Acid generator based on polystyrene sulfonium salt and photoresist composition thereof

Abstract

The invention discloses a styrene sulfonium salt polymer comprising a repeating unit shown in the following formula (I), the synthesis process of which is simple, and the raw materials are cheap and readily available. The polymer has good solubility in various polar solvents and excellent film-forming properties. The polymer is used as an acid generator in a photoresist to avoid the problems of poor solubility and poor film-forming properties of small molecule acid generators, and the polymer acid generator has better compatibility with the main material of the photoresist. By changing the sulfonium salt structure, the polymer has a long absorption wavelength, and can also be used for ultraviolet lithography and deep ultraviolet lithography.

Description

Technical Field

[0001] The invention belongs to the field of material technology, and in particular relates to a polymer acid generator based on polystyrene sulfonium salt and a photoresist composition thereof. Background Art

[0002] With the rapid development of the semiconductor industry, the integration of semiconductor devices is getting higher and higher, and the resolution required to be achieved by photolithography technology is also getting higher and higher. The quality of high-resolution photolithography patterns also puts forward higher requirements, especially the line width roughness (LWR) and line edge roughness (LER) of the patterns are becoming more and more stringent. Photoresist is a key material for transferring photolithography patterns during the processing of semiconductor devices. The photoresist is coated on different substrates, and after being irradiated with energy such as light beams, electron beams, ion beams or x-rays, the solubility changes, and then the corresponding pattern is transferred to the substrate through development and etching processes. The resolution that can be achieved by the pattern formed by the photoresist has a decisive influence on the integration of the device. The comprehensive performance of the photoresist needs to match the development of current photolithography technology.

[0003] At present, conventional high-resolution photoresists all use chemical amplification glue. The concept of "chemical amplification" was proposed by IBM in 1982, in which the photoacid generator (PAG) is a key component of the photoresist. The so-called "chemical amplification" means that PAG decomposes to produce acid after light exposure, and the acid triggers a series of chemical reactions, causing the solubility of the photoresist material in the illuminated area and the non-illuminated area to change significantly. Then, the pattern transfer can be achieved through development. Therefore, the acid generation efficiency of the photoacid generator and the uniformity of the distribution of the acid generator in the material play an important role in the pattern quality.

[0004] Common acid generators are mainly divided into ionic acid generators, such as sulfonium salts, iodonium salts and non-ionic acid generators. These acid generators are usually small molecules, which usually have poor solubility and poor compatibility with polymer host materials, resulting in uneven distribution of the acid generator in the host material, causing the resolution of the photoresist to decrease and the line edge roughness to increase. In comparison, the polymer acid generator has a similar structure to the photoresist host material and has better compatibility, thereby ensuring that the acid generator is more evenly distributed in the photoresist. This can improve the resolution of the photoresist and reduce the line edge roughness of the photoresist. Summary of the invention

[0005] In order to improve the above technical problems, the present invention first provides a sulfonium salt polymer of styrene, wherein the repeating unit of the polymer has a structure as shown in the following formula (I):

[0006]

[0007] Wherein: x and y represent the percentage of the two monomers in the polymer, x+y=1, 0<x≤0.3; x is, for example, 0.17, 0.25; y is, for example, 0.75, 0.83;

[0008] R 1 is selected from sulfonium salt groups; R 1 The position of R can be para, meta or ortho; 2 Selected from H, OH, halogen (Cl, F, I), C 1-15 Alkyl, C 1-15 Alkoxy, aryl; q is an integer selected from 1-5, preferably an integer of 1-3;

[0009] X – is an anion, for example, selected from halide, alkylsulfonate, halogenated alkylsulfonate (such as trifluoromethanesulfonate, perfluoropropylsulfonate, perfluorobutylsulfonate), p-toluenesulfonate, tetrafluoroborate, hexafluorophosphate, bistrifluoromethanesulfonyl imide ion.

[0010] According to an embodiment of the present invention, the R 1 For -S + R 3 R 4 , where R 3 , R 4 The same or different, independently selected from C 1-15 Alkyl, deuterated C 1-15 Alkyl (such as deuterated methyl), aryl, or R 3 , R 4 Together with the S connected thereto, it forms a 5-8 membered sulfur-containing heterocyclic group, wherein the sulfur-containing heterocyclic group may optionally further contain 1-2 oxygen or sulfur, and the sulfur-containing heterocyclic group may optionally be fused with one or two benzene rings; the alkyl, aryl, sulfur-containing heterocyclic group may be substituted by one, two or more (e.g., 1-5) R 1 'Replace. 1 ' may be the same or different and are independently selected from H, oxo, nitro, CN, C 1-15 Alkyl, C 1-15 Alkoxy;

[0011] According to an embodiment of the present invention, the R 1 is selected from unsubstituted or optionally substituted with one, two or more R 1 'Substituted with the following groups:

[0012]

[0013] in, Represents the bond between the substituent and the benzene ring in the main structure; R 1a and R 1b may be the same or different, and are independently selected from C1-15 Alkyl, deuterated C 1-15 Alkyl or one, two or more R d Substituted phenyl; each R d are the same or different and are independently selected from H, nitro, C 1-15 Alkyl, C 1-15 Alkoxy; m can be selected from an integer of 0-5; Y is selected from C, O, S, C(O);

[0014] According to an embodiment of the present invention, R 1 can be selected from unsubstituted or optionally substituted with one, two or more R 1 'Substituted with the following groups:

[0015]

[0016] R 1a and R 1b may be the same or different and are independently selected from methyl, ethyl, propyl, isopropyl, butyl, deuterated methyl, R d can be selected from H, nitro, ethoxy, ethyl, propyl, butyl, isopropyl, isobutyl; m can be 1 or 2; R 1 ' may be the same or different and are independently selected from H, nitro, ethoxy, ethyl, ethyl, propyl, butyl, isopropyl, isobutyl.

[0017] As an example, the repeating unit of the polymer has the following structure:

[0018]

[0019] wherein x and y have the definitions given above.

[0020] According to an embodiment of the present invention, the number average molecular weight of the copolymer of formula (I) is 500-200000 Daltons, such as 1000-100000 Daltons, and for example 5000-50000 Daltons.

[0021] The present invention also provides a method for preparing the above-mentioned polymer, comprising the following steps: preparing a polymer having a repeating unit represented by formula (II):

[0022]

[0023] x, y, q, R 2 As defined above,

[0024] reacting with a sulfoxide compound to obtain a polymer having a repeating unit represented by formula (I);

[0025] Optionally, the polymer having a repeating unit represented by formula (I) is ion exchanged with a corresponding anion solution to obtain polystyrene sulfonium salts with different anions.

[0026] The sulfoxide compound may be R 3 -SO-R 4 , for example, selected from:

[0027]

[0028] Among them, R 1a , R 1b , R 3 , R 4 , Y, m, x, y have the definitions given above;

[0029] According to an embodiment of the present invention, the reaction may be carried out under the action of a catalyst, and the catalyst may be trifluoromethanesulfonic anhydride or trifluoromethanesulfonic acid;

[0030] According to an embodiment of the present invention, the molar ratio of polystyrene or its copolymer to the sulfoxide compound in the reaction may be 1:(0.05-0.5), for example, 1:(0.1-0.3).

[0031] According to the present invention, polystyrene is mixed with R 3 -SO-R 4 Reaction to obtain a polymer whose repeating unit is represented by formula (I);

[0032] According to the present invention, the polymer having the structure represented by formula (II) is prepared by the following method, comprising polymerizing styrene and a compound represented by formula (III) in a certain ratio to obtain a polymer having a repeating unit represented by formula (II),

[0033]

[0034] x, y, q, R 2 As defined above.

[0035] The present invention also provides the use of the polymer as an acid generator in a photoresist.

[0036] The present invention also provides a photoresist composition, which comprises a polymer whose repeating unit is a polymer represented by formula (I), a polymer having an acid-sensitive functional group, and a photoresist solvent.

[0037] According to an embodiment of the present invention, in the photoresist composition, when the x value in the polymer is preferably greater than 0.1 and less than 0.3, the solubility of the main material changes significantly before and after exposure, and the performance of the photoresist is better.

[0038] According to an embodiment of the present invention, the polymer of the acid-sensitive functional group may be, for example, a copolymer of p-hydroxystyrene and p-hydroxystyrene protected by a Boc group, a copolymer of adamantyl methacrylate and methacrylate butyrolactone; for example, the following structure:

[0039] s and t represent the percentage of the two monomers in the polymer, s+t=1, s is, for example, 0.4, and t is, for example, 0.6.

[0040] According to an embodiment of the present invention, the content of the polymer represented by formula (I) in the photoresist composition as a repeating unit is 0.1%-5% of the total mass of the photoresist, and the rest is the polymer having acid-sensitive functional groups and the photoresist solvent.

[0041] According to an embodiment of the present invention, the photoresist solvent is selected from one or more of the following substances: propylene glycol methyl ether acetate, cyclohexanone, ethyl n-amyl ketone, ethyl isoamyl ketone, ethanol, acetonitrile, isopropanol, and acetone.

[0042] A photoresist coating comprises the photoresist composition.

[0043] The present invention also provides a method for preparing the photoresist coating, comprising: forming a film on a substrate by spin coating the photoresist composition to obtain the chemically amplified photoresist coating.

[0044] In one embodiment, the substrate may be a silicon wafer or the like.

[0045] The invention also provides application of the photoresist coating in photolithography.

[0046] In one embodiment, the photoresist coating is used in modern lithography technologies such as 365nm lithography, 248nm lithography, 193nm lithography, extreme ultraviolet lithography, nanoimprint lithography or electron beam lithography; and is particularly suitable for high-resolution lithography technologies such as 193nm, electron beam lithography and extreme ultraviolet (EUV).

[0047] Beneficial Effects

[0048] The invention provides a styrene sulfonium salt polymer shown in formula (I), the synthesis process of which is simple, and the raw materials are cheap and easily available; the synthesized styrene sulfonium salt polymer is used as an acid generator in a photoresist, thereby avoiding the problems of poor solubility and uneven distribution of the acid generator in a chemically amplified photoresist, and the obtained pattern has a very high resolution and low line width roughness. The styrene sulfonium salt polymer has a long absorption wavelength by changing the sulfonium salt structure, so that it can be used not only for deep ultraviolet lithography, but also for ultraviolet lithography (365nm). BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a scanning electron microscope image of compound (1) in Example 2 of the present invention.

[0050] Figure 2 This is the thermogravimetric curve of compound (1) in Example 2 of the present invention.

[0051] Figure 3 This is the UV exposure pattern of the photoresist formulation containing compound (1) in Example 6 of the present invention.

[0052] Figure 4 This is a comparison diagram of the electron beam exposure patterns of the photoresist formulation containing compound (1) (left) and the photoresist formulation containing a small molecule acid generator (right) in Example 7 of the present invention.

[0053] Definition and explanation of terms

[0054] Unless otherwise defined, all technical and scientific terms herein have the same meaning as commonly understood by one of ordinary skill in the art to which the claimed subject matter belongs.

[0055] "More" means three or more.

[0056] The term "halogen" includes F, Cl, Br or I.

[0057] The term "C 1-15 "Alkyl" is understood to mean a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 15 carbon atoms. For example, "C 1-6 The term "alkyl" refers to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5, or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, 1,2-dimethylbutyl, or the like or isomers thereof.

[0058] The term "C 1-15 "Alkoxy" is understood to mean -OC 1-15 Alkyl, where C 1-15 Alkyl has the above definition.

[0059] The term "aryl" is understood to mean an aromatic monocyclic, bicyclic or tricyclic hydrocarbon ring having 6 to 20 carbon atoms, preferably "C 6-14 Aryl". For example, phenyl, naphthyl, fluorenyl, anthracenyl, etc. DETAILED DESCRIPTION

[0060] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0061] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0062] Example 1.

[0063] Preparation of polystyrene, the synthetic route is as follows:

[0064]

[0065] Specific steps: Add styrene (100 ml), AIBN (2 g), and then THF (200 ml) into a 500 ml three-necked flask. Bubble for 30 min. React at 70 ° C for 24 h, and drop the reaction solution into methanol for precipitation. The obtained product is vacuum dried. The weight average molecular weight is about 2000 Daltons using GPC test. Styrene with different molecular weights can also be prepared by other polymerization methods or purchased directly.

[0066] Example 2.

[0067] The synthetic route for preparing polymer (1) is as follows:

[0068]

[0069] Specific steps: Add the polystyrene prepared in Example 1 to a 500 ml Schlenk bottle, then add solvent DCM (200 ml) and DMSO (0.3 eq). Add trifluoromethanesulfonic anhydride (0.6 eq) dropwise at -40°C under inert gas conditions. Stir overnight at room temperature, dissolve the product with dichloromethane, and then dropwise add n-hexane to precipitate to obtain the final product, with x being 0.25 and y being 0.75, and then dry in vacuum. 1 H NMR (400MHz, DMSO) δ (ppm) 7.67 (s, 2H), 6.81 (s, 2H), 3.16 (s, 1.5H), 0.9-1.8 (s, 3H).

[0070] Example 3.

[0071] The synthesis route of polymer (2) is as follows:

[0072]

[0073] Specific steps: Add the polystyrene prepared in Example 1 to a 500 ml Schlenk bottle, then add solvent DCM (200 ml) and diphenyl sulfoxide (0.3 eq). Add trifluoromethanesulfonic anhydride (0.6 eq) dropwise at -40°C under inert gas conditions. Stir at room temperature overnight, dissolve the product with dichloromethane, and then dropwise add n-hexane to precipitate to obtain the final product, with x being 0.17 and y being 0.83, and then dry in vacuum. 1 H NMR (400MHz, DMSO) δ (ppm) 6.7-7.8 (m, 6.5H), 0.9-1.8 (s, 3H).

[0074] Example 4

[0075] The polymer (1) in Example 2 was dissolved in acetonitrile to obtain a 30 mg / ml solution, which was filtered through a microporous filter with a pore size of 0.22 μm to obtain a spin coating solution, which was spin coated on a silicon substrate to form a film. The uniformity of the film was analyzed using a scanning electron microscope (SEM). Figure 1 , it can be seen from the figure that the obtained film is very uniform.

[0076] Example 5

[0077] The thermal stability of the polymer (1) prepared in Example 2 was measured. The results showed that the decomposition temperature of the polymer (1) reached above 200°C, and the polymer (1) had good thermal stability. Figure 2 .

[0078] Example 6

[0079] A photoresist formulation and ultraviolet lithography: The polymer (1) of Example 2 and the acid-sensitive polymer GBLMA-MAMA (the repeating unit is shown in the figure below, and the weight-average molecular weight is about 12,000 Daltons) are dissolved in PGMEA to obtain a solution with a mass concentration of 5%, which is filtered through a microporous filter with a pore size of 0.22 μm to obtain a spin coating solution, which is spin-coated on a silicon substrate and baked at 100° C. for 3 minutes. The prepared film is subjected to an exposure experiment (254 nm), and developed using TMAH alkaline solution to obtain very clear stripes with a line width of 1 μm. Figure 3 The resulting stripe line edge roughness is very small.

[0080]

[0081] Example 7

[0082] A photoresist formulation and electron beam lithography: The polymer (1) of Example 2 and the acid-sensitive polymer GBLMA-MAMA (weight-average molecular weight of about 12,000 Daltons) are dissolved in PGMEA, filtered with a microporous filter with a pore size of 0.22 μm to obtain a spin coating solution, which is spin-coated on a silicon substrate and baked at 100° C. for 3 minutes. The prepared film is exposed to an electron beam to obtain a very clear 50 nm stripe pattern with very small line edge roughness. Figure 4 (Left). When commercial triphenylsulfonium salt is used as an acid generator, the resulting 50nm stripe pattern has large line edge roughness. Figure 4 (right).

[0083] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A styrene sulfonium salt polymer, wherein the repeating unit of the polymer has a structure as shown in the following formula (I): Where: x and y represent the percentage of the two monomers in the polymer, x+y=1, 0<x≤0.3; R1 is -S + R3R4, wherein R3 and R4 are the same or different and are independently selected from C 1-15 Alkyl, deuterated C 1-15 Alkyl, aryl; the alkyl, aryl is optionally substituted by one, two or more R1'; each R1' is the same or different and is independently selected from H, C 1-15 Alkyl, C 1-15 Alkoxy; the position of R1 is para, meta or ortho; R2 is selected from H, C 1-15 Alkyl, C 1-15 Alkoxy; q is an integer selected from 1 to 5; X – Selected from halide ion, alkyl sulfonate, haloalkyl sulfonate, p-toluene sulfonate, tetrafluoroborate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide ion.

2. The polymer according to claim 1, characterized in that q is an integer selected from 1-3.

3. The polymer according to claim 1, characterized in that The halogenated alkyl sulfonate is selected from trifluoromethanesulfonate, perfluoropropylsulfonate and perfluorobutylsulfonate.

4. The polymer according to claim 1, characterized in that The R1 is selected from the following groups which are unsubstituted or optionally substituted by one, two or more R1': in, Represents the bond connecting the substituent and the benzene ring in the main structure; R 1a and R 1b The same or different, each independently selected from C 1-15 Alkyl, deuterated C 1-15 Alkyl; R1' has the definition as defined in claim 1.

5. The polymer according to claim 1, characterized in that The repeating units of the polymer are selected from the following structures: wherein x and y have the definitions as described in claim 1.

6. The method for preparing the polymer according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: preparing a polymer having a repeating unit represented by formula (II): x, y, q, R2 are as defined in any one of claims 1 to 5; reacting with a sulfoxide compound to obtain a polymer having a repeating unit represented by formula (I); The sulfoxide compound is R3-SO-R4; Wherein, R3 and R4 have the definitions as described in any one of claims 1 to 5; The reaction is carried out under the action of a catalyst, and the catalyst is trifluoromethanesulfonic anhydride or trifluoromethanesulfonic acid; In the reaction, the molar ratio of polystyrene or its copolymer to the sulfoxide compound is 1:(0.05-0.3).

7. The preparation method according to claim 6, characterized in that: The sulfoxide compound is selected from: Among them, R 1a , R 1b The same or different, each independently selected from C 1-15 Alkyl, deuterated C 1-15 alkyl.

8. Use of the polymer according to any one of claims 1 to 5 as an acid generator in a photoresist.

9. A photoresist composition, characterized in that: The invention comprises the polymer according to any one of claims 1 to 5, a polymer having an acid-sensitive functional group and a photoresist solvent.

10. The photoresist composition according to claim 9, characterized in that The value of x in the polymer is greater than 0.1 and less than 0.

3.

11. The photoresist composition according to claim 9, characterized in that The polymer with acid-sensitive functional groups is selected from p-hydroxystyrene and Boc group-protected p-hydroxystyrene copolymers, adamantyl methacrylate and butyrolactone methacrylate copolymers.

12. The photoresist composition according to claim 9, characterized in that The content of the polymer with the repeating unit represented by formula (I) in the photoresist composition is 0.1%-5% of the total mass of the photoresist, and the rest is the polymer with acid-sensitive functional groups and the photoresist solvent.

13. The photoresist composition according to claim 9, characterized in that The photoresist solvent is selected from one or more of the following substances: propylene glycol methyl ether acetate, cyclohexanone, ethyl n-amyl ketone, ethyl isoamyl ketone, ethanol, acetonitrile, isopropanol, and acetone.

14. A photoresist coating, comprising the photoresist composition according to any one of claims 9 to 13.

15. Use of the photoresist composition according to any one of claims 9 to 13 and / or the photoresist coating according to claim 14 in photolithography.

16. The use according to claim 15, characterized in that The application is application in 365nm lithography, 248nm lithography, 193nm lithography, extreme ultraviolet lithography, nanoimprint lithography or electron beam lithography.

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