Pellicle membrane for lithographic apparatus

Abstract

A pellicle membrane is provided that includes an emissive crystal in a matrix that includes at least one element that forms a chemical bond with silicon having a bond dissociation energy of at least 447 kJ mol-1. A method of manufacturing such a pellicle membrane, a pellicle assembly comprising such a pellicle membrane, and a lithographic apparatus comprising such a pellicle assembly or pellicle membrane are also provided. The use of molybdenum silicon sulfide, molybdenum silicon oxide, molybdenum silicon selenide or molybdenum silicon fluoride in pellicle membranes and the use of such pellicle membranes, pellicle assemblies or lithographic apparatuses in lithographic apparatuses or methods are also described.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to European application No. 22169417.7 filed on April 22, 2022 and European application No. 22200334.5 filed on October 7, 2022, and the entire contents of these European applications are incorporated herein by reference. Technical Field

[0003] The present invention relates to a pellicle diaphragm for a lithography device, a component for a lithography device, a method for manufacturing the pellicle diaphragm, use of molybdenum silicon sulfide, molybdenum silicon oxide, molybdenum silicon selenide, or molybdenum silicon fluoride in the pellicle diaphragm, and use of the pellicle diaphragm in a lithography device or method. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern onto a substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] The wavelength of radiation used by a lithographic apparatus to project a pattern onto a substrate determines the minimum size of a feature that can be formed on the substrate. A lithographic apparatus using EUV radiation (electromagnetic radiation having a wavelength in the range of 4 nm to 20 nm) can be used to form smaller features on a substrate than a conventional lithographic apparatus (which may, for example, use electromagnetic radiation having a wavelength of 193 nm).

[0006] The lithographic apparatus includes a patterning device (e.g., a mask or reticle). Radiation is provided to pass through or reflect from the patterning device to form an image on a substrate. A diaphragm assembly (also referred to as a pellicle) may be provided to protect the patterning device from airborne particles and other forms of contamination. Contamination on the surface of the patterning device may cause manufacturing defects on the substrate.

[0007] A pellicle may also be provided for protecting optical components other than the patterning device. A pellicle may also be used to provide a path for lithographic radiation between sealed regions of a lithographic apparatus. A pellicle may also be used as a filter (such as a spectral purity filter) or as part of a dynamic gas lock of a lithographic apparatus.

[0008] The mask assembly can include a pellicle that protects a patterning device (e.g., a mask) from particle contamination. The pellicle can be supported by a pellicle frame to form a pellicle assembly. The pellicle can be attached to the frame, for example, by gluing or otherwise attaching the pellicle boundary region to the frame. The frame can be permanently or removably attached to the patterning device.

[0009] Since the pellicle is present in the optical path of the EUV radiation beam, it is desirable for the pellicle to have a high EUV transmittance. A high EUV transmittance allows a greater proportion of the incident radiation to pass through the pellicle. Additionally, reducing the amount of EUV radiation absorbed by the pellicle can reduce the operating temperature of the pellicle. Since the transmittance depends at least in part on the thickness of the pellicle, it is desirable to provide a pellicle that is as thin as possible while maintaining a reliable strength sufficient to withstand the sometimes hostile environment within a lithographic apparatus.

[0010] Therefore, there is a need to provide a pellicle that can withstand the harsh environment of a lithographic apparatus, particularly an EUV lithographic apparatus. There is a particular need to provide a pellicle that can withstand higher powers than previously possible. There is also a need to provide a pellicle membrane that limits or eliminates contamination of the lithographic apparatus due to release of material from the pellicle membrane, which may be referred to as hydrogen-induced outgassing.

[0011] Although the present application generally refers to pellicles in the context of lithographic apparatus, and in particular EUV lithographic apparatus, the present invention is not limited only to pellicles and lithographic apparatus, and it will be appreciated that the subject matter of the present invention may be used in any other suitable apparatus or situation.

[0012] For example, the method of the present invention may be equally applied to spectral purity filters. Some EUV sources, such as those that use plasma to generate EUV radiation, emit not only desired "in-band" EUV radiation, but also unwanted (out-of-band) radiation. This out-of-band radiation is most notably in the deep UV (DUV) radiation range (100 nm to 400 nm). Furthermore, in the case of some EUV sources, such as laser-generated plasma EUV sources, the radiation from the laser, typically at 10.6 microns, exhibits significant out-of-band radiation.

[0013] In lithographic equipment, spectral purity is required for several reasons. One reason is that the resist is sensitive to radiation of out-of-band wavelengths, and therefore the image quality of the pattern applied to the resist can deteriorate when the resist is exposed to such out-of-band radiation. In addition, out-of-band infrared radiation, such as the 10.6 micron radiation in some laser-generated plasma sources, causes unwanted and unnecessary heating of the pattern forming device, substrate, and optics within the lithographic equipment. This heating may cause damage to these components, reduced life of these components, and / or defects or deformation of the pattern projected onto and applied to the substrate coated with the resist.

[0014] A typical spectral purity filter may, for example, be formed from a silicon base structure (e.g., a silicon grid, or other member provided with holes) coated with a reflective metal such as molybdenum. In use, a typical spectral purity filter may be subjected to high thermal loads from, for example, incident infrared and EUV radiation. The thermal load may result in temperatures of the spectral purity filter exceeding 800°C. Under high thermal loads, the coating may delaminate due to differences in the linear expansion coefficients between the reflective molybdenum coating and the underlying silicon support structure. Delamination and decomposition of the silicon base structure is accelerated by the presence of hydrogen, which is typically used as a gas in the environment in which the spectral purity filter is used in order to inhibit debris (e.g., debris such as particles) from entering or leaving certain parts of the lithographic apparatus. Thus, a spectral purity filter may be used as a pellicle, and vice versa. Therefore, references to a "pellicle" in this application are also references to a "spectral purity filter". Although reference is primarily made to a pellicle in this application, all features may equally apply to a spectral purity filter.

[0015] The present invention has been contemplated in an attempt to address at least some of the problems identified above. Summary of the invention

[0016] According to a first aspect of the present disclosure, there is provided a pellicle membrane, comprising an emitting crystal in a matrix, wherein the matrix comprises a silicon-based pellicle having a thermal conductivity of at least 447 kJ mol -1 Or at least one element that chemically bonds with a bond dissociation energy of at least 4.6 eV.

[0017] The choice of material for the pellicle membrane is selected based on criteria such as, inter alia, thermodynamic reduction and oxidation stability, hydride formation, volatility tendency, EUV transmittance, EUV resistance, heat resistance. It has been found that the bond dissociation energy of the material forming the pellicle membrane is also an important selection criterion. In particular, the presence of bonds in the matrix that are stronger than silicon-carbon bonds (3.6 eV) means that the movement and eventual outgassing of material (such as silicon) from the membrane is reduced. Without wishing to be bound by scientific theory, it is believed that the bonds in the matrix material are less susceptible to release by bond breaking events and therefore exhibit less and slower diffusion. In other words, the expected bond dissociation energy according to the present disclosure is equal to or greater than the bond dissociation energy of silicon and carbon plus 1 eV, i.e. 3.6 eV + 1 eV = 4.6 eV, which is equal to 447 kJ mol -1 or larger.

[0018] Elements that can form such a strong bond with silicon include sulfur, oxygen, selenium, and fluorine. In other words, the minimum bond dissociation energy may be 4.6 eV.

[0019] It has been found that a pellicle membrane comprising metal silicide crystals in a sulfur-containing matrix exhibits higher EUV transmittance than an otherwise equivalent pellicle membrane comprising a nitride (e.g., silicon molybdenum nitride). In addition, the Si-S bonds in the pellicle membrane matrix have higher bond dissociation energies than Si-N bonds in a pellicle membrane matrix comprising a nitride. Although oxygen, selenium, and fluorine have higher EUV absorption coefficients than nitrogen or amorphous carbon, the bond dissociation energies of oxygen, selenium, and fluorine with silicon are greater than the bond dissociation energies of nitrogen and amorphous carbon with silicon, so there will be less outgassing of materials from the pellicle membrane, but possibly at the expense of transmittance. The higher bond dissociation energy causes fewer bond breaking events when photons are incident on the pellicle membrane. This situation has the consequence that there is less material migration, such as silicon, via the matrix material to the outer surface of the pellicle membrane, which in turn causes less outgassing of such materials, such as silicon. In addition, during the synthesis of the pellicle membrane according to the present disclosure, there is less silicon available for incorporation into the metal silicide crystals, compared to pellicle membranes that rely on a substrate that essentially only includes silicon. This results in the formation of more metal-rich crystals, which are assessed to provide the pellicle membrane according to the present disclosure with a higher thermal emissivity than a membrane of the same thickness that includes a silicon substrate. Sulfur has a lower EUV absorption coefficient than nitrogen and carbon and also has a higher bond dissociation energy, so the sulfur bonds are less likely to break in use. Although silicon has a lower EUV absorption coefficient than sulfur, silicon has a lower bond dissociation energy and is therefore more likely to cause outgassing of silicon. In addition, there is no suspicion that sulfur contributes significantly to contamination of optical devices within lithographic equipment.

[0020] The sulfur-containing matrix may include silicon sulfide. The sulfur-containing matrix may consist of silicon sulfide. The matrix may include or consist of silicon oxide, silicon selenide, or silicon fluoride, or one or more combinations of any of the matrix materials described herein. Embodiments of the present invention include a pellicle membrane comprising metal silicide crystals in a sulfur-containing matrix, wherein the matrix comprises silicon sulfide.

[0021] The emitting crystal may include one or more of a metal carbide, a metal boride, a metal nitride, a metal fluoride, a metal silicide, or a metal. The metal (which may be a metal of any of the aforementioned compounds or elemental metals) may be selected from one or more of the following: molybdenum, zirconium, yttrium, lanthanum, scandium, niobium, iridium, chromium, vanadium, platinum, rhodium, hafnium, and ruthenium. Yttrium oxide, zirconium oxide, hafnium oxide, and carbon nitride show a specific potential as a matrix material for a diaphragm membrane, because yttrium oxide, zirconium oxide, hafnium oxide, and carbon nitride have an ultimate tensile strength similar to that of silicon and include bonds with a bond dissociation energy greater than 4.6 eV. Molybdenum silicide crystals are more emissive than silicon and therefore contribute to increasing the emissivity of the diaphragm membrane, thereby reducing the operating temperature of the diaphragm at a given power. Similarly, other emissive crystals according to the present disclosure serve to increase the emissivity of the pellicle diaphragm, thereby reducing the operating temperature of the diaphragm at a given power.

[0022] The emissive crystal may comprise one or a combination of Mo5Si3 and Mo3Si. This provides the crystal with an increased proportion of metal, thereby increasing the emissivity of such a metal silicide crystal.

[0023] The emitting crystal may include MoSi 2-x Where the metal silicide is relatively metal-rich, the emissivity increases and the amount of silicon that can migrate through the pellicle membrane and be outgassed decreases. It will be appreciated that molybdenum disilicide crystals may be used to include sulfur in the matrix for reducing the total amount of silicon in the pellicle membrane.

[0024] The sulfur-containing matrix may have SiS 2-y wherein 0 ≤ y < 2. It is believed that including sulfur in the pellicle membrane reduces outgassing by strongly bonding the sulfur to the silicon, thereby inhibiting silicon migration and outgassing.

[0025] The pellicle membrane may at least partially have the molecular formula Mo a Si b S c, wherein 0 < a ≤ 30, 50 ≤ b ≤ 90 and 0 < c ≤ 50 (in mol %). In an embodiment, 10 ≤ a ≤ 30 (in mol %). In an embodiment, 60 ≤ b ≤ 70 (in mol %). In an embodiment, 20 ≤ c ≤ 30 (in mol %). The thermodynamic stability of the pellicle membrane may depend on the relative amounts of the metal, silicon and sulfur. The amount of molybdenum provides a suitable emissivity level without sacrificing transmittance. The amount of sulfur is controlled to avoid the formation of a gas phase at certain temperatures and also to avoid unwanted oxidation. The amount of silicon is controlled to reduce the possibility of outgassing of silicon while providing sufficient strength to the pellicle membrane. The pellicle membrane may at least partially include MoSiN or MoSiSi.

[0026] The pellicle membrane may comprise silicon and a metal, preferably molybdenum, and the ratio of Si:metal (Mo) (in mol%) may deviate from 2.0. In other words, the Si:metal ratio is below the stoichiometric value, i.e., below the stoichiometric value of silicon. In this way, the pellicle membrane is relatively metal-rich, which increases the emissivity of the pellicle membrane while also reducing the likelihood of silicon outgassing. This also allows for thinner membranes than would be the case with stoichiometric amounts of silicon and molybdenum.

[0027] The pellicle membrane may have an EUV transmittance of 90% or greater in a single pass.

[0028] The thickness of the pellicle membrane may be about 10 nm to about 100 nm. The thickness of the pellicle membrane is preferably 18 nm or less. In particular, when forming a pellicle membrane with silicon having a conductivity greater than 447 kJ mol -1 In the case of an element having a bond dissociation energy of 1000 Å from group VIA of the periodic table, specifically oxygen, sulfur, or selenium, in order to have no free silicon in the membrane matrix, the thickness of the membrane must not exceed 18 nm. In an embodiment, the thickness of the pellicle membrane is 15 nm or less. In particular, in the case of a bond with silicon having a bond dissociation energy of greater than 447 kJ mol -1 In the case of a bond dissociation energy of 100 Å for an element from group VIIA of the periodic table, in particular fluorine, in order to have no free silicon in the membrane matrix, the thickness of the membrane must not exceed 15 nm.

[0029] The diaphragm may be composed of molybdenum silicide crystals in a silicon sulfide, silicon oxide, silicon selenide, or silicon fluoride matrix. It should be understood that unintentional trace contaminants may be present due to manufacturing and material tolerances. The contaminants may be present in amounts that are insignificant to the performance of the diaphragm. In such embodiments, no additional elements are intentionally included.

[0030] The pellicle membrane may include a core of MoSiN, MoSiSi, or MoSiC and a cap layer including any of the materials described in the first aspect of the present disclosure. Such a cap layer does not necessarily have to be the outermost layer, and there may be another cap layer that protects the cap layer from the lithography environment.

[0031] According to a second aspect of the present disclosure, there is provided a method of manufacturing a pellicle diaphragm according to the first aspect of the present disclosure, wherein the method comprises sputtering, optionally co-sputtering.

[0032] Sputtering, preferably co-sputtering, provides the exact composition of the pellicle membrane to be controlled, thereby allowing the manufacture of pellicle membranes according to the present disclosure.

[0033] According to a third aspect of the present disclosure, a pellicle assembly is provided, the pellicle assembly comprising the pellicle membrane according to the first aspect of the present disclosure. The pellicle assembly may include additional elements as conventionally found in pellicle assemblies. For example, the pellicle assembly may include a frame that can support the pellicle membrane.

[0034] According to a fourth aspect of the present disclosure, a lithography device is provided, wherein the lithography device comprises the pellicle diaphragm according to the first aspect or the pellicle assembly according to the third aspect of the present disclosure.

[0035] According to a fifth aspect of the present invention, there is provided a use of molybdenum silicon sulfide, molybdenum silicon oxide, molybdenum silicon selenide, or molybdenum silicon fluoride in a pellicle diaphragm.

[0036] The pellicle membrane may be the pellicle membrane according to any aspect of the present disclosure. In an embodiment, the pellicle membrane may at least partially have a molecular formula Mo a Si b S c , where 0 < a ≤ 30, 50 ≤ b ≤ 90 and 0 < c ≤ 50 (in mol %).

[0037] According to a sixth aspect of the present invention, there is provided a use of a pellicle diaphragm, a pellicle assembly, or a lithography device according to the first, third or fourth aspect of the present disclosure in a lithography device or method.

[0038] It will be appreciated that features described with respect to one embodiment may be combined with any features described with respect to another embodiment, and that all such combinations are expressly contemplated and disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which corresponding reference characters indicate corresponding parts, and in which:

[0040] Figure 1 depicts a lithographic apparatus according to an embodiment of the invention; and

[0041] Figure 2 Depicts a sheet membrane assembly having a composite membrane.

[0042] The features and advantages of the present invention will be apparent from the detailed description set forth above in conjunction with the accompanying drawings, in which similar reference numerals identify corresponding elements throughout. In the accompanying drawings, the same reference numerals generally indicate the same, functionally similar, and / or structurally similar elements. DETAILED DESCRIPTION

[0043] Figure 1 A lithography system according to the invention is shown comprising a pellicle 15 (also referred to as a diaphragm assembly). The lithography system comprises a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B. The lithography apparatus LA comprises 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. The illumination system IL is configured to condition 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 comprise a previously formed pattern. In such a case, the lithography apparatus aligns the patterned radiation beam B with the pattern previously formed on the substrate W. In such an embodiment, the pellicle 15 is depicted in the path of the radiation and protects the patterning device MA. It will be appreciated that the pellicle 15 may be located at any desired location and may be used to protect any of the mirrors in the lithography apparatus.

[0044] The radiation source SO, the illumination system IL, and the projection system PS may all be constructed and arranged such that the radiation source SO, the illumination system IL, and the projection system PS may be isolated from the external environment. A gas (e.g., hydrogen) at a pressure below atmospheric pressure may be provided in the radiation source SO. A vacuum may be provided in the illumination system IL and / or the projection system PS. A small amount of gas (e.g., hydrogen) at a pressure sufficiently below atmospheric pressure may be provided in the illumination system IL and / or the projection system PS.

[0045] Figure 1The radiation source SO shown in is of a type that may be referred to as a laser produced plasma (LPP) source. A laser, which may be, for example, a CO2 laser, is arranged to deposit energy via a laser beam into a fuel, such as tin (Sn), provided from a fuel emitter. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may, for example, be in liquid form and may, for example, be a metal or an alloy. The fuel emitter may include a nozzle configured to direct tin, for example in the form of droplets, along a trajectory towards a plasma formation region. The laser beam is incident on the tin at the plasma formation region. The deposition of laser energy into the tin generates a plasma at the plasma formation region. Radiation, including EUV radiation, is emitted from the plasma during de-excitation and recombination of ions of the plasma.

[0046] EUV radiation is collected and focused by a near normal incidence radiation collector (sometimes more generally referred to as a normal incidence radiation collector). The collector 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 may have an elliptical configuration having two elliptical foci. The first focus may be at the plasma formation region, and the second focus may be at an intermediate focus, as discussed below.

[0047] The laser may be separate from the radiation source SO. In such a case, the laser beam may be transferred from the laser to the radiation source SO by means of a beam delivery system (not shown) comprising, for example, suitable directional mirrors and / or beam expanders and / or other optical devices. The laser and the radiation source SO may together be considered a radiation system.

[0048] The radiation reflected by the collector forms a radiation beam B. The radiation beam B is focused at a point to form an image of the plasma formation region, which image serves as a virtual radiation source for illuminating the system IL. The point at which 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 is located at or near an opening in an enclosure of the radiation source.

[0049] The radiation beam B is transmitted from the radiation source SO to the illumination system IL, which is configured to condition the radiation beam. 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 the radiation beam B with a desired cross-sectional shape and a desired angular distribution. The radiation beam B is transmitted from the illumination system IL and is incident on a pattern forming device MA held by a support structure MT. The pattern forming device MA reflects and patterns the radiation beam B. In addition to the faceted field mirror device 10 and the faceted pupil mirror device 11 or instead of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may also include other mirrors or devices.

[0050] After reflection from the patterning device MA, the patterned radiation beam B enters the projection system PS. The projection system comprises a plurality of mirrors 13, 14 configured to project the radiation beam B onto a substrate W held by a substrate table WT. The projection system PS may apply a reduction factor to the radiation beam so as to form an image having features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 may be applied. Although the projection system PS is Figure 1 There are two mirrors 13, 14, but the projection system may include any number of mirrors (eg, six mirrors).

[0051] Figure 1 The radiation source SO shown in FIG. 1 may include components not shown. For example, a spectral filter may be provided in the radiation source. The spectral filter may transmit EUV radiation to a large extent, but may block radiation of other wavelengths, such as infrared radiation, to a large extent.

[0052] In an embodiment, the membrane assembly 15 is a pellicle of a pattern forming device MA for EUV lithography. The membrane assembly 15 of the present invention can be used for a dynamic gas lock or for a pellicle or for another purpose. In an embodiment, the membrane assembly 15 includes a membrane formed by at least one membrane layer having an emissivity of 0.3 or higher. To ensure maximum EUV transmission and minimized impact on imaging performance, the membrane is preferably supported only at the boundaries.

[0053] Figure 2is a schematic depiction of a pellicle assembly 15 according to the present disclosure. The pellicle assembly includes a support 16 configured to support a pellicle membrane 17. In the figure, the support 16 is presented as two separate elements, but this need not be the case and the support 16 can be in the form of a boundary surrounding the pellicle membrane 17. The pellicle membrane 17 includes a cap layer 18, which is configured to protect the pellicle membrane 17, in particular the emissive layer 19 from degradation. The cap layer can be any known cap layer and the present disclosure is not specifically limited to any particular cap layer material. The emissive layer 19 includes a substrate 20, which provides the required pre-tension and strength. Because the pellicle membrane 17 is subjected to pressure differences when in use and must adapt to such pressure differences, pre-tension is required. The substrate material 20 can include one or more of the following: elemental silicon, silicon oxide, silicon fluoride, silicon sulfide, or silicon selenide. The emissive layer 19 includes thermally emitting crystals 21 disposed in the substrate 20. Thermally emitting crystal 21 is included to increase the thermal emissivity of pellicle membrane 17, thereby allowing the pellicle membrane to operate at a lower temperature than would otherwise be the case at a given power, or to operate at the same temperature as a pellicle membrane that does not include an emissive crystal but at a higher power. Thermally emitting crystal 21 may include one or more of a metal carbide, a metal boride, a metal nitride, a metal fluoride, a metal silicide, or a metal. The metal may be selected from one or more of the following: molybdenum, zirconium, yttrium, lanthanum, scandium, niobium, iridium, chromium, vanadium, platinum, rhodium, hafnium, and ruthenium.

[0054] If the patterning device MA is not protected, contamination may require cleaning or discarding the patterning device MA. Cleaning the patterning device MA interrupts valuable manufacturing time and discarding the patterning device MA is costly. Replacing the patterning device MA also interrupts valuable manufacturing time.

[0055] The present invention is directed to reducing hydrogen-induced outgassing (HIO) from Si-containing species of a metal silicide composite (MSC) EUV pellicle under EUV scanner operating conditions. In an embodiment, the MSC pellicle comprises an emissive metal-silicide (MoSi x ) crystals and a matrix providing flexibility and strength, the matrix consisting of a compound in which silicon is bonded to a secondary element "ψ", the matrix being called Si-ψ y Substrate. An MSC material selection parameter may be the "bond dissociation energy (BDE)" of the Si-ψ bonds in the matrix. The BDE of the Si-ψ bonds in the matrix governs the breaking of the Si-ψ bonds during scanner exposure, which produces free Si species that can diffuse to the external pellicle surface, where the free Si species can leave the pellicle via the HIO process. A high Si-ψ BDE thus results in a weakened HIO process. BDE as a parameter for selecting MSC pellicle materials is described herein.

[0056] The present invention is a novel EUV surface film composite MoSi-ψ material combination, wherein ψ = S, O, Se or F. The composite layer has MoSi x Crystal and Si-ψ y For example, in the case of ψ = S, Si-S 2-y The matrix material may exhibit even higher EUV transmission (EUVT). For example, Si-S bonds in the matrix have higher bond dissociation energy (BDE) than Si-N in a SiN matrix; as stated, a higher BDE causes fewer bond breaking events when photons are incident on the material, and may cause a smaller amount of Si to migrate through the matrix material to the outer surface, which therefore causes less Si outgassing. Based on the BDE of Si-S and other compositions described herein, the pellicle membranes of the present disclosure exhibit reduced outgassing compared to other composite pellicle solutions such as MoSiN, MoSiSi, and MoSiC.

[0057] In addition, compared with the MoSi-ψ concept with Si(-Si) as the matrix where ψ=Si, the MoSiS embodiments described herein have Si-S as the matrix. 2-y , Si-S as the matrix 2-y Involving the emission of MoSi in a material including a tensile core x crystal), there is a x Less Si in the crystal allows the formation of a crystal richer in Mo content, which provides a new composite with higher thermal emissivity than a MoSiSi layer of equal thickness. The crystals in the MoSi-S film can be engineered to include Mo5Si3 rich in Mo, since some of the Si is bound to the matrix and not to the emitting crystal, however for the poorly emitting MoSiSi this cannot happen and the crystal includes MoSi2 with a lower Mo content.

[0058] Additional features of the pellicle membranes according to the present disclosure include:

[0059] Power capability ≥ 600 W. That is, the diaphragm is capable of operating at 600 W or more; and / or

[0060] The EUV transmission value in a single shot is 90% or higher.

[0061] The BDE threshold is defined here as any value greater than Si-N, Si-C, and Si-Si bonds.

[0062] Experiments have shown that the metal content of the embedded core crystals is important for the emissivity. For a MoSiψ diaphragm with sufficient emissivity, the MoSi crystal composition can be [Si] / [Mo]=0.6 for Mo5Si3, or [Si] / [Mo]=0.3 for other Mo-rich phases Mo3Si that can be used. If the composition of the Mo phase is [Si] / [Mo] = 2.0 for MoSi2, the film thickness is preferably greater than about 20 nm (for low Mo concentrations, the film needs to be thicker). The matrix material of the composite should include sufficient Si, which is obtained at the expense of incorporating Si in the core crystals. However, preferably, the matrix should not include only Si, such as for MoSiSi type composites.

[0063] In relation to the bond dissociation energy (BDE) of the element ψ with Si and the migration and continuous outgassing of Si atoms, if the Si-ψ BDE is strong enough, Si migration is inhibited and outgassing can only occur temporarily until the outer region of the pellicle is depleted of Si. Excess Si is able to migrate through the membrane and can be released at the outer region of the membrane in a number of processes represented by said Si outgassing, such as SiO2 desorption or SiH4 formation. The MoSiψ concept with possible low levels of outgassing as described herein therefore exhibits a higher Si-ψ bond energy, so that bond dissociation is limited and in this case, atoms of Si are transported through the Siψ 2-x Migration of the substrate and outgassing are also limited. For composite films not based on silicides, the requirements for the minimum value of BDE are different.

[0064] Here, at most 1.1·10 per 10,000 scanner chips 15 at.cm -2 As an example specification for the acceptable amount of HIO, the value of outgassing Si atoms requires at most 0.55·10 per 10,000 scanner wafers for each pellicle side. 15 at.cm -2 of the exhausted Si atoms.

[0065] Among the key parameters determining whether volatile species pose a risk of degrading the optical performance of the EUV mirror are firstly the probability of adhesion of those species to the surface of the EUV mirror and secondly whether said species oxidize on the surface of the mirror.

[0066] With the BDE value being the minimum, the Si-C bond is considered to have the highest BDE value for the three composite film types of MoSiC, MoSiSi and MoSiN, all of which exhibit outgassing of Si, which is assumed here to be associated with atomic migration. Therefore, the BDE value of the atomic bond is preferably larger to reduce bond breaking events and thus attenuate the ensuing atomic migration. The present invention claims that for any improvement, the BDE must exceed the "SiC+1 eV" value. EUV transmittance is generally highest for silicides, followed by carbides, followed by borides, followed by nitrides, followed by oxides, followed by fluorides, followed by sulfides, followed by "other bonds" such as BCl-O, HCN, HC-CH and CO.

[0067] The emitting crystal can be, for example, one or more of the following materials: metal carbides (such as Mo2C), metal borides (such as ZrB2, MoB2), metal silicides (such as ZrSi2, MoSi2, YSi2, LaSi2, ScSi2, NbSi2, RuSi2) or metals (such as Mo, Ru, Sc).

[0068] Such an emitting crystal may be combined with a matrix material which (if so desired) may provide pre-stress and strength depending on the desired pre-stress and EUV transmission, such as nitrides, oxides, fluorides or sulfides.

[0069] Materials of high interest as the core of the pellicle include Y2O3, ZrO2, HfO2 and especially C3N4, all of which have ultimate tensile strength (UTS) values ​​comparable to Si. The latter C3N4 has a very high UTS value. "Other bonds" may include BCl-O, HCN, HC-CH and CO; such bonds may be very suitable for termination or passivation of the pellicle surface because these bonds have very high BDE values.

[0070] According to the present invention, by providing metal silicide crystals in a sulfur-containing matrix, it is possible to maintain EUV transmittance higher than an equivalent pellicle membrane while reducing silicon outgassing. In particular, the molybdenum silicon sulfide pellicle membrane includes molybdenum silicide crystals located in a silicon sulfide matrix. Strong silicon-sulfur bonds have higher bond dissociation energies than silicon-nitrogen or silicon-silicon bonds, so when the pellicle membrane is irradiated with EUV light, the bond dissociation is less likely, resulting in silicon migration and outgassing. Sulfur is not strongly associated with contamination of optical devices within the lithographic equipment, and therefore there is no significant contamination problem in the case where some sulfur is outgassed. In addition, compared to a silicon matrix alone, silicon sulfide has a relatively small amount of silicon that can be incorporated into the molybdenum silicide crystal, which allows the formation of a more Mo-rich crystal, which is believed to provide a higher emissivity. In fact, preferably, the composition of the molybdenum phase is richer in molybdenum than the stoichiometric value. In other words, the ratio of Si:Mo should be less than 2.0. This allows the pellicle membrane to be thinner than the case where the molybdenum phase is composed of MoSi2.

[0071] The present invention may allow for an uncovered diaphragm membrane due to the reduced tendency of silicon to outgas.

[0072] The pellicle membrane according to the present disclosure can be manufactured via sputtering. Sputtering a target of molybdenum silicide and a target of silicon sulfide results in a pellicle membrane having metal-rich molybdenum silicide crystals in a silicon sulfide matrix. Similarly, reactive sputtering of molybdenum disilicide in a hydrogen sulfide atmosphere produces the pellicle membrane of the present disclosure. By providing sulfur in the matrix, the bond formed with silicon is strong and silicon outgassing can only be observed until the outer region of the pellicle membrane is depleted of silicon that is easily outgassable. It is considered that silicon migration is inhibited by the strong bond formed with sulfur.

[0073] Thus, the present disclosure provides a pellicle membrane having similar or better transmittance than other pellicle membranes but with a lower amount of silicon outgassing and acceptable EUV transmittance and acceptable emissivity, which allows the pellicle membrane to operate within a lithographic apparatus, particularly an EUV apparatus.

[0074] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.

[0075] The above description is intended to be illustrative rather than limiting. It will therefore be apparent to those skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set forth hereinafter.

Claims

1. A pellicle membrane comprising an emitting crystal in a matrix, the matrix comprising a silicon-containing emitting crystal having a thermal conductivity of at least 447 kJ mol -1 Or at least one element that chemically bonds with a bond dissociation energy of at least 4.6 eV.

2. The diaphragm membrane according to claim 1, wherein: The matrix comprises silicon, preferably silicon sulfide, silicon oxide, silicon selenide or silicon fluoride.

3. The pellicle diaphragm according to claim 1 or claim 2, wherein: The emitting crystal comprises one or more of the following: metal carbide, metal boride, metal nitride, metal fluoride, metal silicide, or metal, optionally wherein, The metal is selected from one or more of the following: molybdenum, zirconium, yttrium, lanthanum, scandium, niobium, iridium, chromium, vanadium, platinum, rhodium, hafnium and ruthenium.

4. The diaphragm membrane according to claim 3, wherein: The crystal includes one or a combination of Mo5Si3 and Mo3Si.

5. The pellicle diaphragm according to claim 3 or claim 4, wherein: The crystal includes MoSi 2-x Molybdenum silicide having a composition of , wherein 0 ≤ x < 2.

6. A diaphragm membrane according to any preceding claim, wherein: The substrate has SiS 2-y , where 0≤ y < 2.

7. A diaphragm membrane according to any preceding claim, wherein: The pellicle membrane at least partially has the molecular formula Mo a Si b S c , where 0 < a ≤ 30, 50 ≤ b ≤ 90 and 0 < c ≤ 50 (in mol %).

8. The diaphragm membrane according to claim 7, wherein: 10 ≤ a ≤ 30 (in mol%).

9. The pellicle membrane according to claim 7 or claim 8, wherein: 60 ≤ b ≤ 70 (in mol%).

10. The diaphragm membrane according to any one of claims 7 to 9, wherein: 20 ≤ c ≤ 30 (in mol %).

11. A diaphragm membrane according to any preceding claim, wherein: The diaphragm membrane includes silicon and molybdenum, and the ratio of Si:Mo (in mol%) deviates from 2.

0.

12. A diaphragm membrane according to any preceding claim, wherein: The pellicle membrane has an EUV transmittance of 90% or more in a single pass.

13. A diaphragm membrane according to any preceding claim, wherein: The thickness of the pellicle membrane is about 10 nm to about 100 nm, preferably wherein: The thickness of the pellicle membrane is 18 nm or less, or 15 nm or less.

14. A diaphragm membrane according to any preceding claim, wherein: The diaphragm is composed of molybdenum silicide crystals in a silicon sulfide, silicon oxide, silicon selenide or silicon fluoride matrix.

15. A method for manufacturing a diaphragm according to any one of claims 1 to 14, wherein: The method comprises sputtering, preferably co-sputtering.

16. A pellicle assembly comprising the pellicle membrane according to any one of claims 1 to 14.

17. A lithographic apparatus comprising a pellicle membrane according to any one of claims 1 to 14 or a pellicle assembly according to claim 16.

18. Use of molybdenum silicon sulfide, molybdenum silicon oxide, molybdenum silicon selenide, or molybdenum silicon fluoride in a diaphragm membrane.

19. Use of molybdenum silicon sulfide in a diaphragm membrane according to claim 18, wherein: The pellicle membrane at least partially has the molecular formula Mo a Si b S c , where 0 < a ≤ 30, 50 ≤ b ≤ 90 and 0 < c ≤ 50 (in mol %).

20. Use of a pellicle membrane according to any one of claims 1 to 14, a pellicle assembly according to claim 16, or a lithographic apparatus according to claim 17 in a lithographic apparatus or method.

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