Mercaptosulfonic acid ionic liquid, method of preparation, use and copper etching liquid comprising same

Abstract

The application provides a thiol sulfonic acid ionic liquid of formula I or II, a preparation method and application thereof, and further provides a copper etching solution containing the ionic liquid, the etching solution is prepared by containing the ionic liquid, an organic base, an organic acid, a complexing agent, hydrogen peroxide and ultrapure water, the etching solution can effectively remove a copper seed layer on a wafer, can significantly reduce copper side etching, and can be applied to the technical field of semiconductor wafer processing.

Description

Technical Field

[0001] This invention relates to an acidic ionic liquid, its preparation method, and its use, and more particularly to a mercaptosulfonic acid ionic liquid, its preparation method, and its use, as well as a copper etching solution containing the same for use in the field of semiconductor wafer processing technology, belonging to the fields of novel etching solutions and semiconductor wafer processing technology. Background Technology

[0002] In the post-Moore era, as consumer electronics demand increasingly more in terms of portability, miniaturization, and high performance, traditional packaging can no longer meet market needs and technological requirements. Therefore, the application of advanced packaging technology has become the mainstream trend for improving the overall performance of chips.

[0003] Currently, advanced packaging mainly refers to achieving electrical connections through bumps, including various advanced packaging processes such as flip-chip, wafer-level packaging, system-in-package, and 2.5D / 3D packaging.

[0004] In wafer-level packaging, copper is often chosen as the seed layer. After the wiring is completed through multiple processes, the copper seed layer needs to be removed to expose the completed structure or circuit. This removal of the copper seed layer is mainly accomplished by etching copper.

[0005] Among them, the hydrogen peroxide system for copper etching solutions has several advantages over other copper etching solution systems (such as the ferric chloride system and the ammonium persulfate system), such as: it does not introduce metal ion impurities, has high etching efficiency, and a long service life. The etching process of the hydrogen peroxide system copper etching solution involves several stages: 1. Oxidation: Hydrogen peroxide reacts with copper in a redox reaction to produce copper oxide and water; 2. Dissolution: Copper oxide reacts with hydrogen ions in the etching solution to change from an oxidized state to an ionic state; 3. Complexation (chelation): The ionic copper then reacts with a complexing (chelating) agent in the etching solution to form a stable copper complex (chelate). Hydrogen peroxide itself is a strong oxidizing agent with weak acidity. Its oxidation reaction rate is slower in acidic solutions and faster in alkaline solutions. Therefore, most commercially available hydrogen peroxide system copper etching solutions are acidic, mainly provided by strong acidic sulfuric acid.

[0006] However, with the refinement of packaging technology and the stacking of multi-level packaging, the strong corrosiveness of acids, especially sulfuric acid, has caused other metals to be corroded, making the hydrogen peroxide system unable to meet current market demands.

[0007] In view of this, the requirements for copper etching solutions are becoming increasingly stringent, especially in terms of the metal protection performance of the etching solution and the control of copper side etching.

[0008] Ionic liquids are salts composed entirely of anions and cations that are liquid at or near room temperature; they are sometimes also called low-temperature molten salts. As ionic compounds, the low melting point of ionic liquids is mainly due to the asymmetry of certain substituents in their structure, which prevents the ions from regularly stacking into crystals. Ionic liquids have almost no vapor pressure and possess many excellent characteristics and properties, including non-flammability, non-volatility, good chemical and thermal stability, recyclability, and environmental friendliness. Furthermore, their molecular structure is designable and can be controlled and altered by selecting different anions and cations and / or the types of side-chain substituents.

[0009] However, to date, there have been no reports of using ionic liquids in copper etching solutions in the semiconductor processing field, let alone reports that ionic liquid copper etching solutions can significantly reduce lateral etching.

[0010] Therefore, it is particularly important and urgent to overcome the shortcomings of hydrogen peroxide etching solutions, especially to significantly improve copper side etching, which is also the current research and development direction in the field of etching solutions.

[0011] Based on this, the present invention aims to provide a novel mercaptosulfonic acid ionic liquid, its preparation method and uses, and also provides a novel copper etching solution containing the ionic liquid. By using the novel mercaptosulfonic acid ionic liquid, the copper etching solution has excellent metal protection properties. While effectively removing the copper seed layer on the wafer, it also significantly reduces copper side etching. It can provide effective technical support for the formation and fabrication of narrow-pitch bumps and fine lines in wafer-level packaging, and has great application prospects and promotion value in the field of wafer packaging technology. Summary of the Invention

[0012] In order to solve the numerous problems existing in the above-mentioned existing copper peroxide etching solutions and various existing copper etching solutions, to meet the requirements and trends of current semiconductor packaging technology development such as effectively removing copper seed layers, especially significantly reducing copper side etching, and in order to develop novel ionic liquids and their preparation methods and uses, the inventors of this invention have conducted extensive and in-depth research and exploration, thereby providing a novel mercaptosulfonic acid ionic liquid, its preparation method, its uses, and a copper etching solution containing the ionic liquid, thus completing this invention.

[0013] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," "consisting of," etc., and similar meanings.

[0014] Specifically, the present invention includes the following technical solutions.

[0015] [First technical solution]

[0016] In a first aspect, one technical solution of the present invention is to provide a mercaptosulfonic acid ionic liquid compound (hereinafter sometimes simply referred to as "mercaptosulfonic acid ionic liquid" or "ionic liquid").

[0017] In this invention, the mercaptosulfonic acid ionic liquid is a compound of formula I or formula II:

[0018]

[0019] Wherein, R is selected from C1-C6 branched or straight-chain alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl or C6-C10 aryl;

[0020] n is an integer between 2 and 8.

[0021] In the structural formula, "+" represents a positive charge on N, while "-" represents a corresponding negative charge paired with the positive charge (in the case of HSO4). - (Formal manifestation).

[0022] The C1-C6 branched or straight-chain alkyl group refers to a straight-chain or branched alkyl group having 1-6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, and n-hexyl.

[0023] The C2-C6 alkenyl group refers to an alkenyl group having 2-6 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 1-pentenyl, and 1-hexenyl.

[0024] The C3-C6 cycloalkyl group refers to a cycloalkyl group having 3-6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0025] The C6-C10 aryl group refers to an aryl group having 6-10 carbon atoms, such as phenyl or naphthyl.

[0026] Wherein, the HSO4 - To be compatible with the N cation (N) in formula I-II + () paired anions.

[0027] Where n represents the number of repeating units of methylene-CH2-, which is an integer from 2 to 8, for example, it can be 2, 3, 4, 5, 6, 7 or 8.

[0028] The inventors have discovered that the ionic liquids of Formula I-II can be used in copper etching solutions in wafer packaging technology. By including the ionic liquid, the copper etching solution has excellent copper seed layer removal capability, and in particular, excellent copper side etching reduction performance.

[0029] [Second Technical Solution]

[0030] Secondly, one technical solution of the present invention is to provide a method for preparing the thiosulfonic acid ionic liquid of formula I or II, wherein the preparation reaction formula of the thiosulfonic acid ionic liquid of formula I is as follows:

[0031]

[0032] The preparation reaction formula for the formula II mercaptosulfonic acid ionic liquid is as follows:

[0033]

[0034] Furthermore, the preparation method includes the following steps:

[0035] S1. Preparation of precursors;

[0036] S2. Purification and drying of the precursor;

[0037] S3, Preparation of ionic liquids;

[0038] S4. Purification and drying of ionic liquids.

[0039] In the preparation method of the mercaptosulfonic acid ionic liquid of the present invention, step S1 is specifically as follows:

[0040] Add the following compound III or IV to a solvent, stir and preheat to 40-70°C, then add the following sulfonyl lactone compound V dropwise, stir to react, then cool and let stand, and then evaporate by rotary evaporation to obtain the precursor of the following compound VI or VII.

[0041] The definitions of R and n in compounds of formula III or IV are as described above and will not be repeated here.

[0042] In step S1, the solvent is an ester compound, an alcohol compound, a haloalkane, a haloaromatic hydrocarbon, etc., such as any one of ethyl acetate, methyl acetate, methanol, ethanol, n-propanol, isopropanol, n-butanol, chloroform, tetrachloromethane, chlorobenzene, dichlorobenzene, etc.

[0043] The amount of solvent used is not particularly strictly limited, and those skilled in the art can make appropriate selections and determinations according to actual needs (e.g., appropriate determinations based on the convenience of the reaction), which will not be described in detail here.

[0044] In step S1, the mixture is first stirred and preheated to 40-70°C, for example, to 40°C, 50°C, 60°C or 70°C.

[0045] In step S1, the molar ratio of the compound of formula III or IV to the sulfonyl lactone compound of formula V is 1:2-4, for example, it can be 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0046] In step S1, there is no strict limit to the reaction time, as long as the reaction is complete. For example, the reaction endpoint can be determined by chromatographic detection. These are conventional techniques in the field and will not be described in detail here.

[0047] However, the reaction time is typically 10-40 hours, for example, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours or 40 hours.

[0048] In the preparation method of the mercaptosulfonic acid ionic liquid of the present invention, step S2 is specifically as follows:

[0049] The precursor obtained in step S1 above is washed thoroughly in ethyl acetate, acetonitrile, and tetrahydrofuran 1-5 times in sequence (i.e., washed thoroughly in ethyl acetate 1-5 times, washed thoroughly in acetonitrile 1-5 times, and washed thoroughly in tetrahydrofuran 1-5 times), then rotary evaporated and dried under vacuum to obtain the precursor.

[0050] In step S2, the washing time for each wash is not strictly limited, as long as it is sufficient to wash the clothes. For example, it can be 1 minute, 3 minutes, 5 minutes, 7 minutes, 9 minutes or 10 minutes. Those skilled in the art can determine the appropriate time according to the actual situation, which will not be described in detail here.

[0051] In step S2, the temperature of the vacuum drying is 60-90℃, for example, it can be 60℃, 70℃, 80℃ or 90℃. Those skilled in the art can determine the appropriate temperature according to the actual situation, which will not be described in detail here.

[0052] In step S2, the vacuum drying time is not strictly limited, as long as it can dry 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 or 10 hours. Those skilled in the art can determine the appropriate time according to the actual situation, which will not be described in detail here.

[0053] In the preparation method of the mercaptosulfonic acid ionic liquid of the present invention, step S3 is specifically as follows:

[0054] The precursor obtained in step S2 above was added to deionized water, sulfuric acid aqueous solution was added dropwise at room temperature and the reaction was stirred. The reaction temperature was controlled at 40-80℃. After the reaction was completed, the ionic liquid was obtained by vacuum rotary evaporation.

[0055] In step S3, the amount of deionized water used is not particularly strictly limited. Those skilled in the art can make appropriate selections and determinations according to actual needs, which will not be described in detail here.

[0056] In step S3, the mass percentage concentration of the sulfuric acid aqueous solution is not strictly limited, as long as the amount is sufficient to allow the reaction to proceed fully. For example, it can be 30-98%, such as 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 98%.

[0057] In step S3, the molar ratio of the precursor to sulfuric acid (i.e., sulfuric acid contained in an aqueous sulfuric acid solution) can be 1:2.5-4, for example, 1:2.5, 1:3, 1:3.5 or 1:4.

[0058] In step S3, there is no strict limit to the reaction time, as long as the reaction is complete. For example, the reaction endpoint can be determined by chromatographic detection. These are conventional techniques in the field and will not be described in detail here.

[0059] Typically, it can be 4-10 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0060] In the preparation method of the mercaptosulfonic acid ionic liquid of the present invention, step S4 is specifically as follows:

[0061] The ionic liquid obtained in step S3 above is thoroughly washed with ethyl acetate 2-6 times and then dried under vacuum to obtain the mercaptosulfonic acid ionic liquid.

[0062] In step S4, the washing time for each wash is not strictly limited, as long as it is sufficient to wash the clothes. For example, it can be 1 minute, 3 minutes, 5 minutes, 7 minutes, 9 minutes or 10 minutes. Those skilled in the art can determine the appropriate time according to the actual situation, which will not be described in detail here.

[0063] In step S4, the temperature of the vacuum drying is 60-90℃, for example, it can be 60℃, 70℃, 80℃ or 90℃. Those skilled in the art can determine the appropriate temperature according to the actual situation, which will not be described in detail here.

[0064] In step S4, the vacuum drying time 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 or 10 hours. Those skilled in the art can determine the appropriate time according to the actual situation, which will not be described in detail here.

[0065] [Third technical solution]

[0066] Thirdly, one aspect of the present invention relates to the use of the mercaptosulfonic acid ionic liquid in wafer-level packaging.

[0067] The inventors have discovered that the mercaptosulfonic acid ionic liquid can be used in wafer-level packaging, thereby exhibiting excellent copper seed layer removal capability and excellent copper side etching reduction capability, which is surprising and unexpected.

[0068] [Fourth technical solution]

[0069] Fourthly, one technical solution of the present invention is to provide a copper etching solution for wafer-level packaging.

[0070] The copper etching solution comprises ionic liquid, organic base, organic acid, complexing agent, hydrogen peroxide, and ultrapure water.

[0071] Furthermore, the copper etching solution comprises, by weight, the following components:

[0072]

[0073] In the copper etching solution of the present invention, the ionic liquid is the aforementioned mercaptosulfonic acid ionic liquid.

[0074] The ionic liquid has a mass fraction of 0.1-3 parts, for example, 0.1 parts, 0.2 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts or 3 parts.

[0075] In the copper etching solution of the present invention, the organic base is 1-5 parts by mass, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts.

[0076] The organic base is selected from any one or a mixture of any combination of dimethylamine, triethanolamine, pyridine, triethylamine, diethanolamine, isopropylamine, isobutanolamine, 1,8-diazabicycloundec-7-ene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, tetramethylguanidine, tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, or tetramethylammonium hydroxide.

[0077] In the copper etching solution of the present invention, the organic acid is in the form of 1-5 parts by mass, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts.

[0078] The organic acid is selected from any one or a mixture of any of the following: humic acid, pyruvic acid, salicylic acid, formic acid, acetic acid, citric acid, oxalic acid, tartaric acid, oxalic acid, malonic acid (i.e., 1,3-malonic acid), succinic acid (i.e., 1,4-succinic acid), octanoic acid (i.e., 1,8-octanoic acid), glutaric acid (i.e., 1,5-glutaric acid), or adipic acid (i.e., 1,6-adipic acid).

[0079] In the copper etching solution of the present invention, the complexing agent is 1-5 parts by mass, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts.

[0080] The complexing agent is selected from any one or a mixture of any of the following: disodium ethylenediaminetetraacetate, glycine, alanine, trisodium citrate, sodium tartrate, sodium carboxymethyl cellulose, or sodium hexametaphosphate.

[0081] In the copper etching solution of the present invention, the hydrogen peroxide is 1-10 parts by mass, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts.

[0082] In the copper etching solution of the present invention, the mass fraction of ultrapure water is 70-95 parts, for example, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or 95 parts.

[0083] The ultrapure water is deionized water with a resistance ≥18MΩ.

[0084] The copper etching solution of the present invention can be used to remove the copper seed layer in the wafer-level packaging process and has excellent copper side etching performance. This provides effective technical support for the formation and fabrication of narrow-pitch bumps and fine lines in wafer-level packaging, and has great application prospects and promotion value in the field of wafer packaging technology.

[0085] [Fifth technical solution]

[0086] Fifthly, one technical solution of the present invention is to provide a method for preparing the above-mentioned copper etching solution.

[0087] The preparation method is as follows: weigh out the respective amounts of each component, then add ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base and complexing agent into a container in sequence, stir and dissolve thoroughly, and finally filter to obtain the copper etching solution.

[0088] The filtration process can employ a 0.1-0.5μm filter element.

[0089] As described above, the present invention provides a mercaptosulfonic acid ionic liquid, a preparation method thereof, its uses, and a copper etching solution containing the ionic liquid and a preparation method thereof.

[0090] The copper etching solution of the present invention achieves many excellent technical effects by using the mercaptosulfonic acid ionic liquid, such as: eliminating the need for strong acid sulfuric acid, thus prolonging the decomposition of hydrogen peroxide compared to sulfuric acid, and producing less hazardous waste liquid that is easy to treat; significantly reducing corrosion of wafer metal; exhibiting excellent copper seed layer removal performance; and significantly reducing copper side etching caused by etching.

[0091] Therefore, the copper etching solution of the present invention has excellent wafer-level packaging etching performance, avoids many shortcomings of existing etching solutions, can significantly improve packaging yield, thereby reducing production costs, and does not require the use of strong acids such as sulfuric acid, thus making it more user-friendly for operators and the operating environment. It has good application prospects and use value in the field of wafer-level packaging etching. Attached Figure Description

[0092] Appendix Figure 1 The images show the infrared spectra of the mercaptosulfonic acid ionic liquids L1-L2 obtained in Preparation Examples 1-2.

[0093] Appendix Figure 2 This is a scanning electron microscope (SEM) section image of a wafer after etching with copper etching solution Y1 from Example 1.

[0094] Appendix Figure 3 This is a scanning electron microscope (SEM) section image of a wafer after etching with copper etching solution Y2 as described in Example 2.

[0095] Appendix Figure 4 Scanning electron microscope (SEM) section of a wafer etched with copper etchant D1 as described in Comparative Example 1.

[0096] Appendix Figure 5 Scanning electron microscope (SEM) section of a wafer etched with copper etchant D7 as described in Comparative Example 7. Detailed Implementation

[0097] The present invention will now be described in detail through specific embodiments. However, the uses and purposes of these exemplary embodiments are merely illustrative and are not intended to limit the actual scope of protection of the present invention in any way, nor are they intended to restrict the scope of protection of the present invention to these embodiments.

[0098] Preparation Example 1: Preparation of Formula I mercaptosulfonic acid ionic liquid

[0099] The reaction equation is as follows:

[0100]

[0101] Where R is methyl and n = 3 (i.e., the raw material compound V is 1,3-propanesulfonyl lactone).

[0102] Specifically, the steps include the following:

[0103] S1. Preparation of precursors

[0104] The compound of Formula III (i.e., 3-mercapto-5-methyl-1,2,4-triazole) was added to an appropriate amount of ethyl acetate solvent, stirred and preheated to 45°C, and then 1,3-propanesulfonyl lactone of Formula V was added dropwise. The mixture was stirred and reacted for 15 hours, then cooled and allowed to stand, and then evaporated by rotary evaporation to obtain the precursor of the compound of Formula VI.

[0105] The molar ratio of compound III to compound V, 1,3-propanesulfonyl lactone, is 1:3.

[0106] S2. Purification and drying of precursors

[0107] The precursor obtained in step S1 was washed twice in ethyl acetate, acetonitrile, and tetrahydrofuran, respectively, for 10 minutes each time. Then, it was rotary evaporated and dried under vacuum at 90°C for 3 hours to obtain the purified precursor.

[0108] S3, Preparation of Ionic Liquids

[0109] The precursor obtained in step S2 above was added to an appropriate amount of deionized water, and a sulfuric acid aqueous solution with a mass percentage concentration of 50% was added dropwise at room temperature and the mixture was stirred and reacted for 10 hours. The reaction temperature was controlled at 50°C. After the reaction was completed, the ionic liquid, namely compound I, was obtained by vacuum rotary evaporation.

[0110] The molar ratio of the precursor to sulfuric acid (i.e., sulfuric acid contained in an aqueous sulfuric acid solution) is 1:3.

[0111] S4. Purification and Drying of Ionic Liquids

[0112] The ionic liquid obtained in step S3 above was washed thoroughly with ethyl acetate three times, for 10 minutes each time, filtered, and then dried under vacuum at 85°C for 10 hours to obtain the mercaptosulfonic acid ionic liquid of formula I in the above reaction equation, which was named L1.

[0113] Preparation Example 2: Preparation of Formula II thiosulfonic acid ionic liquid

[0114] The reaction equation is as follows:

[0115]

[0116] Where R is methyl and n = 3 (i.e., the raw material compound V is 1,3-propanesulfonyl lactone).

[0117] Specifically, the steps include the following:

[0118] S1. Preparation of precursors

[0119] The compound IV (i.e., 5-mercapto-1-methyltetrazolium) was added to an appropriate amount of solvent n-propanol, stirred and preheated to 65°C, and then 1,3-propanesulfonyl lactone of the above formula V was added dropwise. The mixture was stirred and reacted for 25 hours, then cooled and allowed to stand. The mixture was then evaporated by rotary evaporation to obtain the precursor of the compound VI.

[0120] The molar ratio of compound IV to compound V, 1,3-propanesulfonyl lactone, is 1:4.

[0121] S2. Purification and drying of precursors

[0122] The precursor obtained in step S1 was washed three times in ethyl acetate, acetonitrile, and tetrahydrofuran, respectively, for 5 minutes each time. Then, it was rotary evaporated and dried under vacuum at 65°C for 8 hours to obtain the purified precursor.

[0123] S3, Preparation of Ionic Liquids

[0124] The precursor obtained in step S2 above was added to an appropriate amount of deionized water, and an 80% sulfuric acid aqueous solution was added dropwise at room temperature and the mixture was stirred for 5 hours. The reaction temperature was controlled at 70°C. After the reaction was completed, the ionic liquid, namely compound II, was obtained by vacuum rotary evaporation.

[0125] The molar ratio of the precursor to sulfuric acid (i.e., sulfuric acid contained in an aqueous sulfuric acid solution) is 1:4.

[0126] S4. Purification and Drying of Ionic Liquids

[0127] The ionic liquid obtained in step S3 above was washed thoroughly with ethyl acetate five times, for five minutes each time, and then dried under vacuum at 85°C for four hours to obtain the mercaptosulfonic acid ionic liquid of formula II in the above reaction equation, which was named L2.

[0128] Among them, the appendix Figure 1 The infrared spectra of the above-mentioned mercaptosulfonic acid ionic liquids L1-L2 are shown (from top to bottom, they are the infrared spectra of L1 and L2, respectively). The value at 3091 cm⁻¹ is... -1 2870cm -1 The peaks at 2967 cm⁻¹ represent the stretching vibration absorption peaks of the methyl and methylene groups in the ionic liquid, respectively. -1 The peak of the stretching vibration of -SH is at 1183 cm⁻¹. -1 1066cm -1 The peak at 1660 cm⁻¹ represents the asymmetric and symmetric stretching vibrations of S=O on -SO₃H. -1 1558cm -1 These are absorption peaks for the stretching and bending vibrations of the -C=N bonds on heterocyclic rings. And specifically, the peak at 1723 cm⁻¹. -11470cm -1 The peaks are the stretching vibration peaks of NN in L1-L2 and N=N in L2, respectively.

[0129] In the following examples of copper etching solutions, the ultrapure water used was deionized water with a resistance ≥18MΩ, and will not be described in detail.

[0130] Example 1

[0131] Weigh out 0.1 parts by weight of ionic liquid L1, 5 parts of organic base triethanolamine, 1 part of organic acid pyruvic acid, 5 parts of complexing agent disodium ethylenediaminetetraacetate, 1 part of hydrogen peroxide, and 95 parts of ultrapure water. Then, add the weighed ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base, and complexing agent into a container in sequence, stir thoroughly to dissolve, and finally filter with a 0.3 μm filter to obtain copper etching solution, which is named Y1.

[0132] Example 2

[0133] Weigh out 3 parts by weight of ionic liquid L1, 1 part of organic base pyridine, 5 parts of organic acid acetic acid, 1 part of complexing agent sodium tartrate, 10 parts of hydrogen peroxide, and 70 parts of ultrapure water. Then, add the weighed ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base, and complexing agent into a container in sequence, stir thoroughly to dissolve, and finally filter with a 0.2 μm filter to obtain copper etching solution, which is named Y2.

[0134] Example 3

[0135] By mass, 1.5 parts of ionic liquid L1, 3 parts of organic base 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 3 parts of organic acid adipic acid, 3 parts of complexing agent sodium hexametaphosphate, 5.5 parts of hydrogen peroxide, and 82.5 parts of ultrapure water were weighed out. Then, the weighed ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base, and complexing agent were added to the container in sequence, stirred thoroughly to dissolve, and finally filtered through a 0.2 μm filter to obtain the copper etching solution, which was named Y3.

[0136] Example 4

[0137] By mass, weigh 0.1 parts of ionic liquid L2, 5 parts of organic base 1,8-diazabicycloundec-7-ene, 1 part of organic acid salicylic acid, 5 parts of complexing agent glycine, 1 part of hydrogen peroxide, and 95 parts of ultrapure water. Then, add the weighed ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base, and complexing agent to a container in sequence, stir thoroughly to dissolve, and finally filter with a 0.2 μm filter to obtain copper etching solution, which is named Y4.

[0138] Example 5

[0139] Weigh out 3 parts by weight of ionic liquid L2, 1 part of organic base tetramethylguanidine, 5 parts of organic acid oxalic acid, 1 part of complexing agent sodium carboxymethyl cellulose, 10 parts of hydrogen peroxide, and 70 parts of ultrapure water. Then, add the weighed ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base, and complexing agent into a container in sequence, stir thoroughly to dissolve, and finally filter with a 0.2 μm filter to obtain copper etching solution, which is named Y5.

[0140] Example 6

[0141] Weigh out 1.5 parts by weight of ionic liquid L2, 3 parts by weight of organic base tetraethylammonium hydroxide, 3 parts by weight of organic acid citric acid, 3 parts by weight of complexing agent trisodium citrate, 5.5 parts by weight of hydrogen peroxide, and 82.5 parts by weight of ultrapure water. Then add the weighed ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base and complexing agent into a container in sequence, stir thoroughly to dissolve, and finally filter through a 0.2 μm filter to obtain copper etching solution, which is named Y6.

[0142] Comparative Examples 1-6

[0143] Except for deleting the ionic liquids described in Examples 1-6, everything else remained unchanged, thus obtaining copper etching solutions, which were named D1, D2, D3, D4, D5 and D6 in sequence.

[0144] Comparative Examples 7-12

[0145] Except for replacing the ionic liquid described in Examples 1-6 with the same mass of sulfuric acid, everything else remained unchanged, thus obtaining copper etching solutions, which were named D7, D8, D9, D10, D11 and D12 in sequence.

[0146] Tests on the removal of copper seed layers and copper side etching performance of various copper etching solutions

[0147] Two 2×2cm copper-nickel-gold wafers were respectively selected (where, from top to bottom, the layers are gold, nickel, and copper, and the copper seed layer has a thickness of [missing information]). The wafers were immersed in 100 ml of the etching solutions of Examples 1-6 and Comparative Examples 1-12, respectively. The temperature of the etching solution was maintained at 23±0.5℃. The etching endpoint was reached when the color of the copper-nickel-gold wafers changed. The wafers were then removed, rinsed thoroughly with pure water, and finally purged and dried with high-purity nitrogen.

[0148] From the appendix Figure 2-5 As can be seen, the copper seed layer on all copper-nickel-gold wafers was completely removed.

[0149] The maximum copper lateral erosion CD-loss was measured by scanning electron microscopy cross-section. max (Maximum critical size loss) case.

[0150] in:

[0151] As attached Figure 2 As shown, copper etching was performed using copper etching solution Y1 from Example 1, and then the sections were processed by scanning electron microscopy. The maximum copper lateral etching CD-loss was found. max It is 289nm.

[0152] As attached Figure 3 As shown, copper etching was performed using the Y2 etching solution from Example 2, and then the sections were processed by scanning electron microscopy. The maximum copper lateral etching CD-loss was found. max It is 308nm.

[0153] And attached Figure 4 As shown, copper etching was performed using copper etching solution D1 (Comparative Example 1), and then the cross-sections were processed by scanning electron microscopy. The maximum copper lateral etching loss (CD-loss) was found. max It is 863nm.

[0154] And attached Figure 5 As shown, copper etching was performed using copper etchant D7 (Comparative Example 7), and the resulting sections were then processed by scanning electron microscopy. The maximum copper lateral etching loss (CD-loss) was observed. max It is 803nm.

[0155] Scanning electron microscope (SEM) images of other copper etching solutions Y3-Y6, D2-D6, and D8-D12 are not listed individually; instead, their maximum copper lateral etching CD-loss is presented. max Data including the maximum copper lateral etching CD-loss of Y1-Y2, D1, and D7 max The data is listed in Table 1 below.

[0156] Table 1: Maximum copper lateral etching CD-loss for each copper etching solution max

[0157]

[0158]

[0159] In Table 1 above, the " / " indicates the corresponding relationship. For example, taking Y1-Y6 as an example, "CD-loss" max In “(nm)”, “289 / 308 / 282 / 297 / 311 / 293” represents the CD-loss of Y1-Y6. max The nm values ​​are 289nm, 308nm, 282nm, 297nm, 311nm and 293nm respectively, and D1-D6 and D7-D12 have the same correspondence, which will not be described in detail here.

[0160] As can be seen from Table 1 above: 1. The copper etching solution of the present invention has excellent copper seed layer removal performance, and more unexpectedly, it can significantly improve the copper side etching performance, which is neither obvious nor expected. 2. When the mercaptosulfonic acid ionic liquid is omitted (i.e., D1-D6), it is found that the copper side etching performance is significantly worse, much worse than Y1-Y6. 3. In contrast, when the mercaptosulfonic acid ionic liquid is replaced with sulfuric acid (i.e., D7-D12), it is found that the copper side etching performance is also much worse than Y1-Y6, but better than D1-D6. This proves that the effect of reducing copper side etching ability mainly depends on the presence of the mercaptosulfonic acid ionic liquid.

[0161] As described above, the present invention provides a mercaptosulfonic acid ionic liquid, a preparation method, and uses, as well as a copper etching solution comprising the mercaptosulfonic acid ionic liquid for use in the field of semiconductor wafer processing technology. The copper etching solution achieves numerous superior technical effects by using the mercaptosulfonic acid ionic liquid, such as eliminating the need for strongly acidic sulfuric acid, thus prolonging the decomposition of hydrogen peroxide compared to sulfuric acid, and producing less hazardous waste liquid that is easy to treat; it can also significantly reduce copper side etching caused by etching.

[0162] Therefore, the copper etching solution of the present invention has excellent wafer-level packaging etching performance, avoids many shortcomings of existing etching solutions, can significantly improve packaging yield, thereby reducing production costs, and does not require the use of strong acids such as sulfuric acid, thus making it more user-friendly for operators and the operating environment. It has good application prospects and use value in the field of wafer-level packaging etching.

[0163] It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention. Furthermore, it should be understood that after reading the technical description of this invention, those skilled in the art can make various alterations, modifications, and / or variations to the invention, and all such equivalent forms also fall within the scope of protection defined by the appended claims.

Claims

1. A mercaptosulfonic acid ionic liquid of formula I or II below, wherein R is selected from C1-C6 branched or straight-chain alkyl groups; n is an integer between 2 and 8.

2. The method for preparing the mercaptosulfonic acid ionic liquid according to claim 1, characterized in that: The preparation reaction formula for the mercaptosulfonic acid ionic liquid of formula I is as follows: The preparation reaction formula for the formula II mercaptosulfonic acid ionic liquid is as follows: The definitions of R and n are the same as in claim 1.

3. Use of the mercaptosulfonic acid ionic liquid of claim 1 in wafer-level packaging.

4. A copper etching solution for wafer-level packaging, the copper etching solution comprising the ionic liquid of claim 1, an organic base, an organic acid, a complexing agent, hydrogen peroxide, and ultrapure water.

5. The copper etching solution according to claim 4, characterized in that: The organic base is selected from any one or a mixture of any combination of dimethylamine, triethanolamine, pyridine, triethylamine, diethanolamine, isopropylamine, isobutanolamine, 1,8-diazabicycloundec-7-ene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, tetramethylguanidine, tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, or tetramethylammonium hydroxide.

6. The copper etching solution according to claim 4 or 5, characterized in that: The organic acid is selected from any one or a mixture of any of the following: humic acid, pyruvic acid, salicylic acid, formic acid, acetic acid, citric acid, oxalic acid, tartaric acid, oxalic acid, 1,3-malonic acid, 1,4-succinic acid, 1,8-octanoic acid, 1,5-glutaric acid, or 1,6-adipic acid.

7. The copper etching solution according to claim 4, characterized in that: The complexing agent is selected from any one or a mixture of any of the following: disodium ethylenediaminetetraacetate, glycine, alanine, trisodium citrate, sodium tartrate, sodium carboxymethyl cellulose, or sodium hexametaphosphate.

8. The copper etching solution according to claim 4, characterized in that: The ultrapure water is deionized water with a resistance ≥ 18 MΩ.

9. The method for preparing the copper etching solution according to claim 4, wherein the preparation method specifically comprises: weighing each component in its respective amounts, then adding ultrapure water, hydrogen peroxide, ionic liquid, organic acid, organic base and complexing agent sequentially into a container, stirring thoroughly to dissolve, and finally filtering to obtain the copper etching solution.

10. The preparation method according to claim 9, characterized in that: The filtration uses a 0.2 μm filter element.

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