Photoactive polymer brush materials and EUV patterning using the same
阅读说明：本技术 光活性聚合物刷材料及使用其的euv图案化 (Photoactive polymer brush materials and EUV patterning using the same ) 是由 E.A.德希尔瓦 R.沃杰特基 D.戈尔德法布 D.P.桑德斯 N.费利克斯 于 2019-02-14 设计创作，主要内容包括：描述了光活性聚合物刷材料和使用该光活性聚合物刷材料的EUV光致抗蚀剂图案化方法。所述光活性聚合物刷材料包括可在衬底表面固定的接枝部分、干法可显影或可灰化部分、和光酸产生部分,它们结合到聚合物主链。在曝光于EUV辐射时,所述光酸产生部分在界面处产生酸,这克服了酸损耗问题从而减少光致抗蚀剂浮渣。所述光酸产生部分还可便于经由所述接枝部分的任选的酸可切断的接枝官能团将所述光活性聚合物刷材料从所述衬底切断。所述干法可显影或可灰化部分便于在化学增强EUV光致抗蚀剂的显影之后存在残余物的情况下将所述光活性聚合物刷材料从所述衬底完全去除。(Photoactive polymer brush materials and EUV photoresist patterning processes using the photoactive polymer brush materials are described. The photoactive polymeric brush material includes a graft moiety that can be immobilized on a substrate surface, a dry developable or ashable moiety, and a photoacid generating moiety that are bound to a polymeric backbone. Upon exposure to EUV radiation, the photoacid generator generates an acid at the interface, which overcomes the problem of acid loss and thereby reduces photoresist scum. The photoacid generating moiety can also facilitate cleaving of the photoactive polymer brush material from the substrate via the optional acid-cleavable grafting functionality of the grafting moiety. The dry developable or ashable portion facilitates complete removal of the photoactive polymer brush material from the substrate in the presence of residue after development of a chemically amplified EUV photoresist.)
1. A photoactive polymer brush material comprising the following repeating units:
a grafting moiety, wherein the grafting moiety comprises a grafting component selected from the group consisting of alkynes, alkenes, phosphonic acids, thiols, and silanes;
a dry developable or ashable portion; and
a photoacid generating portion, wherein the photoacid generating portion is configured to decompose and form an acid upon exposure to EUV radiation.
2. The photoactive polymer brush material of claim 1, wherein the photoacid generating moiety comprises a non-ionic photoacid that is photosensitive to the EUV radiation.
3. The photoactive polymer brush material of claim 1, wherein the photoacid generating moiety comprises an ionic photoacid that is photosensitive to the EUV radiation.
4. The photoactive polymer brush material of claim 1, wherein the photoacid generating moiety comprises a photoacid generating component selected from the group consisting of: sulfonium salts, halonium salts, α' -bissulfonyl-diazomethanes, sulfonic acid esters of imides and hydroxyimides, nitrobenzyl sulfonic acid esters, sulfonyloxynaphthalimides, pyrogallol derivatives, naphthoquinone-4-diazides, alkyl disulfones, s-triazine derivatives, and sulfonic acid generators.
5. The photoactive polymer brush material of claim 1, wherein the grafted portion is from about 5% to about 20%, the dry developable or ashable portion is from about 90 to about 60, and the photoacid generating portion is from about 5% to about 20%.
6. The photoactive polymer brush material of claim 1, wherein the dry developable or ashable portion comprises a methacrylate and/or a hexafluoroalcohol derivative.
7. The photoactive polymer brush material of claim 1, wherein the photoactive polymer brush material comprises an acrylate terpolymer of formula (I):
(I)
wherein A is a graft moiety; b is a dry developable or ashable portion; and C is a bound photoacid generator; wherein X can be selected from-H, -CH3and-CH2CH3(ii) a And wherein l is from about 5% to about 20%; m is from about 90% to about 60%, and n is from about 5% to about 20%.
8. The photoactive polymer brush material of claim 7, wherein the bound photoacid generator comprises a sulfonium salt or an iodonium salt.
9. The photoactive polymer brush material of claim 1, wherein the bound photoacid generator comprises a sulfonate ester of an imide and a hydroxyimide.
10. The photoactive polymer brush material of claim 1, wherein the grafting moiety, the dry developable or ashable moiety, and the photoacid generating moiety are attached to a carboxylic acid terminus of a polyacrylate.
11. A method of forming a relief image in a positive chemically amplified EUV photoresist comprising:
grafting a monolayer of a photoactive polymeric brush material onto a substrate, the photoactive polymeric brush material comprising a grafting moiety, a developable or ashable moiety, and a photoacid generating moiety;
applying a positive chemically amplified EUV photoresist to a monolayer of the photoactive polymer brush material;
exposing the positive chemically amplified EUV photoresist and the photoactive polymer brush material to EUV radiation to form a latent image within the chemically amplified EUV photoresist and to generate an acid at an interface between the photoresist and the substrate; and
applying a developer to the substrate to form a relief image in the chemically amplified EUV photoresist and severing at least a portion of the photoactive polymer brush material from the substrate.
12. The method of claim 11, wherein the graft moiety comprises an acid cleavable graft component that reacts with the substrate to provide self-limiting grafting of the photoactive polymer brush material to form the monolayer.
13. The method of claim 11, wherein the graft moieties comprise acid cleavable graft components that are physically adsorbed to the substrate to provide self-limiting grafting of the photoactive polymer brush material.
14. The method of claim 11, wherein the photoacid generating portion comprises a non-ionic photoacid that is photosensitive to the EUV radiation.
15. The method of claim 11, wherein the photoacid generating portion comprises an ionic photoacid that is photosensitive to the EUV radiation.
16. The method of claim 11, wherein the grafting moiety comprises a grafting component selected from the group consisting of alkynes, alkenes, phosphonic acids, thiols, hydroxyls, amines, and silanes.
17. The method of claim 11, wherein the photoactive polymer brush material comprises an acrylate terpolymer of formula (I):
(I)
wherein A is a graft moiety; b is a dry developable or ashable portion; and C is a bound photoacid generator; wherein X can be selected from-H, -CH3and-CH2CH3(ii) a And wherein l is from about 5% to about 20%; m is from about 90% to about 60%, and n is from about 5% to about 20%.
18. The method of claim 11, further comprising rinsing the monolayer of photoactive polymeric brush material with a solvent effective to remove ungrafted photoactive polymeric brush material prior to applying the positive chemically-amplified EUV photoresist to the monolayer.
19. A method of generating an acid at an interface between a substrate and a positive chemically-enhanced EUV photoresist, comprising:
grafting a monolayer of a photoactive polymeric brush material onto a substrate, the photoactive polymeric brush material comprising acid-cleavable grafted moieties, developable or ashable moieties, and photoacid-generating moieties;
applying a positive chemically amplified EUV photoresist to a monolayer of the photoactive polymer brush material; and
exposing the positive chemically amplified EUV photoresist to EUV radiation, wherein the radiation causes partial decomposition of photoacid in the photoactive polymer brush material to form an acid at an interface between the substrate and the positive chemically amplified EUV photoresist effective to reduce an amount of scum of the positive chemically amplified EUV photoresist after development thereof, as compared to exposure without the photoactive polymer brush material.
20. The method of claim 19, wherein the photoacid generating moiety comprises a photoacid generating component selected from the group consisting of: sulfonium salts, halonium salts, α' -bissulfonyl-diazomethanes, sulfonic acid esters of imides and hydroxyimides, nitrobenzyl sulfonic acid esters, sulfonyloxynaphthalimides, pyrogallol derivatives, naphthoquinone-4-diazides, alkyl disulfones, s-triazine derivatives, and sulfonic acid generators.
Technical Field
The present invention relates generally to EUV lithography, and more particularly to photoactive (photosensitive) polymer brush materials and methods of patterning EUV photoresists using the same.
Background
Photolithography is used in the manufacture of semiconductor structures, such as integrated circuits and micromechanical structures. The basic process for fabricating semiconductor structures involves modifying the surface material of a semiconductor substrate (base plate), such as silicon, in a pattern. The interaction of the materials changes and the pattern defines an electrical characteristic of the microelectronic device. Similar processes can be used to form micromechanical devices by, for example, electroplating metal structures onto a substrate in a desired pattern. Photolithography is used to define patterns on a substrate that will be doped, etched, or otherwise modified to form microelectronic or micromechanical devices.
In a basic photolithographic process for fabricating semiconductor structures, a photoresist is deposited on the surface of a substrate. The photoresist is sensitive to radiation, such as Extreme Ultraviolet (EUV) radiation, and depending on the photoresist used, the portions of the photoresist exposed to the radiation are removed (or retained) by a development process. The semiconductor structure is formed by etching or otherwise modifying the substrate in the areas where the photoresist has been removed. To form the desired pattern in the photoresist, the radiation used to expose the photoresist is passed through or reflected from a photolithographic mask that defines the pattern to be transferred to the photoresist.
Disclosure of Invention
Embodiments of the present invention generally relate to photoactive polymer brush materials and methods of patterning EUV photoresists using the same. Non-limiting examples of photoactive polymeric brush materials include a grafted moiety, a dry developable or ashable moiety, and a photoacid generating moiety (photoacid generating moiety). The grafting moiety comprises a grafting component selected from the group consisting of alkynes, alkenes, phosphonic acids, thiols, and silanes, and an acid cleavable component. The photoacid generating portion is configured to decompose and form an acid upon exposure to EUV radiation.
An exemplary method of forming a relief image in a positive chemically amplified EUV photoresist according to embodiments of the present invention includes grafting a monolayer of a photoactive polymeric brush material onto a substrate, wherein the photoactive polymeric brush material includes a grafted portion, a developable or ashable portion, and a photoacid generating portion. A positive chemically amplified EUV photoresist is applied to the photoactive polymer brush material monolayer. The positive chemically amplified EUV photoresist and the photoactive polymer brush material are exposed to EUV radiation to form a latent image within the chemically amplified EUV photoresist and to generate an acid at an interface between the photoresist and the substrate. A developer is applied to the substrate to form a relief image in the chemically amplified EUV photoresist and sever at least a portion of the photoactive polymer brush material from the substrate.
An exemplary method of generating an acid at an interface between a substrate and a positive chemically amplified EUV photoresist according to embodiments of the present invention includes grafting a single layer of a photoactive polymer brush material onto the substrate, wherein the photoactive polymer brush material includes an acid-cleavable graft moiety, a developable or ashable moiety, and a photoacid generator moiety. A positive chemically amplified EUV photoresist is applied to a single layer of photoactive polymer brush material. Exposing the positive chemically amplified EUV photoresist to EUV radiation, wherein the radiation decomposes a photoacid-generating moiety in the photoactive polymer brush material to form an acid at an interface between the substrate and the positive chemically amplified EUV photoresist in an amount effective to reduce scum of the positive chemically amplified EUV photoresist after development thereof as compared to exposure without the photoactive polymer brush material.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features, refer to the description.
Detailed Description
The present invention generally relates to photoactive polymer brush materials and methods of using the photoactive polymer brush materials to pattern positive chemically amplified EUV photoresists. One of the problems with chemically amplified photoresist patterning in EUV lithography is that scum is observed after development of the irradiated pattern in chemically amplified EUV photoresist, where the term "scum" is generally defined as the residual amount of photoresist remaining on the surface after development. While not wishing to be bound by theory, it is believed that scum present after patterning and development of a chemically amplified EUV photoresist may be attributed to acid loss (deletion) at the interface between the substrate and the photoresist, which subsequently prevents acid catalyzed reaction of the photoresist polymer at the interface. The lack of acid at the resist hardmask interface can be attributed to the random nature of EUV exposure. The number of reaching a specific dose in EUV photons is significantly less due to the high energy per photon compared to 193nm exposure. Thus, any small change may result in a significant lack of acid generation at the interface. As deposited chemically amplified EUV photoresist becomes thinner and thinner due to advanced design rules, resist scum at the interface in the developed (i.e., open) area becomes a significant (non-negligible) portion of the unexposed resist height as follows: a pattern transfer that masks the open areas is required.
Positive chemically amplified EUV photoresists typically comprise a polymeric resin that provides most of the properties of the photoresist film, a photoacid generator, and optionally a base. The fundamental difference in acid generation between DUV (deep UV) and EUV necessitates innovations in patterned material development. In DUV exposure, photons are absorbed by chromophores of photoacid generator (PAG) molecules in the resist matrix, which results in decomposition and acid generation. For similar dose sizes, the number of EUV photons is significantly reduced due to the high energy contained in each photon. Thus, EUV photons have sufficient energy to ionize (ionize) resist molecules, which emit secondary electrons that interact with the resist matrix to produce an acid. The resulting acid attacks the acid-labile protecting groups, causing an acid-catalyzed deprotection reaction within the polymer resin. As a direct result, the exposed regions have a higher dissolution rate than the unexposed regions, which are removable with a developer. The reverse is true for negative photoresist, where an acid-catalyzed crosslinking reaction is performed upon exposure to activation energy. Aspects of the present invention generally relate to a photoactive polymer brush and a method of patterning a positive chemically amplified EUV photoresist using the same. As described above, acid depletion at the substrate interface in the open areas can lead to scum, which can be eliminated by using a photoactive polymer brush material at the interface between the substrate surface and the positive chemically amplified EUV photoresist.
In embodiments of the invention, a relatively thin layer of photoactive polymeric brush material is grafted onto the substrate surface prior to deposition of the chemically amplified EUV photoresist to provide a photoresponsive monolayer having a thickness of typically less than about 10 nanometers (nm) at the interface between the substrate and the photoresist. In one or more embodiments of the invention, the thickness is less than 6 nm. In one or more embodiments of the invention, the thickness is less than 4 nm. As will be described in more detail below, in one or more embodiments of the invention, the photoactive polymer brush material incorporates grafted moieties that can be immobilized at the substrate surface, dry developable/ashable moieties, and photoacid generating moieties, all of which are bound to the polymer backbone. The photoacid generating moiety generates acid at the interface upon exposure to secondary electrons emitted as a result of ionization of the polymer matrix by EUV radiation, which overcomes the problem of acid loss to reduce photoresist scum. In addition, the photoacid generator moiety can facilitate cleavage of the photoactive polymer brush material from the substrate via an optional acid-cleavable grafted functional group. In the presence of residue after development of the chemically amplified EUV photoresist, the dry developable or ashable portion facilitates complete removal of the photoactive brush material from the substrate.
Examples of photoactive polymer brush materials according to the present invention and methods of EUV photoresist patterning using photoactive polymer brush materials will now be described herein. However, it is to be understood that the embodiments of the invention described herein are merely illustrative of structures that may be embodied in various forms. Furthermore, each of the examples given in connection with the various embodiments of the invention are intended to be illustrative, and not restrictive. Furthermore, if present, the figures are not necessarily to scale, and some features may be exaggerated to show details of particular components. Therefore, specific details of the structure and function described herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the methods and structures of the present specification. For purposes of the description hereinafter, the terms "upper," "lower," "top," "bottom," "left," and "right" as well as derivatives thereof shall relate to the described structure as it is oriented in the drawing figures. The same numbers in different drawings may refer to the same structural elements or parts thereof
As used herein, the articles "a" and "an" preceding an element or component are intended to be non-limiting with respect to the number of instances (i.e., occurrences) of the element or component. Thus, "a" or "an" should be understood to include one or at least one and the singular forms of an element or component also include the plural unless the number clearly indicates the singular.
As used herein, the term "invention" or "present invention" is a non-limiting term and is not intended to refer to any single aspect of a particular invention, but rather encompasses all possible aspects as set forth in the specification and claims.
Conventional techniques related to semiconductor device and Integrated Circuit (IC) fabrication may or may not be described in detail herein. Further, various tasks and process steps described herein may be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. In particular, various steps in the manufacture of semiconductor devices and semiconductor-based ICs are well known and, thus, in the interest of brevity, many conventional steps will only be mentioned briefly herein or will be omitted entirely without providing the well known process details.
Spatially relative terms, such as "below," "lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that 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. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features, and the term "below" would therefore encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Semiconductor devices and methods of forming the same according to embodiments of the invention may be used in applications, hardware and/or electronic systems. Hardware and systems suitable for implementing embodiments of the present invention may include, but are not limited to, personal computers, communication networks, electronic commerce systems, portable communication devices (e.g., cellular telephones and smart phones), solid state media storage devices, functional circuits, and the like. The systems and hardware incorporating the semiconductor device are embodiments contemplated by the present invention. Given the teachings of the embodiments of the present invention provided herein, one of ordinary skill in the related art will be able to contemplate other implementations and applications of the embodiments of the present invention.
Embodiments of the present invention may be used in conjunction with semiconductor devices requiring, for example, CMOS, MOSFET and/or FinFET devices. By way of non-limiting example, the semiconductor devices may include, but are not limited to, CMOS, MOSFET, and FinFET devices, and/or semiconductor devices using CMOS, MOSFET, and/or FinFET technology.
The following definitions and abbreviations are used to interpret the claims and the specification. As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.
The term "about" as used herein to modify the amount of an ingredient, component, or reactant of the invention refers to a change in that amount, which can occur, for example, through typical measurement and liquid handling procedures used to prepare concentrates or solutions. In addition, variations may occur due to inadvertent errors in the measurement process, differences in the manufacture, source, purity, etc. of the ingredients used to prepare the composition or practice the method. In one aspect, the term "about" means within 10% of the reported numerical value. In another aspect, the term "about" means within 5% of the reported numerical value. In another aspect, however, the term "about" means within 10, 9, 8, 7, 6, 5, 4,3, 2, or 1% of the reported numerical value.
It will also be understood that when an element such as a layer, region or substrate is referred to as being "on" or "over" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly over" another element, there are no intervening elements present, and the element is in contact with the other element.
As used herein, the term "substrate" refers to and includes such exposed materials or structures: a material such as a photoresist material may be deposited or otherwise formed thereon. The substrate may be a semiconductor substrate, a base semiconductor on a support structure, a metal electrode, or a semiconductor substrate having one or more layers, structures, or regions formed thereon. Although the materials described and illustrated herein may be formed as layers, the materials are not limited thereto and may be formed in other three-dimensional configurations. The substrate may be a silicon substrate or other bulk substrate (bulk substrate) comprising a semiconductor material. As used herein, the term "bulk substrate" means and includes a silicon wafer, i.e., a silicon-on-insulator ("SOI") substrate, such as a silicon-on-sapphire ("SOS") substrate or a silicon-on-glass ("SOG") substrate, a silicon epitaxial layer on a bulk semiconductor base or other semiconductor or optoelectronic material, such as silicon germanium (Si1-xGex, where x may be, for example, a mole fraction between 0.2 and 0.8), germanium (Ge), gallium arsenide (GaAs), gallium nitride (GaN), or indium phosphide (lnP). Furthermore, when reference is made to a "substrate" in the following description, previous process stages may have been performed to form regions or junctions in the substrate semiconductor structure or foundation.
As used herein, the term "developable" refers to a material formulated to be selectively dissolved or otherwise removed by an appropriate developer or development process after exposure to an EUV energy source. Thus, as used herein, a material referred to as "developable" may be selectively dissolved in an appropriate developer only after exposure to an appropriate energy source. For example, a positive photoresist is "developable" in that, after exposure to radiation of an appropriate wavelength or an appropriate chemical composition, exposed segments of the positive photoresist can be removed by an appropriate developer material, wherein the exposed segments of the positive photoresist are soluble. Likewise, the photoactive brush polymer material may be "developable" after exposure to standard etch chemistries or plasmas, ashing chemistries.
In aspects of the invention, one or more embodiments of the invention generally relate to photoactive polymer brush materials and methods of EUV photoresist patterning using the same. Photoactive polymeric brush materials typically include a polymeric backbone to which are attached a grafting moiety, a dry developable or ashable moiety, and a photoacid generating moiety. In one or more embodiments of the present invention, the photoactive polymer brush material may also include additional moieties having different functional groups as desired for different applications, e.g., functional groups that provide quenching, functional groups that provide desired solubility properties, functional groups that provide light absorption, and the like. Further, the grafted moieties may optionally be acid cleavable. The photoactive polymeric brush material can be formed by free radical polymerization or other known methods of grafting a functionalized monomer (optionally, an acid-cleavable grafted functional monomer), a dry-developable or ashable monomer, and a photoacid-generating functionalized monomer. Furthermore, the photoacid generating moiety may be a bound ionic or non-ionic photoacid generator depending on the desired acid generated, in particular, upon exposure of the chemically amplified EUV photoresist. The polymeric backbone of the photoactive polymeric brush material can be in the form of polyacrylate, polymethacrylate, polystyrene, mixtures thereof, and the like. The monomers forming the backbone of the polymeric brush can include, for example, but are not limited to, acrylate monomers, methacrylate monomers, styrene monomers, hydroxyethyl methacrylate monomers, epoxydicyclopentadiene methacrylate monomers, or other known conventional photoresist material monomers including the moieties described above attached thereto. For example, the different moieties may be attached to the carboxylic acid terminus of the polyacrylate.
In one or more embodiments of the present invention, the photoactive polymer brush material has an average molecular weight of from about 2 to about 500,000 daltons. In one or more embodiments of the present invention, the photoactive polymer brush material has an average molecular weight of from about 3 to about 300,000 daltons. In one or more embodiments of the present invention, the photoactive polymer brush material has an average molecular weight of from about 4 to about 100,000 daltons, as measured by gel permeation chromatography. The polymer has a polydispersity index (POI) of from about 1 to about 5.
A photoactive polymer brush material including acid-cleavable grafting functional groups may be grafted onto a substrate in a self-limiting grafting reaction to produce a photoresponsive monolayer at the interface between the substrate and the EUV photoresist that is typically less than about 8nm thick. By grafting the photoactive polymeric brush material directly onto the substrate, the photoacid generator functional groups become immobilized at the substrate surface, generating acid at the interface between the substrate and the photoresist upon exposure to EUV radiation to reduce and/or eliminate scum caused by the photoresist and sever the brush material from the substrate. In the case where the brush does not cut off, it can be removed during a dry etching process (or ashing, etc.) before the hard mask is opened. The activating radiation may be the same as the radiation used to form the latent image in the chemically amplified EUV photoresist. The acid loading and acid strength provided when the photoactive polymer brush material is exposed to activating radiation can be tailored to the performance. In a similar manner, the dry developable/ashable portion is fixed at the substrate surface, which provides a means for completely removing any residual photoactive polymer brush material and any photoresist scum from the substrate.
The grafting functionality may be selected from a number of different functionalities that will covalently attach to different substrate surfaces. The grafting functionality includes a grafting component and optionally an acid-cleavable component. For example, the graft component can include alkyne or alkene functional groups that can be used to attach the photoactive polymeric brush material to a substrate that includes a hydrogen-terminated surface (e.g., Si — H). Other functional groups for grafting the photoactive polymeric brush material onto a substrate include, for example, but are not limited to, hydroxyl and amine groups that will react with a substrate comprising an oxide surface, phosphonic acids that will react with a substrate comprising a metal oxide surface, and thiols that will react with a bare metal surface. The particular grafting component is not intended to be limiting and generally depends on the composition of the substrate surface. Non-covalent grafting moieties may also be included which result in physisorbed polymers such as pendant hydroxyl, carboxylic acid or amine groups.
The acid cleavable component may comprise a derivative which is a stable leaving group as follows: which renders the graft units acid cleavable such that photoactive polymer brush materials that may be up to about 10nm thick may be removed from the substrate surface upon exposure to acid generated by the photoacid generator moiety.
In one or more embodiments of the present invention, the photoactive polymer brush material may include two or more different acid-cleavable grafting functional groups.
To facilitate complete removal of the photoactive polymer brush material, most (i.e., greater than about 50%) of the photoactive polymer brush material includes dry developable or ashable portions. The dry developable or ashable portion is not intended to be limiting and may be methyl methacrylate, hexafluoroalcohol derivatives, and the like, which may be tailored to the particular process of record for the etching or ashing process to achieve complete removal from the substrate.
The incorporated photoacid generator monomer is not intended to be limiting and can be ionic or nonionic. The loading and the strength of the acid provided, for example a strong acid similar in strength to the triflate functional group to a weaker acid such as fluorinated aromatic compounds and even non-fluorinated derivatives, can vary. The photoacid generator monomer typically includes a photoacid generating moiety linked to a polymerizable moiety and is capable of generating an acid upon exposure to EUV radiation.
In various embodiments of the present invention, any suitable photoacid generator can be used as the photoacid generating moiety, including ionic and non-ionic photoacid generators, so long as the selected photoacid generator can be linked to the polymerizable moiety, sufficiently dissolved in the coating composition, and the resulting solution thereof can form a coating on a substrate by a dispensing method, spin coating, or the like. As is well known to those of skill in the art upon reading this detailed description, the following exemplary classes of photoacid generators can be used in various embodiments of the present invention.
Typical photoacid generators include, but are not limited to: (1) sulfonium salts such as triphenylsulfonium perfluoromethanesulfonate (triphenylsulfonium trifluoromethanesulfonate), triphenylsulfonium perfluorobutanesulfonate, triphenylsulfonium perfluoropentanesulfonate, triphenylsulfonium perfluorooctanesulfonate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroarsenate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium bromide, triphenylsulfonium chloride, triphenylsulfonium iodide, 2,4, 6-trimethylphenyldiphenylsulfonium perfluorobutanesulfonate, 2,4, 6-trimethylphenyldiphenylsulfonium benzenesulfonic acid, tris (t-butylphenyl) sulfonium perfluorooctanesulfonate, diphenylethylsulfonium chloride, and phenacyldimethylsulfonium chloride; (2) halogen salts, particularly iodine salts, including diphenyliodonium perfluoromethanesulfonate (diphenyliodonium trifluoromethanesulfonate), diphenyliodonium perfluorobutanesulfonate, diphenyliodonium perfluoropentasulfonate, diphenyliodonium perfluorooctanesulfonate, diphenyliodonium hexafluoroantimonate, diphenyliodonium hexafluoroarsenate, bis- (tert-butylphenyl) -iodonium trifluoromethanesulfonate and bis- (tert-butylphenyl) -iodonium camphosulfonate; (3) α, α' -bis-sulfonyl-diazomethanes such as bis (p-toluenesulfonyl) diazomethane, methylsulfonyl-p-toluenesulfonyl diazomethane, I-cyclohexylsulfonyl-I- (1, 1-dimethylethylsulfonyl) diazomethane and bis (cyclohexylsulfonyl) diazomethane; (4) sulfonic acid esters of imides and hydroxyimides, such as α (trifluoromethylsulfonyloxy) -bicyclo [2.2.1] hept-5-ene-2, 3-dicarboximide (MDT); (5) nitrobenzyl sulfonate esters, such as 2-nitrobenzyl p-toluenesulfonate, 2, 6-dinitrobenzyl p-toluenesulfonate and 2, 4-dinitrobenzyl p-trifluoromethylbenzenesulfonate; (6) sulfonyloxynaphthalimides, such as N-camphorsulfonyloxynaphthalimide and N-pentafluorophenylsulfonyloxynaphthalimide; (7) pyrogallol derivatives (e.g., trimesate of pyrogallol); (8) naphthoquinone-4-diazide; (9) an alkyl disulfone; (10) an s-triazine derivative; and (11) various sulfonic acid generators including t-butyl alpha- (p-toluenesulfonyloxy) acetate, N-hydroxynaphthalimide dodecanesulfonate (DDSN), and benzoin tosylate.
Other suitable photoacid generators that can be used in conjunction with the coating compositions and methods provided herein are known to those skilled in the art. Exemplary photoacid generator monomers suitable for use in the present application are described in U.S. patent 9,244,345, which is incorporated herein by reference in its entirety.
By way of example, the photoactive polymer brush material may be an acrylate terpolymer generally represented by the following formula (I):
(I)
wherein A is a graft moiety; b is a dry developable or ashable portion; and C is a bound photoacid generator; wherein X may be selected from-H, -CH3、-CH2CH3(ii) a And wherein l may be 5-20%; m may be 90-60% and n may be 5-20%.
Exemplary graft moieties are shown below:
exemplary dry developable or ashable portions are shown below:
exemplary ionic and nonionic photoacid generating moieties are shown below:
the photoactive polymer brush material may be dissolved in a solvent and applied to a substrate. The choice of solvent is determined by many factors, not limited to the solubility and miscibility of the resist components, the coating process, safety, and environmental regulations. In addition, inertness to other resist components is desirable. It is also desirable that the solvent be of suitable volatility to allow for uniform coating of the film, yet allow for significant reduction or complete removal of residual solvent during the post-application baking process. The solvent may typically be selected from ether, ester, hydroxy and ketone containing compounds, or mixtures of these compounds. Examples of suitable solvents include cyclopentanone, cyclohexanone, lactic acid esters such as ethyl lactate, alkylene glycol alkyl ether esters such as Propylene Glycol Methyl Ether Acetate (PGMEA), alkylene glycol monoalkyl esters such as methyl cellosolve, butyl acetate, 2-ethoxyethanol, and ethyl 3-ethoxypropionate. The above list of solvents is for illustrative purposes only and should not be construed as comprehensive nor limiting the invention in any way. One skilled in the art will recognize that any number of solvents or solvent mixtures may be used. In one or more embodiments, greater than 50% of the total mass of the photoactive polymer brush formulation is made up of solvent, and in one or more other embodiments, greater than 80% of the formulation is solvent.
Methods of patterning positive-working chemically amplified EUV photoresists using photoactive polymer brushes generally include grafting a photoactive polymer brush material onto a substrate to form a photosensitive layer. The photoactive polymer brush material may be dissolved in a solvent and applied by, for example, spin coating, followed by post-application baking at elevated temperatures to remove the solvent until the coating is tack-free. The post-application bake is at an elevated temperature in the range of 80 ℃ to less than 200 ℃ for a time period in the range of 1 second to less than 600 seconds. The applied coating of photoactive polymeric brush material may then be rinsed to remove excess photoactive polymeric brush material, i.e., photoactive polymeric brush material that has not been grafted to the substrate. The thickness of the photoactive polymer brush material is less than about 8 nm.
After deposition of the photoactive polymer brush material, a chemically amplified EUV photoresist is deposited thereon at a thickness typically in the range of 30nm to 50nm and lithographically patterned with EUV radiation at an exposure wavelength of 13.5nm to form a relief image thereon. In the exposed areas, acid is generated in the EUV and acid-labile groups within the chemically amplified photoresist undergo acid-catalyzed deprotection. In addition, the underlying (undercutting) incorporated photoacid generators in the photoactive polymer brush polymer material are also photoactivated upon exposure to the same EUV radiation to generate an acid at the interface between the substrate and the photoresist. The acid generated within the grafted monolayer reduces photoresist scum and may also sever the grafted portions from the substrate, thereby allowing the photoresist and photoactive polymeric brush material to be removed to form a relief image after the latent image in the chemically amplified EUV photoresist is developed by a suitable developer. Any residual photoactive polymer brush material and/or photoresist scum that is still present can then be removed by dry development or by ashing. For example, exposed photoactive polymer brush materials can be etched with standard etch chemistries such as Cl2、SF6、HBr/O2And the like, or subjected to a plasma ashing process.
The description of the various embodiments of the present invention has been presented for purposes of illustration, but is not intended to be exhaustive or limited to the embodiments of the invention described. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the described embodiments of the invention. The terminology used herein is chosen in order to best explain the principles of the embodiments of the invention, the practical application or technical improvements over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments of the invention described herein.