A soft x-ray based lithography process

Abstract

The application discloses an advanced photolithography process based on soft X-rays, and belongs to the technical field of micro-nano processing, aiming at solving the technical bottleneck problem that the existing photolithography technology is difficult to simultaneously consider high pattern resolution, high production efficiency and low manufacturing cost under the condition of a feature scale below 10 nanometers. The process comprises the steps of test mask preparation, substrate gluing, soft X-ray exposure, development processing, pattern transfer and metallization. By introducing short-wavelength synchrotron radiation soft X-rays as an exposure light source, the application fundamentally breaks through the diffraction limit of traditional optical photolithography, and combines electron beam exposure or focused ion beam direct writing, so that nanometer or even sub-nanometer resolution is realized, the processing efficiency is significantly improved, the process tolerance to mask and substrate surface roughness or local defects is higher, the overall process is simplified, the process window is wide, the implementation cost is low, and the application has good engineering implementability and industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of micro-nano fabrication technology, and to a soft X-ray-based photolithography process. Background Technology

[0002] In today's semiconductor industry and cutting-edge nanoscience research, the ever-shrinking demand for device feature sizes is driving patterning technology towards the nanoscale and even smaller. At this technological juncture, extreme ultraviolet lithography and electron beam lithography are currently recognized and widely studied mainstream technologies for high-resolution patterning. However, both technologies face severe technical bottlenecks and cost challenges when fabricating at the nanoscale limits, as detailed below: (1) Extreme ultraviolet lithography uses extremely short wavelength extreme ultraviolet light as a light source, which theoretically has the ability to prepare extremely high resolution patterns. However, since all materials have strong absorption of EUV light, EUV lithography systems must use reflective optical systems and reflective masks. Any tiny phase defects or particle contamination on the mask will be significantly magnified and copied onto the wafer during imaging, resulting in pattern defects. Manufacturing and using such "zero-defect" or "near-perfect" masks is extremely difficult and costly in terms of detection, repair and protection. In addition, EUV lithography equipment is not only expensive, but also has relatively low light source power and conversion efficiency, which puts continuous pressure on the production efficiency and economy of EUV lithography, thus hindering its large-scale preparation method.

[0003] (2) Electron beam lithography uses a focused electron beam to directly draw patterns on photoresist, which has extremely high resolution and can easily break through 10 nanometers. However, since the pattern needs to be scanned and exposed point by point, its writing speed is relatively slow. For a chip containing hundreds of millions of transistors, it takes several hours or even longer to complete the exposure of an entire wafer. This extremely low throughput makes it completely unable to meet the requirements of industrial mass production for capacity and efficiency. Moreover, high-energy electrons will be scattered in the photoresist and substrate, resulting in unexpected exposure in adjacent areas, causing pattern distortion. The correction is complicated, which makes the production cost high and it is difficult to achieve perfect compensation in high-density patterns.

[0004] This demonstrates that current technologies for nanoscale lines face a dilemma: high efficiency versus high cost (EUV lithography) and high resolution versus low efficiency (electron beam lithography). Therefore, the industry urgently needs to explore a novel nanopatterning technology that can balance high resolution, good production efficiency, and relatively controllable cost to fill the gaps left by existing technological approaches and meet the development needs of cutting-edge fields such as micro / nanoelectronic devices and quantum devices. Summary of the Invention

[0005] To address the above shortcomings, this invention provides a soft X-ray lithography process. Utilizing synchrotron radiation short-wavelength soft X-ray lithography, it overcomes the optical diffraction limit and combines it with multi-gun electron beam parallelism to fabricate gold nanoline structures with linewidths below 10 nanometers on a silicon nitride substrate. This significantly improves fabrication efficiency while maintaining nanoscale resolution, resulting in ultra-fine nanoline structures with both high resolution and high efficiency. The process is simple, has a large tolerance, reduces cost, and is easy to implement. It significantly reduces the difficulty and cost of mask fabrication and can tolerate certain surface roughness or defects, which is beneficial for large-scale industrial production. This solves the problem that existing technologies cannot simultaneously achieve pattern resolution, production efficiency, and manufacturing cost at the 10-20 nanometer scale. The specific technical solution is as follows: The purpose of this invention is to provide a soft X-ray lithography process, comprising the following steps: (1) Preparation of test mask and coated silicon nitride substrate: A gold mask with a gold absorption layer pattern is written directly on a silicon nitride substrate to prepare a test mask; a layer of photoresist is spin-coated on another silicon nitride substrate to prepare a coated silicon nitride substrate. (2) Soft X-ray exposure: The test mask from step (1) is closely aligned with the coated silicon nitride substrate in a synchrotron radiation source and exposed using soft X-rays; (3) Development: The photoresist exposed in step (2) is developed using a developer to transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (4) Pattern transfer: Using the nanoline pattern developed in step (3) as a mask, the pattern is further transferred to the coated silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (5) Metallization: Using electron beam evaporation technology, an adhesion layer and a gold layer are sequentially deposited on the silicon nitride substrate with grooves in step (4). After a stripping process, excess photoresist and the metal attached thereto are removed, and the nano-fine lines are obtained on the silicon nitride substrate.

[0006] Preferably, in step (1), the direct writing is a gold mask on which an initial nanopattern is etched on a silicon nitride substrate using electron beam lithography and reactive ion etching, and a gold absorption layer pattern is directly written on it, or a gold mask on a silicon nitride substrate is formed by direct writing on a gold film using a focused ion beam.

[0007] Preferably, the initial nanopattern is an initial silicon fin structure with a period of 100 nm and a linewidth of 3 nm to 50 nm.

[0008] Preferably, in step (1), the gold absorption layer pattern has sufficient absorption rate for soft X-rays, and it is prepared by using an electron beam exposure system with parallel direct writing technology combined with electroplating or physical vapor deposition process for direct writing.

[0009] Preferably, in step (1), the test mask substrate is a nitrided silicon wafer with a diameter of 2 inches.

[0010] Preferably, in step (1), the method for preparing the silicon nitride substrate specifically includes the following steps: using a single crystal silicon wafer with a diameter of 2 inches as a substrate, a low-pressure chemical vapor deposition process is used, silane and ammonia are introduced as reaction gases, and a silicon nitride thin film is formed by reaction deposition at a temperature of 700-800°C. Then, an electron beam evaporation or magnetron sputtering technique is used to sequentially deposit a titanium adhesion layer with a thickness of 2-3 nm and a gold mask layer with a thickness of 95-105 nm on the surface of the silicon nitride thin film to form a metal mask structure with a thickness of 200 nm and a length of 2 inches, thereby obtaining the silicon nitride substrate.

[0011] Preferably, in step (1), the photoresist is an amorphous zeolite imidazole ester framework film with a thickness of 100 nm, using a ZIF photoresist. The photoresist is sensitive to soft X-rays, and its thickness can be controlled within the range of tens to hundreds of nanometers using spin-coating technology, exhibiting excellent uniformity. The soft X-ray exposure time is extremely short, requiring only a few seconds.

[0012] Preferably, in step (2), the wavelength of the soft X-ray is 0.1 nm to 1 nm, and the exposure dose is 10 to 900 mJ / cm². 2 The magnitude is [not specified]; the synchrotron radiation source is 1-2 keV white light.

[0013] Preferably, in step (5), the adhesion layer is titanium with a thickness of 2 nm, and the gold layer has a thickness of 95-105 nm.

[0014] Preferably, in step (5), the nano-fine lines are a gold nanoline array with a linewidth of 3 to 20 nm and good uniformity.

[0015] The present invention achieves at least the following beneficial effects: 1. To address the technical bottleneck of existing photolithography technologies in simultaneously achieving high pattern resolution, high production efficiency, and low manufacturing costs at feature scales below 10 nanometers, this invention fundamentally breaks through the diffraction limit of traditional optical lithography. It employs short-wavelength soft X-rays from synchrotron radiation of energetic ions as the exposure source, combined with electron beam exposure or focused ion beam direct writing. This significantly improves processing efficiency while achieving nanometer-level or even sub-nanometer-level resolution. Synchrotron radiation refers to the high-energy electromagnetic waves radiated along the tangent of the orbit of charged particles moving at high speed in the relativistic energy region under the influence of an external magnetic field. The wavelength of this radiation can be as short as the nanometer scale. Existing chip lithography processes widely use exposure wavelengths such as 248nm, 193nm, and 13.5nm, all constrained by the optical diffraction limit and the minimum achievable feature size. The soft X-ray band used in this invention further breaks through these physical limits, enabling photolithography processes to advance to atomic scales and even scales with significant quantum effects. This is considered one of the ultimate solutions in the field of ultra-micro / nano chip manufacturing. At the same time, this process significantly reduces the difficulty and cost of mask preparation, has a high process tolerance for surface roughness or local defects of the mask and substrate, simplifies the overall process, has a wide process window, and has low implementation cost, and has good engineering feasibility and industrial application prospects.

[0016] 2. The nanoscale ultrafine lines obtained by this invention possess both high resolution and high efficiency. Synchrotron radiation soft X-rays are used as the exposure light source, with a wavelength range covering 0.1 nm to 1 nm. This wavelength range has a higher theoretical resolution than the traditional 13.5 nm extreme ultraviolet light. A multi-gun electron beam parallel direct writing system is used to prepare the X-ray mask. Its high precision and parallel writing capability can effectively improve the mask preparation efficiency. By using short-wavelength soft X-rays to break through the optical diffraction limit and combining it with multi-gun electron beam parallelism, the fabrication efficiency is significantly improved while ensuring nanoscale resolution.

[0017] 3. The present invention has a large process tolerance and reduced cost: By utilizing the high penetrability of soft X-rays, the mask does not need to pursue the ultimate light transmission perfection. That is, the strong penetrating ability of soft X-rays reduces the stringent requirements for the perfection of the mask, allowing the process to tolerate a certain degree of surface roughness or defects. This significantly reduces the stringent requirements for the mask, which greatly reduces the difficulty and cost of mask preparation.

[0018] 4. This invention uses photon exposure, which results in a gentler interaction between photons and materials. This effectively avoids lattice damage and side effects caused by ion implantation, minimizing material damage. It also avoids substrate damage and contamination that may be caused by charged particle beams (such as ion beams) during processing. This invention is particularly suitable for processing novel quantum materials and two-dimensional material devices that are sensitive to damage, ensuring the electrical properties of the underlying material.

[0019] 5. The soft X-ray lithography technology and novel aZIF photoresist used in this invention are highly consistent with the B-EUVL technology route that is of great interest in the global semiconductor field. The technology is highly forward-looking and provides feasible technical reserves and process verification for the next generation of smaller linewidth chip manufacturing in my country. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the extremely fine lines generated by etching a gold mask from the side in the method of the present invention; Figure 2 This is an image of a silicon nitride substrate after gold plating in the method of this invention; Figure 3 This is a schematic diagram of a nano-fine line structure based on soft X-rays obtained by the method of the present invention; Figure 4 This is a magnified schematic diagram of a single ultrafine nanowire structure based on soft X-rays obtained by the method of this invention. Detailed Implementation

[0022] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The inventors of this application have discovered through long-term research that, currently, in the field of nanoscale manufacturing, extreme ultraviolet (EUV) lithography and electron beam lithography are the mainstream technologies for fabricating high-resolution patterns. However, EUV lithography has extremely high requirements for the perfection of the photomask and is very expensive; while electron beam lithography offers high resolution, it is inefficient and cannot meet the needs of large-scale production.

[0025] In their preliminary inventive design, the inventors of this application discovered that synchrotron radiation lithography, particularly the technology employing the 13.5 nm extreme ultraviolet / soft X-ray band, offers new possibilities for nanofabrication. Because this technology features high photon energy and strong penetrability, it is insensitive to minute defects in photomasks, which helps reduce process costs and improve yield.

[0026] However, during further in-depth research, the inventors discovered that efficiently applying synchrotron radiation lithography to the fabrication of metal nanolines below 10 nanometers and solving a series of process challenges such as mask fabrication and pattern transfer remains a technological bottleneck that needs to be overcome.

[0027] The materials and equipment used in this invention are shown in Table 1 below: Table 1 A soft X-ray lithography process includes the following steps: (1) Preparation of test mask: On the hollowed-out silicon nitride substrate, an initial nanopattern with a high aspect ratio is prepared by electron beam lithography (electron beam exposure system) and reactive ion etching. A gold mask with a gold absorption layer pattern (with sufficient absorption rate for soft X-rays) is formed by electroplating or physical vapor deposition of high atomic number metals (such as gold and tungsten) using multi-gun electron beam parallel direct writing technology. Alternatively, a gold mask on the silicon nitride substrate is formed by direct writing on the gold film using a focused ion beam. Finally, a test mask is prepared with a substrate of 2-inch diameter silicon nitride wafer. The initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 3nm to 50nm. (2) Preparation of coated silicon nitride substrate: A silicon nitride substrate with a thickness of 200 nm was selected as the support substrate. A novel amorphous zeolite imidazole ester skeleton film (aZIF) was spin-coated on the substrate as a photoresist to obtain a coated silicon nitride substrate. This material is sensitive to soft X-rays and its thickness can be controlled in the range of tens to hundreds of nanometers by spin-coating technology, and it has excellent uniformity. The specific steps of preparing the silicon nitride substrate include: using a 2-inch diameter single-crystal silicon wafer as the substrate, employing a low-pressure chemical vapor deposition process, introducing silane and ammonia as reaction gases, and reacting and depositing a silicon nitride thin film at a temperature of 700–800°C; then using electron beam evaporation or magnetron sputtering technology, sequentially depositing a titanium adhesion layer with a thickness of 2–3 nm and a gold mask layer with a thickness of 95–105 nm on the surface of the silicon nitride thin film to form a metal mask structure with a thickness of 200 nm and a length of 2 inches, thereby obtaining the silicon nitride substrate; the photoresist is an amorphous zeolite imidazole ester framework thin film with a thickness of 100 nm, a ZIF photoresist; (3) Soft X-ray exposure: The test mask prepared in step (1) and the coated silicon nitride substrate prepared in step (2) are placed in close contact and aligned in a white light synchrotron radiation source with a light source of 1-2 keV. Soft X-rays with a wavelength of about 0.1 nm to 1 nm are used for exposure, and the exposure dose is 10 to 900 mJ / cm. 2 The aZIF photoresist is produced at a very low volume; the exposure time is extremely short, requiring only a few seconds. (4) Development: The aZIF photoresist exposed in step (3) is developed using a developer to clearly transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Pattern transfer: Using the nanoline pattern developed in step (4) as a mask, the pattern is further transferred to the underlying silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (6) Metallization: Using electron beam evaporation technology, a titanium layer with a thickness of 2 nm is deposited on the silicon nitride substrate that has received the transfer pattern in step (5) as an adhesion layer, followed by the deposition of a gold layer with a thickness of 95-105 nm. (7) Lifting: Using the lift-off technique, excess photoresist and metal attached to the silicon nitride substrate with deposited titanium and gold layers are removed, and finally a gold nanoline structure with a linewidth of 10-20 nm is obtained on the silicon nitride substrate, and a gold nanoline array with a linewidth of 3-20 nm and good uniformity is obtained based on soft X-rays.

[0028] Example 1 A soft X-ray lithography process includes the following steps: (1) Preparation of test mask: On a hollow, 2-inch, 200nm thick silicon nitride substrate, an initial nanopattern with a high aspect ratio is etched by electron beam lithography and reactive ion etching. The initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 50nm. Then, the parallel direct writing technology of the electron beam exposure system is combined with electroplating or physical vapor deposition process to directly write a gold absorption layer pattern with sufficient absorption rate for soft X-rays, forming a zone plate structure with an outermost ring width of 25nm, and thus preparing the test mask. (2) Preparation of coated silicon nitride substrate: A layer of aZIF photoresist with a thickness of 100 nm and an amorphous zeolite imidazole ester framework film is spin-coated on another hollow, 2-inch, 200 nm thick silicon nitride substrate to obtain coated silicon nitride substrate. The specific steps of the preparation method of silicon nitride substrate include: using a single crystal silicon wafer with a diameter of 2 inches as a substrate, using a low-pressure chemical vapor deposition process, introducing silane and ammonia as reaction gases, reacting and depositing at a temperature of 700°C to form a silicon nitride thin film, and then using electron beam evaporation or magnetron sputtering technology to sequentially deposit a titanium adhesion layer with a thickness of 3 nm and a gold mask layer with a thickness of 105 nm on the surface of the silicon nitride thin film to form a metal mask structure with a thickness of 200 nm and a length of 2 inches, thereby obtaining the silicon nitride substrate; (3) Soft X-ray exposure: The test mask prepared in step (1) and the coated silicon nitride substrate prepared in step (2) are placed in close contact and aligned in a 1-2 keV white light synchrotron radiation source, with a wavelength of about 0.1 nm and an exposure dose of 900 mJ / cm. 2 Exposure to a large-scale soft X-ray yields aZIF photoresist; (4) Development: The aZIF photoresist exposed in step (3) is developed using a developer to clearly transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Pattern transfer: Using the nanoline pattern developed in step (4) as a mask, the pattern is further transferred to the underlying silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (6) Metallization: Using electron beam evaporation technology, a titanium layer with a thickness of 2 nm is deposited on the silicon nitride substrate that has received the transfer pattern in step (5) as an adhesion layer, followed by the deposition of a gold layer with a thickness of 95 nm. (7) Lifting: Using the lift-off technique, excess photoresist and metal attached to the silicon nitride substrate with deposited titanium and gold layers are removed, and finally a gold nanoline structure with a linewidth of 10 nm is obtained on the silicon nitride substrate, and a gold nanoline array with a linewidth of 3 nm and good uniformity based on soft X-rays is obtained.

[0029] Example 2 A soft X-ray lithography process includes the following steps: (1) Preparation of test mask: On a hollowed-out, 2-inch, 200nm thick silicon nitride substrate, an initial nanopattern with a high aspect ratio is etched using electron beam lithography and reactive ion etching. The initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 50nm. Then, using a parallel direct writing technique of electron beam exposure system combined with electroplating or physical vapor deposition process, a gold absorption layer pattern with sufficient absorption rate for soft X-rays is directly written on it to form a zone plate structure with an outermost ring width of 25nm. Finally, a test mask is made with a substrate of 2-inch diameter silicon nitride wafer; the initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 3nm. (2) Preparation of coated silicon nitride substrate: Another hollow, 2-inch, 200nm thick silicon nitride substrate was selected as the support substrate. A novel amorphous zeolite imidazole ester skeleton film (aZIF) was spin-coated on the substrate as a photoresist to obtain the coated silicon nitride substrate. This material is sensitive to soft X-rays and its thickness can be controlled in the range of tens to hundreds of nanometers by spin-coating technology, and it has excellent uniformity. The specific steps of the preparation method of silicon nitride substrate include: using a single crystal silicon wafer with a diameter of 2 inches as a substrate, using a low-pressure chemical vapor deposition process, introducing silane and ammonia as reaction gases, reacting and depositing at a temperature of 800°C to form a silicon nitride thin film, and then using electron beam evaporation or magnetron sputtering technology to sequentially deposit a titanium adhesion layer with a thickness of 2 nm and a gold mask layer with a thickness of 95 nm on the surface of the silicon nitride thin film to form a metal mask structure with a thickness of 200 nm and a length of 2 inches, thereby obtaining the silicon nitride substrate; (3) Soft X-ray exposure: The test mask prepared in step (1) and the coated silicon nitride substrate prepared in step (2) are placed in close contact and aligned in a 1-2 keV white light synchrotron radiation source, using a wavelength of about 1 nm and an exposure dose of 10 mJ / cm. 2 Exposure to a large-scale soft X-ray yields aZIF photoresist; (4) Development: The aZIF photoresist exposed in step (3) is developed using a developer to clearly transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Pattern transfer: Using the nanoline pattern developed in step (4) as a mask, the pattern is further transferred to the underlying silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (6) Metallization: Using electron beam evaporation technology, a titanium layer with a thickness of 2 nm is deposited on the silicon nitride substrate that has received the transfer pattern in step (5) as an adhesion layer, followed by the deposition of a gold layer with a thickness of 105 nm. (7) Lifting: Using the lift-off technique, excess photoresist and metal attached to the silicon nitride substrate with deposited titanium and gold layers are removed, and finally a gold nanoline structure with a linewidth of 20 nm is obtained on the silicon nitride substrate, thus producing a gold nanoline array with a linewidth of 20 nm and good uniformity based on soft X-rays.

[0030] Example 3 A soft X-ray lithography process includes the following steps: (1) Preparation of test mask: On a hollowed-out, 2-inch, 200nm thick silicon nitride substrate, an initial nanopattern with a high aspect ratio is etched using electron beam lithography and reactive ion etching. The initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 50nm. Then, using the parallel direct writing technology of the electron beam exposure system combined with electroplating or physical vapor deposition, a gold absorption layer pattern with sufficient absorption rate for soft X-rays is directly written on it to form a zone plate structure with an outermost ring width of 25nm. Finally, a test mask is made with a substrate of 2-inch diameter silicon nitride wafer. The initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 50nm. (2) Preparation of coated silicon nitride substrate: Select another hollow, 2-inch, 200nm thick silicon nitride substrate and spin-coat a 100nm thick amorphous zeolite imidazole ester skeleton film of aZIF photoresist to obtain coated silicon nitride substrate. The specific steps of the preparation method of silicon nitride substrate include: using a single crystal silicon wafer with a diameter of 2 inches as a substrate, using a low-pressure chemical vapor deposition process, introducing silane and ammonia as reaction gases, reacting and depositing at a temperature of 750°C to form a silicon nitride thin film, and then using electron beam evaporation or magnetron sputtering technology to sequentially deposit a titanium adhesion layer with a thickness of 2 nm and a gold mask layer with a thickness of 100 nm on the surface of the silicon nitride thin film to form a metal mask structure with a thickness of 200 nm and a length of 2 inches, thereby obtaining the silicon nitride substrate; (3) Soft X-ray exposure: The test mask prepared in step (1) and the coated silicon nitride substrate prepared in step (2) are placed in close contact and aligned in a 1-2 keV white light synchrotron radiation source, with a wavelength of about 0.3 nm and an exposure dose of 100 mJ / cm. 2 Exposure to a large-scale soft X-ray yields aZIF photoresist; (4) Development: The aZIF photoresist exposed in step (3) is developed using a developer to clearly transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Pattern transfer: Using the nanoline pattern developed in step (4) as a mask, the pattern is further transferred to the underlying silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (6) Metallization: Using electron beam evaporation technology, a titanium layer with a thickness of 2 nm is deposited on the silicon nitride substrate that has received the transfer pattern in step (5) as an adhesion layer, followed by the deposition of a gold layer with a thickness of 98 nm. (7) Lifting: Using the lift-off technique, excess photoresist and metal attached to the silicon nitride substrate with deposited titanium and gold layers are removed, and finally a gold nanoline structure with a linewidth of 12nm is obtained on the silicon nitride substrate, and a gold nanoline array with a linewidth of 5nm and good uniformity based on soft X-rays is obtained.

[0031] Example 4 A soft X-ray lithography process includes the following steps: (1) Preparation of test mask: On a hollowed-out, 2-inch, 200nm thick silicon nitride substrate window, an initial silicon fin structure with a period of 100nm and a linewidth of 50nm is etched out using electron beam lithography and reactive ion etching, i.e., an initial nanopattern with a high aspect ratio. Then, using the parallel direct writing technology of the electron beam exposure system combined with the electroplating deposition process of high atomic number tungsten, a gold absorption layer pattern with sufficient absorption rate for soft X-rays is directly written on it, forming a zone plate structure with an outermost ring width of 25nm. Finally, a test mask is made with a substrate of 2-inch diameter silicon nitride wafer; the initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 5nm. (2) Preparation of coated silicon nitride substrate: Select another hollow, 2-inch, 200nm thick silicon nitride substrate and spin-coat a 100nm thick amorphous zeolite imidazole ester skeleton film of aZIF photoresist to obtain coated silicon nitride substrate. (3) Soft X-ray exposure: The test mask prepared in step (1) and the coated silicon nitride substrate prepared in step (2) are placed in close contact and aligned in a 1-2 keV white light synchrotron radiation source, with a wavelength of about 0.8 nm and an exposure dose of 800 mJ / cm. 2 Exposure to a large-scale soft X-ray yields aZIF photoresist; (4) Development: The aZIF photoresist exposed in step (3) is developed using a developer to clearly transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Pattern transfer: Using the nanoline pattern developed in step (4) as a mask, the pattern is further transferred to the underlying silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (6) Metallization: Using electron beam evaporation technology, a titanium layer with a thickness of 2 nm is deposited on the silicon nitride substrate that has received the transfer pattern in step (5) as an adhesion layer, followed by the deposition of a gold layer with a thickness of 102 nm. (7) Lifting: Using the lift-off technique, excess photoresist and metal attached to the silicon nitride substrate with deposited titanium and gold layers are removed, and finally a gold nanoline structure with a linewidth of 18 nm is obtained on the silicon nitride substrate, thus producing a gold nanoline array with a linewidth of 18 nm and good uniformity based on soft X-rays.

[0032] Example 5 A soft X-ray lithography process includes the following steps: (1) Preparation of test mask: On the hollowed-out silicon nitride substrate, an initial nanopattern with a high aspect ratio is prepared by electron beam lithography (electron beam exposure system) and reactive ion etching technology. Using multi-gun electron beam parallel direct writing technology, combined with physical vapor deposition process of high atomic number gold, a gold mask with a gold absorption layer pattern (with sufficient absorption rate for soft X-rays) is formed. Finally, a test mask is prepared with a substrate of 2-inch diameter silicon nitride wafer; the initial nanopattern is an initial silicon fin structure with a period of 100nm and a linewidth of 25nm. (2) Preparation of coated silicon nitride substrate: A silicon nitride substrate with a thickness of 200 nm was selected as the support substrate. A novel amorphous zeolite imidazole ester skeleton film (aZIF) was spin-coated on the substrate as a photoresist to obtain a coated silicon nitride substrate. The photoresist is aZIF photoresist with a thickness of 100 nm and amorphous zeolite imidazole ester skeleton film. (3) Soft X-ray exposure: The test mask prepared in step (1) and the coated silicon nitride substrate prepared in step (2) are placed in close contact and aligned in a white light synchrotron radiation source with a light source of 1-2 keV. The wavelength is about 0.5 nm and the exposure dose is 500 mJ / cm. 2 Exposure to a large-scale soft X-ray yields aZIF photoresist; (4) Development: The aZIF photoresist exposed in step (3) is developed using a developer to clearly transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Pattern transfer: Using the nanoline pattern developed in step (4) as a mask, the pattern is further transferred to the underlying silicon nitride substrate by reactive ion etching technology to form a grooved silicon nitride substrate. (6) Metallization: Using electron beam evaporation technology, a titanium layer with a thickness of 2 nm is deposited on the silicon nitride substrate that has received the transfer pattern in step (5) as an adhesion layer, followed by the deposition of a gold layer with a thickness of 100 nm. (7) Lifting: Using the lift-off technique, excess photoresist and metal attached to the silicon nitride substrate with deposited titanium and gold layers are removed, and finally a gold nanoline structure with a linewidth of 15 nm is obtained on the silicon nitride substrate, and a gold nanoline array with a linewidth of 10 nm and good uniformity based on soft X-rays is obtained.

[0033] In summary, this invention utilizes electron beam lithography (EBL) + synchrotron radiation lithography (SXRL) to achieve gold nanoline structures with linewidths of 10–20 nm on a 200 nm silicon nitride substrate. The fabricated nanoscale lines exhibit both high resolution and high efficiency. Synchrotron radiation soft X-rays are used as the exposure source, with a wavelength range covering 0.1 nm to 1 nm, which offers higher theoretical resolution compared to traditional 13.5 nm extreme ultraviolet light. A multi-gun electron beam parallel direct writing system is employed to fabricate the X-ray mask, leveraging its high precision and parallel writing capability to effectively improve mask fabrication efficiency. The use of short-wavelength soft X-rays to overcome the optical diffraction limit, combined with multi-gun electron beam parallelism, significantly improves fabrication efficiency while maintaining nanoscale resolution.

[0034] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical preparation methods, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An advanced photolithography process based on soft X-rays, characterized in that, Includes the following steps: (1) Preparation of test mask and coated silicon nitride substrate: A gold mask with a gold absorption layer pattern is directly written on a silicon nitride substrate to prepare the test mask; A layer of photoresist is spin-coated onto another silicon nitride substrate to obtain a photoresist-coated silicon nitride substrate. (2) Soft X-ray exposure: The test mask from step (1) is closely aligned with the coated silicon nitride substrate in a synchrotron radiation source and exposed using soft X-rays; (3) Development: The photoresist exposed in step (2) is developed using a developer to transfer the pattern on the test mask onto the photoresist, forming a clear nanoline pattern; (5) Metallization: Using electron beam evaporation technology, an adhesion layer and a gold layer are sequentially deposited on the photoresist with grooves in step (3). After being processed by a stripping process, the nano-fine line gold mask structure is obtained on the silicon nitride substrate.

2. The preparation method according to claim 1, characterized in that, In step (1), the direct writing is a gold mask on which an initial nanopattern is etched on a silicon nitride substrate using electron beam lithography and reactive ion etching, and a gold absorption layer pattern is directly written on it, or a gold mask on a silicon nitride substrate is formed by direct writing on a gold film using a focused ion beam.

3. The preparation method according to claim 2, characterized in that, The initial nanopattern is an initial silicon fin structure with a period of 100 nm and a linewidth of 3 nm to 50 nm.

4. The preparation method according to claim 1, characterized in that, In step (1), the gold absorption layer pattern is prepared by using an electron beam exposure system with parallel direct writing technology combined with electroplating or physical vapor deposition processes.

5. The preparation method according to claim 1, characterized in that, In step (1), the test mask substrate is a 2-inch diameter, nitrided silicon wafer.

6. The preparation method according to claim 1, characterized in that, In step (1), the method for preparing the silicon nitride substrate specifically includes the following steps: using a single crystal silicon wafer with a diameter of 2 inches as a substrate, a low-pressure chemical vapor deposition process is adopted, silane and ammonia are introduced as reaction gases, and a silicon nitride thin film is formed by reaction deposition at a temperature of 700-800°C. Then, an electron beam evaporation or magnetron sputtering technique is used to sequentially deposit a titanium adhesion layer with a thickness of 2-3 nm and a gold mask layer with a thickness of 95-105 nm on the surface of the silicon nitride thin film to form a metal mask structure with a thickness of 200 nm and a length of 2 inches, thereby obtaining the silicon nitride substrate.

7. The preparation method according to claim 1, characterized in that, In step (1), the photoresist is an aZIF photoresist with a thickness of 100 nm and an amorphous zeolite imidazole ester framework film.

8. The preparation method according to claim 1, characterized in that, In step (2), the wavelength of the soft X-ray is 0.1 nm to 1 nm, and the exposure dose is 10 to 900 mJ / cm². 2 The magnitude is [not specified]; the synchrotron radiation source is 1-2 keV white light.

9. The preparation method according to claim 1, characterized in that, In step (5), the adhesion layer is a titanium layer with a thickness of 2 nm, and the gold layer has a thickness of 95-105 nm.

10. The preparation method according to claim 1, characterized in that, In step (5), the nano-fine lines are gold nanowire arrays with a linewidth of 3 to 20 nm and good uniformity.

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