Projection electron beam lithography method and device

Abstract

The present disclosure provides a projection electron beam lithography method and a device. The method comprises: a preparation step, in which a surface of a substrate to be lithographed is covered with an electron beam resist film; a masking step, in which a patterned nanoparticle film partially covering the electron beam resist film is formed on a surface of the electron beam resist film to serve as a lithography mask; a lithography step, in which the substrate covered with the electron beam resist film and the nanoparticle film is placed on a travel path of an electron beam used for lithography, so that the electron beam exposes the electron beam resist film; a mask removal step, in which the nanoparticle film serving as the lithography mask is removed after exposure is completed; and a development step, in which the substrate still covered with the electron beam resist film is subjected to development processing, so as to form, on the substrate, a resist film pattern that is identical to or complementary to a pattern of the nanoparticle film.

Description

A projection electron beam lithography method and apparatus

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. CN 202510124512.7, filed on January 26, 2025, entitled “A Projection Electron Beam Lithography Method and Apparatus”, 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 projection electron beam lithography method and apparatus. Background Technology

[0004] Electron beam lithography (EBL) machines form micro-patterns through the interaction of high-energy electrons with a photoresist, making them crucial equipment for integrated circuit chip fabrication. Most commercial EBL machines are direct-write EBL machines, which accelerate electrons in a high-vacuum environment using a large accelerating voltage and focus them using an electromagnetic lens system to form a converging electron beam with an extremely small spot. Combined with back-end programming and a displacement stage, patterns are directly written at designated locations without the need for a photomask. However, writing can only be done by scanning the focused electron beam point by point (see US patent applications US5326979A and US5545902A). While this equipment can achieve nanometer-level patterning precision, it suffers from very low efficiency or throughput, typically requiring over ten hours to write patterns on a four-inch wafer, hindering its commercial application. It is usually only used for preparing high-precision lithographic masks. Although multi-electron-beam parallel direct-write EBL technology has been developed, the technology is still immature. The problems of high-quality generation and control of multi-electron beams have not been solved, and more importantly, its improvement in throughput is limited, failing to meet the commercial requirements for direct chip fabrication.

[0005] To improve throughput, another type of electron beam lithography technology has been developed—projection electron beam lithography (see Chinese patent applications CN1264850A and CN1193129A; US patent applications US4554458A and US4957835A). This technology projects a pattern on a photomask onto a large area using a large electron beam spot, transferring the pre-designed pattern from the photomask onto the resist. This allows for simultaneous lithography of a large area in a short time. The lithography accuracy of this approach depends on the minimum linewidth of the photomask and the intensity of electron scattering, while the throughput depends on the size and dose of the electron beam spot. Because it is currently difficult to achieve large-area, high-dose electron beams, the throughput of projection electron beam lithography is far from meeting commercial requirements. In addition, projection electron beam lithography faces challenges related to photomasks. On the one hand, because electron beams are easily scattered, the requirements for photomasks are extremely high. Typically, photomasks are required to have a hollow structure (see US patent applications US20020012852A1 and US20020066870A1), and their thickness is usually below 50 nm, resulting in high processing difficulty and cost. On the other hand, such thin photomasks are easily deformed under high-energy electron beam bombardment, thus altering the mask pattern and affecting lithography accuracy. Therefore, previous projection electron beam lithography technologies still face problems such as low processing throughput and high mask processing difficulty and susceptibility to deformation.

[0006] Furthermore, existing electron beam lithography technologies, whether direct-write or projection-based, require sophisticated electron optical systems and ultra-high vacuum systems. Direct-write electron beam lithography requires a sophisticated electron optical system to focus and deflect the electron beam to obtain a nanoscale focused electron beam. Projection-based electron beam lithography also requires a sophisticated electron optical system to obtain a large-area, uniformly intense parallel electron beam. Both high-quality focused electron beams and large-area parallel electron beams require ultra-high vacuum conditions. Both sophisticated electron optical systems and ultra-high vacuum systems are complex and expensive, making existing electron beam lithography machines very costly.

[0007] In addition, since existing electron beam lithography technology is carried out in a vacuum environment, the substrate is prone to charge accumulation. Therefore, it can generally only be used for conductive substrates and it is difficult to use for insulating substrates.

[0008] Furthermore, existing electron beam lithography technology requires a precision electron optical system to obtain a high-quality converged electron beam or a large-area parallel electron beam. Its lithography accuracy is greatly affected by aberrations such as spherical aberration, chromatic aberration, and astigmatism of the electron optical system. Therefore, it requires the working distance to be the same at all parts of the substrate, making it difficult to perform lithography on non-planar substrates.

[0009] Therefore, how to overcome the shortcomings of existing electron lithography technology is a technical problem that urgently needs to be solved. Summary of the Invention

[0010] In view of this, embodiments of the present disclosure provide a projection electron beam lithography method and apparatus to eliminate or improve one or more defects existing in the prior art.

[0011] One aspect of this disclosure provides a projection electron beam lithography method, the method comprising the following steps:

[0012] Preparation steps: An electron beam resist film is coated onto the surface of the substrate to be photolithographically lithographically prepared; Shaping steps: A patterned nanoparticle film partially covering the electron beam resist film is formed on the surface of the electron beam resist film to serve as a photolithography mask; Photolithography steps: The substrate covered with the electron beam resist film and the nanoparticle film is placed in the path of the electron beam used for photolithography, so that the electron beam exposes the electron beam resist film; Shaping removal steps: After exposure, the nanoparticle film serving as the photolithography mask is removed; Development steps: The substrate still covered with the electron beam resist film is developed to form a resist film pattern on the substrate that is the same as or complementary to the pattern of the nanoparticle film.

[0013] In some embodiments of this disclosure, after coating the substrate surface with an electron beam resist film, the method further includes: placing the substrate coated with the electron beam resist film on a heating stage and baking for a preset time.

[0014] In some embodiments of this disclosure, after the development step, the method further includes fixing the substrate still covered with an electron beam resist film.

[0015] In some embodiments of this disclosure, a patterned nanoparticle film partially covering the electron beam resist film is formed on the surface of the electron beam resist film, which may be one or more layers. The diameter of the nanoparticles ranges from 1 to 1000 nm, and the type of nanoparticles may be metallic nanoparticles or non-metallic nanoparticles.

[0016] In some embodiments of this disclosure, the molding step includes: a self-assembly step: forming a nanoparticle film on the surface of a nanoparticle solution through self-assembly; and a transfer imprinting step, which includes: contacting a pre-prepared stamp with raised patterns with the self-assembled nanoparticle film to form a nanoparticle film on the surface of the raised patterns of the stamp; and contacting the stamp with the nanoparticle film formed on the surface of the raised patterns with an electron beam resist film covering the substrate surface and applying pressure to transfer the nanoparticle film formed on the surface of the raised patterns of the stamp to the surface of the electron beam resist film; the transfer imprinting step is performed once or multiple times to achieve the formation of one or more patterned nanoparticle films partially covering the electron beam resist film on the surface of the electron beam resist film.

[0017] In some embodiments of this disclosure, the material of the raised graphic portion of the stamp is selected from: polydimethylsiloxane, polymethyl methacrylate, and polyvinyl alcohol.

[0018] In some embodiments of this disclosure, the material of the nanoparticle film is selected from gold, silver, silicon oxide, and polyethylene.

[0019] In some embodiments of this disclosure, the demolding step removes the nanoparticle film by solution washing.

[0020] In some embodiments of this disclosure, the method further includes the step of preparing an electron beam for photolithography, which includes: generating and accelerating an electron beam in a vacuum chamber, wherein the accelerated electron beam exits through a window on the wall of the vacuum chamber to the outside of the vacuum chamber, and the exited electron beam serves as the electron beam for photolithography.

[0021] In some embodiments of this disclosure, the environment outside the vacuum chamber where the substrate is located is a vacuum environment or an atmospheric environment. When the environment outside the vacuum chamber is an atmospheric environment, the emitted electron beam is scattered by air molecules into a diffuse electron beam, which serves as the electron beam for photolithography.

[0022] In some embodiments of this disclosure, the window on the wall of the vacuum chamber is a silicon nitride thin film window, through which the electron beam exits to the outside of the vacuum chamber.

[0023] In some embodiments of this disclosure, the substrate to be photolithographically etched is a planar substrate or a non-planar substrate; wherein, the structure of a non-planar substrate includes one or more combinations of protrusions, recesses, sidewalls, ramps, bends, and steps.

[0024] In some embodiments of this disclosure, the substrate is an insulating substrate composed of one or more materials selected from silicon, silicon dioxide, glass, aluminum oxide, diamond, silicon carbide, gallium arsenide, and gallium nitride; or, the substrate is a flexible substrate composed of one or more materials selected from polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polyimide, and polydimethylsiloxane.

[0025] In some embodiments of this disclosure, the method includes multiple photolithography processes executed sequentially. Each photolithography process includes the preparation step, the molding step, the photolithography step, the mold removal step, and the development step. Each photolithography process uses patterned nanoparticle thin films with different patterns as photolithography masks, and an optical alignment system is used to position or align the pattern positions between each photolithography process to form a resist film pattern composed of different pattern combinations on the substrate or electron beam resist film.

[0026] Corresponding to the above method, this disclosure also provides a projection electron beam lithography apparatus, comprising: an electron beam generating device for generating an electron beam for lithography; a displacement stage for supporting and moving a substrate to be lithographically lithographically oriented; wherein an electron beam resist film and a patterned nanoparticle film partially covering the electron beam resist film are formed on the surface of the substrate to be lithographically oriented; a control system for controlling the switching, energy, and current of the electron beam of the electron beam generating device, and for controlling the moving direction and moving speed of the displacement stage, so that the substrate covered with the electron beam resist film and the nanoparticle film is located on the travel path of the electron beam, so that the electron beam exposes the electron beam resist film covered with the nanoparticle film; and a driving system for providing voltage drive to the electron beam generating device, the displacement stage, and the control system.

[0027] In some embodiments of this disclosure, the electron beam generating apparatus includes a vacuum chamber, an electron source, an electron accelerating electrode, and an electron emission window. The electron source is located inside the vacuum chamber and is used to emit an electron beam; the electron accelerating electrode is located inside the vacuum chamber or on the chamber wall and is used to accelerate the electron beam; the electron emission window is located on the chamber wall, and the accelerated electron beam exits through the electron emission window to the outside of the vacuum chamber, serving as an electron beam for photolithography.

[0028] In some embodiments of this disclosure, the environment outside the vacuum chamber where the substrate is located is a vacuum environment or an atmospheric environment. When the environment outside the vacuum chamber is an atmospheric environment, the emitted electron beam is scattered by air molecules into a diffuse electron beam, which serves as the electron beam for photolithography.

[0029] In some embodiments of this disclosure, an optical alignment system is also included for positioning or aligning the graphic position.

[0030] In some embodiments of this disclosure, a vacuum system is also included for providing a vacuum environment for the electron beam generating apparatus and the displacement stage.

[0031] In the projection electron beam lithography method and apparatus disclosed herein, the working principle of electron beam exposure of the electron beam resist film is as follows: Due to the obstruction of the electron beam by the nanoparticle film acting as a mask, the electron beam irradiation dose received by the electron beam resist film positions covered by the nanoparticle film is less than that of the electron beam resist film positions not covered by the nanoparticle film. If the electron beam dose is controlled so that the electron beam resist film positions not covered by the nanoparticle film are fully exposed, then the electron beam resist film positions covered by the nanoparticle film will be partially or completely unexposed. Therefore, after development is completed, the electron beam resist film positions not covered by the nanoparticle film are removed or retained, thereby obtaining a resist film pattern on the substrate that is the same as or complementary to the pattern of the nanoparticle film. Since the nanoparticle film acting as a mask and the electron beam resist film can be closely adhered and conformally contacted, the pattern on the nanoparticle film will be accurately transferred to the electron beam resist film at a 1:1 ratio. Furthermore, this disclosure uses a diffuse electron beam as the electron beam for photolithography. The electron motion direction of the diffuse electron beam is randomly distributed, making it difficult to pass through the small gaps between nanoparticles. Therefore, the small gaps between nanoparticles in the nanoparticle film can be avoided by transferring them onto the electron beam resist film. This allows the discontinuous nanoparticle film to be used as a mask to achieve continuous resist film patterns.

[0032] The projection electron beam lithography method and apparatus proposed in this disclosure use patterned nanoparticle thin films as masks. Because nanoparticle thin films have advantages such as low cost, good conformal contact with the substrate leading to minimal deformation, large area, and single-use capability, they can solve the problems of high mask processing difficulty, high cost, and susceptibility to deformation in previous projection electron beam lithography technologies. Furthermore, the projection electron beam lithography method and apparatus proposed in this disclosure can use diffusely scattered electron beams as the lithography electron beam. This eliminates the need for precision electron optics systems and ultra-high vacuum systems, which helps reduce equipment and lithography costs. Simultaneously, it can achieve large-area, high-brightness, and uniform electron beams. The characteristics of large-area deformation-free masks and large-area, high-brightness, and uniform electron beams give the projection electron beam lithography method and apparatus of this disclosure the advantage of high lithography throughput, solving the problem of low processing throughput in previous electron beam lithography technologies.

[0033] 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.

[0034] 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

[0035] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this application, 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 disclosure. For ease of illustration and description of certain parts of this disclosure, 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 disclosure. In the drawings:

[0036] Figure 1 is a flowchart of a projection electron beam lithography method according to an embodiment of the present disclosure.

[0037] Figure 2 is a flowchart of a projection electron beam lithography method according to another embodiment of this disclosure.

[0038] Figure 3 is a flowchart of a patterned nanoparticle film in one embodiment of this disclosure.

[0039] Figure 4 is a schematic diagram of a projection electron beam lithography method based on a nanoparticle thin film as a mask in one embodiment of this disclosure.

[0040] Figure 5 is a flowchart and schematic diagram of the electron beam lithography technology based on nanoparticle thin films as masks in Embodiment 1 of this disclosure.

[0041] Figure 6 is a flowchart and schematic diagram of the preparation of gold nanoparticle thin films by self-assembly transfer imprinting in Embodiment 2 of this disclosure.

[0042] Figure 7 is a flowchart and schematic diagram of the patterned PDMS template creation process in Embodiment 2 of this disclosure.

[0043] Figure 8 is a schematic diagram of the photolithography principle of diffuse electron beam in atmospheric environment in Embodiment 3 of this disclosure.

[0044] Figure 9 is a scanning electron microscope image of the pattern obtained by electron beam lithography under atmospheric diffuse electron beam in Embodiment 3 of this disclosure.

[0045] Figure 10 is a schematic diagram of electron beam lithography performed on a non-planar substrate in Embodiment 4 of this disclosure.

[0046] Figure 11 is a schematic diagram of the structure of a projection electron beam lithography apparatus according to an embodiment of the present disclosure.

[0047] Figure 12 is a schematic diagram of the structure of an electron beam generating device in one embodiment of the present disclosure.

[0048] Figure 13 is a schematic diagram of a scheme for achieving wafer-level lithography based on a small single electronic window and the movement of a displacement stage in one embodiment of this disclosure. Detailed Implementation

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The projection electron beam lithography method proposed in this disclosure uses a patterned nanoparticle film located on the surface of an electron beam resist film as a mask. The patterned nanoparticle film covers some areas of the electron beam resist film surface while leaving others uncovered. The working principle of this method is as follows: the nanoparticle film blocks the electron beam, preventing or minimizing exposure of the electron beam to the nanoparticle-covered electron beam resist film, while exposing the uncovered areas. After exposure, the molecular chains of the electron beam resist become longer or shorter. Through interaction with the developer, the electron beam resist film beneath the nanoparticle film is retained or removed, forming a pattern in the electron beam resist film that is identical or complementary to the pattern in the nanoparticle film, thereby achieving the lithography process.

[0055] Figure 1 is a flowchart of a projection electron beam lithography method according to an embodiment of this disclosure. The projection electron beam lithography method includes the following steps:

[0056] Step S110: Preparation step: Cover the substrate surface with an electron beam resist film.

[0057] Here, "coverage" refers to the positional relationship between different material layers. Coverage does not mean complete obfuscation. Electron beam resist films do not need to cover the entire upper surface of the substrate, and patterned nanoparticle films do not need to cover the entire electron beam resist film.

[0058] In this embodiment, the electron beam resist is a viscoelastic material spin-coated onto the substrate surface, typically made of materials such as polymethyl methacrylate (PMMA) or EBR-9 (poly(alfa-trifluoroethyl chloroacrylate)). After spin-coating, it is cured by heating. Its surface also has a low Young's modulus (PMMA is typically 2500 MPa) and high viscoelasticity, which helps increase the contact area between the nanospheres and the resist on the substrate, thus improving transfer efficiency.

[0059] Step S120: Molding step: A patterned nanoparticle film partially covering the electron beam resist film is formed on the surface of the electron beam resist film to serve as a mask for electron beam lithography.

[0060] Step S130: Photolithography step: The substrate covered with an electron beam resist film and a nanoparticle film is placed in the path of the electron beam used for photolithography, so that the electron beam exposes the electron beam resist film covered with the nanoparticle film.

[0061] In this embodiment, the substrate can be placed facing the path of the electron beam used for photolithography, allowing the electron beam to interact with the resist film to expose the resist film. There are cases where the electron beam exposes both the electron beam-covered and uncovered nanoparticle film locations, but because the exposure levels differ between the covered and uncovered nanoparticle film locations, an exposure pattern is formed.

[0062] Step S140: Mask removal step: After exposure, the nanoparticle film used as a mask is removed. The nanoparticle film can be removed by solution cleaning.

[0063] In the embodiments of this application, the substrate after exposure can be placed in a cleaning solution to remove the nanoparticle film, or the substrate surface can be sprayed or rinsed with a cleaning solution.

[0064] Step S150: Development step: The substrate still covered with electron beam resist film is developed to form a resist film pattern on the substrate that is the same as or complementary to the pattern of the nanoparticle film.

[0065] In this embodiment, the developing step can be achieved by placing the substrate in a developing solution and using the developing solution to dissolve the electron beam resist in the areas that have been exposed by the electron beam or have not been exposed by the electron beam.

[0066] The projection electron beam lithography method proposed in this disclosure uses patterned nanoparticle thin films as masks, which can perform lithography using high-throughput electron beams. This helps to overcome the problem of low processing throughput in existing electron beam lithography technology and improves lithography efficiency. Compared with the projection electron beam lithography technology in the prior art, it does not require a precision electron optical system and an ultra-high vacuum system, which helps to reduce equipment costs and lithography costs.

[0067] In some embodiments of this disclosure, after coating the substrate surface with an electron beam resist film, the method further includes: placing the substrate coated with the electron beam resist film on a heating stage and baking it for a preset time. This method removes the solvent from the electron beam resist by baking the substrate, thereby stabilizing the electron beam resist film layer, improving its uniformity, and ensuring pattern fidelity in subsequent exposure processes.

[0068] In some embodiments of this disclosure, after the development step, the method further includes fixing the substrate still covered with an electron beam resist film.

[0069] In this embodiment of the application, fixing the substrate still covered with an electron beam resist film can be achieved by placing the substrate covered with a patterned electron beam resist film in a fixing solution.

[0070] Using this embodiment, the developer can be removed by fixing, thereby preventing overdevelopment caused by the resist continuously reacting with the developer, and obtaining a stable resist film pattern. From a photolithography perspective, once the pattern is formed on the resist film, photolithography is complete, and the pattern is then transferred to the substrate through subsequent deposition or etching steps.

[0071] Figure 2 is a flowchart of a projection electron beam lithography method according to another embodiment of this disclosure. The method includes the following steps: Step S210: Preparation step: Covering the substrate surface with an electron beam resist film. Step S220: Placing the substrate covered with the electron beam resist film on a heating stage and baking for a preset time. Step S230: Molding step: Forming a patterned nanoparticle film partially covering the electron beam resist film on the surface of the electron beam resist film, as a lithography mask. Step S240: Lithography step: Placing the substrate covered with the electron beam resist film and the nanoparticle film in the path of the electron beam used for lithography, so that the electron beam exposes the electron beam resist film. Step S250: Removal step: Removing the nanoparticle film as the lithography mask after exposure. Step S260: Development step: Developing the substrate still covered with the electron beam resist film to form a resist film pattern on the substrate that is the same as or complementary to the pattern of the nanoparticle film. Step S270: Fix the substrate that is still covered with an electron beam resist film.

[0072] In some embodiments of this disclosure, the nanoparticle film covering the surface of the electron beam resist film is one or more layers, the diameter of the nanoparticles is between 1-1000 nm, and the type of nanoparticles is metal nanoparticles or non-metal nanoparticles.

[0073] This embodiment allows for the achievement of various electron beam lithography effects using nanoparticle masks of different types, sizes, and thicknesses. In particular, in existing technologies, achieving a rigid mask thickness of 100nm is extremely difficult and costly. This solution significantly reduces costs and, by using nanoparticle films as masks, allows for mask thicknesses below 100nm. Furthermore, compared to rigid masks, nanoparticle films can achieve a closer and more conformal contact with the electron beam resist film, resulting in finer and more accurate lithography mask effects.

[0074] Figure 3 is a flowchart illustrating a patterned nanoparticle film in one embodiment of this disclosure. In some embodiments of this disclosure, the molding step includes:

[0075] Step S310: Self-assembly step: A nanoparticle film is formed on the surface of the nanoparticle solution through self-assembly.

[0076] Step S320: The pre-prepared stamp with raised patterns is brought into contact with the self-assembled nanoparticle film to form a nanoparticle film on the surface of the raised patterns of the stamp.

[0077] Step S330: The stamp with the raised pattern surface forming a nanoparticle film is brought into contact with the electron beam resist film covering the substrate surface and pressure is applied so that the nanoparticle film formed on the raised pattern surface of the stamp covers the surface of the electron beam resist film.

[0078] Steps S320 and S330 above are transfer imprinting steps, which are performed at least once (i.e. once or more) to form at least one (i.e. one or more) patterned nanoparticle films partially covering the electron beam resist film on the surface of the electron beam resist film.

[0079] Among them, the bonding force between the nanoparticle film and the material of the raised pattern of the stamp is greater than that between the nanoparticle film and the nanoparticle solution, while the bonding force between the nanoparticle film and the material of the raised pattern of the stamp is less than that between the nanoparticle film and the electron beam resist film.

[0080] Using this embodiment, a patterned nanoparticle film partially covering the electron beam resist film can be formed on the surface of the electron beam resist film by self-assembly transfer imprinting. Using the patterned nanoparticle film as an electron beam lithography mask is beneficial for using a large-area electron beam for projection lithography, and high-throughput lithography can be achieved at low cost.

[0081] In some embodiments of this disclosure, the material of the raised graphic portion of the stamp is selected from: polydimethylsiloxane, polymethyl methacrylate, and polyvinyl alcohol. This solution is not limited to these; the above are merely examples, and any organic polymer that conforms to the above-mentioned bonding strength range is acceptable.

[0082] Using this embodiment, a variety of materials can be used to achieve the transfer and imprinting of the seal.

[0083] In some embodiments of this disclosure, the material of the nanoparticle film may be selected from gold, silver, silicon oxide, and polyethylene. This approach is not limited to these; the above are merely examples, and any nanoparticle film material that conforms to the aforementioned bonding strength range is acceptable.

[0084] Using this embodiment, it is possible to use a variety of materials to realize the use of nanoparticle thin films as photolithography masks.

[0085] In some embodiments of this disclosure, the demolding step removes the nanoparticle film by solution washing.

[0086] In the embodiments of this application, the cleaning solution used to remove the nanoparticle film can be of various types. For example, soap solution, deionized water, a mixed solution of ethanol and acetone, etc., can be used as the cleaning solution to remove the nanoparticle film on a substrate such as glass. The above are merely examples, and the solution is not limited thereto.

[0087] In some embodiments of this disclosure, the method further includes the step of generating an electron beam for photolithography, comprising: generating and accelerating an electron beam in a vacuum chamber, wherein the accelerated electron beam exits through a window in the wall of the vacuum chamber to the outside of the vacuum chamber, and the exited electron beam serves as the electron beam for photolithography.

[0088] In this embodiment, the window on the wall of the vacuum chamber can be a silicon nitride thin film window, through which the electron beam exits to the outside of the vacuum chamber.

[0089] This embodiment enables the fabrication of electron beams for projection lithography within a vacuum chamber. Because this approach uses patterned nanoparticle films as masks, high-throughput electron beams can be directly used for efficient lithography. Compared to existing direct-write electron beam lithography, this significantly improves processing throughput and lithography efficiency. Furthermore, unlike existing direct-write and projection electron beam lithography techniques, this approach eliminates the need for electron beam focusing and deflection systems.

[0090] In some embodiments of this disclosure, the environment outside the vacuum chamber where the substrate is located can be a vacuum environment or an atmospheric environment. When the environment outside the vacuum chamber is an atmospheric environment, the emitted electron beam is scattered by air molecules into a diffusely scattered electron beam, which serves as the electron beam for photolithography. Optionally, the environment outside the vacuum chamber can also be another gaseous environment with a pressure greater than or less than one atmosphere.

[0091] This embodiment enables the formation of large-area, high-intensity, and highly uniform electron beams for photolithography using diffuse-scattered electron beams, which is beneficial for improving photolithography throughput. Furthermore, the electron motion direction of diffuse-scattered electron beams is relatively randomly distributed, making it difficult to penetrate the small gaps between nanoparticles. Therefore, the small gaps between nanoparticles in the nanoparticle film can be prevented from being transferred to the electron beam resist film, allowing the discontinuous nanoparticle film to be used as a mask to achieve continuous electron beam resist film patterns.

[0092] In some embodiments of this disclosure, the method includes multiple photolithography processes executed sequentially. Each photolithography process includes the preparation step, the molding step, the photolithography step, the mold removal step, and the development step. Each photolithography process uses patterned nanoparticle thin films with different patterns as photolithography masks, and an optical alignment system is used to position or align the pattern positions between each photolithography process to form a resist film pattern composed of different pattern combinations on the substrate or electron beam resist film.

[0093] This embodiment enables the alignment of different patterns through an optical alignment system, and the combination of different patterns facilitates the formation of more complex resist film patterns. Furthermore, the overlay method leverages the advantage of this approach in performing photolithography on non-planar substrates. Existing electron beam lithography techniques require high-quality converging electron beams or large-area parallel electron beams, and their lithography accuracy is greatly affected by aberrations such as spherical aberration, chromatic aberration, and astigmatism in the electron optical system. Additionally, it requires uniform working distances across the substrate, making it difficult to perform photolithography on non-planar substrates.

[0094] Figure 4 is a schematic diagram of a projection electron beam lithography method based on a nanoparticle film as a mask in one embodiment of this disclosure. The left image in Figure 4 shows an "H"-shaped patterned nanoparticle film on the surface of an electron beam resist film covering a substrate. The substrate covered with the "H"-shaped nanoparticle film is placed face-to-face in the path of the electron beam. The electron beam irradiates the substrate, which is sequentially covered with an electron beam resist film and an "H"-shaped nanoparticle film. Due to the obstruction of the electron beam by the nanoparticle film mask, the electron beam resist film in the "H"-shaped region is not exposed by the electron beam, while the electron beam resist film in the remaining regions is exposed. When the electron beam resist is a positive electron beam resist, the exposed electron beam resist film can be removed by the developer. Finally, an "H"-shaped pattern is also formed on the electron beam resist film, achieving the purpose of photolithography and pattern transfer. The right figure shows that the "H" pattern of the nanoparticle film was transferred onto the electron beam resist film, and an "H" pattern with a 1:1 scale to the pattern on the nanoparticle film was formed on the electron beam resist film.

[0095] Figure 5 is a flowchart and schematic diagram of the electron beam lithography technique based on a nanoparticle thin film as a mask in Embodiment 1 of this disclosure. The flowchart of the electron beam lithography method in Embodiment 1 is as follows:

[0096] (1) Preparation steps: Spin-coat a thin film of electron beam resist onto the surface of the substrate to be photolithographically prepared. The substrate can be an insulating substrate or a flexible substrate. The substrate material can be a hard material composed of one or more of silicon, silicon oxide, silicon carbide, diamond, and glass, or a flexible material composed of one or more of polydimethylsiloxane, polymethyl methacrylate, and polyvinyl alcohol. The morphology of the substrate can be a planar substrate or a non-planar substrate containing one or more of the following structures: protrusions, depressions, sidewalls, slopes, bends, and steps. The electron beam resist can be one or more of PMMA, ZEP-520, and HSQ. To obtain a more accurate pattern, a baking step can be added after step (1), in which the substrate covered with the electron beam resist film is placed on a heating stage and baked for a period of time to remove the solvent of the electron beam resist.

[0097] (2) Masking Step: A patterned nanoparticle film is prepared on the surface of the electron beam resist film as a mask. The nanoparticle film serving as the mask may contain one layer of nanoparticles, or two or more layers of nanoparticles. The particles may be metallic nanoparticles composed of metals such as gold and silver, or non-metallic nanoparticles composed of silicon oxide, polyethylene, etc. The diameter of the nanoparticles is in the range of 1-1000 nm.

[0098] The selected nanoparticles are typically noble metals capable of self-assembly, such as gold. A larger atomic number provides better shielding and isolation for electrons, reducing the probability of electrons passing through the mask. Furthermore, regarding the diameter of the nanoparticles, larger diameters result in better electron beam isolation and mask blocking, but also larger gaps between particles, leading to a higher limiting resolution. Therefore, to achieve high-resolution, high-isolation masks, nanoparticles with large atomic numbers and small particle sizes should be preferred.

[0099] (3) Photolithography step: The substrate, which is sequentially covered with an electron beam resist film and a patterned nanoparticle film, is placed face-to-face in the path of the electron beam, so that the electron beam interacts with the electron beam resist film for a period of time to complete the exposure of the resist film. The energy and dose of the electron beam can be controlled according to the thickness and type of the electron beam resist film and the patterned nanoparticle film to achieve the purpose of exposure.

[0100] (4) Removal step: Remove the patterned nanoparticle film from the surface of the electron beam resist film. The patterned nanoparticle film can be removed by solution method, specifically by placing the exposed substrate in a specific solution, so that the nanoparticles are dispersed or dissolved in the solution.

[0101] (5) Development step: The substrate is placed in the developing solution to dissolve the electron beam resist in the areas exposed or not exposed by the electron beam, thereby obtaining a pattern on the nanoparticle film mask or a complementary pattern in the electron beam resist film. In addition, a fixing step can be added after step (5) to place the substrate covered with the patterned electron beam resist film in the fixing solution to remove the developing solution.

[0102] Figure 6 is a flowchart and schematic diagram of the preparation of gold nanoparticle films by self-assembly transfer imprinting in Example 2 of this disclosure. The gold nanoparticle film prepared by the self-assembly transfer imprinting method in Example 2 is used as a mask. The flowchart for preparing gold nanoparticle films by self-assembly transfer imprinting is as follows:

[0103] (1) Self-assembly to obtain a close-packed gold nanoparticle film. A solution of gold nanoparticles modified with ctab ligands and dispersed in ultrapure water of a certain concentration and diameter (or a certain diameter range) is added to a container. Then, 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. This induces 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 the gold nanoparticles and the perfluorinated surfactant is only for example. Through similar self-assembly methods, nanoparticle films of different thicknesses and materials can also be obtained.

[0104] (2) Preparation of a patterned stamp, which can also be called a polydimethylsiloxane (PDMS) soft template, or simply a PDMS soft template. The preparation process is shown in Figure 7, which is a flowchart and schematic diagram of the patterned PDMS template fabrication in Embodiment 2 of this disclosure. First, the substrate surface is patterned, for example, by using ultraviolet lithography or electron beam lithography to prepare a patterned resist template on a silicon substrate, and then the pattern of the template is transferred to the silicon substrate by reactive ion etching. The silicon substrate is subjected to silanization treatment to passivate the surface and prevent PDMS from adhering to the mold during the subsequent demolding process. The PDMS and curing agent are mixed at a speed of 2000 rpm for one minute, and then rotated at a speed of 2200 rpm for two minutes to defoam. Then, the uniformly mixed and bubble-free PDMS mixture is poured into the patterned silicon substrate, spin-coated evenly, and placed under atmospheric conditions for 15 minutes to make the thickness of the edges uniform. After curing, the PDMS is placed at room temperature for 24 hours or heated to 80°C for 2 hours to cure. Upon demolding, the patterned PDMS soft mold or stamp is obtained. The process parameters given here are merely examples, and this disclosure is not limited to them; rather, the process parameters can be reasonably adjusted.

[0105] Unlike existing technologies, conventional unpatterned PDMS soft template transfer of gold nanoparticle films results in unpatterned gold nanoparticle films on the substrate. This solution utilizes a patterned PDMS stamp fabricated through microfabrication, which can form a pattern during the transfer imprinting process, replicating the pattern of the PDMS stamp onto the substrate or an electron beam resist film on the substrate surface.

[0106] (3) Transferring the nanoparticle film onto a patterned PDMS soft template. The side of the PDMS soft template containing the patterned protrusion structure is brought into contact with a monolayer close-packed gold nanoparticle film that is self-assembled on the ethanol surface. Since the bonding force between the gold nanoparticle film and the PDMS soft template is greater than the bonding force 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.

[0107] It is important to emphasize that this method involves directly transferring nanoparticles onto the photoresist. Since photoresists typically have a low Young's modulus, they are prone to deformation under external pressure, which increases the contact area between the gold nanoparticles and the photoresist, thus improving transfer efficiency. Furthermore, this method allows nanoparticle films to be transferred onto various materials, including planar, non-planar, and insulating substrates, using a PDMS soft template for subsequent exposure. Traditional exposure methods struggle to perform exposures on non-planar or insulating substrates.

[0108] (4) Transferring the nanoparticle film to the electron beam resist surface. Manipulate the PDMS soft template so that the side containing the gold nanoparticle film contacts the electron beam resist film covering the substrate surface, and apply a certain pressure. Because the patterned structure on the PDMS soft template surface is more convex than other parts, only the gold nanoparticle film on the patterned convex surface will contact the electron beam resist film. Since the adhesion force between the gold nanoparticle film and the electron beam resist film is greater than its adhesion force to the PDMS soft template, the gold nanoparticle film on the patterned convex surface is transferred to the electron beam resist film surface. The gold nanoparticle film on the remaining part of the PDMS soft template remains on the PDMS soft template. Therefore, a patterned gold nanoparticle film is obtained on the electron beam resist surface. In this embodiment, the pressure applied to the resist film is preferably sufficient to transfer the nanoparticle film to the resist film on the substrate surface without damaging the nanoparticle film and the resist film.

[0109] Figure 8 is a schematic diagram of the photolithography principle of diffuse scattering electron beam under atmospheric conditions in Embodiment 3 of this disclosure. Embodiment 3 uses a self-assembled transfer imprinted gold nanoparticle film as a mask and a diffuse scattering electron beam under atmospheric conditions as the electron beam for photolithography.

[0110] As shown in Figure 8, the first step is to generate an electron beam. In this embodiment, the electron beam is a diffusely scattered electron beam generated and accelerated in a vacuum chamber, exiting through a window in the chamber wall into the outside atmosphere. Specifically, an electron source within the vacuum chamber emits and generates free electrons in the vacuum. These electrons are accelerated to high energies (typically greater than 5 keV) by an accelerating electrode within the vacuum chamber, enabling them to penetrate a thin-film window in the chamber wall and enter the atmosphere. Upon entering the atmosphere, these high-energy electrons are scattered by air molecules such as nitrogen and oxygen, altering their emission direction and forming diffusely scattered electron beams with varying directions of motion. Subsequently, the generated electron beam is used for exposure. A substrate sequentially coated with an electron beam resist film and a patterned gold nanoparticle film is placed directly below the electron beam exit window, allowing the diffusely scattered electron beam to interact with the electron beam resist to complete the exposure process.

[0111] The electron source used can be a thermionic emission electron source, a field emission electron source, a tunneling emission electron source, or a photoelectric emission electron source. Different electron sources have different requirements for the vacuum level of the vacuum chamber. The vacuum level inside the vacuum chamber must be sufficient for the stable operation of the electron source and to prevent breakdown during the acceleration of the electron beam. The electron beam exit window can be a silicon nitride thin film with a thickness of approximately 100 nm. The silicon nitride film needs to be thin enough to allow the electron beam to penetrate it, but it also needs sufficient thickness and mechanical strength to ensure that the window can withstand the pressure difference between the inside and outside. The silicon nitride thin film can be supported by a silicon substrate on all four sides. The environment outside the vacuum chamber can be a standard atmospheric pressure environment or an environment with other pressures, temperatures, and gas types.

[0112] Figure 9 is a scanning electron microscope image of the pattern obtained by electron beam lithography under diffuse scattering electron beam in an atmospheric environment in Embodiment 3 of this disclosure. As shown in Figure 9, the experimental results of electron beam lithography under diffuse scattering electron beam in an atmospheric environment are obtained by using a 20 nm diameter gold nanoparticle film as a mask. The specific parameters of the electron beam lithography are as follows: the mask pattern is a disk array with a diameter of 4 μm and a spacing period of 8 μm; the electron beam is emitted from a thermionic filament in a vacuum chamber with a pressure of approximately 0.1 Pa and accelerated to 10 keV in the vacuum chamber; the electron beam current density entering the atmospheric environment is approximately 150 μA / cm. 2The electron beam exit window was a silicon nitride thin film window with a thickness of 100 nm and a side length of 1 mm; the atmospheric environment was room temperature and standard atmospheric pressure; the electron beam resist film was a PMMA film with a thickness of approximately 200 nm located on the surface of the SiO2 / Si substrate; the distance between the exit window on the vacuum chamber wall and the resist film was 1 mm; the developer was a solution of methyl isobutyl ketone and isopropanol mixed in a 1:3 ratio, and the development time was 30 s; the fixing solution was an isopropanol solution, and the fixing time was 30 s; the exposure time was 3 s; after exposure, the gold nanoparticle film on the surface of the resist film was removed by cleaning with potassium iodide solution for 5 s. It can be seen that after photolithography, an electron beam resist film disk array with a size ratio of 1:1 to the mask pattern was obtained on the substrate, achieving a very good electron beam lithography effect.

[0113] Importantly, the exposure time required to obtain this result is only 3 seconds. If wafer-level electron beam lithography is performed with the same electron beam dose, the throughput of electron beam lithography can reach 1200 wafers / hour, far exceeding the throughput of various existing electron beam lithography technologies. Moreover, due to the absence of precision electron optics systems and high vacuum systems, the cost of this electron beam lithography technology is much lower than that of various existing electron beam lithography technologies.

[0114] Figure 10 is a schematic diagram of electron beam lithography on a non-planar substrate in Embodiment 4 of this disclosure. The left image in Figure 10 shows the principle of electron beam lithography on a non-planar substrate using a nanoparticle thin film as a mask and a diffusely scattered electron beam in an atmospheric environment. The right image shows that after development, the pattern on the nanoparticle thin film mask is transferred to the electron beam resist film.

[0115] In Example 4, the substrate used for electron beam lithography is a non-planar substrate. Electron beam lithography is performed on the non-planar substrate using a nanoparticle thin film as a mask and a diffusely scattered electron beam in an atmospheric environment. As shown in Figure 10, the non-planar substrate, which is sequentially covered with an electron beam resist film and a patterned gold nanoparticle film, is placed face-to-face below the electron beam exit window, allowing the diffusely scattered electron beam to interact with the electron beam resist film to complete the exposure process. After exposure, the patterned nanoparticle film is removed, and after development and fixing, the pattern on the nanoparticle film is transferred to the electron beam resist film, completing the lithography process. Furthermore, the non-planar substrate can be a non-planar substrate with one or more structures including protrusions, depressions, sidewalls, slopes, bends, and steps; it can be a rigid substrate or a flexible substrate.

[0116] Traditional electron beam lithography employs a precision electron optical system to converge, scan, or project an electron beam. This requires a high working distance for the electron beam, meaning that every location on the substrate must be at the same distance from the electron focusing lens or hard mask. Simultaneously, aberrations such as spherical aberration, chromatic aberration, and astigmatism within the electron optical system must be controlled to very low levels; otherwise, the exposed pattern will be distorted. Non-planar substrates are difficult to meet these requirements. Therefore, traditional electron beam lithography is ill-suited for processing non-planar substrates with structures such as protrusions, depressions, sidewalls, slopes, bends, and steps.

[0117] As mentioned earlier, this embodiment uses a nanoparticle thin film as a mask, which exhibits excellent conformal adaptability to non-planar structures on the substrate, such as protrusions, depressions, sidewalls, slopes, bends, and steps. It can achieve close contact with the electron beam resist film on these structural surfaces, ensuring that electron beam resist films at different locations on the non-planar substrate surface can maintain close contact with the mask. Furthermore, this embodiment uses a diffuse electron beam from an atmospheric environment, which is a non-focused electron beam. Therefore, it does not require that the distance from each location on the substrate to the electron focusing lens be the same, and it is free from electron optical systems and unaffected by electron optical system aberrations. In addition, the diffuse electron beam has electrons moving in all directions, enabling exposure of electron beam resist films on the substrate that are not directly facing the electron beam exit window. Therefore, it can expose electron beam resist films with structural surfaces such as protrusions, depressions, sidewalls, slopes, bends, and steps. The use of these two technologies allows this technical solution to overcome the limitation of traditional electron beam lithography technology, which can only perform photolithography on planar substrates, and can also process non-planar substrates.

[0118] Figure 11 is a schematic diagram of the structure of a projection electron beam lithography apparatus according to an embodiment of the present disclosure. The projection electron beam lithography apparatus proposed in this application includes the following structure: (1) an electron beam generating device for generating an electron beam for lithography; (2) a displacement stage for supporting and moving a substrate to be lithographically lithographically oriented; wherein an electron beam resist film and a patterned nanoparticle film partially covering the electron beam resist film are sequentially formed on the surface of the substrate to be lithographically oriented; (3) a control system for controlling the switching, energy and current of the electron beam of the electron beam generating device, and for controlling the moving direction and moving speed of the displacement stage, so that the substrate covered with the electron beam resist film and the nanoparticle film is located on the travel path of the electron beam, so that the electron beam exposes the electron beam resist film; (4) a driving system for providing voltage drive to the electron beam generating device, the displacement stage and the control system.

[0119] Furthermore, the electron beam generated by the electron beam generating device can be a large-spot electron beam. A resist film and a patterned nanoparticle film are sequentially coated onto the substrate to be photolithographically patterned; the preparation method can be referred to in Examples 1 and 2.

[0120] Using the projection electron beam lithography equipment proposed in this application is beneficial for realizing the projection electron beam lithography method as described in the above embodiments.

[0121] Figure 12 is a schematic diagram of an electron beam generating apparatus according to an embodiment of this disclosure. The electron beam generating apparatus includes a vacuum chamber, an electron source, an electron accelerating electrode, and an electron emission window. The electron source is located inside the vacuum chamber and is used to emit an electron beam. The electron emission window is located on the wall of the vacuum chamber and is used to accelerate the electron beam. The electron accelerating electrode is located inside the vacuum chamber or on the wall of the vacuum chamber. The accelerated electron beam exits through the electron emission window to the outside of the vacuum chamber, and the emitted electron beam serves as an electron beam for photolithography. Using this embodiment, an electron beam for photolithography can be generated using the electron beam generating apparatus. The electron source is used to emit free electrons. The electron source can be an iridium-yttrium oxide thermionic electron source, or other forms of thermionic electron sources or electron sources using other physical mechanisms, including but not limited to field emission electron sources, tunneling emission electron sources, photoelectric emission electron sources, etc. The electron accelerating electrode is used to accelerate the electrons emitted by the electron source. When accelerating electrons, a high voltage is applied between the electron accelerating electrode and the electron source, and the potential of the electron accelerating electrode is higher than the potential of the electron source. The electron beam exit window used needs to be thin enough to allow the accelerated high-energy electron beam to exit from inside the vacuum chamber to the outside; it also needs to have sufficient thickness and mechanical strength to withstand the pressure difference between the inside and outside of the vacuum chamber. The electron exit window can be a silicon nitride thin film or thin film array with a thickness of about 100 nm and supported by a silicon substrate on all sides.

[0122] When the vacuum chamber is surrounded by atmospheric pressure, the high-energy electron beam is scattered by air molecules upon entering the atmosphere, forming a large-area, high-intensity, and highly uniform diffuse electron beam with electrons moving in all directions. This large-area diffuse electron beam can be used for photolithography. Since projection electron beam lithography equipment can employ the high-throughput electron beam lithography method described in Example 3 without requiring a precision electron optics system or a high-vacuum system, it simultaneously offers the advantages of high photolithography throughput and low cost.

[0123] In some embodiments of this disclosure, the substrate is either a planar substrate or a non-planar substrate; wherein, the structure of the non-planar substrate includes one or more combinations of protrusions, recesses, sidewalls, ramps, bends, and steps.

[0124] Using this embodiment is beneficial for applying the projection electron beam lithography method proposed in this application to various types of substrates, and is beneficial for meeting the lithography requirements of different spatial structures.

[0125] Because the projection electron beam lithography equipment proposed in this disclosure uses patterned nanoparticle thin films as masks and diffusely scattered electron beams in an atmospheric environment, it can perform photolithography on non-planar substrates with structures such as protrusions, depressions, sidewalls, slopes, bends, and steps, and can also perform photolithography on flexible substrates. In some embodiments of this disclosure, the substrate is an insulating substrate composed of one or more materials selected from silicon, silicon dioxide, glass, alumina, diamond, silicon carbide, gallium arsenide, and gallium nitride; or, the substrate is a flexible substrate composed of one or more materials selected from polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polyimide, and polydimethylsiloxane.

[0126] This embodiment enables the design of insulating substrates or flexible substrates using a variety of materials, thereby meeting different photolithography requirements.

[0127] In some embodiments of this disclosure, the displacement stage can move independently in three directions: left and right, front and back, and up and down. Under the control of the control system, the displacement stage can move the substrate to be lithographicated according to the path shown in Figure 10, enabling the splicing of multiple small exposure areas to achieve a larger area of ​​wafer-level exposure. Figure 13 is a schematic diagram of a wafer-level lithography scheme based on a small single electronic window combined with the movement of the displacement stage in one embodiment of this disclosure. It illustrates the principle of wafer-level scanning and lithography on the wafer by using a zigzag movement method based on a small single electronic window combined with the movement of the displacement stage.

[0128] In some embodiments of this disclosure, the device further includes an optical alignment system for positioning or aligning patterns. The optical alignment system is used to align the relative positions of different patterns during the overlay process of an electron beam resist film covering the substrate surface. In embodiments of this application, the optical alignment system structurally includes an optical microscope and a rangefinder. The optical microscope is used to observe the overlay marks, and the rangefinder is used for precise positioning and displacement feedback of the substrate. This disclosure is not limited thereto; the structure of the optical alignment system described above is merely illustrative.

[0129] Using this embodiment facilitates the alignment of overprinted patterns.

[0130] In some embodiments of this disclosure, the device further includes a vacuum system for providing a vacuum environment for the electron beam generating device and the displacement stage. In embodiments of this application, the vacuum system may structurally include a vacuum pump, a vacuum gauge, and a vacuum chamber. The vacuum pump is used to obtain a vacuum environment within the vacuum chamber, the vacuum gauge is used to measure the vacuum level within the vacuum chamber, and the electron beam generating device and the displacement stage are located within the vacuum chamber.

[0131] This embodiment is advantageous for achieving photolithography in a fully vacuum environment.

[0132] During photolithography, the substrate to be photolithographically lithographically shaped is placed on the displacement stage (or sample stage), with the side covered by the resist film and the patterned nanoparticle film facing the electron beam generating device. The large-area electron beam generated by the electron beam generating device irradiates the substrate covered by the resist film and the patterned nanoparticle film.

[0133] The principle is shown in Figure 4. The patterned nanoparticle film covers some areas of the electron beam resist film surface with nanoparticle film, while some areas are not covered. The nanoparticle film blocks the electron beam, so that the electron beam resist film covered with nanoparticle film is not exposed or is exposed less by the electron beam, while the electron beam resist film not covered with nanoparticle film is exposed by the electron beam. After exposure, the molecular chains of the electron beam resist become longer or shorter. After interacting with the developer, the electron beam resist film under the nanoparticle film is retained or removed, forming a pattern in the electron beam resist film that is the same as or complementary to the pattern in the nanoparticle film, thereby realizing the photolithography process.

[0134] As described above, the projection electron beam lithography method and equipment provided in this disclosure overcomes the shortcomings of low throughput in existing electron beam lithography technology, the difficulty and deformation of existing masks during processing, eliminates the need for precision electron optics systems and ultra-high vacuum systems, and enables lithography on both insulating and flexible substrates. It is a low-cost projection electron beam lithography method and equipment. In other words, compared to existing electron beam lithography technologies that all use hard masks, the method and equipment proposed in this disclosure, which uses nanoparticle thin films as masks, has the following advantages:

[0135] (1) Nanoparticle thin films and electron beam resist films have excellent conformal adaptability and can be in close contact with electron beam resist films. Even if the substrate and electron beam resist film are uneven, the image on the nanoparticle thin film can be transferred 1:1 to the electron beam resist film using electron beam lithography. Traditional hard masks cannot achieve conformal contact with electron beam resist films, and there is a gap between the mask and the resist film, resulting in poor lithography accuracy.

[0136] (2) Nanoparticle thin film is a disposable mask. After photolithography, the nanoparticle thin film can be removed by a specific solution. Therefore, the requirements for the mask to resist deformation and contamination are low, which significantly reduces the processing difficulty and cost of the mask.

[0137] (3) Self-assembly and stamp transfer can be used to prepare large-area, wafer-level patterned nanoparticle films at low cost, while hard masks are difficult to prepare at low cost and at the wafer level.

[0138] Compared to existing technologies, the method and apparatus proposed in this disclosure, which use diffusely scattered electron beams in an atmospheric environment for electron beam lithography, have the following advantages:

[0139] (1) Diffuse electron beam is a large-area electron beam generated and traveled in an atmospheric environment. It does not require a precision electron optical system for focusing and deflection. Therefore, its exposure process is not affected by aberrations such as spherical aberration, astigmatism, and chromatic aberration. It also does not require an ultra-high vacuum system. Therefore, compared with the traditional electron beam lithography technology that requires a precision electron optical system and an ultra-high vacuum system, the cost is greatly reduced.

[0140] (2) Diffuse electron beams contain electrons moving in various directions. Therefore, in addition to exposing electron beam resist films on substrates with the front facing the electron beam exit window, they can also expose electron beam resist films on substrates with the back facing the electron beam exit window. Thus, they can expose electron beam resist films on structural surfaces including protrusions, depressions, sidewalls, slopes, bends, steps, etc. They can expose electron beam resist films on both hard and flexible substrates. Therefore, they can avoid the requirement of traditional electron beam lithography that the substrate must be a hard planar substrate, and are applicable to a wider range of substrate types.

[0141] (3) Diffuse scattered electron beams have poor directionality and are difficult to penetrate the small gaps between nanoparticles. Therefore, discontinuous nanoparticle films can be used as masks to obtain continuous resist film patterns.

[0142] (4) In an atmospheric environment, the substrate does not easily accumulate charge under electron beam irradiation, so photolithography can be performed on insulating substrates such as glass and quartz. Traditional electron beam lithography is performed in a vacuum environment, where the substrate is prone to charge accumulation. Conductive substrates are required to avoid charge accumulation, and sometimes a layer of conductive material needs to be spin-coated under the electron beam resist film.

[0143] 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.

[0144] 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.

[0145] 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 projection electron beam lithography method, characterized in that, include: Preparation steps: Cover the substrate surface to be photolithographically etched with an electron beam resist film; The molding step involves forming a patterned nanoparticle film that partially covers the electron beam resist film on the surface of the electron beam resist film, which serves as a photolithography mask. Photolithography step: The substrate covered with an electron beam resist film and a nanoparticle film is placed in the path of the electron beam used for photolithography so that the electron beam exposes the electron beam resist film. Mask removal step: Remove the nanoparticle film used as a photomask after exposure is complete; Development step: The substrate still covered with electron beam resist film is developed to form a resist film pattern on the substrate that is the same as or complementary to the pattern of the nanoparticle film.

2. The electron beam lithography method according to claim 1, characterized in that, After coating the substrate surface with an electron beam resist film, the method further includes: placing the substrate coated with the electron beam resist film on a heating stage and baking for a preset time.

3. The electron beam lithography method according to claim 1, characterized in that, After the development step, the method further includes fixing the substrate still covered with an electron beam resist film.

4. The method according to claim 1, characterized in that, The patterned nanoparticle film partially covering the electron beam resist film is formed on the surface of the electron beam resist film, and can be one or more layers. The diameter of the nanoparticles ranges from 1 to 1000 nm, and the type of nanoparticles can be metallic nanoparticles or non-metallic nanoparticles.

5. The method according to any one of claims 1-4, characterized in that, The molding process includes: Self-assembly step: A nanoparticle film is formed on the surface of a nanoparticle solution through self-assembly; The transfer imprinting step includes: A pre-prepared stamp with raised patterns is brought into contact with a self-assembled nanoparticle film, forming a nanoparticle film on the surface of the raised patterns on the stamp; and A stamp with a raised pattern surface forming a nanoparticle film is brought into contact with an electron beam resist film covering the substrate surface and pressure is applied to transfer the nanoparticle film formed on the raised pattern surface of the stamp to the surface of the electron beam resist film. The transfer imprinting step is performed once or multiple times to form one or more patterned nanoparticle films on the surface of the electron beam resist film, partially covering the electron beam resist film.

6. The method according to claim 5, characterized in that, The material of the raised graphic portion of the stamp is selected from: polydimethylsiloxane, polymethyl methacrylate and polyvinyl alcohol.

7. The method according to claim 1, characterized in that, The nanoparticle film is made of materials selected from gold, silver, silicon oxide, and polyethylene.

8. The method according to claim 1, characterized in that, The demolding step involves removing the nanoparticle film through solution cleaning.

9. The method according to claim 1, characterized in that, The method further includes the step of preparing an electron beam for photolithography, which includes: generating and accelerating an electron beam in a vacuum chamber, and then exiting the accelerated electron beam through a window on the wall of the vacuum chamber to the outside of the vacuum chamber, with the exited electron beam serving as the electron beam for photolithography.

10. The method according to claim 9, characterized in that, The environment outside the vacuum chamber where the substrate is located is either a vacuum environment or an atmospheric environment. When the environment outside the vacuum chamber is an atmospheric environment, the emitted electron beam is scattered by air molecules into a diffuse electron beam, which is used as the electron beam for photolithography.

11. The method according to claim 9, characterized in that, The window on the wall of the vacuum chamber is a silicon nitride thin film window, through which the electron beam exits to the outside of the vacuum chamber.

12. The electron beam lithography method according to claim 1, characterized in that, The substrate to be photolithographically etched is either a planar substrate or a non-planar substrate; wherein, the structure of a non-planar substrate includes one or more combinations of structures such as protrusions, depressions, sidewalls, slopes, bends, and steps.

13. The electron beam lithography method according to claim 1, characterized in that, The substrate is an insulating substrate composed of one or more materials selected from silicon, silicon dioxide, glass, aluminum oxide, diamond, silicon carbide, gallium arsenide, and gallium nitride; or, the substrate is a flexible substrate composed of one or more materials selected from polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polyimide, and polydimethylsiloxane.

14. The method according to claim 1, characterized in that, The method includes multiple photolithography processes executed sequentially. Each photolithography process includes the preparation step, the modeling step, the photolithography step, the model removal step, and the development step. Each photolithography process uses patterned nanoparticle thin films with different patterns as photolithography masks, and an optical alignment system is used to position or align the pattern positions between each photolithography process, so as to form a resist film pattern composed of different pattern combinations on the substrate or electron beam resist film.

15. A projection electron beam lithography apparatus, characterized in that, include: Electron beam generating apparatus, used to generate an electron beam for photolithography; A displacement stage is used to support and move a substrate to be photolithographically etched; wherein an electron beam resist film and a patterned nanoparticle film partially covering the electron beam resist film are formed on the surface of the substrate to be photolithographically etched. The control system is used to control the switching, energy and current of the electron beam of the electron beam generating device, and to control the moving direction and speed of the displacement stage so that the substrate covered with electron beam resist film and nanoparticle film is located on the electron beam travel path so that the electron beam exposes the electron beam resist film covered with nanoparticle film. The drive system is used to provide voltage drive for the electron beam generating device, displacement stage, and control system.

16. The electron beam lithography apparatus according to claim 15, characterized in that, The electron beam generating device includes a vacuum chamber, an electron source, an electron accelerating electrode, and an electron emission window. The electron source is located inside the vacuum chamber and is used to emit an electron beam. The electron accelerating electrode is located inside the vacuum chamber or on the wall of the vacuum chamber and is used to accelerate the electron beam. The electron emission window is located on the wall of the vacuum chamber, and the accelerated electron beam is emitted to the outside of the vacuum chamber through the electron emission window. The emitted electron beam serves as the electron beam for photolithography.

17. The electron beam lithography apparatus according to claim 16, characterized in that, The environment outside the vacuum chamber where the substrate is located is either a vacuum environment or an atmospheric environment. When the environment outside the vacuum chamber is an atmospheric environment, the emitted electron beam is scattered by air molecules into a diffuse electron beam, which is used as the electron beam for photolithography.

18. The electron beam lithography apparatus according to claim 15, characterized in that, It also includes an optical alignment system for positioning or aligning graphic elements.

19. The electron beam lithography apparatus according to claim 15, characterized in that, It also includes a vacuum system to provide a vacuum environment for the electron beam generating device and the displacement stage.

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