Resist composition

Abstract

A polymer for use as a resist in the manufacture of integrated circuits is provided. Additionally, a non-chemically amplified resist composition is provided, comprising a polymer having one or more cleavage portions comprising photodegradable chemical bonds configured to degrade preferentially upon exposure of the resist composition to electromagnetic radiation. Additionally, uses of such resist composition or polymer and a lithography method for incorporating such composition or polymer are provided.

Description

Technology Field

[0001] This application claims priority to U.S. provisional patent application 62 / 938,260 filed November 20, 2019 and U.S. provisional patent application 62 / 944,996 filed December 6, 2019, the full text of which is incorporated herein by reference. Background Technology

[0002] The present invention relates to a resist composition for lithography and a method for manufacturing a semiconductor using said resist composition. In particular, the present invention relates to a resist composition for use in EUV lithography.

[0003] A lithography device is a machine configured to apply a desired pattern onto a substrate. A lithography device can be used, for example, in the manufacture of integrated circuits (ICs). A lithography device can project a pattern onto a layer of radiation-sensitive material (resist) provided on a substrate, for example, from a patterning device (e.g., a mask).

[0004] The wavelength of radiation used by a lithography device to project a pattern onto a substrate determines the minimum size of the feature that can be formed on the substrate. A lithography device using EUV radiation, which is electromagnetic radiation with a wavelength in the range of 4-20 nm, can be used to form smaller features on a substrate than a conventional lithography device (e.g., one that can use electromagnetic radiation with a wavelength of 193 nm).

[0005] Known resists suitable for use with lithography are called chemically amplified resists (CARs) and are polymer-based. When exposed to electromagnetic radiation or an electron beam, the polymers of the CAR absorb photons or interact with electrons to generate secondary electrons. The generation of secondary electrons occurs in a manner where high-energy photons or electrons lose most of their energy. The secondary electrons in the resist diffuse and can generate additional secondary electrons at lower energies until their energy becomes lower than the energy required to break the bonds of the CAR or cause ionization. The generated electrons can excite photo-acid generators (PAGs) to catalyze subsequent decomposition and deblocking reactions, which alter the solubility of the CAR.

[0006] Alternative resist systems containing metal oxide nanoclusters for use with lithography, particularly EUV lithography, have been investigated to address the issues of CAR. These alternative resist systems contain metal oxide nanoparticles or nanoclusters that are prevented from clustering together by ligand shells. When exposed to EUV, photons are absorbed by the nanoparticles or nanoclusters, generating secondary electrons. These electrons break the bonds between the ligand and the nanoparticles or nanoclusters. This causes the nanoparticles or nanoclusters to cluster together, thereby altering the solubility of the resist. Since metal oxide nanoparticles have a larger EUV absorption cross-section than the carbon atoms in CAR, they are more likely to absorb EUV photons. Therefore, lower-intensity beams are required, which necessitate less power or shorter exposure times to EUV photons. Additionally, these alternative conversion mechanisms potentially exhibit lower chemical noise than CAR resist systems.

[0007] While this application generally refers to EUV lithography in its entirety, it is understood that the invention is not limited to EUV lithography and that the subject matter of the invention may be applicable to any other type of lithography, such as photolithography resists using electromagnetic radiation having a frequency higher or lower than that of EUV, or electron beam lithography. means of solving the problem

[0008] According to a first aspect of the present invention, a polymer for use as a resist in the manufacture of an integrated circuit is provided, said polymer having the following structure:

[0009]

[0010] n is an integer, A is a polymer chain subunit, and X is a photo-cleavable chemical bond sensitive to EUV.

[0011] It will be understood that the presence of photodegradable chemical bonds sensitive to EUV causes the polymer to degrade preferentially at these chemical bonds. The polymer chain subunits can be a single monomer or a chain containing two or more monomers.

[0012] The polymer chain subunit may include one or more of aliphatic, aromatic, linear, or cyclic hydrocarbon moiety.

[0013] Polymer chain subunits may include elements having an EUV atomic absorption cross-section larger than that of carbon, preferably larger than that of oxygen. By including elements with a larger EUV atomic absorption cross-section, it is possible to control the location within the polymer where incident EUV radiation is most likely to be absorbed. Absorption of EUV radiation causes bond cleavage. Therefore, by controlling the polymer portion most likely to absorb EUV radiation and providing the polymer with EUV-sensitive photodegradable chemical bonds, it is possible to control the manner in which the polymer is most likely to degrade upon exposure to EUV radiation. Since the polymer backbone is most likely to be made of carbon, it is desirable for the polymer's EUV absorption moiety to include elements that are more likely to absorb EUV radiation.

[0014] The polymer chain subunit may include a metal. The metal may be selected from Sn, Sb, Zr, Hf, In, and Pb. Metals are highly suitable as EUV radiation absorption moiety because they have a large EUV atomic absorption cross-section.

[0015] Photodegradable chemical bonds sensitive to EUV can be selected from esters, ethers, sulfides (thioethers), etc. These chemical bonds can be incorporated into polymer chains and include bonds that are easily cleavable. As such, these connections act as weak points in the polymer chain, causing the chain to decompose into chains of a specific length.

[0016] The polymer may include the following:

[0017] n

[0018] Here, Z is an element having an EUV atomic absorption cross-section larger than that of carbon, preferably larger than that of oxygen. N is, for example, an integer from 1 to 10. It will be understood that n can be greater than 10. Sub-units having n repeating units may be connected via weak bonds. When exposed to EUV radiation in this way, the weak bonds are preferentially broken, and sub-units having n repeating units are emitted. The photodegradable chemical bonds may be selected from esters, ethers, sulfides (thioethers), etc.

[0019] Polymers can be as follows:

[0020]

[0021] Here, Z is an element having an EUV atomic absorption cross-section larger than carbon, preferably larger than oxygen. In this example, photodegradable chemical bonds, namely ester groups, alternate with groups containing EUV absorption moiety. In the examples, it will be understood that ester groups are repeated with intervals between two or more groups containing EUV absorption moiety.

[0022] Polymers can be as follows:

[0023]

[0024] Here, Z is an element having an EUV atomic absorption cross-section larger than carbon, preferably larger than oxygen. In this example, photodegradable chemical bonds, i.e., ether groups, alternate with groups containing EUV absorption moiety. In the examples, it will be understood that ether groups are repeated with intervals between two or more groups containing EUV absorption moiety.

[0025] Polymers can be as follows:

[0026]

[0027] Here, Z is an element having an EUV atomic absorption cross-section larger than carbon, preferably larger than oxygen. In this example, photodegradable chemical bonds, namely sulfide (thioether) groups, alternate with groups containing EUV absorption moiety. In the examples, it will be understood that sulfide (thioether) groups are repeated with intervals between two or more groups containing EUV absorption moiety.

[0028] You will understand that these polymers contain a terminal group. The polymer is not limited to any specific terminal group. The terminal group can be CF3.

[0029] It is preferable to use a single polymer, but a mixture of one or more such polymers may be used.

[0030] According to a second aspect of the present invention, a non-chemically amplified resist composition is provided, comprising a polymer having at least one scission portion comprising a photodegradable chemical bond configured to be preferentially destroyed when the resist composition is exposed to electromagnetic radiation.

[0031] Resist compositions generally include chemically amplified resists or non-chemically amplified resists, such as spin-on metal oxide resists. All of these types of resist compositions have disadvantages.

[0032] In chemically amplified resists (CARs), there is substantial chemical noise originating from the mechanism of action of the CAR, primarily from acid and quencher noise. This chemical noise causes surface roughness and limits the size of achievable features. In particular, since the mechanism of action of the CAR is based on acid groups generated in the photocatalytic ionizing agent (PAG) that diffuse through the resist prior to the reaction, noise is inherent in the mechanism of action. Acid groups generated in the photocatalytic ionizing agent (PAG) of the chemically amplified resist diffuse from within the resist to the area of ​​the resist exposed to electromagnetic waves, contributing to blurring. Thus, the ultimate location where reactions causing changes in the solubility of the resist occur in the developer is not limited solely to the region where EUV photons (or other electromagnetic radiation in use) are incident on the resist. Furthermore, acids and quenchers in the resist are randomly dispersed. In small features, the absolute number of acids and quenchers is limited, resulting in Poisson noise. In addition, in the case of CAR systems, pattern collapse at low critical dimensions becomes a problem as a result of blur caused by the characteristics of the CAR system. Furthermore, as the size of the features to be produced decreases, an alternative resist platform is required. If a high dose is required, the resist must be exposed to an electromagnetic radiation source for a longer period. Consequently, the number of chips that can be produced on a single machine within a given time decreases.

[0033] Resists based on metal oxide nanoparticle systems also have drawbacks. Although metal oxide nanoparticle systems have greater EUV absorption than CAR systems, efficiency and blur cancel each other out; in systems with high conversion efficiency—that is, in the large number of electrons generated by incident EUV photons—a single photon can generate a large number of secondary electrons. As with CAR systems, these electrons can move through the system before causing chemical reactions to remove ligands, and this electron diffusion results in high blur. While the radius of metal oxide nanoparticles is typically about 0.3 to 1.0 nm, electrons generated by the absorption of EUV photons can diffuse by several nanometers. As such, electrons can diffuse toward particles adjacent to the particle that absorbed the EUV photon, potentially breaking the bonds between such adjacent particles and the ligands bound to them. This can cause blur and consequently lead to large local critical dimension uniformity (LCDU) values, both of which are undesirable.

[0034] As such, both CAR and MOR suffer from harmful stochastic effects that result in increased local critical dimension variations due to the statistical distribution of the most basic units of the resist material, particularly the distribution of photon generators within the polymer matrix.

[0035] The present invention has been made in consideration of the aforementioned problems of known resists, particularly EUV resists. By providing a polymer having weak bonds in the polymer chain, it is these weak bonds that are preferentially cleaved when the resist is exposed to electromagnetic radiation, particularly EUV radiation or radiation of much shorter wavelengths. Because there are parts within the polymer chain that are more easily cleaved, this has the advantage that the polymer chain breaks down into subunits having substantially the same molecular weight. When the resist is ultimately developed, these shorter subunits dissolve more readily in the developer than the original intact polymer. Because the polymer is designed so that the cleavage parts are more easily cleaved, the molecular weight distribution of the subunits generated upon exposure to electromagnetic radiation is narrow. Therefore, the time of the development process can be measured more accurately. The cleavage parts are preferably located within the main polymer chain so that when they break down, the existing polymer breaks down into shorter subunits. It will be understood that the resist composition may comprise a plurality of polymers as described herein, and that the polymers are preferably substantially the same. It will be understood that other polymers may be included if necessary.

[0036] The non-chemically amplified resist composition may be an organic material. Polymers are generally organic in nature, and it is possible to form the resist composition according to the present invention using such organic polymers.

[0037] The resist composition is preferably a single-component resist material. The resist composition is preferably an EUV resist composition, but may also be a resist composition used for shorter wavelengths.

[0038] By providing a single-component EUV resist material, many disadvantages of conventional resist compositions are overcome. In particular, CARs have features such as the statistical distribution of the molecular weight of the base polymer, the spatial distribution of photo-generating agents (as well as photo-generated acids), the spatial distribution of base additives, the diffusion of photo-generated acids and base additives, and the phase separation of protected and unprotected polymers. In MORs, these statistical distributions include the distribution of nanoparticle sizes and the statistical characteristics of nanoparticle aggregation and nanoparticle condensation reactions. The present invention solves these problems by providing a single-component resist material. In this way, the resist composition contains a uniform EUV resist material, thereby minimizing any statistical distribution. Because there are fewer factors to add to any statistical variation, the resist composition of the present invention exhibits lower resist stochastics. In particular, the resist composition of the present invention substantially or completely does not contain photo-generating agents and / or base quenchers.

[0039] A resist composition may include a polymer having a substantially uniform molecular weight. In conventional resist compositions, the molecular weight of the polymer constituting the resist material is non-uniform. As such, the molecular weight distribution of the polymer is relatively wide, resulting in a non-uniform resist material. By having polymer chains of substantially the same molecular weight, the resist composition is more uniform and has fewer stochastic effects.

[0040] The polymer may contain photodegradable chemical bonds at regular intervals along the length of the polymer. Thus, there may be a photodegradable chemical bond for every n-th subunit, where n is an integer. Thus, the photodegradable chemical bonds may be at integer intervals, for example, every 1, 1 / 2, 1 / 3, etc. For example, there may be photodegradable chemical bonds between all groups of 5 monomers (subunits). Because the chemical bonds are configured to break preferentially over other parts of the polymer chain, when exposed to electromagnetic radiation, which may be EUV radiation, the resist composition will preferentially degrade into smaller chains of length 5. While conventional polymeric resists degrade into chains of various lengths with a wide length or weight distribution, the polymer degradation products of the resist composition according to the present invention contain cleavage portions and have a narrow size distribution.

[0041] The polymer may comprise 10 to 30 subunits (repeating units). It will be understood that longer or shorter polymer chains may be used. The subunits may comprise a single monomer or two or more monomers. The subunits may comprise 1 to 10 monomers. It will be understood that the subunits may comprise more than 10 monomers.

[0042] The polymer may include an EUV absorption moiety.

[0043] Since the resist composition is highly suitable as an EUV resist, it is desirable to configure the polymer to include regions that readily absorb EUV radiation. In conventional CARs, the component that absorbs EUV radiation is typically the carbon backbone of the polymer. Although carbon can absorb EUV radiation, it absorbs it less readily than other parts, requiring higher power EUV radiation or longer exposure times. Furthermore, since EUV radiation can be absorbed at random points along the polymer, the locations where polymer chains break are random. This is undesirable because it not only increases power requirements or reduces the throughput of the lithography device but also increases the observed stochastic effects. As such, EUV-absorbing moietyes can have larger EUV absorption cross-sections than carbon. Oxygen is another common component of the polymer, which means that when exposed to electromagnetic radiation, such as EUV radiation or shorter wavelength radiation, the locations where polymer chains break are random. As such, EUV-absorbing moietyes can have larger EUV absorption cross-sections than oxygen. The provision of light, preferably EUV, photodegradable chemical bonds causes absorbed energy to cleave such bonds, thereby making the resist composition soluble. Since the resist material is a single-component material—that is, the resist material contains identical or substantially identical molecules—the polymers forming the resist material decompose into identical basic units, making the performance of the resist material more uniform and predictable when exposed to EUV radiation. By configuring the polymer to have specific EUV absorption moiety and predefined cleavage portions, the characteristics of the decomposition product can be finely controlled when the resist is exposed to electromagnetic radiation.

[0044] EUV absorption moiety may include metals. Metals generally have a larger EUV radiation absorption cross-section than carbon and oxygen. Predictable results can be obtained upon exposure to EUV radiation because the polymer comprising the resist material is configured to include these EUV absorption moiety and one or more photodegradable chemical bonds, and the resist material comprises a single-component EUV resist material. This is considered true because, without being bound by scientific theory, by providing a resist material containing only the same basic unit, the statistical distribution caused by including multiple components in previous resists is eliminated. In particular, the resist material of the present invention comprises a polymer having a number of identical or substantially identical components, namely EUV absorption moiety and one or more photodegradable chemical bonds, and having a substantially uniform molecular weight, thus having fewer factors causing stochastic effects.

[0045] The metal can be selected from Sn, Sb, Zr, Hf, In, and Pb. In practice, any metal that is non-radioactive and / or reactive and has an EUV absorption cross-section larger than hafnium may be used. These specific metals have large EUV absorption cross-sections.

[0046] The metal within the metal oxide nanoparticles or nanoclusters may comprise one or more alkali metals, alkaline earth metals, transition metals, lanthanides, actinides, or post-transition metals. Post-transition metals are metals located in the p-block of the periodic table. The metal may be tin. The metal may be hafnium. As previously mentioned, metals generally have a higher EUV absorption cross-section compared to carbon; therefore, resists containing metals are relatively less permeable to EUV radiation than resists that rely on carbon to absorb electromagnetic radiation. In particular, tin and hafnium exhibit excellent absorption of EUV radiation and etching resistance.

[0047] The resist material may have a Dill B parameter greater than about 6 µm-1, optionally greater than about 10 µm-1, optionally greater than about 15 µm-1, and optionally greater than about 20 µm-1.

[0048] The resist composition may be substantially free of photon generators. Since the composition of the present invention does not rely on the generation of acidic species to alter the resist material, the presence of photon generators is not necessary. By eliminating the presence of photon generators, inherent inaccuracies caused by the diffusion of acidic species can be avoided. The composition may be free of photon generators.

[0049] The resist composition substantially does not contain base additives or base quenchers. Base additives or base quenchers serve to react with the generated excess acid. In other words, since the present invention does not rely on the generation and reaction of acidic groups, any base additives or quenchers can be removed.

[0050] The composition may have a molar mass dispersion of 1 to about 1.2. The composition may have a molar mass dispersion of about 1 to 1.1. The composition may have a molar mass dispersion of about 1 to 1.05. It will be understood that in practice, it is not possible to provide a material in which all constituent polymers have exactly the same length. As such, it will be understood that there will inevitably be slight differences in polymer chain lengths. A molar mass dispersion close to 1 (1 indicates that all polymer chain lengths are the same, i.e., the standard deviation is 0) indicates that the molecular mass distribution is dense. As such, the resist has more uniform characteristics overall over its range.

[0051] The resist composition may be configured to decompose into soluble or volatile components upon exposure to EUV radiation. In this way, the resist can be a positive resist. In this manner, when the resist is exposed to EUV radiation, the exposed portions are designed to degrade or degrade and be removed, thereby forming a pattern. If one of the decomposition products is volatile, this component is removed from the resist, and there is no risk of resist re-formation. Due to the presence of EUV-absorbing moiety and cleavage portions—that is, weak linkages in the polymer chains—the polymer is configured to decompose into substantially uniform subunits.

[0052] The resist material may comprise aliphatic, aromatic, linear, or cyclic hydrocarbon moiety. The polymer generally comprises a carbon backbone or a series of carbon units connected to one another or to other chemical moiety to provide polymer chains. The carbon-carbon bonds of the polymer backbone are strong, particularly when part of an aromatic or cyclic chemical group, so they can remain intact while photodegradable chemical bonds degrade. As such, photodegradable chemical bonds preferably comprise bonds weaker than carbon-carbon bonds.

[0053] One or more cleavage portions containing photodegradable chemical bonds configured to be preferentially destroyed upon exposure of the resist composition to electromagnetic radiation may include chemical bonds weaker than the chemical bonds forming the polymer's backbone. In this way, weak bonds are preferentially broken, and the properties of the polymer's degradation products can be controlled.

[0054] One or more photodegradable chemical bonds may be selected from esters, ethers, sulfides (thioethers), or similar groups. If the chemical bonds include esters, carbon dioxide gas is generated when the chemical bonds are cleaved, which can prevent the reformation of the polymer. Since the polymer containing the resist material is configured to have one or more locations where polymer chain cleavage is more likely to occur, the polymer will be more likely to cleave at these locations. Accordingly, the products of EUV radiation-initiated decomposition of the polymer chains will be more consistent than those of previous resists that rely on chemical amplification.

[0055] The resist composition is preferably suitable for use with EUV. Preferably, the resist composition is also suitable for use with photons having frequencies higher or lower than EUV. The resist composition may also be suitable for use with electron beam lithography. The resist composition may be a photoresist composition.

[0056] According to a third aspect of the present invention, a resist for manufacturing an integrated circuit is provided, comprising a resist composition or a polymer according to the first or second aspect of the present invention.

[0057] According to a fourth aspect of the present invention, a use of a composition or polymer according to a first or second aspect is provided in a method for manufacturing an integrated circuit.

[0058] According to a fifth aspect of the present invention, the method comprises: a) providing a resist composition or polymer according to a first or second aspect to a semiconductor substrate; b) exposing the resist composition or polymer to a patterned EUV light beam or electron beam to form a pattern in the resist composition; and c) developing the resist or polymer to form a circuit pattern.

[0059] Electromagnetic radiation can be EUV. Electromagnetic radiation can have frequencies greater or smaller than EUV.

[0060] The method of the fourth aspect of the present invention may also include baking of a semiconductor substrate. Preferably, baking occurs after an electromagnetic radiation or electron beam exposure step. Brief explanation of the drawing

[0061] Now, embodiments of the present invention will be described merely as examples with reference to the attached schematic drawings, wherein: - FIG. 1 illustrates a lithography system comprising a radiation source and a lithography device that can be used to irradiate a resist composition of the present invention. - Figure 2 is a schematic diagram of a generalized polymer that is converted from an insoluble form to a soluble form upon exposure to EUV radiation. - Figure 3 is a schematic diagram of an example of an insoluble polymer that converts into a soluble form and releases gas when exposed to EUV radiation. Specific details for implementing the invention

[0062] FIG. 1 illustrates a lithography system that can be used to irradiate a resist composition of the present invention. The lithography system includes a radiation source (SO) and a lithography device (LA). The radiation source (SO) is configured to generate an extreme ultraviolet (EUV) radiation beam (B). The lithography device (LA) includes an illumination system (IL), a support structure (MT) configured to support a patterning device (MA) (e.g., a mask), a projection system (PS), and a substrate table (WT) configured to support a substrate (W). A layer of the resist composition according to an embodiment of the present invention is provided on the substrate (W). The illumination system (IL) is configured to regulate the radiation beam (B) before it is incident on the patterning device (MA). The projection system is configured to project the radiation beam (B) (now patterned by the mask (MA)) onto the substrate (W). The substrate (W) may include a pre-formed pattern. In this case, the lithography device aligns the patterned radiation beam (B) with a pre-formed pattern on the substrate (W).

[0063] The radiation source (SO), the illumination system (IL), and the projection system (PS) can all be configured and arranged to be isolated from the external environment. A gas (e.g., hydrogen) at a pressure lower than atmospheric pressure can be supplied to the radiation source (SO). A vacuum can be supplied to the illumination system (IL) and / or the projection system (PS). A small amount of gas (e.g., hydrogen) at a pressure much lower than atmospheric pressure can be supplied to the illumination system (IL) and / or the projection system (PS).

[0064] The radiation source (SO) illustrated in FIG. 1 is a type that can be referred to as a laser generating plasma (LPP) source. A laser (1), which may be, for example, a CO2 laser, is arranged to deposit energy onto a fuel, such as tin (Sn), provided from a fuel emitter (3) via a laser beam (2). Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may be, for example, in liquid form, or may be, for example, a metal or an alloy. The fuel emitter (3) may include a nozzle configured to direct the tin in the form of a droplet along a trajectory toward, for example, a plasma forming region (4). The laser beam (2) is incident on the tin in the plasma forming region (4). When laser energy is deposited onto the tin, a plasma (7) is generated in the plasma forming region (4). Radiation, including EUV radiation, is emitted from the plasma (7) during the de-excitation and recombination of plasma ions.

[0065] EUV radiation is collected and focused by a near-vertical incident radiation collector (5) (sometimes more commonly referred to as a vertical incident radiation collector). The collector (5) may have a multilayer structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as 13.5 nm). The collector (5) may have an elliptical configuration having two elliptical foci. As described below, the first foci may be in the plasma forming region (4), and the second foci may be in the intermediate foci (6).

[0066] The laser (1) can be separated from the radiation source (SO). In this case, the laser beam (2) can be transferred from the laser (1) to the radiation source (SO) with the help of a beam transfer system (not shown) including, for example, a suitable directional mirror and / or a beam expander and / or other optical system. The laser (1) and the radiation source (SO) together can be considered as a radiation system.

[0067] Radiation reflected by the collector (5) forms a radiation beam (B). The radiation beam (B) is focused at a point (6) to form an image of the plasma forming area (4) acting as a virtual radiation source for the illumination system (IL). The point (6) where the radiation beam (B) is focused may be referred to as an intermediate focus. The radiation source (SO) is arranged so that the intermediate focus (6) is located at or near the opening (8) in the enclosure structure (9) of the radiation source.

[0068] A radiation beam (B) passes through an illumination system (IL) configured to regulate the radiation beam from a radiation source (SO). The illumination system (IL) may include a faceted field mirror device (10) and a faceted pupil mirror device (11). The faceted field mirror device (10) and the faceted pupil mirror device (11) together provide a radiation beam (B) having a desired cross-sectional shape and a desired angular distribution. The radiation beam (B) passes from the illumination system (IL) and is incident on a patterning device (MA) supported by a support structure (MT). The patterning device (MA) reflects and patterns the radiation beam (B). The illumination system (IL) may include other mirrors or devices in addition to or instead of the faceted field mirror device (10) and the faceted pupil mirror device (11).

[0069] Following reflection from the patterning device (MA), the patterned radiation beam (B) enters the projection system (PS). The projection system includes a plurality of mirrors configured to project the radiation beam (B) onto a substrate (W) supported by a substrate table (WT). The projection system (PS) can form an image having features smaller than the corresponding features on the patterning device (MA) by applying a reduction factor to the radiation beam. For example, a reduction factor of 4 may be applied. Although the projection system (PS) has two mirrors in FIG. 1, the projection system may include any number of mirrors (e.g., six mirrors).

[0070] The radiation source (SO) illustrated in FIG. 1 may include components not illustrated. For example, a spectral filter may be provided to the radiation source. The spectral filter may be substantially transparent to EUV radiation but may substantially block other wavelengths of radiation, such as infrared.

[0071] The term "EUV radiation" may be considered to include electromagnetic radiation having wavelengths within the range of 4-20 nm, for example, within the range of 13-14 nm. EUV radiation may have wavelengths within the range of 4-10 nm, such as less than 10 nm, for example, 6.7 nm or 6.8 nm.

[0072] Figure 1 illustrates a radiation source (SO) as a laser-produced plasma (LPP) source, but any suitable source may be used to generate EUV radiation. For example, EUV emitting plasma can be generated by using an electric discharge to convert a fuel (e.g., tin) into a plasma state. This type of radiation source may be referred to as a discharge-produced plasma (DPP) source. The discharge may be generated by a power supply that can form part of the radiation source, or it may be a separate entity connected to the radiation source (SO) via an electrical connection.

[0073] FIG. 2 illustrates the mechanism of action of polymer chain cleavage in a resist. The polymer comprises units (A) containing EUV-absorbing moiety connected via EUV-sensitive linkages (X). Since chemical bonds or connections between individual monomers are weaker than bonds within the monomers, they are preferentially broken down during EUV exposure. The polymer is broken down into smaller molecules that can be removed by a developer or vaporization. In this way, the solubility of the resist material is converted. Due to the uniform chain structure and the uniform chain length of the reaction products, any chemical or material-related impurities that may occur are removed.

[0074] FIG. 3 illustrates the mechanism of action of an exemplary polymer comprising a resist material. The insoluble polymer comprises a plurality of monomer units containing an EUV-absorbing moiety (Z). The EUV-absorbing moiety has an atomic absorption cross-section larger than that of carbon, preferably larger than that of oxygen. Thus, incident EUV radiation is preferably absorbed by the moiety (Z), and the bond between the cyclic hydrocarbon and the ester group is broken. This irreversibly releases carbon dioxide and makes the resist soluble.

[0075] The foregoing description is for illustrative purposes only and is not limiting. Accordingly, it will be apparent to those skilled in the art that modifications to the invention may be made as described without departing from the scope of the claims.

[0076] The present invention relies on providing portions within a polymer that are more likely to absorb incident EUV radiation than other parts, and weak bonds within the polymer that degrade preferentially upon exposure to EUV radiation. By configuring the polymer in this way, the manner in which the polymer degrades upon exposure to EUV radiation can be controlled. Since the cleavage products are all substantially identical, the stochastic effects observed in conventional resist materials are eliminated.

Claims

Claim 1 As a polymer for use as a resist in the manufacture of an integrated circuit, the polymer is selected from one of the following: a) b) c) d) Z is an element with an EUV atomic absorption cross-section larger than that of carbon, and n is a positive integer, a polymer. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 A non-chemically amplified resist composition comprising a polymer having at least one scission portion comprising a photodegradable chemical bond configured to be preferentially destroyed when the resist composition is exposed to electromagnetic radiation, wherein the polymer is selected from one of the following: a) b) c) d) A resist composition in which Z is an element having an EUV atomic absorption cross-section larger than carbon, and n is a positive integer. Claim 8 In claim 7, the non-chemically amplified resist composition is an organic resist composition. Claim 9 In claim 7, the composition is a resist composition that is a single-component resist material. Claim 10 In claim 7, the polymer constituting the resist composition has a substantially uniform molecular weight, the resist composition. Claim 11 In claim 7, the polymer comprises 10 to 30 sub-units, a resist composition. Claim 12 A resist composition according to claim 7, wherein a photodegradable chemical bond exists in each nth subunit. Claim 13 In claim 7, the resist composition comprises photodegradable chemical bonds at regular intervals along the length of the polymer. Claim 14 In claim 7, the resist composition wherein the polymer comprises at least one EUV absorbing moiety. Claim 15 A lithography method comprising: a. providing a resist composition or polymer according to any one of claims 1, 7 to 14 to a semiconductor substrate; b. exposing the resist composition or polymer to a patterned EUV light beam or electron beam to form a pattern on the resist composition or polymer; and c. developing the resist or polymer to form a circuit pattern. Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 delete Claim 21 delete Claim 22 delete Claim 23 delete Claim 24 delete Claim 25 delete Claim 26 delete Claim 27 delete

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