Metallization Method

Abstract

To provide a metallization method.SOLUTION: There is disclosed a metallization method, comprising (a) providing a photoresist layer on a first surface of a substrate, wherein the photoresist layer is formed from a photoresist composition comprising: a polymer comprising acid-labile groups; a photoacid generator; an organic phosphonic acid; and a solvent; (b) pattern-wise exposing the photoresist layer to activating radiation; (c) developing the exposed photoresist layer with a basic developer to form a photoresist pattern; and (d) after forming the photoresist pattern, plating a metal on the first surface of the substrate using the photoresist pattern as a plating mask.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present disclosure relates to a patterning process for manufacturing semiconductors. In particular, the present disclosure relates to a patterning process for manufacturing semiconductors that prevents the development of a tailing profile in a photoresist pattern. [Background technology]

[0002] Mobile devices, devices that are part of the Internet of Things (IoT), and wearable electronics are becoming smaller, lighter, and thinner devices that, despite their miniaturization, use large amounts of memory and perform increasingly large amounts of computation.

[0003] The manufacturing and packaging of these electronic devices plays a significant role in size reduction. For example, flip-chip packaging methods have been used to increase the density of I / O (input / output) connections between devices, especially for microprocessing units (MPUs) and dynamic random access memory (DRAM) semiconductor chips.

[0004] For example, metal pillar bumps, such as copper pillar bumps, are often used as flip-chip interconnects for use in electronics and optoelectronic packaging, such as flip-chip packaging of CPU and GPU integrated circuits (chips), laser diodes, and semiconductor optical amplifiers (SOAs). Metal pillar bumps provide beneficial contact resistance, high-density connections, metal migration resistance, and heat dissipation properties. Metal line patterns may also be used, for example, in redistribution layers (RDLs) to provide electrical connections between two components.

[0005] Electroplating is used to fabricate metal pillar bump arrays and line patterns. After coating a photoresist layer on the copper film surface, a mask pattern is created using photolithography. Metal structures are then formed on the metal surface by electroplating in the open areas of the mask pattern. The photoresist is then removed, and the metal layer previously covered by the resist is then removed by etching.

[0006] One approach to preparing plating mask patterns is the use of thick photoresist layers to address the need for thicker and narrower pattern sizes for the further increase in I / O and device density. Chemically amplified photoresists may be a suitable option for achieving the faster sensitivity and improved transparency desired for higher resolution patterns. Such resist compositions include a polymer with acid-labile groups, a photoacid generator (PAG), and a solvent. However, when chemically amplified resists are formed on metal layers, such as copper layers, tailing profile problems have been observed due to loss of photoacid present at the interface between the metal surface and the resist.

[0007] The footing of the resist pattern results in an undercut profile of the plating pattern, which can promote collapse of the plating pattern during downstream processing. Therefore, it is desirable to eliminate footing of the photoresist pattern used as a plating mask and provide an undercut resist pattern profile to overcome collapse of the plating pattern. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 6,057,083 [Patent Document 2] U.S. Patent No. 6,136,501 [Patent Document 3] U.S. Patent No. 8,206,886 [Patent Document 4] European Patent Application Publication No. 01008913A1 [Patent Document 5] European Patent Application Publication No. 00930542A1 [Patent Document 6] US Patent Application Publication No. 2012 / 0064456A1 [Patent Document 7] U.S. Patent No. 6,042,997 [Patent Document 8] U.S. Patent No. 5,492,793 [Patent Document 9] U.S. Patent No. 5,929,176 [Patent Document 10] U.S. Patent No. 6,090,526 [Patent Document 11] U.S. Patent No. 6,692,888 [Patent Document 12] U.S. Patent No. 6,680,159 [Patent Document 13] U.S. Patent No. 5,843,624 [Patent Document 14] U.S. Patent No. 6,048,664 [Patent Document 15] U.S. Patent No. 6,048,662 [Patent Document 16] International Publication No. 0186353A1 Brochure [Patent Document 17] U.S. Patent No. 6,306,554 [Patent Document 18] U.S. Patent No. 7,244,542 Summary of the Invention [Means for solving the problem]

[0009] Disclosed herein is a metallization method comprising: (a) providing a photoresist layer on a first surface of a substrate, the photoresist layer being formed from a photoresist composition comprising: a polymer comprising acid-labile groups; a photoacid generator; an organic phosphonic acid; and a solvent; (b) patternwise exposing the photoresist layer to activating radiation; (c) developing the exposed photoresist layer with a basic developer to form a photoresist pattern; and (d) after forming the photoresist pattern, plating a metal onto the first surface of the substrate using the photoresist pattern as a plating mask. [Brief explanation of the drawings]

[0010] [Figure 1A] 1 illustrates an exemplary embodiment of a substrate on which a first metal layer is disposed. [Figure 1B] 1A-1C illustrate an exemplary embodiment of depositing a photoresist layer onto a first metal layer and photopatterning the photoresist layer and the first metal layer. [Figure 1C] 1 illustrates an exemplary embodiment of developing a photoresist layer. [Figure 1D] 1 is an exemplary depiction of the deposition (by plating) of metal on a metal layer. [Figure 1E] FIG. 10 shows the plated metal structure remaining after removing the remaining photoresist layer. [Figure 2-7] 10 shows Tables 5 to 10, respectively, containing data from the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] As used herein, the terms "a," "an," and "the" do not denote limitations of quantity and should be construed to include both the singular and the plural unless otherwise indicated herein or clearly contradicted by context. "Or" means "and / or" unless otherwise stated.

[0012] As used herein, "acid labile group" refers to a group whose bond is cleaved by acid catalysis, optionally and typically by thermal treatment, resulting in a polar group, such as a carboxylic acid or alcohol group, formed on the polymer; optionally and typically, the moiety connected to the cleaved bond is cleaved from the polymer. Such acids are typically photogenerated acids, in which bond cleavage occurs during post-exposure baking. Suitable acid labile groups include, for example, tertiary alkyl ester groups, secondary or tertiary aryl ester groups, secondary or tertiary ester groups having a combination of alkyl and aryl groups, tertiary alkoxy groups, acetal groups, or ketal groups. Acid labile groups are also commonly referred to in the art as "acid cleavable groups," "acid cleavable protecting groups," "acid labile protecting groups," "acid leaving groups," "acid decomposable groups," and "acid-sensitive groups."

[0013] Disclosed herein is a method for manufacturing a semiconductor device that suppresses the occurrence of footing in a photoresist layer during the manufacturing process. Footing causes undercutting of the plating pattern, which can promote the collapse of the plating pattern during further processing and reliability testing. Therefore, it is desirable to eliminate or suppress footing of the plating pattern.

[0014] A photoresist composition containing a polymer, a non-ionic photoacid generator, and a phosphonic acid is disposed on a substrate to form a photoresist layer. The photoresist layer is patternwise exposed to activating radiation. The exposed photoresist layer is then developed with a basic developer, thereby removing portions of the photoresist layer to form a relief pattern. After forming the relief pattern, a metal may be plated on the first surface of the substrate.

[0015] 1A-1E illustrate a method for forming a plating pattern on a substrate. FIG. 1A shows a substrate 100 having a first metal layer 102 disposed thereon. FIG. 1B illustrates the coating of a photoresist layer 106 on the metal layer 102 and subsequent exposure of the photoresist layer 106 to light. The photoresist layer 106 includes a photoacid generator and a polymer containing acid-labile groups. After coating the photoresist layer 106, the photoresist layer 106 is patternwise exposed to activating radiation 108 through a photomask 110 having optically opaque and optically transparent regions. UV light having a wavelength between 10 nanometers and 400 nanometers may be used in photopatterning.

[0016] Figure 1C shows development of the exposed portions of the photoresist layer 106. The exposed portions of the photoresist layer 106 are removed by development, as seen in Figure 1C. After metal plating, as seen in Figure 1D, the remaining portions of the photoresist layer can be removed (stripped) from the substrate, leaving behind plated metal structures 112. Figure 1E shows the plated metal structures 112 remaining after removal of the remaining photoresist layer.

[0017] Next, the various layers mentioned above (shown in FIGS. 1A to 1E) and their respective compositions will be described in detail.

[0018] substrate Examples of substrates include, but are not limited to, silicon wafers, glass substrates, and plastic substrates, optionally including one or more layers or features formed thereon. A preferred substrate is a silicon wafer.

[0019] metal layer FIG. 1A shows a substrate 100 having a first metal layer 102 disposed thereon. An optional second metal layer (not shown) may be disposed on the first metal layer 102. The first metal layer may be made of, for example, titanium, silver, aluminum, gold, copper, or an alloy thereof. In an exemplary embodiment, the first metal layer 102 comprises titanium or copper. When a second metal layer is disposed on the first metal layer, the first metal layer preferably comprises titanium. The first metal layer can be formed using known methods, for example, by chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), or physical vapor deposition (PVD) techniques, with sputtering and plating being typical. The thickness of the first metal layer 102 is typically between 10 nm and 500 nm.

[0020] The optional second metal layer comprises tantalum, titanium, copper, silver, aluminum, gold, or alloys thereof. The second metal layer is chemically distinct from the first metal layer 102. In an exemplary embodiment, the second metal layer comprises copper. The second metal layer may be disposed on the surface of the first metal layer via chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), or a combination thereof. The thickness of the second metal layer is typically between 10 nm and 500 nm.

[0021] Photoresist layer 1B shows deposition of a photoresist layer 106 on the first metal layer 102. The photoresist layer 106 includes a polymer, a photoacid generator, a phosphonic acid, and a base quencher. The polymer includes a first repeat unit including an acid labile group. In one embodiment, the polymer includes a second repeat unit including a vinyl aromatic group.

[0022] Acid labile groups are chemical moieties that undergo deprotection in the presence of acid. Deprotection of some acid labile groups used in the examples is achieved by heat. Acetal protecting groups are easily deprotected at room temperature. The polymer of the photoresist composition undergoes a change in solubility in the developer as a result of reaction with the acid generated from the photoacid generator (contained in the photoresist composition) after soft baking, exposure to activating radiation, and post-exposure baking. This is due to photoacid-induced cleavage of the acid labile group, which causes a change in the polarity of the polymer. The acid labile group can be selected from, for example, tertiary alkyl carbonates, tertiary alkyl esters, tertiary alkyl ethers, acetals, and ketals. Preferably, the acid labile group is an ester group containing a tertiary acyclic alkyl carbon or a tertiary alicyclic carbon covalently bonded to the carboxyl oxygen of the ester of the polymer. Cleavage of such an acid labile group results in the formation of a carboxylic acid group.

[0023] In one embodiment, the polymer comprising acid labile groups comprises polymerized units having the structure shown in formula (1): [ka] In the formula, Z is selected from a hydrogen atom, a substituted or unsubstituted C1-C4 alkyl, a substituted or unsubstituted C1-C4 fluoroalkyl, or a cyano group; Z 1 is a non-hydrogen substituent containing an acid labile group, the cleavage of which forms a carboxylic acid on the polymer.

[0024] In one embodiment, the acid labile groups that upon degradation form carboxylic acid groups on the polymer preferably have the formula —C(O)OC(R 1 )3 or a tertiary ester group of the formula C(O)OC(R 2 )2OR 3 where: R 1 are each independently linear C 1~20 Alkyl, branched C 3~20 Alkyl, monocyclic or polycyclic C 3~20 Cycloalkyl, linear C 2~20 Alkenyl, branched C 3~20Alkenyl, monocyclic or polycyclic C 3~20 Cycloalkenyl, monocyclic or polycyclic C 6~20 Aryl, or monocyclic or polycyclic C 2~20 Heteroaryl, preferably linear C 1~6 Alkyl, branched C 3~6 Alkyl, or monocyclic or polycyclic C 3~10 cycloalkyl, each of which is substituted or unsubstituted; and each R 1 optionally includes as part of its structure one or more groups selected from -O-, -C(O)-, -C(O)-O-, or -S-, and any two R 1 The groups together optionally form a ring; R 2 are independently hydrogen, fluorine, linear C 1~20 Alkyl, branched C 3~20 Alkyl, monocyclic or polycyclic C 3~20 Cycloalkyl, linear C 2~20 Alkenyl, branched C 3~20 Alkenyl, monocyclic or polycyclic C 3~20 Cycloalkenyl, monocyclic or polycyclic C 6~20 Aryl, or monocyclic or polycyclic C 2~20 Heteroaryl, preferably hydrogen, linear C 1~6 Alkyl, branched C 3~6 Alkyl, or monocyclic or polycyclic C 3~10 cycloalkyl, each of which is substituted or unsubstituted, and each R 2 optionally includes as part of its structure one or more groups selected from -O-, -C(O)-, -C(O)-O-, or -S-, and R 2 The groups together optionally form a ring; R 3 is a linear C 1~20 Alkyl, branched C 3~20 Alkyl, monocyclic or polycyclic C 3~20 Cycloalkyl, linear C 2~20 Alkenyl, branched C 3~20 Alkenyl, monocyclic or polycyclic C 3~20 Cycloalkenyl, monocyclic or polycyclic C 6~20 Aryl, or monocyclic or polycyclic C2~20 Heteroaryl, preferably linear C 1~6 Alkyl, branched C 3~6 Alkyl, or monocyclic or polycyclic C 3~10 cycloalkyl, each of which is substituted or unsubstituted; R 3 optionally includes as part of its structure one or more groups selected from -O-, C(O)-, -C(O)-O-, or -S-, and one R 2 is R 3 together optionally forming a ring. Such monomers are typically vinyl aromatic, (meth)acrylate, or norbornyl monomers.

[0025] Suitable acid-labile group-containing units include, for example, acid-labile (alkyl)acrylate units such as t-butyl (meth)acrylate, 1-methylcyclopentyl (meth)acrylate, 1-ethylcyclopentyl (meth)acrylate, 1-isopropylcyclopentyl (meth)acrylate, 1-propylcyclopentyl (meth)acrylate, 1-methylcyclohexyl (meth)acrylate, 1-ethylcyclohexyl (meth)acrylate, 1-isopropylcyclohexyl (meth)acrylate, 1-propylcyclohexyl (meth)acrylate, methyladamantyl (meth)acrylate, ethyladamantyl (meth)acrylate, and the like, as well as other cyclic, such as alicyclic, and acyclic (alkyl)acrylates.

[0026] Acetal and ketal acid-labile groups can bond to an oxygen atom by replacing a hydrogen atom at the end of an alkali-soluble group such as a carboxyl group. When acid is generated, the bond between the acetal or ketal group and the oxygen atom to which the acetal-type acid-dissociable, dissolution-inhibiting group is bonded is cleaved by the acid. Examples of such acid-labile groups are described in, for example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5. Acetal and ketal groups as part of a sugar derivative structure, which form a hydroxyl group upon cleavage, are also suitable, as described in, for example, Patent Document 6.

[0027] Suitable polymers include, for example, phenolic resins containing acid-labile groups. Particularly preferred resins in this category include: (i) polymers containing polymerized units of vinylphenols and the above-mentioned acid-labile (alkyl)acrylates, such as those described in Patent Document 7 and Patent Document 8; (ii) polymers containing polymerized units of vinylphenols, optionally substituted vinylphenyls (e.g., styrene) that do not contain hydroxy or carboxy ring substituents, and the above-mentioned acid-labile (alkyl)acrylates, such as those described in Patent Document 7; (iii) polymers containing repeating units containing photoacid-reactive acetal or ketal moieties and optional aromatic repeating units such as phenyl or phenol groups, such as those described in Patent Document 9 and Patent Document 10; and blends of (i) and / or (ii) and / or (iii). Such polymers are useful, for example, for imaging at wavelengths above 200 nm, for example, 248 nm and 365 nm.

[0028] Suitable polymers include those useful for imaging at certain sub-200 nm wavelengths, such as 193 nm, such as those disclosed in U.S. Patent Nos. 5,629,999, 5,729,143, 5,739,152, and 5,823,163. For imaging at 193 nm wavelengths, the polymer is preferably substantially free (e.g., less than 15 mole %), and preferably completely free of phenyl, benzyl, or other aromatic groups, as such groups are highly absorbing of radiation.

[0029] Other suitable polymers for use in photoresist compositions include, for example, those containing polymerized units of non-aromatic cyclic olefins (endocyclic double bonds), such as optionally substituted norbornenes, such as the polymers described in U.S. Patent Nos. 5,629,999 and 5,729,999. Still other suitable polymers for use in photoresist compositions include polymers containing polymerized anhydride units, particularly polymerized maleic anhydride and / or itaconic anhydride units, such as those disclosed in U.S. Patent Nos. 5,629,999 and 5,729,999.

[0030] Polymers containing repeating units containing heteroatoms, particularly oxygen and / or sulfur (but other than anhydrides, i.e., the units do not contain keto ring atoms), are also suitable for use in photoresist compositions. Heteroalicyclic units can be fused to the polymer backbone and can include fused carbon alicyclic units, such as those provided by polymerization of norbornene groups, and / or anhydride units, such as those provided by polymerization of maleic anhydride or itaconic anhydride. Such polymers are disclosed in U.S. Patent No. 5,629,994 and U.S. Patent No. 5,629,994. Other suitable heteroatom-containing polymers include polymers containing polymerized carbocyclic aryl units substituted with one or more heteroatom- (e.g., oxygen- or sulfur-) containing groups, such as hydroxynaphthyl groups, as disclosed in U.S. Patent No. 5,629,994.

[0031] The polymer may further comprise units containing a lactone moiety to control the dissolution rate of the polymer and the photoresist composition. Monomers suitable for use in polymers containing lactone moieties include, for example: [ka]

[0032] In one embodiment, the polymer further comprises units that typically include polar groups, which enhance the etch resistance of the polymer and the photoresist composition and provide an additional means of controlling the dissolution rate of the polymer and the photoresist composition. Monomers for forming such units include, for example: [ka]

[0033] The polymer may contain one or more additional units of the types described above. Typically, the additional units of the polymer contain the same or similar polymerizable groups as those used in the monomers used to form the other units of the polymer, but may also contain other, different polymerizable groups in the same polymer backbone.

[0034] The polymer may also include one or more repeat units derived from the polymerization of a vinyl aromatic monomer. An exemplary vinyl aromatic monomer is styrene. In one embodiment, the polymer derived from the vinyl aromatic monomer has the following formula (2): [ka] having the structure shown in In the formula, a is 1 to 5, and Z 2 is hydrogen or an alkyl group having 1 to 5 carbon atoms. In a preferred embodiment, a is 1 and Z 2 is hydrogen. The vinyl aromatic monomer preferably has a hydroxyl group in the para position on the aryl ring. A preferred vinyl aromatic polymer is poly(p-hydroxystyrene) (abbreviated as PHS).

[0035] In one embodiment, the polymer for use in the photoresist composition has the following formula (3): [ka] may have the structure shown in In the formula, Z is a hydrogen atom or a methyl group, and Z 1 is a non-hydrogen substituent that provides the acid labile moiety detailed above in Formula (1). In one embodiment, m+n equals 100 mole percent (mol %). In one embodiment, m is 10-80 mol %, preferably 20-70 mol %, and n is 20-90 mol %, preferably 25-80 mol %, preferably 30-40 mol %, based on all polymerized units present in the polymer. In one embodiment, the molar ratio of n to m is 0.7-9.

[0036] When the polymer includes a third repeat unit (different from the first repeat unit and the second repeat unit), the third repeat unit may be present in the polymer in an amount of 15 to 35 mol %, preferably 20 to 30 mol %, based on all polymerized units present in the polymer. The third repeat unit may be present in the polymer in an amount of 15 to 35 mol %, preferably 20 to 30 mol %, based on all polymerized units present in the polymer.

[0037] Exemplary polymers include, but are not limited to, the following: [ka]

[0038] Other exemplary polymers that can be used in the photoresist composition include, for example, [ka] where a+b+c, d+e+f+g, and h+i equal 100 mole % based on all polymerized units present in the polymer.

[0039] Polymers suitable for use in photoresist compositions are commercially available or can be readily made by one skilled in the art, and are present in the photoresist composition in an amount sufficient to render an exposed coating layer of the photoresist developable in a suitable developer.

[0040] Typically, the polymer is present in the photoresist composition in an amount of 70 to 100 weight percent based on the total solids content of the photoresist composition. w is typically less than 100,000, e.g., 4000 to 100,000, more typically 4000 to 20,000 grams per mole (g / mol), as measured by gel permeation chromatography using polystyrene standards. Blends of two or more of the above polymers can be suitably used in the photoresist compositions of the invention.

[0041] The photoresist composition includes a non-ionic photoacid generator. In one embodiment, the photoresist composition may optionally include an ionic photoacid generator. It is desirable to use a photoacid generator that generates a photoacid via Norrish-I type cleavage. The Norrish-I type reaction is the photochemical cleavage or homolysis of aldehydes and ketones into two free radical intermediates. The carbonyl group accepts a photon and is excited to a photochemical singlet state. In one embodiment, the photoacid generator is represented by formula (4): [ka] having the structure shown in In the formula (4), R4 is a hydrogen atom, a substituted or unsubstituted linear or branched C1-C 14 R5 is an alkyl group, a substituted heterocyclic group, or a halogen atom; R5 is a substituted or unsubstituted alkyl group having 1 to 18 carbon atoms; a halogen atom, or an aryl group having 6 to 20 unsubstituted carbon atoms.

[0042] Examples of suitable photoacid generators are N-hydroxynaphthalimide trifluoromethanesulfonate (NHNI-TF), N-hydroxynaphthalimide perfluoro-1-butanesulfonate (NHNI-PFBS), N-hydroxynaphthalimide camphor-10-sulfonate, N-hydroxynaphthalimide 2-trifluoromethylphenylsulfonate, N-hydroxy-5-norbornene-2,3-dicarboximide perfluoro-1-butanesulfonate, N-(trifluoromethylsulfonyloxy)phthalimide, N-hydroxysuccinimide perfluorobutanesulfonate or benzeneacetonitrile, 2-methyl-α-[2-[[(propylsulfonyl)oxy]imino]-3(2H)-thienylidene] (commercially available as IRGACURE PAG 103). In a preferred embodiment, the photoacid generator is represented by formula (4a) or (4b) shown below: [ka] The structure may be one or more of:

[0043] The photoacid generator is present in the photoresist composition in an amount of 0.2 to 15 wt. %, more typically 0.3 to 5 wt. %, and more preferably 0.5 to 2 wt. %, based on the total solids content of the photoresist composition. Minimizing the photoacid generator loading also minimizes the UV transparency of the photoresist, which increases the UV transparency of the photoresist layer. Then, sufficient UV exposure can be applied to penetrate the photoresist layer and reach the UV sensitizer in the underlying layer.

[0044] The photoresist composition includes a phosphonic acid that facilitates reducing tailing during semiconductor manufacturing. The phosphonic acid has the structure shown in formula (5): RPO(OH)2(5), where R is a substituted or unsubstituted aliphatic, alicyclic, or aromatic group bonded directly to the phosphorus atom. The R group is not bonded to the phosphorus atom through an oxygen atom. When R is a substituted or unsubstituted aliphatic group, it can be linear or branched. In one embodiment, R can be an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an arylalkyl group, or a combination thereof.

[0045] In one embodiment, the phosphonic acid is represented by the following formula (6): [ka] having the structure shown in In the formula, R is as defined above.

[0046] Examples of aliphatic phosphonic acids include C1 to C6 butylphosphonic acid, pentylphosphonic acid, hexylphosphonic acid, octylphosphonic acid, n-decylphosphonic acid, n-dodecylphosphonic acid, n-hexadecylphosphonic acid, n-hexylphosphonic acid, n-octadecylphosphonic acid, n-octylphosphonic acid, and n-tetradecylphosphonic acid. 18normal alkyl phosphonic acid, or a combination thereof.

[0047] Examples of aromatic phosphonic acids include phenylphosphonic acid, benzylphosphonic acid, (4-aminobenzyl)phosphonic acid, (4-aminophenyl)phosphonic acid, (4-hydroxyphenyl)phosphonic acid, benzhydrylphosphonic acid, (2-phenylethyl)phosphonic acid, 4-methoxyphenylphosphonic acid, (pyridin-3-ylmethyl)phosphonic acid, etc., or combinations thereof. In a preferred embodiment, the phosphonic acid is phenylphosphonic acid.

[0048] In one embodiment, the phosphonic acid is present in the photoresist composition in an amount of 0.01 to 0.50, preferably 0.05 to 0.20 parts by weight per 100 parts of acid-labile polymer. If the amount of phosphonic acid in the photoresist composition is less than 0.01 parts by weight per 100 parts of acid-labile polymer, footing in the photoresist layer is not minimized. If the amount of phosphonic acid in the photoresist composition is more than 0.20 parts by weight per 100 parts of acid-labile polymer, the pattern in the photoresist layer tends to collapse due to the presence of narrow footing.

[0049] In addition to phosphonic acids, other acids such as phosphoric acids and phosphates can also be added to the photoresist composition.

[0050] The photoresist composition also contains a base quencher, which improves the resolution of the developed resist relief image. The base quencher is preferably a tertiary amine compound added in an amount effective to provide a pKa of the photoresist composition of less than 7. In one embodiment, the base quencher is a tertiary amine in which the nitrogen atom is not a member of an unsaturated heterocyclic compound or is not double-bonded to another atom.

[0051] Examples of preferred amine compounds that can be used as base quenchers include 2,8-dimethyl-6H,12H-5,11methanodibenzo[b,f][1,5]diazocine (Tröger's base), ethyl-3-(morpholino)propionate, 4-(p-tolyl)morpholine, or combinations thereof.

[0052] In one embodiment, other base quenchers such as amides, pyridines, azoles, primary and secondary amines, etc. are not used in the photoresist compositions of the present invention. Furthermore, strong amines that increase the pKa of the photoresist composition above 7 are not used to prevent decomposition of the photoacid generator.

[0053] The amount of base quencher in the photoresist layer is preferably 0.001 to 1.0 wt %, more preferably 0.01 to 0.8 wt %, or 0.02 to 0.2 wt %, based on the total weight of solids in the photoresist composition.

[0054] The photoresist composition further comprises a solvent, which is used to solvate the polymer and promote miscibility of the various components used in the composition.

[0055] Generally suitable solvents for dissolving, dispensing, and coating include anisole; alcohols such as 1-methoxy-2-propanol (also known as propylene glycol methyl ether, PGME) and 1-ethoxy-2-propanol; esters such as n-butyl acetate, 1-methoxy-2-propyl acetate (also known as propylene glycol methyl ether acetate, PGMEA), methoxyethyl propionate, and ethoxyethyl propionate; ketones such as cyclohexanone, 2,6-dimethyl-4-heptanone, and 2-heptanone; ethyl lactate (EL), 2-hydroxyisobutyric acid methyl ester (HBM), gamma-butyrolactone (GBL), 3-methoxypropanoic acid methyl ester, and combinations thereof.

[0056] The amount of solvent can be, for example, 20 to 95 wt %, preferably 40 to 80 wt %, and more preferably 50 to 70 wt %, based on the total weight of the photoresist composition. It is understood that the term "polymer" used in this context of a component in a photoresist layer can refer only to the polymer (containing acid labile groups) disclosed herein. It is understood that the total solids content includes the polymer, photodestructible base, quencher, surfactant, photoacid generator, and any additives excluding the solvent.

[0057] The photoresist composition can include other optional ingredients, such as one or more surface leveling agents (SLAs), adhesion promoters, and / or plasticizers. If used, the SLA is preferably present in an amount of 0.001 to 0.1 wt % based on the total solids content of the photoresist composition, and the adhesion promoters and / or plasticizers, if used, are each present in an amount of 0.1 to 10 wt % based on the total solids content of the photoresist composition.

[0058] A photoresist composition is applied to the first metal layer 102 to form a photoresist layer 106. In one embodiment, the photoresist layer has a thickness greater than 2 micrometers. The photoresist composition is typically applied to the surface of the metal layer by spin coating, dipping, roller coating, or other conventional coating techniques. Spin coating is preferred. For spin coating, the solids content of the coating solution can be adjusted to provide the desired film thickness based on the particular coating equipment utilized, the viscosity of the solution, the speed of the coating tool, and the amount of time allowed for rotation. In one embodiment, the photoresist composition is applied in a single application.

[0059] The photoresist composition layer is then patternwise exposed to activating radiation through a photomask to create a solubility differential between the exposed and unexposed regions. Referring to FIG. 1B, after deposition of the photoresist layer 106, a mask 110 is placed over the photoresist layer 106 to photopattern the photoresist layer 106. UV light having a wavelength between 10 nanometers and 500 nanometers may be used in the photopatterning. The exposed portions of the photoresist layer can be removed by etching with an appropriate alkaline developer, as shown in FIG. 1C.

[0060] References herein to exposing a photoresist composition layer to activating radiation for the layer indicate that the radiation is capable of forming a latent image in the layer. The photomask has optically transparent and optically opaque regions corresponding to areas of the resist layer that are exposed and unexposed, respectively, by activating radiation. The exposure wavelength is typically below 500 nm, such as UV-visible light from 200 to 500 nm. Preferably, exposure is with 365 nm wavelength radiation (i-line) from a mercury lamp.

[0061] After the exposure of the photoresist composition layer, a post-exposure bake (PEB) is typically performed to decompose the acid-labile groups with the acid generated from the PAG during the exposure process. The PEB can be performed, for example, on a hot plate or in an oven. This results in the formation of a latent image defined by the boundaries between polarity-switched and non-switched regions (corresponding to exposed and unexposed regions, respectively).

[0062] The photoresist composition layer is then contacted with an alkaline developer to remove the exposed portions of the layer, leaving the unexposed areas to form the resist pattern. The developer is typically an aqueous alkaline developer, such as a quaternary ammonium hydroxide solution, e.g., a tetraalkylammonium hydroxide solution, such as 0.26 normality (N) (2.38 wt%) tetramethylammonium hydroxide (TMAH).

[0063] A further aspect is a process for depositing metal on the metal layer 102. Figure 1D is an exemplary depiction of depositing (by plating) a metal 112 on the metal layer 102. The process includes immersing the metal layer in a metal plating solution and electrodepositing the metal onto the metal layer in the exposed portions of the photoresist composition layer. The metal layer 112 is typically formed on the substrate or on the exposed portions of the first metal layer 102.

[0064] The substrate bearing the patterned photoresist layer 106 can be immersed in a metal plating solution to plate metal onto the exposed first metal layer in the areas where the photoresist composition layer has been developed away. The developed areas of the photoresist composition layer act as a template for metal plating. The metal can be plated, for example, by electroplating. Various types of metal plating solutions known in the art can be used. Two or more different layers of metal can also be formed, and the layers can be of the same or different metals. Preferred plating metals include, but are not limited to, copper, nickel, tin, silver, gold, and mixtures and alloys thereof. Metal plating solutions suitable for forming such metals are known in the art and are supplied by DuPont Electronics & Industrial. The thickness of the plated metal layer is typically 1 to 100 micrometers, preferably 5 to 50 micrometers. The thickness of the plated metal layer can be less than or greater than the thickness of the photoresist layer.

[0065] After metal plating, the remaining photoresist layer and underlayer can be removed (stripped) from the substrate, leaving behind plated metal structure 112. Figure IE shows the plated metal structure 112 remaining after removal of the remaining photoresist layer. A suitable photoresist stripper is supplied, for example, by Shipley BPR™ Photostripper (DuPont Electronics & Industrial).

[0066] The exposed first metal layer between the plated metal structures can optionally be removed, for example, by an etch-back process, to electrically isolate each of the plated metal structures. The resulting metal structures can have line shapes that can be useful, for example, for redistribution layers to provide electrical connection between two components. Advantageously, metal lines with small widths and straight (vertical) sidewalls can be formed by the compositions and methods disclosed herein. Such structures find use, for example, in electrical connections in small, lightweight, and thin devices. The line width can be, for example, 0.8 to 10 micrometers, preferably 1 to 3 micrometers. The line height will depend, for example, on the thickness of the photoresist composition resin, but pillar heights of 2 micrometers or more can be formed.

[0067] The present invention is advantageous in that the photoresist compositions can be used to obtain lines with a larger cross-sectional area at the base of the pillar compared to the cross-sectional area at the top. Use of the disclosed photoresist compositions prevents the formation of undercuts at the bottom of the metal lines, thereby preventing collapse of the lines during further processing of the semiconductor.

[0068] The invention will now be illustrated by the following non-limiting examples. [Example]

[0069] The following examples are provided to demonstrate the use of phosphonic acids in photoresist compositions. The examples demonstrate how phosphonic acids can be used to minimize tailing in a photoresist layer.

[0070] The photoresist composition includes a polymer including a first repeat unit having an acid labile group and a second repeat unit including a hydroxystyrene. The polymers are shown in Table 1 below, along with the amount of each repeat unit in the polymer in mole percent. Three different polymers (A1, A2, and A3) were prepared using different combinations of the repeat units shown below.

[0071] The monomers shown in Table 1 are TBA (tertiary butyl acrylate), ECPMA (ethyl cyclopentyl methacrylate), STY (styrene), and PHS (polyhydroxystyrene). The structures of the monomers used in the polymer are shown in Table 1 below.

[0072] [Table 1]

[0073] The photoacid generators (PAGs) used were B1 (N-hydroxynaphthalimide trifluoromethanesulfonate, NHNI-TF) and B2 (N-hydroxynaphthalimide perfluoro-1-butanesulfonate, NHNI-PFBS), supplied by Toyo Gosei Co., Ltd. The structures are shown below. [ka]

[0074] The acidic compounds (with predicted pKa) used in each photoresist composition are listed in Table 2. The pKa values ​​for the acidic compounds were obtained from SciFinder. SciFinder values ​​were calculated using Advanced Chemistry Development Software V11.02 (ACD / Labs). The pKa values ​​of organic compounds have traditionally been measured by potentiometric titration and capillary electrophoresis (CE).

[0075] The structures of the acids are shown in Table 2 below.

[0076] [Table 2]

[0077] The base quenchers used in the photoresist compositions used are listed in Table 3 along with their predicted pKa. The pKa of the compounds was obtained from SciFinder.

[0078] [Table 3]

[0079] Photoresist compositions containing a polymer, a photoacid generator, a base quencher, and an acid were mixed together and then deposited on a metal layer disposed on a substrate. Table 4 shows the formulations of photoresist examples and comparable comparative examples. The loadings of PAG (B), acid (C), base (D), and SLA were adjusted in parts by weight relative to 100% acid-labile polymer (A). The solids content was adjusted to 34 wt%. The solvents used were PGMEA (propylene glycol 1-methyl ether 2-acetate) and GBL (γ-butyrolactone). The ratio of PGMEA to GBL was adjusted to achieve a 98 / 2 weight ratio. The photoresist was filtered using a 0.45 μm polytetrafluoroethylene (PTFE) filter. Table 4 includes examples (designated EX) highlighting the present invention as well as comparative examples (designated CF).

[0080] [Table 4]

[0081] Pretreatment of copper substrate A copper metal layer is deposited on a silicon substrate by plasma deposition to form a copper wafer. Prior to copper deposition, a titanium metal layer is deposited on the silicon substrate for passivation and to facilitate adhesion of the photoresist layer to the substrate. The copper wafer is immersed in 10 wt% sulfuric acid (H2SO4) for 30 seconds, then rinsed in deionized water, dried in a nitrogen atmosphere, puddled with 2.38 wt% TMAH developer for 60 seconds, spin-dried, rinsed in deionized water, and spin-dried. After spin-drying, no heating processes such as dehydration baking and / or coating with an HMDS primer are performed / applied to the copper wafer.

[0082] Process Conditions The process conditions are as follows: Substrate: Surface - Copper / Titanium / Silicon Primer: Not applicable A standard bake (SB) was performed at 135°C / 90 seconds. The photoresist layer has a thickness of 8 micrometers (μm). Exposure: NSR-2005i9C, 0.50 numerical aperture (NA) / 0.68PC Post-exposure bake (PEB) was carried out at 110° C. for 90 seconds. Developer: MF® CD-26, 2.38 wt% TMAH, 80 seconds, single paddle

[0083] Pattern Profile Evaluation The pattern profile of the photoresist layer is determined by the focal center (E op The results were evaluated at an exposure energy that allowed for a space width of 1.5 micrometers (μm) at 1000 nm. Enlarged cross-sectional images of the bottom of a 1.5 μm isolated trench pattern and the center of focus of a 1.5 μm dense trench pattern were also evaluated.

[0084] Figure 2 shows Table 5, which illustrates the effect of adding an acidic compound on pattern profiles. Adding the acidic compound C1 (phenylphosphonic acid) can eliminate the tailing profile seen in Comparative Example CF-2 (no acid) in Figure 2 (as seen in the micrograph EX-1). However, it is unclear whether this effect of salicylic acid is due to the acid strength. (Phenylphosphonic acid (C1) has stronger acidity (i.e., a lower pKa) than salicylic acid (C4).) Figure 2 compares cross-sectional pattern profiles under different acids. The bottom profiles of 1.5 μm isolated trenches were compared. This tailing profile effect is not observed when compound C4 (salicylic acid) is added to the photoresist composition.

[0085] The pattern profile tends to include undercut and overhang by increasing the loading of compounds C1 or C2 (phosphonic acids). However, this effect is not observed when C3 (ethylhexyl phosphate) or C5 (benzenesulfonic acid hydrate) are used as the acid in the photoresist composition. From these results, it can be inferred that the effect of adding acidic compounds does not depend on their strength but may be due to their specific chemical structure. Furthermore, it can be seen that phosphate (C3) does not reduce copper footing, while phosphonic acids (C1 and C2) reduce footing and generate undercut by controlling the loading amount.

[0086] Figure 3 (showing Table 6) compares the effect of acidic compounds on cross-sectional pattern profiles. In particular, the bottom profiles of 1.5 μm isolated trenches are compared for different acids (C1, C2, C3, and C5). When compound C1 or C2 is used in a larger amount in the photoresist composition, the pattern profile tends to have undercut or overhang (57% compared to 78% and 100%). However, this effect is not observed when C3 or C5 is used as the acid. From these test results, we can conclude that the effect of adding acidic compounds cannot be estimated solely by acid strength. Without being limited by theory, this is caused by specific chemical structures. It can be seen that phosphate (C3) does not reduce copper footing, while phosphonic acids (C1 and C2) reduce footing and create undercut by controlling their loading.

[0087] Figure 4 (showing Table 7) shows the effect of different base quenchers on the pattern profile while simultaneously using different loadings of the acidic compound C1 (phenylphosphonic acid). As in the previous table (Table 6 shown in Figure 3), the bottom profile of the 1.5 μm isolated trench is observed. Adding larger amounts of acidic compounds tends to result in undercut or overhang features in the copper when using base quenchers (D1, D3, or D2). However, when D4 (tBOC-4HP) or D5 (nicotinamide) were used in conjunction with the acidic compound C1, the tailing profile did not improve.

[0088] Figure 5 (showing Table 8) and Figure 6 (showing Table 9) show the effect of different base-quencher acidic compound combinations on pattern profiles. These figures show that combining acidic compound C1 with one of base quenchers D1, D10, or D2 (in a photoresist composition) reduces the presence of footing. Combining C1 with one of D4, D6, D7, D5, D8, and D9 shows substantial footing. From these test results, the effect of acidic compound (C) and base quencher (D) is determined by the strength (pKa) of the base quencher. The combination of D10 and C1 in a photoresist composition produced a white precipitate after mixing. In a follow-up experiment, precipitation was observed by mixing 1 wt % PGMEA solutions of D10 and C1 in equal molar amounts. The formation of an acid-base salt or complex is one possible reason for the precipitation. The precipitation may be caused by the solubility of the salt in the photoresist solvent (PGMEA / GBL = 98 / 2).

[0089] Figure 7 (showing Table 10) shows the effect of different PAGs (B1 and B2) on a photoresist composition using a combination of acidic compound C1 and base quencher D1. Either the B1 or B2 PAG produces an undercut profile using the acid-base combination of C1 and D1.

[0090] Without being limited by theory, it is believed that phosphonic acid forms a monolayer on the metal oxide formed on the metal (in this case, a copper layer disposed on a substrate). The acid is believed to covalently bond to the metal oxide, thus acting as a corrosion inhibitor. Copper corrosion can occur through ionization, migration, and oxidation. If any one of these copper corrosion processes can be stopped, corrosion will not proceed. When a covalent bond is formed between phenylphosphonic acid and the metal oxide (CuO), copper ions do not migrate to CuO, thereby maintaining a constant concentration. Passivation of the copper oxide surface by phosphonic acid prevents further metal ionization and reduces photoacid consumption due to metal ionization. This reduction in photoacid consumption prevents the presence of significant footing on metal (e.g., copper) substrates. However, it should be noted that phosphonic acid is preferably added in an amount effective to reduce ionization. Excessive amounts of phosphonic acid can act as free acid, promoting pattern collapse and the formation of overhanging pattern profiles. [Explanation of symbols]

[0091] 100 boards 102 First Metal Layer 106 Photoresist layer 108 Activating radiation 110 Photomask 112 Metal structures

Claims

1. 1. A metallization method comprising: (a) providing a photoresist layer on a first surface of a substrate formed from a photoresist composition comprising: a polymer containing acid labile groups; a photoacid generator; an organic phosphonic acid; a base quencher; and a solvent; (b) patternwise exposing the photoresist layer to activating radiation; (c) developing the exposed photoresist layer with a basic developer to form a photoresist pattern; (d) after forming the photoresist pattern, plating a metal onto the first surface of the substrate using the photoresist pattern as a plating mask; the photoresist pattern has an undercut profile; The metallization method, wherein the base quencher is selected from the group consisting of 2,8-dimethyl-6H,12H-5,11methanodibenzo[b,f][1,5]diazocine (Tröger's base), ethyl-3-(morpholino)propionate, 4-(p-tolyl)morpholine, and combinations thereof.

2. 2. The metallization method of claim 1, further comprising: (e) removing said photoresist after plating said metal.

3. 2. The metallization method of claim 1, wherein the photoresist layer is disposed directly on a metal layer.

4. 2. The metallization method of claim 1, wherein the photoresist layer has a thickness greater than 2 [mu]m.

5. 2. The metallization method of claim 1, wherein said organic phosphonic acid is phenylphosphonic acid.

6. 2. The metallization method of claim 1, wherein said organophosphonic acid is present in said photoresist layer in an amount of 0.01 to 0.50 parts by weight per 100 parts of said polymer containing acid labile groups.

7. 2. The metallization method of claim 1, wherein the acid labile groups are selected from tertiary ester groups, acetal groups, or combinations thereof.

8. 10. The metallization method of claim 1, wherein the polymer further comprises repeat units formed from a vinyl aromatic monomer.

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