Method of forming semiconductor device

Abstract

A method of forming a semiconductor device 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 comprising 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, thereby crosslinking the organic underlayer; (d) patterning the cured organic bottom layer so as to expose a region of the metal layer which is not covered by the patterned organic bottom layer; (e) applying an overcoat coating composition on the substrate comprising the patterned organic underlayer, wherein the overcoat coating composition comprises a cross-linkable compound capable of cross-linking with the patterned organic underlayer; and an organic solvent; wherein the overcoat coating composition is substantially free of an acid generator; (f) curing the overcoat coating composition to cause cross-linking between the compound and the patterned organic underlayer, wherein the resulting overcoat comprises a first portion that is cross-linked with the organic underlayer and a second portion that is not cross-linked with the organic underlayer; (g) removing a second portion of the overcoat from the substrate with an organic-based solution; and (h) wet etching the metal layer using the patterned organic underlayer and the first portion of the overcoat layer as an etch mask. These methods are particularly useful for forming fine lithographic patterns in the semiconductor manufacturing industry.

Description

BACKGROUND OF THE INVENTION 1. Technical Field

[0001] The present invention generally relates to the fabrication of electronic devices. More particularly, the present invention relates to methods of forming semiconductor devices that involve patterning a metal layer by wet etching. These methods are particularly useful for forming fine lithographic patterns in the semiconductor manufacturing industry. 2. Description of Related Technologies

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

[0003] Reflection of the activating radiation used to expose the photoresist generally limits the resolution of the patterned image in the photoresist layer. Reflection of the radiation from the substrate / photoresist interface can cause spatial variations in the radiation intensity in the photoresist, resulting in non-uniform photoresist line widths upon development. The radiation can also scatter from the substrate / photoresist interface into regions of the photoresist that are not intended to be exposed, again resulting in line width variations. This reflection and light scattering can be particularly problematic when the layer to be patterned on the substrate is reflective, which is typical when patterning a metal layer.

[0004] Known methods for reducing the radiation problems of reflection during photoresist layer exposure are to use a radiation-absorbing organic underlayer inserted between the substrate surface and the photoresist coating (see, for example, US2016 / 0187778 A1). To increase the integration density of semiconductor devices and to permit the formation of structures having extremely fine dimensions (e.g., in the nanometer range), processing materials and processing tools with high resolution capabilities have been developed and continue to be developed. As such fine geometries and the attendant device complexity and fineness increase, as well as the increasingly demanding wet etching conditions used in the industry, there is a need for organic photoresist underlayers with improved resistance to wet etching.

[0005] When forming a metal layer on a patterned substrate, the increased wet etch resistance of an organic underlayer is conventionally achieved by enhancing the interaction between the photoresist underlayer and the underlying metal layer (such as by incorporating metal interaction moieties into the underlayer). One such technique is disclosed in US10,527,942B2, which describes an organic underlayer comprising (i) one or more glycidyl groups, and (ii) one or more aromatic groups, each of which contains two or more substituents including hydroxyl, thiol, and / or amine moieties. However, incorporating metal interaction moieties may adversely affect certain desired underlayer properties (such as gap filling and planarization properties). Accordingly, a method is desired for increasing the tolerance of an organic underlayer to wet etch chemicals without substantially altering other desired properties of the underlayer.

[0006] There is a need in the art for improved methods of forming semiconductor devices that address one or more problems associated with the prior art. SUMMARY OF THE INVENTION

[0007] The present invention provides new methods of forming semiconductor devices that involve using a photoresist underlayer and an outer coating that provides enhanced wet etch resistance when patterning an underlying metal layer. The methods include: (a) providing a semiconductor substrate comprising 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, wherein the organic underlayer is self-crosslinkable and substantially free of an acid generator; (c) curing the organic underlayer such that the organic underlayer crosslinks; (d) patterning the cured organic underlayer to expose areas of the metal layer not covered by the patterned organic underlayer; (e) applying an outer coating composition on the substrate comprising the patterned organic underlayer, wherein the outer coating composition comprises a crosslinkable compound capable of crosslinking with the patterned organic underlayer; and an organic solvent; wherein the outer coating composition is substantially free of an acid generator; (f) curing the outer coating composition to cause crosslinking between the compound and the patterned organic underlayer, wherein the resulting outer coating comprises 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 outer coating from the substrate with an organic-based solution; and (h) wet etching the metal layer using the patterned organic underlayer and the first portion of the outer coating as an etch mask.

[0008] In another aspect, the method further comprises: (i) removing the patterned organic underlayer and the crosslinked portion of the overcoat composition from the substrate. In certain preferred aspects, the metal layer may 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 polymers. In certain preferred aspects, the crosslinkable compound of the organic underlayer coating composition and the crosslinkable compound of the overcoat coating composition independently comprise a hydroxy-substituted aryl or amine group. In certain preferred aspects, the organic underlayer coating composition comprises a crosslinkable heterocyclic group. In certain preferred aspects, the crosslinkable heterocyclic group is an epoxy 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be described with reference to the following drawings, in which like reference numerals represent like features, and in the drawings:

[0010] Figures 1A - 1H An exemplary process flow for forming a semiconductor device according to the present invention is illustrated in cross-section; and

[0011] Figures 2A - 2C A comparative process flow of the related art is illustrated in cross-section. DETAILED DESCRIPTION

[0012] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. Unless the context otherwise indicates, the singular forms "a / an" and "the" are intended to include the singular and plural forms. All ranges disclosed herein include the endpoints, and the endpoints can be combined independently of each other. When an element is referred to as being "on" or "above" another element, it can be in direct contact with the other element or there may be intervening elements therebetween. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0013] Unless otherwise specified, a "substituted" group means a group in which one or more of its hydrogen atoms are replaced by one or more substituents. Exemplary substituents include, but are not limited to, 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., each ring being a substituted or unsubstituted aromatic), C having at least one aromatic ring7-19 Arylalkyl, C 7-12 Alkylaryl, and combinations thereof. For the purposes of determining the number of carbon atoms, when the group is substituted, the number of carbon atoms in the group is the total number of carbon atoms in the group, excluding those of any substituents.

[0014] Reference will now be made Figure 1A -H to describe the method of the present invention according to the first aspect. Figure 1A A semiconductor substrate 100 is shown in cross-section and includes a metal layer 102 on the surface of the substrate. The semiconductor substrate can be a material such as silicon, or a compound semiconductor (e.g., III-V or II-VI), glass, quartz, sapphire, ceramic, copper, etc. Typically, the substrate is a semiconductor wafer such as single-crystalline silicon and can have one or more layers and / or patterned features formed on its surface. The layers forming part of the substrate can include, for example, one or more conductive layers (such as layers of 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 or polycrystalline silicon), one or more dielectric layers (such as layers of silicon oxide, silicon nitride, silicon oxynitride or metal oxides), semiconductor layers (such as single-crystalline silicon), carbon layers and combinations thereof. These 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 to 300 mm, but wafers with smaller and larger diameters can be suitably employed according to the present invention.

[0015] 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 such metals (such as titanium tungsten, titanium nitride, titanium dioxide, titanium silicon nitride, tungsten nitride, and tungsten carbonitride). Among them, 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 them, ALD is preferably used to produce very thin films (such as those on the order of nanometers, tens 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 greater, typically 1 to 500 nm, 1 to 300 nm, 1 to 100 nm, or 1 to 30 nm.

[0016] Reference Figure 1B, an organic underlayer 104 is formed on the metal layer 102. The organic underlayer is formed from an organic underlayer coating composition that includes a thermally crosslinkable compound and an organic solvent. The preferred underlayer coating composition can be applied by various known coating techniques (e.g., spin coating, dip coating, meniscus-coating, roll coating, slot coating, or spray coating), with spin coating being preferred. The organic underlayer coating composition is substantially free of acid generators. As used herein, "substantially free of acid generators" means that the composition has a combined amount of thermal acid generator compounds and photoacid generator compounds of 2 wt% or less, typically 1 wt% or less, 0.5 wt% or less, or 0.1 wt% or less based on the total solids of the composition, or the composition is completely free of such acid generator compounds. The underlayer coating composition is thermally self-crosslinkable in the absence of acid generator compounds, meaning that one or more components of the layer formed from the underlayer coating composition are capable of crosslinking under heat treatment in the absence of acid generator compounds.

[0017] The thermally crosslinkable compound contains crosslinkable groups selected from, for example, hydroxy-substituted aryl and amine groups, where phenolic groups or amine groups are typical. There are crosslinkable groups that are used both for internal crosslinking of the substrate layer and for interlayer crosslinking between the cured substrate layer and the topcoat to be applied over the substrate layer. The thermally crosslinkable compound can be polymeric or can be in non-polymeric form, where polymeric is typical. Suitable polymers for the thermally crosslinkable compound include, for example, polyvinyl aromatics (e.g., polystyrene), poly(meth)acrylates, polyvinyl ethers, polynorbornenes, polyesters, polyarylenes (e.g., polyphenols, novolacs), polyacetals, polyethylene glycols, polyamides, polyacrylamides, polyvinyl alcohols, and their copolymers. Typically, the polymers are formed by polymerization of ethylenically unsaturated carbon-carbon double bonds, which are preferably polymerizable vinyl groups (e.g., substituted or unsubstituted alkenyl groups), substituted or unsubstituted norbornyl groups, substituted or unsubstituted (meth)acrylic 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 them, polyvinyl aromatics, poly(meth)acrylates, polyarylene compounds, and polyesters are typical. The polymer can be a homopolymer or can be a copolymer having multiple structurally different repeating units, such as two, three, four, or more different repeating units. The copolymer can be a random copolymer, a block copolymer, etc., where random copolymers are typical. Typically, the polymers of the substrate composition of the present invention will 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 polymers of the present invention is suitably determined by gel permeation chromatography.

[0018] Suitable exemplary repeating units having crosslinkable groups for the thermally crosslinkable polymers include the following:

[0019] The polymer typically contains repeating units having crosslinkable groups in an amount of 5 to 100 mol%, more typically 30 to 100 mol%, and still more typically 40 to 100 mol% based on the total repeating units in the polymer. In an embodiment, the polymer is a homopolymer. When the first polymer is a copolymer, the repeating units are typically present in an amount of 1 to 99 mol%, more typically 5 to 95 mol%, and still more typically 10 to 90 mol%.

[0020] The thermally crosslinkable polymer may comprise one or more additional repeating units that are structurally different from the crosslinkable repeating units. The one or more additional repeating units may include, for example, one or more additional crosslinkable repeating units that are structurally different from the first crosslinkable repeating unit as described above, or may include other types of structurally different repeating units. The thermally crosslinkable polymer may, for example, comprise one or more additional repeating units of the above types, such as those present in polyvinyl aromatic hydrocarbons (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 typically present in the thermally crosslinkable polymer in an amount of from 1 to 99 mol%, more typically from 5 to 95 mol%, and still more typically from 10 to 90 mol% based on the total repeating units in the polymer, where the sum of all repeating units of the polymer is 100 mol%.

[0021] Suitable exemplary thermally crosslinkable polymers for the undercoat composition include the following: where a, b, and c represent the mol% of the respective repeating units within the polymer, where the total mol% of all units in the polymer equals 100 mol%.

[0022] Suitable non-polymeric (small molecule) thermally crosslinkable compounds include, for example, monomer precursors of the above crosslinkable polymers, or other non-polymeric compounds containing one or more crosslinkable groups (e.g., hydroxy-substituted aryl or amine groups).

[0023] The thermally crosslinkable compound is typically present in the undercoat composition in an amount of from 0.1 to 20 wt%, more typically from 1 to 10 wt%, based on the total solids of the undercoat composition.

[0024] The organic undercoat composition preferably contains a compound containing one or more crosslinkable heterocyclic groups. The crosslinkable heterocyclic groups are preferably selected from epoxy groups, oxetane groups, aziridine groups, or combinations thereof. The compound containing one or more crosslinkable heterocyclic groups can be in the form of a polymer or a non-polymer, and can be the same compound or a different compound from the thermally crosslinkable compound. For example, in the case of a thermally crosslinkable compound in the form of a polymer, the polymer can contain one or more repeating units containing crosslinkable heterocyclic groups. In the case of a non-polymer thermally crosslinkable compound as described above, the compound can further contain crosslinkable heterocyclic groups. Alternatively, the crosslinkable heterocyclic groups can be present in the undercoat composition as a component different from the thermally crosslinkable compound in the form of a polymer or a non-polymer. As a component different from the thermally crosslinkable compound, the compound containing a crosslinking agent component typically exists in the undercoat composition in an amount of 0.1 to 20 wt%, more typically 1 to 10 wt%, based on the total solids of the undercoat composition.

[0025] Suitable exemplary repeating units having crosslinkable heterocyclic groups include the following:

[0026] Suitable exemplary non-polymer compounds containing one or more crosslinkable heterocyclic groups include the following:

[0027] The undercoat composition can 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 undercoat composition provided that such a crosslinking agent has at least 2, and preferably at least 3, moieties capable of reacting with another component of the composition (e.g., a thermally crosslinkable compound) under suitable conditions. Exemplary crosslinking agents include, but are not limited to, novolak resins, epoxy group-containing compounds, melamine compounds, guanamine compounds, isocyanate group-containing compounds, benzocyclobutene, benzoxazine, etc., and are typically those having 2 or more, more typically 3 or more, substituents selected from hydroxymethyl, C 1-10 alkoxymethyl, and C 2-10 acyloxymethyl. Examples of suitable crosslinking agents are those represented by formulas (1) and (2). Such crosslinking agents are well known in the art and are commercially available from a number of sources. When present in the underlying composition, the amount of such crosslinking agent can be, for example, in the range of greater than 0 to 50 wt%, and typically greater than 0 to 30 wt%, based on the total solids of the underlying coating composition.

[0028] The underlying coating composition of the present invention may optionally contain one or more surfactants (or surface leveling agents). Typical surfactants include those exhibiting amphiphilic properties, which means that they can be hydrophilic and hydrophobic at the same time. Amphiphilic surfactants have one or more hydrophilic head groups (which have a strong affinity for water) and a long hydrophobic tail (which is organophilic and repels water). Suitable surfactants can be ionic (e.g., anionic, cationic) or nonionic. Additional examples of surfactants include silicone surfactants, poly(oxyalkylene) surfactants, and fluorinated compound surfactants. Suitable nonionic surfactants include, but are not limited to, 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). Still additional exemplary surfactants include alcohol (primary and secondary alcohol) ethoxylates, amine ethoxylates, glucosides, glucamines, polyethylene glycols, poly(ethylene glycol-co-propylene glycol), or other surfactants disclosed in the North American edition of McCutcheon's Emulsifiers and Detergents published by Manufacturers Confectioners Publishing Co., Glen Rock, New Jersey, in 2000. Nonionic surfactants that are alkynediol derivatives can also be suitable. Such surfactants are commercially available from Air Products and Chemicals, Inc., Allentown, Pennsylvania, and are sold under the trade names SURFYNOL and DYNOL. Additional suitable surfactants include other polymeric compounds such as the triblock EO-PO-EO copolymers PLURONIC 25R2, L121, L123, L31, L81, L101, and P123 (BASF, Inc.). If used, such surfactants can be present in small amounts, e.g., greater than 0 to 1 wt% based on the total solids of the photoresist underlying composition, in the composition.

[0029] Antioxidants can be added to prevent or minimize the oxidation of organic materials in the underlying coating composition. Suitable antioxidants include, for example, phenol-based 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 phenol-based 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, butylated hydroxyanisole, 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-butylanilino)2,4-bis-octyl-thio-1,3,5-triazine, n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, octylated phenol, aralkyl-substituted phenols, alkylated p-cresols, and hindered phenols; bisphenols, triphenols, and polyphenols such as 4,4'-dihydroxybiphenyl, methylenebis(dimethyl-4,6-phenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-methylenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(6-α-methyl-benzyl-p-cresol), methylene-crosslinked polyvalent alkylphenols, 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2'-dihydroxy-3,3'-di(α-methylcyclohexyl)-5,5'-dimethyl diphenylmethane, alkylated bisphenols, hindered bisphenols, 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 tetra-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. Suitable antioxidants are commercially available, for example, Irganox TM antioxidants (Ciba Specialty Chemicals Corp.). If used, the antioxidant is typically present in the gap-filling composition in an amount of 0.01 to 10 wt% based on the total solids of the underlying coating composition.

[0030] The underlying coating composition that can be used in the method of the present invention may also contain a dye compound that absorbs the radiation used to expose the photoresist layer of the overcoat. If used, such a dye compound may be present in an amount of 0.01 to 10 wt% based on the total solids of the underlying coating composition.

[0031] The underlying coating composition further comprises an organic solvent, which may be a single solvent or a mixture of solvents. Suitable solvents include, for example, one or more of oxyisobutyrates, especially one or more of methyl 2-hydroxyisobutyrate, 2-hydroxyisobutyric acid, ethyl lactate, or glycol ethers, such as 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; solvents having both ether and hydroxyl moieties, 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 γ-butyrolactone; or combinations thereof.

[0032] The concentration of the dry components in the underlying coating composition will depend on several factors, such as the application method and the target film thickness. Typically, the total solids content of the underlying coating composition may be 0.05 to 20 wt% of the total weight of the underlying coating composition, preferably 0.1 to 5 wt% of the underlying coating composition.

[0033] The underlying coating composition is applied to the substrate at a typical dry layer thickness of about 0.02 to 0.5 μm, preferably about 0.04 to 0.20 μm. Then the applied underlying layer is cured before applying the photoresist composition on the underlying layer. The curing conditions will vary with the components of the underlying coating composition. Typical curing conditions are 80 °C to 325 °C, preferably 150 °C to 300 °C, for about 0.5 to 5 minutes. The curing conditions preferably render the underlying layer substantially insoluble in the solvent of the photoresist composition to be coated on the underlying layer.

[0034] After such curing, a photoresist composition is applied to the surface of the underlying layer. A variety of photoresists can be suitably used in the method of the present invention and can be positive or negative materials. Suitable photoresists include, for example, materials within the EPIC series of photoresists available from DuPont Electronics & Industrial of Marlborough, Massachusetts. The photoresist composition can be applied to the substrate by known coating techniques such as those described above for the photoresist underlying layer composition, where spin coating is typical. The thickness of the photoresist layer can vary widely, with a typical thickness of the photoresist layer being 10 to 300 nm. Next, the photoresist layer is typically soft baked to minimize the solvent content in the layer, thereby forming a tack-free coating and improving the adhesion of the layer to the substrate. Preferably, there should be substantially no intermixing of the underlying layer and the overcoated photoresist layer. The soft bake can be carried out on a hot plate or in an oven, where a hot plate is typical. The typical soft bake is carried out at a temperature of 70 °C to 150 °C for a time of 30 to 90 seconds.

[0035] Next, the photoresist layer is exposed to actinic radiation through a photomask or by direct writing to create a solubility difference between the exposed and unexposed regions. The exposure of the photoresist composition to radiation that is actinic to the composition indicates that the radiation can form a latent image in the photoresist composition. The photomask has optically transparent and optically opaque regions corresponding, respectively, to the regions of the resist layer to be exposed and not exposed by the actinic radiation. The exposure wavelength is typically below 400 nm, and more typically below 300 nm, such as 248 nm (KrF), 193 nm (ArF), or EUV wavelengths (e.g., 13.5 nm). The actinic radiation can be an electron beam (e-beam), typically by direct writing to the photoresist layer. In a preferred aspect, the exposure wavelength is 248 nm, 193 nm, or an EUV wavelength. The exposure energy is typically 3 to 300 mJ / cm 2 , which depends on, for example, the exposure tool and the components of the photosensitive composition.

[0036] After exposing the photoresist layer, post-exposure baking (PEB) is typically carried out. The PEB can be carried out, for example, on a hot plate or in an oven. The PEB is typically carried out at a temperature of 50 °C or higher, more typically in the temperature range of 50 °C to 160 °C.

[0037] Then, the exposed photoresist layer is developed with a suitable developer to selectively remove those areas of the layer that are soluble in the developer, and the remaining insoluble areas form the resulting relief image of the photoresist pattern. In the case of a positive photoresist, the exposed areas of the photoresist layer are removed during development and the unexposed areas are retained. Conversely, for a negative photoresist, the exposed areas of the photoresist layer are retained during development and the unexposed areas are removed. The application of the developer can be accomplished by any suitable method such as those described above for the application of the photoresist composition, where spin coating is typical. The development time is the period during which the soluble areas of the photoresist are effectively removed, and a time of 5 seconds to 60 seconds is typical. Development is typically carried out at room temperature.

[0038] The suitable developer will depend on the material of the photoresist composition and can 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, etc. Suitable organic solvent developers include, for example, those selected from ketones, esters, ethers, hydrocarbons, alcohols, and mixtures thereof.

[0039] Then, the developed substrate can be selectively processed in those areas of the underlying layer 104 that are free of photoresist according to procedures well known in the art, such as by dry etching. Suitable etching processes include, for example, plasma etching such as O2, CF4, or H2 / N2 plasma etching, or combinations thereof. As Figure 1C shown, the result is a patterned underlying layer 104', thereby exposing areas of the underlying metal layer 102 that are in regions not covered by the unpatterned organic underlying layer. The remaining photoresist pattern after etching can then be stripped from the substrate by a known photoresist stripping process, such as by an O2 plasma ashing process.

[0040] Reference Figure 1D, and then an outer coating coating composition is applied over the patterned organic underlayer 104' and the exposed areas of the metal layer 102 on the substrate to form an outer coating 106. The outer coating coating composition comprises a compound and an organic solvent, and the compound comprises a group capable of covalently bonding (crosslinking) with the organic underlayer. The outer coating composition is substantially free of acid generators. Although the outer coating formed from this composition can covalently bond with the underlayer, the outer coating is not self-crosslinkable. This allows a part of the covering layer formed from the composition in contact with the underlayer to crosslink with the underlayer, while other parts of the outer coating remain uncrosslinked. Suitable such compounds include those described above for the underlayer coating composition for thermally crosslinkable polymers and compounds containing one or more crosslinkable heterocyclic groups. To allow covalent bonding with the underlayer while avoiding self-crosslinking of the applied outer coating composition, the outer coating coating composition preferably comprises (i) a compound containing crosslinkable groups selected from, for example, hydroxy-substituted aryl or amine groups, or (ii) a compound containing crosslinkable heterocyclic groups selected from epoxy groups, oxetane groups, aziridine groups, or combinations thereof, but does not contain groups from both (i) and (ii). As described above for the underlayer coating composition, the crosslinkable compound can be a polymer or can be in non-polymeric form, with polymers being typical.

[0041] The crosslinkable compound of the outer coating coating composition preferably comprises one or more groups to increase the hydrophobicity of the compound. Suitable such groups include, for example, (i) aromatic groups substituted by one or more halogen atoms (-F, -Br, -Cl or -I), typically -F, or (ii) substituted or unsubstituted alkyl groups, such as substituted or unsubstituted C 1-10 linear, C 3-10 branched or C 3-10 cyclic alkyl groups, and their preferred substituents are halogen atoms, typically -F. For such hydrophobic groups as part of a crosslinkable polymer, it is preferred to have repeating units of one or both of the following general formulas (3) and (4): wherein: R1 represents H, F, CN, substituted or unsubstituted C 1-10 alkyl, typically 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 of R6 is F or at least partially fluorinated; and R7 represents substituted or unsubstituted linear or branched C 1-20An alkyl group, preferably a fluoroalkyl group; m is an integer from 0 to 5, typically from 1 to 5. It is believed that including such repeating units on the polymer enhances the wet etch resistance of the outer coating to typical aqueous wet etchants that can be used to etch the metal layer 102. Suitable exemplary repeating units having the formulas (3) and (4) include the following:

[0042] The optional repeating units having the formulas (3) and (4) can be present in the crosslinkable polymer in an amount of 1 to 80 mol%, more typically 10 to 60 mol%, based on the total repeating units in the crosslinkable polymer, where the sum of all repeating units of the polymer is 100 mol%.

[0043] In the case of a copolymer, the crosslinkable compound can be a random copolymer, a block copolymer, etc., with random copolymers being typical. Typically, the polymer of the underlayer composition of the present invention will 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 suitably determined by gel permeation chromatography.

[0044] Suitable exemplary thermally crosslinkable polymers for the outer coating composition include the following: where a and b represent the mole percentages of the corresponding repeating units within the polymer, where the total mole percentage of all units in the polymer equals 100 mole %.

[0045] The crosslinkable compound is typically present in the outer coating composition in an amount of 1 to 100 wt%, more typically 1 to 99 wt% or 10 to 90 wt%, based on the total solids of the outer coating composition.

[0046] The outer coating composition can further comprise 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 as described above for the underlayer coating composition. The outer coating composition should be substantially free of crosslinking agents to avoid self-crosslinking of the outer coating.

[0047] The outer coating composition further comprises an organic solvent, which may be a single solvent or a mixture of solvents. Suitable solvents include, for example, one or more of oxyisobutyrates, particularly one or more of methyl 2-hydroxyisobutyrate, 2-hydroxyisobutyric acid, ethyl lactate, or glycol ethers such as 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; solvents having both ether and hydroxyl moieties 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 γ-butyrolactone; or combinations thereof. The solvent of the outer coating composition should be selected such that the underlying layer is substantially insoluble in the outer coating solvent.

[0048] The concentration of the dry components in the outer coating composition will depend on several factors such as the application method and the target film thickness. Typically, the total solids content of the outer coating composition can be from 0.05 to 20 wt% of the total weight of the outer coating composition, preferably from 0.1 to 5 wt% of the outer coating composition.

[0049] The outer coating composition is applied to the substrate at a typical dry layer thickness of about 0.02 to 0.5 μm, preferably about 0.04 to 0.20 μm. The applied outer coating is then cured, resulting in covalent bonding between the crosslinkable groups of the outer coating composition and the organic underlying layer. The curing conditions will vary with the components of the underlying layer 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.

[0050] Reference Figure 1E , an organic-based remover is used to remove the uncrosslinked portion of the outer coating from the substrate, leaving the crosslinked portion 106' of the outer coating with the underlying layer. Suitable removers for those portions of the outer coating material that are not bound 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.

[0051] Reference Figure 1F, Next, a patterned photoresist underlayer and an attached outer coating are used as an etch mask, and the substrate is brought into contact with a wet etchant 108 to remove the exposed regions of the metal layer 102. Suitable wet etchants and conditions are known in the art and will depend on, for example, the specific materials of the metal layer, underlayer, and outer coating. The wet etchant can be, for example, an aqueous acidic or aqueous alkaline solution, where SC-1 (e.g., 5:1:1 H2O:H2O2:NH4OH) and SC-2 (H2O:H2O2:HCl (5:1:1)) are typical.

[0052] As Figure 1G shown, due to the isotropic nature of wet etching, the resulting etched region w of the metal layer exhibits some undercutting of the etch mask. It is believed that the presence of the outer coating provides improved resistance to wet etching and thus reduces the amount of undercutting compared to a process without the outer coating 106. Figure 2A -C shows a process of a related art including an underlayer without using an outer coating as described herein. As Figure 2B -C shows, compared to when using an underlayer with an outer coating as described herein, the wet etched region w' in this no-outer-coating process will exhibit a significantly greater degree of undercutting of the etch mask 104'. This greater extent of undercutting may adversely affect the resulting device structure and electrical characteristics of the final device. As Figure 1H shown, known techniques and materials can be used, such as by oxygen plasma ashing, to remove those portions of the patterned outer coating 106' and underlayer 102' remaining on the substrate after wet etching the metal layer.

[0053] After the patterning described, further processing is performed to form the final semiconductor device. The further processing can include, for example, fabricating semiconductor devices such as memory devices, processor chips (CPUs), graphics chips, optoelectronic chips, LEDs, OLEDs, and other electronic devices.

[0054] The following non-limiting examples illustrate the invention. Examples Polymer Synthesis Polymer P1 (MW of about 11,000) (Aldrich Chemical Co.). Example 1 (Polymer P2 )

[0055] Charge 60.0 g of ethyl lactate into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 90 °C under nitrogen and reflux. Dissolve 40.0 g of 4-hydroxyphenyl methacrylate and 10.34 g of V-601HP initiator (2,2'-azobis(2-methylpropionic acid dimethyl ester)) (FUJIFILM Wako Chemicals) in 60.0 g of cyclohexanone, and feed the prepared mixture solution into the reactor for 180 minutes. After the feeding is completed, maintain the reactor at 90 °C for another 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with heptane / methyl tert-butyl ether (MTBE) (6:4) (×10 excess of the reaction mixture). After the precipitate has settled, remove the solvent by decantation and dry the precipitate in air. Redissolve the obtained white solid precipitate in 120 g of tetrahydrofuran (THF) and precipitate from heptane / MTBE (6:4). After the precipitate has settled, remove the solvent by decantation, and then exchange the precipitate with PGMEA solvent. Example 2 (Polymer P3 )

[0056] In a 3-necked 100 mL round-bottom flask equipped with a temperature control unit, dissolve 30.0 g of o-cresol, 7.023 g of paraformaldehyde, and 0.160 g of methanesulfonic acid in 30.0 g of propylene glycol methyl ether (PGME). Heat the reactor to 120 °C for 5 hours. Dilute the reaction mixture with THF to a 30 wt% solution and precipitate with heptane / MTBE (4:1) (×10 excess of the reaction mixture). After the precipitate has settled, remove the solvent by decantation and dry the precipitate in a vacuum oven at 40 °C for 1 day to form a dry powder. Exchange the dry polymer with PGMEA solvent. Example 3 (Polymer P4 )

[0057] Charge 45.7 g of propylene glycol monomethyl ether acetate (PGMEA) into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 90 °C. Dissolve 22.25 g of 4-hydroxyphenyl methacrylate, 17.75 g of glycidyl methacrylate, and 6.90 g of V-601HP initiator (FUJIFILM Wako Chemicals) in 74.3 g of PGMEA. Feed the mixture into the reactor within 180 minutes. After the feeding is completed, maintain the reactor at 90 °C for another 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with heptane / MTBE (6:4) (×10 excess of the reaction mixture). After the precipitate has settled, remove the solvent by decantation and dry the precipitate in a vacuum oven at 40 °C for 1 day to form a dry powder. Exchange the dry polymer with PGMEA solvent. Example 4 (Polymer P5 )

[0058] 24.1 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. The reactor was heated to 90 °C. 40.0 g of glycidyl methacrylate and 2.59 g of V-601HP initiator (FUJIFILM Wako Pure Chemical Corporation) were dissolved in 74.3 g of PGMEA, and the mixture was fed into the reactor over 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 with THF to a 25 wt% solution and precipitated with MTBE (×10 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. Example 5 (Polymer P6 )

[0059] 20.0 g of PGMEA was charged into a 3-necked 250 ml round-bottom flask equipped with a temperature controller 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 Pure Chemical Corporation) were dissolved in 40.0 g of PGMEA. The mixture was fed into the reactor over 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 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 stir bar, 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. The solution was then heated to 65 °C with stirring for 5 hours. The solvent was evaporated on a rotary evaporator, and the resulting product was dissolved in ethyl acetate and washed with deionized water. The organic layer was separated and the solvent was removed on a rotary evaporator. The polymer was solvent-exchanged with PGMEA. Example 6 (Polymer P7 )

[0060] 20.0 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 3-necked 250 ml round-bottom flask equipped with a temperature controller 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 Pure Chemical Corporation) were dissolved in 40.0 g of PGMEA. The mixture was fed into the reactor over 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 under natural stirring. The reaction mixture was precipitated with MeOH (×10 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 stir bar, 20.0 g of the dry powder and 0.456 g of 25% NaOMe in MeOH were dissolved in 46.67 g of MeOH. The solution was then heated to 65 °C with stirring for 5 hours. The solvent was evaporated on a rotary evaporator, and the resulting product was dissolved in ethyl acetate and washed with deionized water. The organic layer was separated and the solvent was removed on a rotary evaporator. The polymer was solvent-exchanged with PGMEA. Example 7 (Polymer P8)

[0061] 45.7 g of propylene glycol monomethyl ether acetate (PGMEA) was charged into a 3-necked 250 ml round-bottom flask equipped with a temperature controller 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 Pure Chemical Corporation) were dissolved in 74.3 g of PGMEA. The mixture was fed into the reactor over 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 (1:1) (×10 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 solvent-exchanged with PGMEA. Example 8 (Polymer P9)

[0062] Charge 20.0 g of PGMEA into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 75 °C. Dissolve 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 Pure Chemical Corporation) in 40.0 g of PGMEA. Feed the mixture into the reactor over 180 minutes. After the feeding is complete, maintain the reactor at 90 °C for an additional 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with MeOH (×10 excess of the reaction mixture). After the precipitate has settled, remove the solvent by filtration, and dry the precipitate 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 stir bar, dissolve 20.0 g of the dry powder and 0.262 g of 25% NaOMe in MeOH in 46.67 g of MeOH. Heat the solution to 65 °C with stirring for 5 hours. After evaporating the solvent on a rotary evaporator, dissolve the resulting product in ethyl acetate and wash with deionized water. Separate the organic layer and remove the solvent with a rotary evaporator. Exchange the polymer solvent with PGMEA. Example 9 (Polymer P10)

[0063] Charge 45.7 g of PGMEA into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 90 °C. Dissolve 21.51 g of glycidyl methacrylate, 18.49 g of 4-fluorostyrene, and 8.36 g of V-601HP initiator (FUJIFILM Wako Pure Chemical Corporation) in 74.3 g of PGMEA. Feed the mixture into the reactor over 180 minutes. After the feeding is complete, maintain the reactor at 90 °C for an additional 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with isopropanol (IPA) (×10 excess of the reaction mixture). After the precipitate has settled, remove the solvent by filtration, and dry the precipitate in a vacuum oven at 40 °C for 1 day. Example 10 (Polymer P11)

[0064] Charge 45.7 g of PGMEA into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 90 °C. Dissolve 20.0 g of glycidyl methacrylate, 20.0 g of n-butyl methacrylate, and 7.77 g of V-601HP initiator (FUJIFILM Wako Pure Chemical Corporation) in 74.3 g of PGMEA. Feed the mixture into the reactor over 180 minutes. After the feeding is complete, maintain the reactor at 90 °C for an additional 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with IPA (10× excess of the reaction mixture). After the precipitate has settled, remove the solvent by filtration, and dry the precipitate in a vacuum oven at 40 °C for 1 day. Example 11 (Polymer P12)

[0065] Charge 45.7 g of PGMEA into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 90 °C. Dissolve 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 Pure Chemical Corporation) in 74.3 g of PGMEA. Feed the mixture into the reactor over 180 minutes. After the feeding is complete, maintain the reactor at 90 °C for an additional 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with heptane (10× excess of the reaction mixture). After the precipitate has settled, remove the solvent by filtration, and dry the precipitate in a vacuum oven at 40 °C for 1 day. Example 12 (Polymer P13)

[0066] Charge 45.7 g of PGMEA into a 3-necked 250 ml round-bottom flask equipped with a temperature controller unit. Heat the reactor to 90 °C. Dissolve 22.60 g of 2-hydroxyethyl methacrylate, 17.40 g of methyl methacrylate, and 9.60 g of V-601HP initiator (FUJIFILM Wako Pure Chemical Corporation) in 74.3 g of PGMEA. Feed the mixture into the reactor over 180 minutes. After the feeding is complete, maintain the reactor at 90 °C for an additional 60 minutes. After the reaction, cool the reactor to room temperature with stirring. Precipitate the reaction mixture with heptane / MTBE (4:1) (10× excess of the reaction mixture). After the precipitate has settled, remove the solvent by decantation. Then dry the precipitate in a vacuum oven at 40 °C for 1 day. Example 13 (Polymer P14)

[0067] 45.7 g of PGMEA was charged into a 3-necked 250 ml round-bottom flask equipped with a temperature controller 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 Pure Chemical Corporation) were dissolved in 74.3 g of PGMEA. The mixture was fed into the reactor within 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 excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation. Then the precipitate was dried in a vacuum oven at 40 °C for 1 day. Example 14 (Polymer P15)

[0068] 45.7 g of PGMEA was charged into a 3-necked 250 ml round-bottom flask equipped with a temperature controller 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 Pure Chemical Corporation) were dissolved in 74.3 g of PGMEA. The mixture was fed into the reactor within 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 excess of the reaction mixture). After the precipitate had settled, the solvent was removed by decantation. Then the precipitate was dried in a vacuum oven at 40 °C for 1 day. Preparation of the bottom layer composition Examples 15 - 20

[0069] The bottom layer composition (UC) was prepared by dissolving the solid components in the solvent using the materials and amounts listed 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. Table 1 S1 = methyl 2-hydroxyisobutyrate (HBM); S2 = PGMEA; all amounts provided are in grams; the polymer content reflects only the solid, with any solvent portion of the polymer reflected in the solvent content. Preparation of the outer coating composition Examples 21 - 30

[0070] The overcoat composition (OC) is prepared by dissolving the solid components in a solvent using the materials and amounts listed in Table 2. The mixture is shaken on a mechanical shaker for at least 4 hours. The resulting mixture is filtered through a PTFE 0.45 μm membrane filter. Table 2 S2 = PGMEA; all amounts provided are in grams; the polymer content reflects only the solids, with any solvent portion of the polymer reflected in the solvent content. Solvent-resistant peelability / strippability evaluation Examples 31 - 46

[0071] The underlayer composition or overcoat composition as described above is spin-coated onto the corresponding 200-mm silicon wafers on an ACT-8 Clean Track (Tokyo Electron Co.) at 1500 rpm for 60 seconds and then baked on a hot plate at 220 °C for 60 seconds to form an underlayer or overcoat film. Then, a Therma-Wave OptiProbe TM 5250 metrology tool is used to measure the film thickness. Then, 30 mL of PGME / PGMEA (70 / 30 wt / wt) remover is applied to the film on the Clean Track for 90 seconds. The wafers are spun dry at 4000 rpm for 60 seconds and soft baked on a hot plate at 110 °C for 60 seconds. The thickness of each film is measured again to determine the amount of film thickness loss. The change in film thickness before and after the application of the remover (i.e., the thickness of the film removed by the remover) is calculated using Equation 1 below: ΔFT = FT i - FT f (1) where FT i is the initial film thickness of the underlayer or overcoat composition (before the application of the remover), and FT f is the final film thickness (after the application of the remover). The results are shown in Table 3. Table 3 As can be seen from Table 3, each of the underlayer compositions UC-1 to UC-6 exhibits negligible peel loss with the organic remover, indicating the complete crosslinking of the composition. Each of the overcoat compositions OC-1 to OC-10 is shown to be substantially completely removed by the remover. Interlayer crosslinking evaluation Examples 47 - 61

[0072] Spin coat the bottom layer compositions listed in Table 4 onto the corresponding 200-mm silicon wafers on an ACT-8 CleanTrack (Tokyo Electron Limited) at 1500 rpm for 60 seconds. Then bake the wafers on a hot plate at 220 °C for 60 seconds to form a cured bottom layer 150 nm thick as measured by a Therma-Wave OptiProbe TM 5250 metrology tool. Spin coat the topcoat compositions listed in Table 4 on top of the bottom layer at 1500 rpm for 60 seconds. Bake the wafer at 220 °C for 60 seconds and then cool to room temperature. Then apply 30 mL of a PGME / PGMEA (70 / 30 wt / wt) remover to the film on the Clean Track for 90 seconds. Spin dry the wafer at 4000 rpm for 60 seconds and soft bake on a hot plate at 110 °C for 60 seconds. Measure the thickness of the resulting bilayer film. Calculate the attached topcoat thickness (FT oc ) using Equation 2 below as the difference between the final thickness of the bilayer film (FT f ) and the initial thickness of the bottom layer film (FT i ), and the results are shown in Table 4: FT oc = FT f - FT i (2) Table 4 As can be seen from Table 4, the bilayer stacks of Comparative Examples 52 and 59 - 61 exhibit a thickness after solvent stripping equal to that of the bottom layer, indicating that not a significant amount of the topcoat remains attached to the bottom layer, believed to be due to the absence of interlayer crosslinking between the bottom layer and the topcoat. In contrast, the bilayer stacks of Examples 47 - 51 and 53 - 58 according to the present invention exhibit a thickness after solvent stripping greater than that of the bottom layer. This indicates that interlayer crosslinking has occurred between the bottom layer and the topcoat film. Wet Etch Resistance Evaluation Examples 62 - 81 Titanium nitride (TiN) was deposited on a 200-mm silicon wafer by atomic layer deposition (ALD) using tetramethyl(dimethylamino)titanium (TDMAT) as a precursor on a Nano-ALD2000 ALD system (Integrated Process Systems Ltd.) at a total pressure of 10 SCCM and 0.34 Torr. The deposition cycle was repeated to achieve a target thickness of 10 nm. Before spin-coating the bottom and topcoat compositions listed in Table 5, the deposited wafers were cut into specimens (4 cm × 4 cm pieces), where coating, curing, and film thickness measurement were performed as described above for interlayer crosslinking evaluation using a J.A. Woollam M-2000 ellipsometer for thickness measurement. The resulting multilayer film stack was immersed in an SC-1 wet etching solution for evaluating the wet etching resistance. The etching solution was prepared by mixing 35 wt% ammonium hydroxide and 30 wt% hydrogen peroxide (NH4OH:H2O2:H2O = 1:1:10) at a bath temperature of 50 °C. The tolerance of the film to the wet etchant was evaluated by measuring the endurance time (t 结束 ) until visually observing film damage. The results are shown in Table 5. Table 5 Based on the results in Table 5, compared to using only the bottom layer (Comparative Examples 62 - 66) or combinations of the bottom layer and topcoat that do not exhibit interlayer crosslinking (Comparative Examples 72 and 79 - 81), using a topcoat capable of crosslinking with the bottom layer resulted in improved wet etching resistance of the bottom layer film.

Claims

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

2. The method of claim 1, further comprising (i) removing the patterned organic primer layer and the cross-linked portion of the overcoat composition from the substrate.

3. The method of 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 cross-linkable compound of the organic undercoat coating composition and the cross-linkable 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 undercoat coating composition and the crosslinkable compound of the overcoat coating composition independently include a hydroxy-substituted aryl or amine group.

6. The method according to any one of claims 1 or 5, wherein: The organic primer coating composition includes a cross-linkable heterocyclic group.

7. The method of claim 6, wherein: The cross-linkable heterocyclic group is an epoxy group, an oxetane group, or an aziridine group.

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

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