Pellicle for EUV lithography

Abstract

To solve one of problems accompanying pellicles produced according to known methods and known techniques for producing pellicles.SOLUTION: A mask includes at least one scribe line that overlaps at least part of the opposite side where at least one layer is substantially absent. A method for preparing a pellicle is provided, which includes the steps of providing a wafer that includes a mask and at least one layer on the opposite side of one surface, defining a scribe line on the mask, and selectively removing part of at least one layer that at least partially overlaps the scribe line. Furthermore, a method for preparing a pellicle is provided, which includes the steps of providing a pellicle core and removing at least a portion of the material from at least one surface of the pellicle core in a non-oxidizing environment. In any of the embodiments, the pellicle may include a metal nitride layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] (Cross - reference to related applications)

[0001] This application claims the priority of EP application No. 18170855.3 filed on May 4, 2018, which is incorporated herein by reference in its entirety.

[0002]

[0002] The present invention relates to a wafer, a method for preparing a wafer, a pellicle for a lithography apparatus including the wafer, a method for preparing the pellicle, and a lithography apparatus including the pellicle.

Background Art

[0003]

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

[0004]

[0004] The wavelength of the radiation used by a lithography apparatus to project a pattern onto a substrate determines the minimum size of the features that can be formed on that substrate. When using a lithography apparatus that uses EUV radiation, which is electromagnetic radiation having a wavelength within 4 - 20 nm, smaller features can be formed on the substrate than with conventional lithography apparatuses (e.g., those that can use electromagnetic radiation with a wavelength of 193 nm).

[0005]

[0005] A lithography apparatus includes a patterning device (e.g., a mask or reticle). The radiation passes through or reflects off the patterning device to form an image on the substrate. A pellicle can be provided to protect the patterning device from airborne particles or other forms of contamination. Contamination on the surface of the patterning device can cause manufacturing defects on the substrate.

[0006]

[0006] The pellicle can also be provided to protect optical components other than patterning devices. Furthermore, the pellicle can be used to provide a passage for lithography radiation between regions of a lithography apparatus that are sealed to each other. The pellicle can also be used as a filter, such as a spectral purity filter.

[0007]

[0007] Known pellicles may include freestanding membranes such as silicon films, silicon nitride, graphene or graphene derivatives, carbon nanotubes, or other film materials. A mask assembly may include a pellicle that protects a patterning device (e.g., a mask) from particle contamination. A pellicle assembly can be formed by supporting the pellicle with a pellicle frame. The pellicle may be attached to the frame, for example, by gluing the pellicle boundary region to the frame. The frame can be permanently or detachably attached to the patterning device.

[0008]

[0008] During use, the temperature of the pellicle in the lithography apparatus rises to any or more between approximately 500°C and 1000°C. Such high temperatures can damage the pellicle. Therefore, it is desirable to improve the heat dissipation method in order to reduce the operating temperature of the pellicle and improve the pellicle life.

[0009]

[0009] One method to achieve this is to apply a thin metal film (coating layer), such as a ruthenium film, to the pellicle. The metal film increases the emissivity of the pellicle, thereby increasing the rate of heat release from the pellicle, and lowering the equilibrium temperature at which the heat release rate and heat absorption rate of the pellicle are equal. The metal layer is provided on the surface of the core of the pellicle, which is, for example, a silicon wafer.

[0010]

[0010] Since the pellicle is located in the optical path of the EUV radiation beam, it is necessary that the pellicle be as particle-free as possible. This is because the presence of particles can cause imaging defects on the wafer and also create hot spots on the pellicle, ultimately leading to premature failure of the pellicle. Existing methods for preparing pellicles, including the core and coating layers, generate a relatively large number of particles, which can contaminate the surface of the pellicle.

[0011]

[0011] Therefore, it is desirable to provide a method for producing a pellicle that produces a pellicle with less particle contamination compared to a pellicle produced using existing techniques, and a pellicle produced according to such a method.

[0012]

[0012] Furthermore, the pellicle must be sufficiently elastic to withstand the harsh environment inside the lithography apparatus, but since it is located in the optical path of the EUV radiation, it is desirable to reduce the amount of EUV radiation absorbed by the pellicle. This is because the amount of EUV radiation affects the number of wafers that can be imaged in a given time period.

[0013]

[0013] Therefore, it is desirable to provide a pellicle that has improved EUV transmittance, exhibits good performance, and can be manufactured with high reliability.

[0014]

[0014] Although this application generally refers to pellicles in the context of lithography apparatus, and particularly in the context of EUV lithography apparatus, it will be acknowledged that the present invention is not limited to pellicles and lithography apparatus, and that the subject matter of the present invention can be used in any other suitable apparatus or environment.

[0015]

[0015] For example, the method of the present invention can also be equally applied to spectral purity filters. Practical EUV sources, such as those that generate EUV radiation using plasma, emit not only desired "in-band" EUV radiation but also undesirable (out-of-band) radiation. The most prominent of this out-of-band radiation is in the deep UV (DUV) radiation range (100-400 nm). Furthermore, in the case of some EUV sources, such as laser-generated plasma EUV sources, the radiation emitted from a laser of typically 10.6 microns produces significant out-of-band radiation.

[0016]

[0016] In lithography equipment, spectral purity is desired for several reasons. One reason is that since resists are sensitive to out-of-band wavelength radiation, exposure of the resist to such out-of-band radiation can degrade the image quality of the pattern applied to the resist. Furthermore, out-of-band infrared radiation, such as 10.6 micron radiation in some laser-generated plasma sources, can cause undesirable and unnecessary heating of the patterning devices, substrates, and optics within the lithography equipment. Such heating can damage these elements, shorten their lifespan, and / or cause defects or distortions in the pattern projected and applied to the resist-coated substrate.

[0017]

[0017] Typical spectral purity filters can be formed from a silicon base structure (e.g., a silicon grid, or other member with an aperture) coated with a reflective metal such as molybdenum. During use, typical spectral purity filters may be subjected to high thermal loads from, for example, incident infrared and EUV radiation. High thermal loads can cause the temperature of the spectral purity filter to exceed 800°C. Under high thermal loads, the coating may peel off due to the difference in the coefficient of thermal expansion between the reflective molybdenum coating and the underlying silicon support structure. Peeling and degradation of the silicon base structure are accelerated by the presence of hydrogen. Hydrogen is often used as a gas in environments where spectral purity filters are used to suppress debris (e.g., particle debris) entering and leaving specific parts of the lithography apparatus. Thus, spectral purity filters can be used as pellicles, and vice versa. Therefore, references to “pellicle” in this application also refer to “spectral purity filters.” Although this application primarily refers to pellicles, all features are equally applicable to spectral purity filters.

[0018]

[0018] In a lithography apparatus (and / or method), it is desirable to minimize the intensity loss of radiation used to apply a pattern to a resist-coated substrate. One reason for this is that, for example, in order to shorten the exposure time and increase throughput, it is ideal to be able to utilize as much radiation as possible when applying a pattern to the substrate. At the same time, it is desirable to minimize the amount of undesirable radiation (e.g., out-of-band) that passes through the lithography apparatus and enters the substrate. Furthermore, it is desirable that the spectral purity filter used in the lithography method or apparatus has a suitable lifespan, and that the spectral purity filter is not exposed to high thermal loads and / or hydrogen (H) to which it may be exposed. * and HO *It is desirable to ensure that the spectral purity filter does not rapidly degrade over time as a result of free radical species (including ). Therefore, it is desirable to provide an improved (or alternative) spectral purity filter, for example, a spectral purity filter suitable for use in lithography apparatus and / or methods.

[0019]

[0019] Furthermore, although this application generally refers to silicon pellicles, it should be acknowledged that any suitable pellicle material may be used. For example, the pellicle may include any suitable carbon-based material, including graphene. [Overview of the Initiative]

[0020]

[0020] The present invention has been made in consideration of the aforementioned problems associated with pellicles manufactured according to known methods and techniques for manufacturing pellicles.

[0021]

[0021] According to a first aspect of the present invention, a wafer is provided comprising a mask on one face and at least one layer on the opposite face. The mask includes at least one scribe line that overlaps at least a portion of the opposite face where at least one layer is substantially absent.

[0022]

[0022] Some pellicles are manufactured by depositing one or more layers of material onto the surface of a silicon wafer. The portion of the wafer is then selectively removed to obtain the final pellicle. The silicon wafer used is circular, which is a common shape for silicon wafers due to the silicon wafer manufacturing method. Due to the constraints of wafer processing equipment, it is desirable to maintain the circular shape for as long as possible to facilitate wafer handling. However, pellicles are generally not circular and therefore need to be shaped to remove excess material. This has traditionally been done by etching grooves, also called scribe lines, into the silicon wafer. Scrib lines define the edge or periphery of the pellicle and act as weak points from which the pellicle can be removed from the rest of the wafer. For practical reasons, scribe lines are formed in the same step as etching the silicon wafer from below the material on the wafer surface to form a "window" through which EUV radiation passes during use of the pellicle in a lithography apparatus. Scrib lines can be formed on the mask and / or wafer.

[0023]

[0023] With current techniques, the etching process does not etch through the material deposited on the wafer surface, so it is unavoidable that the material deposited on the wafer surface bridges over the scribe lines. This bridged material is cut in a process known as "dicing". When the excess material is removed from the material that ultimately forms the pellicle, the bridged material is destroyed, resulting in particle contamination. These particles remain on the surface of the pellicle and can degrade the performance of the pellicle. Attempts have been made to overcome this problem by destroying the bridged material in the presence of a vacuum to suck in the generated particles. Attempts have also been made to overcome this problem by protecting the film on the wafer surface with a cap. However, both of these attempts have been found to be unsuccessful.

[0024] The term "overlie" is understood to assume that the wafer is in a generally horizontal configuration, the mask is on the bottom surface of the wafer, and at least one layer is on the top surface of the wafer. The important feature is that the scribe line and a portion of the opposite surface where at least one layer is substantially absent overlap each other, such that lines substantially parallel to the wafer surface pass through the scribe line and the portion where at least one layer is substantially absent. For this reason, preferably, at least one layer does not extend over the entire wafer surface. Also, it will be appreciated that the scribe line may be inclined with respect to the wafer surface, i.e., the scribe line may not be perpendicular to the wafer surface. In this case, "overlie" is understood to mean that the portion of the mask and at least one layer that has been removed or is otherwise not present is positioned such that it is connected by the scribe line. For this reason, when the scribe line is etched through the wafer, the scribe line connects two portions where the mask and at least one layer are substantially absent.

[0025]

[0025] The wafer preferably contains silicon.

[0026]

[0026] Silicon is a material that is well - characterized and clearly defined in the field of lithography and is thus preferably used. Also, silicon exhibits good EUV transmittance and can withstand the conditions within a lithography apparatus. However, it will be appreciated that other suitable materials can also be used and that the invention according to the first aspect of the present invention is not limited to just silicon. Other suitable materials are those known to be used in pellicles.

[0027]

[0027] The mask can include a positive or negative resist. Positive and negative resists are well - known terms in the field of lithography, and any suitable resist can be used.

[0028]

[0028] When the mask includes a negative resist, the resist becomes less soluble in the developer when exposed to radiation. Therefore, the pattern of the resist corresponds to the material for forming the pellicle without being removed from the wafer. Thus, in the present invention, it is preferable that the mask includes a negative resist.

[0029]

[0029] The mask functions to define which parts of the wafer are to be left and which parts are to be removed in subsequent processing steps. The mask includes at least one scribe line that depicts the outer perimeter of the pellicle that can ultimately be produced from the wafer. Therefore, when using a negative resist, there is substantially no resist in the scribe line in order to enable the removal of the material under the scribe line by etching. In one embodiment, the mask protects a frame of the wafer material that supports the material layer initially deposited on one surface of the wafer, i.e., the material for forming the pellicle itself.

[0030]

[0030] At least one layer can include one or more of a film, a sacrificial layer, and a pellicle layer.

[0031]

[0031] Some pellicles are simple silicon pellicles, but it has been found that the performance of the pellicle can be improved by providing one or more materials on the surface of silicon, or depositing a material on silicon and then removing the underlying silicon to leave only the deposited material on the surface of the silicon wafer to form a portion of the pellicle through which EUV radiation passes.

[0032]

[0032] The pellicle layer can include at least one of a metal layer, an oxide layer, a nitride layer, a silicide layer, a metalloid layer, and a non-metal layer. The pellicle layer can include any suitable material that is chemically and / or thermally stable under the operating conditions in the lithographic apparatus and enables EUV transmission.

[0033]

[0033] Suitable metal layers may include molybdenum, zirconium, and / or ruthenium. Oxide layers may include silicon dioxide or metal oxides. Nitride layers may include silicon nitride, silicon oxynitride, carbon nitride, boron nitride, or the like. Silicide layers may include metal silicides such as molybdenum silicide, ruthenium silicide, or zirconium silicide. Nonmetallic layers may include any suitable form of carbon, preferably graphene.

[0034]

[0034] Surprisingly, it has been found that a metal nitride layer can offer several advantages to the final pellicle. The metal nitride layer may include titanium nitride and / or tantalum nitride. The metal nitride layer can be of any suitable thickness. It is desirable that the pellicle meet other physical requirements suitable for use in lithography machines, preferably such as EUV lithography machines, while maximizing transmittance to radiation used in lithography, such as EUV radiation. For this reason, it is preferable to make the pellicle as thin as possible while maintaining the necessary physical characteristics required of the pellicle. The metal nitride layer can be as thick as about 0.1 nm to about 6 nm. Preferably, the metal nitride layer is less than about 1 nm thick. The metal nitride can function as a seed layer. For this reason, the metal nitride can function as a layer on which another layer, sometimes called a capping layer, is provided. The capping layer may include any suitable material, including ruthenium, molybdenum, boron, zirconium, and combinations thereof. The capping layer may preferably contain ruthenium. Surprisingly, the metal nitride layer increases the emissivity of the pellicle, so it has been found that the same or better emission rates can be obtained with the same or even thinner metal layer thickness as conventional pellicles. Also, surprisingly, the metal nitride layer has been found to reduce or prevent dewetting of the superimposed metal layer, such as ruthenium. This allows the pellicle to receive greater power while maintaining its integrity. Thermal stability is also increased, which enhances the pellicle's power capability. Another advantage is the reduction in the number of pinholes in the pellicle layer and the increased proportion of the pellicle surface covered by the metal layer. This reduces the variation in pellicle transmittance over time with use by preventing oxidation of the underlying material. To enable consistent wafer imaging, it is desirable to avoid changes in pellicle transmittance with use. Furthermore, the metal nitride layer can act as a barrier that slows down or prevents the formation of metal silicides resulting from the reaction between silicon and the metal layer.Metal nitrides enable the pellicle to operate reliably at higher power and / or higher temperatures by increasing the temperature at which silicon reacts with the metal in the metal layer to form metal silicide. The metal nitride layer can be provided by any suitable method known in the art. For example, metal nitrides can be provided by atomic layer deposition or chemical vapor deposition.

[0035]

[0035] By making the pellicle layer sufficiently strong, the pellicle can be formed without a silicon support layer. Therefore, when in use, EUV radiation only needs to pass through the pellicle layer and does not need to pass through the silicon layer.

[0036]

[0036] The sacrificial layer should be a layer that can be easily removed from the wafer without damaging the wafer. Preferably, the sacrificial layer is removed from the wafer before the wafer is used as a pellicle.

[0037]

[0037] The wafer may further include a protective layer.

[0038]

[0038] The protective layer preferably covers at least one layer (i.e., one or more layers of material deposited on one surface of the wafer core). The protective layer acts as a barrier to prevent damage to at least one layer and also acts as support for at least one layer if the wafer is removed by etching from below. Without the protective layer, at least one layer may be damaged, and / or if at least one layer is not strong enough to support the weight of the silicon wafer, the wafer may break along the scribe line.

[0039]

[0039] The protective layer may include at least one of polymer, resist, and lacquer. It will be acknowledged that any suitable protective layer may be used.

[0040]

[0040] Preferably, the protective layer contains poly(p-xylylene)(parylene). It will be acknowledged that any suitable polymer can be used. A polymer is suitable if it is nonreactive to at least one layer on the wafer and can be removed from the wafer without causing damage. For example, the protective layer can be dissolved in a solvent that does not dissolve the other materials forming the wafer, or react with a reactant that does not react with any of the other materials forming the wafer, or reacts with a reactant that reacts very slowly.

[0041]

[0041] A method for preparing a pellicle is provided according to a second aspect of the present invention. This method includes the steps of: providing a wafer having a mask on one face and at least one layer on the opposite face; defining scribe lines in the mask; and selectively removing a portion of at least one layer that at least partially overlaps the scribe lines.

[0042]

[0042] Due to limitations in known methods for generating pellicles, there has been no suitable pellicle preparation method that does not generate particle contamination that may unnecessarily accumulate on the pellicle surface. A method according to a second aspect of the present invention makes it possible to generate a pellicle while minimizing particle generation. By selectively removing at least a portion of at least one layer that at least partially overlaps the scribe line, the wafer can be etched away without at least one layer spanning over the scribe line. As a result, there is no need to dic or cut the material that spans over the scribe line, and thus particle generation is reduced.

[0043]

[0043] The mask can be a positive or negative type resist, and the scribe lines can be defined on the resist using any suitable lithography technique. Thus, the scribe lines can be formed on the mask using lithography.

[0044]

[0044] At least a portion of at least one layer can be removed by any suitable technique. Preferably, the technique used is etching, more preferably dry etching, but wet etching, or a combination of dry etching and wet etching, is also conceivable.

[0045]

[0045] The method may further include providing a protective layer on at least a portion of at least one layer.

[0046]

[0046] Similar to the first aspect of the present invention, the protective layer functions to support the wafer and can prevent the wafer from being damaged during etching. The protective layer can also protect at least one layer on the wafer that may be damaged by etching.

[0047]

[0047] At least a portion of the protective layer can be removed so that excess wafer material can be removed from the pellicle. The protective layer may be removed substantially from the entire wafer, or it may be removed substantially along the scribe line so that the pellicle can be removed from the excess material while leaving the protective and support layers on the pellicle.

[0048]

[0048] At least one layer may include any of the materials described in relation to the first aspect of the present invention. For this reason, the pellicle may include a metal nitride layer. A metal layer can be deposited on top of the metal nitride layer.

[0049]

[0049] The protective layer may include any of the materials described in relation to the first aspect of the present invention.

[0050]

[0050] A third aspect of the present invention provides a method for preparing a pellicle. This method includes the steps of providing a pellicle core and removing at least some material from at least one face of the pellicle core in a non-oxidizing environment.

[0051]

[0051] It is desirable to provide a pellicle that provides high EUV transmittance while maintaining the ability to withstand the harsh conditions in a lithography apparatus. Current EUV pellicles are extremely thin (less than about 100 nm) self-supporting films suspended from a frame. Existing pellicles include a silicon core, and additional layers include silicon nitride and molybdenum and / or ruthenium. The additional layers function to extend the life of the pellicle, but at the cost of a decrease in EUV transmittance and an increase in imaging impact, mainly due to EUV reflection. Efforts have been made to fabricate pellicles as robustly as possible to ensure that failure does not occur. However, fabricating extremely complex pellicles is costly, and in order to enable high throughput of lithography apparatuses, it is necessary to reduce the impact of the pellicle on imaging and increase the EUV transmittance. References to pellicles can be considered to include references to wafers. For this reason, pellicles produced by the method according to the third aspect of the present invention can be wafers according to the first and second aspects of the present invention.

[0052]

[0052] It has been found that the native oxide layer that forms between the pellicle core and the capping layer is one of the causes of EUV transmission loss. Efforts have been made to reduce the thickness of this layer, but have not yet been successful, and it has not been shown that the native oxide can be eliminated.

[0053]

[0053] In a method according to a third aspect of the present invention, the native oxide layer is removed when the pellicle core is in a non-oxidizing environment such as a vacuum, in order to avoid the regrowth of the native oxide layer. The non-oxidizing environment may be one in which substantially no oxygen is present. This may include a noble gas or an unreactive gas such as nitrogen, or it may include hydrogen. These gases are preferably at low pressure.

[0054]

[0054] The method may include the removal of at least a portion of the native oxide layer. Alternatively, the method may include thinning the pellicle core material, either in addition to this.

[0055]

[0055] By removing the native oxide layer, the EUV transmittance of the pellicle is increased, and the uniformity of the surface on which the capping layer is subsequently deposited is improved, so that the layer formation of one or more capping layers becomes more uniform. Furthermore, thinning the pellicle core has the same advantages and, in addition, further reduces the overall thickness of the final pellicle.

[0056]

[0056] The method may also include depositing a capping layer on at least one surface of the pellicle.

[0057]

[0057] The capping layer may be any of the materials described in relation to the first aspect of the present invention, or any other suitable capping material. A metal nitride layer as described herein may be provided before the deposition of the capping layer. As described above, the presence of a metal nitride layer can provide numerous advantages to the final pellicle.

[0058]

[0058] One or more capping layers can improve the performance of the pellicle. For example, the capping layer can lower the operating temperature of the pellicle by increasing the heat dissipation rate from the pellicle.

[0059]

[0059] The material can be removed from the pellicle by any suitable means. Preferably, the material is removed by etching. The etching may be dry etching, wet etching, or a combination of the two. Dry etching may include sputtering of the silicon oxide layer. For example, a beam of noble gas ions can be directed onto this layer to remove an undesirable silicon oxide layer from the surface. The pellicle core can be thinned by continuing the sputtering. Alternatively or in addition to this, as is known in the art, C x F y Etching can also be performed using an etching gas, such as a gas or similar substance.

[0060]

[0060] To prevent oxidation or other contamination, the capping layer is deposited under vacuum. This reduces the risk of contaminants being trapped between the pellicle core and the capping layer, which would weaken the final pellicle. For this reason, it is preferable to carry out the etching and deposition processes without removing the pellicle from the non-oxidizing environment. By keeping the pellicle in a non-oxidizing environment, the regrowth of the oxide layer on the surface of the pellicle core is avoided.

[0061]

[0061] According to a fourth aspect of the present invention, a pellicle for a lithography apparatus is provided, comprising a silicon core and one or more capping layers. The pellicle is substantially free of an oxide layer between the silicon core and the one or more capping layers.

[0062]

[0062] By eliminating the native oxide layer from the pellicle, the transmittance is increased and a pellicle with improved uniformity of one or more capping layers is obtained. This provides a more predictable and reproducible pellicle. The oxide layer to be removed is preferably silicon oxide.

[0063]

[0063] A pellicle according to a fourth aspect of the present invention may include any of the materials described in relation to the first aspect of the present invention.

[0064]

[0064] For this reason, a pellicle according to a fourth aspect of the present invention may include a metal nitride layer. The metal nitride layer may include ruthenium, molybdenum, boron, zirconium, titanium, tantalum, or a combination thereof. Preferably, the metal nitride layer includes at least one of titanium nitride and tantalum nitride.

[0065]

[0065] According to a fifth aspect of the present invention, a pellicle for a lithography apparatus manufactured from or including a wafer according to a first or fourth aspect of the present invention is provided, or a pellicle according to a second, third or seventh aspect of the present invention.

[0066]

[0066] According to a sixth aspect of the present invention, a lithography apparatus is provided that uses a pellicle according to any of the first to fifth aspects and seventh aspects of the present invention.

[0067]

[0067] According to a seventh aspect of the present invention, a pellicle comprising at least one metal nitride layer is provided.

[0068]

[0068] As described above, the presence of a metal nitride layer offers numerous advantages compared to a pellicle that does not contain such a layer.

[0069]

[0069] At least one metal nitride layer may include ruthenium, molybdenum, boron, zirconium, titanium, tantalum, or a combination thereof. Preferably, at least one metal nitride layer includes titanium nitride or tantalum nitride.

[0070]

[0070] At least one metal nitride layer may have any suitable thickness. At least one metal nitride layer may be thick from about 0.1 nm to about 6 nm. Preferably, at least one metal nitride layer is less than about 1.5 nm thick. In other pellicles, for example, a metal layer of molybdenum may be provided beneath the capping layer. The metal nitride layer may partially or entirely replace this molybdenum layer. Due to the advantageous properties provided by the metal nitride layer, the metal nitride layer can be thinner than a layer placed in an equivalent position in other pellicles. Furthermore, if the metal nitride layer oxidizes during use, the oxide layer that is generated is much thinner than the oxide layer produced by the oxidation of the original layer which is thicker than the metal nitride layer. This reduces the change in pellicle transmittance over time, which is desirable. For example, if a metal layer such as a molybdenum layer is replaced with a metal nitride layer such as titanium nitride, which is thinner than the molybdenum layer, the transmittance of the resulting pellicle will increase, the change in EUV transmittance observed during use will be smaller, and the pellicle will be able to withstand higher power or temperature.

[0071]

[0071] The pellicle may include a metal capping layer deposited on at least one metal nitride layer. The metal capping layer may contain ruthenium, molybdenum, boron, zirconium, titanium, tantalum, or a combination thereof. Preferably, the metal capping layer contains ruthenium.

[0072]

[0072] The metal capping layer can have any appropriate thickness. The metal capping layer may have a thickness of about 0.1 nm to about 6 nm.

[0073]

[0073] The pellicle may include one or more other layers known in the art. The pellicle may include a frame that supports the pellicle film.

[0074]

[0074] The first to seventh aspects of the present invention may be combined in any combination, and features described in relation to one aspect may be combined with features described in relation to another aspect of the present invention. For example, a wafer produced according to the method of the third aspect of the present invention may be used in a method according to the second aspect of the present invention. Similarly, a wafer according to the first aspect of the present invention may include a wafer formed according to the third aspect of the present invention. That is, in a wafer according to the first aspect of the present invention, there may be substantially no native oxide layer between the wafer and at least one layer that can be a capping layer. In one example, any method or apparatus of any aspect of the present invention may include a step of providing a metal nitride layer or may have a metal nitride layer. Furthermore, advantages related to features described in relation to one aspect of the present invention are applicable to other aspects of the present invention.

[0075]

[0075] In summary, the method of the present invention enables the manufacture of pellicles having more predictable and reproducible performance than previous pellicles. The resulting pellicles are suitable for use in lithography equipment, such as EUV lithography equipment, which was previously impossible to manufacture. Pellicles manufactured according to the method of the present invention can withstand the high temperatures achieved during use of the pellicle and can withstand attack by free radical species or other reactive species due to the coating material layers on each side of the pellicle. Furthermore, in embodiments in which the method includes providing a metal nitride layer or in which the pellicle includes a metal nitride layer, the final pellicle benefits from the advantages of having the layers described herein.

[0076]

[0076] The present invention will now be described with reference to silicon-based pellicles. However, it will be acknowledged that the present invention is not limited to silicon-based pellicles and is equally applicable to spectral purity filters and core materials other than silicon. [Brief explanation of the drawing]

[0077]

[0077] Embodiments of the present invention will be described below as merely illustrative examples with reference to the attached schematic diagrams.

[0078] [Figure 1] A lithography system including a lithography apparatus and radiation source according to one embodiment of the present invention is shown. [Figure 2] A schematic diagram of a conventional pellicle is shown. [Figure 3a] Pellicles and methods according to the first and second aspects of the present invention are shown. [Figure 3b] Pellicles and methods according to the first and second aspects of the present invention are shown. [Figure 3c] Pellicles and methods according to the first and second aspects of the present invention are shown. [Figure 3d] Pellicles and methods according to the first and second aspects of the present invention are shown. [Figure 4] This shows a conventional method for covering the pellicle core. [Figure 5a] Pellicles and methods according to third and fourth aspects of the present invention are shown. [Figure 5b] Pellicles and methods according to third and fourth aspects of the present invention are shown. [Modes for carrying out the invention]

[0079]

[0078] Figure 1 shows a lithography system including a pellicle 15 manufactured according to a method of a second, fourth, fifth, and seventh aspect of the present invention or according to a method of a first or third aspect of the present invention, according to one embodiment of the present invention. The lithography system includes 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 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. The illumination system IL is configured to adjust the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project the radiation beam (which is patterned by the mask MA at this point) onto the substrate W. The substrate W may contain a previously formed pattern. If so, the lithography apparatus aligns the patterned radiation beam B with the previously formed pattern on the substrate W. In this embodiment, the pellicle 15 is positioned within the radiation path and protects the patterning device MA. It will be acknowledged that the pellicle 15 can be placed at any required location and can be used to protect any of the mirrors in the lithography apparatus.

[0080]

[0079] The radiation source SO, the illumination system IL, and the projection system PS can all be constructed and positioned to 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 well below atmospheric pressure may be provided in the illumination system IL and / or the projection system PS.

[0081]

[0080] The radiation source SO shown in Figure 1 is of a type sometimes called a laser-generated plasma (LPP) source. The laser, which can be a CO2 laser for example, is arranged to deposit energy onto a fuel such as tin (Sn) supplied from a fuel ejector via the laser beam. In the following description, tin will be mentioned, but any suitable fuel may be used. The fuel can be, for example, in liquid form, or, for example, a metal or alloy. The fuel ejector may include a nozzle configured to guide tin, for example, in the form of droplets, along a trajectory toward the plasma-forming region. The laser beam is incident on the tin in the plasma-forming region. The deposition of laser energy onto the tin generates plasma in the plasma-forming region. During the de-excitation and recombination of plasma ions, radiation including EUV radiation is emitted from the plasma.

[0082]

[0081] EUV radiation is collected and focused by a near-normal incident radiation collector (sometimes more commonly called a normal incident 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 with two elliptical foci. The first focal point may be in the plasma-forming region, and the second focal point may be an intermediate focal point. This will be discussed below.

[0083]

[0082] The laser may be separated from the radiation source SO. If this is the case, the laser beam can be delivered from the laser to the radiation source SO by a beam delivery system (not shown) including, for example, a suitable guide mirror and / or beam expander and / or other optical systems. The laser and the radiation source SO can together be considered as a radiation system.

[0084]

[0083] The radiation reflected by the collector forms a radiation beam B. The radiation beam B is focused at a certain point to form an image of the plasma-forming region, which acts as a virtual radiation source for the illumination system IL. The point at which the radiation beam B is focused can be called the intermediate focus. The radiation source SO is positioned such that the intermediate focus is located at or near the aperture of the closed structure of the radiation source.

[0085]

[0084] The radiation beam B travels from the radiation source SO into an illumination system IL configured to adjust the radiation beam. The illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. Both the faceted field mirror device 10 and the faceted pupil mirror device 11 give the radiation beam B a desired cross-sectional shape and a desired angular distribution. The radiation beam B exits the illumination system IL and is incident on a patterning device MA held by a support structure MT. The patterning device MA reflects the radiation beam B and imparts a pattern. The illumination system IL may also include other mirrors or devices in addition to or instead of the faceted field mirror device 10 and the faceted pupil mirror device 11.

[0086]

[0085] After being reflected from the patterning device MA, the patterned radiation beam B is incident on the projection system PS. The projection system comprises several mirrors 13, 14 configured to project the radiation beam B onto a substrate W held by a substrate table WT. The projection system PS can form an image of a feature smaller than the corresponding feature on the patterning device MA by applying a reduction factor to the radiation beam. For example, a reduction factor of 4 can be applied. In Figure 1, the projection system PS has two mirrors 13, 14, but the projection system can include any number of mirrors (e.g., six mirrors).

[0087]

[0086] The radiation source SO shown in Figure 1 may include components not shown. For example, a spectral filter may be provided within the radiation source. The spectral filter may be substantially transparent to EUV radiation but substantially block radiation of other wavelengths, such as infrared radiation.

[0088]

[0087] Figure 2a shows a schematic cross-section of a pellicle produced according to a prior art method. In this figure, the silicon support has already been removed by etching, leaving a boundary 18 separated by the scribe line 16 and the remaining wafer portion 19. The capping layer 17 spans over the scribe line 16. Therefore, in order to separate the boundary 18 from the remaining wafer portion 19, it is necessary to destroy or cut the capping layer 17 that spans over the scribe line 16, which may generate undesirable particles that can contaminate the capping layer 17.

[0089]

[0088] Figure 2b shows a schematic plan view of the pellicle shown in Figure 2a. The boundary 18 is shown as a dashed line (phantom line) inside the scribe line 16. The scribe line 16 is not visible because of the presence of the capping layer 17, but it can be seen that it is shown for clarity. The boundary 18 of the silicon wafer acts as a frame around the capping layer 17 to support the capping layer 17 when used as a pellicle.

[0090]

[0089] Figure 3a shows a wafer according to the present invention, comprising a wafer 23, a capping layer (at least one layer) 17, scribe lines 16, and a mask 20. The capping layer 17 is continuous on the surface of the wafer 23, and the mask 20 on the opposite side of the wafer 23 defines the scribe lines 16. The capping layer 17 may include a metal nitride layer (not shown). The capping layer 17 may include a metal layer and a metal nitride layer disposed between this metal layer and the wafer 23. As described above, the presence of a metal nitride layer has been shown to have a surprising number of advantages.

[0091]

[0090] Figure 3b shows the wafer after a portion 27 of the capping layer 17 that overlapped the scribe line 16 has been removed. Arrow 21 shows how at least a portion of the gap 27 in the capping layer 17 overlaps at least a portion of the scribe line 16.

[0092]

[0091] In Figure 3c, a protective layer 22 is applied to the wafer, and the wafer 23 is removed by etching in areas not protected by the mask 20. The etching process does not remove the protective layer 22. Importantly, there is no capping layer 17 that spans over the scribe lines 16.

[0093]

[0092] As shown in Figure 3c, the protective layer 22 may have a projection 28 that extends into the gap 27.

[0094]

[0093] In Figure 3d, the protective layer 22 has been removed, and any excess material has been removed to reach the pellicle. The remaining material on the wafer 23 serves as a frame to support the capping layer 17 when used as a pellicle. It should be acknowledged that these figures are not drawn to scale and are used simply to show the various layers of the pellicle, not to indicate dimensions.

[0095]

[0094] Figure 4 shows a schematic diagram of a pellicle according to the prior art. The core material includes a wafer 23 core covered with a native oxide layer 24. When a capping layer 25 is deposited on the wafer, the native oxide layer 24 is located between the core 23 and the capping layer 25.

[0096]

[0095] Figure 5a shows the same wafer as shown in Figure 4, but the native oxide layer is removed from wafer 23 in a non-oxidizing atmosphere or vacuum 26. Subsequently, a capping layer is deposited on the core in a non-oxidizing atmosphere or vacuum 26, resulting in a pellicle that does not contain the native oxide layer. Once the native oxide layer has been removed, a metal nitride layer (not shown) can be provided on the core layer. A metal capping layer can then be provided on the metal nitride layer. The metal nitride layer and the metal layer may contain any of the metals described in relation to any aspect of the present invention.

[0097]

[0096] Figure 5b is similar to Figure 5a, but the native oxide layer 24 is removed and the wafer 23 is thinned, resulting in an example where a pellicle that is thinner and has better transmittance than the existing pellicle is obtained. After the native oxide layer is removed and / or after the pellicle core is thinned, the capping layer 25 is deposited. In this case as well, once the native oxide layer is removed and / or the pellicle core is thinned, a metal nitride layer can be provided. In this way, a metal nitride layer can be provided between the wafer 23 and the capping layer 25. Removing the native oxide layer and a portion of the pellicle core, and then depositing the capping layer, is performed in a non-oxidizing environment.

[0098]

[0097] Embodiments of the present invention may also be described as expressed in the following clauses. 1. A wafer comprising a mask on one face and at least one layer on the opposite face, wherein the mask comprises at least one scribe line overlapping at least a portion of the opposite face where at least one layer is substantially absent. 2. The wafer is a wafer containing silicon, as described in Clause 1. 3. The wafer as described in Clause 1 or 2, the mask includes a positive or negative type resist. 4. A wafer according to any one of the clauses 1 to 3, wherein at least one layer comprises one or more of the following: a film, a sacrificial layer, and a pellicle layer. 5. The wafer according to Clause 4, wherein the pellicle layer comprises at least one of a metal layer, an oxide layer, a nitride layer, a silicide layer, a metalloid layer, a nonmetallic layer, and a metal nitride layer, and optionally the metal layer and / or metal nitride layer comprises ruthenium, molybdenum, boron, zirconium, titanium, tantalum, or a combination thereof. 6. The wafer is a wafer as described in any of clauses 1 to 5, further comprising a protective layer. 7. The wafer according to Clause 6, wherein the protective layer is located on top of at least one other layer, and at least one other layer is located between the protective layer and the mask. 8. The wafer according to Clause 7, wherein the protective layer has projections extending into gaps formed in at least one layer at a location where at least one layer is substantially absent on a portion of the opposite face. 9. The wafer according to any one of clauses 6 to 8, wherein the protective layer comprises at least one of a polymer, a resist, and a lacquer, and preferably the polymer is poly(p-xylylene). 10. An assembly comprising a wafer, a mask provided on one face of the wafer, and at least one layer provided on the opposite face of the wafer, wherein the mask includes at least one scribe line overlapping at least a portion of the opposite face where at least one layer is substantially absent. 11. The wafer is an assembly containing silicon, as described in Clause 10. 12. The assembly described in Clause 10 or 11, the mask comprising a positive or negative type resist. 13. An assembly according to any one of the clauses 10 to 12, wherein at least one layer comprises one or more of the following: a film, a sacrificial layer, and a pellicle layer. 14. The assembly according to Clause 13, wherein the pellicle layer comprises at least one of a metal layer, an oxide layer, a nitride layer, a silicide layer, a metalloid layer, a nonmetallic layer, and a metal nitride layer, and optionally the metal layer and / or metal nitride layer comprises ruthenium, molybdenum, boron, zirconium, titanium, tantalum, or a combination thereof. 15. The assembly further includes a protective layer, as described in any of clauses 10 to 14. 16. The assembly described in Clause 15, wherein at least one layer is placed between the protective layer and the wafer. 17. The assembly according to Clause 16, wherein the protective layer has projections extending into gaps formed in at least one layer on a portion of the opposite surface where at least one layer is substantially absent. 18. The assembly according to any one of clauses 10 to 18, wherein the protective layer comprises at least one of a polymer, a resist, and a lacquer, and preferably the polymer is poly(p-xylylene). 19. A method for preparing a pellicle, comprising the steps of: providing a wafer having a mask on one face and at least one layer on the opposite face; defining scribe lines in the mask; and selectively removing a portion of at least one layer that at least partially overlaps the scribe lines. 20. The method according to clause 19, further comprising providing a protective layer on at least a portion of at least one layer. 21. The method according to Clause 19, further comprising providing a protective layer on at least a portion of at least one layer, wherein at least a portion of at least one layer is positioned between the protective layer and the mask. 22. The method according to clause 20 or 21, wherein the protective layer is provided with projections extending into gaps formed by selectively removed portions of at least one layer. 23. The method according to any one of the clauses 19 to 22, further comprising etching at least a portion of the wafer. 24. The method according to Clause 23, further comprising removing at least a portion of the protective layer. 25. The scribe lines and / or masks are defined by lithography, as described in any of Clauses 19 to 24. 26. The method according to any one of the clauses 19 to 25, wherein at least one layer comprises one or more of the following: a film, a sacrificial layer, and a pellicle layer. 27. Etching is dry etching, wet etching, or a combination of the two, as described in any of the methods in Clauses 23 to 26. 28. The protective layer comprises at least one of a polymer, a resist, and a lacquer, as described in any of clauses 19 to 27. 29. The protective layer comprises poly(p-xylylene) as described in Clause 28. 30. A method for preparing a pellicle, comprising the steps of providing a pellicle core and removing at least a portion of the material from at least one face of the pellicle core in a non-oxidizing environment. 31. The method according to Clause 30, further comprising depositing a capping layer on at least one surface of a pellicle, wherein the capping layer optionally comprises a metal nitride layer and / or a metal layer. 32. The material is removed by etching, as described in clause 30 or 31. 33. Etching is dry etching, wet etching, or a combination of the two, as described in Clause 32. 34. The method according to clause 32 or 33, wherein etching is performed by guiding a beam of noble gas ions onto the surface of the pellicle core. 35. The capping layer is deposited under vacuum, according to any of the methods described in clauses 31 to 34. 36. The non-oxidizing environment is a vacuum, as described in any of the methods in clauses 30 to 35. 37. A pellicle for a lithography apparatus comprising a silicon core and one or more capping layers, wherein the pellicle substantially lacks an oxide layer between the silicon core and the one or more capping layers. 38. A pellicle for a lithography apparatus manufactured from or including a wafer as described in any of Clauses 1 to 9 or an assembly as described in any of Clauses 10 to 18 or Clause 37, or as described in the methods of Clauses 19 to 36. 39. Use in a lithography apparatus of a pellicle manufactured in accordance with the methods of Clauses 19 to 36, or of a pellicle as described in any of Clauses 1 to 18 or Clause 37. 40. A pellicle for a lithography apparatus, comprising at least one metal nitride layer. 41. The pellicle according to Clause 40, wherein at least one metal nitride layer comprises at least one of titanium nitride and tantalum nitride.

[0099]

[0098] Although specific embodiments of the present invention have been described above, it will be understood that the present invention can be practiced in ways other than those described. The above description is illustrative and not limiting. Therefore, it will be obvious to those skilled in the art that the present invention can be modified as described without departing from the claims set out below.

Claims

1. A film comprising a seed layer which is a metal nitride layer, and a capping layer which is a metal layer disposed on the seed layer, The boundary supporting the aforementioned film, A self-supporting membrane containing this membrane.

2. The self-supporting film according to claim 1, wherein the seed layer comprises ruthenium, molybdenum, boron, zirconium, titanium, tantalum, or a combination thereof.

3. The self-supporting membrane according to claim 1 or 2, wherein the membrane is used as a pellicle or as a filter such as a spectral purity filter.

4. The self-supporting film according to claim 1, wherein the seed layer has a thickness of 0.1 nm to 6 nm, preferably less than 1.5 nm.

5. The self-supporting film according to claim 1, wherein the capping layer comprises a material selected from ruthenium, molybdenum, boron, zirconium, and combinations thereof.

6. The self-supporting film according to claim 1 or 2, further comprising one or more other layers.

7. The self-supporting film according to claim 6, wherein the one or more other layers are one or more of a core, a sacrificial layer, a protective layer, and a pellicle layer.

8. The self-supporting film according to claim 7, wherein the pellicle layer comprises at least one of a metal layer, an oxide layer, a nitride layer, a silicide layer, a metalloid layer, a nonmetallic layer, and a metal nitride layer.

9. The self-supporting film according to claim 8, wherein the silicide layer includes a metal silicide.

10. The self-supporting film according to claim 9, wherein the metal silicide comprises molybdenum silicide, ruthenium silicide, or zirconium silicide.

11. A pellicle or spectral purity filter comprising a self-supporting membrane according to any one of claims 1 to 10.

12. A pellicle assembly comprising a self-supporting membrane according to any one of claims 1 to 10, further comprising a frame attached to the boundary.

13. An apparatus comprising a self-supporting membrane according to any one of claims 1 to 10.

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