WO2020172481A1

WO2020172481A1 - Photoresists for making euv patternable hard masks

Info

Publication number: WO2020172481A1
Application number: PCT/US2020/019134
Authority: WO
Inventors: Gregory BLACHUT; Christopher Bates
Original assignee: Lam Research Corp
Current assignee: Lam Research Corp
Priority date: 2019-02-22
Filing date: 2020-02-21
Publication date: 2020-08-27
Anticipated expiration: 2021-08-22
Also published as: TW202043922A

Abstract

Compositions and methods for making photoresists on semiconductor substrates, which may be patterned using EUV. The photoresists comprise a graft polymer comprising a backbone polymer, a side-chain polymer, and an acid-cleavable (acid-labile) linking moiety between the backbone polymer and side-chain polymer. In various photoresists, the Tg of the polymeric side chains after they are cleaved from the graft polymer is lower than the Tg of the graft polymer with the side chains still attached. For example, the Tg of the graft polymer may be from about 80 - 200° C, preferably from about 95 - 140° C.

Description

PHOTORESISTS FOR MAKING EUV PATTERNABLE HARD MASKS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/809,160 filed on February 22, 2019. The entire disclosure of the application referenced above is incorporated herein by reference.

FIELD

[0002] The present technology relates to materials and methods for making lithographic masks for use in semiconductor fabrication. In particular, the present technology provides chemically amplified photoresists used for producing patternable hard masks on semiconductor substrates.

BACKGROUND

[0003] The background description provided herein is for the purpose of generally presenting the context of the present technology. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present technology.

[0004] The fabrication of semiconductor devices, such as integrated circuits, is a multi-step process involving photolithography. In general, the process includes the deposition of material on a wafer, and patterning the material through lithographic techniques to form structural features (e.g., transistors and circuitry) of the semiconductor device. The steps of a typical photolithography process known in the art include: preparing the substrate; applying a photoresist, such as by spin coating; exposing the photoresist to light in a desired pattern, causing the exposed areas of the photoresist to become more or less soluble in a developer solution; developing by applying a developer solution to remove either the exposed or the unexposed areas of the photoresist; and subsequent processing to create features on the areas of the substrate from which the photoresist has been removed, such as by etching or material deposition.

[0005] The evolution of semiconductor design has created the need, and has been driven by the ability, to create ever smaller features on semiconductor substrate materials. This progression of technology has been characterized in“Moore’s Law” as a doubling of the density of transistors in dense integrated circuits every two years. Indeed, chip design and manufacturing has progressed such that modern microprocessors may contain billions of transistors and other circuit features on a single chip. Individual features on such chips may be on the order of 22 nanometers (nm) or smaller, in some cases less than 10 nm.

[0006] One challenge in manufacturing devices having such small features is the ability to reliably and reproducibly create photolithographic masks having sufficient resolution. Current photolithography processes typically use 193 nm ultraviolet (UV) light to expose a photoresist. The fact that the light has a wavelength significantly greater than the desired size of the features to be produced on the semiconductor substrate creates inherent issues. Achieving feature sizes smaller than the wavelength of the light requires use of complex resolution enhancement techniques, such as multipatterning. Thus, there is significant interest and research effort in developing photolithographic techniques using shorter wavelength light, such as extreme ultraviolet radiation (EUV), having a wavelength of from 10 nm to 15 nm, e.g., 13.5 nm.

[0007] Chemically-amplified resists (CARs) have been developed in an effort to improve photolithographic resolution and achieve smaller features. A conventional CAR is composed of linear polymers, and the repeat units of these polymers contain alcohol or carboxylic acid functional groups protected by comparatively hydrophobic moieties. During exposure in a photolithographic process, acid is generated (in the case of EUV, primarily by a secondary electron), which leads to a cascading reaction by which the physical properties of the CAR are modified, making them either more or less susceptible to being removed in subsequent lithographic processing.

[0008] However, traditional CARs, similar to those used in 193 nm UV lithography, have potential drawbacks. For example, during post-exposure baking (PEB) of a CAR, the acid produced in the exposed regions of the CAR may diffuse beyond the regions of film exposed by radiation, causing unwanted bias or blur. Blur contributes to unwanted line-edge roughness, and may be a root cause of unwanted stochastic failures that may be observed in exposures of EUV resists. It can be difficult to improve acid blur in an optimized resist system without adversely affecting either the ultimate resolution or the sensitivity of the resist. This engineering trade-off is often referred to as the“resolution, line width roughness, and sensitivity (RLS) trade-off”. This issue is further exacerbated in EUV lithography, as few photons reach the wafer and even fewer are absorbed by the CAR, requiring more blur to compensate for lower effective dose.

[0009] Accordingly, there remains a need for improved photoresist materials, particularly for use in EUV and similar lithographic techniques. For example, materials and methods that maintain acid diffusion in exposed resist areas while minimizing diffusion in unexposed areas would be advantageous for EUV lithography.

SUMMARY

[0010] The present technology provides compositions and methods for making photoresists on semiconductor substrates, which may be patterned using EUV. The photoresists comprise a graft polymer comprising a backbone polymer, a side-chain polymer, and an acid-cleavable (acid-labile) linking moiety between the backbone polymer and side-chain polymer. In some embodiments the backbone may be a homopolymer, comprising substantially identical monomer or macromonomer units. Alternatively, the backbone may be a copolymer, comprising two or more monomers or macromonomers.

[0011] In various photoresists, the T_g of the polymeric side chains after they are cleaved from the graft polymer is lower than the T_g of the graft polymer with the side chains still attached. For example, the T_g of the graft polymer may be from about 80 - 200° C, preferably from about 95 - 140° C.

[0012] The present technology also provides methods of making photoresists of the present technology including “grafting-to,” “grafting-from,” and “grafting-through” synthetic approaches. The present technology also provides methods for making a resist layer on a surface of a semiconductor substrate, the method comprising:

(a) applying a chemically-amplified photoresist, comprising a graft polymer having a backbone polymer with a plurality of acid-cleavable side chains, to the surface to form a photoresist layer;

(b) selectively irradiating the photoresist layer, such that the photoresist layer comprises an irradiated region and an unirradiated region; and

(c) baking the photoresist layer.

[0013] Further areas of applicability of the present technology will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present technology will become more fully understood from the detailed description and the accompanying drawings, wherein:

Figure 1 depicts a first exemplary synthetic scheme for making a macromonomer useful in a resist material of the present technology.

Figure 2 depicts a second exemplary synthetic scheme for making a macromonomer useful in a resist material of the present technology.

DETAILED DESCRIPTION

[0015] The following description of technology is merely exemplary in nature of the subject matter, manufacture and use of one or more inventions, and is not intended to limit the scope, application, or uses of any specific invention claimed in this application or in such other applications as may be filed claiming priority to this application, or patents issuing therefrom. A non-limiting discussion of terms and phrases intended to aid understanding of the present technology is provided at the end of this Detailed Description.

[0016] As discussed above, the present technology provides compositions and methods for making photoresists on semiconductor substrates, which may be patterned using EUV or other light or energy sources. Note, while methods of the present technology are described in various embodiments for use in producing substrates that may be patterned by EUV, reference to EUV is for convenience and does not limit the lithographic methods that may be used to pattern such substrates. In particular, substrates made by the methods of the present technology may be patterned using other energy sources, such as deep ultraviolet lithography (DUV), and electron beam lithography (EBL), as further described herein.

[0017] In general, the present technology provides photoresists, specifically chemically-amplified resists (CARs), comprising a graft polymer having a backbone polymer with a plurality of acid-cleavable polymeric side chains. The side-chain polymers are connected to the backbone with acid-cleavable bonds, such that during post-exposure bake (PEB) of the resist (as described further, below), acid cleaves the side-chains from the backbone, in addition to catalyzing the typical deprotection reactions in the resist.

[0018] In various embodiments, the mobility of the polymer resist is increased after separating the side-chain polymers from the backbone polymer, since small polymers can have comparably lower glass transition temperatures (Tg) (a measure of polymer mobility) than large polymers. In general, films with higher mobility also have overall higher rates of diffusion, which in this case specifically promotes the diffusion of acid in those areas. In this way, anisotropic acid diffusion is realized. Accordingly, the graft polymer can have a T_g comparable to that of a polymer of infinite molecular weight - essentially as high as that specific material allows - but the comparably short side- chains that constitute the polymer can have a significantly lower Tg. During the PEB, acid cleaves the side-chain polymers from the backbone, decreasing the overall molecular weight of the matrix in that region, and consequently depresses Tg.

[0019] Without limiting the mechanism, function or utility of present technology, it is believed that, in some embodiments, the architecture of the photoresist polymers of the present technology decreases the undesired blur associated with acid diffusion during the exposure and post-exposure bake (PEB) of the resist. In some embodiments, the side-chain-cleavable graft-polymer may be synthesized and formulated to create blur essentially equivalent to the blur created by a conventional CAR, but may have improved sensitivity because of the RLS trade-off between blur and sensitivity.

[0020] In various embodiments, the photoresists of the present technology have the following general formula.

I

(A)n - L - B

I

Formula 1 wherein A is a backbone polymer, B is a side-chain polymer, and L is an acid-cleavable (acid-labile) linking moiety. In some aspects, the CARs of the present technology may comprise a mixture of two or more resists of Formula 1. [0021] In some embodiments, the photoresist is of the following general formula.

Formula 2

The left set of parentheses in Formula 2 indicates the graft polymer backbone polymer A (as in Formula 1 ), such as a polyacrylate. R-i, R2, and the depicted ketal or acetal, forms linking moeity L.

[0022] In Formula 2, Ri is linked to the graft backbone polymer, and may be (for example) an alkyl chain (e.g., having from 1 to 4 carbon atoms), and may additionally comprise heteroatoms, such as oxygen. R2 is linked to the side-chain polymer, and may be (for example) an alkyl chain (e.g., having from 1 to 4 carbon atoms) and may additionally comprise heteroatoms, such as oxygen. The right set of parentheses indicate the side-chain polymer, here depicted also as a polyacrylate. R3 indicates the end-group of the side-chain polymer B (as in Formula 1 ), and may be (for example) hydrogen, chlorine, bromine, iodine, thiol, thioether, trithiocarbonate, dithioester, or xanthate. R3 may be formed as a consequence of the polymerization technique used to make the side-chain polymer, and may also have been modified after polymerization to a less-reactive form to minimize reactivity in the final resist. The structures of R2 and R3 are highly dependent on the polymerization technique employed to make the side-chain polymer. R4 is a protecting group on the side-chain polymer, which may function as the solubility-switching moiety in the CAR. For example, possible chemical groups for R4 may be tert-butyl or adamantyl. Suitable R4 protecting groups include any chemical group more hydrophobic than a carboxylic acid group, that leaves upon heating to produce the carboxylic acid group, and where this leaving event is catalyzed by the presence of acid. Other suitable protecting groups are described in Sanders, D. P. “Advances in Patterning Materials for 193 nm Immersion Lithography.” Chemical Reviews, 110 (1 ), 321-360 (2010). Rs may be hydrogen, alkyl, or aryl. [0023] As depicted in Formula 2, the side-chain polymer (B, as in Formula 1 ) is a homopolymer. Flowever, in some embodiments, the side-chain polymer is a copolymer. For example, the side chain polymer may be a copolymer of the following formula.

The side-chain polymer of Formula 3 is a statistical copolymer comprising acrylic, methacrylic, ethacrylic, styrenic components, or combinations thereof. Although Formula 3 depicts just two generic acrylic repeat units and two generic styrenic repeat units, the polymer may be comprised of any number of types of repeat units. Moreover, the polymer may not include any of a given specific type of repeat unit. In addition, the chain depicted within the brackets (with the subscript N) conveys that, although the components are written in a sequential sequence, in reality they would be statistically distributed throughout the chain. Si, S2, S3, and S4 (and extended possibly up to SN) are, individually, hydrogen or lower alkanes (such as methyl or ethyl) or higher alkanes. T 1 , T2, T3, and T4 (again, extended possibly up to TN) are organic protecting groups that may or may not become deprotected during photoresist exposure, post-exposure baking or development. In various embodiments, T 1 , T2, T3, and T4 are, individually, alkyl groups, aryl groups, either alkyl or aryl groups that contain heteroatoms (e.g., oxygen, nitrogen, or sulfur), acid-cleavable protecting groups, or hydrogen. For example, any T may be fe/f-butyl, adamantly, or fe/f-butoxycarbonyl (commonly abbreviated t-BOC or just BOC). Other suitable protecting groups are described in Sanders, D. P.“Advances in Patterning Materials for 193 nm Immersion Lithography.” Chemical Reviews. 110 (1 ), 321-360 (2010). [0024] In various embodiments, side chain polymers may be a copolymer of the following formula, which is a more specific embodiment of Formula 3.

The generic acrylate and styrene, depicted with SN substituents on the backbone and TN functional groups in Formula 4, may refer to more than one non-specified monomer of either variety or both varieties. For example, Si and S2 are, individually, hydrogen, methyl, ethyl, or higher alkanes, and Ti and T2 are, individually, alkyl groups, aryl groups, either alkyl or aryl groups that contain heteroatoms (e.g., oxygen, nitrogen, or sulfur), acid-cleavable protecting groups, or hydrogen.

[0025] Further examples of specific side chain polymers are shown in the following formulas.

Formula 5

In various embodiments, a depicted monomer in the polymers of Formulas 5, 6 and 7 may be omitted, or substituted with other monomers as described above.

[0026] In various photoresists, the T_g of the polymeric side chains after they are cleaved from the graft polymer is lower than the T_g of the graft polymer with the side chains still attached. For example, the T_g of the graft polymer may be from about 80 - 200° C, preferably from about 95 - 140° C. In some embodiments, the plurality of polymeric side chains comprises a polymeric side chain having a T_g which is at least 10° C, preferably at least 20° C, less than the T_g of the backbone polymer.

[0027] In various embodiments, the backbone polymer comprises acrylic or methacrylic monomers, primarily due to the ease of functionalizing the ester group to build the side-chain linker.

[0028] In some embodiments the backbone may be a homopolymer, comprising substantially identical monomer or macromonomer units. Alternatively, the backbone may be a copolymer, comprising two or more monomers or macromonomers. In some embodiments, such polymers comprise a plurality of first macromonomers and a plurality of second macromonomers. For example, the graft polymer may comprise a small portion of polymers without an acid-cleavable group, so as to modulate the solubility of the backbone polymer during wet development. The ratio of the number of macromonomers having an acid-cleavable moiety to the number of the second macromonomers in the copolymer may be from about 99:1 to about 1 :99.

[0029] In some embodiments, the graft polymer may comprise polymers having low surface-energy substituents, such as fluorinated alkyl or methylsilyl groups, so as to change the surface energy, and thus thin film behavior, of the graft polymer. The graft polymers may also comprise small molecule monomers to further modulate the properties of the polymer.

[0030] The acid-cleavable moiety may be, for example, a ketal or an acetal. In various embodiments, the acid-cleavable moiety is an acetal.

Methods of Making Photoresist Compositions

[0031] The photoresists of the present technology may be made by any of a variety of methods useful to make graft polymers among those known in the art. Such methods include, for example, “grafting-to,” “grafting-from,” and “grafting-through” synthetic approaches. Such synthetic methods are based on such approaches generally understood in the art for the synthesis of graft polymers.

[0032] In various embodiments, a“grafting-through” approach to synthesize the graft polymer is preferred, where first a so-called macromonomer is formed which consists of the linear polymer of the hydrophobically-protected CAR moieties, connected through the acid-labile linker group to a polymerizable end-group. The graft copolymer is then created by“grafting-through” (polymerizing) these polymerizable end- groups. Multiple plausible sequences exist to form the macromonomer containing these three components together. One preferred method is to first synthesize the linear polymer, utilizing any number of controlled polymerization techniques that yield a polymer with at least one or more reactive end-groups. The acid-labile group is then installed onto the linear polymer, utilizing the reactive end-group as a synthetic handle, and then the secondary polymerizable end-group is installed onto the other end of the acid-labile group. A different, but related, method first joins together the acid-labile group and the secondary polymerizable end-group, before linking this larger molecule to the linear polymer containing the reactive end-group. Regardless of route, the macromonomers containing the linear polymer, the acid-labile group, and the secondary polymerizable end-group are then subjected to a second polymerization which joins the linear polymers at the site of the secondary polymerizable end-group to yield the final construct, the graft polymer.

[0033] Another method to create a macromonomer for graft polymerization comprises first functionalizing the acid-cleavable linker with the functional groups required to perform a polymerization, and then using this molecule to conduct a polymerization to produce the linear polymer comprising the hydrophobically-protected CAR moieties. Then, the secondary polymerizable group is installed onto the other end of the acid-cleavable linker, and this macromonomer is further polymerized to form the graft polymer. A slight modification of this route comprises first combining the polymerizable end-group, acid-linker, and different polymerizable functional group, performing the first polymerization to yield the linear polymer (without reacting the polymerizable end-group), and then conducting a separate polymerization to create the graft polymer with the polymerizable end-group.

[0034] Thus, in some embodiments, the present technology provides methods for making photoresist graft copolymers, comprising:

making a plurality of macromonomers, each of which comprises a polymeric moiety, a polymerizable end-group, and an acid-cleavable linker between the polymeric moiety and the polymerizable end-group; and

polymerizing the polymerizable end-groups of the macromonomers to form the graft polymer.

[0035] In various embodiments, a controlled radical polymerization is preferred to make the linear polymer since materials made by these methods may be very free of metals, a requirement for semiconductor manufacturing. In this method, a linear polymer is formed from monomers consisting of alcohol or acid functional groups protected by a hydrophobic group, as well as other functional groups to modulate the polymer’s solubility or etch resistance, such as may be used in CARs among those known in the art. However, unlike a conventional CAR, one end of the initial linear polymer contains a functional group that is amenable to further polymerization, and this functional group is linked to the rest of the polymer through an acid-cleavable moiety (for example, a ketal). [0036] Although controlled radical polymerization may be a preferred method to make the linear polymer, it is also possible to make a suitable polymer with a controlled anionic or cationic polymerization. These methods, however, may be more prone to metal contamination and may be less amenable to different varieties of monomers used to construct CARs.

[0037] In other embodiments, methods for making photoresist graft polymers comprise making a backbone polymer comprising reactive functional groups joined to the backbone by an acid-cleavable linker, and using the reactive functional groups to initiate the polymerization of a plurality of sidechains to form the graft copolymer (“grafting-from” approach). In yet other embodiments, such methods comprise making a backbone polymer comprising reactive functional groups joined to the backbone by an acid-cleavable linker, further making a plurality of sidechain polymers with complementary functional groups, and chemically bonding the sidechain polymers to the backbone polymer through the complementary reactive functional groups to form the graft polymer (“grafting-to” approach).

[0038] After the initial linear polymer is made, the material may be isolated, purified, and/or dried to a powder, before proceeding with additional reaction steps. However, in some embodiments, it may be advantageous to skip one or more of these purification and isolation steps, and proceed directly to subsequent reactions.

[0039] The second polymerization then takes place to combine the linear polymers into the graft polymer. The specifics of this polymerization depends on the choice of polymerizable end-group introduced into the linear polymer. If a post polymerization modification strategy is employed to install a conventional olefin onto the linear polymer, then a controlled radical polymerization can be employed. Another possible route is the use of a strained ring olefin and Ring Opening Metathesis Polymerization.

[0040] As noted above, the graft polymer may be composed of different combinations of linear polymer precursors, not just a single linear polymer type, to target different resist properties. Such polymers may be made by copolymerization methods in a statistical fashion or in a blocky fashion. Photolithographic Methods

[0041] The present technology provides methods for making masks on the surface of substrates using chemically-amplified resists. Substrates useful in this technology include any material construct suitable for photolithographic processing, particularly for the production of integrated circuits and other semiconducting devices. In some embodiments, substrates are silicon wafers. (As referred to herein, the “surface” is a surface onto which a resist of the present technology is to be deposited or that is to be exposed to EUV during processing.)

[0042] Accordingly, the present technology provides methods for making a resist layer on a surface of a semiconductor substrate, the method comprising:

(c) baking the photoresist layer.

[0043] As noted above, irradiating comprises the use of DUV, EUV or e-beam radiation. In such patterning, the irradiation is focused on one or more regions of the CAR. Exposure to EUV (for example) is typically performed such that the CAR comprises one or more regions that are not exposed to EUV light. The resulting film may comprise a plurality of exposed and unexposed regions, creating a pattern consistent with the creation of transistor or other features of a semiconductor device, formed by addition or removal of material from the substrate in subsequent processing of the film and substrate. EUV, DUV, and e-beam radiation devices and imaging methods include methods known in the art.

[0044] In some embodiments, methods comprise developing the photoresist layer after the baking, so as to remove the photoresist layer in the irradiated region or the unirradiated region. Developing may comprise applying a solvent, such as alkaline water, to the photoresist layer to remove the irradiated region.

[0045] In various embodiments, the photolithographic methods using the photoresists of the present technology are generally similar in to methods known in the art utilizing conventional CARs. For example, a resist formulation may be deposited via spin coating onto a substrate and soft-baked. The resist relies on a solubility-switching mechanism and wet development to generate the relief pattern for subsequent process steps in semiconductor manufacturing. However, without limiting the mechanism, function or utility of present technology, it is believed that the resists and methods of the present technology address the diffusion issues of conventional processes by biasing acid diffusion into areas of the resist which have already been exposed to acid while minimizing the diffusion of acid into the unexposed, acid-free regions. This occurs by increasing the mobility of the polymer matrix only in the acid-containing regions. The selective increase of mobility may be accomplished by cleaving the side-chains off of the backbone polymer to reduce the overall length of the polymer chains in the areas containing acid (the correlation between short polymer chains and increased polymer mobility is well established). Due to the increased mobility of the matrix, diffusion is promoted in these regions compared to the regions with less mobility.

[0046] During exposure, acid is generated (in the case of EUV, primarily by a secondary electron, for DUV, primarily by a photon, and either by a primary or secondary electron in EBL), and during the PEB, this acid catalytically deprotects the hydrophobic groups, exposing the comparatively hydrophilic alcohol or acid functional groups and drastically transforming the solubility properties of the polymer in the exposed region. Then, during the development step, a solvent such as alkaline water is used to remove the exposed, hydrophilic regions, leaving behind the unexposed, hydrophobic regions as an etch mask for further processing. (Note it is equally possible to perform the wet development“in reverse”, where the solvent is chosen instead to remove the unexposed, hydrophobic regions and leave behind the exposed, hydrophilic regions.)

[0047] Embodiments of the present technology are further illustrated through the following non-limiting examples.

Example 1

[0048] A macromonomer useful in making a graft polymer CAR of the present technology may be made by metal-free ATRP (atom transfer radical polymerization). Such a method is depicted in Figure 1.

[0049] Specifically, an alcohol ketone such as 4-hydroxy-2-butanone is reacted with alpha-bromoisobutyryl bromide and a base such as triethyl amine to yield the brominated ester ketone and hydrogen bromide as a by-product. The product is then contacted with a tri-alcohol like glycerol or (+)-1 ,2,4-butanetriol to form the ketal with catalytic amounts of acid and removal of water. At this step, the molecule has an alcohol end-group as well as a bromine end-group. Metal-free ATRP can then be performed utilizing the bromine as described in Treat, N. J.; et al.; Journal of the American Chemical Society 136 (45), 16096-16101 (2014). The resultant ATRP polymer is then transformed into a macromonomer by the condensation reaction with acryloyl chloride or a similar compound and a base such as triethylamine. The olefin- containing product can then be polymerized via a conventional or controlled radical polymerization technique to yield the graft polymer.

Example 2

[0050] A macromonomer useful in making a graft polymer CAR of the present technology may be made by a RAFT method (reversible addition-fragmentation chain- transfer). Such a method is depicted in Figure 2.

[0051] Specifically, a commercial RAFT initiating agent containing a carboxylic acid group like 4-Cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid is used to conduct a RAFT polymerization. Separately, acryloyl chloride or a similar compound is contacted with solketal and a base like triethylamine to yield an acrylate. The acrylate is then exposed to acid to regain the di-alcohol. The product is then contacted with an alcohol ketone such as 4-hydroxy-2-butanone to yield an alcohol-containing, acetal- containing, acrylate. This acrylate, and the carboxylic-acid-containing RAFT polymer, are coupled together with EDC and DMAP to yield the macromonomer, which can then undergo polymerization to yield the graft polymer.

Non-limiting Discussion of Terminology

[0052] The foregoing description is merely illustrative in nature and is in no way intended to limit the technology, its application, or uses. The broad teachings of the technology can be implemented in a variety of forms. Therefore, while this technology includes particular examples, the true scope of the technology should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims.

[0053] The headings (such as“Background” and“Summary”) and sub-headings used herein are intended only for general organization of topics within the present technology, and are not intended to limit the technology of the technology or any aspect thereof. In particular, subject matter disclosed in the“Background” may include novel technology and may not constitute a recitation of prior art. Subject matter disclosed in the“Summary” is not an exhaustive or complete technology of the entire scope of the technology or any embodiments thereof. Classification or discussion of a component or material within a section of this specification as having a particular utility is made for convenience, and no inference should be drawn that the component or material must necessarily or solely function in accordance with its classification herein when it is used in any given composition.

[0054] It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present technology. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the technology can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this technology. For example, a component which may be A, B, C, D or E, or combinations thereof, may also be defined, in some embodiments, to be A, B, C, or combinations thereof.

[0055] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean“at least one of A, at least one of B, and at least one of C.”

[0056] As used herein, the words“prefer” or“preferable” refer to embodiments of the technology that afford certain benefits, under certain circumstances. Flowever, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the technology.

[0057] As used herein, the word“include,” and its variants, is intended to be non limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, devices, and methods of this technology. Similarly, the terms“can” and“may” and their variants are intended to be non-limiting, such that recitation that an embodiment can or may comprise certain elements or features does not exclude other embodiments of the present technology that do not contain those elements or features.

[0058] Although the open-ended term “comprising,” as a synonym of non- restrictive terms such as including, containing, or having, is used herein to describe and claim embodiments of the present technology, embodiments may alternatively be described using more limiting terms such as“consisting of” or“consisting essentially of.” Thus, for any given embodiment reciting materials, components or process steps, the present technology also specifically includes embodiments consisting of, or consisting essentially of, such materials, components or processes excluding additional materials, components or processes (for consisting of) and excluding additional materials, components or processes affecting the significant properties of the embodiment (for consisting essentially of), even though such additional materials, components or processes are not explicitly recited in this application. For example, recitation of a composition or process reciting elements A, B and C specifically envisions embodiments consisting of, and consisting essentially of, A, B and C, excluding an element D that may be recited in the art, even though element D is not explicitly described as being excluded herein. Further, as used herein the term “consisting essentially of” recited materials or components envisions embodiments “consisting of” the recited materials or components.

[0059] “A” and“an” as used herein indicate“at least one” of the item is present; a plurality of such items may be present, when possible.

[0060] Numeric values stated herein should be understood to be approximate, and interpreted to be about the stated value, whether or not the value is modified using the word“about.” Thus, for example, a statement that a parameter may have value“of X” should be interpreted to mean that the parameter may have a value of “about X.” 'About" when applied to values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by“about” is not otherwise understood in the art with this ordinary meaning, then“about” as used herein indicates variations that may arise from ordinary methods of manufacturing, measuring or using the material, device or other object to which the calculation or measurement applies. [0061] As referred to herein, ranges are, unless specified otherwise, inclusive of endpoints and include technology of all distinct values and further divided ranges within the entire range. Thus, for example, a range of“from A to B” or“from about A to about B” is inclusive of A and of B. Further, the phrase“from about A to about B” includes variations in the values of A and B, which may be slightly less than A and slightly greater than B; the phrase may be read be“about A, from A to B, and about B.” Technology of values and ranges of values for specific parameters (such as temperatures, molecular weights, weight percentages, etc.) are not exclusive of other values and ranges of values useful herein.

[0062] It is also envisioned that two or more specific exemplified values for a given parameter may define endpoints for a range of values that may be claimed for the parameter. For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that Parameter X may have a range of values from about A to about Z. Similarly, it is envisioned that technology of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if Parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, and 3-9.

Claims

CLAIMS What is claimed is:

1. A chemically-amplified photoresist, comprising a graft polymer having a backbone polymer with a plurality of acid-cleavable polymeric side chains.

2. The chemically-amplified photoresist of Claim 1 , wherein the T_g of the polymeric side chains after the polymeric side chains are cleaved from the graft polymer is lower than the T_g of the graft polymer with the side chains still attached.

3. The chemically-amplified photoresist of Claim 1 or Claim 2, wherein the T_g of the graft polymer is from about 80 - 200° C, preferably from about 95 - 140° C.

4. The chemically-amplified photoresist of Claim 2 or Claim 3, wherein the plurality of polymeric side chains comprises a polymeric side chain having a T_g which is at least 10° C, preferably at least 20° C, less than the T_g of the backbone polymer.

5. The chemically-amplified photoresist of any one of the preceding claims, wherein the backbone polymer comprises a plurality of macromonomers, each macromonomer having an acid-cleavable moiety linking the macromonomer to the backbone polymer.

6. The chemically-amplified photoresist of Claim 5, wherein the acid-cleavable moiety is a ketal or acetal.

7. The chemically-amplified photoresist of any one of the preceding claims, wherein the backbone comprises acrylic or methacrylic monomers.

8. The chemically-amplified photoresist of Claim 5 or Claim 6, wherein the backbone polymer is a copolymer further comprising a plurality of second monomers which, optionally, are polymers or macromonomers.

9. The chemically-amplified photoresist of Claim 8, wherein the second monomers have low surface-energy substituents, such as partially-fluorinated alkyl or methylsilyl groups.

10. The chemically-amplified photoresist of Claim 8 or Claim 9, wherein each of the second monomers does not have an acid-cleavable moiety.

11. The chemically-amplified photoresist of Claim 10, wherein the ratio of the number of macromonomers having an acid-cleavable moiety to the number of the second macromonomers in the copolymer is from about 99:1 to about 1 :99.

12. A chemically-amplified photoresist, comprising a graft polymer having a backbone polymer with a plurality of acid-cleavable polymeric side chains, having the following formula:

wherein Ri is linked to the graft backbone polymer, and may be (for example) an alkyl chain (e.g., having from 1 to 4 carbon atoms), and may additionally comprise heteroatoms, such as oxygen; R2 is linked to the side-chain polymer, and may be (for example) an alkyl chain (e.g., having from 1 to 4 carbon atoms) and may additionally comprise heteroatoms, such as oxygen; R3 is the end-group of the side-chain polymer and may be (for example) hydrogen, chlorine, bromine, iodine, thiol, thioether, trithiocarbonate, dithioester, or xanthate; R4 is a protecting group on the side-chain polymer; and Rs is hydrogen, alkyl, or aryl.

13. The chemically-amplified photoresist of Claim 12, wherein the side chain polymer is of the formula:

wherein Si and S2 are, individually, hydrogen, methyl, ethyl, or higher alkanes, and Ti and T2 are, individually, organic protecting groups that may or may not become deprotected during photoresist exposure, post-exposure baking, and development, preferably alkyl groups, aryl groups, either alkyl or aryl groups that contain heteroatoms (e.g., oxygen, nitrogen, or sulfur), acid-cleavable protecting groups, or hydrogen.

14. The chemically-amplified photoresist of Claim 12 or Claim 13, wherein the T_g of the graft polymer is from about 80 - 200° C, preferably from about 95 - 140° C.

15. The chemically-amplified photoresist of any of Claims 12 - 14, wherein the plurality of polymeric side chains comprises a polymeric side chain having a T_g which is at least 10° C, preferably at least 20° C, less than the T_g of the backbone polymer.

16. A method for making a chemically-amplified photoresist graft polymer comprising a backbone polymer and a plurality of acid-cleavable polymeric side chains, the method comprising:

17. The method of making a chemically-amplified photoresist graft polymer according to Claim 16, wherein the polymeric moiety of the macromonomer comprises one or more hydrophobic protecting groups.

18. The method of making a chemically-amplified photoresist graft polymer according to Claim 16 or Claim 17, wherein the acid-cleavable linker is an alcohol or acid-labile functional group, such as a ketal or acetal.

19. The method of making a chemically-amplified photoresist graft polymer according to any one of Claims 16 - 18, further comprising isolating and drying the side-chain macromonomers prior to the polymerizing.

20. A method for making a resist layer on a surface of a semiconductor substrate, the method comprising:

applying a chemically-amplified photoresist, comprising a graft polymer having a backbone polymer with a plurality of acid-cleavable side chains, to the surface to form a photoresist layer;

selectively irradiating the photoresist layer, such that the photoresist layer comprises an irradiated region and an unirradiated region; and

baking the photoresist layer.

21. The method for making a resist layer on a surface of a substrate according to Claim 20, wherein the irradiating comprises the use of DUV, EUV or e-beam radiation.

22. The method for making a resist layer on a surface of a substrate according to Claim 20 or Claim 21 , wherein the acid-cleavable side chains are cleaved from the backbone polymer in the irradiated region, such that the irradiated region is hydrophilic.

23. The method for making a resist layer on a surface of a substrate according to any one of Claims 20 - 22, further comprising developing the photoresist layer after the baking, so as to remove the photoresist layer in the irradiated region or the unirradiated region.

24. The method for making a resist layer on a surface of a substrate according to Claim 23, wherein the developing comprises applying a solvent, such as alkaline water, to the photoresist layer to remove the irradiated region.