Method for forming semiconductor device

Abstract

To provide a method for forming a semiconductor device.SOLUTION: Provided is a method that includes the steps of: (a) providing a semiconductor substrate including a metal layer; (b) forming an organic underlayer on the metal layer from an organic underlayer coating composition comprising a crosslinkable compound and a solvent; (c) crosslinking the organic underlayer; (d) patterning the cured organic underlayer to expose regions of the metal layer that are not covered by the organic underlayer; (e) applying an overcoat coating composition onto the substrate including the patterned organic underlayer, the overcoat coating composition comprising a crosslinkable compound capable of crosslinking with the patterned organic underlayer, and an organic solvent; (f) curing the overcoat coating composition to induce crosslinking between the compound and the patterned organic underlayer; (g) removing the uncrosslinked portion of the overcoat from the substrate using an organic solution; and (h) etching the metal layer using the patterned organic underlayer and the crosslinked portion of the overcoat as an etching mask.SELECTED DRAWING: Figure 1G

Description

Technical Field

[0001] The present invention generally relates to the manufacture of electronic devices. More specifically, the present invention relates to a method of forming a semiconductor device that includes patterning a metal layer by wet etching. This method is particularly used to form fine lithography patterns in the semiconductor manufacturing industry.

Background Art

[0002] A photoresist is a photosensitive film used to transfer an image onto a substrate. A coating layer of photoresist is formed on the substrate, and then the photoresist layer is exposed by an activating radiation source directly or, more commonly, through a patterned photomask. After exposure, the photoresist is developed to provide a relief image that enables selective processing of the substrate.

[0003] The reflection of the activating radiation used to expose the photoresist often limits the resolution of the image patterned in the photoresist layer. Due to the reflection of radiation from the substrate / photoresist interface, spatial variations in the radiation intensity occur in the photoresist, and the line width of the photoresist may become non-uniform during development. Also, the radiation may scatter from the substrate / photoresist interface into regions of the photoresist where exposure is not intended, which also results in line width variations. Such reflections and light scattering can be particularly problematic when the layer to be patterned on the substrate is reflective, as is common when patterning metal layers.

[0004] A known approach for reducing the problem of radiation reflected during exposure of the photoresist layer is the use of a radiation-absorbing organic underlayer inserted between the substrate surface and the photoresist coating layer (see, for example, Patent Document 1). In order to increase the integration density of semiconductor devices and enable the formation of structures having extremely fine dimensions in the nanometer range, for example, process materials and processing tools with high resolution capabilities have been developed and continue to be developed. Due to such fine shapes and the accompanying increase in device complexity and delicacy, and the increasingly stringent wet etching conditions used in the industry, an organic photoresist underlayer with improved wet etching resistance is required.

[0005] When patterning a metal layer on a substrate, an increase in the wet etching resistance of the organic underlayer has conventionally been achieved by strengthening the interaction between the photoresist underlayer and the underlying metal layer, for example, by incorporating metal interaction moieties into the underlayer. One such technique is disclosed in Patent Document 2, which describes an organic underlayer containing (i) one or more glycidyl groups and (ii) one or more aromatic groups each containing two or more substituents including hydroxy, thiol, and / or amine moieties. However, the incorporation of metal interaction moieties may adversely affect certain desired underlayer properties such as gap filling characteristics and planarization characteristics. Therefore, a method for increasing the resistance of the organic underlayer to wet etching chemicals without substantially changing other desired properties of the underlayer may be desired.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the art, there is a need for an improved method of forming semiconductor devices that addresses one or more problems associated with state-of-the-art technologies.

Means for Solving the Problems

[0009] A new method of forming a semiconductor device is provided that includes the use of a photoresist underlayer and an overcoat layer to provide improved wet etching resistance when patterning a lower metal layer. The method includes: (a) providing a semiconductor substrate including a metal layer; (b) forming an organic underlayer on the metal layer from an organic underlayer coating composition including a crosslinkable compound and a solvent, the organic underlayer being self-crosslinkable and substantially free of an acid generator; (c) curing the organic underlayer, thereby crosslinking the organic underlayer; (d) patterning the cured organic underlayer, thereby exposing regions of the metal layer not covered by the patterned organic underlayer; (e) applying an overcoat coating composition on the substrate including the patterned organic underlayer, the overcoat coating composition including a crosslinkable compound crosslinkable with the patterned organic underlayer and an organic solvent, and the overcoat coating composition being substantially free of an acid generator; (f) curing the overcoat coating composition to cause crosslinking between the compound and the patterned organic underlayer, the resulting overcoat including a first portion crosslinked with the organic underlayer and a second portion not crosslinked with the organic underlayer; (g) removing the second portion of the overcoat from the substrate using an organic-based solution; and (h) wet etching the metal layer using the patterned organic underlayer and the first portion of the overcoat as an etching mask.

[0010] In a further aspect, the method further includes the step of removing from the substrate (i) the patterned organic underlayer and the crosslinked portions of the overcoat composition. In certain preferred aspects, the metal layer can be selected from tungsten, titanium nitride, titanium dioxide, titanium silicon nitride, or tungsten carbonitride. In certain preferred aspects, the crosslinkable compound of the organic underlayer coating composition and the crosslinkable compound of the overcoat coating composition are each a polymer. In certain preferred aspects, the crosslinkable compound of the organic underlayer coating composition and the crosslinkable compound of the overcoat coating composition independently include a hydroxy-substituted aryl group or an amine group. In certain preferred aspects, the organic underlayer coating composition includes a crosslinkable heterocyclic group. In certain preferred aspects, the crosslinkable heterocyclic group is an epoxide group, an oxetane group, or an aziridine group. In certain preferred aspects, the organic underlayer coating composition and the overcoat coating composition are free of free acid.

[0011] The present invention will be described in connection with the following drawings, wherein like reference numerals mean like features.

Brief Description of the Drawings

[0012]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 1E

Figure 1F

Figure 1G

Figure 1H

Figure 2A

Figure 2B

Figure 2C

DETAILED DESCRIPTION OF THE INVENTION

[0013] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. All ranges disclosed herein include the endpoints, and the endpoints are independently combinable with each other. When an element is said to be "on" or "over" another element, it can be in direct contact with the other element or intervening elements may be present therebetween. In contrast, when an element is said to be "directly on" another element, no intervening element is present.

[0014] Unless otherwise noted, a "substituted" group means a group in which one or more of the hydrogen atoms are replaced by one or more substituents. Exemplary substituents include isotopes of hydrogen such as deuterium, hydroxy (OH), halogen (e.g., F, Cl, I, Br), C 1~18 alkyl, C 1~8 haloalkyl, C 3~12 cycloalkyl, C having at least one aromatic ring 6~12 aryl (e.g., phenyl, biphenyl, naphthyl, etc., where each ring can be either a substituted or unsubstituted aromatic ring), C having at least one aromatic ring 7~19 arylalkyl, C 7~12Examples include, but are not limited to, alkylaryl and combinations thereof. For the purpose of determining the number of carbon atoms, when a group is substituted, the number of carbon atoms of that group is the total number of carbon atoms in such a group excluding the carbon atoms of any substituents.

[0015] The method of the present invention according to the first aspect will be described below with reference to FIGS. 1A - H. FIG. 1A shows a cross - sectional view of a semiconductor substrate 100 including a metal layer 102 on the surface of the substrate. The semiconductor substrate can be composed of materials such as silicon or compound semiconductors (e.g., III - V or II - VI), glass, quartz, sapphire, ceramic, copper, etc. Usually, the substrate is a semiconductor wafer such as single - crystal silicon and can have one or more layers formed on its surface and / or patterned features. The layers forming part of the substrate can include, for example, one or more conductive layers such as aluminum, copper, molybdenum, tantalum, titanium, tungsten, titanium tungsten, titanium nitride, titanium dioxide, titanium silicon nitride, tungsten nitride, tungsten carbonitride, nickel, copper, gold, other alloys, or nitrides or silicides of such metals, doped or undoped amorphous silicon or polysilicon layers, one or more dielectric layers such as silicon oxide, silicon nitride, silicon oxynitride, or metal oxide layers, semiconductor layers such as single - crystal silicon, carbon layers, and combinations thereof. The layers can be formed by various techniques such as chemical vapor deposition (CVD) such as plasma - enhanced CVD, low - pressure CVD, atomic layer deposition (ALD), or epitaxial growth, physical vapor deposition (PVD) such as sputtering or evaporation, electroplating, or liquid coating techniques such as spin - coating. The substrate can be of any suitable size. A typical wafer substrate diameter is 200 - 300 mm, but wafers with smaller and larger diameters can also be suitably used according to the present invention.

[0016] The metal layer 102 is disposed on the surface of the substrate. The material of the metal layer 102 is not particularly limited, and the metal layer 102 can be, for example, aluminum, copper, molybdenum, tantalum, titanium, tungsten, nickel, copper, gold, and alloys, nitrides, oxides, or silicides of these metals, such as titanium tungsten, titanium nitride, titanium dioxide, titanium silicon nitride, tungsten nitride, and tungsten carbonitride. Among these, tungsten, titanium nitride, titanium dioxide, titanium silicon nitride, and tungsten carbonitride are typical. The metal layer 102 can be formed by known methods, such as ALD or other CVD techniques, sputtering, evaporation, or electroplating. Among these, ALD is preferred for producing very thin films, such as films on the order of nanometers, dozens of nanometers, or hundreds of nanometers. The thickness of the metal layer 102 is not particularly limited and can be, for example, 1 nm or more, usually 1 to 500 nm, 1 to 300 nm, 1 to 100 nm, or 1 to 30 nm.

[0017] Referring to FIG. 1B, an organic underlayer 104 is formed on the metal layer 102. The organic underlayer is formed from an organic underlayer coating composition containing a thermally crosslinkable compound and an organic solvent. Preferred underlayer coating compositions can be applied by various known coating techniques, such as spin coating, dip coating, meniscus coating, roller coating, slot coating, or spray coating, with spin coating being preferred. The organic underlayer coating composition substantially does not contain an acid generator. As used herein, "substantially does not contain an acid generator" means that the composition has a total amount of thermal acid generator compounds and photoacid generator compounds in an amount of 2% by weight or less, usually 1% by weight or less, 0.5% by weight or less, or 0.1% by weight or less based on the total solids of the composition, or that the composition does not contain any such acid generator compounds at all. The underlayer coating composition is thermally self-crosslinkable in the absence of an acid generator compound, which means that one or more components of the layer formed from the underlayer coating composition are crosslinkable upon heat treatment in the absence of an acid generator compound.

[0018] The thermally crosslinkable compound contains a crosslinkable group selected from, for example, a hydroxyl-substituted aryl group and an amine group, and a phenol group or an amine group is typical. The crosslinkable group is present for internal crosslinking of the lower layer and for interlayer crosslinking between the cured lower layer and an overcoat layer coated on the lower layer. The thermally crosslinkable compound may be a polymer or may be in a non-polymeric form, but a polymer is typical. Polymers suitable for the thermally crosslinkable compound include, for example, polyvinyl aromatic compounds (e.g., polystyrene), poly(meth)acrylates, polyvinyl ethers, polynorbornenes, polyesters, polyarylenes (e.g., polyphenols, novolaks), polyacetals, polyethylene glycols, polyamides, polyacrylamides, polyvinyl alcohols, and copolymers thereof. Typical ones are polymers formed by polymerization of ethylenically unsaturated carbon-carbon double bonds, preferably polymerizable vinyl groups, such as substituted or unsubstituted alkenyl groups, substituted or unsubstituted norbornyl groups, substituted or unsubstituted (meth)acryl groups, substituted or unsubstituted vinyl ether groups, substituted or unsubstituted vinyl ketone groups, substituted or unsubstituted vinyl ester groups, or substituted or unsubstituted vinyl aromatic groups. Among these, polyvinyl aromatic compounds, poly(meth)acrylates, polyarylenes, and polyesters are typical. The polymer may be a homopolymer or may be a copolymer having a plurality of structurally different repeating units, for example, two, three, four, or more different repeating units. The copolymer may be a random copolymer, a block copolymer, etc., but a random copolymer is typical. Usually, the polymer of the lower layer composition of the present invention may have a weight average molecular weight (Mw) of 1000 to about 60,000 Da, 1000 to 50,000 Da, or 2000 to 30,000 Da. The molecular weight of the polymer of the present invention is appropriately determined by gel permeation chromatography.

[0019] Exemplary repeating units having a crosslinkable group suitable for the thermally crosslinkable polymer include the following:

Chemical formula

[0020] The polymer usually contains repeating units having crosslinkable groups in an amount of 5 to 100 mol%, more typically 30 to 100 mol%, even more typically 40 to 100 mol%, based on all the repeating units in the polymer. In an embodiment, the polymer is a homopolymer. When the first polymer is a copolymer, the repeating units are usually present in an amount of 1 to 99 mol%, more typically 5 to 95 mol%, even more typically 10 to 90 mol%.

[0021] The thermally crosslinkable polymer may include one or more additional repeating units that are structurally different from the crosslinkable repeating units. The one or more additional repeating units can include, for example, one or more additional crosslinkable repeating units as described above that are structurally different from the first crosslinkable repeating unit, or may include other types of structurally different repeating units. The thermally crosslinkable polymer may include, for example, repeating units present in one or more additional repeating units of the above type, such as polyvinyl aromatic compounds (e.g., polystyrene), poly(meth)acrylates, polyvinyl ethers, polynorbornenes, polyesters, polyarylenes (e.g., polyphenols, novolacs), polyacetals, polyethylene glycols, polyamides, poly(meth)acrylamides, polyvinyl alcohols, and combinations thereof. In the case of a copolymer, the one or more additional repeating units are usually present in the thermally crosslinkable polymer in an amount of 1 to 99 mol%, more typically 5 to 95 mol%, even more typically 10 to 90 mol%, based on all the repeating units in the polymer, and the sum of all the repeating units of the polymer is 100 mol%.

[0022] Exemplary thermally crosslinkable polymers suitable for use in the lower coating composition include the following:

Chemical formula

Chemical formula

[0023] Suitable non-polymeric (small molecule) thermally crosslinkable compounds include, for example, the monomer precursors of the above crosslinkable polymers, or other non-polymeric compounds containing one or more crosslinkable groups, such as hydroxyl-substituted aryl groups or amine groups.

[0024] The thermally crosslinkable compound is usually present in the lower coating composition in an amount of 0.1 to 20% by weight, more generally 1 to 10% by weight, based on the total solids of the lower composition.

[0025] The organic lower coating composition preferably includes a compound containing one or more crosslinkable heterocyclic groups. The crosslinkable heterocyclic group is preferably selected from an epoxide group, an oxetane group, an aziridine group, or a combination thereof. The compound containing one or more crosslinkable heterocyclic groups may be in polymeric form or non-polymeric form, and may be the same compound as or different from the thermally crosslinkable compound. For example, in the case of a polymeric thermally crosslinkable compound, the polymer can include one or more repeating units containing a crosslinkable heterocyclic group. In the case of the non-polymeric thermally crosslinkable compound as described above, the compound can further include a crosslinkable heterocyclic group. Alternatively, the crosslinkable heterocyclic group can be present in the lower coating composition as a component different from the polymeric or non-polymeric thermally crosslinkable compound. As a component different from the thermally crosslinkable compound, the compound containing a crosslinking agent component is usually present in the lower coating composition in an amount of 0.1 to 20% by weight, more generally 1 to 10% by weight, based on the total solids of the lower composition.

[0026] Suitable exemplary repeating units having a crosslinkable heterocyclic group include the following:

Chemical formula

[0027] Suitable exemplary non-polymeric compounds containing one or more crosslinkable heterocyclic groups include the following: [Chemical formula] are included.

[0028] The lower coating composition may further contain one or more additives selected from, for example, crosslinking agents, surfactants, antioxidants, dyes, or other additives known to those skilled in the art. Any suitable crosslinking agent can be used in the lower coating composition, provided that such a crosslinking agent has at least two, preferably at least three moieties that can react with another component of the composition, such as a thermally crosslinkable compound, under suitable conditions. Exemplary crosslinking agents include novolak resins, epoxy-containing compounds, melamine compounds, guanamine compounds, isocyanate-containing compounds, benzocyclobutene, benzoxazine, etc., usually having two or more, more generally three or more substituents selected from methylol, C1~ 10 alkoxymethyl, and C2~ 10 acyloxymethyl, and the like, but are not limited thereto. Examples of suitable crosslinking agents are those represented by formulas (1) and (2). [Chemical formula] Such crosslinking agents are well known in the art and are commercially available from various suppliers. When present in the lower composition, the amount of such a crosslinking agent can range, for example, from more than 0 to 50% by weight, generally from more than 0 to 30% by weight, based on the total solids of the lower coating composition.

[0029] The lower coating composition of the present invention may optionally contain one or more surfactants (or surface leveling agents). Typical surfactants include those exhibiting amphiphilic properties, meaning they can be both hydrophilic and hydrophobic at the same time. Amphiphilic surfactants have a hydrophilic head group with a strong affinity for water and a long hydrophobic tail that is lipophilic and repels water. Suitable surfactants can be ionic (e.g., anionic, cationic) or non-ionic. Further examples of surfactants include silicone surfactants, poly(alkylene oxide) surfactants, and fluorochemical surfactants. Suitable non-ionic surfactants include octyl and nonylphenol ethoxylates such as TRITON X-114, X-100, X-45, X-15, and branched secondary alcohol ethoxylates such as TERGITOL TMN-6 (Dow Chemical Company, Midland, Michigan USA) and PF-656 (Omnova Solutions, Beachwood, Ohio, USA), but are not limited thereto. Still further exemplary surfactants include alcohol (primary and secondary) ethoxylates, amine ethoxylates, glucosides, glucamines, polyethylene glycols, poly(ethylene glycol-co-propylene glycol), or other surfactants disclosed in (Non-Patent Document 1) published by Manufacturers Confectioners Publishing Co., Glen Rock, N.J. Non-ionic surfactants that are acetylene diol derivatives may also be suitable. Such surfactants are commercially available from Air Products and Chemicals, Inc. (Allentown, PA) and are sold under the trade names SURFYNOL and DYNOL. Additional suitable surfactants include other polymeric compounds such as triblock EO-PO-EO copolymers PLURONIC 25R2, L121, L123, L31, L81, L101, and P123 (BASF, Inc.).When such a surfactant is used, it may be present in the composition in a small amount, for example, in an amount of more than 0 to 1% by weight based on the total solids of the photoresist underlayer composition.

[0030] An antioxidant can be added to prevent or minimize the oxidation of organic materials in the underlying coating composition. Suitable antioxidants include, for example, phenolic antioxidants, antioxidants composed of organic acid derivatives, sulfur-containing antioxidants, phosphorus-based antioxidants, amine-based antioxidants, antioxidants composed of amine-aldehyde condensates, and antioxidants composed of amine-ketone condensates. Examples of phenolic antioxidants include substituted phenols such as 1-oxy-3-methyl-4-isopropylbenzene, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, butylhydroxyanisole, 2-(1-methylcyclohexyl)-4,6-dimethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2-methyl-4,6-dinonylphenol, 2,6-di-tert-butyl-α-dimethylamino-p-cresol, 6-(4-hydroxy-3,5-di-tert-butyl-anilino) 2,4-bis-octyl-thio-1,3,5-triazine, n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butyl-phenyl) propionate, octylated phenol, aralkyl-substituted phenol, alkylated p-cresol, and hindered phenol;Bis-, tris- and poly-phenols, such as 4,4'-dihydroxy diphenyl, methylene bis(dimethyl-4,6-phenol), 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-methyl-6-cyclohexyl phenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 4,4'-methylene-bis-(2,6-di-tert-butylphenol), 2,2'-methylene-bis-(6-α-methyl-benzyl-p-cresol), methylene bridged polyvalent alkylphenol, 4,4'-butylidene bis-(3-methyl-6-tert-butylphenol), 1,1-bis-(4-hydroxyphenyl)-cyclohexane, 2,2'-dihydroxy-3,3'di-(α-methylcyclohexyl)-5,5'-dimethyl diphenylmethane, alkylated bisphenol, hindered bisphenol, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, and tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane may be mentioned.; Suitable antioxidants are commercially available, for example, Irganox™ antioxidants (Ciba Specialty Chemicals Corp.). The antioxidant, when used, is usually present in the gap filling composition in an amount of 0.01 to 10% by weight based on the total solids of the underlying coating composition.;

[0031] The underlying coating composition useful in the method of the present invention may also contain a dye compound that absorbs radiation used to expose the overcoated photoresist layer. Such a dye compound, when used, may be present in an amount of 0.01 to 10% by weight based on the total solids of the underlying coating composition.;

[0032] The lower coating composition further comprises an organic solvent, which can be a single solvent or a mixture of solvents. Suitable solvents include, for example, one or more of oxyisobutyric acid esters, particularly methyl-2-hydroxyisobutyrate, 2-hydroxyisobutyric acid, ethyl lactate, or one or more of glycol ethers, such as 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; solvents having both an ether part and a hydroxy part, such as methoxybutanol, ethoxybutanol, methoxypropanol, and ethoxypropanol; methyl 2-hydroxyisobutyrate; esters, such as methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and other solvents, such as dibasic esters, propylene carbonate, and gamma-butyrolactone; or combinations thereof.

[0033] The concentration of the dry components in the lower coating composition can depend on several factors such as the application method and the target film thickness. Usually, the total solid content of the lower coating composition can be from 0.05 to 20 wt%, preferably from 0.1 to 5 wt% of the total weight of the lower coating composition.

[0034] The lower coating composition is applied onto a substrate, and the thickness of a typical dry layer is about 0.02 to 0.5 μm, preferably, the thickness of the dry layer is about 0.04 to 0.20 μm. Next, the applied lower layer is cured before applying a photoresist composition onto the lower layer. The curing conditions can vary depending on the components of the lower coating composition. Typical curing conditions are from 80 °C to 325 °C, preferably from 150 °C to 300 °C for about 0.5 to 5 minutes. Due to the curing conditions, the lower layer preferably becomes substantially insoluble in the solvent of the photoresist composition coated thereon.

[0035] After such curing, a photoresist composition is applied onto the surface of the lower layer. Various types of photoresists can be suitably used in the method of the present invention, and they can be positive or negative materials. Suitable photoresists include, for example, materials within the EPIC series of photoresists available from DuPont Electronics & Industrial (Marlborough, Massachusetts). The photoresist composition can be applied to the substrate by known coating techniques as described above with respect to the photoresist lower layer composition, but spin coating is typical. The thickness of the photoresist layer can vary widely, but a typical thickness of the photoresist layer is 10 - 300 nm. The photoresist layer is then usually soft baked to minimize the solvent content in the layer, thereby forming a non-stick coating and improving the adhesion of the layer to the substrate. Preferably, mixing of the lower layer and the overcoated photoresist layer should not essentially occur. The soft bake can be carried out on a hot plate or in an oven, but a hot plate is typical. A typical soft bake is carried out at a temperature of 70 - 150 °C and for a time of 30 - 90 seconds.

[0036] The photoresist layer is then exposed to actinic radiation through a photomask or by direct writing to create a solubility difference between the exposed and unexposed regions. The reference herein to exposing a photoresist composition to radiation that activates the composition indicates that the radiation can form a latent image in the photoresist composition. The photomask has optically transparent regions and optically opaque regions corresponding to the regions of the resist layer that are exposed and not exposed, respectively, to the actinic radiation. The exposure wavelength is typically less than 400 nm, more generally less than 300 nm, for example, 248 nm (KrF), 193 nm (ArF), or EUV wavelengths (e.g., 13.5 nm). The actinic radiation can typically be an electron beam (e-beam) by direct writing to the photoresist layer. In a preferred embodiment, the exposure wavelength is 248 nm, 193 nm, or an EUV wavelength. The exposure energy is typically 3 - 300 mJ / cm 2 2, depending, for example, on the exposure tool and the components of the photosensitive composition.

[0037] Following exposure of the photoresist layer, a post-exposure bake (PEB) is typically performed. The PEB can be carried out, for example, on a hot plate or in an oven. The PEB is typically performed at a temperature of 50 °C or higher, more generally in the range of 50 °C - 160 °C.

[0038] The exposed photoresist layer is then developed with a suitable developer to selectively remove the regions of the layer that are soluble in the developer, and the remaining insoluble regions form the resulting photoresist pattern relief image. In the case of a positive photoresist, the exposed regions of the photoresist layer are removed during development, and the unexposed regions remain. Conversely, in a negative photoresist, the exposed regions of the photoresist layer remain, and the unexposed regions are removed during development. Application of the developer can be achieved by any suitable method as described above with respect to the application of the photoresist composition, but spin coating is typical. The development time is a period effective to remove the soluble regions of the photoresist, and a time of 5 - 60 seconds is typical. Development is usually carried out at room temperature.

[0039] The appropriate developer will depend on the materials of the photoresist composition and may include aqueous base developers such as quaternary ammonium hydroxide solutions such as tetramethylammonium hydroxide (TMAH), preferably 0.26 normal (N) TMAH, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like. Suitable organic solvent developers include, for example, those selected from ketones, esters, ethers, hydrocarbons, alcohols, and mixtures thereof.

[0040] The developed substrate can then be selectively processed, for example, on the regions of the underlying layer 104 from which the photoresist has been removed by dry etching according to procedures well known in the art. Suitable etching processes include, for example, plasma etching such as O2, CF4, or H2 / N2 plasma etching, or combinations thereof. As shown in FIG. 1C, the result is a patterned underlying layer 104', whereby the regions of the underlying metal layer 102 are exposed in the regions not covered by the patterned organic underlying layer. The photoresist pattern remaining after etching can then be removed from the substrate by a known photoresist stripping process, such as an O2 plasma ashing process.

[0041] Referring to FIG. 1D, next, an overcoat coating composition is coated over the patterned organic underlayer 104' and the exposed regions of the metal layer 102 to form an overcoat layer 106. The overcoat coating composition includes a compound containing a group capable of covalently bonding (crosslinking) with the organic underlayer and an organic solvent. The overcoat composition substantially does not contain an acid generator. The overcoat layer formed from the composition can covalently bond with the underlying layer, and the overcoat layer is not self-crosslinkable. Thereby, the portion of the upper layer formed from the composition that contacts the underlying layer crosslinks with the underlying layer, while the other portions of the overcoat remain uncrosslinked. Suitable such compounds include those described above with respect to the underlayer coating composition of a thermally crosslinkable polymer and a compound containing one or more crosslinkable heterocyclic groups. To enable covalent bonding with the underlying layer while avoiding self-crosslinking of the coated overcoat composition, the overcoat coating composition preferably includes (i) a compound containing a crosslinkable group selected from, for example, a hydroxyl-substituted aryl group or an amine group, or (ii) a compound containing a crosslinkable heterocyclic group selected from an epoxide group, an oxetane group, an aziridine group, or a combination thereof, but does not include both the groups of (i) and (ii). As described above with respect to the underlayer coating composition, the crosslinkable compound may be a polymer or may be in a non-polymeric form, but polymers are typical.

[0042] The crosslinkable compound of the overcoat coating composition preferably includes one or more groups to increase the hydrophobicity of the compound. Suitable such groups include, for example, (i) an aromatic group substituted with one or more halogen atoms (-F, -Br, -Cl, or -I), usually -F, or (ii) a substituted or unsubstituted alkyl group, for example, a substituted or unsubstituted C 1~10 linear, C 3~10 branched, or C 3~10 cyclic alkyl group is included, and its preferred substituent is a halogen atom, usually -F. Preferred for such hydrophobic groups as part of a crosslinkable polymer are the following general formulas (3) and (4): [Chemical formula] is one or both of the repeating units, and in the above formula, R1 is H, F, CN, substituted or unsubstituted C 1~10 alkyl, usually C 1~3 alkyl; R6 independently represents F, OH, substituted or unsubstituted linear or branched C 1~20 alkyl, substituted or unsubstituted linear or branched C 1~20 alkoxy, and preferably at least one R6 is F or is at least partially fluorinated; R7 represents substituted or unsubstituted linear or branched C 1~20 alkyl, preferably fluoroalkyl; m is an integer from 0 to 5, usually from 1 to 5. By including such repeating units on the polymer, it is considered that the wet etching resistance of the overcoat layer against typical aqueous wet etching agents used for etching the metal layer 102 is enhanced. Suitable exemplary repeating units of formulas (3) and (4) include the following: [Chemical formula] are included.

[0043] The optional repeating units of formulas (3) and (4) can be present in the crosslinkable polymer in an amount of 1 to 80 mol%, more generally 10 to 60 mol%, based on all the repeating units in the crosslinkable polymer, and the sum of all the repeating units of the polymer is 100 mol%.

[0044] In the case of a copolymer, the crosslinkable compound can be a random copolymer, a block copolymer, etc., but a random copolymer is typical. Usually, the polymer of the lower layer composition of the present invention can have a weight average molecular weight (Mw) of 1000 to about 60,000 Da, 1000 to 50,000 Da, or 2000 to 30,000 Da. The molecular weight of the polymer of the present invention is appropriately determined by gel permeation chromatography.

[0045] Exemplary crosslinkable polymers suitable for use in an overcoat coating composition include the following: [Chemical formula] wherein a and b represent the mol% of each repeating unit in the polymer, and the total mol% of all units in the polymer is equal to 100 mol%.

[0046] The crosslinkable compound is usually present in the overcoat coating composition in an amount of 1 to 100% by weight, more typically 1 to 99% by weight, or 10 to 90% by weight, based on the total solids of the overcoat composition.

[0047] The overcoat coating composition may further include one or more additives selected from, for example, surfactants, antioxidants, dyes, or other additives known to those skilled in the art. Suitable such additives and typical amounts are described above with respect to the underlying coating composition. The overcoat coating composition should not substantially contain a crosslinking agent to avoid self-crosslinking of the overcoat layer.

[0048] The overcoat coating composition further comprises an organic solvent which can be a single solvent or a mixture of solvents. Suitable solvents include, for example, one or more oxyisobutyric acid esters, particularly methyl-2-hydroxyisobutyrate, 2-hydroxyisobutyric acid, ethyl lactate, or one or more glycol ethers, such as 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; solvents having both an ether moiety and a hydroxy moiety, such as methoxybutanol, ethoxybutanol, methoxypropanol, and ethoxypropanol; methyl 2-hydroxyisobutyrate; esters, such as methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and other solvents, such as dibasic esters, propylene carbonate, and gamma-butyrolactone; or combinations thereof. The solvent of the overcoat coating composition should be selected such that the underlying layer is substantially insoluble in the overcoat solvent.

[0049] The concentration of the dry components in the overcoat coating composition can depend on several factors such as the application method and the target film thickness. Typically, the total solids content of the overcoat coating composition can be from 0.05 to 20 wt%, preferably from 0.1 to 5 wt% of the total weight of the overcoat coating composition.

[0050] The overcoat coating composition is applied onto a substrate, and the thickness of the typical dried layer is about 0.02 to 0.5 μm, preferably the thickness of the dried layer is about 0.04 to 0.20 μm. Next, the applied overcoat layer is cured, and a covalent bond is obtained between the crosslinkable groups of the overcoat composition and the organic underlying layer. The curing conditions can vary depending on the components of the underlying composition. Typical curing conditions are from 80 °C to 325 °C, preferably from 150 °C to 300 °C for about 0.5 to 5 minutes.

[0051] Referring to FIG. 1E, the portion of the overcoat layer that is not crosslinked to the underlying layer is removed from the substrate by an organic-based remover, leaving the portion 106' of the overcoat layer that is crosslinked to the underlying layer. Removers suitable for the portion of the overcoat material not bonded to the underlying layer include, for example, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl 2-hydroxyisobutyrate, ethyl lactate, and combinations thereof, with a mixture of PGME and PGMEA being preferred.

[0052] Referring to FIG. 1F, the substrate is then contacted with a wet etchant 108 to remove the exposed regions of the metal layer 102 using the patterned photoresist underlying layer and the attached overcoat as an etch mask. Suitable wet etchants and conditions are known in the art and may depend, for example, on the specific materials of the metal layer, underlying layer, and overcoat layer. The wet etchant can be, for example, an acidic or basic aqueous solution, with SC-1 (e.g., 5:1:1 H2O:H2O2:NH4OH) and SC-2 (H2O:H2O2:HCl (5:1:1)) being typical.

[0053] As shown in FIG. 1G, the resulting etched region w of the metal layer exhibits some undercutting of the etching mask due to the isotropic nature of wet etching. The presence of the overcoat provides an improvement in wet etching resistance compared to a process in which the overcoat layer 106 is not used, and thus it is believed that the amount of undercutting is reduced. FIGS. 2A - C show a related art process including a lower layer without the overcoat described herein. As shown in FIGS. 2B - C, the wet etching region w' in this process without the overcoat may exhibit undercutting of the etching mask 104' that is significantly greater than when using a lower layer having the overcoat described herein. This more extensive undercutting can have an adverse effect on the resulting device structure and the electrical characteristics of the final device. The patterned portions 106' of the overcoat layer and 102' of the lower layer remaining after wet etching of the metal layer can be removed from the substrate using known techniques and materials, for example, by oxygen plasma ashing, as shown in FIG. 1H.

[0054] Following the patterning described, further processing is performed to form the final semiconductor device. The further processing can include, for example, the fabrication of semiconductor devices such as memory devices, processor chips (CPUs), graphics chips, optoelectronic chips, LEDs, OLEDs, and other electronic devices.

[0055] The following non - limiting examples illustrate the present invention.

Example

[0056]

Chemical formula

[0057] Synthesis of Polymer Polymer P1 (Mw ~ 11,000) (Aldrich Chemical Co.).

[0058] Example 1 (Polymer P2) 60.0 g of ethyl lactate was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C and refluxed under nitrogen. 40.0 g of 4-hydroxyphenyl methacrylate and 10.34 g of V-601HP initiator (dimethyl 2,2'-azobis(2-methylpropionate)) (FUJIFILM Wako Chemicals) were dissolved in 60.0 g of cyclohexanone, and the prepared mixed solution was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature while stirring. The reaction mixture was precipitated with heptane / methyl tert-butyl ether (MTBE) (6:4) (10-fold excess of the reaction mixture). After the precipitate settled, the solvent was removed by decantation, and the precipitate was dried in air. The obtained white solid precipitate was redissolved in 120 g of tetrahydrofuran (THF) and precipitated from heptane / MTBE (6:4). After the precipitate settled, the solvent was removed by decantation, and then the precipitate was replaced with PGMEA solvent.

[0059] Example 2 (Polymer P3) In a 100 mL three-necked round-bottom flask equipped with a temperature control unit, 30.0 g of o-cresol, 7.023 g of paraformaldehyde, and 0.160 g of methanesulfonic acid were dissolved in 30.0 g of propylene glycol methyl ether (PGME). The reactor was heated to 120 °C for 5 hours. The reaction mixture was diluted to a 30 wt% solution with THF and precipitated with heptane / MTBE (4:1) (10-fold excess of the reaction mixture). After the precipitate settled, the solvent was removed by decantation, and the precipitate was dried in a vacuum oven at 40 °C for 1 day to form a dry powder. The dry polymer was replaced with PGMEA solvent.

[0060] Example 3 (Polymer P4) 45.7 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 22.25 g of 4-hydroxyphenyl methacrylate, 17.75 g of glycidyl methacrylate, and 6.90 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with heptane / MTBE (6:4) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation, and the precipitate was dried in a vacuum oven at 40 °C for 1 day to form a dry powder. The dry polymer was replaced with a PGMEA solvent.

[0061] Example 4 (Polymer P5) 24.1 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 40.0 g of glycidyl methacrylate and 2.59 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA, and the mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was diluted to a 25 wt% solution with THF and precipitated with MTBE (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 50 °C for 1 day.

[0062] Example 5 (Polymer P6) 20.0 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 75 °C. 24.36 g of 4-acetoxystyrene (ACS), 15.64 g of styrene (Sty), and 3.36 g of V-65 initiator (2,2’-azobis(2,4-dimethylvaleronitrile)) (FUJIFILM Wako Chemicals) were dissolved in 40.0 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with methanol (MeOH) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 40 °C for 1 day to form a dry powder. 20.0 g of the dry powder and 0.487 g of 25 wt% sodium methoxide (NaOMe) in MeOH were dissolved in 46.67 g of MeOH in a round-bottom flask equipped with a condenser and a magnetic stirrer. Next, the solution was heated to 65 °C for 5 hours with stirring. The solvent was evaporated with a rotary evaporator, the resulting product was dissolved in ethyl acetate, and washed with deionized water. The organic layer was separated, and the solvent was removed with a rotary evaporator. The polymer was replaced with a PGMEA solvent.

[0063] Example 6 (Polymer P7) 20.0 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 75 °C. 22.82 g of 4-acetoxystyrene (ACS), 17.18 g of 4-fluorostyrene (FS), and 3.15 g of V-65 initiator (FUJIFILM Wako Chemicals) were dissolved in 40.0 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature while stirring naturally. The reaction mixture was precipitated with MeOH (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 40 °C for 1 day to form a dry powder. In a round-bottom flask equipped with a condenser and a magnetic stirrer, 20.0 g of the dry powder and 0.456 g of 25% NaOMe in MeOH were dissolved in 46.67 g of MeOH. Next, the solution was heated to 65 °C for 5 hours while stirring. The solvent was evaporated with a rotary evaporator, the resulting product was dissolved in ethyl acetate, and washed with deionized water. The organic layer was separated, and the solvent was removed with a rotary evaporator. The polymer was replaced with a PGMEA solvent.

[0064] Example 7 (Polymer P8) 45.7 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 22.25 g of 4-hydroxyphenyl methacrylate, 17.75 g of n-butyl methacrylate, and 6.90 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature while stirring. The reaction mixture was precipitated with heptane / MTBE (1:1) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation, and the precipitate was dried in a vacuum oven at 40 °C for 1 day. The polymer was replaced with a PGMEA solvent.

[0065] Example 8 (Polymer P9) 20.0 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 75 °C. 13.12 g of 4-acetoxystyrene, 26.88 g of 3,3,4,4,5,5,6,6,6-nonafluorohexyl methacrylate, and 1.81 g of V-65 initiator (FUJIFILM Wako Chemicals) were dissolved in 40.0 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with MeOH (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 40 °C for 1 day to form a dry powder. In a round-bottom flask equipped with a condenser and a magnetic stirrer, 20.0 g of the dry powder and 0.262 g of 25% NaOMe in MeOH were dissolved in 46.67 g of MeOH. The solution was heated to 65 °C for 5 hours with stirring. After the solvent was evaporated by a rotary evaporator, the resulting product was dissolved in ethyl acetate and washed with deionized water. The organic layer was separated, and the solvent was removed by a rotary evaporator. The polymer was replaced with a PGMEA solvent.

[0066] Example 9 (Polymer P10) 45.7 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 21.51 g of glycidyl methacrylate, 18.49 g of 4-fluorostyrene, and 8.36 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with isopropanol (IPA) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 40 °C for 1 day.

[0067] Example 10 (Polymer P11) 45.7 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 20.0 g of glycidyl methacrylate, 20.0 g of n-butyl methacrylate, and 7.77 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with IPA (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 40 °C for 1 day.

[0068] Example 11 (Polymer P12) 45.7 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 11.99 g of glycidyl methacrylate, 28.01 g of 3,3,4,4,5,5,6,6,6-nonafluorohexyl methacrylate, and 4.66 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with heptane (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by filtration, and the precipitate was dried in a vacuum oven at 40 °C for 1 day.

[0069] Example 12 (Polymer P13) 45.7 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 22.60 g of 2-hydroxyethyl methacrylate, 17.40 g of methyl methacrylate, and 9.60 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with heptane / MTBE (4:1) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation. Next, the precipitate was dried in a vacuum oven at 40 °C for 1 day.

[0070] Example 13 (Polymer P14) 45.7 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 22.22 g of 2-hydroxyethyl methacrylate, 17.78 g of styrene, and 9.44 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with heptane / MTBE (4:1) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation. Next, the precipitate was dried in a vacuum oven at 40 °C for 1 day.

[0071] Example 14 (Polymer P15) 45.7 g of PGMEA was charged into a 250 ml three-necked round-bottom flask equipped with a temperature control unit. The reactor was heated to 90 °C. 19.11 g of 2-hydroxyethyl methacrylate, 20.89 g of n-butyl methacrylate, and 8.12 g of V-601HP initiator (FUJIFILM Wako Chemicals) were dissolved in 74.3 g of PGMEA. The mixture was fed to the reactor for 180 minutes. After the feeding was completed, the reactor was maintained at 90 °C for an additional 60 minutes. After the reaction, the reactor was cooled to room temperature with stirring. The reaction mixture was precipitated with heptane / MTBE (4:1) (10-fold excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation. Next, the precipitate was dried in a vacuum oven at 40 °C for 1 day.

[0072] Preparation of the lower layer composition Examples 15 - 20 The lower layer composition (UC) was prepared by dissolving the solid components in the solvent using the materials and amounts described in Table 1. The mixture was shaken on a mechanical shaker for at least 4 hours. The resulting mixture was filtered through a PTFE 0.45 μm membrane filter.

[0073] [Table 1]

[0074] [Chemical formula]

[0075] Preparation of the overcoat composition Examples 21 - 30 The overcoat composition (OC) was prepared by dissolving the solid components in the solvent using the materials and amounts described in Table 2. The mixture was shaken on a mechanical shaker for at least 4 hours. The resulting mixture was filtered through a PTFE 0.45 μm membrane filter.

[0076] [Table 2]

[0077] Evaluation of Solvent Resistance / Peelability Examples 31 to 46 On an ACT-8 Clean Track (Tokyo Electron Co.), each of the above lower layer composition or overcoat composition was spin-coated on a 200 mm silicon wafer at 1500 rpm for 60 seconds, and then baked on a hot plate at 220 °C for 60 seconds to form a lower layer or overcoat film. Next, the film thickness was measured with a Therma-Wave OptiProbe (trademark) 5250 measurement tool. Next, in the Clean Track, 30 mL of a PGME / PGMEA (70 / 30 wt / wt) remover was applied to the film for 90 seconds. The wafer was spin-dried at 4000 rpm for 60 seconds and soft-baked on a hot plate at 110 °C for 60 seconds. The thickness of each film was measured again to determine the loss amount of the film thickness. The change in film thickness between before and after applying the remover (i.e., the thickness of the film removed by the remover) was calculated using the following formula 1: ΔFT = FT i -FT f (1) wherein, in the above formula, FT i is the initial film thickness (before applying the remover) of the lower layer or overcoat composition, and FT f is the final film thickness (after applying the remover). The results are shown in Table 3.

[0078] [Table 3]

[0079] As can be seen from Table 3, each of the lower layer compositions UC-1 to UC-6 showed a negligible peel loss by the organic remover, indicating complete crosslinking of the composition. Each of the overcoat compositions OC-1 to OC-10 showed substantially complete removal by the remover.

[0080] Evaluation of Interlayer Crosslinking Examples 47 - 61 At ACT - 8 Clean Track (Tokyo Electron Co.), the underlayer compositions shown in Table 4 were spin - coated onto each 200 - mm silicon wafer at 1500 rpm for 60 seconds. Next, the wafer was baked on a hot plate at 220°C for 60 seconds to form a cured underlayer with a thickness of 150 nm as measured by a Therma - Wave OptiProbe (trademark) 5250 measurement tool. The overcoat compositions shown in Table 4 were spin - coated onto the underlayer at 1500 rpm for 60 seconds. The wafer was baked at 220°C for 60 seconds and then cooled to room temperature. Next, in the Clean Track, 30 mL of a PGME / PGMEA (70 / 30 wt / wt) remover was applied to the film for 90 seconds. The wafer was spin - dried at 4000 rpm for 60 seconds and soft - baked on a hot plate at 110°C for 60 seconds. The thickness of the resulting two - layer film was measured with a measurement tool. The thickness of the adhered overcoat (FT oc ) was calculated as the difference between the final thickness of the two - layer film (FT f ) and the initial thickness of the underlayer film (FT i ) using the following Equation 2: FT oc =FT f - FT i (2) and the results are shown in Table 4.

[0081]

Table 4

[0082] As can be seen from Table 4, the two-layer stacks of Comparative Examples 52 and 59 to 61 show that the thickness after solvent peeling is equal to the thickness of the lower layer, indicating that there is almost no amount of the overcoat layer remaining attached to the lower layer, which is considered to be due to the absence of an interlayer crosslink between the lower layer and the overcoat layer. In contrast, the two-layer stacks of Examples 47 to 51 and 53 to 58 according to the present invention showed that the thickness after solvent peeling was greater than the thickness of the lower layer. This indicates that an interlayer crosslink occurred between the lower layer and the overcoat film.

[0083] Evaluation of wet etching resistance Examples 62 to 81 In a Nano-ALD2000 ALD system (Integrated Process Systems Ltd.), titanium nitride (TiN) was deposited on a 200 mm silicon wafer by atomic layer deposition (ALD) using tetrakis(dimethylamino)titanium (TDMAT) as a precursor at a total pressure of 10 SCCM and 0.34 Torr, and the deposition cycle was repeated until a target thickness of 10 nm was reached. After cutting the deposited wafer into coupons (4 cm × 4 cm pieces), the lower layer and overcoat compositions shown in Table 5 were spin-coated. Coating, curing, and film thickness measurement were performed as described above for the evaluation of interlayer crosslinking, and a J.A.Woollam M-2000 ellipsometer was used for thickness measurement. To evaluate the wet etching resistance, the obtained multilayer film stack was immersed in an SC-1 wet etching solution. The etching solution was prepared by mixing 35 wt% ammonium hydroxide and 30 wt% hydrogen peroxide (NH4OH:H2O2:H2O = 1:1:10) with a bath temperature of 50°C. The resistance of the film to the wet etching agent was evaluated by measuring the duration time (t end ) until visual damage to the film was observed. The results are shown in Table 5.

[0084]

Table 5

[0085] Based on the results in Table 5, the use of an overcoat layer that can be crosslinked with the underlying layer resulted in an improvement in the wet etching resistance of the underlying film compared to the use of only the underlying layer (Comparative Examples 62 to 66) or the use of a combination of an underlying layer and an overcoat that does not show interlayer crosslinking (Comparative Examples 72 and 79 to 81).

Explanation of symbols

[0086] 100 Semiconductor substrate 102 Metal layer 104 Organic underlying layer 106 Overcoat layer 108 Wet etching agent

Claims

1. A method of forming a semiconductor device, comprising: (a) providing a semiconductor substrate including a metal layer; (b) forming an organic underlayer on the metal layer from an organic underlayer coating composition including a crosslinkable compound and a solvent, wherein the organic underlayer is self-crosslinkable and substantially free of an acid generator; (c) curing the organic underlayer to crosslink the organic underlayer; (d) patterning the cured organic underlayer to expose regions of the metal layer not covered by the patterned organic underlayer; (e) applying an overcoat coating composition on the substrate including the patterned organic underlayer, wherein the overcoat coating composition includes a crosslinkable compound crosslinkable with the patterned organic underlayer and an organic solvent, and the overcoat coating composition is substantially free of an acid generator; (f) curing the overcoat coating composition to cause crosslinking between the compound and the patterned organic underlayer, wherein the resulting overcoat includes a first portion crosslinked with the organic underlayer and a second portion not crosslinked with the organic underlayer; (g) removing the second portion of the overcoat from the substrate using an organic-based solution; and (h) wet etching the metal layer using the patterned organic underlayer and the first portion of the overcoat as an etching mask. A method comprising the above steps.

2. The method according to claim 1, further comprising (i) removing the patterned organic underlayer and the crosslinked portion of the overcoat composition from the substrate.

3. The method according to claim 1, wherein the metal layer is selected from tungsten, titanium nitride, titanium dioxide, titanium silicon nitride, or tungsten carbonitride.

4. The method according to any one of claims 1 to 3, wherein the crosslinkable compound of the organic underlayer coating composition and the crosslinkable compound of the overcoat coating composition are each a polymer.

5. The method according to any one of claims 1 to 4, wherein the crosslinkable compound of the organic underlayer coating composition and the crosslinkable compound of the overcoat coating composition independently contain a hydroxy-substituted aryl group or an amine group.

6. The method according to claim 1 or 5, wherein the organic underlayer coating composition contains a crosslinkable heterocyclic group.

7. The method according to claim 6, wherein the crosslinkable heterocyclic group is an epoxide group, an oxetane group, or an aziridine group.

8. The method according to any one of claims 1 to 7, wherein the organic underlayer coating composition and the overcoat coating composition do not contain a free acid.

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