TW202414076A - Manufacturing method of pellicle for euv photomask - Google Patents

Abstract

In a method of manufacturing a pellicle for an extreme ultraviolet (EUV) photomask, a nanotube layer including a plurality of carbon nanotubes is formed, the nanotube layer is attached to a pellicle frame, and a Joule hearting treatment is performed to the nanotube layer by applying electric current through the nanotube layer.

Description

Photomask pellicle for extreme ultraviolet lithography mask and manufacturing method thereof

without

A pellicle is a thin transparent film that extends over a frame that is glued to one side of the reticle to protect it from damage, dust, and/or moisture. In extreme ultraviolet (EUV) lithography, a pellicle with high transparency in the EUV wavelength region, high mechanical strength, and low or no contamination is often required. EUV transmissive films have also been used in EUV lithography equipment to replace pellicles.

without

It will be understood that the following disclosure provides many different embodiments or examples for implementing different features of the present disclosure. Specific embodiments or examples of components and configurations are described below to simplify the present disclosure. Of course, these are merely examples and are not intended to be limiting. For example, the size of the elements is not limited to the disclosed ranges or values, but may depend on the process conditions and/or desired properties of the device. In addition, the formation of a first feature above or on a second feature in the following description may include embodiments in which the first feature and the second feature are formed in direct contact, and may also include embodiments in which additional features interposing the first feature and the second feature may be formed so that the first feature and the second feature may not be in direct contact. The various features may be arbitrarily depicted in different proportions for simplicity and clarity. In the accompanying drawings, some layers/features may be omitted for simplicity.

Furthermore, spatially relative terms such as "below," "below," "down," "above," "upper," etc., may be used herein for convenience of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than the orientation depicted in the figures. The device may be oriented in other ways (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein may be interpreted accordingly. Additionally, the term "made of" may mean "comprising" or "consisting of." Furthermore, in the following manufacturing processes, there may be one or more additional operations in between the described operations, and the order of the operations may be changed. In the present disclosure, the term "at least one of A, B, and C" means any one of A, B, C, A+B, A+C, B+C, or A+B+C, and does not mean one from A, one from B, and one from C, unless otherwise explained. Materials, configurations, structures, operations, and/or dimensions explained with one embodiment may be applied to other embodiments, and a detailed description thereof may be omitted.

EUV lithography is one of the key technologies for extending Moore's Law. However, due to the wavelength scaling from 193 nm (ArF) to 13.5 nm, EUV sources suffer from strong power degradation due to environmental absorption. Although stepper/scanner chambers are operated under vacuum to prevent strong EUV absorption by gases, maintaining high EUV transmittance from the EUV source to the wafer is still an important factor in EUV lithography.

Mask pellicles usually require high transparency and low reflectivity. In ultraviolet (UV) or deep ultraviolet (DUV) lithography, mask pellicles are made of transparent resin films. However, in EUV lithography, resin-based films are not acceptable, and non-organic materials such as polysilicon, silicide or metal films are used.

Carbon nanotubes (CNTs) are one of the materials suitable for pellicles used for EUV reflective masks because CNTs have a high EUV transmittance of more than 96.5%. Generally, pellicles used for EUV reflective masks require the following properties: (1) long life in the hydrogen-rich radical operating environment in the EUV stepper/scanner; (2) strong mechanical strength to minimize droop effects during vacuum pumping and exhaust operations; (3) high or ideal blocking properties for particles larger than about 20 nanometers (inhibitor particles); and (4) good heat dissipation to prevent the pellicle from being burned by EUV radiation. Other nanotubes made of non-carbon-based materials can also be used for pellicles used for EUV masks. In some embodiments of the present disclosure, nanotubes are one-dimensional elongated tubes having a diameter in a range from about 0.5 nanometers to about 100 nanometers.

In the present disclosure, a mask pellicle for EUV mask includes a mesh film having a plurality of nanotubes, the plurality of nanotubes forming a mesh structure. In addition, a method for treating the mesh film to remove contaminants and increase mechanical strength is also disclosed.

FIG. 1A and FIG. 1B illustrate an EUV pellicle 10 according to one embodiment of the present disclosure. In some embodiments, the pellicle 10 for EUV reflective mask includes a main mesh film 100 disposed on and attached to a pellicle frame 15. In some embodiments, as shown in FIG. 1A , the main mesh film 100 includes a plurality of single-walled nanotubes 100S, and in other embodiments, as shown in FIG. 1B , the main mesh film 100 includes a plurality of multi-walled nanotubes 100D. In some embodiments, the single-walled nanotubes are carbon nanotubes. In some embodiments, some single-walled nanotubes are closely attached to each other to form a bundle of nanotubes.

In some embodiments, the multi-walled nanotubes are coaxial nanotubes having two or more tubes coaxially surrounding an inner tube (multiple). In some embodiments, the main network film 100 includes only one type of nanotube (single-walled/multi-walled, or material), and in other embodiments, different types of nanotubes form the main network film 100. In some embodiments, the multi-walled nanotubes are multi-walled carbon nanotubes. In some embodiments, some multi-walled nanotubes are closely attached to each other to form a bundle of nanotubes.

In some embodiments, when mounted on the EUV mask, the mask pellicle (support) frame 15 is attached to the main mesh film 100 to maintain the space between the main mesh film of the mask pellicle and the EUV mask (pattern area). The mask pellicle frame 15 of the mask pellicle is attached to the surface of the EUV mask with a suitable bonding material. In some embodiments, the bonding material is an adhesive, such as an acrylic or silicone based glue or an A-B cross-linked type glue. The size of the frame structure is larger than the area of the black border of the EUV mask so that the mask pellicle covers not only the circuit pattern area of the mask but also the black border.

2A, 2B, 2C, and 2D illustrate various views of multi-walled nanotubes according to embodiments of the present disclosure.

In some embodiments, the nanotubes in the main network film 100 include multi-walled nanotubes, which are also called coaxial nanotubes. FIG. 2A shows a perspective view of a multi-walled coaxial nanotube having three tubes 210, 220, and 230 and FIG. 2B shows a cross-sectional view thereof. In some embodiments, tube 210 (inner tube 210) and tube 220 (outer tube 220) and tube 230 (outer tube 230) are carbon nanotubes. In other embodiments, the inner tube and one or more of the two outer tubes are non-carbon-based nanotubes, such as boron nitride nanotubes.

The number of tubes of the multi-walled nanotube is not limited to three. In some embodiments, the multi-walled nanotube has two coaxial nanotubes as shown in FIG. 2C, and in other embodiments, the multi-walled nanotube includes tube 210 (innermost tube 210) and first to Nth nanotubes including outermost tube 200N, where N is a natural number from 1 to 20, as shown in FIG. 2D. In some embodiments, N is at most 10 or at most 5. In some embodiments, at least one of the first to Nth outer layers is a nanotube coaxially surrounding tube 210 (innermost nanotube 210). In some embodiments, all of the innermost tube 210 and the first to Nth outer layers are carbon nanotubes. In other embodiments, one or more of the tubes are non-carbon-based nanotubes.

In some embodiments, the diameter of the innermost nanotube is in a range from about 0.5 nm to about 20 nm, and in other embodiments, in a range from about 1 nm to about 10 nm. In some embodiments, the diameter of the multi-walled nanotube (i.e., the diameter of the outermost tube) is in a range from about 3 nm to about 40 nm, and in other embodiments, in a range from about 5 nm to about 20 nm. In some embodiments, the length of the multi-walled nanotube is in a range from about 0.5 microns to about 50 microns, and in other embodiments, in a range from about 1.0 microns to about 20 microns.

3A, 3B and 3C illustrate the fabrication of a nanotube network film for a mask pellicle according to an embodiment of the present disclosure.

In some embodiments, the carbon nanotubes are formed by a chemical vapor deposition (CVD) process. In some embodiments, the CVD process is performed by using a vertical furnace as shown in FIG. 3A, and the synthesized nanotubes are deposited on a support film 80 as shown in FIG. 3B. In some embodiments, the carbon nanotubes are formed by a carbon source gas (precursor) using a suitable catalyst such as iron (Fe) or nickel (Ni). Then, the main mesh film 100 formed on the support film 80 is separated from the support film 80 and transferred to the photomask pellicle frame 15 as shown in FIG. 3C. In some embodiments, the platform or base on which the supporting film 80 is disposed is rotated continuously or intermittently (in a stepwise manner) so that the synthesized nanotubes are deposited on the supporting film 80 in different or random directions.

Figure 3D shows a manufacturing process of the network film and Figure 3E shows a flow chart thereof according to one embodiment of the present disclosure.

In some embodiments, carbon nanotubes are dispersed in a solution as shown in FIG. 3D. The solution includes a solvent such as water or an organic solvent, and a surfactant such as sodium dodecyl sulfate (SDS). The nanotubes are one type or two or more types of nanotubes (material and/or number of walls). In some embodiments, carbon nanotubes are formed by various methods such as arc discharge, laser ablation, or chemical vapor deposition (CVD) methods.

As shown in FIG. 3D, the support film 80 is placed between the chamber or cylinder in which the nanotube dispersion is placed and the vacuum chamber. In some embodiments, the support film 80 is an organic or inorganic porous or mesh material. In some embodiments, the support film 80 is a woven or non-woven fabric. In some embodiments, the support film 80 has a circular shape in which a 150 mm x 150 mm square photomask film size (the size of an EUV mask) can be placed.

As shown in FIG. 3D , the pressure in the vacuum chamber is reduced so that pressure is applied to the solvent in the chamber or cylinder. Because the mesh or pore size of the supporting film 80 is sufficiently smaller than the size of the nanotubes, the nanotubes are captured by the supporting film 80 and the solvent passes through the supporting film 80. The supporting film 80 on which the nanotubes are deposited is removed from the filtering apparatus of FIG. 3D and then dried. In some embodiments, the deposition by filtration is repeated to obtain the desired thickness of the nanotube network layer as shown in FIG. 3E . In some embodiments, after the nanotubes in the solution are deposited, other nanotubes are dispersed in the same or new solution and the filtration deposition is repeated. In other embodiments, after the nanotubes are dried, another filtration precipitation is performed. Repeatedly, the same type of nanotubes are used in some embodiments, and different types of nanotubes are used in other embodiments. In some embodiments, the nanotubes dispersed in the solution include multi-walled nanotubes.

FIGS. 4A and 4B to FIGS. 6A and 6B illustrate cross-sectional views (“A” views) and plan (top) views (“B” views) of various stages of manufacturing a pellicle for an EUV mask according to one embodiment of the present disclosure. It should be understood that additional operations may be provided before, during, and after the process illustrated by FIGS. 4A to 6B, and that some of the operations described below may be replaced or eliminated for additional embodiments of the method. The order of operations/processes may be interchangeable. Materials, configurations, methods, processes, and/or dimensions as explained with respect to the previous embodiments are applicable to the following embodiments, and detailed descriptions thereof may be omitted.

As shown in FIG. 4A and FIG. 4B , a nanotube layer 90 is formed on a supporting film 80 by one or more methods as explained above. In some embodiments, the nanotube layer 90 includes single-walled nanotubes, multi-layer nanotubes, or a mixture thereof. In some embodiments, the nanotube layer 90 includes only single-walled nanotubes. In some embodiments, the nanotubes are carbon nanotubes.

Then, as shown in FIGS. 5A and 5B , the pellicle frame 15 is attached to the nanotube layer 90. In some embodiments, the pellicle frame 15 is formed of one or more layers of crystalline silicon, polysilicon, silicon dioxide, silicon nitride, ceramic, metal, or organic material. In some embodiments, as shown in FIG. 5B , the pellicle frame 15 has a rectangular (including square) frame shape that is larger than the black border region of the EUV mask and smaller than the substrate of the EUV mask.

Next, in some embodiments, as shown in FIGS. 6A and 6B , the nanotube layer 90 and the supporting film 80 are cut into a rectangular shape having the same size as or slightly larger than the pellicle frame 15, and then the supporting film 80 is detached or removed. When the supporting film 80 is made of an organic material, the supporting film 80 is removed by wet etching using an organic solvent.

In some embodiments of the present disclosure, a pellicle film including a plurality of carbon nanotubes is subjected to a thermal (annealing) treatment to remove contaminants such as residual catalyst (e.g., iron catalyst) used to form the nanotubes and used to form a plurality of bundles of nanotubes in which the nanotubes are closely attached to each other.

FIGS. 7A and 7B are flow charts illustrating a process according to an embodiment of the present disclosure. It should be understood that additional operations may be provided before, during, and after the process shown in FIGS. 7A and 7B, and that some of the operations described below may be replaced or eliminated for additional embodiments of the method. The order of operations/processes may be interchangeable.

In the process of FIG. 7A, nanotubes are formed as in the process described above, and a thin film is formed by the nanotubes. Then, as described, a photomask pellicle frame is attached to the thin film. Subsequently, a heat treatment is performed on the thin film. In the process shown in FIG. 7B, the thin film is subjected to a heat treatment before the photomask pellicle frame is attached to the thin film.

In some embodiments, the heat treatment includes a Joule heating treatment using a Joule heating apparatus as described below, wherein an electric current is applied through the film to generate heat.

Figures 8A, 8B, 8C, and 8D show various views of a Joule heating apparatus and process for a pellicle or a pellicle film, and Figure 9 shows a schematic diagram of a Joule heating apparatus and process for a pellicle or a pellicle film according to an embodiment of the present disclosure. Figures 8A, 8C, and 8D are cross-sectional views and Figure 8B is a plan view (top view).

In some embodiments, as shown in FIGS. 8A and 8B, the pellicle 10 including the main mesh film 100 and the pellicle frame 15 is placed on an insulating platform or support 50 and fixed at the edge portion of the pellicle by the platform and the portion of the electrode 55. In some embodiments, the support 50 (or insulating platform 50) is made of ceramic, and the electrode 55 is made of metal such as tungsten, copper or steel. The electrode 55 is attached to contact the main mesh film 100. In some embodiments, the electrode 55 is attached to two side portions (e.g., left and right) of the main mesh film 100. In some embodiments, the length of the electrode is greater than the length of the side (photomask film frame 15) of the main mesh film 100. In some embodiments, the main mesh film 100 is supported horizontally. In some embodiments, the electrode 55 is connected to a current source (power supply) 58 via a wire.

In other embodiments, as shown in FIG. 8C , when the film 100 of the mask pellicle frame 15 is heated, the Joule heating device fixes the film at the edge portion, and the electrode 55 contacts the main web film 100. In some embodiments, as shown in FIG. 8D , the main web film 100 is fixed by two electrodes 55 and 56.

The Joule heating device with the mask film 10 or the main web film 100 mounted thereon is placed in a vacuum chamber 60 as shown in FIG. 9. In some embodiments, the vacuum chamber 60 has a bottom portion and an upper (cover) portion of the Joule heating device placed therein, and a gasket (e.g., an O-ring) is disposed between the bottom portion and the upper portion. The wires of the Joule heating device are connected to external wires, which are connected to a current source 58 (current source 58).

In some embodiments, during the Joule heating operation, the vacuum chamber is evacuated to a pressure equal to or less than 10 Pa. In some embodiments, the pressure is greater than 0.1 Pa. Current source 58 applies current to mask pellicle 100 so that the current flows through the film, thereby generating heat. In some embodiments, the current is direct current (DC), and in other embodiments, the current is alternating current (AC) or pulsed current.

In some embodiments, the current from the current source 58 is adjusted so that the film is heated at a temperature in the range of from about 800°C to 2000°C. In some embodiments, the lower limit of the temperature is about 1000°C, 1200°C, or 1500°C, and the upper limit is about 1500°C, 1600°C, or 1800°C. The temperature is adjusted so that the metal particles (e.g., iron as a residual catalyst) are vaporized under vacuum and evacuated. When the temperature is below these ranges, the contaminants may not be completely removed, and when the temperature is above these ranges, the film and/or frame may be damaged. In some embodiments, the mask film frame 15 is made of a ceramic or metal or a metal material having a higher resistance than the main network film 100 (carbon nanotube film 100).

In some embodiments, the Joule heating process is performed in an inert gas environment such as _N2 and/or Ar. In some embodiments, the Joule heating process is performed for about 5 seconds to about 60 minutes, and in other embodiments, for about 30 seconds to about 15 minutes. When the heating time is shorter than these ranges, the contaminants may not be completely removed, and when the heating time is longer than these ranges, the cycle time or process efficiency may be degraded.

In some embodiments, as shown in FIG. 8B , the electrode 55 contacts two sides (left and right) of the mask film 10 and current flows through the main mesh film 100 (film 100). In other embodiments, after heat treatment in the case where the electrode 55 contacts two sides (left and right), the mask film 10 or the main mesh film 100 is rotated by 90 degrees so that the electrode 55 contacts the other two sides (top and bottom) of the mask film 10 for current to flow through the main mesh film 100 in different directions. In some embodiments, a pair of additional electrodes is provided so that the top and bottom edges of the mask film 10 or the main mesh film 100 are also fixed, and the current is switched to flow between the first pair of electrodes or the second pair of additional electrodes.

In some embodiments, the Joule heating process is performed using induction heating as shown in FIG. 10. In some embodiments, one or more coils 70 are provided around (e.g., below) the mask film 10 or the main web film 100, and alternating current is provided to the coils. In some embodiments, the coils are provided outside the vacuum chamber to surround the vacuum chamber. In some embodiments, the vacuum chamber is made of glass or ceramic.

In some embodiments, as shown in FIG. 11 , the Joule heating operation causes individual separated nanotubes 100M (single-walled or multi-walled nanotubes) to bond and form a bundle 100B of nanotubes having a seamless graphite structure, wherein the nanotubes are more firmly bonded or bound than simply touching each other. In some embodiments, three or more nanotubes are connected (bonded or bound) to form a bundle of nanotubes. In some embodiments, the number of nanotubes in one bundle is at most 10.

In some embodiments, the main network film 100 formed before the Joule heating treatment includes no or a small amount of carbon nanotube bundles, and after the Joule heating treatment, the number of carbon nanotube bundles increases.

In some embodiments, the main network film 100 formed before the Joule heating treatment includes an Sp ³ carbon structure, such as amorphous carbon. As shown in FIG. 12 , the Joule heating treatment removes amorphous carbon from the film and/or converts the amorphous carbon (Sp ³ carbon structure) into an Sp ² carbon structure. In some embodiments, the amorphous carbon is graphitized to form a crystalline structure. In some embodiments, the crystallized amorphous carbon forms one or more outer tubes surrounding an inner carbon nanotube having a single-walled or multi-walled structure to form a multi-walled nanotube. In some embodiments, the content of amorphous carbon in the film formed before the Joule heating is in the range of from about 1 wt % to about 50 wt %, and the content of amorphous carbon in the film after the Joule heating is less than about 3 wt %. In some embodiments, the content of amorphous carbon in the film after Joule heating is in the range of from about 0.5 wt% to about 2.5 wt%. In some embodiments, all of the ^Sp3 carbon structure is removed or converted, and thus the film after Joule heating treatment does not show a peak at the D band (1360 cm ^-1 ) in the Raman spectrum. In other embodiments, a portion of the ^Sp3 carbon structure is retained, and a peak at the D band is observed.

13A to 13E illustrate schematic diagrams of catalyst removal and beam formation by Joule heating according to an embodiment of the present disclosure.

As explained above, the main mesh film 100 (with or without the pellicle frame 15) may include residual catalyst or catalyst particles 89 therein, as shown in FIG. 13A. The Joule heating process may remove a portion (see FIG. 13B) or all (see FIG. 13C) of the residual catalyst from the film. In addition, the separated nanotubes shown in FIG. 13A may be converted into bundles of nanotubes as shown in FIG. 13D and FIG. 13E by the Joule heating process. In some embodiments, the content of residual catalyst in the film formed before the Joule heating is in the range of from about 7 wt% to about 15 wt%, and the content of residual catalyst in the film after the Joule heating is less than about 2 wt%. In some embodiments, the residual catalyst content in the film after Joule heating is in a range from about 0.1 wt % to about 1.5 wt %.

As explained above, Joule heating treatment can improve the chemical and mechanical properties of the network film formed by carbon nanotubes.

FIG. 14 shows a flow chart for processing a pellicle for an EUV mask, and FIGS. 15A to 15E show schematic diagrams of processing a pellicle according to an embodiment of the present disclosure. It should be understood that additional operations may be provided before, during, and after the processes shown in FIGS. 14 and 15A to 15E, and that some of the operations described below may be replaced or eliminated for additional embodiments of the method. The order of operations/processes may be interchangeable.

In some embodiments, the Joule heating process is performed after using a mask pellicle in an EUV lithography operation.

As shown in FIGS. 14 and 15A, a mask pellicle having a frame that has been subjected to a Joule heating treatment as shown in FIGS. 7A and 7B is attached to an EUV mask. The mask is then used in an EUV lithography operation subjected to EUV radiation. During the EUV lithography operation, contaminants or particles 92 may land on the mask pellicle, as shown in FIG. 15B. In some embodiments, the contaminants or particles include particles of molybdenum (Mo), silicon carbide (SiC), titanium nitride (TiN), tantalum (Ta), iron (Fe), nickel (Ni), etc. As shown in FIG. 15C, after performing a predetermined number of EUV exposure operations, the mask pellicle is detached from the mask, as shown in FIG. 15D, and the mask pellicle is subjected to a Joule heating treatment as described above to remove contaminants and particles. In some embodiments, one or more defects in the carbon nanotube film caused by EUV radiation are removed or reduced by graphitization during the Joule heating process. In some embodiments, additional wet cleaning or dry cleaning is performed before or after the Joule heating process. The mask pellicle is then mounted again on the EUV mask, as shown in FIG. 15E, and the mask is used in an EUV lithography operation, as shown in FIG. 15F.

In some embodiments, the network film includes ^Sp2 carbon structures, such as graphite or graphene instead of or in addition to carbon nanotubes.

In some embodiments, the photomask pellicle of the present embodiment further comprises one or more capping layers. After the initial Joule heating treatment is performed, the capping layer(s) are attached to the film.

In some embodiments, as shown in FIG. 16A, a first cover plate (or layer) 520 is formed at the bottom surface of the main mesh film 100 between the pellicle frame 15 and the main mesh film 100. In some embodiments, a second cover plate 530 is formed on the main mesh film 100 to seal the mesh film with the first cover plate 520. In some embodiments, as shown in FIG. 16C, the first cover plate is not used, and only the second cover plate 530 is used. In some embodiments, as shown in FIG. 16D, a third cover plate 540 covers the entire structure of FIG. 16B (or FIG. 16A or FIG. 16C). In some embodiments, as shown in FIG. 16E, the first cover plate and/or the second cover plate are not used. In some embodiments, the material of the third cover plate 540 of FIG. 16E is the same as the material of the first cover plate and/or the second cover plate.

In some embodiments, one or both of the first cover plate 520 and the second cover plate 530 include a two-dimensional material in which one or more two-dimensional layers are stacked. Here, in some embodiments, a "two-dimensional" layer refers to one or a few crystalline layers of an atomic matrix or network having a thickness in the range of about 0.1 nanometers to 5 nanometers. In some embodiments, the two-dimensional materials of the first cover plate 520 and the second cover plate 530 are the same or different from each other. In some embodiments, the first cover plate 520 includes a first two-dimensional material and the second cover plate 530 includes a second two-dimensional material.

In some embodiments, the two-dimensional material used for the first cover plate 520 and/or the second cover plate 530 includes boron nitride (BN), graphene, and/or transition metal dichalcogenide (TMD) represented by MX ₂ , where M=Mo, W, Pd, Pt, and/or Hf, and X=S, Se and/or Te. In some embodiments, TMD is one of MoS ₂ , MoSe ₂ , WS ₂ , or WSe ₂ .

In some embodiments, the total thickness of each of the first cover plate 520 and the second cover plate 530 is in a range from about 0.3 nm to about 3 nm, and in other embodiments, in a range from about 0.5 nm to about 1.5 nm. In some embodiments, the number of two-dimensional layers of each of the two-dimensional materials of the first cover layer and/or the second cover layer is 1 to about 20, and in other embodiments, 2 to about 10. When the thickness and/or number of layers is greater than these ranges, the EUV transmittance of the mask pellicle may be reduced, and when the thickness and/or number of layers is less than these ranges, the mechanical strength of the mask pellicle may be insufficient.

In some embodiments, the third superstrate 540 includes at least one layer of an oxide such as HfO ₂ , Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , or La ₂ O _3. In some embodiments, the third superstrate 540 includes at least one layer of a non-oxidized compound such as B ₄ C, YN, Si ₃ N ₄ , BN, NbN, RuNb, YF ₃ , TiN, or ZrN. In some embodiments, the protective layer 40 includes at least one metal layer made of, for example, Ru, Nb, Y, Sc, Ni, Mo, W, Pt, or Bi. In some embodiments, the third superstrate 540 is a single layer, and in other embodiments, two or more layers of these materials are used as the third superstrate 540. In some embodiments, the thickness of the third cover layer is in a range from about 0.1 nm to about 5 nm, and in other embodiments, in a range from about 0.2 nm to about 2.0 nm. When the thickness of the third cover plate 540 is greater than these ranges, the EUV transmittance of the mask film may be reduced, and when the thickness of the third cover plate 540 is less than these ranges, the mechanical strength of the mask film may be insufficient.

In some embodiments, the thickness of the main mesh film 100 is in the range of about 5 nm to about 100 nm, and in other embodiments, in the range of about 10 nm to about 50 nm. When the thickness of the main mesh film 100 is greater than these ranges, EUV transmittance may be reduced, and when the thickness of the main mesh film 100 is less than these ranges, mechanical strength may be insufficient.

FIG. 17A illustrates a flow chart of a method for making a semiconductor device, and FIG. 17B, FIG. 17C, FIG. 17D, and FIG. 17E illustrate a sequential manufacturing method for making a semiconductor device according to an embodiment of the present disclosure. A semiconductor substrate or other suitable substrate to be patterned to form an integrated circuit thereon is provided. In some embodiments, the semiconductor substrate includes silicon. Alternatively or in addition, the semiconductor substrate includes germanium, silicon germanium, or other suitable semiconductor materials, such as Group III-V semiconductor materials. At step S801 of FIG. 17A, a target layer to be patterned is formed on the semiconductor substrate. In some embodiments, the target layer is a semiconductor substrate. In some embodiments, the target layer includes a conductive layer, such as a metal layer or a polysilicon layer; a dielectric layer, such as silicon dioxide, silicon nitride, SiON, SiOC, SiOCN, SiCN oxide, or aluminum oxide; or a semiconductor layer, such as an epitaxially formed semiconductor layer. In some embodiments, the target layer is formed on an underlying structure such as an isolation structure, a transistor, or a wiring. At step S802 of FIG. 17A, a photoresist layer is formed on the target layer, as shown in FIG. 17B. The photoresist layer is sensitive to radiation from an exposure source during a subsequent photolithography exposure process. In the present embodiment, the photoresist layer is sensitive to EUV light used in the photolithography exposure process. The photoresist layer can be formed on the target layer by spin coating or other suitable techniques. The coated photoresist layer can be further baked to drive out the solvent in the photoresist layer. At step S803 of Figure 17A, the photoresist layer is patterned using an EUV reflective mask having a photomask pellicle as described above, as shown in Figure 17C. The patterning of the photoresist layer includes performing a photolithography exposure process using an EUV mask by an EUV exposure system. During the exposure process, the integrated circuit (IC) design pattern defined on the EUV mask is imaged onto the photoresist layer to form a latent pattern thereon. The patterning of the photoresist layer further includes developing the exposed photoresist layer to form a patterned photoresist layer having one or more openings. In an embodiment where the photoresist layer is a positive tone photoresist layer, the exposed portion of the photoresist layer is removed during the development process. The patterning of the photoresist layer may further include other process steps, such as various baking steps at different stages. For example, a post-exposure-baking (PEB) process may be performed after the photolithography exposure process and before the development process.

At step S804 of FIG. 17A , the target layer TL is patterned using the patterned photoresist layer PR as an etching mask, as shown in FIG. 17D . In some embodiments, patterning the target layer TL includes applying an etching process to the target layer TL using the patterned photoresist layer PR as an etching mask. The portion of the target layer TL exposed within the opening of the patterned photoresist layer PR is etched, while the remaining portion is protected from etching. In addition, the patterned photoresist layer PR can be removed by wet stripping or plasma ashing, as shown in FIG. 17E .

In some embodiments, a network film including carbon nanotubes or other Sp2 carbon subjected to Joule heating is used in an EUV transmission window, a residue trap disposed between an EUV lithography apparatus and an EUV radiation source, or any other part in an EUV lithography apparatus and EUV radiation where high EUV transmittance is required.

In previous embodiments, the pellicle film was subjected to a Joule heating operation to remove contaminants and form bundles of carbon nanotubes. The pellicle according to embodiments of the present disclosure provides higher strength and lower contamination and higher EUV transmittance than conventional pellicles.

It will be understood that not all advantages have necessarily been discussed herein, that no particular advantage is required for all embodiments or examples, and that other embodiments or examples may provide different advantages.

According to one aspect of the present disclosure, in a method of manufacturing a pellicle for an extreme ultraviolet (EUV) mask, a nanotube layer including a plurality of carbon nanotubes is formed, the nanotube layer is attached to a pellicle frame, and a Joule heating treatment is performed on the nanotube layer by applying a current through the nanotube layer. In one or more of the previous and following embodiments, the Joule heating treatment is performed at a pressure equal to or less than 10 Pa. In one or more of the previous and following embodiments, the Joule heating treatment is performed in an inert gas environment. In one or more of the previous and following embodiments, the Joule heating treatment is performed for 5 seconds to 60 minutes. In one or more of the previous and following embodiments, a current is applied so that the nanotube layer is heated at a temperature in the range of 800°C to 2000°C. In one or more of the previous and following embodiments, the current is direct current DC. In one or more of the previous and following embodiments, the current is AC. In one or more of the previous and following embodiments, the Joule heating treatment is performed by placing the nanotube layer and the photomask pellicle frame on a support, fixing the edge of the frame with a conductive plate so that the conductive plate contacts the nanotube layer, and applying a current through the conductive plate. In one or more of the previous and following embodiments, the nanotube layer is placed in a vacuum chamber before or after fixing. In one or more of the preceding and following embodiments, the plurality of carbon nanotubes include metal contaminants, and the content of the metal contaminants in the nanotube layer after the Joule heating treatment is less than the content of the metal contaminants in the nanotube layer. In one or more of the preceding and following embodiments, the metal contaminants include a plurality of iron catalysts used in forming the plurality of carbon nanotubes. In one or more of the preceding and following embodiments, the metal contaminants include one or more of molybdenum (Mo), titanium (Ti), titanium nitride (TiN), tantalum (Ta), or nickel (Ni).

According to another aspect of the present disclosure, in a method for manufacturing a pellicle for an extreme ultraviolet (EUV) mask, a nanotube layer including a plurality of carbon nanotubes and amorphous carbon is formed, the nanotube layer is attached to a pellicle frame, and a Joule heating treatment is performed on the nanotube layer by applying a current. At least a portion of the amorphous carbon is converted into crystals by the Joule heating treatment. In one or more of the previous and following embodiments, the crystallized amorphous carbon has a graphite structure. In one or more of the previous and following embodiments, the crystallized amorphous carbon is formed on the surface of a carbon nanotube in a plurality of carbon nanotubes. In one or more of the previous and following embodiments, the crystallized amorphous carbon formed on the surface of the carbon nanotube has a multilayer structure. In one or more of the foregoing and following embodiments, at least a portion of the amorphous carbon is removed via Joule heating.

According to another aspect of the present disclosure, in a method of manufacturing a pellicle for an extreme ultraviolet (EUV) mask, a nanotube layer including a plurality of carbon nanotubes is formed, the nanotube layer is attached to a pellicle frame, and the nanotube layer is subjected to a Joule heating treatment by applying an electric current. After the Joule heating treatment, the nanotube layer includes a plurality of bundles of carbon nanotubes, in each bundle, the carbon nanotubes are connected to form a seamless graphite structure. In one or more of the previous and following embodiments, the number of the plurality of bundles of carbon nanotubes is increased due to the Joule heating treatment. In one or more of the previous and following embodiments, the carbon nanotubes of the plurality of bundles include multi-walled nanotubes. In one or more of the previous and following embodiments, the number of carbon nanotubes in one bundle is three or more.

According to another aspect of the present disclosure, in a method of extreme ultraviolet (EUV) lithography, an EUV mask pellicle is attached to an EUV mask, an EUV exposure process using the EUV mask with the EUV mask pellicle is performed, the EUV mask pellicle is detached from the EUV mask, and a Joule heating process is performed on the EUV mask pellicle by applying a current through the EUV mask pellicle. In one or more of the previous and following embodiments, the EUV mask pellicle includes a nanotube layer, the nanotube layer including a plurality of nanotubes. In one or more of the previous and following embodiments, the plurality of nanotubes include carbon nanotubes. In one or more of the previous and following embodiments, the carbon nanotubes include multi-walled nanotubes. In one or more of the previous and following embodiments, the EUV mask pellicle includes contaminants, and the content of the contaminants in the EUV mask pellicle after the Joule heating treatment is less than the content of the contaminants in the EUV mask pellicle. In one or more of the previous and following embodiments, the contaminants include one or more of Mo, SiC, Si, Ti, TiN, Ta, Fe, or Ni.

According to another aspect of the present disclosure, in a method for treating a film that transmits extreme ultraviolet (EUV), the film includes ^Sp2 carbon and a Joule heating treatment is performed on the film by applying a current through the film. In one or more of the previous and following embodiments, before the Joule heating treatment, the film is attached to a frame having an opening. In one or more of the previous and following embodiments, the frame is a photomask pellicle frame. In one or more of the previous and following embodiments, after the Joule heating treatment, the photomask pellicle frame is attached to an EUV mask. In one or more of the previous and following embodiments, the film includes at least one of carbon nanotubes, graphene, or graphite. In one or more of the previous and following embodiments, the film before the Joule heating treatment further includes ^Sp3 carbon, and at least a portion of the ^Sp3 carbon is converted into ^Sp2 carbon by the Joule heating treatment. In one or more of the preceding and following embodiments, the film includes carbon nanotubes, and after Joule heating treatment, the film includes a plurality of bundles of carbon nanotubes, in each of the plurality of bundles, the carbon nanotubes are connected to form a seamless graphite structure. In one or more of the preceding and following embodiments, before Joule heating treatment, the film includes a plurality of bundles of carbon nanotubes, and the number of the plurality of bundles of carbon nanotubes after Joule heating treatment is greater than the number of the plurality of bundles of carbon nanotubes before Joule heating treatment. In one or more of the preceding and following embodiments, the film has an EUV transmittance of 95% to 98%.

According to another aspect of the present disclosure, an EUV mask pellicle includes a web film, the web film includes a plurality of carbon nanotubes, and residual catalyst particles in an amount less than 2 wt% relative to the total weight of the web film. According to another aspect of the present disclosure, an EUV mask pellicle includes a web film, the web film includes a plurality of carbon nanotubes and amorphous carbon, and the content of amorphous carbon in the web film is less than 3 wt% relative to the total weight of the web film.

The foregoing summarizes the features of several embodiments or examples so that those skilled in the art can better understand the state of the present disclosure. Those skilled in the art will understand that they can easily use the present disclosure as a basis for designing or modifying other processes and structures to implement the same purpose and/or achieve the same advantages of the embodiments or examples introduced herein. Those skilled in the art should also recognize that such equivalent structures do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and modifications without departing from the spirit and scope of the present disclosure.

10: Photomask film 15: Photomask film frame 50: Supporting member 55, 56: Electrode 58: Current source 60: Vacuum chamber 70: Coil 80: Supporting film 89: Catalyst particles 90: Nanotube layer 92: Particles 100: Main network film 100B: Bundle of nanotubes 100S: Single-walled nanotubes 100D: Multi-walled nanotubes 100M: Nanotubes 200N: Outermost tube 210: Tube 220, 230: Tube 520: First cover plate 530: Second cover plate 540: Third cover plate S801, S802, S803, S804: Steps

The aspects of the present disclosure are better understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that various features are not drawn to scale, in accordance with standard practice in the industry. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of discussion. FIGS. 1A and 2A illustrate a pellicle for an EUV mask according to an embodiment of the present disclosure. FIGS. 2A, 2B, 2C, and 2D illustrate various views of multi-walled nanotubes according to an embodiment of the present disclosure. FIGS. 3A, 3B, and 3C illustrate a process for manufacturing a network film according to one embodiment of the present disclosure. FIG. 3D illustrates a process for manufacturing a network film, and FIG. 3E illustrates a flow chart thereof according to one embodiment of the present disclosure. Figures 4A and 4B show a cross-sectional view and a plane (top view) view of one of the various stages for manufacturing a pellicle for an EUV mask according to an embodiment of the present disclosure. Figures 5A and 5B show a cross-sectional view and a plane (top view) view of one of the various stages for manufacturing a pellicle for an EUV mask according to an embodiment of the present disclosure. Figures 6A and 6B show a cross-sectional view and a plane (top view) view of one of the various stages for manufacturing a pellicle for an EUV mask according to an embodiment of the present disclosure. Figures 7A and 7B show a flow chart for manufacturing a pellicle for an EUV mask according to an embodiment of the present disclosure. FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D illustrate various views of a Joule heating apparatus and process for a pellicle or pellicle film according to an embodiment of the present disclosure. FIG. 9 illustrates a schematic diagram of a Joule heating apparatus and process for a pellicle or pellicle film according to an embodiment of the present disclosure. FIG. 10 illustrates a schematic diagram of a Joule heating apparatus and process for a pellicle or pellicle film using induction heating according to an embodiment of the present disclosure. FIG. 11 illustrates a schematic diagram of a bundle formation of nanotubes according to an embodiment of the present disclosure. FIG. 12 illustrates a schematic diagram of the removal or transformation of amorphous carbon according to an embodiment of the present disclosure. FIG. 13A, FIG. 13B, FIG. 13C, FIG. 13D, and FIG. 13E illustrate various views of the removal of excess catalyst and the formation of nanotube bundles according to various embodiments of the present disclosure. FIG. 14 is a flow chart for processing a pellicle for an EUV mask according to various embodiments of the present disclosure. FIG. 15A, FIG. 15B, FIG. 15C, FIG. 15D, FIG. 15E, and FIG. 15F illustrate EUV lithography processes according to various embodiments of the present disclosure. FIG. 16A, FIG. 16B, FIG. 16C, FIG. 16D, and FIG. 16E illustrate diagrams of pellicles according to some embodiments of the present disclosure. FIG. 17A shows a flow chart of a method for manufacturing a semiconductor device, and FIG. 17B, FIG. 17C, FIG. 17D, and FIG. 17E show sequential manufacturing operations of a method for manufacturing a semiconductor device according to an embodiment of the present disclosure.

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

100B:Bundle of nanotubes

100M:Nanotubes

200N: Outermost tube

210: tube

Claims (20)

A method of manufacturing a pellicle for an extreme ultraviolet photomask comprises: forming a nanotube layer including a plurality of carbon nanotubes; attaching the nanotube layer to a pellicle frame; and performing a Joule heating process on the nanotube layer by applying a current through the nanotube layer. A method as described in claim 1, wherein the Joule heating treatment is performed at a pressure equal to or less than 10 Pa. The method of claim 2, wherein the Joule heating treatment is performed in an inert gas environment for 5 seconds to 60 minutes. A method as described in claim 1, wherein the current is applied so that the nanotube layer is heated to a temperature in a range from 800°C to 2000°C. A method as described in claim 4, wherein the current is direct current. A method as described in claim 4, wherein the current is alternating current. The method of claim 1, wherein the Joule heating treatment is performed by: Placing the nanotube layer and the photomask film frame on a support; Fixing the edges of the frame with a plurality of conductive plates so that the conductive plates contact the nanotube layer; and Applying the current through the conductive plates. The method of claim 7, wherein the nanotube layer is placed in a vacuum chamber before or after fixation. The method of claim 1, wherein: the carbon nanotubes include a plurality of metal contaminants, and after the Joule heating treatment, the content of one of the metal contaminants in the nanotube layer is less than the content of one of the metal contaminants in the nanotube layer before the Joule heating treatment. A method as described in claim 9, wherein the metal contaminants include a plurality of iron catalysts used in forming the carbon nanotubes. A method as described in claim 9, wherein the metal contaminants include one or more of molybdenum, titanium, titanium nitride, tantalum or nickel. A method for manufacturing a pellicle for an extreme ultraviolet light mask comprises: forming a nanotube layer including a plurality of carbon nanotubes and amorphous carbon; attaching the nanotube layer to a pellicle frame; and performing a Joule heating treatment on the nanotube layer by applying a current, wherein at least a portion of the amorphous carbon is converted into crystallized amorphous carbon by the Joule heating treatment. A method as described in claim 12, wherein the crystallized amorphous carbon has a graphite structure. The method of claim 12, wherein the crystallized amorphous carbon is formed on a surface of a carbon nanotube among the carbon nanotubes. The method of claim 14, wherein the crystallized amorphous carbon formed on the surface of the carbon nanotube has a multi-layer structure. The method of claim 12, wherein at least a portion of the amorphous carbon is removed by the Joule heating treatment. A method for manufacturing a pellicle for an extreme ultraviolet light mask, comprising: forming a nanotube layer including a plurality of carbon nanotubes; attaching the nanotube layer to a pellicle frame; and performing a Joule heating treatment on the nanotube layer by applying an electric current, wherein after the Joule heating treatment, the nanotube layer includes a plurality of bundles of the carbon nanotubes, in each of the bundles, the carbon nanotubes are connected to form a seamless graphite structure. A method as described in claim 17, wherein a number of the bundles of the carbon nanotubes is increased due to the Joule heating treatment. The method of claim 17, wherein the carbon nanotubes of the bundles include a plurality of multi-walled nanotubes. A method as described in claim 17, wherein a number of the carbon nanotubes in a bundle is three or more.

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