Photoresist components and methods of forming photoresist patterns and acid cleavable copolymers

Abstract

The present disclosure provides a photoresist composition and a method of forming a photoresist pattern and an acid cleavable copolymer. The photoresist component includes an acid cleavable copolymer formed from oligomers in the backbone or side arms of the copolymer. Each oligomer includes an acid labile group, a first comonomer having an acid leaving substituent, and at least one of a second comonomer having a hydrogen donating substituent or a third comonomer having a polar substituent. The copolymer may also include a reversible addition fragmentation chain transfer agent. Upon exposure of the photoresist component to radiation, an acid may be generated to cleave the copolymer. This can improve the line edge roughness of the photoresist layer and maintain good coating properties.

Description

Technical Field

[0001] The present disclosure relates to a photoresist layer, and more particularly to a photoresist layer material and a lithography method thereof. Background Art

[0002] Integrated circuits are formed on semiconductor wafers. A photolithography patterning process uses ultraviolet light to transfer the desired mask pattern to a photoresist on the semiconductor wafer. An etching process can then be used to transfer the pattern to the underlying layer of the photoresist. This process is repeated multiple times using different patterns to build up different layers on the wafer substrate and produce a usable device.

[0003] In order to obtain smaller feature sizes, a high-resolution lithography process is required. An example of such a process is extreme ultraviolet (EUV) lithography, which uses wavelengths of about 10 nanometers (nm) to about 100 nanometers. This process needs to be further improved. Summary of the invention

[0004] According to some embodiments of the present disclosure, a method for forming a photoresist pattern includes the following steps: coating a substrate with a photoresist composition including an acid-cleavable copolymer to form a photoresist layer; exposing the photoresist layer to radiation to form a patterned photoresist layer, wherein the exposure releases an acid to cause the backbone or side arm of the acid-cleavable copolymer to cleave; optionally performing a post-exposure bake on the coated substrate; developing the patterned photoresist layer using a developer; and optionally hard baking the patterned photoresist layer.

[0005] According to some embodiments of the present disclosure, a photoresist composition includes an acid-cleavable copolymer, a photoacid generator, and a quencher, wherein the acid-cleavable copolymer has a plurality of acid-labile groups in a main chain or a side arm.

[0006] According to some embodiments of the present disclosure, a method for forming an acid-cleavable copolymer comprises the following steps. A covalent bond is formed between a reversible addition-fragmentation chain transfer initiator and a molecule having an acid-labile group to obtain an intermediate product. A reversible addition-fragmentation chain transfer polymerization reaction is performed using the intermediate product, a first comonomer, and at least one of a second comonomer or a third comonomer to obtain an acid-cleavable copolymer. The first comonomer has an acid-leaving substituent, the second comonomer has a hydrogen-donating substituent, and the third comonomer has a polar substituent. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] When read in conjunction with the accompanying drawings, various aspects of the present disclosure can be best understood from the following detailed description. It should be noted that, in accordance with standard methods in the industry, various features are not drawn to scale. In fact, the size of various features may be arbitrarily increased or reduced for clarity of discussion.

[0008] Figure 1 is a list of acid-labile groups and their degradation products;

[0009] Figure 2 A flow chart of a method for forming an acid-cleavable copolymer is shown according to some embodiments;

[0010] Figure 3 A first exemplary embodiment of synthesizing the acid-cleavable copolymer of the present disclosure is shown;

[0011] Figure 4 A second exemplary embodiment of synthesizing the acid-cleavable copolymer of the present disclosure is shown;

[0012] Figure 5 A third exemplary embodiment of synthesizing the acid-cleavable copolymer of the present disclosure is shown;

[0013] Figure 6 A fourth exemplary embodiment of synthesizing the acid-cleavable copolymer of the present disclosure is shown;

[0014] Figure 7 A fifth exemplary embodiment of synthesizing the acid-cleavable copolymer of the present disclosure which is a star copolymer is shown;

[0015] Figure 8 is a schematic diagram of an acid-cleavable copolymer of the present disclosure, the acid-cleavable copolymer comprising two to five different monomers, a reversible addition-fragmentation chain transfer agent, and an acid-labile group in the polymer backbone;

[0016] Fig. 9 A flow chart of a method for preparing a patterned photoresist layer and etching a layer of a semiconductor device is depicted according to some embodiments;

[0017] Fig. 10A It's the beginning Fig. 9 A cross-sectional view of a substrate before the method;

[0018] Fig. 10B is a cross-sectional view of a substrate having a first material layer on the substrate, also at the beginning Fig. 9 Before the method;

[0019] Fig. 10C is a cross-sectional view of a substrate having two bottom layers on a first material layer, also at the beginning Fig. 9 Before the method;

[0020] Fig.11 is a cross-sectional view of a substrate having a photoresist layer above a first material layer and a surface layer above the photoresist layer;

[0021] Fig.12 is a cross-sectional view of the substrate after exposure to radiation, wherein the photoresist layer includes soluble regions and insoluble regions;

[0022] Fig.13is a cross-sectional view of a substrate after development, wherein the photoresist layer is patterned;

[0023] Fig.14 is a cross-sectional view of a final structure having a patterned first material layer;

[0024] Fig.15 is a schematic diagram of an EUV lithography system for exposing a photoresist layer to EUV radiation according to some embodiments.

[0025]

Explanation of symbols

[0026] 100: Method

[0027] 102,104,106:Step 110:Method

[0028] 112,115,120,122,130,132,140,150,160,170:Step 200:Substrate

[0029] 202: First material layer

[0030] 204,206: Bottom layer

[0031] 210: Photoresist layer

[0032] 212: Soluble area

[0033] 214: Insoluble region

[0034] 215:Thickness

[0035] 800: System

[0036] 840: Extreme Ultraviolet Light Source

[0037] 850: Irradiation platform

[0038] 852: Field Faceted Mirror

[0039] 854: Steering Mirror

[0040] 860: Photomask

[0041] 862: Protective film

[0042] 870: Projection Optical Module

[0043] 872,874: Lenses

[0044] 880: Wafer Platform DETAILED DESCRIPTION

[0045] In order to realize the different features of the mentioned subject matter, the following disclosure provides many different embodiments or examples. Specific examples of components, configurations, etc. are described below to simplify the present disclosure. Of course, these are merely examples and are not restrictive. For example, in the following description, forming a first feature on or above a second feature may include an embodiment in which the first feature and the second feature are formed in direct contact, and may also include an embodiment in which an additional feature is formed between the first feature and the second feature so that the first feature and the second feature may not be in direct contact. In addition, the present disclosure may repeat reference numbers and / or letters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself represent the relationship between the various embodiments and / or configurations discussed.

[0046] Furthermore, spatially relative terms, such as "below," "beneath," "lower," "above," "upper," and the like, may be used herein to facilitate describing one element or feature's relationship to another element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0047] The numerical values ​​in the present disclosure and patent application range should be understood to include the same numerical values ​​when reduced to significant figures and the numerical values ​​whose difference from the numerical values ​​is less than the experimental error of the known measurement technology type described in the present disclosure to determine the data. All ranges disclosed herein include the described endpoints.

[0048] The term "about" can be used to include any numerical value that fluctuates without changing the basic function of the numerical value. When "about" is used for a range, "about" also discloses the range defined by the absolute values ​​of the two end points, for example, "about 2 to about 4" also discloses the range of "2 to 4". The term "about" can represent plus or minus 10% of the number.

[0049] Some embodiments of the present disclosure relate to structures made of different layers. When the terms "on" or "above" are used to describe the relationship between two different layers (including a substrate), it only means that one layer is on or above the other layers. These terms do not specify that the two layers are in direct contact with each other, and allow other layers to be located between the two layers. For example, all layers of a structure can be considered to be "on" a substrate, even if not all of these layers are in direct contact with the substrate. The term "directly" can be used to indicate that two layers are in direct contact with each other without any layer located between them. In addition, when it is indicated that a process step is performed on a substrate, it can be interpreted, depending on the context, as also performing the step on any layer present on the substrate.

[0050] As used herein, the term "copolymer" refers to a polymeric molecule derived from two or more monomers, as opposed to a homopolymer which is a molecule derived from only one monomer.

[0051] The term "monomer" refers to a molecule that can react with other monomers to form a polymer. A "repeating unit" is derived from a monomer, and the repeating unit and the monomer may differ in structure to a known degree. The two terms are used interchangeably.

[0052] In some embodiments of the present disclosure, the term "oligomer" is used to represent a group of monomers that react together. Multiple oligomers are joined together to form a polymer. It should be noted that this is different in some respects from previous usage, where oligomers and polymers are different from each other based on length.

[0053] The term "alkyl" represents a radical consisting entirely of carbon atoms and hydrogen atoms and is fully saturated (i.e., having no double or triple bonds). Alkyl radicals can be linear, branched, or cyclic. Alkyl radicals can be bonded to one or two other atoms, depending on the context in which the alkyl radical is used. For example, both methyl (-CH3) and methylene (-CH2-) should be considered alkyl radicals. As used herein, alkyl radicals contain 1 to 8 carbon atoms. Alkyl radicals can be substituted.

[0054] The term "aryl" represents an aromatic radical consisting entirely of carbon atoms and optionally hydrogen atoms along the free radical periphery. As used herein, an aromatic group has 6 to about 18 carbon atoms. The term "aryl" should not be construed to include substituted aromatic radicals, such as a methylphenyl group (7 carbon atoms). Aromatic radicals can be bonded to one or two other atoms, depending on the context in which the aromatic radical is used. For example, phenyl (-C6H5) and phenylene (phenylene,-C6H4-) should both be considered aromatic radicals. Aryl radicals can be substituted.

[0055] The term "carbonyl" represents a free radical of formula -CO- in which a carbon atom is bonded to two other carbon atoms.

[0056] The term "ether" refers to a free radical of the formula -O-, in which an oxygen atom is bonded to two other carbon atoms.

[0057] The term "ester" represents a free radical of the formula -CO-O-, in which a carbon atom and an oxygen atom are each bonded to another carbon atom.

[0058] The term "amide" refers to a free radical having the chemical formula -CO-NH-.

[0059] The term "acetal" refers to a group having the chemical formula -O-CR 1 R 2 -O- free radical, where R 1 is an alkyl group or a substituted alkyl group, and R 2 is one of hydrogen, alkyl or substituted alkyl.

[0060] The term "imine" represents a radical of the formula -N=CR-, wherein R is hydrogen, alkyl, or substituted alkyl.

[0061] The term "hydrazone" represents a free radical of the formula -NH-N=CR-, wherein R is hydrogen, alkyl or substituted alkyl.

[0062] The term "oxime" represents a radical of the formula -ON=CR-, wherein R is hydrogen, alkyl or substituted alkyl.

[0063] The term "dithioester" represents a free radical having the chemical formula -C(=S)-S-.

[0064] The term "trithiocarbonate" represents a radical having the formula -SC(=S)-S-.

[0065] The term "dithiocarbamate" refers to a radical of the formula -NR-C(=S)-S-, wherein R is alkyl, substituted alkyl, aryl or substituted aryl.

[0066] The term "xanthate" represents a free radical having the chemical formula -OC(=S)-S-.

[0067] The term "carboxyl" represents a free radical of the formula -CO-OR", wherein R" is hydrogen, alkyl, substituted alkyl or a salt thereof. The carboxyl free radical is bonded through a carbon atom. It should be noted that a carbonate group (-O-CO-OR") should not be considered a carboxyl group.

[0068] The term "amine" refers to a group having the chemical formula -NR 1 R 2 The free radical, R 1 and R 2 Each is hydrogen, alkyl or substituted alkyl. This includes monosubstituted radicals (i.e., where R 2is hydrogen) and disubstituted radicals (where R 1 and R 2 Neither is hydrogen).

[0069] The term "hydroxy" represents an -OH free radical.

[0070] The term "cyano" represents a free radical having the chemical formula -CN.

[0071] The term "halogen" represents a fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) atom.

[0072] The term "acrylate" refers to a acrylate having the chemical formula H2C=CR 1 -CO-OR 2 The free radical, R 1 can be hydrogen, alkyl or substituted alkyl, and R 2 It may be hydrogen, alkyl, substituted alkyl, aryl or substituted aryl.

[0073] The term "lactone" refers to a cyclic ester.

[0074] The term "heterocyclic" denotes a cyclic radical containing at least one heteroatom, such as nitrogen, oxygen, phosphorus or sulfur.

[0075] The term "substituted" means that at least one hydrogen atom on the free radical is replaced by another functional group. An example of a substituted alkyl group is a perhaloalkyl group, in which one or more hydrogen atoms in the alkyl group are replaced by halogen atoms.

[0076] In some embodiments of the present disclosure, the term "up to X" is used to describe the quantity of a given material. This term should be interpreted as requiring the quantity of the given material to be greater than zero, or excluding the value zero.

[0077] Some embodiments of the present disclosure relate to photoresist compositions and methods of using photoresist compositions in photolithography processes to manufacture integrated circuits / semiconductor devices. In this regard, the photoresist composition is typically applied to a substrate by, for example, spin coating, and the photoresist composition may also be cured by baking. The photoresist contains a photosensitive material. A mask pattern is used to expose the desired portion of the photoresist to radiation, such as ultraviolet light or an electron beam. The photoresist is then developed using a chemical solution (also referred to as a developer). The developer removes portions of the photoresist (e.g., the exposed portion in a positive photoresist) so that the mask pattern is transferred to the photoresist layer. The patterned photoresist layer can then be used as an etching mask for a subsequent etching process to transfer the pattern to the underlying material layer.

[0078] The minimum feature size of the pattern is limited by the wavelength of light. Ultraviolet (UV) lithography uses wavelengths of 193 nanometers (nm) or 248 nanometers. Extreme ultraviolet (EUV) light, which spans wavelengths from 124 nanometers to 10 nanometers, is now used to provide small minimum feature sizes. At such wavelengths, photosensitive materials need to use light as efficiently as possible. Chemical amplification can be used to increase the efficiency of photoresists. In chemically amplified resists or chemically amplified resists (CAR), the photoresist components include a photosensitive polymer, a photoacid generator (PAG), and a quencher. After exposure to radiation, the photoacid generator generates an acid. The acid cleaves the acid leaving group (ALG) on the polymer to change the solubility of the polymer. This also generates an acid that can continue the reaction. Such a chain reaction is only terminated when the generated acid comes into contact with a base, which is also called a quencher. The balance between acid and quencher defines the fidelity of the photoresist pattern, such as whether the sidewalls of the photoresist pattern are straight. However, low radiation doses usually lead to poor line width roughness (LWR) and critical dimension uniformity (CDU) due to photon shot noise.

[0079] The photoresist composition of some embodiments of the present disclosure includes a photosensitive copolymer. The copolymer can be a linear copolymer or a star copolymer with a side arm. The copolymer includes an acid-labile unit in the main chain or the side arm of the copolymer. When the copolymer is exposed to an acid, the copolymer cleaves, and the resulting fragments have a significantly reduced molecular weight compared to the original acid-cleavable copolymer. This can balance the good coating quality at a higher molecular weight and the improved line edge roughness (LER) to offset the poor line width roughness. If necessary, the photoresist composition can further include a photoacid generator, a quencher, and a solvent.

[0080] In certain embodiments of the present disclosure, acid-cleavable copolymers can be formed from three, four, five, six or more different monomers. The copolymers are typically formed using a living polymerization process such as reversible addition fragmentation chain transfer (RAFT). Thus, in certain embodiments, the acid-cleavable copolymers are random copolymers.

[0081] In some embodiments, the acid-cleavable copolymer can be a linear copolymer containing a single main chain and a substituent, a pendant group or a side chain extending from the main chain. In other embodiments, the acid-cleavable copolymer is a star copolymer with side arms. The star copolymer is formed from a spacer core, and three or more side arms extend from the spacer core. Each side arm has the structure of a linear copolymer, and the specific order of the monomers in each side arm can be different from each other.

[0082] In some embodiments of the present disclosure, the acid-cleavable copolymer has a general structure as shown in one of the following formulas (I) to (V):

[0083]

[0084] wherein RAFT is a reversible addition fragmentation chain transfer agent (RAFT chain transfer agent); A represents an acid-labile group (ALG); L1 and L2 are linking groups, respectively; M1 is a first comonomer having an acid leaving substituent; M2 is a second comonomer having a protondonating substituent; M3 is a third comonomer having a polar substituent; PAG represents a photoacid substituent of a fourth comonomer; Q represents a quenching substituent of a fifth comonomer; x represents the molar amount of the first comonomer in the oligomer; y represents the molar amount of the second comonomer in the oligomer; z represents the molar amount of the third comonomer in the oligomer; u represents the molar amount of the fourth comonomer in the oligomer; v represents the molar amount of the fifth comonomer in the oligomer; wherein x+y+z+u+v=100%; n is the number of oligomers in the copolymer; and m is the number of side arms in the star copolymer. Again, it should be understood that the acid-cleavable copolymers are generally random copolymers and that the notations of Formulae (I) to (V) are for convenience and ease of understanding and should not be construed to mean that the copolymers need to be block copolymers.

[0085] As described above, the acid-cleavable copolymer can be formed by RAFT polymerization. Therefore, the RAFT chain transfer agent can be part of the final copolymer. The RAFT chain transfer agent can be a dithioester, a trithiocarbonate, a dithiocarbamate or a xanthate. These four structures are depicted below:

[0086]

[0087] Formula (I) and formula (II) are two different embodiments of acid-cleavable linear copolymers. In formula (I), the RAFT chain transfer agent serves as an end group of the copolymer. In formula (II), the RAFT chain transfer agent is part of an oligomer that is repeated to form the copolymer. Formula (III), formula (IV) and formula (V) are three different embodiments of acid-cleavable star copolymers. In formula (III), the RAFT chain transfer agent serves as an end group of each side arm of the copolymer. In formula (IV) and formula (V), the RAFT chain transfer agent is part of an oligomer that is repeated to form each side arm of the copolymer. These two formulas differ in the oligomer that is attached to the spacer core. As further described below, these five formulas can be generated depending on the complete structure of the reversible addition fragmentation chain transfer initiator (or RAFT initiator).

[0088] It should be noted that due to the polymerization technique, the comonomer is located between the acid labile group A and the RAFT chain transfer agent. It should be noted that in some embodiments where the RAFT chain transfer agent is a terminal group, the RAFT chain transfer agent can be removed and replaced with a different terminal group using known techniques.

[0089] In formula (I) and formula (II), the acid-labile group A is part of the main chain. In formula (III) to formula (V), the acid-labile group A is part of each side arm. When exposed to acid, the acid-labile group will cleave. In a specific embodiment, the acid-labile group in the acid-cleavable copolymer is an ester group, an amide group, an acetal group, an imine group, a hydrazone group or an oxime group. The general formula of these acid-labile groups and their degradation products is shown in Figure 1 In. Figure 1 In the above formula (A), R1 and R2 represent the remainder of the copolymer, and R3 and R4 are each hydrogen, an alkyl group or a substituted alkyl group.

[0090] exist Figure 1In the figure, two different examples of ester groups are shown. In the first example, the ester group is cleaved into a carboxylic acid and an alcohol. In the second example, the orthoester bond is cleaved to form a lactone and two alcohols. Two different examples of amide groups are also shown in the figure. In the first example, the amide group is cleaved into a carboxylic acid and an amine. In the second example, the cis-aconityl group is cleaved into an amine and a maleamidic amide. It should be noted that a ketal is a subset of an acetal in which R2 is hydrogen.

[0091] Referring back to Formula (I) to Formula (V), L1 and L2 are each linking groups. As discussed further below, forming these linking groups can be part of a polymerization process. Examples of these linking groups can include -O-, -S-, ester groups or carbonyl groups.

[0092] M1 represents a first comonomer having an acid leaving substituent. Upon exposure to an acid, the acid leaving substituent will cleave and increase the hydrophilicity of the copolymer. Such acid leaving groups are well known in the art. In some specific embodiments, the first comonomer is an alkyl acrylate or an aryl acrylate. In a more specific embodiment, the first comonomer is t-butyl acrylate, as shown in the following manner (M1-a):

[0093]

[0094] M2 represents a second comonomer having a hydrogen-donating substituent. M2 can provide a hydrogen source for the photoacid generator. In a specific embodiment, the second comonomer is styrene having one or more hydroxyl, ether, ester or carboxyl substituents. In a more specific embodiment, the second comonomer is 4-hydroxystyrene, as shown in the following manner (M2-a):

[0095]

[0096] M3 represents a third comonomer having a polar substituent. This comonomer adjusts the polarity of the overall copolymer, thereby affecting the solubility of the copolymer in the developer. In a specific embodiment, the polar substituent is a heterocyclic group, and in a more specific embodiment, the polar substituent contains one or more oxygen atoms. In a more specific embodiment, the heterocyclic group is a five-membered ring or a six-membered ring, and can be substituted with a suitable substituent. In a specific embodiment, the polar substituent is a lactone. The polar substituent can be bonded to, for example, an acrylate. A specific example illustrates the following method (M3-a):

[0097]

[0098] In some embodiments, there may be a fourth comonomer including a photoacid substituent, which is labeled PAG in Formulas (I) to (V). Monomers containing such photoacid generators are well known in the art.

[0099] Similarly, in some embodiments, there may be a fifth comonomer including a quenching substituent, which is labeled Q in Formulas (I) to (V). Monomers containing such quenching substituents are well known in the art.

[0100] It should be noted that when a specific monomer can be included in more than one of the above comonomer definitions, formulas (I) to (V) should be interpreted as the presence of different monomers. For example, a specific comonomer cannot be considered as both M1 and M2 at the same time.

[0101] The variable x represents the molar amount of the first comonomer in the oligomer; y represents the molar amount of the second comonomer in the oligomer; z represents the molar amount of the third comonomer in the oligomer; u represents the molar amount of the fourth comonomer in the oligomer; and v represents the molar amount of the fifth comonomer in the oligomer. When taken together, x+y+z+u+v=100%. In this regard, these molar amounts are determined without taking into account the molar amounts of the RAFT chain transfer agent and the acid labile group A in the oligomer, even though the RAFT chain transfer agent and the acid labile group A can be considered as comonomers.

[0102] In the acid-cleavable copolymers of formula (I) to formula (V), the first comonomer M1 is always present. In a specific embodiment, x is from about 0.15 to about 0.70, in other words, the copolymer contains from about 15 mole percent to about 70 mole percent of monomer M1. In some more specific monomers, x is from about 0.20 to about 0.50. However, other values ​​and ranges are also within the scope of the present disclosure.

[0103] In continuation, at least one of the second comonomer M2 and the third comonomer M3 is always present. The scope of consideration includes the presence of only M2, only M3, or both M2 and M3 in the copolymer. If the second comonomer M2 is present, y is at most about 0.50, in other words, the copolymer can contain up to about 50 mole percent of the monomer M2. If the third comonomer M3 is present, z is at most about 0.70, in other words, the copolymer can contain up to about 70 mole percent of the monomer M3. However, other values ​​and ranges are also within the scope of the present disclosure.

[0104] The fourth comonomer and the fifth comonomer may be optionally present. If the fourth comonomer is present, u is at most about 0.30, in other words, the copolymer may contain at most about 30 mole percent of the comonomer containing the photoacid generator. Similarly, if the fifth comonomer is present, v is at most about 0.30, in other words, the copolymer may contain at most about 30 mole percent of the monomer containing the quencher. However, other values ​​and ranges are also within the scope of the present disclosure.

[0105] In some specific embodiments of Formula (I) to Formula (V), y is 0 and z is greater than 0. In other words, the copolymer contains the first comonomer and the third comonomer.

[0106] In other specific embodiments of Formula (I) to Formula (V), z is 0, y is greater than 0, and both u and v are 0. In other words, the copolymer contains the first comonomer and the second comonomer.

[0107] In yet other specific embodiments of Formula (I) to Formula (V), z is 0, and y, u, and v are all greater than 0, and both u and v are 0. In other words, the copolymer contains the first comonomer and the second comonomer, and also contains the fourth comonomer and the fifth comonomer.

[0108] The variable n represents the number of oligomers in the copolymer. In certain embodiments, n is from 2 to about 40. Similarly, the variable m is the number of side arms in the star copolymer. In certain embodiments, m is from 3 to 12. However, other values ​​and ranges are also within the scope of the present disclosure.

[0109] In certain embodiments, the spacer core of the star copolymer can be any alkyl or aromatic group. For example, the spacer core can be a phenyl group, or can be derived from pentaerythritol (C(CH2-)4).

[0110] The preparation of acid-cleavable copolymers can use living free radical polymerization, especially RAFT polymerization. In some specific embodiments, the weight average molecular weight (weight-average molecularweight, Mw) of the acid-cleavable copolymer can be from about 2000 to about 100000. In some more specific embodiments, the weight average molecular weight is from about 10000 to about 20000. Due to the use of RAFT polymerization, the polymerization degree dispersity (polydispersity, PDI) of the acid-cleavable copolymer can be very low, and in some specific embodiments can be 1 to about 1.4. These numerical values ​​are for the copolymers before cracking. Other numerical values ​​and ranges are also within the scope of the present disclosure.

[0111] A RAFT polymerization system generally includes a free radical initiator, a monomer / comonomer, and a RAFT initiator. A solvent may also be included.

[0112] As previously mentioned, RAFT initiators include dithioesters, trithiocarbonates, dithiocarbamates, or xanthate chain transfer agents, and also include two or three additional groups, commonly referred to as R and Z groups. The R group is typically selected to be a leaving group that is well-hemolytic, thereby initiating and reinitiating polymerization reactions. The Z group is selected for its effect on the thiocarbonyl bond, where the thiocarbonyl bond is the location for the addition of monomer. Therefore, in some embodiments, the RAFT initiator may have a general structure as shown below:

[0113]

[0114] The Z group can be selected so that the monomer is added to only one side of the thiocarbonyl group. For example, the Z group can be an alkyl or aryl group. The R group typically includes an electron-withdrawing group on the alpha carbon, such as one or more alkyl groups or a cyano group.

[0115] In the RAFT initiator of some embodiments of the present disclosure, the R group also includes an active group that can form a covalent bond with a molecule having an unstable group. The molecule having an acid-labile group usually also has two active groups. Examples of active groups that can form a covalent bond include thiol (thiol, -SH), hydroxyl group (-OH), carboxyl group (-COOH, -COOR) and acyl halide (acyl halide, -COX).

[0116] Conventional free radical initiators may be used in the RAFT polymerization system. Non-limiting examples may include azobisisobutyronitrile (AIBN) and 4,4'-azobis(4-cyanovaleric acid) (ACVA).

[0117] The RAFT polymerization process to form the acid-cleavable copolymers of some embodiments of the present disclosure is generally a two-step process. Figure 2 One such method 100 is illustrated in FIG.

[0118] First, if it is desired to form a star copolymer, the spacer core is reacted with either a RAFT initiator or a molecule having an acid-labile group at step 102. Next, in the first step of the process, as shown in step 104, the RAFT initiator reacts with the molecule having an acid-labile group to form an intermediate product. Next, in the second step of the process, as shown in step 106, the intermediate product is subjected to a RAFT polymerization reaction with at least two comonomers. Figures 3 to 7 Four examples of the process are shown in FIG.

[0119] First refer to Figure 3 , the molecule (1) having an acid-labile group has two active hydroxyl groups on both sides of the acid-labile group. Here, the acid-labile group is an ester. In the first step, the molecule (1) reacts with a RAFT initiator (2) having only one active group to form a covalent bond, and the active group of the RAFT initiator (2) is either a carboxyl group or an acid halide. The resulting intermediate (3) includes two RAFT chain transfer agents (indicated in a dotted box) on both sides of the acid-labile group (indicated in a dotted box).

[0120] In the second step, the intermediate product (3) is reacted with three comonomers M1, M2 and M3. These comonomers may be added to any RAFT chain transfer agent in amounts indicated as x1, y1, z1, x2, y2, z2, where x1+x2=x; y1+y2=y; and z1+z2=z, x, y, z being as defined above with respect to formula (I) to (V). The resulting acid-cleavable copolymer (4) thus contains one acid-labile group, and the RAFT chain transfer agent may be considered as a terminal group. As an example, if the copolymer (4) has a molecular weight of 10,000 before exposure to radiation, then after exposure the copolymer may be split into two fragments each having a molecular weight of about 5,000.

[0121] Reference to Figure 4 , molecule (5) has two acid-labile groups on both sides of the phenyl group, and also has two active hydroxyl groups on the acid-labile groups on both sides. In the first step, molecule (5) reacts with a RAFT initiator (6) which also has only one active group. The resulting intermediate (7) includes two RAFT chain transfer agents (indicated in the dotted box) on both sides of the two acid-labile groups (indicated in the dotted box).

[0122] In the second step, the intermediate product (7) is reacted with three comonomers M1, M2 and M3. These comonomers may be added in the presence of any RAFT chain transfer agent. The acid-cleavable copolymer (8) thus produced contains two acid-labile groups. Likewise, the RAFT chain transfer agent may be considered as a terminal group. If the copolymer (8) has a molecular weight of 10,000 before exposure to radiation, then after exposure the copolymer may be split into three fragments. Two of the fragments containing the comonomers may have a molecular weight of less than 5,000. The third fragment may include a phenyl group and may have a molecular weight of about 132 g / mol.

[0123] Reference to Figure 5 , a molecule (1) having an acid-labile group is reacted with a RAFT initiator (9) having two reactive groups. Thus, the intermediate product (10) itself can be considered an oligomer, wherein n is 2 to about 40. Then, in a second step of adding a comonomer, the molecular weight of the oligomer increases. In this example, the resulting copolymer (11) includes n acid-labile groups. The copolymer (11) also includes n RAFT chain transfer units. If the copolymer (8) has a molecular weight of 10,000 before exposure to radiation and consists of 10 oligomers (n=10), then after exposure the copolymer can be split into 10 fragments, each having a molecular weight of about 1,000.

[0124] It should be noted that when the molecule (1) and the RAFT initiator (9) each have two reactive groups, either the molecule (1) or the RAFT initiator (9) in the star polymer can be bonded to the spacer core. The object bonded to the spacer core can be controlled by first exposing the spacer core to the molecule (1) or first exposing the spacer core to the RAFT initiator (9). These two options are illustrated in the above formula (IV) and formula (V).

[0125] Reference to Figure 6 , a molecule (1) having an acid labile group reacts with a RAFT initiator (12) having two reactive groups to form an intermediate (13). In this particular embodiment, the RAFT initiator (12) has electron withdrawing substituents on the alpha carbons on either side of the thiocarbonyl group. Thus, in the second step, comonomers can be added on either side of the RAFT chain transfer agent as shown, although only two comonomers M1 and M2 are shown in the figure.

[0126] Figure 7 is an example of a star copolymer. Figure 2The spacer core (15) is labeled with the letter R, and the number of side arms of the star copolymer is labeled with the variable m. The molecule (16) having an acid labile group is depicted as an acetal. The spacer core (15) reacts with the molecule (16) to form a first intermediate product (17). Next, a RAFT initiator reacts with the acid labile group of the first intermediate product (17) to obtain a second intermediate product (18). In the second step of adding comonomer, the molecular weight of each side arm increases. In this schematic, the acid labile group is attached to the spacer core, and the RAFT chain transfer agent acts as a terminal group of each side arm. The resulting copolymer (19) includes m acid labile groups. The copolymer (19) also includes m RAFT chain transfer units. If the copolymer (19) has a molecular weight of 6000 before exposure to radiation and has six oligomeric side arms (m=6), then after exposure the copolymer can be split into seven fragments. The six fragments can correspond to the side arms, each fragment having a molecular weight of less than 1000. The seventh fragment can include the spacer core.

[0127] Figures 3 to 7 The copolymer of does not depict the fourth comonomer or the fifth comonomer. Figure 8 is a schematic diagram of a copolymer including a fourth comonomer (having a PAG side group) and a fifth comonomer (having a Q side group). In this schematic diagram, the linking group L2 includes an electron withdrawing substituent that activates the thiocarbonyl group to direct the site of comonomer addition.

[0128] In certain embodiments, the acid-cleavable copolymer is a positive-tone photoresist, which can be photosensitive and degrade upon exposure to radiation. Thus, the developer will dissolve the exposed areas.

[0129] The acid-cleavable copolymer is a component of the photoresist composition. Other components of the photoresist composition may include a photoacid generator, a quencher and a solvent. If the acid-cleavable copolymer does not include a fourth comonomer or a fifth comonomer, the photoresist composition may include a photoacid generator and a quencher, respectively. Other optional additives may also be present in the photoresist composition, such as a surfactant, a sensitizer, a crosslinker, a stabilizer, a dissolution inhibitor, a plasticizer, a colorant, an adhesion promoter and / or a surface leveling agent.

[0130] Non-limiting examples of the photoacid generator may include halogenated triazine, onium salt, diazonium salt, aromatic diazonium salt, phosphonium salt, sulfonium salt, iodonium salt, imide sulfonate, oxime sulfonate, diazodisulfone, disulfone, o-nitrobenzylsulfonate, sulfonated ester, halogenated sulfonyloxy dicarboximide, sulfonated ester, sulfon ... dicarboximide, diazodisulfone, α-cyanooxyamine-sulfonate, imidesulfonate, ketodiazosulfone, sulfonyldiazoester, 1,2-di(arylsulfonyl)hydrazine, nitrobenzylester, s-triazine derivative, combinations thereof or the like.

[0131] Specific examples of the photoacid generator include α-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide (MDT), N-hydroxy-naphthalimide (DDSN), benzoin tosylate, t-butylphenyl-α-(p-toluenesulfonyloxy)-acetate, t-butyl-α-(p-toluenesulfonyloxy)-acetate, triarylsulfonium and diaryliodonium hexafluoroantimonate. hexafluoroantimonate, hexafluoroarsenate, trifluoromethanesulfonate, iodonium perfluorooctanesulfonate, N-camphorsulfonyloxynaphthalimide, N-pentafluorophenylsulfonyloxynaphthalimide, ionic iodine sulfonates such as diaryliodonium (alkyl or aryl) sulfonate and bis-(di-t-butylphenyl)iodonium camphanylsulfonate.iodoniumsulfonate, perfluoroalkanesulfonate such as perfluoropentanesulfonate, perfluorooctanesulfonate or perfluoromethanesulfonate, aryltriflate such as triphenylsulfoniumtriflate or bis-(t-butylphenyl)iodoniumtriflate, pyrogallol derivative such as trimesylate of pyrogallol, trifluoromethanesulfonate ester of hydroxyimide, α,α'-bis-sulfonyl-diazomethanes, sulfonate esters of nitro-substituted benzyl alcohols. of nitro-substituted benzyl alcohol), naphthoquinone-4-diazides, ethanone and alkyl disulfone.

[0132] The quencher can be used to suppress the diffusion of the generated acid within the photoresist, thereby improving the photoresist stability and improving the photoresist pattern configuration. Non-limiting examples of quenchers include amines and organic acids. The amine can be a second lower aliphatic amine or a tertiary lower aliphatic amine. Specific examples of amine quenchers include trimethylamine, diethylamine, triethylamine, di-n-propylamine, tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, and other alkanolamines.

[0133] Examples of organic acids that can be used as quenchers may include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid, phosphoric acid and its derivatives (e.g., phosphoric acid di-n-butyl ester or phosphoric acid diphenyl ester), phosphonic acid and its derivatives (e.g., phosphonic acid dimethyl ester, phosphonic acid di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester or phosphonic acid dibenzyl ester), and phosphinic acid and its derivatives (e.g., esters thereof or phenylphosphinic acid).

[0134] The plurality of components are mixed or blended together in a solvent to form a photoresist composition. In a specific embodiment, the solvent is an organic solvent. Examples of suitable organic solvents include propylene glycol monomethyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), and a mixture of PGME and PGMEA (commercially known as OK73). Other examples include ketones, alcohols, polyalcohols, ethers, glycol ethers, cyclic ethers, aromatic hydrocarbons, esters, propionates, lactates, lactic esters, akylene glycol monoalkyl ethers, akyl lactates, akyl alkoxypropionates, cyclic lactones, monoketone compounds containing a ring, akylene carbonates, akyl alkoxyacetates, akylpyruvates, lactate esters, ethylene glycol akyl ether acetates, diethylene glycol, propylene glycol akylether acetates, akylene glycol akyl ether esters, ester), akylene glycol monoakyl ester or the like.

[0135] The surfactant may be present in the photoresist composition. After the photoresist layer is developed, the surfactant may facilitate the removal of residues from the photoresist layer. The surfactant may be an alkyl cationic surfactant, an amide quaternary cationic surfactant, an ester quaternary cationic surfactant, an amine oxide surfactant, a betaine surfactant, an alkoxylate surfactant, a fatty acid ester surfactant, an amide surfactant, an alcohol surfactant, an ethylenediamine surfactant, or a fluorine-containing and / or silicon-containing surfactant.

[0136] The sensitizer may be present in the photoresist composition. After exposure to radiation, the sensitizer is designed to produce radiation of different wavelengths so that the sensitivity of the photoresist material is substantially improved. In some embodiments, the sensitizer may include fluorine, metal, or phenol groups. For example, the sensitizer may be polyhydroxystyrene (PHS) or polyfluorostyrene. Other sensitizers with high electron-beam cross sections may also be used, such as organic iodides, bromides, chlorides, or magnesium-containing compounds.

[0137] Crosslinking agents may also be added to the photoresist composition. The crosslinking agent may react with the copolymer after exposure to help increase the crosslinking density of the photoresist, thereby helping to improve the photoresist pattern and etch resistance. Examples of crosslinking agents may include melamine, urea, glycoluril compounds, aliphatic hydrocarbons having hydroxyl or thiol or hydroxyalkyl groups, alcohols, and etherified amino resins.

[0138] Stabilizers may be included in the photoresist composition. Stabilizers reduce the diffusion of acids generated by the photoresist composition during exposure. Examples of stabilizers include nitrogen-containing compounds such as primary / secondary / tertiary aliphatic amines, cyclic amines such as piperidine / pyrrolidine / morpholine, aromatic heterocycles such as pyridine / pyrimidine / purine, imines, guanidines, imides, amides, ammonium salts, cationic nitrogen-containing compounds, phenolates, carboxylates, aryl and alkyl sulfonates, sulfonamides, and the like.

[0139] Dissolution inhibitors may be included in the photoresist composition to help control the dissolution of the photoresist during development. Non-limiting examples of dissolution inhibitors include cholic acid, deoxycholic acid, lithocholic acid, t-butyl deoxycholate, t-butyl lithocholate, and t-butyl-3-α-acetyllithocholate.

[0140] Plasticizers can be used in photoresist compositions to reduce delamination and cracking between the photoresist and the layer beneath the photoresist. Examples of plasticizers can include monomeric, oligomeric, and polymeric plasticizers, such as oligo- and polyethylene glycol ethers, cycloaliphaticesters, and non-acid reactive steroidally derived materials. Specific examples of materials that can be used for plasticizers include dioctyl phthalate, didodecylphthalate, triethylene glycol dicaprylate, dimethyl phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, triacetylglycerine, and the like.

[0141] If necessary, a colorant can be used to help locate defects in the photoresist. A wide range of colorants include dyes and pigments. More specific examples of colorants can include triarylmethane dyes, crystal violet, methyl violet, ethyl violet, malachite green, diamond green, phthalocyanine pigments, azo pigments, carbon black, titanium oxide, benzophenone compounds, salicylic acid compounds, phenylacrylate compounds, coumarin compounds, thioxanthone compounds, stilbene compounds, naphthalene dicarboxylic acid compounds, azo dyes, and the like.

[0142] Adhesion promoters can be used in the photoresist composition to promote adhesion between the photoresist and the layer below the photoresist. Examples of adhesion promoters include silane compounds having at least one reactive substituent, such as a carboxyl group, a methacryloyl group, an isocyanate group, and / or an epoxy group.

[0143] A surface leveler may be additionally added to the photoresist composition to planarize the top surface of the photoresist layer. Examples of surface levelers include fluoroaliphatic esters, hydroxylterminated fluorinated polyethers, fluorinated ethylene glycol polymers, silicones, and acrylic polymer levelers.

[0144] The photoresist composition is used to form a photoresist layer, which is used in a variety of processes to form a variety of structures in an integrated circuit or semiconductor device. Fig. 9 One such method 110 for forming a photoresist pattern and patterning a material layer of a semiconductor device is shown in FIG.

[0145] First, heating the substrate may be a suitable step prior to the photoresist patterning process. This will desorb moisture present on the substrate surface and may improve photoresist adhesion, as well as thermally crack any OH bonds present on the oxidized surface. The substrate may be heated to a temperature above 100°C (e.g., up to 200°C) for several minutes. The substrate is then cooled back to room temperature.

[0146] In step 112, the photoresist composition is coated on the substrate. It should be noted that the substrate can be any type of material layer in which a pattern is desired to be formed. The coating can be completed by, for example, spin coating or spraying, roller coating, dip coating or extrusion coating. Generally speaking, in spin coating, the substrate is placed on a rotating platform (platen), wherein the rotating platform may include a vacuum chuck to hold the substrate in the platform. The photoresist composition is then applied to the center of the substrate. The speed of the rotating platform is then increased to evenly distribute the photoresist from the center of the substrate to the edge of the substrate. The rotation speed of the platform is then fixed, so that the thickness of the final photoresist layer can be controlled.

[0147] In step 115, the photoresist composition is baked or cured to remove the solvent and harden the photoresist layer. In some specific embodiments, the baking temperature is about 80° C. to about 110° C., and the baking time is about 60 seconds. The baking can be performed using a hot plate, an oven, or similar equipment.

[0148] In step 120, the photoresist layer is patterned by exposing it to radiation. The radiation can be any wavelength of light that carries the desired mask pattern, although ultraviolet radiation is commonly used today. Ultraviolet radiation has a wavelength in the range of about 10 nanometers to about 400 nanometers, such as KrF lasers (248 nanometers) or ArF lasers (193 nanometers). In certain embodiments, extreme ultraviolet light has a wavelength of about 13.5 nanometers for patterning, which can achieve smaller feature sizes. In other embodiments, electron-beam (e-beam) radiation is used. This causes some portions of the photoresist layer to be exposed to the radiation, while some portions of the photoresist are not exposed to the radiation. Such exposure can activate the acid-cleavable copolymer so that some portions of the photoresist can be dissolved in the developer, while some portions of the photoresist will not be dissolved in the developer.

[0149] An additional resist bake step (post exposure bake (PEB)) may be performed after exposure to radiation in optional step 122. This may help release acid-labile groups or other molecules that are important for chemical amplification.

[0150] In step 130, the photoresist layer is developed using a developer. The developer can be an aqueous solution or an organic solution. The soluble portion of the photoresist layer is dissolved and washed away during development to leave the photoresist pattern. An example of a common developer for positive photoresist is an aqueous solution of tetramethylammonium hydroxide (TMAH). In general, any suitable developer can be used.

[0151] In optional step 132, a post-development bake or hard bake may be performed to stabilize the photoresist pattern for optimal performance in subsequent steps.

[0152] In succession, a portion of the material layer below the photoresist pattern is now exposed. In step 140, the material layer is etched resulting in the exposed portion of the material layer being removed, thereby transferring the photoresist pattern to the material layer. In a specific embodiment, the etching is performed by dry etching.

[0153] In addition to etching the material layer, other process steps may be performed instead. For example, in an alternative step 150, ions may be implanted into the exposed material layer instead, or in an alternative step 160, a different material may be deposited on the material layer.

[0154] Finally, the photoresist layer may then be removed in step 170. For example, the photoresist layer may be removed using a variety of solvents such as N-methyl-pyrrolidone (NMP), alkaline media or other strippers at elevated temperatures, or dry etching using oxygen plasma.

[0155] FIG. 10A to FIG. 14 Draw Fig. 9 These figures provide different views for better understanding.

[0156] First refer to Fig. 10A , depicting an example of a starting state of substrate 200 prior to any process steps. The substrate is typically a wafer made of a semiconductor material. Such a material may include silicon, such as in the form of crystalline silicon or polycrystalline silicon. In alternative embodiments, the substrate may be made of other elemental semiconductors such as germanium, or may include compound semiconductors such as silicon carbide (SiC), gallium arsenide (GaAs), gallium carbide, gallium phosphide, indium arsenide (InAs), indium phosphide (InP), silicon germanium, silicon germanium carbide, gallium arsenic phosphide, or gallium indium phosphide. In a specific embodiment, the wafer substrate is silicon. As illustrated in this figure, no additional layers exist on substrate 200.

[0157] In contrast, Fig. 10BIn the embodiment, there is a first material layer 202 on the substrate 200. The first material layer can be any material that can be used in a semiconductor device or an integrated circuit. For example, the first material layer can be made of an insulating material, such as silicon dioxide (SiO2) or silicon nitride (SiN), silicon oxynitride (SiON), fluorine-doped silicate glass or other dielectric materials. As another example, the first material layer can be made of a conductive material, such as polysilicon or a metal such as aluminum, copper, titanium or tungsten. The first material layer can generally serve any function. For example, the first material layer can be a high dielectric constant dielectric layer, a gate layer, a hard mask layer, an interfacial layer, a capping layer, a diffusion / barrier layer, a dielectric layer (such as SiO2), a conductive layer (such as doped polysilicon) or some other layer. The following figures show that the first material layer exists, which is only for illustration purposes and it should be understood that the substrate can also be etched.

[0158] exist Fig. 10C In the schematic diagram, one or more underlayers are applied to the substrate before the photoresist composition is applied. In this regard, the term "underlayer" is relative to the photoresist layer, and the underlayer can represent any layer applied to the expected etching layer before the photoresist composition is applied. In other words, any layer between the expected etching layer and the photoresist layer can be considered an underlayer. In this schematic diagram, two underlayers (underlayer 204, underlayer 206) are applied on the first material layer 202.

[0159] As an example, the lower bottom layer 204 can be a bottom anti-reflective coating (BARC). When the photoresist layer is applied to a reflective substrate, light reflection from the substrate / photoresist interface may cause exposure changes, leading to critical dimension control problems. For example, light may be reflected into an area not intended to be exposed and change the desired pattern. A bottom anti-reflective coating can be applied between the substrate and the photoresist layer to minimize or eliminate such problems. Suitable examples of bottom anti-reflective coatings include amorphous carbon and a variety of organic polymers. The bottom anti-reflective coating is usually formed by spin coating, but other methods can also be used. Next, the bottom anti-reflective coating or film is baked or cured to induce a cross-linking reaction and remove the solvent, and harden the bottom anti-reflective coating. In some specific embodiments, the baking temperature is about 125°C to about 275°C. In a specific embodiment, the baking time is about 30 seconds to about 250 seconds. A hot plate or similar device can be used to perform baking.

[0160] As another example, the upper bottom layer 206 can be a hard mask layer. The hard mask layer can be formed of a dielectric material, a metal, or other suitable material. Examples of suitable dielectric materials can include silicon carbide, silicon nitride, silicon oxycarbide, or silicon oxynitride. The hard mask layer can be formed by any suitable process, such as chemical vapor deposition (CVD), low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or spin coating. The bottom anti-reflective coating and the hard mask layer are typically selected to have significantly different etching sensitivities to the same etchant. When combined with a photoresist layer, such a multi-layer photoresist pattern can also help improve line width roughness.

[0161] Now starting at Fig. 9 Step 112 and if Fig.11 As shown in FIG. 2 , a photoresist composition is applied to a substrate and a material layer such as the bottom layer 206. The photoresist composition can be applied by, for example, spin coating or spray coating, roller coating, dip coating or extrusion coating. Generally speaking, in spin coating, a substrate is placed on a rotating platform, wherein the rotating platform may include a vacuum chuck to hold the substrate in the platform. The photoresist composition is then applied to the center of the substrate. The speed of the rotating platform is then increased to evenly spread the photoresist composition from the center of the substrate to the edge of the substrate. The rotation speed of the platform is then fixed so that the thickness of the final photoresist layer can be controlled.

[0162] Then, in Fig. 9 In step 115 of Fig.11 , pre-bake the photoresist composition to remove solvents and harden the photoresist layer. This may also be referred to as a soft bake. In some specific embodiments, the pre-bake temperature is about 40°C to about 100°C, including from about 250°C to about 800°C or from about 80°C to about 110°C. The pre-bake time may depend on the thickness of the photoresist layer (greater thickness requires longer time), and in specific embodiments is from about 10 seconds to about 10 minutes. Baking may be performed using a hot plate, an oven, or similar equipment. Reference Fig.11 The photoresist layer 210 may have a thickness 215 of about 10 nanometers to about 100 nanometers. The substrate and other layers on the substrate are then cooled back to room temperature.

[0163] Continuing, in Fig. 9In step 120, the photoresist layer 210 is patterned by exposing it to radiation. The radiation can be any wavelength of light that carries the desired mask pattern. In a particular embodiment, extreme ultraviolet light has a wavelength of about 13.5 nanometers for patterning, which can achieve smaller feature sizes. In other embodiments, electron beam radiation is used. The electron beam can be characterized by an electron beam energy, which in some embodiments is in the range of about 5 kilovolts (kV) to about 200 kV. This step causes some portions of the photoresist layer to be exposed to the radiation, while some portions of the photoresist are not exposed to the radiation. Such exposure allows some portions of the photoresist to maintain the characteristic of being soluble in the developer, while other portions of the photoresist become insoluble in the developer. Now refer to Fig.12 , the photoresist layer 210 includes a soluble region 212 and an insoluble region 214. For reference, EUV and electron beam radiation exposure generally occur under vacuum.

[0164] Optionally, in Fig. 9 In step 122, a post-exposure bake is performed after exposure to radiation. The post-exposure bake step can be used to complete any cross-linking within the photoresist, or to complete any chemical amplification reactions that may occur. In addition, the post-exposure bake step can reduce mechanical stress that may have accumulated during the previous steps. In some specific embodiments, the post-exposure bake temperature is about 40°C to about 250°C, including from about 100°C to about 250°C or from about 90°C to about 150°C. The post-exposure bake duration can be in the range of about 10 seconds to about 10 minutes, and can vary depending on the thickness of the photoresist layer.

[0165] Then, in Fig. 9 In step 130, the photoresist layer 210 is developed using a developer. The developer may be applied by spin coating, spray coating, or other suitable process. During the development step, the soluble portion of the photoresist layer is dissolved and washed away to leave the patterned photoresist layer. This step may be accomplished, for example, by spin drying. The resulting structure is shown in FIG. Fig.13 As shown in this image, the soluble areas have been washed away to produce a patterned photoresist layer.

[0166] exist Fig. 9 In an optional step 132 of the present invention, a post-development bake or hard bake may be performed after development. This step is done to stabilize the photoresist pattern after development for optimal performance in subsequent steps. In some specific embodiments, the hard bake temperature is about 100° C. to about 160° C. The hard bake time may be in the range of about 1 minute to about 10 minutes and may vary depending on the thickness of the photoresist layer.

[0167] Continuing, as Fig.13As shown in FIG. 1 , a portion of the upper bottom layer 206 , the lower bottom layer 204 , and the first material layer 202 beneath the patterned photoresist layer are now exposed.

[0168] Then, in Fig. 9 In step 140, etching is performed through the patterned photoresist layer to transfer the photoresist pattern to the first material layer 202 through the bottom layer 206, the bottom layer 204 to obtain a patterned material layer. Ideally, the etchants used for the multiple layers are significantly different from each other, thereby improving the line width roughness in the first material layer. It should be understood that the patterned material layer can be either the first material layer or the substrate. In some embodiments, the first material layer is an insulating layer, and the etched pattern can be subsequently filled with a conductive material to form a circuit in this insulating layer. In other alternative embodiments, the first material layer is a conductive layer, and the etched pattern is subsequently filled with an insulating material.

[0169] Generally, these etching steps may be performed using wet etching, dry etching, or plasma etching processes, such as reactive ion etching (RIE), inductively coupled plasma (ICP), or a combination thereof, as appropriate. The etching may be anisotropic. Depending on the material, the etchant may include carbon tetrafluoride (CF4), hexafluoroethane (C2F6), octafluoropropane (C3F8), fluoroform (CHF3), difluoromethane (CH2F2), fluoromethane (CH3F), trifluoromethane (CHF3), carbon fluoride, nitrogen (N2), hydrogen (H2), oxygen (O2), argon (Ar), xenon (Xe), xenon difluoride (XeF2), helium (He), carbon monoxide (CO), carbon dioxide (CO2), fluorine (F2), chlorine (Cl2), oxygen (O2), hydrogen bromide (HBr), hydrofluoric acid (HF), nitrogen trifluoride (NF3), sulfur hexafluoride (SF6), boron trichloride (boron trichloride (BCl3), ammonia (NH3), bromine (Br2), nitrogen trifluoride (NF3), the like or combinations thereof in various ratios. For example, hydrofluoric acid and ammonium fluoride may be used to wet etch silicon dioxide. Alternatively, various mixtures of CHF3, O2, CF4, and / or H2 may be used to dry etch silicon dioxide.

[0170] In addition to etching the first material layer, other process steps may be performed instead. For example, in an alternative step 150, ions may be implanted into the exposed material layer instead, or in an alternative step 160, a different material may be deposited on the material layer.

[0171] Then, in Fig. 9 In step 170, the patterned photoresist layer 210 is removed. The bottom layer is also removed. The photoresist layer, the upper bottom layer, and the lower bottom layer can be removed using conventional means, such as plasma stripping, solvents, or chemical-mechanical planarization (CMP). The resulting structure is shown in FIG. Fig.14, wherein the first material layer 202 is patterned.

[0172] The use of acid-cleavable copolymers in photoresist compositions provides multiple advantages. Prior to exposure to radiation, the acid-cleavable copolymers have a high molecular weight, thereby improving the quality of the photoresist coating when applied to a substrate. After exposure to radiation, the copolymers cleave into fragments with significantly reduced molecular weight. This improves line edge roughness, line width roughness, critical dimension uniformity, and etch feature quality. This can also improve throughput and reduce overall cost.

[0173] Fig.15 8 is an exemplary schematic diagram, not drawn to scale, illustrating various components of an EUV lithography system that generates radiation for exposing photoresist. Generally, EUV lithography system 800 begins with an EUV light source 840 that generates EUV light or radiation. Downstream of EUV light source 840 is an illumination platform 850 that can collect the EUV light and focus it into a beam, such as by splitting the beam into multiple light channels using a field facet mirror 852. These beam channels can then be directed onto the plane of a reticle using one or more relay mirrors 854. Reticle 860 can include a pellicle membrane 862 through which the radiation can pass before and / or after contacting the reticle. Downstream of reticle 860 is a projection optics module 870 that is configured to image the pattern of the reticle onto semiconductor wafer substrate 200. The projection optical module 870 may include a refractive optical element or a reflective optical element for carrying the pattern image defined by the mask. The lens 872 and the lens 874 are used as examples in the drawings. The wafer substrate 200 is located on the wafer platform 880, and the wafer platform 880 can be moved if imaging is required. The lithography system may include other modules, or be integrated or coupled with other modules.

[0174] Additional process steps may be performed to fabricate the semiconductor device or integrated circuit. Examples of such steps may include ion implantation, deposition of other materials, etching, etc.

[0175] Thus, some aspects of the present disclosure relate to methods of forming photoresist patterns. A substrate is coated with a photoresist composition to form a photoresist layer, wherein the photoresist composition includes an acid-cleavable copolymer. The photoresist layer is exposed to radiation to pattern the photoresist layer. Exposure releases acid, resulting in cleavage of the copolymer backbone or side arms. Optionally, a post-exposure bake of the coated substrate is performed. The patterned photoresist layer is developed using a developer. Optionally, the patterned photoresist layer can be hard-baked. Etching can be performed through the patterned photoresist layer to obtain a patterned material layer on the substrate.

[0176] In some embodiments, the main chain or side arm of the acid-cleavable copolymer includes multiple oligomers, each of which includes an acid-labile group, a first comonomer with an acid-leaving substituent, and at least one of a second comonomer with a hydrogen-donating substituent or a third comonomer with a polar substituent. In some embodiments, the molar ratio of the first comonomer is about 15% to about 70% of the oligomer. If a second comonomer is present, the molar ratio of the second comonomer is up to about 50% of the oligomer. If a third comonomer is present, the molar ratio of the third comonomer is up to about 70% of the oligomer. In some embodiments, the acid-labile group is an ester, amide, acetal, imine, hydrazone or oxime. In some embodiments, the main chain or side arm of the acid-cleavable copolymer has 2 to 40 oligomers. In some embodiments, each of the oligomers further includes a reversible addition-fragmentation chain transfer agent. In some embodiments, the reversible addition-fragmentation chain transfer agent is a dithioester, a trithiocarbonate, a dithiocarbamate or a xanthate. In some embodiments, the first comonomer is an alkyl acrylate or an aryl acrylate. In some embodiments, the second comonomer is styrene having one or more hydroxyl, ether, ester or carboxyl substituents. In some embodiments, the third comonomer is an acrylate having a polar substituent. In some embodiments, the polar substituent contains one or more oxygen atoms, or the polar substituent is a lactone. In some embodiments, each of the oligomers further includes a fourth monomer having a photoacid substituent and / or a fifth monomer having a quenching substituent. In some embodiments, the molar ratio of the fourth monomer is up to about 30% of the oligomer, and / or the molar ratio of the fifth monomer is up to about 30% of the oligomer. In some embodiments, the acid-cleavable copolymer has terminal groups formed from a reversible addition-fragmentation chain transfer agent. In some embodiments, the acid-cleavable copolymer is a linear copolymer or a star copolymer.

[0177] The present disclosure also discloses a plurality of embodiments of a photoresist composition. The photoresist composition includes an acid-cleavable copolymer having an acid-labile group in the main chain or side arm of the copolymer, a photoacid generator, and a quencher. If necessary, a solvent may also be present in the photoresist composition.

[0178] In some embodiments, the acid-cleavable copolymer further comprises a first comonomer, and at least one of a second comonomer or a third comonomer. The first comonomer has an acid leaving substituent, the second comonomer has a hydrogen donating substituent, and the third comonomer has a polar substituent.

[0179] Some embodiments of the present disclosure also disclose methods for forming acid-cleavable copolymers. A covalent bond is formed between a reversible addition-fragmentation chain transfer initiator and a molecule having an acid-labile group to obtain an intermediate product. The intermediate product is then used to perform a reversible addition-fragmentation chain transfer polymerization reaction with (A) a first comonomer and (B) at least one of a second comonomer (i) or a third comonomer (ii) to obtain a copolymer. The first comonomer has an acid-leaving substituent, the second comonomer has a hydrogen-donating substituent, and the third comonomer has a polar substituent.

[0180] In some embodiments, a molecule having an acid labile group is attached to a spacer core. In some embodiments, the reversible addition fragmentation chain transfer initiator has two reactive groups such that the intermediate product is a copolymer.

[0181] Some embodiments of the present disclosure also disclose acid-cleavable copolymers. The acid-cleavable copolymers include oligomers in the main chain or side arms of the copolymer. Each oligomer includes an acid-labile group, a first comonomer having an acid-leaving substituent, and at least one of (i) a second comonomer having a hydrogen-donating substituent or (ii) a third comonomer having a polar substituent.

[0182] The features of some embodiments are summarized above so that those skilled in the art can better understand the viewpoints of the present disclosure. Those skilled in the art should understand that they can easily use the present disclosure as a basis for designing or modifying other processes and structures to achieve the same purpose and / or achieve the same advantages as the embodiments described herein. Those skilled in the art should also understand that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and various changes, substitutions and modifications can be made without departing from the spirit and scope of the present disclosure.

Claims

1. A method for forming a photoresist pattern, characterized in that: include: Coating a substrate with a photoresist composition including an acid-cleavable copolymer to form a photoresist layer; exposing the photoresist layer to radiation to form a patterned photoresist layer, wherein the exposure releases acid to cause cleavage of a backbone or a side arm of the acid-cleavable copolymer; Optionally performing a post-exposure bake on the coated substrate; developing the patterned photoresist layer using a developer; as well as The patterned photoresist layer is optionally hard baked.

2. The method according to claim 1, characterized in that wherein the backbone or the side arm of the acid-cleavable copolymer comprises a plurality of oligomers, each of the plurality of oligomers comprising: An acid-labile group; a first comonomer having an acid leaving substituent; and At least one of a second comonomer having a hydrogen donating substituent or a third comonomer having a polar substituent.

3. The method according to claim 2, characterized in that in: A molar ratio of the first comonomer is 15% to 70% of the plurality of oligomers; If the second comonomer is present, a molar ratio of the second comonomer is up to 50% of the plurality of oligomers; as well as If the third comonomer is present, a molar ratio of the third comonomer is up to 70% of the plurality of oligomers.

4. The method according to claim 2, characterized in that The acid labile group is an ester, an amide, an acetal, an imine, a hydrazone or an oxime.

5. The method according to claim 2, characterized in that Each of the plurality of oligomers further comprises a reversible addition-fragmentation chain transfer agent.

6. The method according to claim 2, characterized in that Each of the plurality of oligomers further comprises a fourth monomer having a photoacid substituent and / or a fifth monomer having a quenching substituent.

7. The method according to claim 2, characterized in that The acid cleavable copolymer is a linear copolymer or a star copolymer.

8. A photoresist component, characterized in that: include: an acid-cleavable copolymer, wherein a plurality of acid-labile groups are present in a main chain or one side arm of the acid-cleavable copolymer; a photoacid generator; and A quencher.

9. The photoresist composition according to claim 8, wherein: wherein the acid-cleavable copolymer further comprises a first comonomer, and at least one of a second comonomer or a third comonomer; The first comonomer has an acid leaving substituent, the second comonomer has a hydrogen donating substituent, and the third comonomer has a polar substituent.

10. A method for forming an acid-cleavable copolymer, characterized in that: include: forming a covalent bond between a reversible addition-fragmentation chain transfer initiator and a molecule having an acid-labile group to obtain an intermediate product; as well as Performing a reversible addition-fragmentation chain transfer polymerization reaction using the intermediate product, a first comonomer, and at least one of a second comonomer or a third comonomer to obtain the acid-cleavable copolymer; The first comonomer has an acid leaving substituent, the second comonomer has a hydrogen donating substituent, and the third comonomer has a polar substituent.

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