Polymer comprising repeat units with photoacid-generating functionality and base-solubility-enhancing functionality, and associated photoresist composition and electronic device forming method

A polymer includes repeat units, most of which are photoacid-generating repeat units. Each of the photoacid-generating repeat units includes photoacid-generating functionality and base-solubility-enhancing functionality. Each of the photoacid-generating repeat units comprises an anion and a photoacid-generating cation that collectively have structure (I)wherein q, r, R1, m, X, and Z− are defined herein. The polymer is useful as a component of a photoresist composition that further includes a second polymer that exhibits a change in solubility in an alkali developer under action of acid.

FIELD

The present invention relates to photoacid-generating polymers useful as components of photoresist compositions.

INTRODUCTION

As feature sizes of integrated circuits continue to shrink, next generation lithographic processes struggle to fit the stringent requirements to extend Moore's Law. It has long been recognized that increased photoacid generator (PAG) non-uniformity and acid diffusion have limited photoresist resolution, worsened line width roughness (LWR) (see, e.g., Nakamura et. al., Proc. SPIE 2013, 8682, 86821H-1), limited exposure latitude, and generally degraded photolithographic performance for chemically amplified resists. In the past, polymer-bound-PAG (PBP) systems have been implemented to increase PAG uniformity and control acid diffusion (see, e.g., Oh et. al., Proc. SPIE 2008, 7140 714031, pages 1-9; and U.S. Pat. No. 5,945,250 B2 to Aoai et al.). More recently, increased concentration of PAG in the matrix has been shown to further enhance lithographic performance, particularly when combined with a PBP system (U.S. Patent Application Publication No. US 2014/0080062 A1 of Thackeray et. al.). Despite these advances, there remains a need for photoresist compositions providing one or more of decreased critical dimension uniformity, decreased dose to clear energy, and increased contrast slope.

SUMMARY

One embodiment is a polymer comprising, based on 100 mole percent of total repeat units, 50 to 100 mole percent of photoacid-generating repeat units; wherein each of the photoacid-generating repeat units comprises an anion, a photoacid-generating cation, and base-solubility-enhancing functionality; wherein either the anion or the photoacid-generating cation is polymer-bound; wherein the base-solubility-enhancing functionality is selected from the group consisting of tertiary carboxylic acid esters, secondary carboxylic acid esters wherein the secondary carbon is substituted with at least one unsubstituted or substituted C6-40aryl, acetals, ketals, lactones, sultones, alpha-fluorinated esters, beta-fluorinated esters, alpha,beta-fluorinated esters, polyalkyleneglycols, alpha-fluorinated alcohols, and combinations thereof, and wherein the combination of the anion and the photoacid-generating cation has the structure (I)

wherein q is independently in each photoacid-generating repeat unit 0, 1, 2, 3, 4, or 5; r is independently at each occurrence in each photoacid-generating repeat unit 0, 1, 2, 3, or 4; R1is independently at each occurrence in each photoacid-generating repeat unit halogen, unsubstituted or substituted C1-40hydrocarbyl, or unsubstituted or substituted C1-40hydrocarbylene; m is independently in each photoacid-generating repeat unit 0 or 1; X is independently in each photoacid-generating repeat unit a single bond, —O—, —S—, —C(═O)—, —C(R2)2—, —C(R2)(OH)—, —C(═O)O—, —C(═O)N(R2)—, —C(═O)C(═O)—, —S(═O)—, or —S(═O)2—, wherein R2is independently at each occurrence hydrogen or C1-12hydrocarbyl; and Z−is a free or monovalent monoanion.

Another embodiment is a photoresist composition comprising the polymer and a solvent.

Another embodiment is a method of forming an electronic device, comprising: (a) applying a layer of the photoresist composition on a substrate; (b) pattern-wise exposing the photoresist composition layer to activating radiation; and (c) developing the exposed photoresist composition layer to provide a resist relief image.

These and other embodiments are described in detail below.

DETAILED DESCRIPTION

The present inventors have determined that the photolithographic performance of a photoresist composition can be improved by the incorporation of a polymer that includes a majority of photoacid-generating repeat units, wherein each of the photoacid-generating repeat units comprises photoacid-generating functionality and base-solubility-enhancing functionality. The improvement in photolithographic performance can be manifested as one or more of decreased critical dimension uniformity, decreased dose to clear energy, and increased contrast slope.

Thus, one embodiment is a polymer comprising, based on 100 mole percent of total repeat units, 50 to 100 mole percent of photoacid-generating repeat units; wherein each of the photoacid-generating repeat units comprises an anion, a photoacid-generating cation, and base-solubility-enhancing functionality; wherein either the anion or the photoacid-generating cation is polymer-bound; wherein the base-solubility-enhancing functionality is selected from the group consisting of tertiary carboxylic acid esters, secondary carboxylic acid esters wherein the secondary carbon is substituted with at least one unsubstituted or substituted C6-40aryl, acetals, ketals, lactones, sultones, alpha-fluorinated esters, beta-fluorinated esters, alpha,beta-fluorinated esters, polyalkyleneglycols, alpha-fluorinated alcohols, and combinations thereof; and wherein the combination of the anion and the photoacid-generating cation has the structure (I)

wherein q is independently in each photoacid-generating repeat unit 0, 1, 2, 3, 4, or 5; r is independently at each occurrence in each photoacid-generating repeat unit 0, 1, 2, 3, or 4; R1is independently at each occurrence in each photoacid-generating repeat unit halogen, unsubstituted or substituted C1-40hydrocarbyl, or unsubstituted or substituted C1-40hydrocarbylene; m is independently in each photoacid-generating repeat unit 0 or 1; X is independently in each photoacid-generating repeat unit a single bond, —O—, —S—, —C(═O)—, —C(R2)2—, —C(R2)(OH)—, —C(═O)O—, —C(═O)N(R2)—, —C(═O)C(═O)—, —S(═O)—, or —S(═O)2—, wherein R2is independently at each occurrence hydrogen or C1-12hydrocarbyl; and Z−is a free or monovalent monoanion.

Within the range of 50 to 100 mole percent, the content of photoacid-generating repeat units can be 60 to 100 mole percent, specifically 70 to 100 mole percent, more specifically 80 to 100 mole percent, even more specifically 90 to 100 mole percent, still more specifically 95 to 100 mole percent. As used herein, the term “repeat unit” refers to divalent unit that is the residue of a polymerizable monomer. Conversely, “repeat unit” does not include monovalent groups, such as a terminal group derived from a polymerization initiator.

Each of the photoacid-generating repeat units comprises an anion, a photoacid-generating cation, and base-solubility-enhancing functionality. The combination of the anion and the photoacid-generating cation has the structure (I)

wherein q is independently in each photoacid-generating repeat unit 0, 1, 2, 3, 4, or 5; r is independently at each occurrence in each photoacid-generating repeat unit 0, 1, 2, 3, or 4; R1is independently at each occurrence in each photoacid-generating repeat unit halogen, unsubstituted or substituted C1-40hydrocarbyl, or unsubstituted or substituted C1-40hydrocarbylene; m is independently in each photoacid-generating repeat unit 0 or 1; X is independently in each photoacid-generating repeat unit a single bond, —O—, —S—, —C(═O)—, —C(R2)2—, —C(R2)(OH)—, —C(═O)O—, —C(═O)N(R2)—, —C(═O)C(═O)—, —S(═O)—, or —S(═O)2—, wherein R2is independently at each occurrence hydrogen or C1-12hydrocarbyl; and Z−is a free or monovalent monoanion. As used herein, the term “hydrocarbyl”, whether used by itself, or as a prefix, suffix, or fragment of another term, refers to a residue that contains only carbon and hydrogen unless it is specifically identified as “substituted hydrocarbyl”. The hydrocarbyl residue can be aliphatic or aromatic, straight-chain, cyclic, bicyclic, branched, saturated, or unsaturated. It can also contain combinations of aliphatic, aromatic, straight chain, cyclic, bicyclic, branched, saturated, and unsaturated hydrocarbon moieties. When the hydrocarbyl residue is described as substituted, it can contain heteroatoms in addition to carbon and hydrogen.

When the photoacid-generating cation is polymer-bound, then the photoacid-generating cation is monovalent and Z−is a free monoanion. Conversely, when Z−is polymer bound, then the photoacid-generating cation is a free cation, and Z−is a monovalent monoanion.

In addition to photoacid-generating functionality, each photoacid-generating repeat unit comprises base-solubility-enhancing functionality. Base-solubility-enhancing functionality includes functional groups that are base-soluble (e.g., polyalkyleneglycols, alpha-fluorinated alcohols); functional groups that are base-soluble after acid-catalyzed deprotection (e.g., tertiary esters, acetals, ketals, secondary carboxylic acid esters wherein the secondary carbon is substituted with at least one unsubstituted or substituted C6-40aryl); and functional groups that are base-soluble after base-catalyzed deprotection (e.g., fluorinated esters, lactones, sultones). Examples of base-solubility-enhancing functionality include tertiary carboxylic acid esters, secondary carboxylic acid esters wherein the secondary carbon is substituted with at least one unsubstituted or substituted C6-40aryl, acetals, ketals, lactones, sultones, alpha-fluorinated esters, beta-fluorinated esters, alpha,beta-fluorinated esters, polyalkyleneglycols, alpha-fluorinated alcohols, and combinations thereof. In some embodiments, the base-solubility-enhancing functionality is a tertiary carboxylic acid ester, an acetal, a ketal, a lactone, or a combination thereof. In some embodiments, the base-solubility-enhancing functionality is a tertiary carboxylic acid ester, a lactone, or a combination thereof. The base-solubility-enhancing functionality can reside in the anion or the photoacid-generating cation. In some embodiments, base-solubility-enhancing functionality resides in a photoacid-generating cation.

In some embodiments of the polymer, the photoacid-generating repeat units are derived from a single monomer. Alternatively, the photoacid-generating repeat units can be derived from at least two different monomers.

The polymer comprises 50 to 100 mole percent of photoacid-generating repeat units, based on 100 mole percent of total repeat units. When the polymer comprises less than 100 mole percent of photoacid generating repeat units, the other repeat units can comprise photoacid-generating functionality or not, and they can comprise base-solubility-enhancing functionality or not. Examples of monomers from which such other repeat units can be derived are

In some embodiments, the polymer has a weight average molecular weight of 2,500 to 10,000 daltons, specifically 3,000 to 7,000 daltons.

In some embodiments, the photoacid-generating functionality comprises a polymer-bound anion and a non-polymer-bound cation. For example, in some embodiments, each of the photoacid-generating repeat units independently has the structure

wherein R3is independently in each of the repeat units H, F, —CN, C1-10alkyl, or C1-10fluoroalkyl; n is independently in each of the repeat units 0 or 1; L1and L3are each independently in each of the repeat units an unsubstituted or substituted C1-20hydrocarbylene, wherein the substituted C1-20hydrocarbylene can, optionally, comprise one or more in-chain divalent heteroatom-containing groups that is —O—, —S—, —NR4—, —PR4—, —C(O)—, —OC(O)—, —C(O)O—, —OC(O)O—, —N(R4)C(O)—, —C(O)N(R4)—, —OC(O)N(R4)—, —N(R4)C(O)O—, —S(O)—, —S(O)2—, —N(R4)S(O)2—, —S(O)2N(R4)—, —OS(O)2—, or —S(O)2O—, wherein R4is H or C1-12hydrocarbyl; L2is independently in each of the repeat units —O—, —C(O)—, or —N(R5)—, wherein R5is H or C1-12hydrocarbyl; and q, r, R1, m, and X are defined for structure (I).

In other embodiments, the photoacid-generating functionality comprises a polymer-bound cation and a non-polymer-bound anion. For example, in some embodiments, in each of the photoacid-generating repeat units one occurrence of R1is present in structure (II) or (II) (i.e., one occurrence of R1is associated with a non-zero occurrence of q or r), covalently links the photoacid-generating cation to the polymer, and has the structure

wherein R3is independently in each of the repeat units H, F, —CN, C1-10alkyl, or C1-10fluoroalkyl; L4is independently in each of the repeat units 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, —C(O)O—, —C(O)C(O)—, or —C(O)N(R5)—, wherein R5is H or C1-12hydrocarbyl; p is independently in each of the repeat units 0 or 1; and L5is independently in each of the repeat units an unsubstituted or substituted C1-20hydrocarbylene, wherein the substituted C1-20hydrocarbylene can, optionally, comprise one or more in-chain divalent heteroatom-containing groups that is —O—, —S—, —NR4, —PR4—, —C(O)—, —OC(O)—, —C(O)O—, —OC(O)O—, —N(R4)C(O)—, —C(O)N(R4)—, —OC(O)N(R4)—, —N(R4)C(O)O—, —S(O)—, —S(O)2—, —N(R4)S(O)2—, —S(O)2N(R4)—, —OS(O)2—, or —S(O)2O—, wherein R4is H or C1-12hydrocarbyl.

In a specific embodiment, the polymer comprises a homopolymer of 5-(4-methoxy-3-(4-((2-methyladamantan-2-yl)oxy)-1-(2-((2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-dibenzothiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate, a homopolymer of 5-(4-methoxy-3-(4-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-1-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(2-(methacryloyloxy)acetoxy)ethanesulfonate, a homopolymer of 5-(4-methoxy-3-(2-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-2-oxo-1-(2-oxotetrahydrofuran-3-yl)ethyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate, a copolymer of 5-(4-(2-(2-methoxyethoxy)ethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate and 5-(4-methoxy-3-(4-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-1-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(2-(methacryloyloxy)acetoxy)ethanesulfonate, a copolymer 5-(4-(2-(2-methoxyethoxy)ethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate and 5-(4-methoxy-3-(2-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-2-oxo-1-(2-oxotetrahydrofuran-3-yl)ethyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate, or a combination thereof.

Another embodiment is a photoresist composition comprising the polymer and a solvent. Any of the variations described above in the context of the polymer apply as well to the photoresist composition comprising the polymer. Suitable solvents include anisole; esters including ethyl lactate, methyl 2-hydroxybutyrate (HBM), n-butyl acetate, 1-methoxy-2-propyl acetate (also referred to as propylene glycol methyl ether acetate, PGMEA), methoxyethyl propionate, ethoxyethyl propionate, and gamma-butyrolactone; alcohols including 1-methoxy-2-propanol (also referred to as propylene glycol methyl ether, PGME), and 1-ethoxy-2 propanol; ketones including cyclohexanone and 2-heptanone; and combinations thereof.

Another embodiment is a method of forming an electronic device, comprising: (a) applying a layer of the photoresist composition on a substrate; (b) pattern-wise exposing the photoresist composition layer to activating radiation; and (c) developing the exposed photoresist composition layer to provide a resist relief image.

FIG. 1is a synthetic scheme for the preparation of 5-(3,5-dimethyl-4-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)phenyl)-5H-dibenzo[b,d]thiophen-5-ium ((1S,4S)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl)methanesulfonate.

FIG. 2is a synthetic scheme for the preparation of 2-(2-methoxyethoxy)ethyl 4-tosylate.

FIG. 3is a synthetic scheme for the preparation of 2-(2-(2-methoxyethoxy)ethoxy)-1,3-dimethylbenzene.

FIG. 4is a synthetic scheme for the preparation of 5-(4-(2-(2-methoxyethoxy)ethoxy)-3,5-dimethylphenyl)-dibenzothiophen-5-ium iodide.

FIG. 5is a synthetic scheme for the preparation of 5-(4-(2-(2-methoxyethoxy)ethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate.

FIG. 6is a synthetic scheme for the preparation of 5-(4-methoxy-3-(4-((2-methyladamantan-2-yl)oxy)-1-(2-((2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-dibenzothiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate.

FIG. 7is a synthetic scheme for the preparation of 5-(4-methoxy-3-(4-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-1-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(2-(methacryloyloxy)acetoxy)ethanesulfonate.

FIG. 8is a synthetic scheme for the preparation of 5-(4-methoxy-3-(2-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-2-oxo-1-(2-oxotetrahydrofuran-3-yl)ethyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate.

In general polymer molecular weight were determined from13C NMR spectra obtained on a Varian 300 Megahertz NMR spectrometer operating with a relaxation delay of 2 seconds by integration of initiator end groups and one of the carbons of the PAG unit.

FIG. 9is a synthetic scheme for the preparation of a homopolymer of 5-(4-methoxy-3-(4-((2-methyladamantan-2-yl)oxy)-1-(2-((2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-dibenzothiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate.

5-(4-methoxy-3-(4-((2-methyladamantan-2-yl)oxy)-1-(2-((2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-dibenzothiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate (10.0 g, 10.2 mmol) was dissolved in ethyl lactate/gamma-butyrolactone (3/7 v/v, 15.0 g). The initiator 2,2′-azobis(2.4-dimethyl valeronitrile) (1.00 g) was dissolved in acetonitrile/tetrahydrofuran (2/1 v/v, 1.00 g). The monomer and initiator solutions were added drop-wise over 4 hours to a flask preheated to 80° C. followed by an initiator chase. The reaction mixture was stirred for 2 hours, cooled to room temperature, diluted with methanol (17 g) and precipitated into diisopropyl ether (800 g). The polymer was filtered and dried to afford the title compound (8.00 g, 80%, weight average molecular weight 3,972 daltons) as a white solid.

FIG. 10is a synthetic scheme for the preparation of a homopolymer of 5-(4-methoxy-3-(4-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-1-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(2-(methacryloyloxy)acetoxy)ethanesulfonate.

5-(4-methoxy-3-(4-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-1-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(2-(methacryloyloxy)acetoxy)ethanesulfonate (1.00 g, 0.953 mmol) was dissolved in ethyl lactate/gamma-butyrolactone (3/7 v/v, 1.50 g). 2,2′-Azobis(2.4-dimethyl valeronitrile) (0.150 g) was dissolved in acetonitrile/tetrahydrofuran (2/1 v/v, 0.150 g). The monomer and initiator solutions were added drop-wise to a flask preheated to 75° C. and stirred for 8 h. The reaction mixture was cooled to room temperature, diluted with acetone (0.900 g) and precipitated as a sticky solid from acetone/diisopropylether (1:1 25.0 g), decanted, redissolved in acetone (2.40 g) and methanol (0.500 g) and precipitated into diisopropyl ether (20× reaction volume). The polymer was filtered and dried to afford the title compound (0.550 g, 55%, weight average molecular weight 3,000 daltons) as a white solid.

FIG. 11is a synthetic scheme for the preparation of a homopolymer of 5-(4-methoxy-3-(2-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-2-oxo-1-(2-oxotetrahydrofuran-3-yl)ethyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate.

5-(4-methoxy-3-(2-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-2-oxo-1-(2-oxotetrahydrofuran-3-yl)ethyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate (15.0 g, 17.3 mmol) was dissolved in ethyl lactate/gamma-butyrolactone (3/7 v/v, 60.0 g). 2,2′-Azobis(2.4-dimethyl valeronitrile) (2.25 g) was dissolved in acetonitrile/tetrahydrofuran (2/1 v/v, 2.25 g). The monomer and initiator solutions were added drop-wise over 4 hours to a flask preheated to 90° C. The reaction mixture was cooled to room temperature, diluted with tetrahydrofuran (10× reaction volume) and acetone (5× reaction volume) and precipitated into diisopropyl ether (2000 g). The polymer was filtered and dried to afford the title compound (7.96 g, 53%, weight average molecular weight 3,476 daltons) as a white solid.

FIG. 12is a synthetic scheme for the preparation of a copolymer of 5-(4-(2-(2-methoxyethoxy)ethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate and 5-(4-methoxy-3-(4-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-1-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-1,4-dioxobutan-2-yl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(2-(methacryloyloxy)acetoxy)ethanesulfonate.

FIG. 13is a synthetic scheme for the preparation of a copolymer 5-(4-(2-(2-methoxyethoxy)ethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate and 5-(4-methoxy-3-(2-(2-(((1R,3S,5r,7r)-2-methyladamantan-2-yl)oxy)-2-oxoethoxy)-2-oxo-1-(2-oxotetrahydrofuran-3-yl)ethyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate.

Preparation of Tetrapolymer with Acid Generator Units

A heel solution was made by dissolving 2-phenylpropan-2-yl methacrylate (0.39 g), 2-oxotetrahydrofuran-3-yl methacrylate (0.33 g), 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl methacrylate (0.57 g) and 5-(4-(2-(1-ethylcyclopentyloxy)-2-oxoethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate (0.31 g) in 12.81 g ethyl lactate/gamma butyrolactone (7/3 v/v). Feed solution was prepared by dissolving 2-phenylpropan-2-yl methacrylate (185.54 g, 0.967 mol), 2-oxotetrahydrofuran-3-yl methacrylate (204.27 g, 1.26 mol), 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl methacrylate (127.98 g, 0.29 mol) and 5-(4-(2-(1-ethylcyclopentyloxy)-2-oxoethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate (81.5 g, 0.132 mol) in 606 g ethyl lactate:γ-butyrolactone (30/70 v/v). Initiator solution was prepared by dissolving 65.96 g initiator (2,2′-azobis(2.4-dimethyl valeronitrile)) in 66 g acetonitrile/tetrahydrofuran (2/1 v/v). The polymerization was carried out in a 2 L 3-neck round bottom flask fitted with a water condenser and a thermometer to monitor the reaction in the flask. The contents were stirred using an overhead stirrer. The reactor was charged with the heel solution and the contents were heated to 75° C. The feed solution and the initiator solution were fed into the reactor using syringe pump over a 4 hour time period. The contents were then stirred for additional 2 hours, whereby, the reaction was quenched using hydroquinone (2.0 g). The contents were cooled to room temperature and precipitated twice out of 10× (by weight) diisopropyl ether/methanol 95/5 (w/w). The polymer obtained was dried under vacuum after each precipitation step at 50° C. for 24 hours to yield 500 g polymer having a weight average molecular weight of 5,200 daltons, a dispersity of 1.5, and a monomer composition of the respective monomers of 36.0 mole percent, 47.5 mole percent, 11.0 mole percent, and 5.5 mole percent.

Preparation of Tetrapolymer with Acid Generator Units (PDBT-F2 Polymer Example)

The process of Example 14 was repeated, except that equimolar 5-phenyl-5H-dibenzo[b,d]thiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate was used in place of 5-(4-(2-(1-ethylcyclopentyloxy)-2-oxoethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate. The polymer obtained had a weight average molecular weight of 6,300 daltons, a dispersity of 1.4, and respective monomer contents of 36.5 mole percent, 47.5 mole percent, 12.0 mole percent, and 5 mole percent.

Preparation of Tetrapolymer with Acid Generator Units (TBPPDBTS-F2)

The process of Example 14 was repeated, except that equimolar 5-(4-(tert-butyl)phenyl)-5H-dibenzo[b,d]thiophen-5-ium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate was used in place of 5-(4-(2-(1-ethylcyclopentyloxy)-2-oxoethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate. The polymer obtained had a weight average molecular weight of 5,200 daltons, a dispersity of 1.6, and respective monomer contents of 34 mole percent, 51 mole percent, 9 mole percent, and 6 mole percent.

Preparation of Tetrapolymer with Acid Generator Units

The process of Example 14 was repeated, except that an equimolar amount of the monomer of Example 9 was used in place of 5-(4-(2-(1-ethylcyclopentyloxy)-2-oxoethoxy)-3,5-dimethylphenyl)-5H-dibenzo[b,d]thiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate. The polymer obtained had a weight average molecular weight of 5,200 daltons, a dispersity of 1.5, and respective monomer contents of 38 mole percent, 46 mole percent, 10 mole percent, and 6 mole percent.

Preparation of Tetrapolymer with Acid Generator Units

A heel solution was made by dissolving 2-phenylpropan-2-yl methacrylate (0.53 g), (1S,3R,8S)-5-oxo-4-oxatricyclo[4.3.1.13,8]undecan-1-yl methacrylate (0.44 g), 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl methacrylate (0.78 g) and phenyldibenzothiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate (0.42 g) in 20.0 g ethyl lactate/gamma butyrolactone (7/3 v/v). Feed solution was prepared by dissolving 2-phenylpropan-2-yl methacrylate (7.50 g), (1S,3R,8S)-5-oxo-4-oxatricyclo[4.3.1.13,8]undecan-1-yl methacrylate (12.23 g), 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl methacrylate (4.97 g) and phenyldibenzothiophenium 1,1-difluoro-2-(methacryloyloxy)ethanesulfonate (1.12 g) in 26.0 g ethyl lactate:γ-butyrolactone (3/7 v/v). Initiator solution was prepared by dissolving 2.59 g initiator (2,2′-azobis(2.4-dimethyl valeronitrile)) in 2.59 g acetonitrile/tetrahydrofuran (2/1 v/v). The polymerization was carried out in a 200 mL 3-neck round bottom flask fitted with a water condenser and a thermometer to monitor the reaction in the flask. The contents were stirred using an overhead stirrer. The reactor was charged with the heel solution and the contents were heated to 75° C. The feed solution and the initiator solution were fed into the reactor using syringe pump over a 4 hour time period. The contents were then stirred for additional 2 hours, whereby, the reaction was quenched using hydroquinone (0.200 g). The contents were cooled to room temperature and precipitated twice out of 10× (by weight) diisopropyl ether/methanol 95/5 (w/w). The polymer obtained was dried under vacuum after each precipitation step at 50° C. for 24 hours to yield 26 grams of polymer having a weight average molecular weight of 5,000 daltons, a dispersity of 1.5, and respective monomer contents of 36 mole percent, 47 mole percent, 12 mole percent, and 5 mole percent.

Preparation and Processing of a Photoresist Composition

Non-polymeric photoacid generators and photo-destroyable quenchers (collectively, “additives”) used in the preparation of photoresist compositions are summarized in Table 1. Photoresist compositions are summarized in Table 2. The Example 19 positive-tone photoresist composition was prepared by combining component 1, 5.33 g of a 10 weight percent solution of the polymer of Example 17 in ethyl lactate; component 2, 10.373 g of a 2 weight percent solution of the additive A-1 in ethyl lactate; component 3, 0.320 g of a 0.5 weight percent solution of tetrakis(2-hydroxypropyl)ethylenediamine in ethyl lactate; component 4, 0.356 g of a 2 weight percent solution of the additive A-2 in ethyl lactate; component 5, 0.107 g of a 0.5 weight percent solution of fluorinated surfactant (Omnova PF656) in ethyl lactate; component 6, 4.737 g of ethyl lactate; and component 7, 8.775 g of 2-hydroxyisobutyric acid methyl ester. The formulated resist was passed through a 0.01 micrometer (μm) polytetrafluoroethylene (PTFE) filter. The thus prepared resist was spin coated onto a silicon wafer, soft baked to remove carrier solvent and exposed through a photomask to EUV radiation. The imaged resist layer was then baked at 110° C. for 60 seconds and then developed with an aqueous alkaline composition.

For Table 2, below, components 1-7 correspond to the descriptions in Example 19. Component amounts, in brackets, are expressed in units of grams.

Critical Dimension Uniformity.

Critical dimension uniformity (CDU) is the calculated 3 Sigma (three standard deviations) for ten Fields of View (FOV) measuring 36 contact holes for each FOV, all taken at Best Exposure/Best Focus at 30 nm contact hole resolution with 1:1 half pitch. Each data point has been pre-normalized to a standard EUV photoresist which is run in each lithographic slot to eliminate variability and noise. The results, presented in Table 3, show that the lowest (best) CDU value is exhibited by the inventive Example 23 photoresist. In Table 3, the CDU of Example 23 is normalized to 1, and designated with “⋄”. Comparative examples which underperform relative to the example by 0-5% are designated with“●”; comparative examples which underperform relative to the example by 5%-15% are designated with “▪”; and comparative examples which underperform relative to the example by >15% are designated with “□”. In Table 3, “PolyPAG” refers to a polymer comprising 50 to 100 mole percent of photoacid-generating repeat units, “Polymer-bound-PAG” refers to a polymer comprising photoacid-generating repeat units in an amount less than 50 mole percent, and “free PAG” refers to a non-polymer-bound photoacid-generator.

Dose to Clear.

Extreme ultraviolet (EUV) dose to clear was measured as the dose at 5% remaining film thickness. Data was collected either on a Litho Tech Japan (LTJ) EVUES-9000 tool or on the Albany MET tool at the College of Nanoscale Science and Technology at the State University of New York, Albany. Processing conditions were a soft bake at 110° C. for 90 seconds, a post exposure bake for at 100° C. for 60 seconds, and development for 30 seconds at room temperature in 0.26N tetramethylammonium hydroxide developer.

Dose to clear results are summarized in Table 4. Dose to clear values for inventive Examples 23-26 are normalized to a value of 1.00 for Comparative Example 21. Values below 1.00 represent a desirable decrease in dose to clear energy. The results show that inventive photoresist compositions 23-26 exhibit substantially decreased dose to clear energies relative to the Example 21 comparison. The results are consistent with the hypothesis that a progression from polymer-bound-PAG to (polymer-bound-PAG+additive PAG) to polyPAG will result in an increased sensitivity due to PAG density and uniformity.

In Table 5, inventive Examples 27-29 are normalized to a value of 1.00 for Comparative Example 31. Values below 1.00 represent a desirable decrease in dose to clear energy. The results show that inventive photoresist compositions 27-29 exhibit decreased dose to clear energies relative to the Example 31 comparison. The results are again consistent with the hypothesis that a progression from polymer-bound-PAG to polyPAG will result in an increased sensitivity due to PAG density and uniformity.

EUV contrast slope was measured as the slope of the contrast curve between 95% and 5% film thickness during positive tone development. Data was collected either on a Litho Tech Japan (LTJ) EVUES-9000 tool or on the Albany MET tool at the College of Nanoscale Science and Technology at the State University of New York, Albany. Processing conditions were a soft bake at 110° C. for 90 seconds, a post-exposure bake for at 100° C. for 60 seconds, and development for 30 seconds at room temperature in 0.26N tetramethylammonium hydroxide developer. In Table 6 the contrast slope of Comparative Example 30 was normalized to 1.00, and designated with “⋄”. Inventive examples that outperform relative to the comparative example by 10%-20% are designated with “▪”; and inventive examples that outperform relative to the comparative example by >20% are designated with “□”. The results show that for the property of contrast slope, inventive Example 27 outperforms Comparative Example 30 by at least 10%, and inventive Examples 28 and 29 outperform Comparative Example 30 by at least 20%.

In Table 7, the contrast slope of Comparative Example 19 was normalized to 1, and designated with “⋄”. Inventive examples that outperform the comparative example by >20% are designated with “□”. The results show that for the property of contrast slope, inventive Example 23-26 outperform Comparative Example 21 by at least 20%. The results are consistent with the hypothesis that a progression from polymer-bound-PAG to polyPAG will result in greater (more negative) contrast slope.