Mask for projection lithography, and mask preparation method

Abstract

A mask for projection lithography, and a mask preparation method. The mask preparation method comprises: forming, by means of transfer printing, direct printing or coating, a patterned nanoparticle thin film or microparticle thin film on the surface of a resist thin film covering a substrate for projection lithography; and using the patterned nanoparticle thin film or microparticle thin film as a mask to block the resist thin film below the mask from being exposed during the process of projection lithography.

Description

A mask for projection lithography and a method for mask fabrication.

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. CN 202510124511.2, filed on January 26, 2025, entitled "A mask for projection lithography and a method for preparing the mask", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of micro-nano fabrication technology, and in particular to a mask and mask preparation method for projection lithography. Background Technology

[0004] Photolithography masks are an indispensable tool in semiconductor manufacturing. They serve as a medium for defining lithographic patterns, selectively allowing light, electrons, and other substances to pass through and interact with the resist. The minimum size, area, and uniformity of the mask pattern directly determine the performance of devices and chips.

[0005] Traditional mask fabrication methods involve processing intricate patterns onto a thin masking layer using techniques such as laser direct writing, electron beam lithography, projection lithography, and nanoimprinting. High-transmittance materials like quartz or optical glass serve as the mask substrate, providing support. However, while laser direct writing and electron beam lithography can achieve nanometer-level pattern resolution, the patterning rate is extremely slow. For example, writing a high-precision mask (10nm resolution) on an eight-inch wafer typically takes over 100 hours, with low yield. This extremely slow writing speed significantly increases R&D costs and hinders product development and iteration, limiting its application to small-scale production. Projection lithography, by scaling and projecting the pattern from a single mask onto a new one, is suitable for high-volume mask fabrication with high reproducibility. While it significantly increases fabrication speed, its resolution is limited by the diffraction limit of the optical system, typically used for micrometer-level mask fabrication, and insufficient for more advanced manufacturing requirements. Nanoimprinting, which directly imprints desired patterns onto a mold substrate, offers high resolution and low cost. However, the mold fabrication process is complex, requires high-quality substrate surface treatment, and is prone to introducing defects. Furthermore, photomasks, as consumables, are easily damaged and contaminated during contact or proximity lithography, limiting their reusability. While projection lithography effectively reduces mask damage, its structure can still be damaged during handling, resulting in a limited lifespan and increased industrial production costs.

[0006] Furthermore, the masks fabricated using electron beam lithography and laser direct writing methods typically only meet the requirements of ultraviolet and extreme ultraviolet lithography, and cannot meet the mask requirements of electron beam lithography. Because electron beams have low penetration capabilities into hard masks, the mask thickness must be extremely thin (~100nm), and the pattern size must also be very small (~100nm), resulting in high fabrication difficulty and cost. Secondly, ultrathin masks are easily deformed under high-energy electron beam bombardment, making them difficult to reuse multiple times, which increases costs and affects lithography accuracy.

[0007] Another existing mask fabrication technique is nanosphere lithography. This technique uses patterned silica or polystyrene microspheres on the surface of a resist as patterned microlenses. Light is coupled into these microlenses and focused beneath them, forming a focal point with a strong local light intensity distribution. This focusing effect concentrates the light beam to a nanometer scale, thus significantly exposing the area beneath the microspheres and forming the corresponding pattern. For example, when using silica microspheres as microlens masks, a self-assembly method can be used to fabricate closely packed silica microspheres, which are then transferred onto the resist to form a microlens array. While nanosphere lithography saves on mask fabrication costs and time and promises to rapidly fabricate large-area lithographic masks, using microspheres as microlenses requires a specific diameter and wavelength matching; that is, the silica microspheres need to be of a specific size to couple with the light. Furthermore, using these microlenses as a patterning medium cannot achieve arbitrary pattern shapes. The lithographic patterns are typically special shapes such as dots, rings, circles, and ellipses, thus making them unsuitable as masks for general-purpose pattern lithography. On the other hand, the resolution of the optical focal point is usually limited by the diffraction limit, resulting in limited accuracy of the exposed pattern. Furthermore, the light coupled through microlenses exhibits a continuous energy distribution on the resist, and the boundary of the lithographic region depends on the light intensity threshold, often leading to insufficiently sharp boundaries. These drawbacks make this method difficult to apply to general industrial patterning processes.

[0008] As mentioned above, electron beam lithography and laser direct writing techniques for fabricating photomasks suffer from low throughput and high cost. Furthermore, nanosphere lithography, which uses self-assembled and transferred silica or polystyrene particles as microlens systems as masks, cannot fabricate universal patterns and produces blurred boundaries. In addition, existing photomask fabrication processes are generally only applicable to ultraviolet and extreme ultraviolet lithography applications and cannot be used in electron beam lithography.

[0009] Current projection electron beam lithography techniques all employ microfabricated hard masks with patterned regions exhibiting varying electron beam transmittance. Due to the low penetration capability of electron beams through hard masks, existing projection electron beam lithography techniques suffer from several common drawbacks. First, because of this low penetration capability, the mask thickness must be extremely thin, and the pattern size must be very small, resulting in high fabrication difficulty and cost. Second, ultrathin masks are easily deformed under high-energy electron beam bombardment, making them unsuitable for repeated use, which increases cost and affects lithography accuracy.

[0010] Therefore, how to design a mask fabrication method that can achieve large area, high precision, and high efficiency, as well as a mask that can specifically transmit ultraviolet light, extreme ultraviolet light, or electrons, is a technical problem that urgently needs to be solved. Summary of the Invention

[0011] In view of this, embodiments of this application provide a mask and a mask preparation method for projection lithography to eliminate or improve one or more defects existing in the prior art.

[0012] One aspect of this disclosure provides a method for preparing a mask for projection lithography, the method comprising the following steps: forming a patterned nanoparticle film or micron particle film on the surface of a resist film covering a substrate for projection lithography by means of transfer imprinting, direct printing or deposition; and using the patterned nanoparticle film or micron particle film as a mask to prevent the resist film below the mask from being exposed during the projection lithography process.

[0013] In some embodiments of this disclosure, patterned nanoparticle films or microparticle films are formed on the surface of a resist film by transfer imprinting, including: forming a nanoparticle film on the surface of a nanoparticle solution by self-assembly, or forming a microparticle film on the surface of a microparticle solution; contacting the raised pattern surface of a pre-prepared flexible template with the self-assembled nanoparticle film or microparticle film to form a layer of nanoparticle film or microparticle film on the raised pattern surface of the flexible template; contacting the raised pattern surface of the flexible template with the nanoparticle film or microparticle film to the surface of the resist film covering the substrate and applying pressure, so that the nanoparticle film or microparticle film on the raised pattern surface of the flexible template is transferred to the surface of the resist film.

[0014] In some embodiments of this disclosure, the material of the raised pattern portion of the soft template is selected from polydimethylsiloxane (PDMS), polymethyl methacrylate, and polyvinyl alcohol.

[0015] In some embodiments of this disclosure, the method further includes the step of pre-preparing a soft template with raised patterns, comprising: patterning the surface of a substrate with raised and recessed areas; performing silanization treatment on the substrate to passivate the surface; uniformly mixing the soft template material with a curing agent; pouring the mixture of the soft template material and the curing agent onto the treated substrate, uniformly spin-coating and placing it for curing, and demolding after curing to obtain the soft template with raised patterns.

[0016] In some embodiments of this disclosure, the patterning of the substrate surface includes: forming a predetermined pattern of resist on the substrate surface using a patterning mask via ultraviolet lithography to form a resist mask; and etching the substrate surface with the patterned resist mask using reactive ion etching to transfer a pattern identical or complementary to the resist pattern onto the substrate, thereby patterning the substrate surface; or

[0017] The process of patterning the substrate surface includes: obtaining a preset pattern on an electron beam resist film on the substrate surface by electron beam lithography to form a resist mask; and etching the substrate surface with the patterned resist mask by reactive ion etching to transfer a pattern that is the same as or complementary to the resist pattern onto the substrate, thereby patterning the substrate surface.

[0018] In some embodiments of this disclosure, the substrate is a non-planar substrate, and the resist film covering the substrate is a non-planar resist film. Contacting the surface of the flexible template with the raised pattern of nanoparticle or microparticle film with the surface of the resist film covering the substrate and applying pressure to transfer the nanoparticle or microparticle film from the raised pattern surface of the flexible template to the surface of the resist film includes: manipulating the surface of the flexible template with the raised pattern of nanoparticle or microparticle film to conformally contact the surface of the non-planar resist film covering the non-planar substrate, so that the pattern on the flexible template is conformally transferred to the non-planar substrate, forming a patterned nanoparticle or microparticle film on the surface of the resist film; the non-planar substrate is a non-planar substrate comprising one or more structures including protrusions, depressions, sidewalls, ramps, bends, and steps.

[0019] In some embodiments of this disclosure, a patterned nanoparticle film or micron particle film is coated on the surface of a resist film by direct printing, including: using 3D printing, inkjet printing or screen printing to directly additively print a patterned film composed of nanoparticles or micron particles on the surface of the resist film according to a preset drawing.

[0020] In some embodiments of this disclosure, the materials used for 3D printing, inkjet printing, or screen printing are metallic or inorganic non-metallic materials. The types of metallic materials include stainless steel, aluminum alloy, titanium alloy, and copper, while the types of inorganic non-metallic materials include ceramics and gypsum.

[0021] In some embodiments of this disclosure, patterned nanoparticle films or microparticle films are coated on the surface of a resist film by means of coating, including: attaching a hollowed-out patterned template tightly to the surface of the resist film; coating nanoparticles or microparticles using electron beam evaporation coating, thermal evaporation coating, magnetron sputtering coating, chemical vapor deposition or atomic layer deposition, using the coating of the hollowed-out area as a mask.

[0022] In some embodiments of this disclosure, the energy form used for projection lithography may be ultraviolet light, electrons, or X-rays.

[0023] In some embodiments of this disclosure, the patterned nanoparticle film or microparticle film covering the surface of the resist film has one or more layers, and the multilayer nanoparticle film or microparticle film is obtained by performing multiple transfer imprints.

[0024] In some embodiments of this disclosure, the material of the nanoparticle film or the microparticle film is a metal or a non-metal, the metal including gold and silver, and the non-metal including silicon dioxide, titanium dioxide, aluminum oxide and zinc oxide.

[0025] In some embodiments of this disclosure, the shapes of the nanoparticles or microparticles include: nanospheres, nanostars, nanocubes, nanosheets, nanocages, nanopolyhedra, and nanorods.

[0026] Corresponding to the above methods, this disclosure also provides a mask for projection lithography, prepared according to any of the methods described in the above embodiments, and covering the surface of a resist film.

[0027] The mask and mask preparation method for projection lithography disclosed herein can cover patterned nanoparticle thin films or micron particle thin films by transfer imprinting, direct printing or coating. The patterned nanoparticle thin film or micron particle thin film serves as a mask to prevent the resist film under the mask from being exposed during the projection lithography process. It can achieve large-area, high-precision and high-efficiency mask preparation. The mask prepared by this method can specifically transmit or block ultraviolet light, extreme ultraviolet light, X-rays or electrons.

[0028] Additional advantages, objects, and features of this disclosure will be set forth in part in the description which follows, and will in part become apparent to those skilled in the art upon studying the following text, or may be learned by practice of this disclosure. The objects and other advantages of this disclosure may be realized and obtained by means of the structures specifically pointed out in the specification and the accompanying drawings.

[0029] Those skilled in the art will understand that the purposes and advantages achievable with this disclosure are not limited to those specifically described above, and that the above and other purposes achievable with this disclosure will become clearer from the following detailed description. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this disclosure, do not constitute a limitation thereof. The components in the drawings are not drawn to scale but are merely for illustrating the principles of this application. For ease of illustration and description of certain parts of this application, corresponding portions in the drawings may be enlarged, i.e., may appear larger relative to other components in an exemplary device actually manufactured according to this application. In the drawings:

[0031] Figure 1 is a schematic diagram of a mask preparation method for projection lithography in one embodiment of this disclosure.

[0032] Figure 2 is a flowchart of the self-assembly transfer imprinting preparation of gold nanoparticle thin films in one embodiment of this disclosure.

[0033] Figure 3 is a flowchart of a contact mask preparation method for coating in one embodiment of this disclosure.

[0034] Figure 4 illustrates a mask fabrication method on a non-planar substrate according to an embodiment of this disclosure.

[0035] Figure 5 illustrates the preparation process of a soft template in one embodiment of this disclosure. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions herein are used to explain this disclosure, but are not intended to limit it.

[0037] It should also be noted that, in order to avoid obscuring this disclosure with unnecessary details, only the structures and / or processing steps closely related to the scheme according to this disclosure are shown in the accompanying drawings, while other details that are not closely related to this disclosure are omitted.

[0038] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0039] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0040] In the following description, embodiments of the present disclosure will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0041] Figure 1 is a schematic diagram of a mask fabrication method for projection lithography according to an embodiment of this disclosure. The mask fabrication method for projection lithography includes the following steps: A patterned nanoparticle film or micron-particle film is coated onto the surface of a resist film covering a substrate for projection lithography by means of transfer imprinting, direct printing, or deposition. The patterned nanoparticle film or micron-particle film serves as a mask to prevent the resist film beneath the mask from being exposed during the projection lithography process. The resist can be a photoresist (i.e., photoresist) or an electron beam resist.

[0042] In specific implementations, the substrate can be one or more materials selected from silicon, silicon dioxide, silicon nitride, glass substrate, alumina, gallium nitride, polyvinyl alcohol, polycarbonate, polyethylene terephthalate, and polyimide. The substrate material used in this example is merely illustrative, and this disclosure is not limited thereto. The substrate can be a rigid substrate or a flexible substrate. The photoresist can be a photoresist such as ultraviolet light photoresist, extreme ultraviolet light photoresist, or X-ray photoresist, or an electron beam photoresist. These photoresists are merely examples, and this disclosure is not limited thereto. Furthermore, the photoresist can be a positive or negative photoresist. After exposure, the patterned nanoparticle film or micron-particle film can be removed by solution cleaning using a specific etching solution, and the etching solution will not dissolve the photoresist.

[0043] The mask fabrication method for projection lithography disclosed herein can form patterned nanoparticle or micron-sized particle films on the surface of a resist film on a substrate through transfer imprinting, direct printing, or deposition, enabling large-area, high-precision, and high-efficiency mask fabrication. The fabricated patterned nanoparticle or micron-sized particle films, as masks, can prevent the resist film beneath the mask from being exposed during projection lithography. Masks prepared by this method can specifically transmit or block ultraviolet light, extreme ultraviolet light, X-rays, or electrons. Masks prepared by this method can be directly placed on the resist surface of the substrate, directly contacting the resist film, and can completely or partially block electron beams, ultraviolet light, extreme ultraviolet light, or X-rays. The difference in exposure between the covered and uncovered areas of the mask forms the lithographic pattern.

[0044] In some embodiments of this disclosure, patterned nanoparticle films or micron-sized particle films are coated onto the surface of a resist film by transfer imprinting, including: (1) forming a nanoparticle film on the surface of a nanoparticle solution or a micron-sized particle film on the surface of a micron-sized particle solution by self-assembly; (2) contacting the raised pattern surface of a pre-prepared flexible template with the self-assembled nanoparticle film or micron-sized particle film to form a layer of nanoparticle film or micron-sized particle film on the raised pattern surface of the flexible template; (3) contacting the raised pattern surface of the flexible template with the surface of the resist film and applying pressure so that the nanoparticle film or micron-sized particle film on the raised pattern surface of the flexible template covers the surface of the resist film. Wherein, the bonding force between the nanoparticle film or micron-sized particle film and the raised pattern portion of the flexible template is greater than its bonding force with the solution, and the bonding force between the nanoparticle film or micron-sized particle film and the raised pattern material of the flexible template is less than its bonding force with the resist film.

[0045] This embodiment enables the deposition of patterned nanoparticle or micron-sized particle films onto the surface of a resist film via self-assembly transfer imprinting for high-throughput projection lithography. The patterned soft stencil (or stamp) used in the transfer imprinting process is replicated from a hard mask with a complementary structure.

[0046] In some embodiments of this disclosure, the material for the raised pattern portion of the soft template can be selected from organic polymers such as polydimethylsiloxane (PDMS), polymethyl methacrylate, and polyvinyl alcohol. The types of materials used for the raised pattern portion of the soft template in this disclosure are not limited to these; the above are merely examples.

[0047] This embodiment enables the fabrication of raised patterns on transfer embossing soft stencils using a variety of materials.

[0048] In some embodiments of this disclosure, the method further includes the step of pre-preparing a flexible template with raised patterns, comprising: patterning the surface of a substrate with raised and recessed areas; performing a silanization treatment on the substrate to passivate the surface; uniformly mixing the flexible template material with a curing agent; pouring the mixture of the flexible template material and the curing agent onto the passivated substrate, uniformly spin-coating and placing it on a curing plate; and demolding after curing to obtain a flexible template with raised patterns. The substrate may be a silicon substrate, but it may also be other rigid substrates, such as glass, quartz, or sapphire substrates, etc., and this disclosure is not limited thereto.

[0049] In this embodiment of the disclosure, there are many ways to pattern the surface of the substrate. For example, taking a silicon substrate as an example, the surface of the silicon substrate can be patterned with uneven surfaces in the following ways:

[0050] Ultraviolet lithography is used to form a predetermined pattern of the resist on the surface of a silicon substrate using a patterned mask; that is, the resist on the surface of the silicon substrate is patterned to form a resist mask; and

[0051] The silicon substrate surface is patterned by etching a patterned resist mask using reactive ion etching, transferring a pattern that is the same as or complementary to the resist pattern onto the silicon substrate.

[0052] Alternatively, the surface of the silicon substrate can be patterned with bumps and depressions in the following ways:

[0053] A predetermined pattern is obtained on an electron beam resist film on a silicon substrate surface using electron beam lithography; that is, the resist on the silicon substrate surface is patterned to form a resist mask.

[0054] The silicon substrate surface is patterned by etching a patterned resist mask using reactive ion etching, transferring a pattern that is the same as or complementary to the resist pattern onto the silicon substrate.

[0055] In this embodiment of the disclosure, the purpose of silanizing the substrate to passivate the surface is to construct a series of dense, low surface energy, chemically inert organic-inorganic hybrid films on the substrate surface to facilitate the demolding of the soft mold.

[0056] The above steps enable the pre-preparation of soft templates with raised patterns.

[0057] Figure 2 is a flowchart illustrating the self-assembled transfer imprinting method for preparing gold nanoparticle thin films according to an embodiment of this disclosure. As shown in Figure 2, the method for preparing a metal nanoparticle thin film mask using self-assembled transfer imprinting includes:

[0058] (1) Self-assembly to obtain a close-packed gold nanoparticle film.

[0059] A solution of gold nanoparticles modified with ctab ligands and dispersed in ultrapure water of a certain concentration and diameter is added to a container. The gold nanoparticle solution consists of gold nanoparticles modified with ctab ligands of a certain concentration and diameter (or a certain diameter range) uniformly dispersed in the solvent. Here, the certain concentration can be a concentration value in the range of 0.1 mM to 50 mM, and the certain diameter is, for example, a diameter value in the range of 1 nm to 1000 nm or a smaller diameter range, which can be determined based on the thickness parameters of the particle film to be prepared. A perfluorinated surfactant (PFT) solution, which is a mixture of ethanol, n-hexane, and 1H,1H,2H,2H-perfluorododecanethiol in a certain proportion, is added to the container to induce the gold nanoparticles to self-assemble at the interface between the upper and lower layers of n-hexane and ethanol to form a close-packed gold nanoparticle film. After the upper layer of n-hexane evaporates, a monolayer of close-packed gold nanoparticle film can be obtained on the ethanol surface. Here, the composition of gold nanoparticles and perfluorinated surfactant is only for example. Through similar self-assembly methods, nano or micron particle films of different thicknesses and materials can also be obtained.

[0060] (2) Prepare a graphical PDMS soft template (or stamp).

[0061] The soft template is fabricated using a hard-film casting and demolding method. The preparation process is shown in Figure 5, which illustrates the soft template preparation process in one embodiment of this disclosure. First, a patterned resist mask is prepared on a silicon substrate using ultraviolet lithography or electron beam lithography. The pattern of the mask is then transferred to the silicon substrate using reactive ion etching. Next, the silicon substrate is silanized to passivate the surface and prevent PDMS from adhering to the mold during subsequent demolding. PDMS and a curing agent are mixed at 2000 rpm for one minute in a stirring or mixing device, followed by defoaming at 2200 rpm for two minutes to achieve uniform mixing of the soft template material and the curing agent. The uniformly mixed, bubble-free PDMS mixture is then poured onto the patterned silicon substrate, spin-coated evenly, and left to stand under atmospheric pressure for 15 minutes to ensure uniform edge thickness. The substrate is then left to cure for 24 hours at room temperature or 2 hours at 80°C. After curing, the patterned PDMS soft template is obtained by demolding. The process parameters given here are merely examples, and this disclosure is not limited to them; rather, the process parameters can be reasonably adjusted.

[0062] (3) Transfer the nanoparticle film onto a graphic PDMS soft template.

[0063] A single layer of closely packed gold nanoparticle film is formed by self-assembling on the surface of ethanol with one side of a PDMS soft template containing a patterned protrusion structure. Since the bonding force between the gold nanoparticle film and the PDMS soft template is greater than that with the solution, the nanoparticle film is transferred onto the PDMS soft template, forming a layer of gold nanoparticle film on the surface of the PDMS soft template.

[0064] (4) Transfer the nanoparticle film to the surface of the electron beam resist.

[0065] A PDMS flexible stencil is manipulated so that one side containing the gold nanoparticle film contacts a resist film covering the substrate surface, and appropriate pressure is applied. Because the patterned structure on the PDMS flexible stencil surface is raised compared to other parts, only the gold nanoparticle film on the patterned raised surface contacts the resist film. Since the adhesion between the gold nanoparticle film and the resist film is greater than its adhesion to the PDMS flexible stencil, the gold nanoparticle film on the patterned raised surface transfers to the resist film surface. The remaining gold nanoparticle film on the PDMS flexible stencil remains on the PDMS flexible stencil, thus obtaining a patterned gold nanoparticle film on the resist surface. In this embodiment, the pressure applied to the resist film is preferably sufficient to transfer the gold nanoparticle film to the resist film on the substrate surface without damaging the gold nanoparticle film and the resist film.

[0066] Steps (3) and (4) are transfer imprinting steps. Compared to existing technologies, this transfer imprinting method directly transfers the patterned gold nanoparticle film onto the resist. Since the resist is usually a viscoelastic material with a low Young's modulus, it will deform under external pressure, which helps to increase the contact area between the gold nanoparticles and the resist, thereby improving the transfer efficiency. Similarly, patterned gold micron-sized particle films can also be directly transferred onto the resist, as can patterned micron-sized or nanon-sized particle films of other materials.

[0067] In some embodiments of this disclosure, since the mask is a nanoparticle thin film or a microparticle thin film, it can be tightly bonded to a non-planar substrate and has good contact conformality. Therefore, this disclosure can also realize masking and exposure of non-planar substrates. A non-planar substrate is a substrate whose surface is not planar, such as a non-planar substrate containing one or more structures including protrusions, depressions, sidewalls, slopes, bends, and steps. In contrast, conventional methods are difficult to achieve exposure on non-planar or insulating substrates. This disclosure overcomes this deficiency of conventional technology and has significant progress.

[0068] Furthermore, in one embodiment of this disclosure, coating a patterned nanoparticle film or microparticle film onto the surface of a resist film above a non-planar substrate by transfer imprinting includes: manipulating a pre-prepared soft template to conformally contact the non-planar substrate, so that the pattern on the soft template is conformally transferred to the non-planar substrate, forming a patterned nanoparticle film or microparticle film located on the surface of the resist film.

[0069] Figure 4 illustrates a mask fabrication method on a non-planar substrate according to an embodiment of this disclosure. As shown in Figure 4, the patterned transfer of the non-planar substrate can be achieved through a transfer imprinting method. First, a monolayer close-packed gold nanoparticle film is formed through a self-assembly process, and the nanoparticles are transferred onto a patterned PDMS soft template. Since the bonding force between the gold nanoparticles and the PDMS film is greater than the bonding force between the gold nanoparticles and the ethanol interface, the close-packed monolayer gold nanoparticle film is transferred onto the PDMS soft template. During the mask fabrication process on the non-planar substrate, the non-planar substrate with photoresist can be placed on a hot stage, and the PDMS template is manipulated to contact the substrate. Since PDMS has a relatively small Young's modulus (approximately 400 MPa), it can achieve good conformal contact with the non-planar substrate, allowing the pattern on the PDMS soft template to be conformally transferred onto the non-planar substrate, forming a patterned gold nanoparticle array pattern.

[0070] This embodiment enables the formation of patterned nanoparticle or micron-sized particle films on the surface of a resist film on a non-planar substrate, greatly expanding the application scenarios and applicable range of projection lithography.

[0071] In some embodiments of this disclosure, a patterned nanoparticle film or micron particle film is coated on the surface of a resist film by direct printing, including: directly additively printing a patterned film composed of nanoparticles or micron particles onto the surface of the resist film according to a preset drawing using 3D printing, inkjet printing or screen printing.

[0072] The materials used in 3D printing, inkjet printing, or screen printing are either metallic or inorganic non-metallic materials. Examples of metallic materials include stainless steel, aluminum alloys, titanium alloys, and copper, while examples of inorganic non-metallic materials include ceramics and gypsum. During the printing process, the design is first drawn using CAD software. Then, the drawing is imported and a mask, acting as a barrier layer, is directly printed onto the resist surface using additive manufacturing. Subsequently, the nanoparticle or micron-sized particle film can be specifically removed using solution cleaning.

[0073] Using this embodiment, nanoparticle thin films or micron-particle thin films can be fabricated through various direct printing methods. A patterned mask can be directly printed on the substrate and the resist using 3D printing, inkjet printing, or screen printing.

[0074] In some embodiments of this disclosure, a patterned nanoparticle film or micron-particle film is coated onto the surface of a resist film by means of a coating process, including: (1) pre-processing a hollowed-out patterned template; (2) attaching the patterned template tightly to the surface of the resist film; and (3) coating the nanoparticles or micron-particles using electron beam evaporation coating, thermal evaporation coating, magnetron sputtering coating, chemical vapor deposition, or atomic layer deposition, using the coating of the hollowed-out area as a mask. In specific implementations, the thickness of the coating can be 20-200 nm.

[0075] This embodiment demonstrates that nanoparticle thin films or micron-particle thin films can be prepared by coating.

[0076] Figure 3 is a flowchart of a contact mask fabrication method for film deposition in one embodiment of this disclosure. As shown in Figure 3, fabricating a mask using film deposition requires first preparing a hollowed-out patterned template. The patterned template can be fabricated using 3D printing, dry etching, wet etching, etc. A layer of electron beam resist, ultraviolet resist, extreme ultraviolet resist, or X-ray resist is uniformly spin-coated onto the substrate. The hollowed-out patterned template is then tightly attached to the resist. Film deposition is performed using electron beam evaporation, thermal evaporation, magnetron sputtering, chemical vapor deposition, or atomic layer deposition techniques, with a film thickness of 20-200 nm. The metal in the hollowed-out pattern area can be directly deposited onto the resist, while the metal film in the remaining areas is directly deposited onto the template and serves as a mask for subsequent photolithography. After a period of exposure to electron beam / ultraviolet / extreme ultraviolet / X-ray light, the metal interacts with the resist, ensuring sufficient photolithography. The mask is removed by etching with a solution, the pattern is transferred to the resist by the developer, and then the developer is removed by the fixer to prevent overdevelopment.

[0077] In some embodiments of this disclosure, the energy form used for projection lithography can be ultraviolet light, extreme ultraviolet light, electron beam, or X-rays, and the resist film area shielded by the patterned nanoparticle film or micron particle film will not or will be exposed to ultraviolet light, extreme ultraviolet light, electron beam, or X-rays.

[0078] In some embodiments of this disclosure, the patterned nanoparticle film or micron-particle film covering the surface of the resist film has one or more layers. When the nanoparticle film or micron-particle film is multilayered, this multilayered nanoparticle film or micron-particle film can be achieved by performing multiple transfer imprints.

[0079] In some embodiments of this disclosure, the material type of the nanoparticle film or microparticle film is metal or non-metal, the metals include gold and silver, and the non-metals include silicon dioxide, titanium dioxide, aluminum oxide and zinc oxide.

[0080] In some embodiments of this disclosure, the types of nanoparticles or microparticles classified according to their structural characteristics include: nanospheres, nanostars, nanocubes, nanosheets, nanocages, nanopolyhedra, and nanorods.

[0081] Corresponding to the above method, this disclosure also provides a mask for projection lithography, which is prepared as described in the above embodiments and covers the surface of a resist film.

[0082] The mask and mask preparation method for projection lithography proposed in this disclosure can cover patterned nanoparticle thin films or micron particle thin films by transfer imprinting, direct printing or coating. The patterned nanoparticle thin film or micron particle thin film serves as a mask to prevent the resist film under the mask from being exposed during the projection lithography process. This method enables large-area, high-precision and high-efficiency mask preparation. The mask prepared by this method can specifically allow or block ultraviolet light, extreme ultraviolet light, X-rays or electrons.

[0083] Compared to existing technologies, the advantages of this solution are mainly reflected in:

[0084] (1) Compared to existing mask fabrication methods that mostly employ laser direct writing, the method proposed in this disclosure directly fabricates disposable nanoparticle or microparticle masks on the resist. In particular, the patterned mask achieved through self-assembly transfer imprinting allows for direct cleaning of the nanoparticles or microparticles after photolithography, and the cleaned particles can be reused in subsequent self-assembly processes. The mask in this disclosure is in direct contact with the resist, which not only improves the resolution during photolithography but also avoids the introduction of a projection system in the photolithography system, reducing equipment complexity. Compared to hard masks fabricated through micromachining, it has the advantages of easy fabrication and low cost.

[0085] (2) Compared with the process of using transferred nanoparticles as a microlens system for patterning in nanosphere photolithography, the mask preparation method proposed in this disclosure produces a mask that directly blocks the image, can process arbitrary shapes and patterns, can form clear boundaries, has no special requirements on the diameter of the nanospheres, and the patterned area of ​​the mask can reach the inch level.

[0086] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this disclosure. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this disclosure are programs or code segments used to perform the desired tasks. The programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave.

[0087] It should be clarified that this disclosure is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of this disclosure is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of this disclosure.

[0088] In this disclosure, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0089] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to the embodiments of this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for preparing a mask for projection lithography, characterized in that, include: Patterned nanoparticle films or micron-sized particle films are formed on the surface of a resist film covering a substrate used for projection lithography by means of transfer imprinting, direct printing or deposition. The patterned nanoparticle film or micron-sized particle film is used as a mask to prevent the resist film under the mask from being exposed during the projection lithography process.

2. The method according to claim 1, characterized in that, Patterned nanoparticle or micron-sized particle films are formed on the surface of a resist film by transfer imprinting, including: Nanoparticle films are formed on the surface of nanoparticle solutions or microparticle films are formed on the surface of microparticle solutions through self-assembly. The raised pattern surface of a pre-prepared soft template is brought into contact with a self-assembled nanoparticle film or micron particle film to form a nanoparticle film or micron particle film on the raised pattern surface of the soft template. The surface of the flexible stencil with a raised pattern of nanoparticle or microparticle film is brought into contact with the surface of the resist film covering the substrate and pressure is applied to transfer the nanoparticle or microparticle film on the raised pattern surface of the flexible stencil to the surface of the resist film.

3. The method according to claim 2, characterized in that, The material of the raised pattern portion of the soft template is selected from polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and polyvinyl alcohol.

4. The method according to claim 2, characterized in that, The method further includes the step of pre-preparing a soft template with a raised pattern, including: Pattern the surface of the substrate with concave and convex shapes; The substrate is subjected to silanization to passivate the surface; Mix the soft template material and the curing agent evenly; The mixture of soft template material and curing agent is poured onto the treated substrate, evenly spin-coated and placed on the curing plate. After curing, the soft template with raised patterns is obtained by demolding.

5. The method according to claim 4, characterized in that, The process of patterning the surface of the substrate includes: A resist mask is formed by using ultraviolet lithography to create a predetermined pattern from the resist on the substrate surface using a patterned mask; and by using reactive ion etching to etch the substrate surface with the patterned resist mask, transferring a pattern that is the same as or complementary to the resist pattern onto the substrate, thereby patterning the substrate surface; or The process of patterning the surface of the substrate includes: A pre-defined pattern is obtained on an electron beam resist film on the substrate surface by electron beam lithography to form a resist mask; and the substrate surface with the patterned resist mask is etched by reactive ion etching to transfer a pattern that is the same as or complementary to the resist pattern onto the substrate, thereby patterning the substrate surface.

6. The method according to claim 2, characterized in that, The substrate is a non-planar substrate, and the resist film covering the substrate is also a non-planar resist film. The process of contacting the surface of the flexible stencil with the raised pattern of nanoparticle or microparticle films with the surface of the resist film covering the substrate and applying pressure to transfer the nanoparticle or microparticle film from the raised pattern surface of the flexible stencil to the surface of the resist film includes: manipulating the surface of the flexible stencil with the raised pattern of nanoparticle or microparticle films to conformally contact the surface of the non-planar resist film covering the substrate, so that the pattern on the flexible stencil is conformally transferred to the non-planar substrate, forming a patterned nanoparticle or microparticle film on the surface of the resist film; the non-planar substrate is a non-planar substrate containing one or more structures including protrusions, depressions, sidewalls, ramps, bends, and steps.

7. The method according to claim 1, characterized in that, Patterned nanoparticle or micron-particle films can be directly printed onto the surface of a resist film, including: A patterned film composed of nanoparticles or microparticles is additively printed directly onto the surface of a resist film according to a preset drawing using 3D printing, inkjet printing, or screen printing.

8. The method according to claim 7, characterized in that, The materials used in 3D printing, inkjet printing, or screen printing are either metallic or inorganic non-metallic. Metallic materials include stainless steel, aluminum alloys, titanium alloys, and copper, while inorganic non-metallic materials include ceramics and gypsum.

9. The method according to claim 1, characterized in that, Patterned nanoparticle or micron-particle films are deposited onto the surface of a resist film using a coating method, including: The perforated patterned template is attached tightly to the surface of the resist film; Nanoparticles or microparticles are deposited using electron beam evaporation, thermal evaporation, magnetron sputtering, chemical vapor deposition, or atomic layer deposition, with the deposited area in the hollow region serving as a mask.

10. The method according to claim 1, characterized in that, The energy form used for projection lithography can be ultraviolet light, extreme ultraviolet light, electron beam, or X-rays.

11. The method according to claim 2, characterized in that, The patterned nanoparticle film or microparticle film covering the surface of the resist film has one or more layers, and the multilayer nanoparticle film or microparticle film is obtained by performing multiple transfer imprints.

12. The method according to claim 1, characterized in that, The materials for nanoparticle films or microparticle films are metals or non-metals. Metals include gold and silver, and non-metals include silicon dioxide, titanium dioxide, aluminum oxide, and zinc oxide.

13. The method according to claim 1, characterized in that, The shapes of the nanoparticles or microparticles include: nanospheres, nanostars, nanocubes, nanosheets, nanocages, nanopolyhedra, and nanorods.

14. A mask for projection lithography, characterized in that, Prepared according to the method of any one of claims 1-13 and coated on the surface of the resist film.

Images