KR102848426B1 - Pellicle for EUV lithography and fabrication method thereof - Google Patents

Abstract

The present invention discloses a pellicle for EUV exposure that simultaneously satisfies the high transmittance and mechanical strength of crystalline silicon and enables large-area manufacturing, and a method for manufacturing the same.

Description

Pellicle for EUV lithography and fabrication method thereof

The present invention relates to a pellicle for extreme ultraviolet (EUV) exposure and a method for manufacturing the same.

To improve integration during the semiconductor pattern formation process, it is necessary to improve lithography technology to reduce the line width of the semiconductor.

Recently, major semiconductor and IT electronics companies are releasing semiconductor products with line widths of 10nm or less, and their lithography processes are shifting from the older ArF method to Extreme Ultraviolet (EUV) irradiation. While the existing ArF method struggles to form clear patterns at feature sizes below 10nm, the latest lithography processes using EUV light sources with a wavelength of 13.5nm enable applications below 10nm.

The lithography process was conducted in the existing ArF method, where the light source penetrated the existing pattern mask, but in EUV lithography, it was changed to a reflective method, and the process is also being conducted in a high vacuum atmosphere.

EUV lithography uses an EUV reticle (pattern mask or photomask), and the reticle forms a mask pattern on a high-purity quartz substrate.

The mask pattern is composed of a reflective layer and an absorbing layer, and is made by stacking 80 consecutive layers of Mo (3 nm) and Si (4 nm) layers forming a low-refractive-index layer and a high-refractive-index layer, and then stacking a capping layer/buffer layer on top of the reflective layer and finally stacking an absorbing layer.

The EUV mask (reticle) is completed by etching the buffer layer/absorber layer, including the buffer layer stacked on the capping layer that protects the Mo/Si reflective layer, according to the semiconductor pattern line width and shape.

When EUV light reaches the mask, EUV is absorbed in the absorption layer of the remaining area except for the etched pattern, and when EUV is reflected by the reflective layer that is etched according to the pattern shape, the light reflected in the shape of the pattern reaches the substrate and an image is formed.

In this method, if contaminants, dust, etc. enter the mask pattern (i.e., the reticle), pattern defects can occur. In particular, as feature sizes decrease, the need to block these contaminants and dust increases. Therefore, a film-type pellicle filter must be installed on the front of the reticle to protect it from contaminants and dust.

Although most of the development of the current EUV process has been completed, a pellicle that satisfies the transmittance suitable for mass production has not been developed. In addition to the cost of tens of millions of won per piece, this material must be developed in order to enter the mass production of ultra-high-density (3 nm or less) semiconductors in the future.

The requirements for a pellicle to be applied include a high transmittance of at least 90% for EUV light sources, sufficient mechanical strength to withstand the pressure difference generated during vacuum evacuation, the ability to withstand the high temperatures caused by irradiation from the EUV light source, and chemical stability that prevents etching by hydrogen when a large amount of hydrogen is administered.

Currently, as a result of development by various research groups including domestic ones, Si material has the highest EUV transmittance, achieving 86%. However, because the thickness must be reduced to 50 nm or less to improve transmittance, there is a problem with reduced mechanical properties.

To compensate for this, candidate materials such as SiC, SiN, and CNT were used, but most of them did not satisfy the transmittance or the required area (110x144 mm ² ).

KR Patent Publication No. 10-2015-0123145 discloses a pellicle comprising a single-layer graphene, double-layer graphene, or multi-layer graphene material, and discloses that the graphene material has high mechanical strength and can quickly dissipate high-temperature heat generated from EUV during a lithography process.

However, since these membranes are weak in strength, various support films or reinforcing films are used for reinforcement, and multilayer thin films with various structures such as mesh or porous membranes are also used.

Additionally, graphene, which is made of carbon atoms, has the characteristic of being etched in a large amount of hydrogen atmosphere, so an additional protective film is required on top of the graphene.

Materials used for supporting or reinforcing films include silicon (Si), ruthenium (Ru), iron (Ir), gold (Au), rhodium (Rh), and carbon (C), as well as inorganic films such as aluminum nitride (AlN), silicon nitride (SiN), and silicon carbide (SiC). While these materials offer the advantage of enhancing the durability of the pellicle film, their manufacturing process is complex, and some materials still have issues with EUV transmittance.

KR Publication Patent No. 10-2015-0123145 (Published on November 3, 2015) KR Publication Patent No. 10-2018-0109498 (Published on October 8, 2018)

The present applicant has conducted various studies to simplify the process conditions for manufacturing a pellicle film in which a graphene layer and a crystalline silicon (c-Si) layer are hetero-bonded, while maintaining the excellent mechanical properties of graphene and increasing EUV transmittance, while also enabling large-scale production. As a result, a new method has been developed in which, after the formation of a precursor layer for manufacturing each layer, electron beam irradiation causes the formation of a graphene layer, crystallization of silicon, and diffusion of the Si-C interface, thereby creating a stacked structure of c-Si/graphene or c-Si/SiC/graphene.

Accordingly, the purpose of the present invention is to provide a pellicle for EUV exposure and a method for manufacturing the same.

To achieve the above object, the present invention provides a pellicle for EUV (Extreme Ultraviolet) exposure, which includes a pellicle film that transmits extreme ultraviolet rays and a support frame that supports the pellicle film.

The above pellicle film has a multilayer thin film structure in which a c-Si layer and a graphene thin film are hetero-bonded.

The above c-Si is crystallized silicon without grain boundaries of the micrometer size, and is crystallized by heating a deposited amorphous silicon thin film with electron beam irradiation, and the above graphene thin film is also crystallized into a graphene thin film by irradiating a graphene precursor or carbon thin film with electron beam.

Si crystallized by electron beam irradiation shows crystallization peaks at the (111), (220), and (311) planes in the XRD (X-ray diffraction) analysis spectrum, and has a Raman shift at 520 cm ^-1 , which indicates Si crystallized by electron beam irradiation, unlike 480 cm ^-1 , which indicates amorphous silicon, in the Raman analysis.

Amorphous silicon crystallized by laser irradiation has grain boundaries several micrometers in size, but c-Si crystallized by electron beam irradiation does not show grain boundaries of micrometers in size. When there is an external force or impact, especially when there is a difference in vacuum pressure between the front and back of the pellicle, a crack that starts to break on one side will be generated, and this will propagate along the grain boundaries, causing the pellicle to be destroyed. Therefore, crystalline silicon c-Si, which does not have grain boundaries, can be used as a material with excellent properties that can increase the strength of the pellicle and enhance the transmittance of EUV.

At this time, the pellicle film may be any one of the c-Si/graphene, graphene/c-Si, c-Si/SiC/graphene, graphene/SiC/c-Si, c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene structures used as the pellicle film or as part of a variety of pellicle film stacking structure arrangements.

The above pellicle film may have a thickness of 5 to 50 nm.

In addition, the present invention provides a manufacturing method for manufacturing a pellicle for EUV (Extreme Ultraviolet) exposure, which includes a pellicle film that transmits ultraviolet rays and a support frame that supports the pellicle film.

Specifically,

(S1) A step of forming a multilayer film including a carbon layer, a metal catalyst layer, and an amorphous silicon layer on a substrate;

(S2) A step in which the amorphous silicon layer on the surface is heated by irradiating an electron beam, and as this heat diffuses downward, the amorphous silicon layer is crystallized into a c-Si layer, the carbon in the carbon layer passes through the metal catalyst layer and diffuses to the c-Si/metal catalyst layer interface, and the carbon that has risen thereafter forms graphene at the interface, all of which are performed simultaneously or sequentially to ultimately form a multilayer thin film in which the c-Si layer and the graphene layer are hetero-bonded;

(S3) A step of forming a binder layer on the outer surface of the multilayer film and also forming a binder layer on the facing surface of the support frame, and then performing diffusion bonding through the binder layer by bringing the support frame into contact with the binder layer on the outer surface of the multilayer film; and

(S4) A step including a step of lifting off a multilayer thin film attached to a frame from the substrate.

At this time, if the metal catalyst layer remains on the top layer of the multilayer thin film, the metal catalyst layer is etched to leave a multilayer thin film of c-Si/graphene on the frame _.

Additionally, after the above (S4)

(S5) A step of forming at least one of an amorphous silicon layer and a carbon layer on the bottom surface opposite the frame of the frame-attached multilayer thin film; and

(S6) A step of forming at least one of a c-Si layer and a graphene layer by irradiating an electron beam on the above-mentioned bottom surface is further performed.

Through the above steps, the present invention completes a pellicle film having an asymmetric structure of Si/graphene, graphene/c-Si, c-Si/SiC/graphene, and graphene/SiC/c-Si bonded to a frame.

Through additional steps, a pellicle film having a symmetrical structure of c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene bonded to the frame is completed.

In the present invention, the multilayer film before electron beam treatment may be one type of multilayer film selected from the group consisting of amorphous silicon layer/metal catalyst layer/carbon layer/substrate, amorphous silicon layer/carbon layer/metal catalyst layer/substrate, carbon layer/metal catalyst layer/amorphous silicon layer/substrate, carbon layer/amorphous silicon layer/metal catalyst layer/substrate, metal catalyst layer/carbon layer/amorphous silicon layer/substrate, and metal catalyst layer/amorphous silicon layer/carbon layer/substrate.

The above metal catalyst layer may be a single metal or an alloy of two or more selected from the group consisting of Ni, Ti, Al, Zn, Co, Cu, Pt, Ag, and Au having an FCC structure.

The above carbon layer is formed by coating a graphene precursor solution and then curing it to form a graphene cured film or by sputtering or vacuum deposition.

The above diffusion bonding is performed by applying a pressure of 0.1 MPa to 1.0 MPa at a temperature of 300°C to 600°C.

The binder layer for diffusion bonding is any one of a low-temperature melting metal; a eutectic alloy having a lower melting temperature when Zn, Ga, In, Sn, Au and Al, Si, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Te, Ru, Pd, Ag, and Pt are alloyed together; and a general alloy, and includes one selected from the group consisting of oxides, nitrides, carbides, and borides thereof.

The above substrate is pretreated by one or more processes including plasma implantation treatment, hydrophobic plasma treatment, or deposition of a spacing layer on a Si wafer, or by hydrophobic plasma treatment or deposition of a spacing layer on various metals, ceramics, or a quartz plate.

The lift-off is performed by separating the substrate and the multilayer thin film by heat treatment, RTA heat treatment, electron beam or laser irradiation of the back surface of the substrate after plasma implantation and deposition of the separation layer, and by ejecting hydrogen, helium, and nitrogen, oxygen, etc. from the interface with the substrate or the separation layer compound and decomposition from the separation layer compound.

Lift-off can also be performed by etching the substrate or by etching away the intermediate film between the substrate and the multilayer film, leaving the remaining multilayer film.

In the above embodiments, a SiC layer can be formed by the reaction of Si and carbon at the Si/carbon interface, and the formation and thickness of the SiC layer can be controlled by adjusting the energy irradiation time of the electron beam.

In the above implementation examples, amorphous silicon can be crystallized simultaneously with the crystallization of graphene after the formation of a multilayer thin film, but if necessary, crystallization of silicon alone can be performed immediately after silicon deposition.

In the above embodiments, the metal catalyst layer acts as a catalyst not only in crystallizing amorphous silicon but also in crystallizing the carbon layer into graphene, and this metal catalyst layer can ultimately be removed with an etchant.

In the above embodiments, a step of pretreating the substrate or depositing spacing layer thin films necessary for lift-off may be included before depositing a multilayer thin film on the substrate to lift-off the pellicle from the substrate.

In the above embodiments, by combining the sequence of deposition of a multilayer thin film, electron beam irradiation, and etching of the outermost metal catalyst layer, the multilayer thin film is made into a mirror structure, and further, by controlling the electron beam irradiation time to control the formation of a SiC layer at the Si/C interface, various multilayer thin films including SiC of c-Si/SiC/graphene, graphene/SiC/c-Si, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene can be formed.

In the above implementation examples, the heating method by electron beam irradiation may also be possible by general heat treatment, RTA heat treatment, or laser irradiation.

Additionally, the present invention provides a pellicle used to protect a reticle from dust.

Electron beams can be generated using one or more electron beam sources, the electron beam sources can be arranged in series or parallel, and a circular or linear beam can be used. Electron beam irradiation can be generated using one or more electron beam sources, the electron beam sources can be arranged in series or parallel, and a circular or linear beam can be used.

Electron beam irradiation can be performed by moving the support at a constant speed while the electron beam source is fixed, or by moving the support while the electron beam source is fixed. The electron beam irradiated to the substrate can have an applied voltage of 50 eV to 50 keV. Electron beam irradiation is performed in the presence of an inert gas, and the inert gas can be selected from nitrogen, helium, neon, argon, xenon, or a mixture of one or more thereof.

The carbon layer may use polyimide, polyacrylonitrile, polymethyl methacrylate, polystyrene, rayon, lignin, pitch, borazine oligomer, and a combination of one or more thereof as a graphene precursor. Here, the solvent used to dissolve the graphene precursor may be at least one selected from dimethylformamide (DMF), formaldehyde, chloroform, dimethylacetamide (DMA), pyridine, benzopyridine, benzene, xylene, toluene, dioxane, tetrahydrofuran (THF), diethyl ether, dimethyl sulfoxide (DMSO), and n-methyl-2-pyrrolidone (NMP).

The carbon layer can be formed by coating a graphene precursor solution and then curing it to form a graphene cured film, or by any one of chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), sputtering, graphite ion beam deposition (IBD), physical vapor deposition, and vacuum deposition. In addition, the carbon source in sputtering, graphite ion beam deposition (IBD), physical vapor deposition, and vacuum deposition can be formed by using a graphite target or pellet alone, or by a process in which hydrocarbon gas is additionally added.

The method for manufacturing a pellicle for EUV exposure according to the present invention is not only very simple in process but also enables processing of a pellicle size (140 mm × 114 mm) or larger required for the EUV process using a linear electron beam, thereby enabling the production of a pellicle with uniform characteristics.

The graphene layer and c-Si layer in the pellicle film manufactured in this way are high-quality thin films with few defects, and their properties and thickness can be easily controlled during the manufacturing process.

In particular, the present invention simultaneously forms crystalline silicon and graphene thin films using an electron beam, and has a structure in which these form continuous layers. The crystalline silicon has no grain boundaries, and the graphene thin film can be produced over a large area. At this time, a metal catalyst layer is formed in the middle, so that when the electron beam is irradiated, both crystalline silicon and graphene are simultaneously created and bonded at the interface to form a structure.

The pellicle according to the present invention can simultaneously secure high transmittance due to c-Si and mechanical strength due to the graphene layer, so that when applied to a pellicle for EUV exposure, it has high EUV transmittance and excellent durability against EUV, and secures strength that can withstand atmospheric pressure or vacuum processes in a pellicle manufacturing process or an EUV exposure system.

Figure 1 is a cross-sectional view showing a pellicle according to one embodiment of the present invention.
Figure 2 is a cross-sectional view showing a pellicle according to another embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a pellicle mounted in front of a reticle according to one embodiment of the present invention.
Figure 4 is a schematic diagram showing the beam shape of an electron beam source.
FIG. 5 is a schematic diagram showing irradiating a linear electron beam on a large substrate according to one embodiment of the present invention.
Fig. 6 is a schematic diagram showing the QQ' cross-section of Fig. 5.
Figure 7 X-ray diffraction patterns of amorphous silicon and crystalline silicon before and after electron beam irradiation.
Figure 8 is a Raman graph of amorphous silicon and crystalline silicon before and after electron beam irradiation.
Figure 9 is a scanning electron microscope image of crystalline silicon (a) formed by electron beam irradiation and crystalline silicon (b) formed by laser irradiation.
Figure 10 is a Raman spectrum of the graphene layer manufactured in Example 1.

Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. In addition, for the sake of clarity in the drawings, parts irrelevant to the description are omitted, and similar parts are designated with similar reference numerals throughout the specification. Furthermore, for convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced.

Throughout this specification, when it is said that a member is located “on,” “above,” “upper,” “lower,” “lower” or “lower” another member, this includes not only cases where the member is in contact with the other member, but also cases where another member exists between the two members.

Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

pellicle

FIG. 1 is a cross-sectional view showing a pellicle for EUV exposure according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a pellicle for EUV exposure according to another embodiment of the present invention.

The pellicle (80) according to FIGS. 1 and 2 has a shape in which a pellicle film (33), a frame (60) supporting the pellicle film (33), and a binder layer (50) that attaches them together are combined.

The above pellicle film (33) must have high EUV transmittance, excellent high-temperature durability as the temperature rises while EUV is transmitted, and film strength that can withstand the pressure difference caused by the vacuum process in the EUV exposure system.

In particular, the c-Si layer (22) is silicon crystallized by electron beam irradiation, and shows crystallization peaks at the (111), (220), and (311) planes according to XRD (X-ray diffraction) analysis, and in Raman analysis, unlike 480 cm ^-1 indicating amorphous silicon, crystallized Si shows a Raman shift at 520 cm ^-1 indicating crystallization.

The c-Si layer (22) has a thickness of 10 nm to 50 nm and can secure high transmittance by EUV.

At this time, the pellicle film (33) may be any one of the c-Si/graphene, graphene/c-Si, c-Si/SiC/graphene, graphene/SiC/c-Si, c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene structures.

For example, the pellicle film (33) according to FIG. 1 has a multilayer thin film structure in which crystalline silicon (c-Si, 22) and a graphene layer (42) are hetero-bonded.

In particular, in exposure systems that use large amounts of hydrogen (H ₂ ) gas during the process, chemical stability against hydrogen gas must be considered. For example, carbon-based materials exhibit a characteristic of being etched by hydrogen gas, so it is not desirable for these carbon-based unit thin films to be exposed to an atmosphere where they come into contact with hydrogen as the outermost thin film in a pellicle multilayer thin film structure.

Accordingly, as shown in Fig. 2, it is more preferable that the pellicle film (33) have a multilayer thin film structure in which crystalline silicon (c-Si, 22)/graphene layer (42)/crystalline silicon (c-Si, 22) are hetero-bonded.

As a result, the low mechanical properties of conventional crystalline silicon can be structurally supplemented by the strong mechanical properties of the graphene layer, and the elongation and high thermal diffusion rate of the graphene layer can be secured simultaneously.

Meanwhile, while crystalline silicon and graphene are formed by electron beam irradiation, a SiC compound can be formed at the Si-C interface by mutual diffusion, and its thickness can be controlled by increasing the energy and irradiation time (flux) of the electron beam irradiation.

The above pellicle film (33) can have a total thickness of 5 nm to 100 nm, and preferably 5 nm to 50 nm. The thinner the thickness, the higher the EUV transmittance of the pellicle film can be obtained.

The above multilayer thin film and the frame (60) for structurally supporting it are fixed by a binder layer (50). The binder layer (50) may be made of a material having excellent bonding strength with the support frame (60). In order to facilitate bonding, the binder layer (50) is composed of multilayer thin films, and the pellicle film (33) can be firmly fixed to the support frame due to diffusion bonding of these multilayer thin films.

Reticle

FIG. 3 is a cross-sectional view showing a state in which a pellicle (80) according to one embodiment of the present invention is mounted in front of a reticle to cover the reticle (90).

Referring to Fig. 3, the reticle (90) is composed of a high-purity quartz substrate (92); an EUV Mirror layer (93) composed of a multilayer thin film of 80 layers of Mo/Si repeating for reflecting EUV and a final capping layer for protecting Mo/Si; a semiconductor pattern layer (94) formed by stacking a buffer layer on the Mirror layer and an EUV absorbing layer thereon, and then etching a semiconductor pattern in a negative manner so that the EUV Mirror (93) layer formed underneath is exposed in the shape of the pattern.

In order to prevent particles from sticking to the exposed semiconductor pattern etched in negative during the EUV process, a pellicle (80) according to the present invention is positioned on the front surface and used as a particle filter.

A pellicle (80) can protect the reticle (90) from external contaminants (e.g., dust, tin particles). Without a pellicle, foreign substances may adhere to the semiconductor pattern of the reticle (90), causing defects in the EUV lithography process.

In this specification, EUV light refers to light in the EUV wavelength range of 5 nm to 30 nm, but the EUV wavelength currently used commercially uses a wavelength of 13.5 nm created from plasma containing tin (Sn) particles.

In the exposure process, EUV is applied to a wafer on which a resist film has been formed, reflecting the pattern formed on the reticle (90) and exposing it to form a latent pattern on the resist film. A development process then forms the resist pattern on the wafer. However, if foreign matter, such as particles, is present on the reticle, the foreign matter may be transferred onto the wafer along with the pattern, resulting in pattern defects.

A pellicle (80) manufactured according to the present invention protects a reticle (90) from foreign substances, has high transmittance for EUV, and has excellent thermal durability for EUV, and thus has strength that can withstand atmospheric pressure or vacuum processes in a pellicle manufacturing process or an EUV exposure system.

Pellicle manufacturing method

A pellicle is intended to prevent contamination of a reticle (or photomask) used in an exposure process, and is structured such that a pellicle film is attached to a support frame via a binder layer. When a multilayer film in which c-Si and graphene layers are hetero-bonded is used as the pellicle film, the effect is very excellent. However, in the general process for manufacturing a multilayer film of c-Si and graphene layers, several complex steps are performed, such as manufacturing the c-Si and graphene layers separately and then bonding them together, or forming a graphene layer after a crystallization process of amorphous silicon. In particular, in the case of the graphene layer, there is the problem that it is difficult to produce a large area.

The present invention proposes a method for simplifying the manufacturing process of a pellicle film including a multilayer thin film, while having almost no defects in the obtained multilayer thin film and allowing easy process control, and enabling a large-area process that can solve the problem of being limited to a narrow area in the past.

Specifically, the manufacturing of the pellicle comprises the following steps:

(S1) A step of forming a multilayer film including a carbon layer, a metal catalyst layer, and an amorphous silicon layer on a substrate;

(S2) A step in which the amorphous silicon layer on the surface is heated by irradiating an electron beam, and as this heat diffuses downward, the amorphous silicon layer is crystallized into a c-Si layer, the carbon in the carbon layer passes through the metal catalyst layer and diffuses to the c-Si/metal catalyst layer interface, and the carbon that has risen thereafter forms graphene at the interface, all of which are performed simultaneously or sequentially to ultimately form a multilayer thin film in which the c-Si layer and the graphene layer are hetero-bonded;

(S3) A step of forming a binder layer on the outer surface of the multilayer film and also forming a binder layer on the facing surface of the support frame, and then bringing the support frame into contact with the binder layer on the outer surface of the multilayer film to perform diffusion bonding through the binder layer;

(S4) A step of lifting off a multilayer thin film attached to a frame from the above substrate.

In addition, after the above (S4)

(S5) A step of forming at least one of an amorphous silicon layer and a carbon layer on the bottom surface opposite the frame of the frame-attached multilayer thin film; and

(S6) A step of forming at least one of a c-Si layer and a graphene layer by irradiating an electron beam on the bottom surface is further performed.

Through the above steps, the present invention completes a pellicle film having an asymmetric structure of Si/graphene, graphene/c-Si, c-Si/SiC/graphene, and graphene/SiC/c-Si bonded to a frame.

Through additional steps, a pellicle film having a symmetrical structure of c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene bonded to the frame is completed.

The process of crystallizing an amorphous silicon layer into a c-Si layer and diffusion of a carbon layer into a graphene layer can be achieved by a combination of a multilayer film deposition process and an electron beam irradiation process on a substrate. In addition, a pellicle film deposited on a substrate, diffusion bonding with a support frame to fix the pellicle film, and a lift-off process to separate the substrate and the pellicle must be performed. The multilayer film deposition, electron beam irradiation, diffusion bonding, and lift-off processes can be modified in various ways depending on the structure of the pellicle film to be manufactured.

Each step is explained in detail below.

(S1) Multilayer film lamination process

First, a step of forming a multilayer film including an amorphous silicon layer, a metal catalyst layer, and a carbon layer on a substrate is performed.

At this time, the multilayer film may be one type of multilayer film selected from the group consisting of amorphous silicon layer/metal catalyst layer/carbon layer, amorphous silicon layer/carbon layer/metal catalyst layer, carbon layer/metal catalyst layer/amorphous silicon layer, carbon layer/amorphous silicon layer/metal catalyst layer, metal catalyst layer/carbon layer/amorphous silicon layer, and metal catalyst layer/amorphous silicon layer/carbon layer.

The substrate may be any one of inorganic materials such as glass, quartz, Pyrex, alumina, zirconia, and sapphire; organic materials such as polyethylene naphthalate, polyethersulfone, polyimide, polycarbonate, polytetrafluoroethylene, polyethylene terephthalate, polystyrene, polyvinyl chloride, polyvinylpyrrolidone, polyethylene, polydimethylsiloxane, polymethyl methacrylate, and rubber; metal plates such as thin stainless steel, thin nickel, thin copper, thin Al, and thin Invar; and opaque inorganic substrates such as Si, Ge, GaN, GaAs, InP, InSb, InAs, AlAs, AlSb, CdTe, ZnTe, ZnS, ZnSe, CdSe, CdSb, GaP, and SiC.

The process of manufacturing a conventional graphene thin film using CVD or carbonization requires a high-temperature process, which limits the use of the substrate. However, the electron beam irradiation process of the present invention can limit the temperature transferred to the substrate by heating only the surface, so there is no limitation in the use of the substrate.

The substrate must be separated from the pellicle in a subsequent lift-off process, and a pretreatment process may be performed to facilitate separation.

The pretreatment process of the substrate is performed by plasma implantation treatment, hydrophobic plasma treatment, deposition of a spacing layer such as Si:H, or a combination thereof.

Plasma implantation treatment creates plasma using a gas with a small atomic radius, such as hydrogen or helium, on a substrate, and gives the plasma energy of several hundred eV to several tens of MeV to implant (+) gas ions with energy into the substrate, so that the implanted gas is pushed out of the substrate by diffusion (heat application) and separates from the pellicle.

Hydrophobic plasma treatment is a hydrophobic treatment performed on the surface of a substrate, and is performed alone or after plasma treatment. Hydrophobic treatment can be performed after (+) ion implant irradiation is completed, so that the surface of the substrate becomes hydrophobic and the pellicle can be easily detached. The surface can be hydrophobicized using atmospheric pressure plasma or vacuum plasma by mixing C ₂ F ₂ , C ₂ F ₄ , C ₂ F ₆ , C ₃ F ₈ or preferably C ₄ F ₈ gas with He gas.

The separation layer is a layer from which gas can be emitted when the temperature rises, and the separation between the substrate and the pellicle occurs due to the emitted gas. The separation layer may be a layer that can eject H, O, N gases by heating, such as CuN, CuO, Si:H, etc.

These amorphous silicon layers can be formed by deposition processes, including plasma enhanced chemical vapor deposition (PECVD), chemical vapor deposition (CVD), low-pressure chemical vapor deposition (LPCVD), RF/DC sputtering, ion beam deposition (IBD), vacuum deposition, electron beam deposition, ion plating, or pulsed laser deposition.

At this time, the amorphous silicon layer is formed with a thickness ranging from 5 nm to 50 nm. This thickness range takes into account the final thickness of c-Si formed by electron beam irradiation, and represents an appropriate thickness that can secure optimal properties when applied to an EUV pellicle.

The metal catalyst layer acts as a catalyst not only in crystallizing the amorphous silicon layer but also in crystallizing the carbon layer into graphene. This metal catalyst layer can be ultimately removed using an etchant after the electron beam irradiation process. Without the formation of the metal catalyst layer, crystallization into graphene is impossible.

The Ni catalyst metal forming the metal catalyst layer must have an FCC (Face-Centered Cunic) structure. Crystal structures include BCC (Body-Centered Cubic Lattics), FCC, and HCP (Closed Packed Hexagonal Lattics, HCP) structures, and most metals have one of these crystal lattice structures.

By electron beam irradiation, carbon atoms of graphene precursor form aromatic hexagonal C=C- bonds, and at this time, carbon atoms are adsorbed on the surface of the catalyst metal and grow into a graphene film. If the surface energy of the catalyst metal is unstable, the speed at which carbon atoms are adsorbed is different, resulting in the carbon atoms becoming graphitized rather than forming graphene. In the FCC structure of the Ni catalyst metal, the (111) plane is the most stable and has a uniform surface energy, so that carbon atoms are evenly anchored, enabling stable growth into a graphene film.

Preferably, the metal catalyst layer is preferably a metal having an fcc structure when Ni, and other catalyst metals include at least one single metal or alloy selected from the group consisting of Ti, Al, Zn, Co, Cu, Pt, Ag, and Au.

The thickness of this metal catalyst layer is not particularly limited, but may be 0.1 nm to 10 nm.

The formation of the metal catalyst layer is not particularly limited in the present invention, and any method capable of forming a uniform thin film across the entire substrate may be used. For example, the dry deposition process described above may be used.

The carbon layer according to the present invention is a layer that can be converted into graphene by electron beam irradiation, and can be manufactured through a wet process or a dry process.

The carbon layer formed through the wet process refers to a graphene cured film formed by coating and then curing a graphene precursor solution, and the graphene precursor layer formed through the dry process refers to a carbon deposition layer formed through CVD, PECVD, sputtering, or vacuum deposition. This carbon layer is later converted into graphene through electron beam irradiation, and its thickness can be easily controlled through the wet process and the dry process, so the thickness of the final obtained graphene layer can be easily controlled. In addition, since the wet process allows for the production of a carbon layer over a large area, there is an advantage in that a large-area graphene layer can be easily formed compared to the conventional method.

In the production of a carbon layer through a wet process according to one embodiment of the present invention, a graphene precursor can be produced by applying a graphene precursor solution containing a graphene precursor and a solvent, drying the solution, and then curing the solution.

The graphene precursor is a polymer, and any polymer that has a graphene structure upon electron beam irradiation can be used. Representative examples of the graphene precursor include one selected from the group consisting of polyimide, polyacrylonitrile, polymethyl methacrylate, polystyrene, rayon, lignin, pitch, borazine oligomers, and combinations thereof. Among these graphene precursors, an aromatic hydrocarbon series, i.e., polyimide, is preferred so that aromatic hexagonal C=C- bonds can easily form upon electron beam irradiation. In addition, the polymer is preferably an oligomer so that a subsequent curing process can be performed.

The final graphene properties and type can be controlled by adjusting the composition of the graphene precursor. For example, polyimide or PMMA can produce highly conductive graphene films, while borazine oligomers can produce white graphene films.

Any solvent that can sufficiently dissolve the graphene precursor and control the viscosity within a predetermined range may be used. The solvent may vary depending on the composition or molecular weight of the graphene precursor, i.e., the polymer, and may include, for example, one or more selected from the group consisting of dimethylformamide (DMF), formaldehyde, chloroform, dimethylacetamide (DMA), pyridine, benzopyridine, benzene, xylene, toluene, dioxane, tetrahydrofuran (THF), diethyl ether, dimethyl sulfoxide (DMSO), and n-methyl-2-pyrrolidone (NMP).

If necessary, the graphene precursor solution may further include additives for controlling dispersibility, application properties, viscosity, etc., and/or dopants for doping purposes. The types and content ranges thereof are not particularly limited in the present invention and can be appropriately selected by those skilled in the art.

The above graphene precursor solution is applied to a metal catalyst layer using a conventional wet coating method, and then dried and cured to form a carbon layer.

At this time, the viscosity of the graphene precursor solution is limited to facilitate coating and form a uniform dry film. Preferably, it is within the range of 100 cps to 10 cps, and the lower the viscosity, the lower the coating thickness. If the concentration is below the above range, multiple coating processes are required to form a graphene precursor dry film of a predetermined thickness, which may make it difficult to form a uniform dry film. Conversely, if the viscosity is too high, the physical properties of the entire carbon layer obtained after the subsequent curing process may not be uniform, so it is appropriately used within the above range.

The wet coating method may be any one of roll coating, spray coating, impregnation coating, spin coating, gravure coating, knife coating, bar coating, slot die coating, or screen printing, and among these, spray coating, spin coating, or roll coating in the case of a continuous process may be used to facilitate the process and form a uniform coating film.

After coating, the solvent is removed through drying. The drying temperature and method may vary depending on the type of solvent used, and typically hot air drying or induction heating drying methods may be used. The drying is performed at 30°C to 90°C, 35°C to 85°C, or 40°C to 80°C, and depressurization may be performed if necessary.

After drying, the dried film of the graphene precursor on the metal catalyst layer is cured by applying heat to form a carbon layer. The temperature for curing varies depending on the type of polymer of the graphene precursor, and in the case of polyimide, it was performed at 400°C.

The carbon layer obtained after curing may have a thickness of 5 nm to 200 nm, preferably 0.5 nm to 20 nm. The thickness of this carbon layer affects the thickness of the total graphene layer produced by the electron beam. If the thickness is too thin, graphene cannot be formed into a stable structure, whereas if it is too thick, graphitization or multi-layered graphite may be formed.

In addition, the carbon layer through the dry process according to one embodiment of the present invention is a carbon deposition layer, and can be deposited by a method such as chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), sputtering, graphite ion beam deposition, or physical vapor deposition. At this time, the carbon source is a hydrocarbon gas including CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₂ H ₆ , etc., and in PVD, a graphite target is used alone or in combination with the hydrocarbon gas. The carbon deposition layer can be formed without a separate curing process and has the thickness range of the carbon layer mentioned above.

The multilayer film including the amorphous silicon layer, the metal catalyst layer, and the carbon layer as described above has a heterojunction structure of c-Si/graphene layers through a subsequent process.

(S2) Electron beam irradiation process

Next, a step is performed to form a c-Si/graphene pellicle film having a multilayer thin film structure in which the c-Si layer and the graphene layer are hetero-bonded by simultaneously performing crystallization into the c-Si layer and diffusion of carbon through the metal catalyst layer to the Si/catalyst interface and formation of graphene at the interface by irradiating the electron beam.

Electron beam irradiation is performed to fabricate a heterojunction multilayer thin film structure of c-Si and graphene layers. Electron beam irradiation can be performed separately to form the c-Si and graphene layers separately, or simultaneously to form the c-Si and graphene layers simultaneously. For example, amorphous silicon can be crystallized simultaneously with the crystallization of graphene after the formation of the multilayer thin film, but if necessary, silicon-only crystallization can be performed first after silicon deposition.

There are various known methods for crystallizing amorphous silicon, including solid phase crystallization (SPC), laser induced crystallization (LIC), metal induced crystallization (MIC), and joule heating induced crystallization (JIC), but there are differences in the state of the thin film after crystallization.

c-Si formed by electron beam irradiation is more easily crystallized than c-Si formed by conventional laser beam irradiation, and in particular, metal-induced crystallization by a metal catalyst layer has the advantage of easily inducing crystallization. In addition, c-Si formed by electron beam irradiation has the advantage of not having a hill-lock on the grain boundary or surface compared to c-Si formed by laser beam irradiation, and since the grain boundary serves as a path for crack propagation, it can have the advantage of not being easily broken compared to a film crystallized by a laser beam when lifted off as a thin film and left free-standing inside the frame.

Figure 7 is an X-ray diffraction analysis pattern of c-Si irradiated with an electron beam at room temperature, and it can be seen that crystallization peaks are shown at the (111), (220), and (311) planes by electron beam irradiation.

Figure 8 is a Raman spectrum, which shows a sharp peak at a different location from 480 cm ^-1 , which indicates amorphous silicon, in the case of c-Si irradiated with electron beams, and a peak at 520 cm ^-1 , which indicates crystallization similar to that of Si Wafer, indicating that silicon crystallization occurred through electron beam irradiation.

Figure 9 is a scanning electron microscope (SEM) image showing the state of the thin film. It can be seen that, while c-Si crystallized by laser irradiation has grain boundaries and hill-locks on the surface that are formed as it melts and solidifies, c-Si crystallized by electron beam irradiation forms a high-quality thin film without grain boundaries.

In Fig. 9, amorphous silicon crystallized by laser irradiation (b) has grain boundaries several μm in size, but c-Si crystallized by electron beam irradiation (a) does not have grain boundaries several μm in size. When there is an external force or impact, especially when there is a difference in vacuum pressure between the front and back of the pellicle, a crack that starts to break on one side is generated, which easily propagates along the grain boundaries and causes destruction of the pellicle. Therefore, crystalline silicon c-Si without grain boundaries created by electron beam irradiation can be a material with excellent properties that can increase the strength of the pellicle and increase the transmittance of EUV.

In addition, when an electron beam is irradiated on the surface of amorphous silicon/metal catalyst layer/carbon, the metal of the metal catalyst layer exists in a solid-solution state, and the carbon in the carbon layer diffuses and moves to form a carbon precipitation layer at the interface of the metal catalyst layer and silicon in contact with the amorphous silicon layer. This precipitation layer is converted to graphene by the metal, which acts as a catalyst to form a graphene structure. At this time, the grown graphene is obtained in the form of a dense thin film without pores or defects, and the growth occurs uniformly at a relatively same rate from the surface of the metal catalyst layer, so that a graphene layer with high smoothness can be obtained. The metal catalyst layer forms a metal-carbon (e.g., Ni-C) bond during electron beam irradiation, and this automatically flies away through high-temperature sublimation or is removed by etching, so that it does not exist on the surface of the final pellicle film.

Figure 10 is a Raman spectrum of graphene produced by irradiating an electron beam on a carbon layer in contact with a catalyst. It can be seen that a 1300 cm ^-1 : D peak, a 1580 cm ^-1 : G peak, and a 2700 cm ^-1 : 2D peak representing graphene are confirmed, indicating that a graphene thin film has been formed.

In particular, among various embodiments, in the present invention, a c-Si layer and a graphene layer can be formed simultaneously through electron beam irradiation. When forming a c-Si layer and a graphene layer separately, each must be performed in a separate process, which causes inconvenience in the process, a problem that it is difficult to form a bonded structure of the two layers because a complete crystal layer remains when each layer is formed, and an increase in cost. However, in the present invention, crystallization of the amorphous silicon is performed simultaneously through electron beam irradiation for conversion from a graphene precursor to graphene, thereby solving the problems of the conventional process and cost.

The electron beam irradiation process can relatively shorten processing time by controlling energy and flux, resulting in thin films with improved properties at a much faster rate than conventional heat treatment methods. Furthermore, it can be performed by surface heating via electron beam irradiation without requiring a separate heat treatment (i.e., applying heat to the substrate). This allows for unlimited use of substrates, which are traditionally restricted by heat-induced cracking or warping. Furthermore, the process requires relatively low costs.

In addition, by changing the structure of the multilayer thin film in various ways, the composition of the final pellicle film can be combined in various ways.

Electron beam irradiation is performed within a vacuum chamber capable of electron beam irradiation, as known in the art. The vacuum chamber includes a support placed inside, a substrate mounted on the support, and an electron beam source positioned to irradiate the substrate with an electron beam in a direction facing the substrate.

To generate an electron beam, a field emission method can be used, which extracts electrons by applying a high negative voltage to a sharp tip, a thermionic method, which heats a filament such as tungsten or LaB ₆ and causes electrons to eject from the surface of the filament, or a plasma extraction method, which extracts and accelerates electrons by shielding the plasma with a grid and applying voltage to the plasma at the same time.

Among these, the plasma extraction method allows for a large linear source, and by scanning it in the vertical direction of a large substrate, a large area can be uniformly processed. At this time, the power source for creating the plasma can use various types such as LF, MF, HF, RF, UHF, and Microwave depending on the AC frequency, and also can use various types such as Capacitive, Inductive, ICP, ECR, Helical, Helicon, Hollow cathode, and Hot filament depending on the shape of the electrode or antenna, and high-pressure plasma such as atmospheric pressure plasma can also be used.

Electron beam irradiation can be performed by moving the support at a constant speed while the electron beam source is fixed, or by moving the support while the electron beam source is fixed. The former is preferable because it is advantageous in terms of process control.

At this time, there may be more than one electron beam source, and for a large-area pellicle film, multiple electron beam sources may be used, and these may be arranged in series or parallel.

Fig. 4 is a schematic diagram showing the beam shape of an electron beam source. Depending on the cross-sectional shape (i.e., spot) of the electron beam source, it can be a round source (Fig. 5a) that generates a circular electron beam, or a linear source (Fig. 5b) that generates a linear electron beam with different length and width ratios. Through various arrangements of these, it is possible to form a large-area pellicle film. Preferably, the electron beam source can be a linear gun in the shape of a long rectangular parallelepiped having a length similar to the width of the substrate.

Fig. 5 is a schematic diagram showing irradiating an electron beam onto a substrate according to one embodiment of the present invention, and Fig. 6 is a schematic diagram showing a Q-Q' cross-section. In this case, the electron beam irradiated in the drawing is shown as being irradiated only to a predetermined area, but in reality, when irradiating the electron beam, these electron beams fly while spreading out to some extent, so that the electron beam flies by filling the predetermined flight space entirely, and thus the electron beam is irradiated simultaneously to a predetermined area of the opposing substrate.

Referring to Fig. 5, after three linear electron beam sources (source 1, source 2, source 3) are arranged in series on a substrate on which an amorphous silicon layer/metal catalyst layer/carbon layer are sequentially formed, the substrate is fixed and the electron beam is irradiated while the electron beam source is moved in one direction, so that the electron beam is irradiated over the entire substrate, thereby forming a pellicle film with a hetero-bonded c-Si/graphene layer over a large area. As shown in Fig. 6, not only is large-area processing possible by serially connecting the Linear Beam Source, but the processing speed can also be increased by connecting another Linear Beam Source in parallel.

Additionally, three electron beam sources are arranged in series so that the entire width of the substrate can be irradiated with the electron beam. At this time, as shown in Fig. 6, the electron beam source is moved in one direction so that the electron beam is irradiated across the entire substrate, and after irradiation, the carbon layer is converted into a graphene layer and the amorphous silicon layer is converted into c-Si.

The method illustrated in FIGS. 5 and 6 is a method of scanning by moving three preceding electron beam sources by arranging them in series. This method belongs to one embodiment of the present invention, and the number and shape of the electron beam sources can be changed depending on the size of the substrate, and the arrangement of the electron beam sources can also be done in a parallel manner, a serial manner, or a mixed manner thereof. In addition, although the above example described a method of scanning by moving the electron beam sources, a method of moving the substrate in one direction while fixing the electron beam sources can be used.

During electron beam irradiation, the transport speed of the electron beam source or substrate must be such that it provides sufficient time for the c-Si/graphene layer to form. That is, the thinner the amorphous silicon layer and carbon layer, and the higher the energy of the applied electron beam, the higher the transport speed. More specific conditions can be appropriately selected and modified by those skilled in the art.

The electron beam irradiated onto the substrate is accelerated by the applied voltage to have a kinetic energy of 50 eV to 50 keV, preferably 1 KeV to 10 KeV, and is irradiated onto the process area on the substrate.

The above electron beam irradiation process is performed in the presence of an inert gas, and the inert gas is preferably one or more selected from nitrogen, helium, neon, argon, xenon, or a mixed gas thereof, but is not limited thereto.

The steps of lamination, drying, curing, and electron beam irradiation of each layer, including the electron beam irradiation of the aforementioned main step, can be performed continuously and automatically through a roll-to-roll process, or can be performed separately for each step. Thus, one or more steps of the method disclosed herein can be performed automatically, for example, through the use of a computer-controlled automatic processing line. For example, large-area graphene processing is technically possible through a continuous line after mounting a linear electron beam source in a roll-to-roll vacuum chamber system.

Additionally, in order to remove a trace amount of amorphous carbon layer present on the graphene thin film after electron beam irradiation in the above step, a process of irradiating the surface with a hydrogen beam created by plasma etching using hydrogen or hydrogen plasma activation can be further performed.

After electron beam irradiation, the metal catalyst layer can be removed through an etching process.

Meanwhile, by controlling the electron beam irradiation process, a SiC layer is formed at the Si/carbon interface through a reaction between Si and carbon. This allows for controlling the formation and thickness of the SiC layer by adjusting the electron beam irradiation time. This allows for the production of pellicle films containing SiC, such as c-Si/SiC/graphene, c-Si/SiC/graphene/SiC/c-Si, or graphene/SiC/c-Si/SiC/graphene.

For example, a multilayer film can be made into a mirror structure by combining the sequence of deposition of a multilayer film, electron beam irradiation, and etching of the outermost metal catalyst layer, and additionally, the formation of a SiC layer at the Si/C interface can be controlled by controlling the electron beam irradiation time.

(S3) Diffusion bonding process

Next, a binder layer is formed on the outer surface of the multilayer film, a support frame is placed against the substrate, and diffusion bonding is performed through the binder layer.

The diffusion bonding process refers to a bonding process between a pellicle film and a support frame for fixing the pellicle film.

First, a binder layer is formed on the outer surface of the pellicle film (or multilayer film before electron beam irradiation).

The material of the above binder layer is a material that is easy to bond depending on the material of the support frame, and has a certain thickness during the diffusion bonding process, and is formed to be 0.1 nm to 100 nm so that the bonding strength can be maintained after the final bonding.

If necessary, a buffer layer may be additionally formed to contact the binder layer.

Next, a buffer/binder layer is deposited on the surface of the substrate on which the pellicle film is formed and the surface of the support frame that faces the pellicle film to fix the pellicle film, and then diffusion bonding is performed through the binder layer.

The support frame is made of silicon wafer, Ti metal plate, aluminum alloy or ceramic material, and should have low high-temperature thermal expansion, should not be deformed even at high temperatures, and preferably has a melting point of over 800℃ and 1000℃.

The ceramic support frame is preferably a black ceramic mainly composed of alumina, zirconia, etc., and containing manganese, chromium, carbon, etc. as coloring agents for black coloring. This is to minimize the reflection of exposure light on the support frame.

Diffusion bonding (cladding) is a bonding technique that uses the diffusion of atoms that occurs between the bonding surfaces by bringing the binder layer and the support frame into close contact. It is characterized by less thermal stress or deformation after bonding and less material deterioration due to structural change, and has the advantage of being able to bond not only the same materials but also heterogeneous materials with different properties and bond complex shapes.

In the present invention, the pellicle film can be firmly fixed to the support frame through diffusion bonding between the binder layer and the support frame.

Diffusion bonding can be performed by applying pressure at a temperature below the melting point of the support frame to a degree that plastic deformation is unlikely to occur, and may vary depending on the materials of the binder layer and the support frame.

The binder layer forms a multilayer film selected from at least one of low-temperature molten metals; eutectic alloys having a lower melting temperature when alloyed with any one of Zn, Ga, In, Sn, or Au and any one of Al, Si, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Te, Ru, Pd, Ag, or Pt; general alloys; and oxides, nitrides, carbides, and borides thereof, and the binder is formed on both sides of the multilayer film and the support frame and diffusion bonded thereto.

According to an implementation example, in the case of a frame made of Si material, diffusion bonding can be performed by applying a pressure of 0.1 MPa to 1.0 MPa at a temperature of 300°C to 600°C to a eutectic alloy buffer layer formed of Ti/Au. At this time, if an appropriate temperature and pressure are not applied, the strength at the bonding portion is low, and the pellicle film may be detached from the support frame when the pellicle is mounted on the reticle or during a process before or after that, so the temperature and pressure are appropriately adjusted within the above range.

(S4) Lift-off process

Next, a process of lifting off the pellicle from the substrate is performed.

Lift-off is the process of separating the pellicle from the substrate.

The above lift-off process can be performed by heating the back surface of the substrate using a heater or an RTA halogen lamp, or by heating using an electron beam or laser irradiation. Heating the back surface of the substrate can cause pellicle separation due to differences in thermal expansion indices between the substrate and c-Si, or between the substrate and graphene. Therefore, a method that rapidly increases the substrate temperature may be preferred.

According to one embodiment of the present invention, a lift-off process is performed by irradiating the back surface of the substrate with an electron beam of 2 keV to 50 keV for 30 seconds to 5 minutes. The electron beam is the same as the electron beam in the previous step (S2), and the process can be performed by scanning the entire substrate using a linear electron beam. This method has the advantage of making it easier to separate a pellicle film having a large area.

In particular, when the substrate is subjected to hydrogen or helium gas plasma implantation treatment so that gas particles are embedded on the substrate surface and are ejected to the interface with the pellicle at the same time as the substrate is heated, or when additional plasma hydrophobic treatment is performed on the plasma implanted substrate to perform surface chemical treatment to facilitate peeling, or when a separation layer such as a CuO, CuN, or Si:H layer is formed at the interface with the substrate, hydrogen, helium, nitrogen, or oxygen gases are separated and released from these layers by heating the back surface of the substrate, so that the separation of the pellicle between the substrate and c-Si, or between the substrate and graphene, becomes easier.

The lift-off process is particularly important when forming a pellicle film over a large area. While separation of the substrate and the pellicle film is easy when the pellicle film is small, there is a risk that portions of the pellicle film may tear or be damaged during the lift-off process when forming a large-area pellicle film. Therefore, when performing heat treatment, electron beam, or laser irradiation along with substrate pretreatment, a high-quality pellicle film can be separated and recovered intact after the lift-off process.

The pellicle recovered through the above steps has a shape in which the pellicle film is supported by a support frame, and at this time, the pellicle film has a structure in which c-Si/graphene is hetero-bonded.

Additionally, by extending the irradiation time during electron beam irradiation, it is possible to manufacture a pellicle in which c-Si/SiC/graphene are bonded.

Additional processes: amorphous silicon deposition and electron beam irradiation steps

Additionally, after the above (S4), an additional process can be performed to manufacture a pellicle having a multilayer thin film with a symmetrical structure of other shapes, for example, c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene.

According to one embodiment, after step (S4), a step of forming at least one of an amorphous silicon layer and a carbon layer on the bottom surface opposite the frame of the frame-attached multilayer thin film (S5) is additionally performed; and a step of forming at least one of a c-Si layer and a graphene layer by irradiating the bottom surface with an electron beam (S6) is additionally performed, thereby manufacturing pellicles of various structures.

As an example, in (S5), an amorphous silicon layer is deposited on a graphene layer of a multilayer thin film to produce a pellicle with a c-Si/graphene/c-Si structure.

As another example, in (S5), a carbon layer is deposited on a c-Si layer of a multilayer thin film to produce a pellicle with a graphene/c-Si/graphene structure.

As another example, by extending the electron beam irradiation time in the above (S6), a SiC layer can be further formed between the c-Si layer and the graphene layer, and a pellicle having a c-Si/SiC/graphene/SiC/c-Si or graphene/SiC/c-Si/SiC/graphene structure is manufactured.

As another example, the above (S5) and (S6) can be performed multiple times.

As another example, both an amorphous silicon layer and a carbon layer can be formed in the above (S5), and a metal layer can be additionally formed here.

In addition, if the metal catalyst layer remains on the top layer of the multilayer thin film before the step (S5), the metal catalyst layer is etched. For example, a c-Si/graphene/metal catalyst layer is formed through steps (S1) to (S4), and the metal catalyst layer formed on the graphene layer is removed through etching.

If the metal catalyst layer is formed thinly, it may not remain after the (S4) step, but if it is formed thickly, it remains, and after removal through etching, the (S5) process is further performed.

Table 1 below summarizes the method for manufacturing a pellicle proposed in the present invention. The process in the table below is only an example, and pellicles of various structures can be manufactured by changing the material of the multilayer thin film of (S1), the electron beam irradiation time of (S2) and (S6), and the additional deposition material of (S5).

(S1) Multilayer film formation (a) c-Si/graphene: 1 of amorphous silicon layer/metal catalyst layer/carbon layer/substrate, amorphous silicon layer/carbon layer/metal catalyst layer/substrate, metal catalyst layer/amorphous silicon layer/carbon layer/substrate
(b) Graphene/c-Si: 1 of carbon layer/metal catalyst layer/amorphous silicon layer, carbon layer/amorphous silicon layer/metal catalyst layer, metal catalyst layer/carbon layer/amorphous silicon layer (S2) Electron beam irradiation O O, extension of investigation time O O O, extension of investigation time O, extension of investigation time (S3) Diffusion bonding O O O O O O (S4) Lift-off O O O O O O (S5) Additional deposition - - Amorphous silicon deposition Carbon layer deposition Amorphous silicon deposition Carbon layer deposition (S6) Electron beam irradiation - - O, c-Si formation, O, graphene formation O, c-Si formation, extended irradiation time O, graphene, formation, extended irradiation time Pellicle membrane structure c-Si/graphene, graphene/c-Si c-Si/SiC/graphene, graphene/SiC/c-Si c-Si/graphene /c-Si Graphene/c-Si/graphene c-Si/ SiC/ graphene/
SiC/c-Si Graphene/SiC/
c-Si/SiC/graphene -(S3) and/or (S5) Addition of a process for removing the metal catalyst layer through etching

The method for manufacturing a pellicle for EUV exposure of the present invention as described above has the advantage of being able to manufacture a large-area, high-throughput pellicle that can uniformly process the beam over the entire pellicle area, since the process is very simple and a linear electron beam of a size that covers a large pellicle area is possible.

As a result, the pellicle manufactured according to the present invention protects the reticle from foreign substances, has high EUV transmittance, and has excellent durability against EUV, and has strength that can withstand atmospheric pressure or vacuum processes in the pellicle manufacturing process or the EUV exposure system. In addition, It has the advantage of being able to be produced on a large scale.

[Example]

Hereinafter, the present invention will be described in detail through examples. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited by the following examples.

Example 1: Graphene/c-Si structure pellicle

A pellicle membrane and a pellicle mounted on a support frame were manufactured through the following steps.

A 40 nm thick amorphous silicon layer was deposited on the surface of a Si wafer that had been pretreated with atmospheric hydrophobic plasma and H ₂ plasma implantation by PECVD, and then a 10 nm thick Ni thin film was formed as a metal catalyst layer by sputtering. A graphene precursor solution (polyimide/NMP solution, 10 cps) was coated on the metal catalyst layer, dried at 40°C for 10 minutes, and then thermally cured at 400°C for 20 minutes to produce a 25 nm thick graphene precursor cured coating film.

The above substrate was transferred into an electron beam deposition chamber, and then irradiated with an electron beam of 4 Kev at room temperature for 5 minutes to form a pellicle film in which a 35 nm thick c-Si layer and a 10 nm thick graphene layer were hetero-bonded.

Next, a 20 nm thick binder layer was formed by sputtering using Ti metal along the outer surface of the graphene layer, which is the outermost layer of the pellicle film. Meanwhile, a binder layer using Ti/Au metal was also deposited on the opposing frame, and then a diffusion bonding process was performed by applying a temperature of 600°C and a pressure of 0.2 MPa.

Next, a 4 keV electron beam was irradiated on the back surface of the substrate for 2 minutes to create a gap between the c-Si, the lowest layer of the pellicle film, and the substrate by ejecting hydrogen gas, and the pellicle was lifted off from this gap to recover the pellicle, thereby fabricating a pellicle having a graphene/c-Si structure.

Example 2: c-Si/graphene structure pellicle

A pellicle was manufactured in the same manner as in Example 1 above, but with a different thin film stacking order.

After coating a graphene precursor solution (polyimide/NMP solution, 10 cps) on the surface of a Si wafer that had been pretreated with H ₂ Plasma implantation and atmospheric pressure hydrophobic plasma, the solution was dried at 40°C for 10 minutes and then thermally cured at 400°C for 20 minutes to produce a 25 nm thick graphene precursor cured film. Then, a 10 nm thick Ni thin film was formed as a metal catalyst layer through sputtering, and a 40 nm thick amorphous silicon layer was deposited on the metal catalyst layer through PECVD.

The above substrate was transferred into an electron beam chamber, and then irradiated with a 4 Kev electron beam at room temperature for 5 minutes to form a pellicle film in which a 35 nm thick c-Si and a 10 nm thick graphene layer were hetero-bonded after the carbon catalyst layer was diffused and moved.

Next, a 20 nm thick binder layer was formed by sputtering using Ti metal along the outer surface of the c-Si layer, which is the outermost layer of the pellicle film. Meanwhile, a binder layer using Ti/Au metal was also deposited on the opposing frame, and then a diffusion bonding process was performed by applying a temperature of 600°C and a pressure of 0.2 MPa.

Next, a 4 keV electron beam was irradiated on the back surface of the substrate for 2 minutes to create a gap between the c-Si, the lowest layer of the pellicle film, and the substrate by ejecting hydrogen gas, and a multilayer film of c-Si/graphene/Ni was lifted off from this.

Next, the Ni layer was removed through etching to fabricate a pellicle having a c-Si/graphene structure that was finally bonded to the frame.

Example 3: c-Si/SiC/graphene structure pellicle

The same procedure as in Example 2 was performed, but the electron beam irradiation time was extended to produce a c-Si/SiC/graphene pellicle in which SiC was formed at the interface between the c-Si layer and the graphene layer.

Example 4: c-Si/graphene/c-Si structure pellicle

A pellicle membrane and a pellicle mounted on a support frame were manufactured through the following steps.

After coating a graphene precursor solution (polyimide/NMP solution, 10 cps) on the surface of a Si wafer that had been pretreated with H ₂ Plasma implantation and atmospheric pressure hydrophobic plasma, the solution was dried at 40°C for 10 minutes and then thermally cured at 400°C for 20 minutes to produce a 25 nm thick graphene precursor cured film. Then, a 10 nm thick Ni thin film was formed as a metal catalyst layer through sputtering, and a 40 nm thick amorphous silicon layer was deposited on the metal catalyst layer through PECVD.

The above substrate was transferred into an electron beam chamber, and then irradiated with a 4 Kev electron beam at room temperature for 5 minutes to form a pellicle film in which a 35 nm thick c-Si and a 10 nm thick graphene layer were hetero-bonded after the carbon catalyst layer was diffused and moved.

Next, a 20 nm thick binder layer was formed by sputtering using Ti metal along the outer surface of the c-Si layer, which is the outermost layer of the pellicle film. Meanwhile, a binder layer using Ti/Au metal was also deposited on the opposing frame, and then a diffusion bonding process was performed by applying a temperature of 600°C and a pressure of 0.2 MPa.

Next, a 4 keV electron beam was irradiated on the back surface of the substrate for 2 minutes to create a gap between the c-Si, the lowest layer of the pellicle film, and the substrate by ejecting hydrogen gas, and a multilayer film of c-Si/graphene/Ni was lifted off from this.

Afterwards, the Ni layer, which is a metal catalyst layer, was etched to leave the c-Si/graphene attached to the frame, and then amorphous silicon was deposited on the opposite graphene surface using PECVD and irradiated with an electron beam to create a crystallized c-Si layer, and finally, a c-Si/graphene/c-Si pellicle bonded to the frame was manufactured.

Example 5: c-Si/SiC/graphene/SiC/c-Si structure pellicle

The same procedure as in Example 3 was performed, but the electron beam irradiation time was extended to produce a c-Si/SiC/graphene/SiC/c-Si pellicle in which SiC was formed at the interface between the c-Si layer and the graphene layer.

Test Example 1: Analysis of crystalline silicon layers

(Crystallinity analysis of crystalline silicon layers)

To confirm the formation of a c-Si layer by electron beam irradiation after depositing amorphous silicon, X-ray diffraction analysis and Raman analysis were performed.

Figure 7 shows an X-ray diffraction pattern of a c-Si layer irradiated with an electron beam at an energy of 4 keV after depositing a 200 nm thick amorphous silicon layer via PECVD on a Si wafer with a natural oxide film on the surface. As can be seen from Figure 7, silicon irradiated with an electron beam exhibits crystal peaks at (111), (220), and (311).

Figure 8 is a Raman spectrum of a c-Si layer with the same results after electron beam irradiation. As shown in Figure 8, the c-Si layer irradiated with electron beam shows a peak at a different location from amorphous silicon and a peak at a similar location to a crystalline silicon wafer, indicating that silicon crystallization occurred through electron beam irradiation.

(Analysis of crystallization surface by electron beam vs. laser irradiation)

Amorphous silicon was deposited on two Si wafer substrates by PECVD, and one substrate was irradiated with a 4 KeV electron beam, and the other substrate was irradiated with a laser to form a crystalline c-Si layer.

Fig. 9a is a scanning electron microscope image of a c-Si layer irradiated with an electron beam, and Fig. 9b is a scanning electron microscope image of a crystalline c-Si layer irradiated with a laser. As shown in Figs. 9a and 9b, the crystallization of silicon by electron beam irradiation has the advantage of not having a grain boundary or a hill-lock on the surface compared to silicon irradiated with a laser beam, and this can have the advantage of not being easily broken compared to a c-Si layer irradiated with a laser because there is no grain boundary that provides a path for destruction when a thin pellicle film is made free-standing.

Test Example 2: Graphene Layer Analysis

Figure 10 is a Raman spectrum of the graphene layer manufactured in Example 1.

A 40 nm thick amorphous silicon layer was deposited on the surface of a Si wafer by PECVD, and then a 10 nm thick Ni metal thin film was formed as a metal catalyst layer by sputtering. A graphene precursor solution (polyimide/NMP solution, 101) was coated on the metal catalyst layer, dried at 40°C for 10 minutes, and then thermally cured at 400°C for 20 minutes to produce a 25 nm thick graphene precursor cured coating film. An electron beam was irradiated here, and the graphene layer appearing on the surface was subjected to Raman analysis.

Here, A is the peak that appeared when the electron beam energy was 4 keV, B is the peak that appeared when the electron beam energy was 3.5 keV, and C is the peak that appeared when the electron beam energy was 3 keV for 2 minutes, respectively. The typical D peak and G peak that appear when heat or energy is applied to the carbon layer represent the Disorder peak and Graphite peak, respectively, and 2D is a typical peak that appears only when graphene is formed.

Looking at Figure 10, the 2700 cm ^-1 : 2D peak representing graphene is confirmed along with the 1350 cm ^-1 : D peak, the 1580 cm ^-1 : G peak, and it can be seen that a graphene film was formed by the energy of the electron beam and the Ni catalyst.

The EUV pellicle according to the present invention can be applied to a lithography process of a semiconductor device.

22: c-Si layer
42: Graphene layer
50: Binder layer
60: Support frame
80: Pellicle
90: Reticle
92: Mask substrate
93; EUV reflective mirror layer composed of 80 Si/Mo layers
94: Mask Pattern

Claims (20)

In a pellicle for EUV (Extreme Ultraviolet) exposure, the pellicle comprises a pellicle film that transmits EUV extreme ultraviolet rays and a support frame that supports the pellicle film,
The above pellicle film has a multilayer thin film structure in which a crystalline silicon (c-Si) layer without grain boundaries and a graphene thin film are hetero-bonded,
The above crystalline silicon (c-Si) layer is a pellicle for EUV exposure, which is formed by crystallizing an amorphous silicon thin film by heating with electron beam irradiation and has crystal peaks at (111), (220), and (311) in an XRD (X-ray diffraction) spectrum. delete In the first paragraph,
A pellicle for EUV exposure, wherein the above pellicle film is any one of c-Si/graphene, graphene/c-Si, c-Si/SiC/graphene, graphene/SiC/c-Si, c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene structures. In the first paragraph,
The above pellicle film is a pellicle for EUV exposure, having a thickness of 5 to 50 nm. To manufacture an exposure pellicle including a pellicle film that transmits EUV (Extreme Ultraviolet) and a support frame that supports the pellicle film,
(S1) A step of forming a multilayer film including a carbon layer, a metal catalyst layer, and an amorphous silicon layer on a substrate;
(S2) A step in which the amorphous silicon layer on the surface is heated by irradiating an electron beam, and as this heat diffuses downward, the amorphous silicon layer is crystallized into a c-Si layer, the carbon in the carbon layer passes through the metal catalyst layer and diffuses to the c-Si/metal catalyst layer interface, and the carbon that has risen thereafter forms graphene at the interface, all of which are performed simultaneously or sequentially to ultimately form a multilayer thin film in which the c-Si layer and the graphene layer are hetero-bonded;
(S3) A step of forming a binder layer on the outer surface of the multilayer film and also forming a binder layer on the facing surface of the support frame, and then performing diffusion bonding through the binder layer by bringing the support frame into contact with the binder layer on the outer surface of the multilayer film; and
(S4) A method for manufacturing a pellicle for EUV exposure, comprising the step of lifting off a multilayer thin film attached to a frame from the substrate. In paragraph 5,
After step (S4),
(S5) A step of forming at least one of an amorphous silicon layer and a carbon layer on the bottom surface opposite the frame of the frame-attached multilayer thin film; and
(S6) A method for manufacturing a pellicle for EUV exposure, further comprising performing a step of forming at least one of a c-Si layer and a graphene layer by irradiating an electron beam on a bottom surface. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, further comprising performing a step of etching a metal catalyst layer between (S4) and (S5). In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the pellicle has any one of the structures c-Si/graphene, graphene/c-Si, c-Si/SiC/graphene, and graphene/SiC/c-Si. In any one of paragraphs 5 and 6,
A method for manufacturing a pellicle for EUV exposure, wherein the pellicle has any one of the structures c-Si/graphene/c-Si, graphene/c-Si/graphene, c-Si/SiC/graphene/SiC/c-Si, and graphene/SiC/c-Si/SiC/graphene. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the multilayer film is one type of multilayer film selected from the group consisting of amorphous silicon layer/metal catalyst layer/carbon layer, amorphous silicon layer/carbon layer/metal catalyst layer, carbon layer/metal catalyst layer/amorphous silicon layer, carbon layer/amorphous silicon layer/metal catalyst layer, metal catalyst layer/carbon layer/amorphous silicon layer, and metal catalyst layer/amorphous silicon layer/carbon layer. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the metal catalyst layer is made of a single metal or two or more alloy thin films selected from the group consisting of Ni, Ti, Al, Zn, Co, Cu, Pt, Ag and Au having an FCC (Face Centered Cubic lattice) structure. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the carbon layer is formed by coating a graphene precursor solution and then curing the graphene cured film; or by any one of chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), sputtering, graphite ion beam deposition (IBD), physical vapor deposition, and vacuum deposition. In paragraph 12,
A method for manufacturing a pellicle for EUV exposure, comprising a process in which a carbon source in the above sputtering, graphite ion beam deposition (IBD), physical vapor deposition, and vacuum deposition methods is used alone or by adding hydrocarbon gas. In paragraph 12,
A method for manufacturing a pellicle for EUV exposure, wherein the graphene precursor is one selected from the group consisting of polyimide, polyacrylonitrile, polymethyl methacrylate, polystyrene, rayon, lignin, pitch, borazine oligomer, and combinations thereof. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the electron beam uses one electron beam source or multiple electron beam sources, the electron beam sources are arranged in series or parallel, and a circular or linear beam is used to uniformly process the electron beam across the entire surface of the pellicle. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the electron beam is applied at a voltage of 50 eV to 50 keV. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the binder layer comprises a multilayer film comprising at least one selected from a low-temperature melting metal; an eutectic alloy having a lower melting temperature when any one of Zn, Ga, In, Sn, or Au and any one of Al, Si, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Te, Ru, Pd, Ag, or Pt is alloyed together; a general alloy; and an oxide, nitride, carbide, or boride thereof. In paragraph 5,
A method for manufacturing a pellicle for EUV exposure, wherein the above binder layer diffusion bonding is performed by applying a pressure of 0.1 MPa to 1.0 MPa at a temperature of 300°C to 600°C. In paragraph 5,
The above lift-off is a pretreatment process, and a method for manufacturing a pellicle for EUV exposure, in which a hydrophobic plasma treatment is performed on various metal or ceramic, quartz plate substrates, a plasma implantation treatment is performed on Si wafers, a spacing layer of any one of CuN, CuO, and Si:H is deposited on these substrates, and after pretreatment by one or a combination of one or more of these methods, heat is supplied to the substrate so that hydrogen, helium, nitrogen, and oxygen gases are ejected from the compound constituting the interface between the substrate and the multilayer thin film or the spacing layer, thereby separating the interface between the substrate and the multilayer thin film. Photomask; and
A reticle for EUV exposure, comprising a pellicle according to claim 1, to protect the above photomask from dust.