# Patent

## Title
Photoresist system and method

## Abstract

A system and method for photoresists is provided. In an embodiment a photoresist is developed. Once developed, the photoresist is slimmed using either a direct slimming technique or an indirect slimming technique. In a direct slimming technique the slimming agent is either an alkaline solution or a polar solvent. In the indirect slimming technique a hydrophobic material is diffused into the photoresist to form a modified region and the modified region is then removed.

## Background
This application claims the benefit of U.S. Provisional Application No. 61/777,742, filed on Mar. 12, 2013, entitled “Photoresist System and Method”, which application is hereby incorporated herein by reference.


BACKGROUND
As consumer devices have gotten smaller and smaller in response to consumer demand, the individual components of these devices have necessarily decreased in size as well. Semiconductor devices, which make up a major component of devices such as mobile phones, computer tablets, and the like, have been pressured to become smaller and smaller, with a corresponding pressure on the individual devices (e.g., transistors, resistors, capacitors, etc.) within the semiconductor devices to also be reduced in size.
One enabling technology that is used in the manufacturing processes of semiconductor devices is the use of photolithographic materials. Such materials are applied to a surface and then exposed to an energy that has itself been patterned. Such an exposure modifies the chemical and physical properties of the exposed regions of the photolithographic material. This modification, along with the lack of modification in regions of the photolithographic material that were not exposed, can be exploited to remove one region without removing the other.
However, as the size of individual devices has decreased, process windows for photolithographic processing as become tighter and tighter. As such, advances in the field of photolithographic processing have been necessitated in order to keep up the ability to scale down the devices, and further improvements are needed in order to meet the desired design criteria such that the march towards smaller and smaller components may be maintained.



BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present embodiments, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a photoresist on a semiconductor substrate in accordance with an embodiment;
FIG. 2 illustrates an exposure of the photoresist in accordance with an embodiment;
FIGS. 3-4 illustrate a development of the photoresist in accordance with an embodiment;
FIGS. 5A-5B illustrate a slimming of the photoresist using a direct slimming process in accordance with an embodiment; and
FIGS. 6-8 illustrate a slimming of the photoresist using an indirect slimming process in accordance with an embodiment.



Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The making and using of the present embodiments are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the disclosed subject matter, and do not limit the scope of the different embodiments.
Embodiments will be described with respect to a specific context, namely a photoresist slimming process utilized in the manufacturing of semiconductor devices. Other embodiments may also be applied, however, to other slimming processes of other materials.
With reference now to FIG. 1, there is shown a semiconductor device 100 with a substrate 101, active devices 103 on the substrate 101, an interlayer dielectric (ILD) layer 105 over the active devices 103, metallization layers 107 over the ILD layer 105, a layer to be patterned 109 over the ILD layer 105, and a photoresist 111 over the layer to be patterned 109. The substrate 101 may comprise bulk silicon, doped or undoped, or an active layer of a silicon-on-insulator (SOI) substrate. Generally, an SOI substrate comprises a layer of a semiconductor material such as silicon, germanium, silicon germanium, SOI, silicon germanium on insulator (SGOI), or combinations thereof. Other substrates that may be used include multi-layered substrates, gradient substrates, or hybrid orientation substrates.
The active devices 103 are represented in FIG. 1 as a single transistor. However, as one of skill in the art will recognize, a wide variety of active devices such as capacitors, resistors, inductors and the like may be used to generate the desired structural and functional requirements of the design for the semiconductor device 100. The active devices 103 may be formed using any suitable methods either within or else on the surface of the substrate 101.
The ILD layer 105 may comprise a material such as boron phosphorous silicate glass (BPSG), although any suitable dielectrics may be used for either layer. The ILD layer 105 may be formed using a process such as PECVD, although other processes, such as LPCVD, may alternatively be used. The ILD layer 105 may be formed to a thickness of between about 100 Å and about 3,000 Å.
The metallization layers 107 are formed over the substrate 101, the active devices 103, and the ILD layer 105 and are designed to connect the various active devices 103 to form functional circuitry. While illustrated in FIG. 1 as a single layer, the metallization layers 107 are formed of alternating layers of dielectric and conductive material and may be formed through any suitable process (such as deposition, damascene, dual damascene, etc.). In an embodiment there may be four layers of metallization separated from the substrate 101 by the ILD layer 105, but the precise number of metallization layers 107 is dependent upon the design of the semiconductor device 100.
A layer to be patterned 109 or otherwise processed using the photoresist 111 is formed over the metallization layers 107. The layer to be patterned 109 may be an upper layer of the metallization layers 107 or else may be a dielectric layer (such as a passivation layer) formed over the metallization layers 107. In an embodiment in which the layer to be patterned 109 is a metallization layer, the layer to be patterned 109 may be formed of a conductive material using processes similar to the processes used for the metallization layers (e.g., damascene, dual damascene, deposition, etc.). Alternatively, if the layer to be patterned 109 is a dielectric layer the layer to be patterned 109 may be formed of a dielectric material using such processes as deposition, oxidation, or the like.
However, as one of ordinary skill in the art will recognize, while materials, processes, and other details are described in the embodiments, these details are merely intended to be illustrative of embodiments, and are not intended to be limiting in any fashion. Rather, any suitable layer, made of any suitable material, by any suitable process, and any suitable thickness, may alternatively be used. All such layers are fully intended to be included within the scope of the embodiments.
The photoresist 111 is applied to the layer to be patterned 109. In an embodiment the photoresist 111 includes a polymer resin along with one or more photoactive compounds (PACs) in a solvent. In an embodiment the polymer resin may comprise a hydrocarbon structure (such as a alicyclic hydrocarbon structure) that contains one or more groups that will decompose (e.g., acid labile groups) or otherwise react when mixed with acids, bases, or free radicals generated by the PACs (as further described below). In an embodiment the hydrocarbon structure comprises a repeating unit that forms a skeletal backbone of the polymer resin. This repeating unit may include acrylic esters, methacrylic esters, crotonic esters, vinyl esters, maleic diesters, fumaric diesters, itaconic diesters, (meth)acrylonitrile, (meth)acrylamides, styrenes, vinyl ethers, combinations of these, or the like.
Specific structures which may be utilized for the repeating unit of the hydrocarbon structure include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, acetoxyethyl acrylate, phenyl acrylate, 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-alkyl-2-adamantyl (meth)acrylate or dialkyl(1-adamantyl)methyl (meth)acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, acetoxyethyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-(2-methoxyethoxy)ethyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, 3-acetoxy-2-hydroxypropyl methacrylate, 3-chloroacetoxy-2-hydroxypropyl methacrylate, butyl crotonate, hexyl crotonate and the like. Examples of the vinyl esters include vinyl acetate, vinyl propionate, vinyl butylate, vinyl methoxyacetate, vinyl benzoate, dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, acrylamide, methyl acrylamide, ethyl acrylamide, propyl acrylamide, n-butyl acrylamide, tert-butyl acrylamide, cyclohexyl acrylamide, 2-methoxyethyl acrylamide, dimethyl acrylamide, diethyl acrylamide, phenyl acrylamide, benzyl acrylamide, methacrylamide, methyl methacrylamide, ethyl methacrylamide, propyl methacrylamide, n-butyl methacrylamide, tert-butyl methacrylamide, cyclohexyl methacrylamide, 2-methoxyethyl methacrylamide, dimethyl methacrylamide, diethyl methacrylamide, phenyl methacrylamide, benzyl methacrylamide, methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethyl vinyl ether and the like. Examples of the styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl methyl benzoate, α-methyl styrene, maleimide, vinylpyridine, vinylpyrrolidone, vinylcarbazole, combinations of these, or the like.
In an embodiment the repeating unit of the hydrocarbon structure may also have either a monocyclic or a polycyclic hydrocarbon structure substituted into it, or else the monocyclic or polycyclic hydrocarbon structure may be the repeating unit, in order to form an alicyclic hydrocarbon structure. Specific examples of monocyclic structures that may be used include bicycloalkane, tricycloalkane, tetracycloalkane, cyclopentane, cyclohexane, or the like. Specific examples of polycyclic structures that may be used include adamantine, norbornane, isobornane, tricyclodecane, tetracycododecane, or the like.
The group which will decompose, otherwise known as a leaving group or, in an embodiment in which the PAC is a photoacid generator, an acid labile group, is attached to the hydrocarbon structure so that, it will react with the acids/bases/free radicals generated by the PACs during exposure. In an embodiment the group which will decompose may be a carboxylic acid group, a fluorinated alcohol group, a phenolic alcohol group, a sulfonic group, a sulfonamide group, a sulfonylimido group, an (alkylsulfonyl) (alkylcarbonyl)methylene group, an (alkylsulfonyl)(alkyl-carbonyl)imido group, a bis(alkylcarbonyl)methylene gourp, a bis(alkylcarbonyl)imido group, a bis(alkylsylfonyl)methylene group, a bis(alkylsulfonyl)imido group, a tris(alkylcarbonyl methylene group, a tris(alkylsulfonyl)methylene group, combinations of these, or the like. Specific groups that may be utilized for the fluorinated alcohol group include fluorinated hydroxyalkyl groups, such as a hexafluoroisopropanol group. Specific groups that may be utilized for the carboxylic acid group include acrylic acid groups, methacrylic acid groups, or the like.
In an embodiment the polymer resin may also comprise other groups attached to the hydrocarbon structure that help to improve a variety of properties of the polymerizable resin. For example, inclusion of a lactone group to the hydrocarbon structure assists to reduce the amount of line edge roughness after the photoresist 111 has been developed, thereby helping to reduce the number of defects that occur during development. In an embodiment the lactone groups may include rings having five to seven members, although any suitable lactone structure may alternatively be used for the lactone group.
The polymer resin may also comprise groups that can assist in increasing the adhesiveness of the photoresist 111 to underlying structures (e.g., the layer to be patterned 109). In an embodiment polar groups may be used to help increase the adhesiveness, and polar groups that may be used in this embodiment include hydroxyl groups, cyano groups, or the like, although any suitable polar group may alternatively be utilized.
Optionally, the polymer resin may further comprise one or more alicyclic hydrocarbon structures that do not also contain a group which will decompose. In an embodiment the hydrocarbon structure that does not contain a group which will decompose may includes structures such as 1-adamantyl(meth)acrylate, tricyclodecanyl (meth)acrylate, cyclohexayl (meth)acrylate, combinations of these, or the like.
Additionally, the photoresist 111 also comprises one or more PACs. The PACs may be photoactive components such as photoacid generators, photobase generators, free-radical generators, or the like, and the PACs may be positive-acting or negative-acting. In an embodiment in which the PACs are a photoacid generator, the PACs may comprise halogenated triazines, onium salts, diazonium salts, aromatic diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonate, oxime sulfonate, disulfone, o-nitrobenzylsulfonate, sulfonated esters, halogenerated sulfonyloxy dicarboximides, diazodisulfones, α-cyanooxyamine-sulfonates, imidesulfonates, ketodiazosulfones, sulfonyldiazoesters, 1,2-di(arylsulfonyl)hydrazines, nitrobenzyl esters, and the s-triazine derivatives, suitable combinations of these, and the like.
Specific examples of photoacid generators that may be used include α.-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarbo-ximide (MDT), N-hydroxy-naphthalimide (DDSN), benzoin tosylate, t-butylphenyl-α-(p-toluenesulfonyloxy)-acetate and t-butyl-α-(p-toluenesulfonyloxy)-acetate, triarylsulfonium and diaryliodonium hexafluoroantimonates, hexafluoroarsenates, trifluoromethanesulfonates, iodonium perfluorooctanesulfonate, N-camphorsulfonyloxynaphthalimide, N-pentafluorophenylsulfonyloxynaphthalimide, ionic iodonium sulfonates such as diaryl iodonium (alkyl or aryl) sulfonate and bis-(di-t-butylphenyl)iodonium camphanylsulfonate, perfluoroalkanesulfonates such as perfluoropentanesulfonate, perfluorooctanesulfonate, perfluoromethanesulfonate, aryl (e.g., phenyl or benzyl) triflates such as triphenylsulfonium triflate or bis-(t-butylphenyl)iodonium triflate; pyrogallol derivatives (e.g., trimesylate of pyrogallol), trifluoromethanesulfonate esters of hydroxyimides, α,α′-bis-sulfonyl-diazomethanes, sulfonate esters of nitro-substituted benzyl alcohols, naphthoquinone-4-diazides, alkyl disulfones, and the like.
In an embodiment in which the PACs are a free-radical generator, the PACs may comprise n-phenylglycine, aromatic ketones such as benzophenone, N,N-tetramethyl-4,4′-diaminobenzophenone, N,N′-tetraethyl-4,4′-diaminobenzophenone, 4-methoxy-4′-dimethylaminobenzo-phenone, 3,3′-dimethyl-4-methoxybenzophenone, p,p′-bis(dimethylamino)benzo-phenone, p,p′-bis(diethylamino)-benzophenone, anthraquinone, 2-ethylanthraquinone, naphthaquinone and phenanthraquinone, benzoins such as benzoin, benzoinmethylether, benzomethylether, benzoinisopropylether, benzoin-n-butylether, benzoin-phenylether, methylbenzoin and ethybenzoin, benzyl derivatives such as dibenzyl, benzyldiphenyldisulfide and benzyldimethylketal, acridine derivatives such as 9-phenylacridine and 1,7-bis(9-acridinyl)heptane, thioxanthones such as 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone and 2-isopropylthioxanthone, acetophenones such as 1,1-dichloroacetophenone, p-t-butyldichloro-acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 2,2-dichloro-4-phenoxyacetophenone, 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di-(m-methoxyphenyl imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer, 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer and 2-(p-methylmercaptophenyl)-4,5-diphenylimidazole dimmer, suitable combinations of these, or the like.
In an embodiment in which the PACs are a photobase generator, the PACs may comprise quaternary ammonium dithiocarbamates, a aminoketones, oxime-urethane containing molecules such as dibenzophenoneoxime hexamethylene diurethan, ammonium tetraorganylborate salts, and N-(2-nitrobenzyloxycarbonyl)cyclic amines, suitable combinations of these, or the like. However, as one of ordinary skill in the art will recognize, the chemical compounds listed herein are merely intended as illustrated examples of the PACs and are not intended to limit the embodiments to only those PACs specifically described. Rather, any suitable PAC may alternatively be utilized, and all such PACs are fully intended to be included within the scope of the present embodiments.
The individual components of the photoresist 111 may be placed into a solvent in order to aid in the mixing and placement of the photoresist 111. To aid in the mixing and placement of the photoresist 111, the solvent is chosen at least in part based upon the materials chosen for the polymer resin as well as the PACs. In particular, the solvent is chosen such that the polymer resin and the PACs can be evenly dissolved into the solvent and dispensed upon the layer to be patterned 109.
In an embodiment the solvent may be an organic solvent, and may comprise any suitable solvent such as ketones, alcohols, polyalcohols, ethers, glycol ethers, cyclic ethers, aromatic hydrocarbons, esters, propionates, lactates, lactic esters, alkylene glycol monoalkyl ethers, alkyl lactates, alkyl alkoxypropionates, cyclic lactones, monoketone compounds that contain a ring, alkylene carbonates, alkyl alkoxyacetate, alkyl pyruvates, ethylene glycol alkyl ether acetates, diethylene glycols, propylene glycol alkyl ether acetates, alkylene glycol alkyl ether esters, alkylene glycol monoalkyl esters, or the like.
Specific examples of materials that may be used as the solvent for the photoresist 111 include, acetone, methanol, ethanol, toluene, xylene, 4-hydroxy-4-methyl-2-pentatone, tetrahydrofuran, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, ethylene glycol dimethyl ether, ethylene glycol methylethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol, glycol monoacetate, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethylmethyl ether, diethylene glycol monoethyl ether, diethylene monobutyl ether, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-2-methylbutanate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl acetate, butyl acetate, methyl lactate and ethyl lactate, propylene glycol, propylene glycol monoacetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monopropyl methyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol monomethyl ether propionate, propylene glycol monoethyl ether propionate, propylene glycol methyl ether acetate, proplylene glycol ethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propyl lactate, and butyl lactate, ethyl 3-ethoxypropionate, methyl 3-methoxypropionate, methyl 3-ethoxypropionate, and ethyl 3-methoxypropionate, β-propiolactone, β-butyrolactone, γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-octanoic lactone, α-hydroxy-γ-butyrolactone, 2-butanone, 3-methylbutanone, pinacolone, 2-pentanone, 3-pentanone, 4-methyl-2-pentanone, 2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone, 2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone, 3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone, 2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone, 3-decanone, 4-decanone, 5-hexene-2 -one, 3-pentene-2-one, cyclopentanone, 2-methylcyclopentanone, 3-methylcyclopentanone, 2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone, cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, 4-ethylcyclohexanone, 2,2-dimethylcyclohexanone, 2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone, 2-methylcycloheptanone, 3-methylcycloheptanone, pylene carbonate, vinylene carbonate, ethylene carbonate, and butylene carbonate, acetate-2-methoxyethyl, acetate-2-ethoxyethyl, acetate-2-(2-ethoxyethoxy)ethyl, acetate-3-methoxy-3-methylbutyl, acetate-1-methoxy-2-propyl, dipropylene glycol, monomethylether, monoethylether, monopropylether, monobutylehter, monophenylether, dipropylene glycol monoacetate, dioxane, etheyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl puruvate, ethyl puruvate, propyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, n-methylpyrrolidone (NMP), 2-methoxyethyl ether (diglyme), ethylene glycol monom-ethyl ether, propylene glycol monomethyl ether; methyl proponiate, ethyl proponiate and ethyl ethoxy proponiate, methylethyl ketone, cyclohexanone, 2-heptanone, carbon dioxide, cyclopentatone, cyclohexanone, ethyl 3-ethocypropionate, propylene glycol methyl ether acetate (PGMEA), methylene cellosolve, butyle acetate, and 2-ethoxyethanol, N-methylformamide, N,N-dimethylformamide, N-methylformanilide, N-methylacetamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, benzyl ethyl ether, dihexyl ether, acetonylacetone, isophorone, caproic acid, caprylic acid, 1-octanol, 1-nonanol, benzyl alcohol, benzyl acetate, ethyl benzoate, diethyl oxalate, diethyl maleate, γ-butyrolactone, ethylene carbonate, propylene carbonate, phenyl cellosolve acetate, or the like.
However, as one of ordinary skill in the art will recognize, the materials listed and described above as examples of materials that may be utilized for the solvent component of the photoresist 111 are merely illustrative and are not intended to limit the embodiments. Rather, any suitable material that may dissolve the polymer resin and the PACs may alternatively be included within the scope of the embodiments.
Additionally, while individual ones of the above described materials may be used as the solvent for the photoresist 111, in alternative embodiments more than one of the above described materials may be utilized. For example, the solvent may comprise a combination mixture of two or more of the materials described. All such combinations are fully intended to be included within the scope of the embodiments.
Optionally, a cross-linking agent may also be added to the photoresist 111. The cross-linking agent reacts with the polymer resin within the photoresist 111 after exposure, assisting in increasing the cross-linking density of the photoresist, which helps to improve the resist pattern and resistance to dry etching. In an embodiment the cross-linking agent may be an melamine based agent, a urea based agent, ethylene urea based agent, propylene urea based agent, glycoluril based agent, an aliphatic cyclic hydrocarbon having a hydroxyl group, a hydroxyalkyl group, or a combination of these, oxygen containing derivatives of the aliphatic cyclic hydrocarbon, glycoluril compounds, etherified amino resins, combinations of these, or the like.
Specific examples of materials that may be utilized as a cross-linking agent include melamine, acetoguanamine, benzoguanamine, urea, ethylene urea, or glycoluril with formaldehyde, glycoluril with a combination of formaldehyde and a lower alcohol, hexamethoxymethylmelamine, bismethoxymethylurea, bismethoxymethylbismethoxyethylene urea, tetramethoxymethylglycoluril, and tetrabutoxymethylglycoluril, mono-, di-, tri-, or tetra-hydroxymethylated glycoluril, mono-, di-, tri-, and/or tetra-methoxymethylated glycoluril, mono-, di-, tri-, and/or tetra-ethoxymethylated glycoluril, mono-, di-, tri-, and/or tetra-propoxymethylated glycoluril, and mono-, di-, tri-, and/or tetra-butoxymethylated glycoluril, 2,3-dihydroxy-5-hydroxymethylnorbornane, 2-hydroy-5,6-bis(hydroxymethyl)norbornane, cyclohexanedimethanol, 3,4,8(or 9)-trihydroxytricyclodecane, 2-methyl-2-adamantanol, 1,4-dioxane-2,3-diol and 1,3,5-trihydroxycyclohexane, tetramethoxymethyl glycoluril, methylpropyltetramethoxymethyl glycoluril, and methylphenyltetramethoxymethylglycoluril, 2,6-bis(hydroxymethyl)p-cresol, N-methoxymethyl- or N-butoxymethyl-melamine. Additionally, compounds obtained by reacting formaldehyde, or formaldehyde and lower alcohols with amino group-containing compounds, such as melamine, acetoguanamine, benzoguanamine, urea, ethylene urea and glycoluril, and substituting the hydrogen atoms of the amino group with hydroxymethyl group or lower alkoxymethyl group, examples being hexamethoxymethylmelamine, bismethoxymethyl urea, bismethoxymethylbismethoxyethylene urea, tetramethoxymethyl glycoluril and tetrabutoxymethyl glycoluril, copolymers of 3-chloro-2-hydroxypropyl methacrylate and methacrylic acid, copolymers of 3-chloro-2-hydroxypropyl methacrylate and cyclohexyl methacrylate and methacrylic acid, copolymers of 3-chloro-2-hydroxypropyl methacrylate and benzyl methacrylate and methacrylic acid, bisphenol A-di(3-chloro-2-hydroxypropyl)ether, poly(3-chloro-2-hydroxypro-pyl)ether of a phenol novolak resin, pentaerythritol tetra(3-chloro-2-hydroxypropyl)ether, trimethylolmethane tri(3-chloro-2-hydroxypropyl)ether phenol, bisphenol A-di(3-acetoxy-2-hydroxypropyl)ether, poly(3-acetoxy-2-hydroxypropyl)ethe-r of a phenol novolak resin, pentaerythritol tetra(3-acetoxy-2-hydroxyprop-yl)ether, pentaerythritol poly(3-chloroacetoxy-2-hydroxypropyl)ether, trimethylolmethane tri(3-acetoxy-2-hydroxypropyl)ether, combinations of these, or the like.
In addition to the polymer resins, the PACs, the solvents, and the cross-linking agents, the photoresist 111 may also include a number of other additives that will assist the photoresist 111 obtain the highest resolution. For example, the photoresist 111 may also include surfactants in order to help improve the ability of the photoresist 111 to coat the surface on which it is applied. In an embodiment the surfactants may include nonionic surfactants, polymers having fluorinated aliphatic groups, surfactants that contain at least one fluorine atom and/or at least one silicon atom, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters.
Specific examples of materials that may be used as surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenol ether, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitan tristearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, polyethylene glycol distearate, polyethylene glycol dilaurate, polyethylene glycol, polypropylene glycol, polyoxyethylenestearyl ether and polyoxyethylene cetyl ether; fluorine containing cationic surfactants, fluorine containing nonionic surfactants, fluorine containing anionic surfactants, cationic surfactants and anionic surfactants, polyethylene glycol, polypropylene glycol, polyoxyethylene cetyl ether, combinations of these, or the like.
Another additive that may be added to the photoresist 111 is a quencher, which may be utilized to inhibit diffusion of the generated acids/bases/free radicals within the photoresist, which helps the resist pattern configuration as well as to improve the stability of the photoresist 111 over time. In an embodiment the quencher is an amine such as a second lower aliphatic amine, a tertiary lower aliphatic amine, or the like. Specific examples of amines that may be used include trimethylamine, diethylamine, triethylamine, di-n-propylamine, tri-n-propylamine, tripentylamine, diethanolamine, and triethanolamine, alkanolamine, combinations of these, or the like.
Alternatively, an organic acid may be utilized as the quencher. Specific embodiments of organic acids that may be utilized include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid, phosphorous oxo acid and its derivatives such as phosphoric acid and derivatives thereof such as its esters, such as phosphoric acid, phosphoric acid di-n-butyl ester and phosphoric acid diphenyl ester; phosphonic acid and derivatives thereof such as its ester, such as phosphonic acid, phosphonic acid dimethyl ester, phosphonic acid di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, and phosphonic acid dibenzyl ester; and phosphinic acid and derivatives thereof such as its esters, including phosphinic acid and phenylphosphinic acid.
Another additive that may be added to the photoresist 111 is a stabilizer, which assists in preventing undesired diffusion of the acids generated during exposure of the photoresist 111. In an embodiment the stabilizer may include nitrogenous compounds such as aliphatic primary, secondary, and tertiary amines, cyclic amines such as piperidines, pyrrolidines, morpholines, aromatic heterocycles such as pyridines, pyrimidines, purines, imines such as diazabicycloundecene, guanidines, imides, amides, and others. Alternatively, ammonium salts may also be used for the stabilizer, including ammonium, primary, secondary, tertiary, and quaternary alkyl- and arylammonium salts of alkoxides including hydroxide, phenolates, carboxylates, aryl and alkyl sulfonates, sulfonamides, and others. Other cationic nitrogenous compounds including pyridinium salts and salts of other heterocyclic nitrogenous compounds with anions such as alkoxides including hydroxide, phenolates, carboxylates, aryl and alkyl sulfonates, sulfonamides, and the like may also be employed.
Yet another additive that may be added to the photoresist 111 may be a dissolution inhibitor in order to help control dissolution of the photoresist 111 during development. In an embodiment bile-salt esters may be utilized as the dissolution inhibitor. Specific examples of materials that may be utilized include cholic acid (IV), deoxycholic acid (V), lithocholic acid (VI), t-butyl deoxycholate (VII), t-butyl lithocholate (VIII), and t-butyl-3-α-acetyl lithocholate (IX).
Another additive that may be added to the photoresist 111 may be a plasticizer. Plasticizers may be used to reduce delamination and cracking between the photoresist 111 and underlying layers (e.g., the layer to be patterned 109) and may comprise monomeric, oligomeric, and polymeric plasticizers such as oligo-and polyethyleneglycol ethers, cycloaliphatic esters, and non-acid reactive steroidally-derived materials. Specific examples of materials that may be used for the plasticizer include dioctyl phthalate, didodecyl phthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, triacetyl glycerine and the like.
Yet another additive that may be added include a coloring agent, which helps observers examine the photoresist 111 and find any defects that may need to be remedied prior to further processing. In an embodiment the coloring agent may be either a triarylmethane dye or, alternatively, may be a fine particle organic pigment. Specific examples of materials that may be used as coloring agents include crystal violet, methyl violet, ethyl violet, oil blue #603, Victoria Pure Blue BOH, malachite green, diamond green, phthalocyanine pigments, azo pigments, carbon black, titanium oxide, brilliant green dye (C. I. 42020), Victoria Pure Blue FGA (Linebrow), Victoria BO (Linebrow) (C. I. 42595), Victoria Blue BO (C. I. 44045) rhodamine 6G (C. I. 45160), Benzophenone compounds such as 2,4-dihydroxybenzophenone and 2,2′,4,4′-tetrahydroxybenzophenone, salicylic acid compounds such as phenyl salicylate and 4-t-butylphenyl salicylate, phenylacrylate compounds such as ethyl-2-cyano-3,3-diphenylacrylate, and 2′-ethylhexyl-2-cyano-3,3-diphenylacrylate, benzotriazole compounds such as 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, and 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole, coumarin compounds such as 4-methyl-7-diethylamino-1-benzopyran-2-one, thioxanthone compounds such as diethylthioxanthone, stilbene compounds, naphthalic acid compounds, azo dyes, Phthalocyanine blue, phthalocyanine green, iodine green, Victoria blue, naphthalene black, Photopia methyl violet, bromphenol blue and bromcresol green, laser dyes such as Rhodamine G6, Coumarin 500, DCM (4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H pyran)), Kiton Red 620, Pyrromethene 580, or the like. Additionally, one or more coloring agents may be used in combination to provide the desired coloring.
Adhesion additives may also be added to the photoresist 111 in order to promote adhesion between the photoresist 111 and an underlying layer upon which the photoresist 111 has been applied (e.g., the layer to be patterned 109). In an embodiment the adhesion additives include a silane compound with at least one reactive substituent such as a carboxyl group, a methacryloyl group, an isocyanate group and/or an epoxy group. Specific examples of the adhesion components include trimethoxysilyl benzoic acid, γ-methacryloxypropyl trimethoxy silane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyl triethoxy silane, γ-glycidoxypropyl trimethoxy silane, β-(3,4-epoxycyclohexyl)ethyl trimethoxy silane, benzimidazoles and polybenzimidazoles, a lower hydroxyalkyl substituted pyridine derivative, a nitrogen heterocyclic compound, urea, thiourea, 8-oxyquinoline, 4-hydroxypteridine and derivatives, 1,10-phenanthroline and derivatives, 2,2′-bipyridine and derivatives, benzotriazoles; organophosphorus compounds, phenylenediamine compounds, 2-amino-1-phenylethanol, N-phenylethanolamine, N-ethyldiethanolamine, N-ethylethanolamine and derivatives, benzothiazole, and a benzothiazoleamine salt having a cyclohexyl ring and a morpholine ring, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyl trimethoxysilane, combinations of these, or the like.
Surface leveling agents may additionally be added to the photoresist 111 in order to assist a top surface of the photoresist 111 to be level so that impinging light will not be adversely modified by an unlevel surface. In an embodiment surface leveling agents may include fluoroaliphatic esters, hydroxyl terminated fluorinated polyethers, fluorinated ethylene glycol polymers, silicones, acrylic polymer leveling agents, combinations of these, or the like.
In an embodiment the polymer resin and the PACs, along with any desired additives or other agents, are added to the solvent for application. Once added, the mixture is then mixed in order to achieve an even composition throughout the photoresist 111 in order to ensure that there are no defects caused by an uneven mixing or non-constant composition of the photoresist 111. Once mixed together, the photoresist 111 may either be stored prior to its usage or else used immediately.
Once ready, the photoresist 111 may be utilized by initially applying the photoresist 111 onto the layer to be patterned 109. The photoresist 111 may be applied to the layer to be patterned 109 so that the photoresist 111 coats an upper exposed surface of the layer to be patterned 109, and may be applied using a process such as a spin-on coating process, a dip coating method, an air-knife coating method, a curtain coating method, a wire-bar coating method, a gravure coating method, a lamination method, an extrusion coating method, combinations of these, or the like. In an embodiment the photoresist 111 may be applied such that it has a thickness over the surface of the layer to be patterned 109 of between about 10 nm and about 300 nm, such as about 150 nm.
Once the photoresist 111 has been applied to the semiconductor substrate, a pre-bake of the photoresist 111 is performed in order to cure and dry the photoresist 111 prior to exposure to finish the application of the photoresist 111. The curing and drying of the photoresist 111 removes the solvent component while leaving behind the polymer resin, the PACs, cross-linking agents, and the other chosen additives. In an embodiment the pre-bake may be performed at a temperature suitable to evaporate the solvent, such as between about 40° C. and 150° C., although the precise temperature depends upon the materials chosen for the photoresist 111. The pre-bake is performed for a time sufficient to cure and dry the photoresist 111, such as between about 10 seconds to about 5 minutes, such as about 90 seconds.
FIG. 2 illustrates an exposure of the photoresist 111 to form an exposed region 201 and an unexposed region 203 within the photoresist 111. In an embodiment the exposure may be initiated by placing the semiconductor device 100 and the photoresist 111, once cured and dried, into an imaging device 200 for exposure. The imaging device 200 may comprise a support plate 205, an energy source 207, a patterned mask 209 between the support plate 205 and the energy source 207, and optics 213. In an embodiment the support plate 205 is a surface to which the semiconductor device 100 and the photoresist 111 may be placed or attached to and which provides support and control to the substrate 101 during exposure of the photoresist 111. Additionally, the support plate 205 may be movable along one or more axes, as well as providing any desired heating or cooling to the substrate 101 and photoresist 111 in order to prevent temperature gradients from affecting the exposure process.
In an embodiment the energy source 207 supplies energy 211 such as light to the photoresist 111 in order to induce a reaction of the PACs, which in turn reacts with the polymer resin to chemically alter those portions of the photoresist 111 to which the energy 211 impinges. In an embodiment the energy 211 may be electromagnetic radiation, such as g-rays (with a wavelength of about 436 nm), i-rays (with a wavelength of about 365 nm), ultraviolet radiation, far ultraviolet radiation, x-rays, electron beams, or the like. The energy source 207 may be a source of the electromagnetic radiation, and may be a KrF excimer laser light (with a wavelength of 248 nm), an ArF excimer laser light (with a wavelength of 193 nm), a F2 excimer laser light (with a wavelength of 157 nm), or the like, although any other suitable source of energy 211, such as mercury vapor lamps, xenon lamps, carbon arc lamps or the like, may alternatively be utilized.
The patterned mask 209 is located between the energy source 207 and the photoresist 111 in order to block portions of the energy 211 to form a patterned energy 215 prior to the energy 211 actually impinging upon the photoresist 111. In an embodiment the patterned mask 209 may comprise a series of layers (e.g., substrate, absorbance layers, anti-reflective coating layers, shielding layers, etc.) to reflect, absorb, or otherwise block portions of the energy 211 from reaching those portions of the photoresist 111 which are not desired to be illuminated. The desired pattern may be formed in the patterned mask 209 by forming openings through the patterned mask 209 in the desired shape of illumination.
Optics (represented in FIG. 2 by the trapezoid labeled 213) may be used to concentrate, expand, reflect, or otherwise control the energy 211 as it leaves the energy source 207, is patterned by the patterned mask 209, and is directed towards the photoresist 111. In an embodiment the optics 213 comprise one or more lenses, mirrors, filters, combinations of these, or the like to control the energy 211 along its path. Additionally, while the optics 213 are illustrated in FIG. 2 as being between the patterned mask 209 and the photoresist 111, elements of the optics 213 (e.g., individual lenses, mirrors, etc.) may also be located at any location between the energy source 207 (where the energy 211 is generated) and the photoresist 111.
In an embodiment the semiconductor device 100 with the photoresist 111 is placed on the support plate 205. Once the pattern has been aligned to the semiconductor device 100, the energy source 207 generates the desired energy 211 (e.g., light) which passes through the patterned mask 209 and the optics 213 on its way to the photoresist 111. The patterned energy 215 impinging upon portions of the photoresist 111 induces a reaction of the PACs within the photoresist 111. The chemical reaction products of the PACs' absorption of the patterned energy 215 (e.g., acids/bases/free radicals) then reacts with the polymer resin, chemically altering the photoresist 111 in those portions that were illuminated through the patterned mask 209.
In a specific example in which the patterned energy 215 is a 193 nm wavelength of light, the PAC is a photoacid generator, and the group to be decomposed is a carboxylic acid group on the hydrocarbon structure and a cross linking agent is used, the patterned energy 215 will impinge upon the photoacid generator and the photoacid generator will absorb the impinging patterned energy 215. This absorption initiates the photoacid generator to generate a proton (e.g., a H+ion) within the photoresist 111. When the proton impacts the carboxylic acid group on the hydrocarbon structure, the proton will react with the carboxylic acid group, chemically altering the carboxylic acid group and altering the properties of the polymer resin in general. The carboxylic acid group will then react with the cross-linking agent to cross-link with other polymer resins within the photoresist 111.
Optionally, the exposure of the photoresist 111 may occur using an immersion lithography technique. In such a technique an immersion medium (not individually illustrated in FIG. 2) may be placed between the imaging device 200 (and particularly between a final lens of the optics 213) and the photoresist 111. With this immersion medium in place, the photoresist 111 may be patterned with the patterned energy 215 passing through the immersion medium.
In this embodiment a protective layer (also not individually illustrated in FIG. 2) may be formed over the photoresist 111 in order to prevent the immersion medium from coming into direct contact with the photoresist 111 and leaching or otherwise adversely affecting the photoresist 111. In an embodiment the protective layer is insoluble within the immersion medium such that the immersion medium will not dissolve it and is immiscible in the photoresist 111 such that the protective layer will not adversely affect the photoresist 111. Additionally, the protective layer is transparent so that the patterned energy 215 may pass through the protective layer.
In an embodiment the protective layer comprises a protective layer resin within a protective layer solvent. The material used for the protective layer solvent is, at least in part, dependent upon the components chosen for the photoresist 111, as the protective layer solvent should not dissolve the materials of the photoresist 111 so as to avoid degradation of the photoresist 111 during application and use of the protective layer. In an embodiment the protective layer solvent includes alcohol solvents, fluorinated solvents, and hydrocarbon solvents.
Specific examples of materials that may be utilized for the protective layer solvent include methanol, ethanol, 1-propanol, isopropanol, n-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 3-methyl-1-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, n-hexanol, cyclohecanol, 1-hexanol, 1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, 2-methyl-2-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2,2,3,3,4,4-hexafluoro-1-butanol, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 2,2,3,3,4,4,5,5,6,6-decafluoro-1-hexanol, 2,2,3,3,4,4-hexafluoro-1,5-pentanediol, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-diol, 2-fluoroanisole, 2,3-difluoroanisole, perfluorohexane, perfluoroheptane, perfluoro-2-pentanone, perfluoro-2-butyltetrahydrofuran, perfluorotetrahydrofuran, perfluorotributylamine, perfluorotetrapentylamine, toluene, xylene and anisole, and aliphatic hydrocarbon solvents, such as n-heptane, n-nonane, n-octane, n-decane, 2-methylheptane, 3-methylheptane, 3,3-dimethylhexane, 2,3,4-trimethylpentane, combinations of these, or the like.
The protective layer resin may comprise a protective layer repeating unit. In an embodiment the protective layer repeating unit may be an acrylic resin with a repeating hydrocarbon structure having a carboxyl group, an alicyclic structure, an alkyl group having one to five carbon atoms, a phenol group, or a fluorine atom-containing group. Specific examples of the alicyclic structure include a cyclohexyl group, an adamantyl group, a norbornyl group, a isobornyl group, a tricyclodecyl group, a tetracyclododecyl group, and the like. Specific examples of the alkyl group include an n-butyl group, an isobutyl group, or the like. However, any suitable protective layer resin may alternatively be utilized.
The protective layer composition may also include additional additives to assist in such things as adhesion, surface leveling, coating, and the like. For example, the protective layer composition may further comprise a protective layer surfactant, although other additives may also be added, and all such additions are fully intended to be included within the scope of the embodiment. In an embodiment the protective layer surfactant may be an alkyl cationic surfactant, an amide-type quaternary cationic surfactant, an ester-type quaternary cationic surfactant, an amine oxide surfactant, a betaine surfactant, an alkoxylate surfactant, a fatty acid ester surfactant, an amide surfactant, an alcohol surfactant, an ethylenediamine surfactant, or a fluorine- and/or silicon-containing surfactant.
Specific examples of materials that may be used for the protective layer surfactant include polyoxyethylene alkyl ethers, such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether and polyoxyethylene oleyl ether; polyoxyethylene alkyl aryl ethers, such as polyoxyethylene octyl phenol ether and polyoxyethylene nonyl phenol ether; polyoxyethylene-polyooxypropylene block copolymers; sorbitan fatty acid esters, such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate and sorbitan tristearate; and polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate and polyoxyethylene sorbitan tristearate.
Prior to application of the protective layer onto the photoresist 111, the protective layer resin and desired additives are first added to the protective layer solvent to form a protective layer composition. The protective layer solvent is then mixed to ensure that the protective layer composition has a consistent concentration throughout the protective layer composition.
Once the protective layer composition is ready for application, the protective layer composition may be applied over the photoresist 111. In an embodiment the application may be performed using a process such as a spin-on coating process, a dip coating method, an air-knife coating method, a curtain coating method, a wire-bar coating method, a gravure coating method, a lamination method, an extrusion coating method, combinations of these, or the like. In an embodiment the photoresist 111 may be applied such that it has a thickness over the surface of the photoresist 111 of about 100 nm.
After the protective layer composition has been applied to the photoresist 111, a protective layer pre-bake may be performed in order to remove the protective layer solvent. In an embodiment the protective layer pre-bake may be performed at a temperature suitable to evaporate the protective layer solvent, such as between about 40° C. and 150° C., although the precise temperature depends upon the materials chosen for the protective layer composition. The protective layer pre-bake is performed for a time sufficient to cure and dry the protective layer composition, such as between about 10 seconds to about 5 minutes, such as about 90 seconds.
Once the protective layer has been placed over the photoresist 111, the semiconductor device 100 with the photoresist 111 and the protective layer are placed on the support plate 205, and the immersion medium may be placed between the protective layer and the optics 213. In an embodiment the immersion medium is a liquid having a refractive index greater than that of the surrounding atmosphere, such as having a refractive index greater than 1. Examples of the immersion medium may include water, oil, glycerine, glycerol, cycloalkanols, or the like, although any suitable medium may alternatively be utilized.
The placement of the immersion medium between the protective layer and the optics 213 may be done using, e.g., an air knife method, whereby fresh immersion medium is applied to a region between the protective layer and the optics 213 and controlled using pressurized gas directed towards the protective layer to form a barrier and keep the immersion medium from spreading. In this embodiment the immersion medium may be applied, used, and removed from the protective layer for recycling so that there is fresh immersion medium used for the actual imaging process.
However, the air knife method described above is not the only method by which the photoresist 111 may be exposed using an immersion method. Any other suitable method for imaging the photoresist 111 using an immersion medium, such as immersing the entire substrate 101 along with the photoresist 111 and the protective layer, using solid barriers instead of gaseous barriers, or using an immersion medium without a protective layer, may also be utilized. Any suitable method for exposing the photoresist 111 through the immersion medium may be used, and all such methods are fully intended to be included within the scope of the embodiments.
For example, in a particular embodiment in which the PAC is a photoacid generator and the group which will decompose is an acid labile group, the impinging patterned energy 215 will initiate the photoacid generators to generate, e.g., a acid in the form of a hydrogen proton (H+). The hydrogen atoms generated will then react with the acid labile group in the polymer resin, removing portions or all of the acid labile group, and modifying the chemical structure of the reacted polymer resin, leading to a change in the solubility of the polymer resin. In embodiments in which the cross-linking agent is used, the generated acids will also initiate the cross-linking agents to react with the polymer resins, cross-linking the polymer resins to each other and increasing the molecular weight of the resulting polymer.
After the photoresist 111 has been exposed to the patterned energy 215, a post-exposure baking may be used in order to assist in the generating, dispersing, and reacting of the acid/base/free radical generated from the impingement of the patterned energy 215 upon the PACs during the exposure. Such assistance helps to create or enhance chemical reactions which generate chemical differences between the exposed region 201 and the unexposed region 203 within the photoresist 111. These chemical differences also caused differences in the solubility between the exposed region 201 and the unexposed region 203. In an embodiment this post-exposure baking may occur at temperatures of between about 50° C. and about 160° C. for a period of between about 40 seconds and about 120 seconds.
FIG. 3 illustrates a development of the photoresist 111 with the use of a first developer 301 after the photoresist 111 has been exposed. In an embodiment in which a negative tone development is desired, an organic solvent or critical fluid may be utilized to remove those portions of the photoresist 111 which were not exposed to the patterned energy 215 and, as such, retain their original solubility. Specific examples of materials that may be utilized include hydrocarbon solvents, alcohol solvents, ether solvents, ester solvents, critical fluids, combinations of these, or the like. Specific examples of materials that can be used for the negative tone solvent include acetone, acetate, hexane, heptane, octane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, methanol, ethanol, propanol, butanol, critical carbon dioxide, diethyl ether, dipropyl ether, dibutyl ether, ethyl vinyl ether, dioxane, propylene oxide, tetrahydrofuran, cellosolve, methyl cellosolve, butyl cellosolve, methyl carbitol, diethylene glycol monoethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pyridine, formamide, N,N-dimethyl formamide, or the like.
In an embodiment in which immersion lithography is utilized to expose the photoresist 111 and a protective layer is utilized to protect the photoresist 111 from the immersion medium, the first developer 301 may be chosen to remove not only those portions of the photoresist 111 that are desired to be removed, but may also be chosen to remove the protective layer in the same development step. Alternatively, the protective layer may be removed in a separate process, such as by a separate solvent from the first developer 301 or even an etching process to remove the protective layer from the photoresist 111 prior to development.
The first developer 301 may be applied to the photoresist 111 using, e.g., a spin-on process. In an embodiment in which a spin-on process is utilized, the first developer 301 is applied to the photoresist 111 from above the photoresist 111 while the semiconductor device 100 (and the photoresist 111) is rotated. In an embodiment the first developer 301 may be supplied at a rate of between about 10 ml/min and about 2000 ml/min, such as about 500 ml/min, while the semiconductor device 100 is being rotated at a speed of between about 500 rpm and about 3500 rpm, such as about 1500 rpm. In an embodiment the first developer 301 may be at a temperature of between about 10° C. and about 80° C., such as about 50° C., and the development may continue for between about 1 minute to about 60 minutes, such as about 30 minutes.
However, while the spin-on process described herein is one suitable method for developing the photoresist 111 after exposure, it is intended to be illustrative and is not intended to limit the embodiment. Rather, any suitable method for development, including dip processes, puddle processes, and spray-on processes, may alternatively be used. All such development processes are fully intended to be included within the scope of the embodiments.
During development the first developer 301 will come into contact with the photoresist 111 and will absorb portions of the photoresist 111 that have retained their solubility through the exposure process (e.g., the unexposed region 203). This absorbtion will dissolve these sections of the photoresist 111, thereby separating the exposed region 201 from the unexposed region 203 of the photoresist 111. The exposed region 201 that changed its original solubility during the exposure process are insoluble in the first developer 301 (e.g., the negative tone developer) and are not absorbed, thereby remaining in a solid state during the development process while the non-exposed region 203 are dissolved.
FIG. 4 illustrates a removal of the first developer 301 from the photoresist 111 after the photoresist 111 has been developed with the first developer 301. In an embodiment the first developer 301 may be removed using, e.g., a spin-dry process, although any suitable removal technique may alternatively be utilized. Once the first developer 301 has been removed, the photoresist 111 may have an initial first width W1 of between about 20 nm and about 1000 nm, such as about 50 nm, and may also have an initial first height H1 of between about 20 nm and about 1000 nm, such as about 100 nm.
FIG. 5A illustrates a slimming process that may be utilized to reduce the width and height of the photoresist 111 from the first W1 and the first height H1. In an embodiment the slimming process may be a direct slimming process using either chemical methods or physical methods to directly remove portions of the photoresist 111 by applying a slimming agent 501 to the photoresist 111 after the photoresist 111 has been developed. In an embodiment the slimming agent 501 acts directly on the photoresist 111 (using either chemical means or physical means) to remove exterior portions of the photoresist 111, thereby reducing the dimensions of the photoresist 111.
In an embodiment in which a direct slimming process using a chemical reaction method is desired, the slimming agent 501 is a chemically reactive agent that is used to react with the material of the photoresist 111 and remove or etch the exterior surfaces of the photoresist 111. As one example, the chemically reactive agent may be an alkaline solution that comprises water and a base compound. In an embodiment the base compound may be an organic base, such as tetramethylammonium hydroxide (TMAH), tetrabutylammonium hydroxide (TBAH), trimethylamine, ammonia, guanidinium, combinations of these, or the like. Alternatively, the base compound may be an inorganic base, such as sodium hydroxide (NaOH), calcium hydroxide (CaOH2), combinations of these, or the like.
However, as one of ordinary skill in the art will recognize, the organic bases and inorganic bases described and listed above are intended to be illustrative only, and are not intended to be limiting upon the embodiments. Rather, any suitable alkaline materials that may be mixed in solution or else applied directly to the photoresist 111 may alternatively be utilized. All such materials are fully intended to be included within the scope of the embodiments.
The base compound may be placed into an aqueous solution for application to the photoresist 111. While the precise method of mixing is dependent at least in part upon the materials chosen for the base compound, in an embodiment in which the base compound is a liquid, the base compound may be mixed with the water to form the alkaline solution. Alternatively, if the base compound is a gaseous compound, the base compound may be dissolved into the water by, e.g., bubbling the base compound through the water.
In an embodiment the slimming agent 501 may be applied to the photoresist 111 using, e.g., a spin-on process, although any other suitable processes, such as dip processes, puddle processes, or spray-on processes, may alternatively be utilized. If a spin-on process is utilized, the slimming agent 501 may be applied to the photoresist 111 at a rate of between about 10 ml/min and about 1500 ml/min, such as about 300 ml/min, while the semiconductor device 100 and the photoresist 111 are rotated at a speed of between about 0 rpm and about 2000 rpm, such as about 1000 rpm. The slimming agent 501 may be applied at a temperature of between about 15° C. and about 100° C., such as about 25° C.
During the direct slimming process, the slimming agent 501 is applied to the photoresist 111. In an embodiment the photoresist 111 will at this point comprise groups which will react with the slimming agent, such as carboxylic groups. Because the slimming agent 501 is an alkaline solution, the groups on the photoresist (e.g., the carboxylic acid) will react with the slimming agent 501, thereby removing the exterior regions of the photoresist 111. Once an exterior region of the photoresist 111 has been reacted and removed into the slimming agent 501, the slimming agent 501 will then be in contact with a new surface of the photoresist 111, which is then reacted and removed in a similar fashion. In such a manner, the slimming agent 501 will react with and remove the photoresist 111 from the outer surfaces to slowly reduce the width and the height of the photoresist 111, as represented in FIG. 5A by the arrows labeled 503.
The rate of reaction between the slimming agent 501 and the photoresist 111 (and, thus, the rate of slimming of the photoresist 111) may be controlled by controlling, among other things, the pH of the slimming agent 501, which may have a pH range of greater than about 7 and less than about 10, although any other suitable pH may alternatively be utilized. For example, in an embodiment the greater the pH of the slimming agent 501, the larger the rate of removal of the photoresist 111. Similarly, the lower the pH of the slimming agent 501 (while still remaining alkaline), the slower the rate of removal. As such, the rate of removal of the photoresist 111 may be controlled by controlling the pH of the slimming agent 501.
In an embodiment the pH of the slimming agent 501 can be controlled can controlling the relative concentration of the base compound within the aqueous solution of the slimming agent 501. In an embodiment in which the base compound is ammonia and a pH of 7 ̃10 is desired, the slimming agent 501 may, e.g., have a concentration of about 0.001 wt % ̃40 wt %. However, the pH may be adjusted either up or down depending upon the desired rate of reaction.
Additionally, to further aid in the control of the rate of removal, a slimming surfactant may be added to the slimming agent 501 in order to assist the slimming agent 501 in coating the photoresist 111. By assisting the slimming agent 501 to coat the photoresist 111, the slimming surfactant aids in increasing the surface area of contact and, as such, aids in increasing the surface area of reaction. In an embodiment the slimming surfactant may be an organic solvent, such as acetone or acetate, and may have a concentration of between about 0.001 wt % and about 80 wt %, such as about 30 wt %, although any other suitable surfactant may alternatively be utilized.
An organic solvent may also be added to the slimming agent 501 in order to assist in the control of the rate of the chemical reaction between the slimming agent 501 and the photoresist 111 and, thus, assist in the rate of slimming of the photoresist 111. The organic solvent may be added in order to dilute the concentration of the base compound, thereby lowering the rate of reaction between the slimming agent 501 and the photoresist 111 by lowering the concentration of one of the reactants (e.g., the base compound). In an embodiment the organic solvent may be a solvent such as acetone, acetate, combinations of these, or the like, and may have a concentration within the slimming agent 501 of between about 0.001 wt % and about 80 wt %, such as about 30 wt %.
Alternatively, in another embodiment of the direct slimming process in which a chemical reaction is not desired, a physical absorption method may be utilized to remove exterior surfaces of the photoresist 111 and slim the photoresist 111. In this embodiment the slimming agent 501 may not be an alkaline solution (as described above and which chemically reacts with the photoresist 111) but is, rather, a polar solvent. The polar solvent may be an organic solvent similar to the first developer 301 (which was a negative tone developer) but has a polarity that is greater than the first developer 301 used to develop the photoresist 111. In a particular embodiment the polar solvent may be isopropyl alcohol (IPA), N-methyl-2-pyrrolidone (NMP), gamma-butyrolactone (GBL), or the like.
Additionally, in addition to using a single solvent as the polar solvent, a hybrid solvent may be utilized. In this embodiment two or more polar solvents may be mixed and applied to the photoresist 111 in order to start the slimming process. In this embodiment at least one of the polar solvents has a polarity that is greater than the polarity of the first developer 301.
In this embodiment in which the slimming agent 501 is slimming the photoresist 111 through physical methods instead of chemical methods, the polar solvent is applied to the photoresist 111 using, e.g., a spin-on method, although any other suitable method may alternatively be utilized. If a spin-on process is utilized, the slimming agent 501 in this embodiment may be applied to the photoresist 111 at a rate of between about 10 ml/min and about 1500 ml/min, such as about 300 ml/min, while the semiconductor device 100 and the photoresist 111 are rotated at a speed of between about 0 rpm and about 3500 rpm, such as about 500 rpm. The slimming agent 501 may be applied at a temperature of between about 15° C. and about 100° C., such as about 25° C.
Once in contact with the photoresist 111, the polar solvent will begin to absorb the exterior surfaces of the photoresist 111 into which the polar solvent comes into contact in a similar fashion as the first developer 301 dissolved the unexposed region 203 of the photoresist 111 (as described above with respect to FIG. 3). However, while the first developer 301 was chosen and used because the exposed region 201 of the photoresist 111 were insoluble or at least partially insoluble to the first developer 301, the polar solvent has a higher polarity than the first developer 301 that was used. Accordingly, the photoresist 111 may be semi-soluble to the polar solvent, and the polar solvent may absorb those portions of the photoresist 111 that were insoluble to the first developer 301. As such, the polar solvent will absorb and dissolve the exposed surfaces of the photoresist 111, slimming the photoresist 111 in the process.
FIG. 5B illustrates a result of the direct slimming processes after the slimming agent 501 has been used to slim the photoresist 111 and has been removed using, e.g., a spin-dry process. In this embodiment the photoresist 111 has been slimmed to have smaller dimensions than before the slimming process. For example, the photoresist 111 may have a second width W2 smaller than the first width W1, such as a second width W2 of between about 10 nm and about 100 nm, such as about 30 nm. Additionally, the photoresist 111 may have a second height H2 smaller than the first height H1, such as having a second height H2 of between about 10 nm and about 300 nm, such as about 20 nm.
By using a slimming process, the dimensions of the photoresist 111 are not limited to the dimensions utilized in the exposure of the photoresist 111. Rather, the photoresist 111 may be exposed with dimensions larger than the desired dimensions and, after development, the dimensions of the photoresist 111 may be modified. As such, this provides more flexibility in the process of photolithography, and even allows a reduction in dimensions beyond the limitations of the photolithography process, allowing for smaller devices to be crafted.
Once the slimming agent 501 has been utilized to slim the photoresist 111, the slimming agent 501 may be removed from the photoresist 111. Once the slimming agent 501 has been removed, the photoresist 111 may be dried using a drying process such as a spin-dry, in which the substrate 101 and the photoresist 111 are spun at high speeds to remove any excess liquids such as the slimming agent 501 from the surface of the photoresist 111.
FIGS. 6-8 illustrate an alternative, indirect slimming process that may be utilized to slim the photoresist 111 with greater control than the direct slimmin processes described above with respect to FIGS. 5A-5B. In this embodiment the processes prior to FIG. 6 may be similar to the processes described above with respect to FIGS. 1-4. However, in this indirect slimming process, a two step process is utilized to slim the photoresist 111. An initial diffusion step diffuses a reactive compound 601 into the photoresist 111, wherein the reactive compound 601 reacts with the material of the photoresist 111 and modifies the photoresist's 111 solubility but does not remove the photoresist 111 by itself. Once the reactive compound 601 has diffused to a desired depth and reacted with the material of the photoresist 111, a second removal process is performed in which the reacted material of the photoresist 111 is removed.
FIG. 6 illustrates an application of the reactive compound 601 to the photoresist 111. In an embodiment the reactive compound 601 may be a hydrophobic material such as an organic solution comprising a slimming organic solvent and an organic compound with hydrophobicibity, such as an alcohol, an amine, or carboxylic acid. In an embodiment the slimming organic solvent may be any solvent into which the organic compound may be placed and handled so that the organic compound may be placed in contact with the photoresist 111. As such, the slimming organic solvent may be similar to the organic solvent described above with respect to the photoresist 111, although any other suitable organic solvent may alternatively be used.
The organic compound may have the following structures:




where R1-R5 may be an alkyl group with hydrogen attached to the carbons and each group may have a carbon number between 2 and 20 with straight, branched or cyclic structures that are singly, doubly, or triply bonded. Each of the alkyl groups may also contain a hetero atom, such as containing nitrogen, oxygen, or fluorine, or may also contain a nitro- or sulfonic-group.

The organic compound may be placed into the slimming organic solvent to form the reactive compound so that it may be applied to the photoresist 111. Once the components are in solution, the reactive compound 601 may be applied to the photoresist 111 using, e.g., a spin-on process, although any other suitable process, such as a dip process or a spray-on process, may alternatively be utilized. If a spin-on process is utilized, the reactive compound 601 may be applied to the photoresist 111 at a rate of between about 10 ml/min and about 1500 ml/min, such as about 300 ml/min, while the semiconductor device 100 and photoresist 111 are rotated at a speed of between about 0 rpm and about 3500 rpm, such as about 500 rpm.
When the reactive compound 601 is applied to the photoresist 111, the organic compound will react with the photoresist 111 wherever the reactive compound 601 comes into contact with the photoresist 111. In an embodiment the reactive compound 601 will react with the groups present on the hydrocarbon structure of the photoresist 111, modifying the groups on the hydrocarbon structure and causing the hydrophilicity of the photoresist 111 to be reduced.
Also, in addition to merely reacting with the molecules on the surface of the photoresist 111, the reactive compound 601 will diffuse into the photoresist 111, where it will react with molecules located within the photoresist 111 as well as the molecules on the surface of the photoresist 111. This diffusion will create a modified region 603 wherein the photoresist 111 through which the reactive compound 601 has diffused has reacted with the reactive compound 601 and been modified so that the photoresist 111 has had its hydrophilicity reduced.
In an embodiment the diffusion of the reactive compound 601 into the photoresist 111 can be well controlled, allowing for a first distance D1 of diffusion to be easily controlled. In an embodiment the diffusion can be controlled by controlling the temperature at which the diffusion occurs and also controlling the amount of time that the reactive compound 601 is allowed to diffuse. As a particular example, in an embodiment in which alcohol is utilized as the reactive compound 601 and methacrylate is utilized as the photoresist 111, the reactive compound 601 may be applied to the photoresist 111 at a temperature of between about 15° C. and about 100° C., such as about 25° C. With this temperature, the reactive compound 601 is allowed to diffuse into the photoresist 111 for a time period of between about 5 sec and about 300 sec, such as about 60 sec. This allows for a diffusion into the photoresist 111 of the first distance D1 between about 3 nm and about 50 nm, such as about 10 nm.
However, as one of ordinary skill in the art will recognize, while the temperature and time of the diffusion process are described above as variables that may be utilized to control the rate of diffusion, these variables are only intended to be illustrative and are not intended to be limiting upon the embodiments. Rather, any suitable method of controlling the rate of diffusion of the reactive compound 601, such as controlling the concentration of the organic compound within the reactive compound 601, may alternatively be utilized. Any suitable method of control may be used, and all such methods are fully intended to be included within the scope of the embodiments.
By being able to control the diffusion of the reactive compound 601 through the photoresist 111, the diffusion may be stopped or significantly reduced when desired through such methods as removing the reactive compound 601 from the photoresist 111 or lowering the temperature of the diffusion process. As such, the indirect slimming process can be perceived as a static method of narrowing the photoresist 111. This static method is in distinction from the dynamic method of narrowing the photoresist 111 that was described in the direct slimming processes above in FIGS. 5A-5B.
FIG. 7 illustrates the second step of the indirect slimming process in which the reactive compound 601 is removed and a second developer 701 is applied to the photoresist 111 to remove the modified region 603 of the photoresist 111. In an embodiment the second developer 701 may be similar to the first developer 301, and may be the same negative tone developer used to develop the photoresist 111. However, in other embodiments the second developer 701 may be a different negative tone developer than was used to develop the photoresist 111.
The second developer 701 may be applied to the photoresist 111 using, e.g., a spin-on process. In this process the second developer 701 is applied to the photoresist 111 from above the photoresist 111 while the semiconductor device 100 (and the photoresist 111) is rotated. In an embodiment the second developer 701 may be supplied at a rate of between about 10 ml/min and about 1500 ml/min, such as about 500 ml/min, while the semiconductor device 100 is being rotated at a speed of between about 10 rpm and about 3500 rpm, such as about 500 rpm. In an embodiment the second developer 701 may be at a temperature of between about 10° C. and about 80° C., such as about 50° C., and the development may continue for between about 10 sec to about 600 sec, such as about 180 sec.
Because the photoresist 111 in the modified region 603 has had its hydrophilicity modified, when the second developer 701 comes into contact with the modified region 603, the second developer 701 will absorb the photoresist 111 within the modified region 603. However, because the reactive compound 601 has not diffused throughout the photoresist 111, the second developer 701 will not absorb or remove the photoresist 111 outside of the modified region 603. As such, the photoresist 111 can be narrowed as desired by controlling how far the reactive compound 601 diffuses into the photoresist 111 to form the modified region 603.
Once the second developer 701 has been utilized to remove the modified region 603, the second developer 701 may be removed from the photoresist 111. Once the second developer 701 has been removed, the photoresist 111 may be dried using a drying process such as a spin-dry, in which the substrate 101 and the photoresist 111 are spun at high speeds to remove any excess liquids such as the second developer 701 from the surface of the photoresist 111.
FIG. 8 illustrates a result of the indirect slimming process in which the photoresist 111 has been slimmed to have smaller dimensions than before the indirect slimming process. For example, the photoresist 111 may have a third width W3 smaller than the first width W1, such as a third width W3 of between about 10 nm and about 100 nm, such as about 30 nm. Additionally, the photoresist 111 may have a third height H3 smaller than the first height H1, such as having a third height H3 of between about 10 nm and about 200 nm, such as about 20 nm.
After the photoresist 111 has been slimmed by the slimming agent through either the direct slimming process or the indirect slimming process, additional processing may be performed on the layer to be patterned 109 while the photoresist 111 is in place. As one example, a reactive ion etch or other etching process may be utilized, to transfer the pattern of the photoresist 111 to the underlying layer to be patterned 109. Alternatively, in an embodiment in which the layer to be patterned 109 is a seed layer, the layer to be patterned 109 may be plated in order to form, e.g., a copper pillar, or other conductive structure in the opening of the photoresist 111. Any suitable processing, whether additive or subtractive, that may be performed while the photoresist 111 is in place may be performed, and all such additional processing are fully intended to be included within the scope of the embodiments.
By utilizing the slimming agents 501 to reduce the dimensions of the photoresist 111, issues related to negative tone exposure and processing may be reduce or eliminated. For example, as negative tone exposure and development have trouble defining photoresist lines and photoresist islands in dimensions <50 nm, the photoresist lines and photoresist islands may be exposed and developed at a desired dimension (e.g., 50 nm) and then the photoresist lines and photoresist islands may be slimmed in order to meet the desired specifications.
In accordance with an embodiment, a method for manufacturing a semiconductor device developing a photoresist on a substrate is provided. A dimension of the photoresist is reduced after the developing the photoresist.
In accordance with another embodiment, a method of manufacturing a semiconductor device comprising developing a photoresist on a substrate with a negative tone developer is provided. A slimming agent is applied to the photoresist after the developing the photoresist.
In accordance with yet another embodiment, a method of manufacturing a semiconductor device comprising applying a photoresist to a substrate and exposing the photoresist to an energy is provided. The photoresist is developed with a negative tone developer to form a patterned photoresist with a first width parallel to a major surface of the substrate, and the negative tone developer is removed. The first width is reduced to a second width after the removing the negative tone developer without removing the entire patterned photoresist.
Although the present embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many different processes may be utilized to form, apply, and develop the photoresist, and many different processes may be utilized to form, apply, and remove the slimming agents.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

## Claims

1. A method for manufacturing a semiconductor device, the method comprising:
developing a photoresist on a substrate; and
reducing a dimension of the photoresist with a liquid chemical after the developing the photoresist by applying an alkaline slimming agent that directly dissolves a portion of the photoresist.

2. The method of claim 1, wherein the alkaline slimming agent is a chemically reactive slimming agent.

3. The method of claim 1, wherein the alkaline slimming agent is tetramethylammonium hydroxide.

4. The method of claim 1, further comprising controlling the rate of removal by controlling the pH of the alkaline slimming agent.

5. The method of claim 4, wherein the controlling the pH of the alkaline slimming agent further comprises controlling the concentration of a base compound within the alkaline slimming agent.

6. The method of claim 1, wherein the alkaline slimming agent further comprises a surfactant.

7. A method of manufacturing a semiconductor device, the method comprising:
developing a photoresist on a substrate with a negative tone developer; and
applying a liquid slimming agent to the photoresist after the developing the photoresist, wherein the liquid slimming agent directly dissolves a portion of the photoresist.

8. The method of claim 7, wherein the liquid slimming agent is a chemically reactive compound.

9. The method of claim 8, wherein the chemically reactive compound is an alkaline solution.

10. The method of claim 7, wherein the negative tone developer has a first polarity and the slimming agent has a second polarity larger than the first polarity.

11. The method of claim 7, wherein the slimming agent comprises an organic compound.

12. The method of claim 11, wherein the organic compound comprises an alcohol or an amine.

13. The method of claim 7, wherein the slimming agent modifies groups on the photoresist to cause the hydrophilicity of the photoresist to be reduced.

14. The method of claim 7, wherein the liquid slimming agent comprises:
a first polar solvent; and
a second polar solvent different from the first polar solvent.

15. The method of claim 14, wherein the negative tone developer has a first polarity and the first polar solvent has a second polarity larger than the first polarity.

16. The method of claim 7, wherein the liquid slimming agent further comprises a surfactant.

17. A method of manufacturing a semiconductor device, the method comprising:
applying a photoresist to a substrate;
exposing the photoresist to an energy;
developing the photoresist with a negative tone developer to form a patterned photoresist with a first width parallel to a major surface of the substrate;
removing the negative tone developer;
reducing the first width to a second width after the removing the negative tone developer without removing the entire patterned photoresist, wherein the reducing the first width is performed by applying a liquid slimming agent to the patterned photoresist and allowing the liquid slimming agent to diffuse into the patterned photoresist and react with a portion of the patterned photoresist to form a modified region, the modified region having a lower hydrophilicity than a remainder of the patterned photoresist; and
removing the modified region that has reacted with the liquid slimming agent without removing the remainder of the patterned photoresist.

18. The method of claim 17, wherein the slimming agent comprises an organic compound.

19. The method of claim 18, wherein the organic compound comprises carboxylic acid.