Photoresist composition and pattern formation method

Abstract

To provide a photoresist composition and a pattern formation method.SOLUTION: A photoresist composition includes: a nonionic thioxanthone compound, a nonionic oxime compound, or a combination of a nonionic thioxanthone compound and a nonionic oxime compound; a polymer comprising a first repeating unit of formula (3) and a second repeating unit of formula (4a); a basic quencher; a photoacid generator; and a solvent. In formula (3), Z is a non-hydrogen substituent including an acid-labile site. In formula (4a), Z2 is a hydrogen atom or a substituted or unsubstituted C1-C5 alkyl group.SELECTED DRAWING: Figure 1D

Description

Technical Field

[0001] The present disclosure relates to a photoresist composition and a method for manufacturing the same. The present disclosure also relates to a patterning process for manufacturing a semiconductor that prevents the occurrence of a footing profile in a photoresist pattern.

Background Art

[0002] Mobile devices, devices that are part of the Internet of Things (IoT), and wearable electronics have, for many years, despite miniaturization, become smaller, lighter, and thinner devices that use large amounts of memory and perform even larger amounts of computation.

[0003] The manufacturing and packaging of these electronic devices play an important role in size reduction. For example, the flip-chip packaging method is used to increase the density of I / O (input / output) connections between devices, particularly for microprocessing units (MPUs) and dynamic random access memory (DRAM) semiconductor chips.

[0004] Dry plasma etching is widely used in semiconductor manufacturing. The manufacture of 3D-NAND devices requires the use of a thick film photoresist having durable etching resistance. 3D-NAND (three-dimensional NAND) is a type of flash memory technology used in data storage devices such as solid state drives (SSDs) and USB flash drives. The "3D" in 3D NAND means stacking memory cells in multiple layers to form a vertical structure.

[0005] When meeting the technical specifications of a thick film photoresist, there is a tendency to increase the height of the pattern and narrow the width. To meet these technical specifications, chemically amplified photoresist (CAR) is used.

[0006] One of the concerns in plasma etching processes involving chemically amplified photoresists (CARs) is the presence of ultraviolet (UV) radiation that activates photoacid generators (PAGs) present in the photoresist composition. The acid generated by the activation of the photoacid generator decomposes acid-labile groups in the polymer and accumulates and aggregates inside the photoresist film. Beyond a critical point, these aggregates can cause swelling or rupture. Even when the degree of gas evolution is low, it may be revealed as voids when examined using scanning microscopy.

[0007] One of the promising solutions to mitigate the problem of gas evolution is to reduce the amount of acid-labile components present in the photoresist composition. However, this adjustment has been shown to have an adverse effect on the dissolution rate and is disadvantageous for thick-film applications. Another way to mitigate this problem is to increase the amount of quencher base added to the photoresist composition. It has been shown that increasing the amount of quencher is effective in reducing the severity of swelling. However, this reduction comes at the cost of sacrificing sensitivity.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Patent Document 14

Patent Document 15

Patent Document 16

Patent Document 17

Patent Document 18

Patent Document 19

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, while maintaining the sensitivity, it is desirable to improve the dry etching resistance by reducing the formation of voids and / or the occurrence of swelling caused by UV radiation during plasma etching.

Means for Solving the Problems

[0010] In this specification, a nonionic thioxanthone compound, a nonionic oxime compound, or a combination of a nonionic thioxanthone compound and a nonionic oxime compound; a polymer containing a first repeating unit of formula (3) and a second repeating unit of formula (4a):

Chemical formula

Brief Description of Drawings

[0011]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 2

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5

Figure 6

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] As used herein, the terms "a", "an", and "the" are not meant to limit quantity and should be construed to include both the singular and plural forms unless specifically indicated herein or clearly inconsistent with the context. "Or" means "and / or" unless otherwise specified.

[0013] As used herein, the term "acid-labile group" refers to a group in which the bond is cleaved, optionally and typically by heat treatment, under the catalysis of an acid, to yield a polar group such as a carboxylic acid or alcohol group formed on the polymer, and the moiety connected to the optionally and typically cleaved bond is detached from the polymer. Such an acid is typically a photoacid 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 an alkyl group and an aryl group, tertiary alkoxy groups, acetal groups or ketal groups. Acid-labile groups are generally referred to in the art as "acid-cleavable groups", "acid-cleavable protecting groups", "acid-labile protecting groups", "acid-detachable groups", "acid-decomposable groups" and "acid-sensitive groups".

[0014] In lithography, the term "underexposure region" refers to a region of exposure conditions where the amount of light or radiation used to expose the photoresist is intentionally reduced below the standard or optimal exposure amount. This is a controlled variation from the nominal exposure conditions. The exposure amount in lithography is useful for defining the desired pattern on the photoresist. Underexposure involves intentionally reducing the exposure energy during the lithography process. This approach may be used to explore the sensitivity limits of the photoresist or to intentionally induce variations in pattern dimensions.

[0015] The term "process window" refers to the range of process conditions (such as exposure amount, focus, depth of focus, etc.) under which the manufacturing process is robust and the desired pattern on the photoresist is consistently and accurately formed. "Improved process window" means an expansion or enhancement of this range, resulting in more tolerant and reliable manufacturing conditions.

[0016] The term "thioxanthone" includes nonionic sulfur-containing heterocyclic compounds containing a thioether group (S atom) in the structure. This includes nonionic derivatives of thioxanthone.

[0017] The term "oxime" includes nonionic oximes and their derivatives. This includes nonionic oxime esters, oxime ethers, and their derivatives.

[0018] Disclosed herein is a photoresist composition that can be used for plasma dry etching. This photoresist composition reduces the presence of voids and other forms of photoresist damage and exhibits an improved process window. This photoresist composition contains a polymer containing an acid-labile group, a nonionic thioxanthone compound and / or a nonionic oxime compound, a photoacid generator, and a basic deactivator, and this nonionic thioxanthone compound and / or nonionic oxime compound improves the process window compared to a photoresist composition containing all the same components except for the nonionic thioxanthone compound and / or nonionic oxime compound. Due to the nonionic thioxanthone compound and / or nonionic oxime compound, the photoresist composition can have an improved process window at an exposure wavelength of 300 to 400 nanometers.

[0019] Without being limited to theory, it is believed that the nonionic thioxanthone compound absorbs a portion of the UV radiation to which the photoresist composition is exposed during the plasma etching process. The absorption of UV radiation reduces acid generation from the photoacid generator, and as a result, improves the process window. The nonionic oxime compound generates a basic deactivator when exposed to UV radiation and effectively deactivates the acid generated during the etching process. The deactivation of the acid promotes the improvement of the process window. This also improves the resistance to dry plasma etching.

[0020] The above-described photoresist composition is disposed on a substrate to form a photoresist layer. The photoresist layer is patternwise exposed to actinic radiation. The exposed photoresist layer is then developed with a basic developer, thereby removing a part of the photoresist layer to form a relief pattern. The relief pattern is used as a mask during dry plasma etching.

[0021] As described above, in the plasma etching process, the acid generated by the activation of the photoacid generator decomposes the acid-labile groups in the polymer. Excess acid may aggregate inside the photoresist film and ultimately cause swelling (void formation) or film rupture. The nonionic thioxanthone compound and / or nonionic oxime compound enable the photoresist composition to exhibit improved etching resistance by reducing the number of such voids. These compounds absorb UV radiation and reduce PAG decomposition during plasma etching, which affects void formation by preventing the cleavage of acid-labile polymers.

[0022] Figures 1A - 1D show a method of forming a pattern on a substrate using dry etching. Figure 1A shows a substrate 100 on which a first layer 102 is disposed. Figure 1B shows the coating of a photoresist layer 106 onto the first layer 102, followed by the photoexposure of the photoresist layer 106. 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 actinic radiation 108 through a photomask 110 having optically opaque regions and optically transparent regions. UV light having a wavelength of 10 - 400 nanometers is used for photopatterning.

[0023] Figure 1C shows the development of the exposed portion of the photoresist layer 106. The exposed portion of the photoresist layer 106 is removed by an aqueous alkaline developer as seen in Figure 1C. Thereafter, as seen in Figure 1D, the exposed portion of the first layer 102 and / or the substrate 100 is removed by plasma dry etching. During the dry plasma etching, the photoresist layer 106 (where the exposed portion has been removed) functions as an etching mask. This etching mask exposes a portion of the first layer 102 and / or the substrate 100 so that it can be removed during the etching.

[0024] substrate Examples of substrates include, but are not limited to, silicon wafers, glass substrates, and plastic substrates, and such substrates optionally include one or more layers or features formed thereon. A preferred substrate is a silicon wafer.

[0025] first layer Figure 1A shows a substrate 100 on which a first layer 102 is disposed. The first layer 102 is selectively removed by dry plasma mask etching. The first layer includes a metal, a ceramic, or a combination thereof. The metal includes aluminum, copper, titanium, silicon, or a combination thereof. The ceramic includes silicon oxide, silicon nitride, titanium nitride, or a combination thereof. In one embodiment, the first layer includes a stack of multiple layers, and alternating layers therein may include silicon oxide and silicon nitride. The stack may include 10 to 500 such alternating layers.

[0026] photoresist layer Figure 1B shows the deposition of a photoresist layer 106 on the first layer 102 to be etched. The photoresist composition 106 includes a polymer containing an acid-labile group, a photoacid generator, a quencher, and a solvent. The polymer includes a first repeating unit containing an acid-labile group. In one embodiment, the polymer includes a second repeating unit containing a vinyl aromatic group. In one embodiment, the polymer includes a first repeating unit of formula (3) and a second repeating unit of formula (4a): [Chem.] (In formula (3), R1 is a hydrogen atom or a substituted or unsubstituted C1-C3 alkyl group, Z is a non-hydrogen substituent containing an acid-labile moiety, and in formula (4a), "a" is an integer including 1-5, and Z 2 is a hydrogen atom or a C1-C5 alkyl group).

[0027] An acid-labile group is a chemical moiety that undergoes a deprotection reaction in the presence of an acid. The deprotection of some acid-labile groups used in the examples is effected by heat. An acetal protecting group is readily deprotected at room temperature. The polymer of the photoresist composition undergoes a change in solubility in the developer as a result of reaction with an acid generated from a photoacid generator (contained in the photoresist composition) after soft baking, exposure to actinic radiation, and post-exposure baking. This is due to photoacid-induced cleavage of the acid-labile group that causes a change in the polarity of the polymer. The acid-labile group can be selected, for example, from 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 carboxylic acid oxygen of the ester of the polymer. Cleavage of such an acid-labile group forms a carboxylic acid group.

[0028] In one embodiment, a polymer containing an acid-labile group has the following formula (1): [Chem.] (wherein Z is selected from a hydrogen atom, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 fluoroalkyl, or a cyano group, and Z 1 is a non-hydrogen substituent containing an acid-labile group whose cleavage forms a carboxylic acid on the polymer) and contains a polymerized unit having the structure shown.

[0029] In one embodiment, at the time of decomposition, the acid-labile group that forms a carboxylic acid group on the polymer is preferably a tertiary ester group of the formula -C(O)OC(R1)3 or an acetal group of the formula -C(O)OC(R2)2OR3. In these formulas, each R1 is independently a linear C1-20 alkyl, branched C3-20 alkyl, monocyclic or polycyclic C3-20 cycloalkyl, linear C2-20 alkenyl, branched C3-20 alkenyl, monocyclic or polycyclic C3-20 cycloalkenyl, monocyclic or polycyclic C6-20 aryl, or monocyclic or polycyclic C2-20 heteroaryl, preferably a linear C1-6 alkyl, branched C3-6 alkyl, or monocyclic or polycyclic C3-10 cycloalkyl, each of which may be substituted or unsubstituted, and each R1 may optionally contain one or more groups selected from -O-, -C(O)-, -C(O)-O-, or -S- as part of its structure, and any two R1 groups may optionally combine to form a ring; R2 is independently hydrogen, fluorine, linear C1-20 alkyl, branched C3-20 alkyl, monocyclic or polycyclic C3-20 cycloalkyl, linear C2-20 alkenyl, branched C3-20 alkenyl, monocyclic or polycyclic C3-20 cycloalkenyl, monocyclic or polycyclic C6-20 aryl, or monocyclic or polycyclic C2-20 heteroaryl, preferably hydrogen, linear C1-6 alkyl, branched C3-6 alkyl, or monocyclic or polycyclic C3-10 cycloalkyl, each of which may be substituted or unsubstituted, and each R2 may optionally contain one or more groups selected from -O-, -C(O)-, -C(O)-O-, or -S- as part of its structure, and a plurality of R2 groups may optionally combine to form a ring;R3 is a linear C1-20 alkyl, branched C3-20 alkyl, monocyclic or polycyclic C3-20 cycloalkyl, linear C2-20 alkenyl, branched C3-20 alkenyl, monocyclic or polycyclic C3-20 cycloalkenyl, monocyclic or polycyclic C6-20 aryl, or monocyclic or polycyclic C2-20 heteroaryl, preferably a linear C1-6 alkyl, branched C3-6 alkyl, or monocyclic or polycyclic C3-10 cycloalkyl, each of which may be substituted or unsubstituted, and each R3 may optionally contain one or more groups selected from -O-, -C(O)-, -C(O)-O-, or -S- as part of its structure. One of the R2s may optionally form a ring together with R3. Such monomers are typically vinyl aromatic, (meth)acrylate or norbornyl monomers.;

[0030] Suitable acid-labile group-containing units include, for example, 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, methyl adamantyl (meth)acrylate, ethyl adamantyl (meth)acrylate, etc., as well as acid-labile (alkyl)acrylate units such as other cyclic and acyclic (alkyl)acrylates like alicyclic ones.

[0031] Acetal and ketal-based acid-labile groups can replace the hydrogen atom at the terminal of an alkali-soluble group such as a carboxyl group and bond to an oxygen atom. When an acid is generated, the bond between the acetal group 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, for example, in (Patent Document 1), (Patent Document 2), (Patent Document 3), (Patent Document 5), (Patent Document 4), and (Patent Document 5). For example, as described in (Patent Document 6), acetal groups and ketal groups as part of a sugar derivative structure that form a hydroxyl group by cleavage are also suitable.

[0032] Suitable polymers include, for example, phenol resins containing acid-labile groups. Particularly preferred resins of this classification include the following: (i) polymers containing polymerized units of vinylphenol and the above-mentioned acid-labile (alkyl) acrylates, such as the polymers described in (Patent Document 7) and (Patent Document 8); (ii) polymers containing polymerized units of vinylphenol, optionally substituted vinylphenyl (e.g., styrene) without hydroxy or carboxy ring substituents, and the above-mentioned acid-labile (alkyl) acrylates, such as the polymers described in (Patent Document 7); (iii) polymers containing repeating units containing an acetal or ketal moiety that reacts with a photoacid, and optionally aromatic repeating units such as phenyl groups or phenol groups, such as the polymers 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 of 200 nm or more, such as 248 nm and 365 nm.

[0033] Suitable polymers include those disclosed in (Patent Document 11), (Patent Document 12), and (Patent Document 13), etc., which are useful for imaging at specific wavelengths less than 200 nm, such as 193 nm. For imaging at a wavelength of 193 nm, the polymer is preferably substantially free (e.g., less than 15 mol%) and preferably does not completely contain phenyl, benzyl, or other aromatic groups, as such groups highly absorb radiation.

[0034] Other suitable polymers for use in a photoresist composition include, for example, those containing polymerization units of non-aromatic cyclic olefins (intra-ring double bonds), such as optionally substituted norbornene, for example, the polymers described in (Patent Document 14) and (Patent Document 15). Still other suitable polymers for use in a photoresist composition include polymers containing polymerization anhydride units, particularly polymerization maleic anhydride and / or itaconic anhydride units, as disclosed in (Patent Document 4) and (Patent Document 16).

[0035] Polymers containing repeating units containing heteroatoms, particularly oxygen and / or sulfur (however, other than anhydrides, i.e., the units do not contain keto ring atoms), are also suitable for use in a photoresist composition. The heteroalicyclic units can be condensed to the main chain of the polymer and can include condensed carbon alicyclic units provided by the polymerization of norbornene groups and / or anhydride units provided by the polymerization of maleic anhydride or itaconic anhydride. Such polymers are disclosed in (Patent Document 17) and (Patent Document 18). Other suitable heteroatom group-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 (Patent Document 19).

[0036] The polymer may further include units containing lactone moieties for controlling the dissolution rate of the polymer and the photoresist composition. Examples of monomers suitable for use in polymers containing lactone moieties include the following. [Chemical formula]

[0037] In one embodiment, the polymer typically further comprises units containing polar groups, which enhance the etching resistance of the polymer and the photoresist composition and provide additional means for controlling the dissolution rate of the polymer and the photoresist composition. Examples of monomers for forming such units include the following. [Chemical formula]

[0038] The polymer may contain one or more additional units of the type described above. Typically, the additional units of the polymer contain polymerizable groups that are the same as or similar to those used in the monomers for forming the other units of the polymer, but may contain other different polymerizable groups in the same polymer backbone.

[0039] The polymer may also contain one or more repeating units derived from the polymerization of vinyl aromatic monomers. An exemplary vinyl aromatic monomer is styrene. In one embodiment, the polymer derived from a vinyl aromatic monomer has the following formula (4a): [Chemical formula] (wherein a is from 1 to 5, and Z 2 is hydrogen or an alkyl group having 1 to 5 carbon atoms) has the structure shown. In a preferred embodiment, a is 1 and Z 2 is hydrogen. The vinyl aromatic monomer preferably has a hydroxyl group at the para position on the aryl ring. A preferred vinyl aromatic polymer is poly(p-hydroxystyrene) (abbreviated as PHS).

[0040] In one embodiment, the polymer for use in a photoresist composition has a first repeating unit of formula (3) and a second repeating unit of formula (4): [Chemical formula] (wherein R1 is a hydrogen atom or a substituted or unsubstituted C1-C3 alkyl, and Z is a non-hydrogen substituent containing an acid-labile site) and includes. In one embodiment, m + n (in formulas (3) and (4)) is 70 to 100 mole percent (mol%). In one embodiment, m is 10 to 90 mol%, preferably 15 to 50 mol%, preferably 20 to 40 mol% based on all the polymerized units present in the polymer, and n is 10 to 80 mol%, preferably 20 to 75 mol%, more preferably 60 to 70 mol%. In one embodiment, the molar ratio of n to m is 0.7 to 9, preferably 0.2 to 4.

[0041] When the polymer includes a third repeating unit (different from the first and second repeating units), the third repeating unit may be present in the polymer in an amount of 5 to 35 mol%, preferably 10 to 30 mol% based on all the polymerized units present in the polymer.

[0042] Exemplary polymers include, but are not limited to, for example, the following. [Chemical formula]

[0043] Polymers suitable for use in photoresist compositions are commercially available and can be readily prepared by those skilled in the art. The polymer is present in the photoresist composition in an amount sufficient to make the exposed coating layer of the photoresist developable in a suitable developer.

[0044] Typically, the polymer is present in the photoresist composition in an amount of 70 to 100% by weight based on the total solids of the photoresist composition. The weight average molecular weight Mw of the polymer, when measured by gel permeation chromatography using polystyrene standards, is typically less than 100,000, for example, 4000 to 100,000, more typically 4000 to 20,000 grams per mole (g / mol). Blends of two or more of the above polymers can be suitably used in the photoresist composition of the present invention.

[0045] The photoresist composition contains a nonionic photoacid generator. In one embodiment, the photoresist composition may optionally contain an ionic photoacid generator. It is desirable to use a photoacid generator that generates a photoacid by Norrish-1 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 receives a photon and is excited to the photochemical singlet state. In one embodiment, the photoacid generator has a structure represented by formula (5)

Chemical formula

[0046] 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 of the formula (5a) or (5b) shown below: [Chemical formula] It may be one or more of the structures of.

[0047] 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%, more preferably 0.5 to 3 wt% based on the total solids of the photoresist composition. By minimizing the amount of the photoacid generator added, the UV transparency of the photoresist can also be minimized. This increases the UV transparency of the photoresist layer.

[0048] As described above, the photoresist composition contains a non - ionic thioxanthone compound and / or a non - ionic oxime compound to improve the process window and to prevent void formation during dry plasma etching. The non - ionic thioxanthone compound can be used alone or in combination with the non - ionic oxime compound in the photoresist composition. The non - ionic thioxanthone compound has the structure of formula (6) [Chemical formula] (In the formula, R is a non-hydrogen substituent, and each T is independently a hydrogen atom, a substituted or unsubstituted C 1~5 alkyl, amino, mercapto, or hydroxyl, and each m is independently an integer from 0 to 4). In one embodiment, each T is independently a hydrogen atom or a substituted or unsubstituted C 1~3 alkyl group. In another embodiment, the nonionic thioxanthone compound is 2-isopropylthioxanthenone, diethylthioxanthone, or a combination thereof.

[0049] The nonionic thioxanthone compound can be used in the photoresist composition in an amount of 0.05 to 3% by weight, preferably 0.08 to 2% by weight, more preferably 0.1 to 1.5% by weight, based on the total solids of the photoresist composition.

[0050] In one embodiment, the nonionic oxime compound has the formula (7A) [Chemical formula] In the formula (7A), R 21 is a hydrogen atom, a substituted or unsubstituted C 1~20 alkyl, a substituted or unsubstituted C 3~20 cycloalkyl, a substituted or unsubstituted C 2~20 alkenyl, a substituted or unsubstituted C 6~30 aryl, a substituted or unsubstituted C 3~30 heteroaryl, a substituted or unsubstituted C 7~20 arylalkyl, a substituted or unsubstituted C 4~20 heteroarylalkyl, or a combination thereof, and R 21 may optionally contain a -C(O)- group bonded to the O atom; R 22 and R 23 are each independently a hydrogen atom, a substituted or unsubstituted C 1~20 alkyl, a substituted or unsubstituted C 3~20 cycloalkyl, a substituted or unsubstituted C 2~20 alkenyl, a substituted or unsubstituted C 6~30 aryl, a substituted or unsubstituted C 3~30Heteroaryl, substituted or unsubstituted C 7~20 Arylalkyl, substituted or unsubstituted C 4~20 Heteroarylalkyl, or a combination thereof, provided that R 22 and R 23 cannot both be hydrogen atoms, and R 22 and R 23 may optionally be linked to each other via a single bond or a divalent linking group to form a ring. The ring formed by the condensation of R 22 and R 23 may contain one of the following structures.

[0051] In one embodiment, R21 contains a -C(O)- group bonded to an O atom, and R22 and R23 are linked to each other via a single bond or a divalent linking group to form a ring.

[0052] In one embodiment, R22 and R23 can be used to form fluorene.

[0053] In one embodiment, preferred nonionic oximes include 1-(2-naphthalenyl)ethanone O-(2-phenylacetyl)oxime ((E)-1-(naphthalen-2-yl)ethane-1-one O-(2-phenylacetyl)oxime (hereinafter also referred to as oxime A)) and (9H-fluoren-9-one, O-(2-phenylacetyl)oxime) (also referred to as 9H-fluoren-9-one O-(2-phenylacetyl)oxime) (hereinafter oxime B).

Chemical formula

[0054] The nonionic oxime compound can be used in the photoresist composition in an amount of 0.1 to 1.5% by weight, preferably 0.2 to 1% by weight, based on the total solids of the photoresist composition.

[0055] The photoresist composition also contains a basic deactivator. The basic deactivator improves the resolution of the developed resist relief image. However, the nonionic photoacid generator exemplified as an embodiment decomposes in the presence of a basic substance. Therefore, in order to prevent the photoacid generator from decomposing during storage of the photoresist composition, it is preferable that the basicity is low.

[0056] The basic deactivator is selected from N-diethyldodecanamide, 2,8-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (trager base), 1,1-dimethylethyl 4-hydroxypiperidine-1-carboxylate, N-allylcaprolactam, ethyl-3-(morpholino)propionate, 4-(p-tolyl)morpholine, or a combination thereof. A preferred basic deactivator is 2,8-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (trager base).

[0057] The amount of the basic deactivator in the photoresist layer is preferably 0.001 to 1.0% by weight, more preferably 0.01 to 0.8% by weight or 0.02 to 0.2% by weight based on the total weight of the solids in the photoresist composition.

[0058] Solvent The photoresist composition further contains a solvent. The solvent is used to solvate the polymer and promote the miscibility of various components used in the composition.

[0059] Solvents generally suitable 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), methyl 2-hydroxyisobutyrate (HBM), gamma-butyrolactone (GBL), methyl 3-methoxypropionate, and combinations thereof.

[0060] The amount of the solvent can be, for example, 20 to 98% by weight, preferably 40 to 90% by weight, more preferably 60 to 80% by weight, based on the total weight of the photoresist composition. It will be understood that the "polymer" used in connection with the components in the photoresist layer can only mean the polymers (containing acid-labile groups) disclosed herein. The total solids are understood to include the polymer, the basic deactivator, the surfactant (if used), the photoacid generator, and any optional additives other than the solvent. The solids content of the composition can typically be 2 to 80% by weight, preferably 10 to 60% by weight, based on the total weight of the photoresist composition.

[0061] The photoresist composition can include other optional raw materials such as one or more surface leveling agents (SLA), adhesion promoters, and / or plasticizers. When used, the SLA is preferably present in an amount of 0.001 to 0.1% by weight based on the total solids of the photoresist composition, and when used, the adhesion promoter and / or plasticizer are each present in an amount of 0.1 to 10% by weight based on the total solids of the photoresist composition.

[0062] The photoresist composition further comprises a weakly acidic or basic compound that makes it easier to control the influence of the substrate. When the photoresist is disposed on a metal substrate such as copper, typically a footing profile is generated in the photoresist. These weakly acidic or basic compounds form a passivation layer on the metal surface and reduce its influence. When used, the weakly acidic or basic compound is present in an amount of 0.001 to 0.1% by weight based on the total weight of the solids of the photoresist composition.

[0063] The photoresist composition is applied to the first layer 102 to form the photoresist layer 106. In one embodiment, the photoresist layer has a thickness exceeding 2 micrometers. The photoresist composition is generally 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 specific coating apparatus used, the viscosity of the solution, the speed of the coating tool and the amount of rotational tolerance time. In one embodiment, the photoresist composition is applied in a single application.

[0064] The photoresist composition layer is then patternwise exposed to actinic radiation through a photomask to create a difference in solubility between the exposed and unexposed regions. Referring to FIG. 1B, after deposition of the photoresist layer 106, a mask 110 is disposed on the photoresist layer 106 to photopattern the photoresist layer 106. UV light having a wavelength of 10 nanometers to 500 nanometers can be used for photopatterning. The exposed portion of the photoresist layer can be removed by an aqueous alkaline developer such as 2.38% by weight of tetramethylammonium hydride, followed by water washing and spin drying, as seen in FIG. 1C.

[0065] References herein to exposing a photoresist composition layer to radiation that activates the layer indicate that the radiation can form a latent image in the layer. The photomask has optically transmissive regions and optically opaque regions corresponding to regions of the resist layer that are respectively exposed and unexposed to the activating radiation. The exposure wavelength is typically below 500 nm, such as UV-visible light of 200-500 nm. Preferably, the exposure is performed with radiation of a wavelength of 365 nm (i-line) from a mercury lamp.

[0066] After exposure of the photoresist composition layer, a post-exposure bake (PEB) is typically performed to decompose acid-labile groups by 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. Thereby, a latent image defined by the boundary between the region where the polarity is switched and the region where the polarity is not switched (corresponding to the exposed region and the unexposed region respectively) is formed.

[0067] The photoresist composition layer is then contacted with an alkaline developer to remove the exposed portion of the layer, leaving the unexposed regions that form the resist pattern. The developer is typically an aqueous alkaline developer, such as a tetraalkylammonium hydroxide solution, such as a 0.26 normal (N) (2.38 wt%) tetramethylammonium hydroxide (TMAH) solution.

[0068] A further aspect is a process for dry plasma etching of the first layer 102. The first layer 102 is partially removed by using the relief pattern of the photoresist as an etching mask. After dry plasma etching, any remaining portion of the photoresist composition can be removed (stripped) from the substrate.

[0069] The present invention is advantageous in that a photoresist composition can be used to obtain a wider process window in a lithography process for forming an etching mask. Thereafter, the etching mask formed by the photoresist provides greater resistance to the etching process by reducing the formation of voids caused by gas evolution from the acid-labile groups of the polymer.

[0070] Herein, the present invention is illustrated by the following non-limiting examples.

Examples

[0071] Example 1 This example was conducted to determine the process window of a photoresist composition that contains neither a nonionic thioxanthone compound nor a nonionic oxime compound, or a photoresist composition that contains either a nonionic thioxanthone compound or a nonionic oxime compound, or a photoresist composition that contains both a nonionic thioxanthone compound and a nonionic oxime compound. The composition contained one of Additive-A and Additive-B for controlling the pattern profile. Both additives facilitate the removal of the footing profile.

[0072] In this example, the photoacid generator (PAG-1) is N-hydroxynaphthalimide trifluoromethanesulfonate. The basic deactivator (Base-A) is a tracer base. Additive-A is 1H-1,2,3-benzotriazole. Additive-A has a weaker basicity than the basic deactivator. Additive-B is trithiocyanuric acid. 2-Isopropylthioxanthone (ITX) and diethylthioxanthone (DETX) are nonionic thioxanthone compounds that reduce photoacid generation by the photoacid generator. As nonionic oxime compounds that improve the processing window (for example, additives that generate basic deactivators that improve the processing window), 1-(2-naphthalenyl)ethanone O-(2-phenylacetyl)oxime (also called oxime-A) and (9H-fluoren-9-one, O-(2-phenylacetyl)oxime) (also called oxime-B) can be mentioned. The structures of all the materials described above are shown below. [Chemical formula]

[0073] All samples contain 0.02 wt% of POLYFOX PF-656, and the weight ratio of PGMEA / GBL is 98 / 2.

[0074] The acid-labile polymer of the photoresist composition has a weight average molecular weight (Mw) of 23,000 grams per mole and contains 35 mol% of tertiary butyl alcohol and 65 mol% of polyhydroxystyrene. Table 1 shows samples of the photoresist composition in which the solid content is indicated in parts by weight (pbw).

[0075] The comparative photoresist compositions shown in Table 1 are CF-5 to CF-8. The comparative compositions do not contain an oxime or a thioxanthone. The exemplary compositions EX-1 to EX-21 contain one of a nonionic oxime compound or a nonionic thioxanthone compound, or both a nonionic oxime compound and a nonionic thioxanthone compound.

[0076] A titanium layer with a thickness of 150 nm was deposited on a 150 mm silicon substrate. Subsequently, a copper layer with a thickness of 200 nm was deposited on the titanium layer by sputtering. The surface of the copper layer was cleaned for 30 seconds using a 10 wt% sulfuric acid (H2SO4) solution to remove the surface oxide layer, and then rinsed with deionized (DI) water. Thereafter, a pressurized nitrogen stream was blown onto the substrate to remove moisture. The substrate was paddle-coated with a 2.38 wt% TMAH solution for 60 seconds and then rinsed with deionized water. Subsequently, the substrate was spin-dried. No primer was used on the copper layer.

[0077] Thereafter, the photoresist composition was spin-coated onto the substrate using a D-Spin 60A SK-W60A-AVP wafer track (Sokudo). The spin speed was adjusted, and after a soft bake at 135 °C for 90 minutes, a photoresist layer with a thickness of 7.5 micrometers (μm) was obtained.

[0078] Next, the photoresist layer was mask-exposed using an NSR-2005i9C (Nikon) light source with a numerical aperture of 0.50 NA. The post-exposure bake (PEB) and development processes were performed by a Clean Track Mk-Vz (Tokyo Electron Limited). The PEB process was carried out at 110 °C for 90 seconds. Thereafter, the photoresist layer was paddle-developed with a 2.38 wt% aqueous TMAH developer (MFTM CD-26, DuPont Electronics & Industrial) for 80 seconds. After development, the substrate was rinsed with water and spin-dried. The term "paddle development" typically refers to a specific development technique used in photoresist processing. Paddle development involves the developer accumulating or forming a "liquid pool" on the surface of the photoresist during the development process.

[0079] The stability of the pattern width against fluctuations in the focus position and energy intensity during the mask exposure process (focus-exposure matrix = FEM) of the lithography process was evaluated using a 1.2 μm trench mask. The aim was to evaluate pattern widths 100 nm narrower than the nominal size and focus on the under-exposure process window. The process window was quantified as the focus margin providing a 5% exposure margin corresponding to fluctuations of ±10% from the target pattern size (1210 nm to 990 nm). The calculations were performed using ProData software by KLA-TENCOR.

[0080] Table 2 shows the results of the lithography tests and process window evaluations. To evaluate the effects of analogs of nonionic oxime compounds and nonionic thioxanthone compounds, their addition amounts are shown as relative values to the molar amount of PAG as shown in Table 2.

[0081] [Table 1]

[0082] [Table 2]

[0083] Effect of thioxanthone addition to the photoresist composition The influence of thioxanthone additives in a photoresist composition was evaluated by a) using them individually in the form of a single additive (ITX) in an amount suitable for reducing footing on a copper substrate; or b) adding them in the form of two different additives (ITX and DETX) by dividing the total amount used in a). The thioxanthone addition effects on the unexposed film thickness loss (UFTL) (lower graph), the energy up to -100 nm bias with respect to the nominal mask size (middle graph), and the process window at a mask bias of nominal 1200 nm to -100 nm (upper graph) are shown graphically. As shown in Figure 2, the use of nonionic thioxanthone compounds decreased the unexposed film thickness loss (UFTL) and the sensitivity decreased. This tendency persisted when comparing different types of thioxanthone (ITX and DETX) or different additives (benzotriazole and trithiocyanuric acid). In particular, benzotriazole, which acts as a weak base in iCAR, showed a slower sensitivity (Eop, energy with respect to the nominal mask size, 1200 nm).

[0084] Figures 3A and 3B show the variation of the pattern space width with respect to the focus position and exposure energy, represented by the Bossung curve. Figure 3A shows the Bossung curve of a photoresist composition without ITX (photoresist composition CF-7 in Table 1), and Figure 3B shows the curve of a photoresist composition containing ITX (photoresist composition EX-5 in Table 1). The exposure tool uses "msec" as the unit of exposure energy. This is the exposure time, 1 / 2 mJ / cm 2is approximately equal to. The Bossung curve, also known as the focus-exposure matrix or process window, is a graphical representation used in lithography to analyze the performance of the photolithography process. It shows how the critical dimension (CD) (such as line width) of a pattern changes in response to changes in both the focus position and exposure energy during the lithography exposure process. The x-axis of the Bossung curve typically represents the focus position and indicates the position of the photoresist layer perpendicular to the focal plane of the imaging system. The y-axis represents the exposure energy, which is the amount of light or other radiation used during exposure. The Bossung curve helps to determine the optimal conditions for generating a pattern of the target dimension. The addition of ITX (Figure 3B based on EX-5) narrowed the variation in pattern width with respect to variations in both exposure energy and focus position compared to the composition without ITX (Figure 3A based on CF-7). In other words, the pattern width tends to stabilize with an increase in exposure energy when compared to an equivalent comparative composition (CF-7) containing the same components but without ITX (for the photoresist composition containing ITX (EX-5)).

[0085] Figures 4A and 4B show examples of process window plots using a nominal mask size of 1200 nm. Figure 4A shows the process window (PW) of the focus-exposure matrix of Comparative Example CF-7 (without ITX) aimed at achieving a space width of 1.1 μm using a nominal mask of 1.2 μm. Figure 4B shows the process window (PW) of the focus-exposure matrix of Example EX-5 (with ITX) aimed at achieving the same space width using the same nominal mask. The process window is designed with a 5% exposure margin that allows a ±10% variation in pattern size with respect to the target size. As previously shown in Figure 3B, the pattern width tends to stabilize with an increase in exposure energy when compared to an equivalent comparative composition (CF-7) containing the same components but without ITX (for the photoresist composition (EX-5) containing ITX). In this evaluation, the process window is determined at low exposure energy, resulting in a bias of -100 nm from the nominal mask size (1200 nm) to 1100 nm. A ±10% allowable range of pattern width with respect to the target size is considered, and the exposure margin is calculated for each focus offset. This is defined as the ratio of the difference between the exposure energy for a +10% pattern size (E+10%, 1210 nm = 1100 nm × 110%) and the exposure energy for a -10% pattern size (E-10%, 990 nm) to the energy for the target size (E-100 nm bias, 1100 nm).

Number

[0086] In this evaluation, the focus range that provides a 5% EL margin is used as the process window. Surprisingly, when a nonionic thioxanthone compound is added, the process window tends to become wider. For example, CF7 and EX5 have the same formulation except for the nonionic thioxanthone compound. As shown in the plot, the addition of ITX results in more stable critical dimension (CD) variations with respect to both exposure energy and focus position (offset). EX5 provides a process window of 0.96 μm by maintaining pattern width variations within ±10% compared to undersize (see the elliptical region in Figure 4B). This represents an almost two-fold improvement in the process window compared to baseline CF7 (0.49 μm) (see the elliptical region in Figure 4A).

[0087] Effect of Oxime Addition to Photoresist Compositions The lithography performance of the nonionic oxime additives ethanone (1-(2-naphthalenyl)-, O-(2-phenylacetyl)oxime) (oxime-A) and (9H-fluoren-9-one, O-(2-phenylacetyl)oxime) (oxime-B) was evaluated in a photoresist composition. The test results in Table 2 show that the addition of nonionic oxime compounds increases the process window regardless of the presence or absence of the addition of nonionic thioxanthone compounds.

[0088] Figure 5 shows a series of graphs indicating the effect of oxime compounds on the unexposed film thickness loss (UFTL) (lower plot), sensitivity (energy up to -100 m bias, middle plot), and process window (PW - 100 nm bias, upper plot) for a photoresist composition containing an oxime additive. Figure 5 shows the data for EX-5, EX-11, EX-12, EX-14, and EX-19 in Table 2.

[0089] Figure 5 shows that a photoresist composition containing an increased amount of a nonionic oxime compound (such as oxime A) exhibits a decreased amount of UFTL. This trend is similar to the trend observed when a nonionic thioxanthone compound is incorporated into the photoresist composition (see Figure 2). Furthermore, by introducing a nonionic oxime compound beyond the baseline formulation that already contains a nonionic thioxanthone compound, the process window was further expanded.

[0090] Example 2 The effects of nonionic thioxanthone compounds and nonionic oxime compounds on dry etching resistance were evaluated. The process conditions and plasma etching conditions are detailed in Tables 4 and 5, respectively. Table 6 (shown in Figure 6) represents the wafer appearance after plasma etching and the corresponding cross-sectional SEM images.

[0091] From Table 6, it can be seen that sample CF-7 (see Table 1) which contains neither thioxanthone (ITX) nor oxime compound (oxime A) shows swelling on the surface. When either ITX or oxime-A is added, the number and size of these swellings decrease, resulting in a significant improvement. When the cross-section is examined with a scanning electron microscope (SEM), small circular voids are observed, and their size decreases as they approach the photoresist surface. When ITX or oxime-A is introduced, the size and thickness of the void distribution from the surface further decrease.

[0092] [Table 3]

[0093] [Table 4]

[0094] Although not limited to theory, the blisters (observed in comparative sample CF-7) are thought to be an aggregate of small voids generated by gas evolution from acid-labile polymers in the photoresist. During plasma etching, UV emission is thought to play an important role in the generation of photoacid from a photoacid generator (PAG). This photoacid is thought to decompose acid-labile groups and act as a gas evolution source.

[0095] As demonstrated above, both nonionic thioxanthone (ITX) and oxime compound (oxime-A) contribute to a wider process window, particularly in the under-exposure region. Both approaches lower the UFTL and slow down the sensitivity. The slower the sensitivity, the more controllable the exposure process can be, enabling more accurate pattern development.

Explanation of symbols

[0096] 100 Substrate 102 First layer 106 Photoresist layer 108 Activating radiation 110 Photomask

Claims

1. A photoresist composition comprising: a nonionic thioxanthone compound, a nonionic oxime compound, or a combination of a nonionic thioxanthone compound and a nonionic oxime compound; a polymer containing a first repeating unit of formula (3) and a second repeating unit of formula (4a); 【Chemical 1】 (In formula (3), R １ is a hydrogen atom or a substituted or unsubstituted C １ -C ３ alkyl group, Z is a non-hydrogen substituent containing an acid-labile site, in formula (4a), a is an integer from 1 to 5, and Z ２ is a hydrogen atom or a substituted or unsubstituted C １ -C ５ alkyl group); and a basic deactivator; a photoacid generator; and a solvent The photoresist composition containing these.

2. The photoresist composition according to claim 1, wherein the nonionic thioxanthone compound has the structure of formula (6). [Chemical Formula 2] (In the formula, R is a non-hydrogen substituent, and each T is independently a hydrogen atom, a substituted or unsubstituted C １～５ alkyl, amino, mercapto, or hydroxyl, and each m is independently an integer of 0 to 4).

3. Each T is, independently, a hydrogen atom or a substituted or unsubstituted C １～３ alkyl group, the photoresist composition according to claim 2.

4. The photoresist composition according to any one of claims 1 to 3, wherein the nonionic thioxanthone compound is 2-isopropylthioxanthone, diethylthioxanthone, or a combination thereof.

5. The photoresist composition according to claim 1, wherein the nonionic oxime compound has formula (7A). 【Chemical Formula 3】 (In formula (7A), R ２１ is a hydrogen atom, a substituted or unsubstituted C １～２０ alkyl, a substituted or unsubstituted C ３～２０ cycloalkyl, a substituted or unsubstituted C ２～２０ alkenyl, a substituted or unsubstituted C ６～３０ aryl, a substituted or unsubstituted C ３～３０ heteroaryl, a substituted or unsubstituted C ７～２０ arylalkyl, a substituted or unsubstituted C ４～２０ heteroarylalkyl, or a combination thereof, and R ２１ may optionally contain a -C(O)- group bonded to the O atom; R ２２ and R ２３ are each independently a hydrogen atom, a substituted or unsubstituted C １～２０ alkyl, a substituted or unsubstituted C ３～２０ cycloalkyl, a substituted or unsubstituted C ２～２０ alkenyl, a substituted or unsubstituted C ６～３０ aryl, a substituted or unsubstituted C ３～３０ heteroaryl, a substituted or unsubstituted C ７～２０ arylalkyl, a substituted or unsubstituted C ４～２０ heteroarylalkyl, or a combination thereof, provided that both R ２２ and R ２３ cannot both be hydrogen atoms, and R ２２ and R ２３ may optionally be linked to each other via a single bond or a divalent linking group to form a ring).

6. R ２１ The photoresist composition according to claim 5, wherein R contains a -C(O)- group bonded to the O atom.

7. R ２２ and R ２３ The photoresist composition according to claim 5 or 6, wherein R and R are linked to each other via a single bond or a divalent linking group to form a ring.

8. The photoresist composition according to any one of claims 1 to 7, wherein the photoacid generator is selected from N-hydroxynaphthalimide trifluoromethanesulfonate, N-hydroxynaphthalimide perfluoro-1-butanesulfonate, N-hydroxynaphthalimide camphor-10-sulfonate, N-hydroxynaphthalimide 2-trifluoromethylphenylsulfonate, N-hydroxy-5-norbornene-2,3-dicarboximide perfluoro-1-butanesulfonate, N-(trifluoromethylsulfonyloxy)phthalimide, and N-hydroxysuccinimide perfluorobutanesulfonate.

9. The photoresist composition according to any one of claims 1 to 8, wherein the basic deactivator is selected from N-diethyldodecanamide, 2,8-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (trager base), 1,1-dimethylethyl 4-hydroxypiperidine-1-carboxylate, N-allylcaprolactam, ethyl-3-(morpholino)propionate, 4-(p-tolyl)morpholine, or a combination thereof.

10. A pattern formation method comprising: providing a substrate; forming a photoresist formed from the photoresist composition according to any one of claims 1 to 9 on the substrate; patternwise exposing the photoresist layer to actinic radiation; and Contacting the photoresist layer with a developer to thereby form a photoresist pattern; A method comprising.

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