphiphilic ionic liquid, a preparation method and an application thereof. Background Art

[0002] In the process of storage technology development, semiconductor storage has the advantages of fast access speed, low power consumption, small size, and high reliability. It is widely used in electronic devices and is gradually replacing mechanical hard disks to become the mainstream storage. Among them, flash memory is gradually replacing mechanical hard disks to become the protagonist in the field of big data storage with its advantages of large storage capacity per unit area and fast rewriting speed. Its technological development is also moving towards the direction of continuously increasing storage capacity per unit area, from two-dimensional to three-dimensional, and then to continuously increasing the number of stacking layers.

[0003] In the 3D stacking process, the polysilicon needs to be etched away first to form grooves. Currently, polysilicon etching solution systems are mainly divided into alkaline or acidic systems. The etching of polysilicon by alkaline systems has problems such as slow etching rate, silicon crystal surface selectivity, and the generation of hillock-like morphology during the etching process, which increases the surface roughness. The acidic system can solve the above problems very well, but the hydrofluoric acid in the acidic system will preferentially etch the silicon dioxide layer, so it is an urgent problem to improve the selectivity ratio of silicon oxide to polysilicon in the acidic system. Summary of the invention

[0004] The technical problem solved by the present invention is that in polysilicon etching solution, the hydrofluoric acid system etching solution has a relatively low selectivity between silicon oxide and polysilicon during the etching process.

[0005] In view of the technical problems existing in the prior art, the present invention designs an amphiphilic ionic liquid, and a polysilicon etching solution containing the amphiphilic ionic liquid, a preparation method and an application thereof.

[0006] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0007] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0008] [The first technical solution]

[0009] In the first aspect, a technical solution of the present invention is to provide an amphiphilic ionic liquid compound. In the present invention, the amphiphilic ionic liquid is a compound of the following formula I:

[0010]

[0011] Wherein, R1, R2, R3, and R4 are independently selected from hydroxyl, C1-C6 branched or straight chain alkyl with hydroxyl, C2-C6 alkenyl with hydroxyl, C3-C6 cycloalkyl with hydroxyl, or C6-C10 aryl with hydroxyl;

[0012] n1, n2, n3, and n4 may be the same or different and may be any integer from 2 to 8.

[0013] Wherein, the "+" in the structural formula represents the positive charge on N, and the "-" represents the corresponding negative charge paired with the positive charge.

[0014] The C1-C6 branched or straight chain alkyl group with a hydroxyl group refers to a straight chain or branched chain alkyl group containing a hydroxyl group having 1 to 6 carbon atoms, such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxyisopropyl, hydroxybutyl, hydroxyisobutyl, and hydroxytert-butyl.

[0015] The C2-C6 alkenyl group having a hydroxyl group refers to an alkenyl group having 2 to 6 carbon atoms, such as a hydroxyvinyl group, a hydroxypropylene group, a hydroxybutylene group, and a hydroxypentenyl group.

[0016] The C3-C6 cycloalkyl group with a hydroxyl group refers to a cycloalkyl group containing a hydroxyl group having 3 to 6 carbon atoms, such as 1-hydroxycyclopropyl(alkane), 1-hydroxycyclobutyl(alkane), 1-hydroxycyclopentyl(alkane), and 1-hydroxycyclohexyl(alkane).

[0017] The C6-C10 aryl group having a hydroxyl group refers to a hydroxyl-containing aryl group having 6 to 10 carbon atoms, such as a phenol group.

[0018] Wherein, n1-4 represents the number of repeating units of methylene (-CH2-), which is any integer from 2 to 8, for example, 2, 3, 4, 5, 6, 7 or 8.

[0019] The inventors have found that the ionic liquid of formula I can be used in polysilicon etching solution in 3D memory chip technology. By including the ionic liquid, the polysilicon etching solution can etch polysilicon without adding ammonium fluoride, especially having a higher polysilicon to silicon oxide etching selectivity.

[0020] [Second technical solution]

[0021] In a second aspect, a technical solution of the present invention is to provide a method for preparing the amphiphilic ionic liquid of formula I.

[0022] The preparation reaction formula of the amphiphilic ionic liquid of formula I is as follows:

[0023]

[0024] The preparation method of the amphiphilic ionic liquid specifically comprises the following steps:

[0025] The alcohol amine compound (compound of formula II) is added to the solvent, stirred and preheated to 40-90°C, and then the halogen-containing alcohol substance (compound of formula III) is slowly added dropwise to react. After the reaction is completed, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium (compound of formula V) is added to the product (compound of formula IV) obtained by the reaction. After continuing the reaction for a period of time, the temperature is lowered and allowed to stand, and rotary evaporation is performed to obtain a crude amphiphilic ionic liquid. After the crude amphiphilic ionic liquid is purified and dried, the amphiphilic ionic liquid (compound of formula I) is obtained.

[0026] Furthermore, the preparation method of the amphiphilic ionic liquid specifically comprises the following steps:

[0027] S1: adding the compound of formula II to a solvent, stirring and preheating to 40-90° C., then slowly and uniformly dropping the compound of formula III into the reactor containing the compound of formula II, and reacting for a period of time to obtain the compound of formula IV;

[0028] S2: Add the compound of formula V to the compound of formula IV slowly and evenly, continue stirring the reaction for a period of time, finally cool down and let stand, and rotary evaporate to obtain the compound of formula I. After the compound of formula I is purified and dried, an amphiphilic ionic liquid is obtained.

[0029] Wherein, in formula III, X is selected from one of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0030] Furthermore, in formula III, X is preferably bromine.

[0031] Wherein, the definitions of R1, R2, R3, R4 and n in the compounds of formula II and III are the same as those in formula I, and are not further described herein.

[0032] Furthermore, in step S1, the solvent is an ester compound, an alcohol compound, a halogenated alkane, a halogenated aromatic hydrocarbon, etc., for example, it can be any one of ethyl acetate, methyl acetate, methanol, ethanol, n-propanol, isopropanol, n-butanol, chloroform, tetrachloromethane, chlorobenzene, dichlorobenzene, acetonitrile, and toluene.

[0033] The amount of the solvent used is not particularly strictly limited, and those skilled in the art can make appropriate selections and determinations according to actual needs (for example, appropriate determinations based on the convenience of the reaction), which will not be described in detail here.

[0034] Further, the mixture is preheated to 40-90°C with stirring, for example, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C.

[0035] Furthermore, the molar ratio of the alcoholamine compound (the compound represented by Formula II) to the halogen-containing alcohol substance (the compound represented by Formula III) is 1:1-2, for example, 1:1, 1:1.5 or 1:2.

[0036] Furthermore, the molar ratio of the alcoholamine compound (the compound represented by Formula II) to the halogen-containing alcohol substance (the compound represented by Formula III) is preferably 1:2.

[0037] Furthermore, the molar ratio of the compound of formula III to the lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide (the compound represented by formula V) is 1:1-2, for example, 1:1, 1:1.5 or 1:2.

[0038] Furthermore, the molar ratio of the compound of formula III to the lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide (the compound represented by formula V) is preferably 1:1.

[0039] Furthermore, the drop speed is not strictly limited, as long as the drop speed of the solution is ensured to be uniform. However, generally, the drop speed can be 5-20 drops / second, for example, 5 drops / second, 10 drops / second, 15 drops / second or 20 drops / second.

[0040] There is no strict limit on the reaction time, as long as the reaction can be completed. For example, the reaction endpoint can be determined by chromatography detection, which is a conventional technical means in the art and will not be described in detail here.

[0041] But generally, the reaction time can be usually 10-40 hours, for example, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours or 40 hours.

[0042] Further, the alcoholamine compound (the compound shown in Formula II) is selected from triethanolamine, N,N-dimethylisopropanolamine, N,N-diethylpropanolamine, triisopropanolamine, diethanolmonoisopropanolamine, hydroxyethyldiisopropanolamine, diisopropylethanolamine, N-isopropyldiethanolamine, N,N-dibenzylethanolamine, N-benzyl-N-methylethanolamine, N-butyldiethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, N-methyl-N-(N,N-dimethylaminoethyl)ethanolamine, N,N-dibutylethanolamine, and N-o-tolyldiethanolamine.

[0043] Furthermore, the alcoholamine compound (the compound represented by Formula II) is preferably triethanolamine.

[0044] Furthermore, the halogen-containing alcohol substance (the compound shown in Formula III) is selected from 2-bromoethanol, 1-bromo-2-propanol, 3-bromo-1-propanol, 2,3-dibromo-1-propanol, 1,3-dibromo-2-propanol, bromobutanol, 4-bromo-1-butanol, chloropropanol, 1,3-dichloro-2-propanol, 3-chloro-1-propanol, 2,3-dichloro-1-propanol, and 4-chlorobutanol.

[0045] Furthermore, the halogen-containing alcohol substance (the compound represented by formula III) is preferably 2-bromoethanol.

[0046] Furthermore, the compound of formula V is 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid imide lithium.

[0047] In the preparation method of the amphiphilic ionic liquid of the present invention, the specific methods of purification and drying are as follows:

[0048] A1: The compound of formula I is washed 1-5 times with ethyl acetate, acetonitrile and tetrahydrofuran, i.e., washed 1-5 times with ethyl acetate, 1-5 times with acetonitrile and 1-5 times with tetrahydrofuran, then rotary evaporated and dried in vacuo to obtain an amphiphilic ionic liquid.

[0049] Furthermore, the time for each washing in step A1 is not strictly limited as long as it can be sufficiently washed. For example, it can be 1 minute, 3 minutes, 5 minutes, 7 minutes, 9 minutes or 10 minutes. Those skilled in the art can make appropriate determinations based on actual conditions and will not be described in detail here.

[0050] Furthermore, the temperature of vacuum drying in step A1 is 60-90°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C. Those skilled in the art can make appropriate determinations based on actual conditions, which will not be described in detail here.

[0051] Furthermore, the time for vacuum drying in step A1 is not strictly limited, as long as it can be dried sufficiently, for example, it can be 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours. Those skilled in the art can make appropriate determinations based on actual conditions, and will not be described in detail here.

[0052] [The third technical solution]

[0053] In a third aspect, a technical solution of the present invention is to provide a use of the amphiphilic ionic liquid in a 3D flash memory chip.

[0054] The inventors have found that the amphiphilic ionic liquid of formula I can be used in the polysilicon etching solution of 3D flash memory chips. By including the amphiphilic ionic liquid, the polysilicon etching solution has excellent etching selectivity and stability.

[0055] [The fourth technical solution]

[0056] In a fourth aspect, a technical solution of the present invention is to provide a polysilicon etching solution containing an amphiphilic ionic liquid, the components of which include an amphiphilic ionic liquid, hydrofluoric acid, an oxidizing acid and ultrapure water; the mass ratio of the amphiphilic ionic liquid, hydrofluoric acid, oxidizing acid and ultrapure water is 0.1-5:1-20:5-30:70-95.

[0057] The mass fraction of the amphiphilic ionic liquid is 0.1-5 parts, for example, 0.1 parts, 0.2 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 4 parts or 5 parts.

[0058] The mass fraction of the hydrofluoric acid is 1-20 parts, for example, 1 part, 5 parts, 10 parts, 15 parts or 20 parts.

[0059] The oxidizing acid is selected from any one or more of nitric acid, perchloric acid, hypochlorous acid and sulfuric acid.

[0060] The mass parts of the oxidizing acid are 5-30 parts, for example, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts or 30 parts.

[0061] The mass proportion of the ultrapure water is 70-95 parts, for example, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or 95 parts.

[0062] The ultrapure water is deionized water with a resistance of ≥ 18 MΩ.

[0063] [Fifth technical solution]

[0064] In a fifth aspect, a technical solution of the present invention is to provide a method for preparing the above-mentioned polysilicon etching solution, wherein the preparation method is specifically:

[0065] Weigh the respective amounts of the components respectively, then add ultrapure water, hydrofluoric acid, oxidizing acid, and amphiphilic ionic liquid into the container in sequence, fully stir and dissolve, and finally filter to obtain the polysilicon etching solution.

[0066] Wherein, the filtration can be carried out using a 0.1-0.5 μm filter element.

[0067] [Sixth technical solution]

[0068] In a sixth aspect, a technical solution of the present invention is to provide a polysilicon etching solution containing an amphiphilic ionic liquid for etching a 3D memory chip.

[0069] [Seventh technical solution]

[0070] In a seventh aspect, a technical solution of the present invention is a method for treating a 3D memory chip using the polysilicon etching solution, comprising the following steps:

[0071] The polysilicon etching solution is added into the etching tank, and then the polysilicon etching solution is heated, and the 3D memory chip is immersed at 20-40° C. for 1-10 minutes. The immersed 3D memory chip is rinsed in ultrapure water at least twice, each time for not less than 30 seconds, and the polysilicon etching solution is used for the 3D memory chip.

[0072] The present invention provides an amphiphilic ionic liquid, and a polysilicon etching solution containing the amphiphilic ionic liquid, and a preparation method and application thereof, which have the following beneficial effects:

[0073] (1) The present invention synthesizes an amphiphilic ionic liquid, which has both a hydrophilic polyhydroxyl group and a hydrophobic polyfluoride group. Its amphiphilic properties can be used as a surfactant. At the same time, the polyfluoride group in the ring structure can play a good supporting role in the etching process due to its large steric hindrance. In addition, the quaternary ammonium structure of the polyhydroxyl group can replace ammonium fluoride and play a role in regulating the etching rate in the etching process.

[0074] (2) The etching solution of the present invention can be used in 3D storage chips. The ionic liquid designed by the present invention has a hydrophilic polyhydroxyl group and has better water solubility than existing surfactants (such as fluorocarbons). During multiple cycles of filtration, the existing surfactants are easily filtered out by water-based filter elements, while the amphiphilic ionic liquid of the present invention has almost no significant difference in surface tension and etching performance after multiple cycles of filtration, and has an excellent service life.

[0075] In summary, the polysilicon etching solution of the present invention has very good application prospects and large-scale industrial promotion potential in the field of 3D memory chip polysilicon etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 : is the infrared spectrum of the amphiphilic ionic liquid prepared in Preparation Example 1. DETAILED DESCRIPTION

[0077] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

[0078] About the preparation method of the amphiphilic ionic liquid of the present invention:

[0079] The components and molar ratios of the preparation examples 1-7 of the amphiphilic ionic liquid are shown in Table 1. The amphiphilic ionic liquid is prepared according to the following preparation method:

[0080] S1: Add the compound of formula II to an appropriate amount of ethanol solvent, preheat to 50°C with stirring, then slowly and uniformly drop the compound of formula III into the reactor containing the compound of formula II. After the dropwise addition is completed, heat to reflux temperature, stir and react for 24 hours to obtain the compound of formula IV;

[0081] S2: After cooling and stirring, add the compound of formula V (i.e., 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid imine lithium) dropwise to the compound of formula IV, stir at room temperature for 24 hours, and finally stand and filter to remove the precipitate, and rotary evaporate the filtrate to obtain a crude amphiphilic ionic liquid;

[0082] The crude amphiphilic ionic liquid obtained above was washed three times with acetonitrile, ethyl acetate and tetrahydrofuran, respectively, for 10 minutes each time, then rotary evaporated and vacuum dried at 85° C. for 12 hours to obtain the compound of formula I - amphiphilic ionic liquid.

[0083] The reaction equation for the amphiphilic ionic liquid of the present invention is as follows:

[0084]

[0085] R1, R2, R3, and R4 are independently selected from hydroxyl, C1-C6 branched or straight chain alkyl with hydroxyl, C2-C6 alkenyl with hydroxyl, C3-C6 cycloalkyl with hydroxyl, or C6-C10 aryl with hydroxyl;

[0086] n1, n2, n3, and n4 may be the same or different and may be any integer from 2 to 8.

[0087] X is selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0088] Wherein, the "+" in the structural formula represents the positive charge on N, and the "-" represents the corresponding negative charge paired with the positive charge.

[0089] Table 1: Preparation Examples 1 to 7 of Amphiphilic Ionic Liquids

[0090]

[0091] Preparation methods of polysilicon etching solutions of the present invention and comparative examples:

[0092] The components and molar ratios of polysilicon etching solutions in Examples 1-7 are shown in Table 2, and the components and molar ratios of polysilicon etching solutions in Comparative Examples 1-3 are shown in Table 3. According to Tables 2 and 3 below, the respective amounts of the components are weighed, and then ultrapure water, hydrofluoric acid, oxidizing acid, and amphiphilic ionic liquid are sequentially added to the container, stirred and dissolved, and finally filtered using a 0.5 μm filter element to obtain the polysilicon etching solution.

[0093] Table 2: Examples 1 to 7 of polysilicon etching solutions

[0094]

[0095] Table 3: Comparative Examples 1-3 of Preparation of Polysilicon Etching Solutions

[0096]

[0097] Table 4: Test data

[0098]

[0099] About performance testing and description:

[0100] Method for using polysilicon etching solution containing amphiphilic ionic liquid in 3D memory chip:

[0101] The polysilicon etching solution is introduced into an etching tank, and then the etching solution is used to soak the 3D memory chip at 25° C. for 6 minutes. The etched 3D memory chip is rinsed in ultrapure water at least twice, each time for no less than 30 seconds, and the etched 3D memory chip is obtained after the treatment.

[0102] Performance 1 The test method for surface tension is:

[0103] After the treatment is completed by the above method, the surface tension of the etching solution and the etching solution filtered 200 times by a 0.5 μm filter element are tested at room temperature using a surface tension tester. The test results are shown in Table 4.

[0104] Performance 2 Etching selectivity test method is:

[0105] The etching rates of the etching solution on the silicon oxide layer and the polysilicon layer are measured respectively, and the etching selectivity ratio can be obtained by dividing the etching rate of the silicon oxide layer by the etching rate of the polysilicon layer.

[0106] In the present invention, the ultrapure water used is deionized water with a resistance of at least 18 MΩ.

[0107] Analysis of the test results:

[0108] Based on Table 4, it can be seen that the difference between Comparative Example 1 and Example 1 is only that the amphiphilic ionic liquid is different, wherein Comparative Example 1 uses conventional N-ethyl perfluorooctane sulfonamide ethanol as a surfactant, resulting in an increase in surface tension and a decrease in etching selectivity. Comparative Example 2 does not add 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid imine lithium, and the etching rate cannot be adjusted. Comparative Example 3 uses 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid imine lithium alone as a surfactant, resulting in an increase in surface tension and a decrease in etching selectivity, while the ionic liquid synthesized by the present invention has a polyfluoro group, a cyclic structure, and a polyhydroxyl group, which can significantly reduce the surface tension and improve the etching selectivity.

[0109] Further comparison is made through the attached drawings in the specification:

[0110] The amphiphilic ionic liquid of Preparation Example 1 was subjected to infrared testing. The test results are shown in Figure 1 .

[0111] from Figure 1 It can be seen that the stretching vibration peak at 3433 cm-1 is -OH, the stretching vibration absorption peak at 3030 cm-1 is methyl, the asymmetric stretching vibration and symmetric stretching vibration of methylene are at 2980 cm-1 and 2845 cm-1, the in-plane bending vibration absorption peak of methylene CH is at 1431 cm-1, the peak at 1378 cm-1 belongs to the stretching vibration absorption peak of amine CN single bond, and the peaks at 1095 cm-1 and 1058 cm-1 are asymmetric and symmetric stretching vibrations of S=O. In summary, the ionic liquid surfactant has been successfully synthesized.

[0112] The present invention is described exemplarily above in conjunction with the embodiments and drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned methods. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A polysilicon etching solution, characterized in that: It comprises an amphiphilic ionic liquid, wherein the amphiphilic ionic liquid is a compound of the following formula I: Wherein, R1, R2, R3, and R4 are independently selected from hydroxyl, C1-C6 branched or straight chain alkyl with hydroxyl, and n1, n2, n3, and n4 can be the same or different and are any integers from 2 to 8.

2. The polysilicon etching solution according to claim 1, characterized in that: The preparation method of the amphiphilic ionic liquid comprises the following steps: The alcohol amine compound is dissolved in a solvent, stirred and preheated to 40-90° C., and then the halogen-containing alcohol substance is slowly added dropwise to react, and after the reaction is completed, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium is added. After the reaction is completed, the temperature is lowered and allowed to stand, and rotary evaporation is performed to obtain a compound of formula I. After the compound of formula I is purified and dried, an amphiphilic ionic liquid is obtained; The alcoholamine compound has a structure shown in the following formula II, and the halogen-containing alcohol substance has a structure shown in the following formula III, wherein X is a halogen; 。 3. The polysilicon etching solution according to claim 2, characterized in that: The molar ratio of the alcoholamine compound to the halogen-containing alcohol substance is 1:1-2.

4. The polysilicon etching solution according to claim 2, characterized in that: The solvent is at least one of an ester compound, an alcohol compound, a halogenated alkane, and a halogenated aromatic hydrocarbon.

5. The polysilicon etching solution according to claim 1, characterized in that: The components also include hydrofluoric acid, oxidizing acid and ultrapure water. The mass ratio of the amphiphilic ionic liquid, hydrofluoric acid, oxidizing acid and ultrapure water is 0.1-5:1-20:5-30:70-95.

6. The polysilicon etching solution according to claim 5, characterized in that: The oxidizing acid is any one or more of nitric acid, perchloric acid, hypochlorous acid and sulfuric acid.

7. A method for preparing the polysilicon etching solution according to any one of claims 1 to 6, characterized in that The following steps are involved: Weigh the respective amounts of the components respectively, then add ultrapure water, hydrofluoric acid, oxidizing acid, and amphiphilic ionic liquid into the container in sequence, fully stir and dissolve, and finally filter to obtain the polysilicon etching solution.

8. A method for treating 3D flash memory chips using the polysilicon etching solution according to any one of claims 1 to 6, characterized in that: The steps include: The polysilicon etching solution is introduced into the etching tank, and then the polysilicon etching solution is heated, and the 3D flash memory chip is immersed at 20-40° C. for 1-10 minutes. The immersed 3D flash memory chip is placed in ultrapure water and rinsed at least twice, each time for not less than 30 seconds, and the polysilicon etching solution is used to process the 3D flash memory chip.

9. Use of the polysilicon etching solution according to any one of claims 1 to 6 in the field of 3D flash memory chips.

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