Thickening composition, method for manufacturing thickened resist pattern, and method for manufacturing processed substrate

Abstract

[Problem] To provide a thick film composition. [Solution] Provided is a thick film composition containing a polymer (A) containing a repeating unit (A1) represented by formula (a1) and a solvent (B).

Description

Technical Field

[0001] This invention relates to thick film compositions, methods for manufacturing thick film resist patterns, and methods for manufacturing processed substrates. Background Technology

[0002] In recent years, the demand for high integration of LSIs has been growing, requiring more refined resist patterns. To meet this demand, photolithography processes using KrF excimer lasers, ArF excimer lasers, extreme ultraviolet light, short-wavelength X-rays, electron beams, and other methods have been put into practice.

[0003] To obtain a finer pattern, one method involves covering the developed resist pattern, which is formed within a range that can be stably obtained by conventional methods, with a polymer-containing composition to thicken the resist pattern, thereby resulting in a finer aperture or spacing width (e.g., Patent Document 1). This is primarily aimed at increasing the width of the resist pattern, which is achieved by further applying the polymer-containing composition after the resist pattern has been developed.

[0004] In addition, given the need for thicker resist patterns with high aspect ratios, a composition containing vinyl resin and amine compound was developed (Patent Document 2).

[0005] In addition, a technique for fabricating thick-film resist patterns using a solution containing polymer and solvent was studied (Patent Document 3).

[0006] [Existing Technical Documents]

[0007] [Patent Literature]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2014-170190

[0009] [Patent Document 2] Japanese Patent Application Publication No. 2017-165846

[0010] [Patent Document 3] Japanese Patent Application Publication No. 2022-096214 Summary of the Invention

[0011] [The problem the invention aims to solve]

[0012] The inventors noted that in EUV exposure, which is expected to become a high-precision technology, when used as an etching mask, it may not be able to fully exert its durability as a mask, and in the final stage of the etching process, the masked object may be etched away.

[0013] Therefore, the inventors believe that there is still more than one problem that needs to be improved in the method for manufacturing resist patterns. These problems can be listed as follows: making the fine resist pattern thicker; obtaining a fine resist pattern for use as an etching mask; suppressing resist dissolution after applying the thick-film composition to the resist; ensuring that the exposed portion of the thick-film layer can be sufficiently dissolved in the developer; obtaining a resist pattern with sufficient etching resistance; obtaining sufficient resolution even when using an exposure machine with an increased numerical aperture; obtaining a fine pattern with suppressed pattern width deviation; obtaining a resist pattern with a high aspect ratio; widening the process window; and improving the manufacturing yield.

[0014] [Methods used to solve problems]

[0015] The thick film composition according to the invention contains a polymer (A) and a solvent (B), wherein the polymer (A) contains repeating units (A1) represented by formula (a1).

[0016]

[0017] In the formula,

[0018] L 1 L 2 and L 3 Each is independently a single bond, C 1-10 straight-chain alkylene, C 3-10 Branched alkylene, or C 3-10 Cyclic alkylene

[0019] R 1 R 2 and R 3 Each independently represents H and C. 1-10 straight-chain alkyl, C 3-10 Branched alkyl, C 3-10 Cycloalkyl, C 6-15 Aryl or C 6-15 Araneyl groups,

[0020] R 4 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, C 6-15 Aryl, C 6-15 Aryl groups, or any combination thereof,

[0021] Among them, R 4 At least one hydrogen atom can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH substitutions;

[0022] Among them, L 1 L 2 L3 R 1 R 2 R 3 and R 4 At least one non-adjacent methylene group (-CH2-) can be converted by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CR 5 =CR 6 - or -C≡C- can be substituted.

[0023] R 5 and R 6 Each independently is H or C 1-6 Straight-chain alkyl,

[0024] X is O or S.

[0025] n is 0 or 1.

[0026] The method for manufacturing a thick-film resist pattern according to the present invention includes the following steps.

[0027] (1) Applying a resist composition over a substrate to form a resist layer from the resist composition;

[0028] (2a) Expose the resist layer;

[0029] (2b) Applying the above-described thick film composition to the resist layer to form a thick film layer; and

[0030] (2c) Develop the resist layer and the thickened film layer.

[0031] The method for manufacturing a processed substrate according to the present invention includes the following steps.

[0032] Forming the above-mentioned thick-film resist pattern; and

[0033] (3) The thickened resist pattern is used as a mask for processing.

[0034] The method for manufacturing a device according to the present invention includes the method described above.

[0035] This invention relates to the use of a composition comprising a polymer (A) and a solvent (B) for forming a film on a resist layer, wherein the polymer (A) contains repeating units (a1) represented by formula (a1). The structure of the polymer (A) is as described above.

[0036] [The effects of the invention]

[0037] According to the present invention, one or more of the following effects are desirable: making the fine resist pattern thicker; obtaining a fine resist pattern for use as an etching mask; suppressing resist dissolution after applying the thickening composition to the resist; allowing the exposed portion of the thickened layer to dissolve sufficiently in the developer; obtaining a resist pattern with sufficient etching resistance; obtaining sufficient resolution even when using an exposure machine with increased numerical aperture; obtaining a fine pattern with suppressed pattern width deviation; obtaining a resist pattern with a high aspect ratio; widening the process window; and improving manufacturing yield. Attached Figure Description

[0038] [ Figure 1 ] Figure 1 This is a schematic diagram showing one embodiment of a method for manufacturing a thick-film resist pattern. Detailed Implementation

[0039] [Method for carrying out the invention]

[0040] [definition]

[0041] In this specification, unless otherwise specified, the definitions or examples set forth in the following paragraphs shall apply.

[0042] The singular form contains the plural form, and "a" or "the" means "at least one". The elements of a concept can be expressed in multiple ways, and when describing its quantity (e.g., mass % or mole %), the quantity means the sum of these multiple elements.

[0043] "And / or" includes combinations of all elements, as well as cases where elements are used individually.

[0044] When using "~ / to" or "-" to represent a numerical range, it includes both endpoints and the units are the same. For example, 5 mol% to 25 mol% means more than 5 mol% and less than 25 mol%.

[0045] “C x-y “C” x ~C y "and "C x The term "" indicates the number of carbon atoms in a molecule or substituent. For example, C 1-6 Alkyl refers to an alkyl chain having one to six carbon atoms (methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.).

[0046] When a polymer has multiple repeating units, these repeating units are copolymerized. These copolymerizations can be alternating copolymerization, random copolymerization, block copolymerization, graft copolymerization, or a mixture thereof. When polymers or resins are represented by structural formulas, the n, m, etc. appended to parentheses indicate the number of repeats.

[0047] Temperature is measured in Celsius. For example, 20 degrees means 20 degrees Celsius.

[0048] Additives refer to the compound itself that performs this function (e.g., if it is a base-generating agent, it is the compound itself that generates base). It can also be added to the composition in the form of the compound dissolved or dispersed in a solvent. As a form of the present invention, it is preferable that the composition of the present invention contains such a solvent as solvent (B) or other components.

[0049] Aryl refers to a group containing one or more aromatic rings, including phenyl, anthracene, naphthyl, phenanthryl, fluorenyl, pyrene, etc., but not limited to these.

[0050] Arane refers to alkyl groups that have been substituted with aryl groups, including benzyl and phenethyl, but not limited to these.

[0051] The following describes in detail the embodiments of the present invention.

[0052] [Thick Film Forming Composition]

[0053] The thick film composition according to the invention contains a polymer (A) and a solvent (B), wherein the polymer (A) contains repeating units (a1) represented by formula (a1).

[0054] The thick film composition according to the invention can be applied to the resist layer before development or after development.

[0055] In a preferred embodiment, the thickening composition according to the invention is applied to the resist layer before development, but not between the resist patterns after development. However, "development" as used herein does not include development when patterning a removed resist layer. For example, in designs where multiple resist patterning operations are performed consecutively, the thickening composition of the invention can still be used for thickening the resist layer in subsequent processes, even after the resist has been developed in a previous process.

[0056] (A) Polymer

[0057] The polymer (A) used in this invention contains repeating units (A1) represented by formula (a1).

[0058] One characteristic of the thick film composition according to the present invention is that it contains a polymer (A) containing repeating units (A1), thereby enabling further thick film formation.

[0059] The repeating unit (A1) represented by equation (a1) is as follows:

[0060]

[0061] In the formula,

[0062] L 1 L 2 and L 3 Each is independently a single bond, C 1-10 straight-chain alkylene, C 3-10 Branched alkylene, or C 3-10 Cyclic alkylene groups (preferably single bonds or methyl groups; more preferably single bonds).

[0063] R 1 R 2 and R 3 Each independently represents H and C. 1-10 straight-chain alkyl, C 3-10 Branched alkyl, C 3-10 Cycloalkyl, C 6-15 Aryl, or C 6-15 Aryl alkyl group (preferably H or methyl; more preferably H).

[0064] R 4 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, C 6-15 Aryl, C 6-15 Aryl alkyl groups, or any combination thereof. Wherein, R 4 One or more hydrogen atoms can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH can be substituted.

[0065] Where R 4 C 1-15 A straight-chain alkyl group, wherein one or more hydrogen atoms of the straight-chain alkyl group are C-shaped. 1-5 When straight-chain alkyl is substituted, R 4 It can be a branched alkyl group.

[0066] L 1 L 2 L 3 R 1 R 2 R 3 and R 4 One or more non-adjacent methylene groups (-CH2-) can be represented by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CR 5 =CR 6 - or -C≡C- can be substituted, but it is preferable not to be substituted.

[0067] R 5 and R 6 Each independently is H or C 1-6 Straight-chain alkyl, preferably hydrogen or methyl.

[0068] X can be O or S, preferably O.

[0069] n can be 0 or 1, preferably 1.

[0070] Specific examples of compounds that can be read as formula (a1) are detailed below. The following compounds can be read as formula (a1). L 1 L 2 and L 3 For a single bond, R 1 R 2 and R 3 H is H, X is O, R is O 4 A C2 straight-chain alkyl (ethyl) group in which one hydrogen atom is replaced by a hydrogen atom. 10 Cyclic alkyl group (adamantyl group), n is 1.

[0071]

[0072] The following compounds can also be read as formula (a1). L 1 L 2 and L 3 For a single bond, R 1 R 2 and R 3 H is H, X is O, R is O 4 It is a combination of C1 straight-chain alkyl, C6 cyclic alkyl, and C1 straight-chain alkyl with one hydrogen atom replaced by -OH, where n is 1. As shown in this example, when R 4 When it is a combination of multiple substituents, a monovalent substituent can be regarded as a divalent substituent obtained by removing a hydrogen atom, and then combined with other substituents.

[0073]

[0074] R 4 It can also be represented by equation (a2).

[0075] -(R 7 ) p -(R 8 ) q -R 9 (a2)

[0076] In the formula,

[0077] R 7 C 1-15 straight-chain alkylene, C 3-15 Branched alkylene, C 3-15 Cyclic alkylene or phenylene,

[0078] R 8 C 1-15straight-chain alkylene, C 3-15 Branched alkylene, C 3-15 Cyclic alkylene or phenylene,

[0079] R 9 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, phenyl, or benzyl,

[0080] Among them, R 7 R 8 、or R 9 One or more of the hydrogens in any one of them can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH substitutions;

[0081] p and q are each individually 0 or 1.

[0082] Where R 7 R 8 、or R 9 C 1-15 A straight-chain alkyl group, wherein one or more hydrogen atoms of the straight-chain alkyl group are C-shaped. 1-5 When straight-chain alkyl is substituted, R 7 R 8 、or R 9 It can be a branched alkyl group.

[0083] In a preferred embodiment, p and q are 0, and R 9 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, phenyl, or benzyl, R 9 More than one hydrogen atom is C 1-5 Straight-chain alkyl groups, -COOH, or -OH can be substituted. More preferably, p and q are 0, and R... 9 C 1-10 straight-chain alkyl, C 3-10 Branched alkyl, C 3-10 Cycloalkyl, phenyl, or benzyl, R 9 More than one hydrogen atom can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH can be substituted. Further preferred is when p and q are 0, and R... 9 C 1-8 straight-chain alkyl, C 3-8 Branched alkyl, C 3-10 Cycloalkyl, phenyl, or benzyl, R 9 One or more hydrogen atoms can be replaced by -OH.

[0084] In a preferred embodiment, p and q are 1, and R 7 C1-10 Straight-chain alkylene, R 8 C 3-10 Cyclic alkylene, R 9 C 3-10 Straight-chain alkyl, R 9 One or more hydrogen atoms can be replaced by -OH.

[0085] Regarding R 4 Examples of such compounds include: n-propyl, n-butyl, isopropyl, isobutyl, cycloalkyl, 2-ethylhexyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, 4-(hydroxymethyl)cyclohexylmethyl, adamantyl, benzyl, phenyl, 4-hydroxyphenyl, etc.

[0086] Regarding the repeating unit (A1), the following examples can be listed.

[0087]

[0088] For the repeating unit (A1), the carbon atom parameter represented by formula (I) is preferably 2.0 to 5.0, more preferably 2.0 to 4.0, and even more preferably 2.0 to 3.5.

[0089] Carbon atom parameter = (total number of atoms in the repeating unit (A1)) / (number of C atoms in the repeating unit (A1) - number of O atoms in the repeating unit (A1)) (I)

[0090] The same applies to the polymer (A) as a whole; formula (I)' is preferably 2.0 to 5.0, more preferably 2.0 to 4.0, and even more preferably 2.0 to 3.5.

[0091] Carbon atom parameter = (total number of atoms in polymer (A)) / (number of C atoms in polymer (A) - number of O atoms in polymer (A)) (I)

[0092] For the repeating unit (A1), in order to achieve further thickening, the ratio of the annular structure represented by formula (II) is preferably 5% to 80%, more preferably 20% to 80%.

[0093] Ring structure ratio = (sum of atomic weights of all atoms in the ring structure constituting the repeating unit (A1)) / (sum of atomic weights of all atoms in the repeating unit (A1)) × 100 (II)

[0094] The same applies to the polymer (A) as a whole; formula (II)' is preferably 5% to 80%, more preferably 20% to 80%.

[0095] Cyclic structure ratio = (sum of atomic weights of all atoms constituting the cyclic structure in polymer (A)) / (sum of atomic weights of all atoms constituting polymer (A)) × 100 (II)

[0096] Without prejudice to the scope of protection of this invention, polymer (A) may contain repeating units other than repeating unit (A1). Based on the total number of all repeating units constituting polymer (A), the proportion of repeating unit (A1) is preferably 60% to 100%, more preferably 80% to 100%, and even more preferably 95% to 100%. In a further preferred embodiment, polymer (A) is substantially composed of repeating unit (A1), more preferably composed of repeating unit (A1).

[0097] In the molecular weight distribution curve of polymer (A) obtained by gel permeation chromatography (GPC), the ratio of the amount of polymer (A) with a molecular weight of 500 to 10,000 (converted to polystyrene) to the total amount of polymer (A) (hereinafter sometimes referred to as "the ratio of molecular weight 500 to 10,000") is preferably 60% or more, more preferably 70% to 100%, and even more preferably 80% to 100%.

[0098] The ratio of molecular weights between 500 and 10,000 can be obtained in the following way.

[0099] First, in the molecular weight distribution curve of the thick film composition obtained by GPC, the peak with the largest area fraction among the peaks of the molecular weight distribution curve is specifically designated as the peak of polymer (A).

[0100] In the peaks of the specially designated polymer (A), the area in the range of 500 to 10,000 on the X-axis of the molecular weight distribution curve (representing molecular weight in logarithmic terms) is obtained, and the value obtained by dividing this area by the total area of ​​the peaks of polymer (A) and multiplying by 100 can be set as the ratio of the amount of all polymer (A) with a molecular weight of 500 to 10,000 converted from polystyrene.

[0101] The mass-average molecular weight (Mw) of polymer (A) is preferably 500 to 20,000, more preferably 500 to 8,000, even more preferably 800 to 5,000, and even more preferably 1,000 to 3,000. In this invention, mass-average molecular weight (Mw) refers to the average mass molecular weight converted to polystyrene using GPC measurements.

[0102] Although not bound by theory, it can be considered that in the repeating unit (A1), the effects of the present invention can be better achieved by the polymer (A) having a carbon atom parameter of 5.0 or less, a cyclic structure ratio of 5% or more, a molecular weight ratio of 500 to 10,000 of 60% or more, or a mass-average molecular weight of 500 or more, and the following can be deduced.

[0103] First, it can be assumed that when a thick-film composition is applied to a resist layer and a thick-film layer is formed by heating or the like, the polymers in the area where the thick-film layer and the resist layer are in contact will permeate (mix) each other, forming a mixed layer. It can be assumed that the resist pattern can be thickened by forming this mixed layer.

[0104] Therefore, it can be assumed that after the thick film composition is applied to the resist layer, the amount of the thick film composition that penetrates into the resist layer will be reduced, thus effectively inhibiting the dissolution of the resist.

[0105] Furthermore, it can be considered that a thick film layer with sufficient etch resistance can be formed.

[0106] Although not bound by theory, it can be considered that by having a carbon atom parameter of 2.0 or higher, a cyclic structure ratio of 80% or less, or a mass-average molecular weight of 10,000 or less in the repeating unit (A1), the solubility of the exposed portion of the thick film layer in the developer can be further improved. Furthermore, it can be considered that the solubility of the polymer (A) in the solvent (B) can be further improved.

[0107] Based on the total mass of the thick film composition, the content of polymer (A) is preferably 0.01% to 30% by mass, more preferably 0.5% to 20% by mass, and even more preferably 1% to 10% by mass.

[0108] The thick film composition contains polymer (A), and may also contain polymers other than polymer (A). Based on the total mass of the thick film composition, the content of polymers other than polymer (A) is preferably 0% to 20% by mass, more preferably 0% to 10% by mass, further preferably 0% to 5% by mass, and even more preferably 0% by mass (in embodiments excluding polymer (A)).

[0109] (B) Solvent

[0110] Solvent (B) is used to dissolve polymer (A) and other components as needed.

[0111] Solvent (B) is preferably a solvent (B1) represented by formula (b1).

[0112] R 21 -OR 22 (b1)

[0113] In the formula,

[0114] R 21 and R 22 Each independently is C 1-8 Alkyl group. Preferably C14. 3-6Alkyl groups. More preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, isopentyl, cyclopentyl, or cyclohexyl. Further preferably methyl, n-butyl, n-pentyl, isopropyl, cyclopentyl, or cyclohexyl. Even more preferably n-butyl. These are straight-chain, branched, or cyclic, preferably straight-chain or cyclic, more preferably straight-chain.

[0115] R 21 and R 22 They can be different or the same, but the same is preferred.

[0116] Examples of solvents (B1) include: dibutyl ether, dipentyl ether, diisopentyl ether, dicyclopentyl ether, dicyclohexyl ether, cyclopentylmethyl ether, etc.

[0117] In a preferred embodiment, the solvent (B) is preferably composed of solvent (B1) only, and more preferably, it is composed of solvent (B1) only.

[0118] In another preferred embodiment, the solvent (B) preferably contains a solvent (B2) that is different from the solvent (B1), and more preferably it consists only of the solvent (B1) and the solvent (B2).

[0119] Preferably, the solvent (B2) is cyclohexanone, cyclopentanone, propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, γ-butyrolactone, ethyl lactate, 2-propanol (IPA), or any combination thereof. Solvent (B2) is preferably PGME, PGMEA, or a combination thereof. When solvent (B2) contains two solvents, their mass ratio is preferably 100:1 to 1:100, more preferably 50:1 to 1:50, and even more preferably 30:1 to 1:30.

[0120] The solvent (B2) may contain water. Based on solvent (B), the water content is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.001% by mass or less. Solvent (B2) containing no water (0.000% by mass) is also a preferred embodiment of the present invention.

[0121] Although not bound by theory, it can be considered that the solvent (B) of the composition according to the invention can contribute to the formation of thick film patterns by avoiding dissolution of the underlying resist film while dissolving the solid components (components other than solvent (B)).

[0122] Based on the composition according to the invention, the content of solvent (B) is preferably 70% to 99.99% by mass, more preferably 80% to 99.99% by mass, even more preferably 95% to 99.99% by mass, and even more preferably 95% to 99.90% by mass.

[0123] Based on solvent (B), the content of solvent (B1) is preferably 70% to 100% by mass, more preferably 80% to 100% by mass, and even more preferably 90% to 100% by mass.

[0124] Based on solvent (B), the content of solvent (B2) is preferably 0% to 30% by mass, more preferably 0% to 20% by mass, and even more preferably 0.1% to 10% by mass.

[0125] (C) Surfactants

[0126] The thick film composition according to the present invention can further contain a surfactant (C). By containing a surfactant (C), the coatability can be improved. Among the surfactants that can be used in the present invention, examples include: (I) anionic surfactants, (II) cationic surfactants, or (III) nonionic surfactants; more specifically, examples include: (I) alkyl sulfonates, alkylbenzene sulfonic acids, and alkyl benzene sulfonates; (II) laurylpyridinium chloride and lauryl methyl ammonium chloride; and (III) polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene kyne glycol ether, fluorinated surfactants (e.g., Florard (3M), Megafac (DIC), Sulfuron (AGC), and organosiloxane surfactants (e.g., KF-53, KP341 (Shin-etsu Chemical Industry)).

[0127] These surfactants can be used alone or in combination of two or more.

[0128] Based on the total mass of the thick film composition, the content of surfactant (C) is preferably 0% to 5% by mass; more preferably 0.001% to 2% by mass; and even more preferably 0.01% to 1% by mass. The absence of surfactant (C) (0% by mass) is also an embodiment of the present invention.

[0129] (D) Additives

[0130] The thick film composition according to the present invention may further contain additives (D) other than the components (A) to (C) mentioned above. Additives (D) are preferably plasticizers, crosslinking agents, antibacterial agents, bactericides, preservatives, antifungal agents, acids, alkalis, organic salts, or mixtures of at least any of the above.

[0131] Based on the total mass of the thick film composition, the content of additive (D) is preferably 0% to 10% by mass; more preferably 0.001% to 5% by mass; further preferably 0.01% to 4% by mass; and even more preferably 0.1% to 3% by mass. A preferred embodiment of the invention is a thick film composition that does not contain additive (D) (0% by mass).

[0132] <Method for manufacturing thick-film resist patterns>

[0133] The method for manufacturing a thick-film resist pattern according to the present invention includes the following steps.

[0134] (1) Applying a resist composition over a substrate to form a resist layer from the resist composition;

[0135] (2a) Expose the resist layer;

[0136] (2b) Applying the thick-film composition according to the invention to the resist layer to form a thick-film layer; and

[0137] (2c) Develop the resist layer and the thickened film layer.

[0138] The following steps are illustrated using diagrams. For clarity, steps (1), (2a), (2b), and (2c) are performed before step (3). The numbers in parentheses indicating the steps indicate the order. However, the order of (2a), (2b), and (2c) is arbitrary. The same applies below.

[0139] Step (1)

[0140] In step (1), the resist composition is applied over the substrate to form a resist layer.

[0141] Examples of substrates include silicon / silicon dioxide coated substrates, silicon nitride substrates, silicon wafer substrates, glass substrates, and ITO substrates.

[0142] The resist composition is not particularly limited, but from the viewpoint of forming a fine resist pattern with high resolution, a chemically amplified resist composition is preferred. Examples include chemically amplified PHS-acrylate hybrid EUV resist compositions. The presence of a photoacid generator in the resist composition is also a preferred embodiment. A suitable resist composition of the present invention is a positively chemically amplified resist composition.

[0143] The resist composition of the present invention can also use a negative resist composition. Well-known negative resist compositions and processes can be used.

[0144] The resist composition is applied over a substrate by a suitable method. In this invention, "over the substrate" includes both direct application over the substrate and application over layers other than the substrate. For example, a lower resist layer (e.g., spin-on carbon (SOC) and / or adhesion enhancement film) can be formed directly over the substrate, and the resist composition is then applied directly over it. Preferably, the resist composition is applied directly over the substrate. In another preferred embodiment, a SOC is formed directly over the substrate, an adhesion enhancement film is formed directly over the SOC, and the resist composition is then applied directly over it.

[0145] The application method is not particularly limited; for example, coating using spin coating.

[0146] A substrate to which a resist composition has been applied is preferably heated to form a resist layer. This heating, also known as pre-baking, is performed, for example, using a hot plate. The heating temperature is preferably 100°C to 250°C; more preferably 100°C to 200°C; and even more preferably 100°C to 160°C. Here, the temperature refers to the temperature of the heated surface of the hot plate. The heating time is preferably 30 seconds to 300 seconds; more preferably 30 seconds to 120 seconds; and even more preferably 45 seconds to 90 seconds. Heating is preferably performed in an atmospheric or nitrogen atmosphere; more preferably in an atmospheric atmosphere.

[0147] Figure 1 (i) is a schematic diagram of forming a resist layer 2 on a substrate 1. The thickness of the resist layer can be selected according to the purpose, preferably 10 nm to 100 nm; more preferably 10 nm to 40 nm; and even more preferably 10 nm to 30 nm.

[0148] Step (2a)

[0149] In step (2a), the resist layer is exposed through a mask used as needed.

[0150] The wavelength of the radiation (light) used in the exposure is not particularly limited, but exposure with light having a wavelength of 13.5 nm to 248 nm is preferred. Specifically, KrF excimer lasers (wavelength 248 nm), ArF excimer lasers (wavelength 193 nm), and EUV (extreme ultraviolet light, wavelength 13.5 nm) can be used. EUV light is more preferred. These wavelengths allow for a deviation range of ±1%.

[0151] After exposure, post-exposure heating (PEB) can be performed as needed. The PEB temperature can be selected from the range of 70°C to 150°C; preferably, it can be selected from the range of 80°C to 120°C. The PEB heating time can be selected from the range of 0.3 minutes to 5 minutes; preferably, it can be selected from the range of 0.5 minutes to 2 minutes.

[0152] Figure 1 (ii) is a schematic diagram showing the state in which the resist layer 2 is exposed through a mask when using a typical positive chemical amplification resist composition. Acid is released from the photoacid generator into the exposed section 4, thereby deprotecting the polymer and increasing its alkali solubility. In the unexposed section 3, the alkali solubility of the polymer remains unchanged.

[0153] Step (2b)

[0154] In step (2b), a thick film composition containing polymer (A) and solvent (B) is applied to the resist layer to form a thick film layer.

[0155] The application method is not particularly limited; for example, coating using spin coating.

[0156] The substrate to which the thick film composition is applied is preferably formed into a thick film layer by heating or spin drying (more preferably by heating). Heating is performed using, for example, a hot plate. The heating temperature is preferably 45°C to 150°C; more preferably 60°C to 130°C. The heating time is preferably 30 seconds to 180 seconds; more preferably 45 seconds to 90 seconds. Heating is preferably performed in an atmospheric or nitrogen atmosphere; more preferably in an atmospheric atmosphere. The heating in (2b) is also referred to as mixed baking.

[0157] Figure 1 (iii) is a schematic diagram of the state in which a thick film layer 5 is formed on the resist layer 2.

[0158] In step (2b), it is preferable to form an insoluble layer in the region near the contact between the thickened layer and the photoresist layer. Although not bound by theory, it can be considered that the polymers of the thickened layer and the photoresist layer will permeate (mix) each other in the region where they contact, forming a mixed layer. Whether the mixed layer is soluble or insoluble in the developing solution of the subsequent developing step depends on whether the underlying photoresist layer is soluble or insoluble in the developing solution. If the region of the underlying photoresist layer is insoluble in the developing solution, the mixed layer is an insoluble layer. If the region of the underlying photoresist layer is soluble in the developing solution, the mixed layer is also soluble.

[0159] The following explanation uses a positive resist layer as an example. The exposed portion of the resist layer is soluble in the developer; therefore, the resist layer (matrix component, preferably a polymer) that penetrates into the mixed layer in the same area will dissolve, and the mixed layer will also dissolve. Furthermore, the exposed portion of the resist layer below the mixed layer will also dissolve. On the other hand, the unexposed portion of the resist layer is insoluble in the developer (e.g., it has not been deprotected). Therefore, the resist layer that penetrates into the mixed layer in the same area will not dissolve, and the mixed layer will not dissolve. Furthermore, the unexposed portion of the resist layer below the mixed layer will not dissolve.

[0160] Figure 1 (iv) is a schematic diagram showing the state in which the insoluble layer 6 is formed. A mixed layer is also formed in the area where it will dissolve (the exposed area if it is a positive type), but it will be removed during the development process, so it is not shown in (iv) for the sake of convenience.

[0161] In step (2b), it is also preferable to perform rinsing after the formation of the thick film layer to remove the upper part of the thick film layer (the thick film layer above the mixing layer). The rinsing can be performed using a solvent with the same composition as the solvent (B) of the thick film composition. The rinsing in this invention differs from the development described later. That is, the rinsing is not used to dissolve soluble areas of the resist layer to form a resist pattern.

[0162] Step (2c)

[0163] In step (2c), the resist layer or the resist layer and the thickened layer are developed.

[0164] Examples of methods for applying the developer include: immersion, dipping, and spraying. The temperature of the developer is preferably 5°C to 50°C; more preferably 25°C to 40°C. The development time is preferably 15 seconds to 120 seconds; more preferably 30 seconds to 60 seconds. After applying the developer, it is removed. The developed resist pattern can also be rinsed. Rinsing can preferably be performed using water (DIW).

[0165] The developer is preferably an alkaline aqueous solution or an organic solvent; more preferably an alkaline aqueous solution. Examples of alkaline aqueous solutions include: aqueous solutions containing inorganic bases such as sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium silicate; organic amines such as ammonia, ethylamine, propylamine, diethylamine, diethylaminoethanol, and triethylamine; and quaternary ammonium hydroxide such as tetramethylammonium hydroxide (TMAH); more preferably, an aqueous solution of TMAH; and even more preferably, a 2.38% by mass aqueous solution of TMAH.

[0166] The aforementioned surfactants can also be further added to the developer.

[0167] The order of (2a), (2b), and (2c) is arbitrary. Since exposure can be avoided when penetrating the thick film layer, it is more preferable to perform process (2b) after (2a). It is also feasible to perform process (2a) after (2b), in which case it is preferable to control the effect of penetrating the thick film layer before exposure. Since the development process only needs to be performed once, it is preferable to perform (2c) after (2a) and (2b). In the preferred embodiment of the present invention, steps (2a), (2b), and (2c) are performed in this order.

[0168] Figure 1 (v) shows the state where the developer is applied to the resist layer and the thickened layer, the developer is removed, and the thickened resist pattern 7 is formed.

[0169] If the thickness is defined as (height of the thickened resist pattern) - (height of the resist pattern formed in the same manner except without the thickened composition), the thickness is preferably 2 nm to 20 nm; more preferably 2 nm to 15 nm; further preferably 5 nm to 10 nm; and even more preferably 5.5 nm to 8 nm. Although not bound by theory, the thickness of the resist film is usually thin in high-precision lithography techniques such as EUV exposure, it can be considered that by using the present invention to thicken it, the durability of the mask can be ensured when used in subsequent steps, such as as an etching mask.

[0170] <Methods for Manufacturing Processed Substrates and Devices>

[0171] The method for manufacturing a processed substrate according to the present invention includes the following steps.

[0172] Forming the thick-film resist pattern described above; and

[0173] (3) The thickened resist pattern is used as a mask for processing.

[0174] Step (3)

[0175] In step (3), the resist pattern that has been thickened is used as a mask for processing.

[0176] The thickened resist pattern is preferably used for processing the resist underlayer or substrate (more preferably the substrate). Specifically, the resist pattern can be used as a mask to process various substrates as substrates using methods such as dry etching, wet etching, ion implantation, and metal plating. Since the resist pattern is thickened, it can function as a mask even under more demanding conditions, and is therefore preferably used for processing using dry etching.

[0177] When using a thickened resist pattern to fabricate the underlying resist film, the process can be performed in stages. For example, a adhesion enhancement film and a SOC can be fabricated using a resist pattern, and a substrate can be fabricated using a SOC pattern. The adhesion enhancement film can use, for example, SiARC (Si antireflective coating).

[0178] The method for manufacturing a device according to the present invention includes the above-described method, and optionally further includes the step of forming wiring on a processed substrate. These processes can be performed using well-known methods. Subsequently, as needed, the substrate is cut into wafers, connected to a lead frame, and encapsulated using resin. In this invention, the encapsulated device is referred to as a device. Examples of devices include: semiconductor devices, liquid crystal display devices, organic EL display devices, plasma display devices, and solar cell devices, preferably semiconductor devices.

[0179] This invention relates to the use of a composition comprising a polymer (A) and a solvent (B) for forming a film on a resist layer, wherein the polymer (A) contains repeating units (A1) represented by formula (a1). Preferred embodiments of the polymer (A) and solvent (B) are as described above. The composition comprising the polymer (A) and solvent (B) is preferably a thick film composition, and preferred embodiments are as described above.

[0180] [Example]

[0181] The present invention will be described below through various embodiments. However, the embodiments of the present invention are not limited to these embodiments.

[0182] [Synthesis of Polymer (A)]

[0183] (1) Synthesis of poly(cyclohexylvinyl ether)

[0184] A 100 mL three-necked flask was dried for 10 minutes under nitrogen atmosphere using a hot air gun. Then, 32 mL of a 5.25 mmol / L solution of n-butylammonium bromide and dichloromethane was prepared in the flask. Next, 4 mL of a 40 mmol / L dichloromethane solution of trifluoromethane was added to the flask using a dry syringe. The solution was brought to -40°C, and 4 mL of cyclohexyl vinyl ether was added, allowing the reaction to proceed for 27 hours. The reaction was then terminated by adding a solution of 5 mL of 0.1% (w / w) ammonia solution and 5 mL of ethanol. The mixture was washed three times with 30 mL of water, and after stirring for 5 minutes with 10 g of magnesium sulfate, the solid was filtered off. The resulting mixture was then subjected to reduced pressure to remove the solvent. Subsequently, it was dried at room temperature for more than 3 hours under reduced pressure using vacuum to obtain poly(cyclohexylvinyl ether) (Mw: 1800, PDI (Poly Dispersity Index) = 1.9) in 82% yield.

[0185] (2) Synthesis of poly(isobutyl vinyl ether)

[0186] The cyclohexyl vinyl ether used in synthesis (1) was replaced with isobutyl vinyl ether, and the synthesis was carried out using the same method. The poly(isobutyl vinyl ether) at this time had a Mw of 1960, a PDI of 2.1, and a yield of 76%.

[0187] (3) Synthesis of poly(isopropyl vinyl ether)

[0188] The cyclohexyl vinyl ether used in synthesis (1) was replaced with isopropyl vinyl ether, and the synthesis was carried out using the same method. The poly(isopropyl vinyl ether) at this time had a Mw of 2040, a PDI of 2.0, and a yield of 73%.

[0189] [Preparation of compositions of Examples 1-3 and Reference Example 1]

[0190] The polymer (A) listed in Table 1 was dissolved in solvent (B) dibutyl ether. The content of polymer (A) was 1.0% by mass relative to the total mass of the composition. The resulting solution was stirred at room temperature for 60 minutes. After visually confirming that the solute was completely dissolved, the solution was filtered through a 0.2 μm fluoropolymer filter to obtain the compositions of Examples 1-3.

[0191] In Reference Example 1, cyclohexyl vinyl ether (molecular weight 126.2, carbon atom parameter 3.3) was used as a monomer instead of polymer (A), and the same preparation was carried out as described above to obtain the composition of Reference Example 1.

[0192] [Table 1]

[0193]

[0194] In the table,

[0195] -P1: Poly(cyclohexylvinyl ether), Mw 1,800, carbon atom parameter 3.3, cyclic structure ratio 65%.

[0196]

[0197] -P2: Poly(isobutylvinyl ether), Mw 1,960, carbon atom parameter 3.8,

[0198]

[0199] -P3: Poly(isopropyl vinyl ether), Mw 2,040, carbon atom parameter 4.0,

[0200]

[0201] -M1: Cyclohexyl vinyl ether, molecular weight 126.2, carbon atom parameter 3.3.

[0202] [Determination of mass-average molecular weight (Mw)]

[0203] The mass-average molecular weight (Mw) of the compositions in Examples 1-3 and Reference Example 1 was determined by gel permeation chromatography (detector: differential refractometer) using monodisperse polystyrene as a standard, under analytical conditions of two GPC columns (two "G2000HXL" and one "G3000HXL" from Tosoh Corporation), a flow rate of 1.0 ml / min, tetrahydrofuran (Kishida Kagalu) as the dissolution solvent, and a column temperature of 40°C. The samples were prepared by dissolving the polymer in tetrahydrofuran to a 0.5 wt% solution, then filtered and analyzed using a 0.2 μm PTFE filter.

[0204] [Calculation of the ratio of molecular weights between 500 and 10,000]

[0205] For the compositions of Examples 1-3 and Reference Example 1, molecular weight distribution curves were obtained by gel permeation chromatography in the same manner as described above. The peak with the largest area fraction among the peaks of the molecular weight distribution curve was designated as the peak of polymer (A).

[0206] Within the peaks of polymer (A), the area in the range of 500–10,000 on the X-axis of the molecular weight distribution curve (representing molecular weight in logarithmic terms) is calculated. This area is divided by the total area of ​​the peaks of polymer (A) and multiplied by 100. This value is taken as the ratio of the amount of polymer (A) with a molecular weight of 500–10,000 converted to polystyrene. The results are recorded in Table 1.

[0207] [Evaluation of film thickness variation]

[0208] The silicon substrate was treated with HMDS (hexamethyldisilazane) at 90°C for 30 seconds. An EUV chemically amplified PHS-acrylate mixed resist composition (positive type) was spin-coated onto the HMDS-treated substrate, and heated at 110°C for 60 seconds using a hot plate to form a resist layer with a thickness of 35 nm. The composition of Example 1 was poured onto the resist layer, covering it with the composition of Example 1, and left to stand for 60 seconds. Afterward, the substrate was spun at high speed to dry. The film thickness at this point was measured using an Ellipsometer M-2000 (JAWoollam). The thickness obtained by subtracting the resist layer thickness (35 nm) from this initial film thickness is defined as the thickness allowance, and the results are recorded in Table 1.

[0209] The film thickness variation was evaluated based on the following criteria, and the results are recorded in Table 1.

[0210] A: 5.0nm < Thickness of film ≤ 10.0nm

[0211] B: Thickness of film ≤ 5.0 nm

[0212] The compositions of Examples 2, 3 and Reference Example 1 were evaluated in the same manner.

[0213] [LWR Evaluation]

[0214] The silicon substrate was subjected to HMDS treatment at 90°C for 30 seconds. An EUV chemically amplified PHS-acrylate mixed resist composition (positive type) was applied to the HMDS-treated substrate by spin coating, and heated at 110°C for 60 seconds using a hot plate to form a resist layer with a thickness of 35 nm. While varying the exposure, the resist layer was exposed using an EUV exposure apparatus (NXE: 3300B, ASML) through an 18 nm (line:space = 1:1) mask. Afterwards, post-exposure heating (PEB) was performed at 100°C for 60 seconds. Then, the composition of Example 1 was applied to the resist layer by spin coating, and heated at 90°C for 60 seconds to form a thick film. Subsequently, a 2.38% by mass TMAH aqueous solution was used as the developer, and spin-dip development was performed for 30 seconds. Water was added dropwise while the substrate was rotated, replacing the developer with water. The substrate was then rotated at high speed to dry the thickened resist pattern of Example 1. The thickened resist pattern was observed using a CG6300 SEM (Hitachi High Technologies), and the line width and line width roughness (LWR) values ​​were measured. The value ((LWR value / line width) × 100) was calculated and set as X. The results were evaluated according to the following criteria and are recorded in Table 1.

[0215] A: X≦20

[0216] B: X > 20

[0217] The compositions of Examples 2, 3 and Reference Example 1 were evaluated in the same manner.

[0218] [Evaluation of Etching Resistance]

[0219] The silicon substrate was subjected to HMDS treatment at 90°C for 30 seconds. An EUV-enhanced chemically amplified PHS-acrylate mixed resist composition (positive type) was spin-coated onto the HMDS-treated substrate, and heated at 110°C for 60 seconds using a hot plate to form a resist layer with a thickness of 35 nm. The composition from Example 1 was spin-coated onto the resist layer, and heated at 90°C for 60 seconds to form a thickened film. The resulting substrate was placed in a dry etching apparatus, and plasma etching was performed for 15 seconds at a substrate temperature of 23°C using a mixed gas of CF4 (5 mL / min), O2 (10 mL / min), and Ar (500 mL / min). Afterward, the amount of residual resist film was measured using an Ellipsometer M-2000 (JAWoollam). This residual amount is designated as Y1. A higher residual amount indicates better plasma etching resistance.

[0220] As a comparison, a 35nm thick resist layer was etched in the same manner as described above, and the amount of residual film was measured. This amount of residual film is then designated as Y2.

[0221] Calculate Y = Y1 / Y2 × 100, evaluate according to the following criteria, and record the results in Table 1.

[0222] A: 110 < Y

[0223] B: 100 < Y ≤ 110

[0224] The compositions of Examples 2, 3 and Reference Example 1 were evaluated in the same manner.

[0225] [Symbol Explanation]

[0226] 1: Substrate

[0227] 2: Resist layer

[0228] 3: Unexposed Department

[0229] 4: Exposure Department

[0230] 5: Thick film layer

[0231] 6: Insoluble layer

[0232] 7: Thick-filmed resist pattern

[0233] 8: Height of the resist pattern after thickening.

Claims

1. A thick-film composition comprising a polymer (A) and a solvent (B), wherein the polymer (A) contains repeating units (A1) represented by formula (a1): In the formula, L 1 L 2 and L 3 Each is independently a single bond, C 1-10 straight-chain alkylene, C 3-10 Branched alkylene, or C 3-10 Cyclic alkylene; R 1 R 2 and R 3 Each independently represents H and C. 1-10 straight-chain alkyl, C 3-10 Branched alkyl, C 3-10 Cycloalkyl, C 6-15 Aryl or C 6-15 Aryl alkyl groups; R 4 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, C 6-15 Aryl, C 6-15 Aryl alkyl groups, or any combination thereof; in, R 4 At least one hydrogen atom can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH can be substituted; Among them, L 1 L 2 L 3 R 1 R 2 R 3 and R 4 At least one non-adjacent methylene group (-CH2-) can be represented by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, or -CR. 5 =CR 6 - or -C≡C- can be substituted; R 5 and R 6 Each independently is H or C 1-6 Straight-chain alkyl; X is either O or S; n is 0 or 1.

2. The thick film composition according to claim 1, wherein, R 4 This can be expressed by equation (a2): -(R 7 ) p -(R 8 ) q -R 9 (a2) In the formula, R 7 C 1-15 straight-chain alkylene, C 3-15 Branched alkylene, C 3-15 Cyclic alkylene or phenylene, R 8 C 1-15 straight-chain alkylene, C 3-15 Branched alkylene, C 3-15 Cyclic alkylene or phenylene, R 9 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, phenyl, or benzyl, Among them, R 7 R 8 、or R 9 At least one hydrogen atom in either of them can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH substitutions; p and q are each individually 0 or 1.

3. The thick-film composition according to claim 1 or 2, wherein, The polymer (A) has a mass-average molecular weight of 500 to 20,000.

4. The thick-film composition according to one or more of claims 1 to 3, wherein, In the molecular weight distribution curve of polymer (A) obtained by gel permeation chromatography, the amount of polymer (A) with a molecular weight of 500 to 10,000 (based on polystyrene) accounts for more than 60% of the total amount of polymer (A).

5. The thick-film composition according to one or more of claims 1 to 4, wherein, The carbon atom parameters represented by equation (I) are 2.0–5.0: Carbon atom parameter = (total number of atoms in repeating unit (A1)) / (number of C atoms in repeating unit (A1) - number of O atoms in repeating unit (A1))(I).

6. The thick-film composition according to one or more of claims 1 to 5, wherein, The ratio of ring structures represented by formula (II) is 5-80%. The ring structure ratio = (the sum of the atomic weights of all atoms in the ring structure that make up the repeating unit (A1)) / (the sum of the atomic weights of all atoms in the repeating unit (A1)) × 100 (II).

7. The thick-film composition according to one or more of claims 1 to 6, wherein, L 1 L 2 and L 3 It is a single key.

8. The thick-film composition according to one or more of claims 1 to 7, wherein, L 1 L 2 and L 3 For H.

9. The thick-film composition according to one or more of claims 1 to 8, wherein, Based on the total mass of the thick film composition, the content of polymer (A) is 0.01% to 30% by mass.

10. The thick-film composition according to one or more of claims 1 to 9, wherein, The solvent (B) contains a solvent (B1) represented by formula (b1). R 21 -OR 22 (b1) In the formula, R 21 and R 22 Each can be a linear, branched, or cyclic C-chain. 1-8 alkyl; Optionally, based on the thick film composition, the content of the solvent (B) is 70% to 99.99% by mass; or Optionally, the content of solvent (B1) is 70% to 100% by mass, based on solvent (B).

11. A method for manufacturing a thick-film resist pattern, comprising the following steps: (1) Applying a photoresist composition over a substrate to form a photoresist layer from the photoresist composition (preferably by heating); (2a) Expose the resist layer (preferably by EUV light); (2b) Applying the thick film composition according to one or more of claims 1 to 10 to the resist layer (preferably by heating or rotary drying) to form a thick film layer; as well as (2c) Develop the resist layer and the thick film layer (preferably using an alkaline aqueous solution or an organic solvent; more preferably using an alkaline aqueous solution).

12. The method according to claim 11, wherein, Further includes: After the thick film layer is formed in step (2b), the upper part of the thick film layer is removed by rinsing.

13. The method according to claim 11 or 12, wherein, This resist composition is a chemically amplified resist composition.

14. The method according to one or more of claims 11 to 13, wherein, The resist composition further contains a photoacid generator.

15. A method for manufacturing a processed substrate, comprising the following steps: Forming a thick-film resist pattern according to one or more of claims 11 to 14; as well as (3) The thickened resist pattern is used as a mask for processing.

16. A method of manufacturing a device, comprising the method according to claim 15; Optionally, it further includes the step of forming wiring on the processed substrate; or Optionally, the device is a semiconductor device.

17. Use of a composition comprising a polymer (A) and a solvent (B) for forming a film on a resist layer, wherein the polymer (A) comprises a repeating unit (a1) represented by formula (a1): In the formula, L 1 L 2 and L 3 Each is independently a single bond, C 1-10 straight-chain alkylene, C 3-10 Branched alkylene, or C 3-10 Cyclic alkylene R 1 R 2 and R 3 Each independently represents H and C. 1-10 straight-chain alkyl, C 3-10 Branched alkyl, C 3-10 Cycloalkyl, C 6-15 Aryl or C 6-15 Aryl groups, R 4 C 1-15 straight-chain alkyl, C 3-15 Branched alkyl, C 3-15 Cycloalkyl, C 6-15 Aryl, C 6-15 Aryl groups, or any combination thereof, in, R 4 At least one hydrogen atom can be C 1-5 Straight-chain alkyl groups, -COOH, or -OH substitutions; Among them, L 1 L 2 L 3 R 1 R 2 R 3 and R 4 At least one non-adjacent methylene group (-CH2-) can be represented by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, or -CR. 5 =CR 6 - or -C≡C- can be substituted. R 5 and R 6 Each independently is H or C 1-6 Straight-chain alkyl, X is O or S. n is 0 or 1.

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