Polyacrylate leveling agent, preparation method thereof and application of polyacrylate leveling agent in chemically amplified photoresist

Abstract

The invention discloses an acrylate copolymer. The acrylate copolymer is shown as a structural formula (I), and in the formula (I), the sum of x, y and z is 1; the R1 group is a hydroxyl substituted linear long alkane chain; r2 groups are acid-sensitive groups such as tert-butyl groups; and the R3 group is a five-membered, six-membered or other cyclic structure, and has the characteristics that the C / H ratio is greater than 0.8 and / or oxygen atoms are doped and the like. The invention also discloses a preparation method of the acrylate copolymer, and the acrylate copolymer can be prepared by free radical polymerization and needs to be purified by precipitation, extraction, washing and other steps. The flatting agent is suitable for the technical fields of KrF line photoetching and the like, can be used as the flatting agent, is added according to the content of 0.05-1% of photoresist, can eliminate fisheye, increase fluidity and avoid the phenomenon of uneven film thickness after spin coating and baking of the photoresist, and has an obvious improvement effect on T-top morphology and Top-loss conditions. The method has a wide application prospect. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of photoresists, and particularly to a polyacrylate leveling agent, a preparation method thereof, and an application thereof in a chemically amplified photoresist. Background Art

[0002] The large-scale production of integrated circuits has profoundly changed human society, and its manufacturing process is inseparable from the lithography step and the key raw material - photoresist. A photoresist is a corrosion-resistant thin film material whose solubility changes after being irradiated or radiated by different light sources. Through processes such as silicon wafer surface treatment, spin coating, baking, exposure with a mask, development, etching, etc., the pattern on the mask can be skillfully and accurately transferred to the silicon wafer through the different solubility properties of the exposed area / non-exposed area of the photoresist. Subsequently, processes such as etching are carried out, and after several such processes, a complex circuit structure can be constructed. According to the different exposure light sources, photoresists can be classified into categories such as G-line, I-line, KrF-line, ArF-line, ArFi-line, etc., and the corresponding minimum resolution that can be achieved increases in sequence. Among them, for processes above the KrF-line, chemically amplified photoresists are often used to improve the photon utilization rate. As the resolution increases, the precision requirements of the process also become higher, and the uniformity of spin coating is an important indicator of the photoresist. However, some photoresists have problems such as inappropriate viscosity, poor coatability, uneven film thickness, rough surface, and many defects.

[0003] Leveling agents are an effective means to solve the above problems. In existing solutions, leveling agents of polyether-modified silicone, fluorinated aliphatic polymers, and other chemical components are often used. For example, CN105566552B uses sorbitan monopalmitate as a leveling agent for a chemically amplified photoresist; according to the examples disclosed in CN112650025B, silicone-based agents are used as leveling agents for chemically amplified photoresists; in patents such as CN115877659A / CN116009353A / CN116125748A, etc., fluorocarbon surfactants of 3M and polysiloxane-based leveling agents of Troy are also used as additives for chemically amplified photoresists. Due to the low proportion of the leveling agent in the photoresist, fewer patents specifically report on leveling agents for photoresists. Currently, there are even fewer reports on the application of polyacrylate leveling agents in photoresists.

[0004] The working principle of polyacrylate leveling agents is generally as follows: The leveling agent migrates to the interface between the photoresist solution and air, producing a reverse flow control effect and increasing the spreadability of the polymer chains in the photoresist. The compatibility between the leveling agent and the main components of the photoresist needs to be controlled just right: If the compatibility is too good, the leveling agent will not migrate to the surface but be evenly mixed, resulting in no leveling effect at this time; if it is too incompatible, the alkyl chains will shield the resin solution, interrupting the leveling and causing uneven accumulation of the leveling agent on the surface. Considering the subsequent processes of lithography, on the one hand, if the leveling agent is easily washed off by the developer, the leveling effect after development will be greatly reduced, and it will be difficult to eliminate the surface roughness during the post-baking process of the photoresist in the non-exposed area; conversely, if the polarity is low, it may hinder the dissolution of the resin in the exposed area, resulting in poor morphologies such as T-top. Therefore, it is necessary to develop a leveling agent that meets the requirements of lithography at each stage; considering the limitations of electronic chemicals on impurities such as metal ions, the leveling agent should also meet the requirement of low metal impurities. Summary of the Invention

[0005] The present invention provides an acrylate copolymer, which is represented by the following structural formula (I). In the formula (I), the sum of x, y, and z is 1; the R1 group is a linear long alkane chain (C1 - C9) substituted with a hydroxyl group; the R2 group includes acid-sensitive groups such as tert-butyl; the R3 group includes cyclic structures such as five-membered and six-membered rings, which have a C / H ratio greater than 0.8 and / or the characteristic of doping oxygen atoms.

[0006]

[0007] Specifically, the acrylate copolymer is a ternary acrylate copolymer resin, which contains three unit components. Preferably, the proportion range of each unit is: R1: 55 - 80%; R2: 5 - 20%; R3: 15 - 25%. Among them, the R1 group is a linear long alkane chain (C1 - C9) substituted with a hydroxyl group, accounting for 55 - 80%, which has the function of assisting leveling; the R2 group is an acid-sensitive group such as tert-butyl, accounting for 5 - 20%, which has the function of regulating solubility; the R3 group is a cyclic structure such as five-membered and six-membered rings, which has a relatively high C / H ratio and / or the characteristic of oxygen atom substitution, accounting for 15 - 25%.

[0008] Preferably, the molecular weight range of the acrylate copolymer is 10000 - 20000, and the polymer dispersity index PDI is 1.3 - 1.8. Preferably, the proportion range of each unit is: R1: 55 - 80%; R2: 5 - 20%; R3: 15 - 25%

[0009] Preferably, in the structural formula (I),

[0010] R1 includes but is not limited to the following structures:

[0011]

[0012] Preferably, R1 is a linear alkyl group substituted with a hydroxyl group having 2 to 4 carbon atoms such as -CH2CH2OH, -CHOHCH2OH, -CH2CHOHCH3, -CH2CHOHCH2OH, etc.

[0013] R2 includes but is not limited to the following structures:

[0014]

[0015] Preferably, R2 is a group having 3 to 5 carbon atoms such as tert-butyl, trimethylsilyl, tert-amyl, etc.; and / or an alkyl group containing a tertiary carbon.

[0016] R3 includes but is not limited to the following structures:

[0017]

[0018] Preferably, R3 is benzyl, 2-methylene furan, 3-methylene furan.

[0019] In the present invention, the "acrylate copolymer" refers to a high molecular linear polymer obtained by copolymerizing three or more acrylate monomers as shown in the structural formula (I).

[0020] Specifically, the present invention also provides polymer ①, polymer ②, and polymer ③, and their structural formulas are as follows:

[0021] The chemical structure of polymer ① is shown as follows:

[0022]

[0023] The chemical structure of polymer ② is shown as follows:

[0024]

[0025] The chemical structure of polymer ③ is shown as follows:

[0026]

[0027] The present invention also provides a preparation method of the acrylate copolymer. The method is to first synthesize a resin by free radical polymerization and then purify it by extraction or other means.

[0028] Specifically, the preparation method of the present invention includes: first synthesizing a resin by free radical polymerization and then purifying it by extraction; in the preparation method, by adjusting the mutual solubility of the aqueous layer and the organic layer, an organic layer concentrated with the copolymer can be obtained, and small molecule impurities and metal impurities can be effectively removed.

[0029] In a specific embodiment, the preparation method includes the following steps:

[0030] Step 1: First, under the conditions of an initiator and heating, acrylic monomers undergo a polymerization reaction to synthesize an acrylate copolymer resin as shown in structural formula (I);

[0031] Step 2: Then, the unreacted monomers, initiators, and other impurities in the first step are removed by extraction with water and / or alcohols. Meanwhile, the metal impurities in the system are reduced. The selected alcohols need to have the characteristic of being miscible with water and the solvent used in the polymerization. In some specific embodiments, for example, when the polymerization solvent is an ester, such as ethyl acetate or butyl acetate, a mixed solvent of water and methanol is preferably added. At this time, the mass ratio of water to methanol is preferably 1:19 - 1:4. When the polymerization solvent is toluene, methanol is preferably added. When the polymerization solvent is methanol, water is preferred. Other suitable solvent types can also be replaced according to the actual preparation scenario and requirements.

[0032] Step 3: The low-boiling solvents and water are removed through solvent replacement with the solvents used in the photoresist system to obtain the acrylate copolymer as shown in structural formula (I). The steps are as follows: vacuum distillation, and then adding ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol methyl ethyl ether, neopentyl acetate, methyl isobutyl ketone, cyclopentanone, cyclohexanone, diacetone alcohol, or γ-butyrolactone, etc., which are the solvents used in the photoresist system. Preferably, the solvent used in the photoresist system is propylene glycol monomethyl ether acetate.

[0033] In the preparation method, by adjusting the miscibility of the water layer and the organic layer, an organic layer concentrated with the copolymer can be obtained, and small molecule impurities and metal impurities can be effectively removed.

[0034] In the preparation method of the present invention, the initiator is any one or any combination of two or more of benzoyl peroxide, azodiisobutyric acid, dimethyl azodiisobutyrate, azodiisobutyronitrile, etc. Preferably, it is azodiisobutyronitrile; and / or, the low-boiling solvents include organic substances immiscible with water such as esters, ketones, ethers, alcohols, etc.; and / or, the boiling point of the low-boiling solvents is 80 - 180°C.

[0035] In the present invention, the preparation method of the acrylate copolymer is as follows: using azo and peroxy radical initiators, heating and copolymerizing in an organic solvent, and then removing unreacted monomers and other impurities by extraction, and controlling the metal impurities at an extremely low level.

[0036] The present invention provides the acrylate copolymer obtained by the above preparation method, as shown in structural formula (I).

[0037] The present invention also provides a polyacrylate leveling agent, which contains the acrylate copolymer as shown in the structural formula (I). The acrylate copolymer provided by the present invention in the structural formula (I) can be used as a polyacrylate leveling agent.

[0038] The present invention also provides a chemically amplified photoresist, which contains the acrylate copolymer as shown in the structural formula (I). It also includes, but is not limited to, a base resin, a solvent, a photoacid generator, a quencher, a surfactant, and / or an additive, etc. The base resin includes one or more of the following resins:

[0039] The structure of Resin 1 (BOC-PHS resin) is as follows, x / y = 15:85 - 40:60, Mw = 6k - 30k:

[0040]

[0041] The structure of Resin 2 (EVE-PHS resin) is as follows, a / b = 15:85 - 40:60, Mw = 6k - 30k:

[0042]

[0043] The structure of Resin 3 (ESCAP resin) is as follows, c / d = 15:85 - 40:60, Mw = 10k - 30k:

[0044]

[0045] The structure of Resin 4 (Terpolymer resin) is as follows, m = 10 - 40%; n = 55 - 85%; o = 0 - 35%, Mw = 10k - 30k:

[0046]

[0047] The solvent includes one or more of the following: methyl ethyl ketone, methyl amyl ketone, ethyl 3 - ethoxypropionate, ethyl tert - valerate, propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether propionate, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, N - methylpyrrolidone, γ - butyrolactone, propylene glycol methyl ether acetate (PGMEA), ethyl lactate, propyl lactate, etc.

[0048] The photoacid generator includes α-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide (MDT), N-hydroxy-naphthalimide (DDSN), benzoin tosylate, tert-butylphenyl-α-(p-toluenesulfonyloxy)-acetate and tert-butyl-α-(p-toluenesulfonyloxy)-acetate, triarylsulfonium and diaryliodonium trifluoromethanesulfonates, iodonium perfluorooctanesulfonates, N-camphorsulfonyloxynaphthalimide, ionic iodonium sulfonates (such as diaryliodonium (alkyl)sulfonates or diaryliodonium (aryl)sulfonates and bis-(di-tert-butylphenyl)iodonium camphenylsulfonate), perfluorinated alkanesulfonates (such as perfluoropentanesulfonate, perfluorooctanesulfonate, perfluoromethanesulfonate), aryl (e.g., phenyl or benzyl) trifluoromethanesulfonates (such as triphenylsulfonium trifluoromethanesulfonate or bis-(tert-butylphenyl)iodonium trifluoromethanesulfonate), tert-butylphenyl iodonium salt perfluorooctanesulfonic acid, etc.

[0049] The quencher includes but is not limited to amine compounds or mixtures of amine compounds, such as triethanolamine, trioctylamine, tetrabutylammonium hydroxide, triisopropanolamine, triethylenediamine, etc.

[0050] The surfactant includes Polyfox PF-656, FC-4430, Troysol S366, etc.

[0051] The additive can be a dissolution inhibitor to help control the dissolution of the photoresist during development. Specific examples include tert-butyl deoxycholate, tert-butyl lithocholate, and tert-butyl-3-acetyl lithocholate.

[0052] Preferably, the base resin is composed of Terpolymer resin and EVE-PHS resin, and their mass ratio is 1:1. The solvent is PGMEA, the photoacid generator is tert-butylphenyl iodonium salt perfluorooctanesulfonic acid, the quencher is triethanolamine, and the surfactant and the additive are not added. The acrylate copolymer of structural formula (I) provided by the present invention can be used to prepare a chemically amplified photoresist.

[0053] The present invention also discloses the application of the acrylate copolymer in chemically amplified photoresists, including assisting in leveling, achieving a uniform coating effect, etc. When used as a leveling agent in a photoresist, due to the introduction of acid-sensitive groups, a solubility difference will also be generated in the exposed area / non-exposed area, which is beneficial to improving the top morphology of the photoresist after development. The resin of the present invention also contains a cyclic structure with a relatively high carbon-hydrogen ratio, etc. According to relevant theories (the smaller the Ohnishi parameter and the larger the Ring parameter, the stronger the etching resistance. The Ohnishi parameter is defined as N / (Nc - No), where N is the total number of atoms including hydrogen atoms in the polymer repeating unit, Nc is the number of carbon atoms, and No is the number of oxygen atoms; the Ring parameter is defined as Mcr / Mtot, where Mcr and Mtot are the mass of the polymer present in the form of carbon atoms contained in the ring structure and the total mass of the polymer, respectively), the etching resistance of the photoresist surface can be improved.

[0054] The present invention also provides the application of the acrylate copolymer for preparing chemically amplified photoresists and the application as a polyacrylate leveling agent. The present invention also provides the application of the chemically amplified photoresist in I-line, KrF-line, ArF-line, ArFi-line, etc.

[0055] The present invention also provides the usage methods of the acrylate copolymer and the chemically amplified photoresist. In a specific embodiment, the usage method includes the following steps: spin-coating a photoresist on a silicon wafer, pre-baking, exposing, post-baking, and developing to finally obtain a photolithography pattern; preferably, the pre-baking temperature is 70 - 150 °C; the pre-baking time is 30 - 180 s; the post-baking temperature is 90 - 200 °C; the post-baking time is 30 - 180 s; the developer used for development is an aqueous solution of tetramethylammonium hydroxide; the development time is 30 - 130 s. Further preferably, the pre-baking temperature is 100 - 130 °C, the pre-baking time is 90 - 100 s, the post-baking temperature is 110 - 140 °C, the post-baking time is 90 - 100 s, and the development time is 60 s.

[0056] The beneficial effects of the present invention include: the acrylate copolymer of the present invention can be prepared by free radical polymerization and needs to be purified through steps such as precipitation, extraction, and water washing. The present invention is applicable to technical fields such as KrF-line lithography. It can be used as a leveling agent and is added in an amount of 0.05 - 1% of the photoresist, which can eliminate fish eyes, increase fluidity, avoid the phenomenon of uneven film thickness after spin-coating and baking of the photoresist, and has an obvious improvement effect on the T-top morphology and Top-loss situation, and has broad application prospects. Description of the Drawings

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, without creative work, other drawings can be obtained based on these drawings.

[0058] Figure 1 It represents the cross-sectional morphology of Sample I in the embodiments of the present invention.

[0059] Figure 2 It represents the cross-sectional morphology of Sample II in the embodiments of the present invention.

[0060] Figure 3 It represents the cross-sectional morphology of Sample III in the embodiments of the present invention.

[0061] Figure 4 It represents the cross-sectional morphology of Sample IV in the embodiments of the present invention.

[0062] Figure 5 It represents the cross-sectional morphology of Sample V in the embodiments of the present invention.

[0063] Figure 6 It represents the cross-sectional morphology of Sample VI in the embodiments of the present invention. Detailed implementation manners

[0064] Combined with the following specific embodiments and drawings, the present invention will be further described in detail. The protection scope of the present invention is not limited to the following embodiments. Without departing from the spirit and scope of the inventive concept, the changes and advantages that those skilled in the art can think of are included in the present invention, and the scope of protection is defined by the appended claims. The processes, conditions, reagents, experimental methods, etc. for implementing the present invention, except for the specifically mentioned content below, are all common knowledge and well-known common sense in the art, and the present invention has no special limiting content.

[0065] In the experiments of the present invention, reagents such as 2-hydroxyethyl acrylate, tert-butyl acrylate, furfuryl methacrylate, butyl acetate, and azobisisobutyronitrile are all chemically pure.

[0066] 1. Preparation and purification of the polyacrylate compound:

[0067] Polymer ①:

[0068] In a 1000 mL three-necked round-bottom flask (high borosilicate glass), a magnetic stir bar (wrapped with PTFE) was placed, and a condenser and a dropping funnel were connected. The vacuum-purging with nitrogen operation was repeated three times, and 450 g of butyl acetate was bubbled in under a nitrogen atmosphere. The temperature was raised to 70 °C; 81.3 g of 2-hydroxyethyl acrylate (unit A), 29.9 g of tert-butyl acrylate (unit B), 38.8 g of furfuryl methacrylate (unit C), and 6.7 g of azobisisobutyronitrile were mixed evenly and bubbled with nitrogen for 2 min, then charged into the dropping funnel under a nitrogen atmosphere and slowly added dropwise over 30 min. Subsequently, the reaction was carried out at 70 °C for 7 h under uniform stirring of the magnetic stir bar. After the reaction solution was cooled, it was poured into a 1.5 L PFA separatory funnel, 50 g of methanol was added, and then extracted with 500 g of high-purity water. The above steps of adding methanol-high-purity water extraction were repeated 3 times, and the organic layer was sent for GPC measurement, and it was found that the monomer signal peak became weak. The obtained colorless and transparent organic layer was transferred to a 1000 mL three-necked round-bottom flask (high borosilicate glass), and vacuum distillation was carried out while stirring, and PGMEA was added as appropriate until the solvent was completely replaced with propylene glycol monomethyl ether acetate (PGMEA) (residual methyl acetate in GC test < 0.5%), and the solid content was adjusted to 30%. The test results by gel permeation chromatography (GPC) were Mw = 12524, PDI = 1.49; the unit ratio calculated by quantitative carbon spectrum integration was: A / B / C = 57:19:24; the test results of gold impurities by atomic absorption spectrometry (AAS) were: Na 3.6 ppb, K 1.6 ppb, Ca 2.4 ppb, Fe 0.8 ppb. The chemical structure of polymer ① is as follows:

[0069]

[0070] Polymer ②:

[0071] In a 1000 mL three-necked round-bottom flask (high borosilicate glass), a magnetic stir bar (wrapped with PTFE) was loaded, and a condenser and a dropping funnel were connected. The vacuum-purging with nitrogen operation was repeated three times, and 450 g of butyl acetate was bubbled in under a nitrogen atmosphere. The temperature was raised to 70 °C; 113.9 g of 2-hydroxyethyl acrylate (unit A), 15.7 g of tert-butyl acrylate (unit B), 20.4 g of furfuryl methacrylate (unit C), and 6.7 g of azobisisobutyronitrile were mixed evenly and bubbled with nitrogen for 2 min, then loaded into the dropping funnel under a nitrogen atmosphere and slowly added dropwise within 30 min. Subsequently, the reaction was carried out at a constant temperature of 70 °C for 7 hours with magnetic stirring. After the reaction solution was cooled, it was poured into a 1.5 L PFA separatory funnel, 50 g of methanol was added, and then extracted with 500 g of high-purity water. The above steps of adding methanol-high-purity water extraction were repeated 3 times, and the organic layer was sent for GPC measurement, and it was found that the monomer signal peak became weak. The obtained colorless and transparent organic layer was transferred to a 1000 mL three-necked round-bottom flask (high borosilicate glass), and vacuum distillation was carried out with stirring, and PGMEA was supplemented as appropriate until the solvent was completely replaced with PGMEA (residual methyl acetate in GC test < 0.5%), and the solid content was adjusted to 31%. The GPC test results were Mw = 11807, PDI = 1.49; the unit ratio calculated by quantitative carbon spectrum integration was: A / B / C = 78:10:12; the results of AAS test for metal impurities were: Na 0.9 ppb, K 0.7 ppb, Ca 2.7 ppb, Fe 1.1 ppb. The chemical structure of Polymer ② is as follows:

[0072]

[0073] Polymer ③:

[0074] In a 1000 mL three-necked round-bottom flask (made of high borosilicate glass), a magnetic stir bar (wrapped with PTFE) was placed, and a condenser and a dropping funnel were connected. The operations of evacuating and filling with nitrogen were repeated three times, and 450 g of butyl acetate was added by bubbling under a nitrogen atmosphere. The temperature was raised to 70 °C; 113.9 g of 2-hydroxyethyl acrylate (unit A), 15.7 g of tert-butyl acrylate (unit B), 20.4 g of furfuryl methacrylate (unit C), and 4.5 g of azobisisobutyronitrile were mixed evenly and bubbled with nitrogen for 2 min, then placed in the dropping funnel under a nitrogen atmosphere and slowly added dropwise within 30 min. Subsequently, the reaction was carried out at a constant temperature of 70 °C for 7 hours with uniform stirring by the magnetic stir bar. After the reaction solution was cooled, it was poured into a 1.5 L PFA separating funnel, 50 g of methanol was added, and then extracted with 500 g of high-purity water. The above steps of adding methanol-high-purity water extraction were repeated 3 times. The organic layer was sent for GPC measurement, and it was found that the monomer signal peaks became weak. The obtained colorless and transparent organic layer was transferred to a 1000 mL three-necked round-bottom flask (made of high borosilicate glass), and vacuum distillation was carried out with stirring, and PGMEA was added as appropriate until the solvent was completely replaced by PGMEA (residual methyl acetate in GC test < 0.5%), and the solid content was adjusted to 28%. The GPC test results were Mw = 16781, PDI = 1.48; the unit ratio calculated by quantitative carbon spectrum integration was: A / B / C = 79:10:11; the results of AAS test for metal impurities were: Na 2.9 ppb, K 0.2 ppb, Ca 4.4 ppb, Fe 2.0 ppb. The chemical structure of Polymer ③ is as follows:

[0075]

[0076] 2. Preparation of photoresist:

[0077] Photoresist Sample I: A positive photoresist composition comprising the following raw material components by weight: 150 g of poly(styrene-tert-butyl acrylate-p-hydroxystyrene) terpolymer resin (abbreviated as Terpolymer resin, unit ratio 10:25:65, solid content 33.3%, solvent ethyl lactate, Mw 12609), 150 g of poly(1-(1-ethoxyethoxy)-4-vinylbenzene-p-hydroxystyrene) resin (abbreviated as EVE-PHS resin, unit ratio 35:65, solid content 33.3%, solvent ethyl lactate, Mw 18099), 5.0 g of tert-butylphenyl iodonium perfluorooctanesulfonate (TBI-PFOS), 1.0 g of triethanolamine (TEOA), 192.9 g of ethyl lactate, 400 g of PGMEA.

[0078] The photoresist samples II-VI were obtained by adding the corresponding leveling agents to sample I according to the proportions shown in the following table. The parts of raw materials in the formula are based on the dry weight, and the amount of the solvent PGMEA in the formula is 4 times the mass of the solid resin (Terpolymer resin + EVE-PHS resin).

[0079] Table 1. Photoresist formulation information

[0080]

[0081] 3. Film thickness test results and final morphology

[0082] The photoresist samples I-VI were spin-coated on 8-inch silicon wafers using a spin coater. Then, after the silicon wafers coated with the photoresist composition were vacuum-dried, the film thickness was measured after baking at 100 °C for 90 s. Among them, the target film thickness was set to

[0083] The mask plate was detected using a standard L / S = 1:1, with a target CD of 140 nm. The obtained photoresist layers were exposed using a light source of KrF line (wavelength 248 nm). The pre-baking condition was 130 °C / 90 s, and the post-baking condition was 140 °C / 90 s. Then, a 2.38 w% aqueous solution of tetramethylammonium hydroxide was used as the developer to develop the exposed photoresist layers for 60 s, obtaining photoresist patterns.

[0084] After slicing, cross-sectional morphology was collected using a scanning electron microscope. The leveling degrees of different photoresists are shown in Table 2 below.

[0085] Table 2. Leveling degrees of photoresists

[0086]

[0087] Note: The calculation method for the range of film thickness measurement: the maximum film thickness minus the minimum film thickness

[0088] The sliced morphologies of the photoresist samples are as shown in Table 3 and Figures 1-6 as follows.

[0089] Table 3. Sliced morphologies and summaries of photoresists

[0090]

[0091] Note: The collection conditions for the sliced morphologies were exposure at the optimal energy (Eop) and Focus = 0.

[0092] In summary, the performance of the photoresist-coated steel using the acrylic leveling agent of the present invention is significantly improved compared to the reference samples (Samples II and III, using commercial leveling agents), manifested as a smaller film thickness range, that is, an increase in the film thickness uniformity after spin coating. Moreover, the morphology after development is also better than that of the reference samples, effectively avoiding both T-top and Top-loss defective morphologies. The acrylate copolymer proposed in the present invention can completely replace the currently used commercial siloxane-based and fluorocarbon-based leveling agents in assisting photoresist leveling.

[0093] The protection scope of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be conceived by those skilled in the art are included in the present invention, and the appended claims are used as the protection scope.

Claims

1. An acrylate copolymer, characterized in that, The acrylate copolymer is shown as the following structural formula (I): Wherein, in the formula (I), the sum of x, y, and z is 1; the R1 group is a linear long alkane chain C1-C9 substituted with a hydroxyl group; the R2 group is an acid-sensitive group including a tert-butyl group; the R3 group is a cyclic structure including a five-membered or six-membered ring, which has a C / H ratio greater than 0.8 and / or the characteristic of doping oxygen atoms; Wherein, the molecular weight range of the acrylate copolymer is 10,000-20,000, and the polymer dispersity index PDI is 1.3-1.8; and / or, the proportion range of the R1, R2, and R3 groups: R1: 55-80%; R2: 5-20%; R3: 15-25%.

2. The acrylate copolymer according to claim 1, characterized in that, In the formula (I), R1 includes the following structure: n is 3 - 9; and / or, R2 includes the following structure: and / or, R3 includes the following structure:

3. The acrylate copolymer according to claim 1, characterized in that, It includes polymer ①, polymer ②, and polymer ③; The chemical structure of the polymer ① is shown as follows: The chemical structure of the polymer ② is shown as follows: The chemical structure of the polymer ③ is shown as follows:

4. The preparation method of the acrylate copolymer according to claim 1, characterized in that Firstly, a resin is synthesized by free radical polymerization and then purified by an extraction method; the preparation method includes the following steps: The first step: Firstly, under the conditions of an initiator and heating, acrylate monomers are subjected to a polymerization reaction to synthesize an acrylate copolymer resin shown as the structural formula (I); The second step: Then, the impurities in the first step are removed by a method of adding water and / or alcohols for extraction; the impurities include unreacted monomers and initiators; at the same time, the metal impurities in the system are reduced, and the selected alcohols need to have the characteristic of being miscible with water and the solvent used in the polymerization; The third step: The low-boiling solvents and water are removed by solvent replacement with the solvent used in the photoresist system; an acrylate copolymer shown as the structural formula (I) according to claim 1 is obtained; In the preparation method, by adjusting the miscibility of the water layer and the organic layer, an organic layer concentrated with the copolymer can be obtained, and small molecule impurities and metal impurities can be effectively removed.

5. The preparation method according to claim 4, characterized in that In the first step, the initiator is any one or any combination of two or more of benzoyl peroxide, azodiisobutyric acid, dimethyl azodiisobutyrate, and azodiisobutyronitrile; and / or, In the third step, the steps are: vacuum distillation, and adding solvents used in the photoresist system including ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol methyl ethyl ether, neopentyl acetate, methyl isobutyl ketone, cyclopentanone, cyclohexanone, diacetone alcohol, or γ-butyrolactone; and / or, In the third step, the low-boiling solvents include organic substances immiscible with water such as esters, ketones, ethers, and alcohols; and / or, the boiling point of the low-boiling solvents is 80-180°C.

6. The acrylate copolymer obtained by the preparation method according to any one of claims 4-5, characterized in that, The acrylate copolymer is the acrylate copolymer of the structural formula (I) according to any one of claims 1-3.

7. A polyacrylate leveling agent, characterized in that It contains the acrylate copolymer according to any one of claims 1-3 or according to claim 6.

8. A chemically amplified photoresist, characterized in that, It contains the acrylate copolymer as described in any one of claims 1-3 or claim 6, and / or further includes a base resin, a solvent, a photoacid generator, a quencher, a surfactant and / or an additive.

9. An application, characterized in that, The acrylate copolymer as described in any one of claims 1-3 or claim 6 is applied to the preparation of a chemically amplified photoresist and used as a polyacrylate leveling agent; the chemically amplified photoresist as described in claim 8 is applied to the I-line, KrF-line, ArF-line, and ArFi-line.

10. The method for using the chemically amplified photoresist according to claim 8, characterized in that, The usage method includes the following steps: spin-coating a photoresist on a silicon wafer, pre-baking, exposing, post-baking, and developing to finally obtain a photolithographic pattern; wherein, the temperature of the pre-baking is 70-150 °C; the pre-baking time is 30-180 s; the temperature of the post-baking is 90-200 °C; the post-baking time is 30-180 s; the developer used for the development is an aqueous solution of tetramethylammonium hydroxide; the development time is 30-130 s.

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