Laser accelerator and preparation method thereof
By using doped diamond crystals as the substrate material and forming micropillars and positioning structures through photolithography and etching techniques, the problem of poor stability of dielectric laser accelerators during long-term use was solved, and efficient electron beam acceleration was achieved.
Patent Information
- Application Number
- CN202410887110.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-03
- Publication Date
- 2026-01-06
AI Technical Summary
Existing dielectric laser accelerators suffer from poor stability and inability to excite high energies due to damage or shedding of conductive materials during long-term use.
By using doped diamond crystals as the substrate material, micropillars, positioning structures, and mesa structures are formed on the substrate through photolithography and etching techniques, forming channels for accelerating electron beams and avoiding the step of additional coating of conductive materials.
This improves the stability and acceleration effect of the laser accelerator, ensuring that high-energy electron beams can be continuously excited during long-term use.
Smart Images
Figure CN121284820A_ABST
Abstract
Description
[Technical Field]
[0001] This disclosure relates to the field of laser accelerator technology, and in particular to a laser accelerator and its fabrication method. [Background Technology]
[0002] Dielectric laser accelerators (DLAs), as an emerging particle accelerator technology, utilize the interaction between laser pulses and dielectrics to generate high-intensity electric field gradients, thereby accelerating charged electrons. DLAs have broad application prospects in particle physics research and medical imaging technology, and can also be used in micro / nanostructure fabrication, surface modification, and device function modulation, thus promoting the development of photolithography technology and expanding its application areas. Traditional large-scale accelerators are limited by factors such as size and cost, while DLAs, with their advantages of compactness, high efficiency, and low cost, have attracted much attention.
[0003] However, existing dielectric laser accelerators typically use silicon or doped silicon as the main substrate material during their fabrication, and a conductive material needs to be coated on the substrate. Over time, this conductive material can be damaged or detached. Once the conductive material is damaged or detached, the laser accelerator will exhibit poor stability and be unable to excite high energies during long-term use. [Summary of the Invention]
[0004] To address the problem that laser accelerators prepared by existing methods suffer from poor stability and inability to excite high energies during long-term use, this disclosure provides a laser accelerator and its preparation method.
[0005] To solve the above-mentioned technical problems, this disclosure provides the following technical solution: a method for fabricating a laser accelerator, the method comprising:
[0006] Provide a doped diamond crystal raw material with electrical conductivity, and obtain a substrate by processing the raw material;
[0007] A first photoresist layer is disposed on one side of the substrate. Corresponding to the first region of the substrate, the first photoresist layer is subjected to a first photolithography so that a portion of the first photoresist layer is penetrated to form a first trench.
[0008] The side of the substrate near the first trench is etched to form spaced micropillars and positioning structures on the side of the substrate near the first photoresist layer.
[0009] A second photoresist layer is formed on one side of the substrate where the micropillars and positioning structure are formed. Corresponding to the second region of the substrate, the second photoresist layer is subjected to a second photolithography so that part of the second photoresist layer is penetrated to form a second trench.
[0010] The side of the substrate closest to the second trench is etched to form a mesa structure on the side of the substrate closest to the second photoresist layer;
[0011] The first and second photoresist layers on the substrate are removed to obtain the laser accelerator.
[0012] In this embodiment, since the substrate is made of conductive doped diamond crystal material, and the micropillars and positioning structures formed by the first photolithography and etching provide an acceleration channel with the ability to accelerate electron beams, it avoids the disadvantages of existing laser accelerators, such as poor stability and inability to excite high energy when the conductive material inside is damaged or falls off.
[0013] In some embodiments, the doped diamond crystal raw material having electrical conductivity includes:
[0014] Provide hydrogen, acetone and methanol, and mix acetone and methanol to form an organic mixture;
[0015] A diamond seed layer is provided, and the diamond seed layer is placed in a sealed reaction chamber for the first heat treatment;
[0016] An organic mixture is introduced into a reaction chamber at a first preset flow rate and hydrogen is introduced at a second preset flow rate to form a mixed gas.
[0017] A boron source is provided to perform a second heating treatment on the mixed gas and diamond seed layer in the reaction chamber. The boron source is then introduced into the reaction chamber, and a doped diamond layer is formed on the diamond seed layer using a vapor deposition method.
[0018] Remove the diamond seed layer to obtain a doped diamond crystal raw material with electrical conductivity.
[0019] This embodiment can prepare doped diamond crystal raw materials with electrical conductivity without the need for additional coating with conductive materials.
[0020] In some embodiments, the first preset flow rate is 3–20 s cm; the second preset flow rate is 100–200 s cm. In this embodiment, by adjusting the flow rate of the hydrogen and organic mixture introduced into the reaction chamber, the hydrogen can better etch the amorphous carbon phase of diamond and bond with the carbon atoms on the surface of the diamond seed layer, thereby maintaining a stable diamond structure on the surface carbon atoms.
[0021] In some embodiments, the resistivity of the doped diamond crystal raw material with conductivity is 0.01–5 ΩΩm. In this embodiment, the raw material used for the substrate is preferably a doped diamond crystal with a resistivity of 0.01–5 ΩΩm, resulting in a laser accelerator with good acceleration performance due to its high conductivity. There is no need to coat the substrate with a conductive material, as the substrate itself possesses conductive properties.
[0022] In some embodiments, obtaining a substrate by processing the raw material includes:
[0023] The doped diamond crystal raw material is cut and ground to obtain a substrate. The substrate has opposing upper and lower surfaces that are parallel to each other. This embodiment avoids the problem that if the upper and lower surfaces of the substrate are not parallel, the surface formed at the end of the micropillar and mesa structure furthest from the substrate will also be non-parallel to the upper surface of the substrate. It also reduces the difficulty of adjusting the angle of the electron beam incident on the acceleration channel.
[0024] In some embodiments, performing a first photolithography on the first photoresist layer to allow a portion of the first photoresist layer to be penetrated to form a first trench includes:
[0025] Provides an electron beam of 15kV to 125kV;
[0026] The surface of the first photoresist is exposed using an electron beam, causing a portion of the first photoresist layer to be penetrated. The exposed first photoresist layer is then placed in a pre-set developer for development for 80-90 seconds and fixing for 20-30 seconds, forming a first trench at the penetration point. The shape of the area where the first trench is not formed in the first photoresist layer is the same as the cross-sectional shape of the micropillars and positioning structures. The remaining first photoresist layer primarily serves to protect the substrate surface, allowing for direct formation of micropillars and positioning structures during subsequent etching processes, simplifying the operation.
[0027] In some embodiments, etching the side of the substrate near the first trench includes:
[0028] Carbon tetrafluoride and oxygen are provided to obtain a reaction gas. This reaction gas passes through a first trench on a first photoresist layer, etching a groove with a depth of 0.1 μm to 10 μm onto the substrate. The unetched portion of the substrate near the first photoresist layer forms micropillars and positioning structures. The formed micropillar structures are arranged in pairs on the substrate surface, forming an acceleration channel for electrons in the electron beam. The positioning structures serve as auxiliary positioning, helping to adjust the angle at which the electron beam enters the acceleration channel.
[0029] In some embodiments, performing a second photolithography on the second photoresist layer to allow a portion of the second photoresist layer to penetrate and form a second trench includes:
[0030] Provides an electron beam of 15kV to 125kV;
[0031] The surface of the second photoresist is exposed using an electron beam, causing a portion of the second photoresist layer to be penetrated. The exposed second photoresist layer is then placed in a pre-set developer for development for 140–150 seconds and fixing for 20–30 seconds, forming a second trench at the penetration point. This second trench helps reduce the size of the accelerator during subsequent etching and creates a mesa structure that facilitates the adjustment and calibration of the angle by which the electron beam enters the acceleration channel.
[0032] In some embodiments, etching the side of the substrate near the second trench includes:
[0033] Carbon tetrafluoride and oxygen are provided to obtain a reactive gas. This reactive gas passes through a second trench on a second photoresist layer, etching a groove with a depth of 20 μm to 100 μm onto the substrate. The unetched portion of the substrate near the second photoresist layer forms a mesa structure. This mesa structure helps to calibrate the angle of the electron beam entering the acceleration channel, thereby improving stability during acceleration.
[0034] To solve the above-mentioned technical problems, this disclosure provides another technical solution as follows: a laser accelerator, which is prepared by the laser accelerator preparation method described above.
[0035] To address the aforementioned technical problems, this disclosure provides another technical solution as follows: a computer device applied to the above-described laser accelerator fabrication method, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the laser accelerator fabrication method. The laser accelerator provided in this embodiment has the same beneficial effects as the above-described laser accelerator fabrication method, and will not be elaborated upon here. [Attached Image Description]
[0036] Figure 1 This is a schematic flowchart of the method for fabricating a laser accelerator provided in the first embodiment of this disclosure.
[0037] Figure 2 This is a schematic diagram of the process of providing a conductive doped diamond crystal raw material in the method for preparing a laser accelerator according to the first embodiment of this disclosure.
[0038] Figures 3a to 3h This is a flowchart illustrating the fabrication process of the laser accelerator provided in the first embodiment of this disclosure.
[0039] Explanation of reference numerals in the attached diagram:
[0040] 10. Laser accelerator;
[0041] 1. Substrate; 2. First photoresist layer; 3. Micropillar; 4. Positioning structure; 5. Second photoresist layer; 6. Mesa structure;
[0042] 21. First trench; 51. Second trench;
[0043] A1, First Region; A2, Second Region.
Detailed Implementation Methods
[0044] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this disclosure.
[0045] In the embodiments provided in this disclosure, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.
[0046] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this disclosure. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Those skilled in the art should also recognize that the embodiments described in the specification are optional embodiments, and the actions and modules involved are not necessarily essential to this disclosure.
[0047] In the various embodiments of this disclosure, it should be understood that the sequence number of each process does not necessarily imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this disclosure.
[0048] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved. It is particularly important to note that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.
[0049] Dielectric laser accelerators (DLAs), as an emerging particle accelerator technology, utilize the interaction between laser pulses and dielectrics to generate high-intensity electric field gradients, thereby accelerating charged electrons. DLAs have broad application prospects in particle physics research and medical imaging technology, and can also be used in micro / nanostructure fabrication, surface modification, and device function modulation, thus promoting the development of photolithography technology and expanding its application areas. Traditional large-scale accelerators are limited by factors such as size and cost, while DLAs, with their advantages of compactness, high efficiency, and low cost, have attracted much attention.
[0050] However, existing dielectric laser accelerators typically use silicon or doped silicon as the main substrate material during their fabrication. Because silicon or doped silicon has high resistivity, its application in dielectric laser accelerators usually requires coating the substrate with a conductive material. However, with long-term operation of the laser accelerator, this conductive material coating can be damaged or detached. Once damaged or detached, the laser accelerator suffers from poor stability during operation and is affected by the resistivity of its internal surfaces, making it unable to excite high-energy electron beams during acceleration.
[0051] Please see Figure 1 and combined Figures 3a to 3h The first embodiment of this disclosure provides a method for fabricating a laser accelerator 10, comprising:
[0052] S1, providing a doped diamond crystal raw material with electrical conductivity, and processing the raw material to obtain substrate 1;
[0053] S2, a first photoresist layer 2 is disposed on one side of the substrate 1, corresponding to the first region A1 of the substrate 1, and the first photoresist layer 2 is photolithographically etched for the first time so that a portion of the first photoresist layer 2 is penetrated to form a first trench 21;
[0054] S3, etch the side of the substrate 1 near the first trench 21 to form spaced micropillars 3 and positioning structures 4 on the side of the substrate 1 near the first photoresist layer 2;
[0055] S4, a second photoresist layer 5 is formed on one side of the substrate 1 where the micropillar 3 and the positioning structure 4 are formed. Corresponding to the second region A2 of the substrate 1, the second photoresist layer 5 is subjected to a second photolithography so that part of the second photoresist layer 5 is penetrated to form a second trench 51.
[0056] S5, etch the side of the substrate 1 near the second trench 51 to form a mesa structure 6 on the side of the substrate 1 near the second photoresist layer 5;
[0057] S6, remove the first photoresist layer 2 and the second photoresist layer 5 on the substrate 1 to obtain the laser accelerator 10.
[0058] Understandably, the method used in this embodiment differs from existing methods that use silicon or doped silicon as the main material of substrate 1. This embodiment provides a conductive doped diamond crystal raw material, which is then processed to obtain substrate 1. That is, the main material of substrate 1 is a conductive doped diamond crystal. This ensures that substrate 1 itself has a low resistivity. It should be understood that this embodiment does not require coating substrate 1 with a conductive material as in existing technologies, and avoids the problem of the conductive material breaking or falling off, which could affect the stability of the laser accelerator 10 during use.
[0059] Furthermore, after obtaining the substrate 1, a first photoresist layer 2 can be deposited on one side of the substrate 1, and the first photoresist layer 2 is subjected to a first photolithography to partially penetrate it and form a first trench 21. It should be understood that the main material of the first photoresist layer 2 is photoresist, specifically a special resin material that can react sensitively to light or other forms of radiation. It is mainly composed of three components: photosensitive resin, sensitizer, and solvent, and is a photosensitive liquid mixture. The process of performing the first photolithography on the first photoresist layer 2 to partially penetrate it and form the first trench 21 can specifically include: exposing the first photoresist layer 2 to light of a specific wavelength for a period of time, so that a pattern similar to the cross-section of the first trench 21 is formed on its surface. Then, the substrate 1, together with the first photoresist layer 2, is placed in a developing solution for development, and the residual photoresist at the patterned area is removed to expose the surface of the substrate 1, thereby forming the first trench 21. It should be understood that since the substrate 1 near the first trench 21 is not protected by photoresist, during the etching process on the side of the substrate 1 near the first trench 21, the surface of the substrate 1 without the protection of the first photoresist layer 2 will be etched into the first trench 21, while the surface of the substrate 1 protected by the first photoresist layer 2 cannot be etched, thereby forming spaced micropillars 3 and positioning structures 4.
[0060] It should be noted that the micropillars 3 are paired cylinders, and their cross-sections can be circular, elliptical, rectangular, regular hexagonal, or regular octagonal. The positioning structure 4 is also a cylinder, and its cross-section can be circular, elliptical, or an irregular polygon. It should be understood that the paired cylinders form an acceleration channel, and the positioning structures 4 are respectively provided at both ends of the acceleration channel. It should be noted that the laser accelerator 10 mainly utilizes the interaction between laser light and matter (such as electrons) to accelerate electrons. In the laser accelerator 10, laser pulses are used to generate a strong electromagnetic field, which interacts with the electron beam, exerting a force on the electrons and thus accelerating them. Therefore, the object accelerated by the laser accelerator 10 is usually an electron beam. Ideally, the angle at which the electron beam enters the acceleration channel should coincide with the axis of the acceleration channel. However, in practice, it is difficult to guarantee that the electron beam can enter the acceleration channel at the aforementioned angle. Therefore, before accelerating the electron beam, it is necessary to continuously calibrate the angle at which the electron beam enters the acceleration channel. For example, the laser accelerator 10 prepared in this embodiment can be applied in the field of photolithography. Specifically, the device is adapted to include an electron beam emission module and an identification module. The positioning structure 4 serves as a positioning aid, working in conjunction with the pre-set identification module. When the identification module identifies the positioning structure 4, it can control the emission module to adjust the electron beam emission angle, thereby controlling the angle at which the electron beam enters the acceleration channel. Specifically, the electron beam can enter the acceleration channel through the positioning structure 4, which facilitates the calibration of the electron beam's entry angle. Furthermore, after entering the acceleration channel, influenced by the laser pulse, the electron beam can be accelerated within the acceleration channel formed by the paired micropillars 3, which is simple and convenient. Additionally, it is necessary to ensure that there is a gap between the micropillars 3 and the positioning structure 4 to prevent them from contacting each other, which could lead to unsatisfactory acceleration performance in the fabricated laser accelerator 10.
[0061] Furthermore, if the micropillars 3 and positioning structures 4 have already been formed, a second photoresist layer 5 can be formed on one side of the substrate 1 where the micropillars 3 and positioning structures 4 are formed. A second photolithography process is then performed on the second photoresist layer 5 to allow a portion of the second photoresist layer 5 to penetrate and form a second trench 51. It should be understood that the main material of the second photoresist layer 5 is the same as that of the first photoresist layer 2, and therefore will not be elaborated upon here. It should be noted that before forming the second photoresist layer 5, the first photoresist layer 2 can be completely removed, or it can remain intact. If the latter is chosen, the second photoresist layer 5 will cover the first photoresist layer 2. Additionally, the first region A1 and the second region A2 of the substrate 1 refer to specific locations on the surface of the substrate 1. The first region A1 of the substrate 1 includes at least the location where the micropillars 3 and positioning structures 4 are located. The second region A2 of the substrate 1 does not include the location where the micropillars 3 and positioning structures 4 are located. That is, the first region A1 may not include the second region A2 at all, or it may include a portion of the location within the second region A2. It should be understood that the position of the platform structure 6 on the base 1 is different from the position of the micro-pillar 3 and the positioning structure 4 on the base 1. Therefore, the positions formed by the first groove 21 and the second groove 51 should also be different.
[0062] Specifically, the process of forming the second trench 51 may include: exposing the second photoresist layer 5 to the second region A2 of the substrate 1, avoiding the micropillars 3 and the positioning structure 4, using light of a specific wavelength, for a period of time, so that a pattern similar to the cross-section of the second trench 51 is formed on its surface. It should be noted that since the micropillars 3 and the positioning structure 4 need to be avoided in the subsequent etching process, the first photoresist layer 2 needs to be removed in the second photolithography process. Further, the substrate 1 together with the second photoresist layer 5 is placed in a developer for development, and the residual photoresist at the patterned area is removed to expose the surface of the substrate 1 to form the second trench 51. It should be understood that since the substrate 1 near the second trench 51 is not protected by photoresist, during the etching process on the side of the substrate 1 near the second trench 51, the surface of the substrate 1 without the protection of the second photoresist layer 5 will be etched into the second trench 51, while the surface of the substrate 1 protected by the second photoresist layer 5 cannot be etched, thus forming the mesa structure 6. For example, in this embodiment, the pre-set identification module first identifies the platform structure 6 before the electron beam enters the positioning structure 4, and then calibrates the angle at which the electron beam enters the positioning structure 4. This helps to calibrate the angle at which the electron beam enters the acceleration channel, thereby improving the stability during the acceleration process.
[0063] Further, by removing the remaining first photoresist layer 2 and second photoresist layer 5 on the substrate 1, the laser accelerator 10 can be obtained. The laser accelerator 10 prepared using the method provided in this embodiment eliminates the need for an additional conductive layer during fabrication, saving process steps, while still achieving good acceleration performance. Furthermore, by setting micropillars 3 and positioning structures 4 in this embodiment, the electron beam can enter the acceleration channel through the positioning structures 4, facilitating the calibration of the electron beam's entry angle into the acceleration channel. After entering the acceleration channel, the electron beam, influenced by the laser pulse, can complete acceleration within the acceleration channel formed by the paired micropillars 3, resulting in a stable and efficient acceleration process. Moreover, in this embodiment, since the substrate 1 is made of conductive doped diamond crystal material, and the micropillars 3 and positioning structures 4 formed by the first photolithography and etching provide an acceleration channel capable of accelerating the electron beam, the laser accelerator 10 avoids the shortcomings of existing laser accelerators 10, such as poor stability and inability to excite high energies due to damage or detachment of the internal conductive material.
[0064] In some embodiments, please refer to the following: Figure 2 In step S1 above, the doped diamond crystal raw material with electrical conductivity includes:
[0065] S11 provides hydrogen, acetone and methanol, and mixes acetone and methanol to form an organic mixture;
[0066] S12 provides a diamond seed layer, which is then placed in a sealed reaction chamber for the first heat treatment.
[0067] S13, the organic mixture is introduced into the reaction chamber at a first preset flow rate and hydrogen is introduced at a second preset flow rate to form a mixed gas;
[0068] S14 provides a boron source to perform a second heating treatment on the mixed gas and diamond seed layer in the reaction chamber. Then, the boron source is introduced into the reaction chamber, and a doped diamond layer is formed on the diamond seed layer by vapor deposition.
[0069] S15, remove the diamond seed layer to obtain a doped diamond crystal raw material with electrical conductivity.
[0070] Understandably, existing technologies typically use silicon or doped silicon as the main material of the substrate 1. However, in the fabrication of the laser accelerator 10, an additional step of coating the laser accelerator surface with a conductive material is required, which is complex and carries the risk of damage or detachment of the coated conductive material. In this embodiment, acetone and methanol are first mixed to form an organic mixture. A diamond seed layer, made of diamond, is placed in a sealed reaction chamber for a first heating treatment. It should be noted that the organic mixture of acetone and methanol is a carbon source, and its role is to change the diamond particle size and crystal orientation by adjusting the secondary nucleation process. The diamond seed layer refers to the diamond seed crystal, which is the starting point for growth. The diamond seed layer is placed in a sealed reaction chamber and heated until its temperature stabilizes at 750–850°C. In some embodiments, the organic mixture is introduced into the reaction chamber at a first preset flow rate, and hydrogen is introduced at a second preset flow rate to form a mixed gas, wherein the first preset flow rate is 3–20 s cm⁻¹, and the second preset flow rate is 100–200 s cm⁻¹. The pressure within the reaction chamber during the mixing process is 4 × 10⁻³ Pa. Further, the mixed gas and diamond seed layer within the reaction chamber undergo a second heating treatment to stabilize the internal temperature to 2000℃–2400℃. It should be understood that the role of hydrogen is to etch the amorphous carbon phase of the diamond, forming bonds with carbon atoms on the surface of the diamond seed layer, thus maintaining a stable diamond structure. Hydrogen atoms can also react with small diamond nuclei, promoting diamond nucleation. The reaction temperature is between 2000-2400℃, hence the second heating. After heating, a boron source, such as boron trioxide (B₂O₃), is introduced into the reaction chamber, and a doped diamond layer is formed on the diamond seed layer using vapor deposition. Finally, the diamond seed layer is removed to obtain a conductive doped diamond crystal raw material.
[0071] Furthermore, a conductive doped diamond crystal raw material can be obtained and used to fabricate substrate 1. Specifically, a laser cutting method can be used to cut the opposite sides of the grown doped diamond crystal raw material, giving it a relatively parallel upper surface and lower surface. The entire piece is then placed on a grinding machine and ground to give the raw material a flat and smooth surface. Further, after grinding, it can be ultrasonically cleaned sequentially with deionized water and ethanol for 20 minutes at a cleaning temperature of 30°C. After cleaning, it can be air-dried to obtain substrate 1.
[0072] In some embodiments, the resistivity of the doped diamond crystal raw material with conductivity is 0.01–5 ΩΩm. In this embodiment, the raw material used for the substrate 1 is preferably a doped diamond crystal with a resistivity of 0.01–5 ΩΩm. Laser accelerator 10 prepared with high conductivity exhibits good acceleration performance. There is no need to coat the substrate 1 with a conductive material, as the substrate 1 itself possesses conductive properties. The preparation method of laser accelerator 10 provided in this embodiment saves the process step of coating with a conductive material, and the prepared laser accelerator 10 still possesses good acceleration performance.
[0073] It should be noted that during the preparation of substrate 1, a four-probe resistivity meter can be used to measure the resistivity of substrate 1 until a substrate with a resistivity of 0.01–5 ΩΩm is selected. An ellipsometer is then used to measure the refractive index of the diamond substrate 1 and calculate its dielectric constant.
[0074] In some embodiments, obtaining substrate 1 by processing the raw material includes:
[0075] A substrate 1 is obtained by cutting and grinding a doped diamond crystal raw material. The substrate 1 has opposing upper and lower surfaces that are parallel to each other. It should be understood that the lower surface of the substrate 1 directly contacts the mesa during the subsequent formation of the micropillars 3 and the positioning structure 6. If its upper and lower surfaces are not parallel, the surface formed at the end of the micropillars 3 and the mesa structure 6 furthest from the substrate 1 will also not be parallel to the upper surface of the substrate 1. This will increase the difficulty of adjusting the angle of the electron beam incident on the acceleration channel, resulting in poor electron beam acceleration.
[0076] In some embodiments, in step S2 above, forming a first photoresist layer 2 on one side of the substrate 1 includes: using a spin coater, setting the spin coater speed to 2500 rpm, for example, uniformly coating PMMAA 4 photoresist onto the upper surface of the substrate 1 to form the first photoresist layer 2, and placing the substrate 1 together with the first photoresist layer 2 on a hot plate and baking it at 90°C for 3 minutes.
[0077] In some embodiments, performing a first photolithography on the first photoresist layer 2 to allow a portion of the first photoresist layer 2 to be penetrated to form the first trench 21 includes:
[0078] Provides an electron beam of 15kV to 125kV;
[0079] The surface of the first photoresist is exposed by an electron beam, so that part of the first photoresist layer 2 is penetrated. The exposed first photoresist layer 2 is then placed in a preset developing solution for development for 80-90 seconds and fixing for 20-30 seconds, so that the first groove 21 is formed at the penetration point of the first photoresist layer 2.
[0080] Understandably, the shape of the first photoresist layer 2 where the first trench 21 is not formed is the same as the cross-sectional shape of the micropillar 3 and the positioning structure 4, and the remaining first photoresist layer 2 is mainly to protect the surface of the substrate 1 so that the micropillar 3 and the positioning structure 4 can be formed in the subsequent etching process.
[0081] In some embodiments, in step S3 above, etching the side of the substrate 1 near the first trench 21 includes:
[0082] Carbon tetrafluoride and oxygen are provided to obtain a reaction gas based on carbon tetrafluoride and oxygen. The reaction gas passes through the first trench 21 on the first photoresist layer 2 and is etched on the substrate 1 to form a groove with a depth of 0.1μm to 10μm. The unetched part of the substrate 1 near the first photoresist layer 2 forms a micropillar 3 and a positioning structure 4.
[0083] For example, a radio frequency power of 150-300W can be used, with carbon tetrafluoride (CF4) and oxygen (O2) as the reaction gases, to etch a substrate 1 without the protection of the first photoresist layer 2, to a depth of 1 μm. The unetched portion of the substrate 1 forms micropillars 3 and positioning structures 4, with a height of 1 μm. It should be noted that the height of the micropillars 3 and positioning structures 4 is 0.1 μm to 10 μm. It should be understood that the height of the micropillars 3 and positioning structures 4 needs to be greater than the diameter of the electrons in the electron beam to ensure that the electrons can move and be accelerated within the acceleration channels formed by the paired micropillars 3.
[0084] In step S4 above, forming a second photoresist layer 5 on one side of the substrate 1 includes: using a spin coater, setting the spin coater speed to 2500 rpm, for example, uniformly coating PMMAA 7 photoresist onto the upper surface of the substrate 1 to form the second photoresist layer 5. The substrate 1 along with the second photoresist layer 5 is then placed on a hot plate and baked at 90°C for 3 minutes.
[0085] In some embodiments, performing a second photolithography on the second photoresist layer 5 to allow a portion of the second photoresist layer 5 to penetrate and form the second trench 51 includes:
[0086] Provides an electron beam of 15kV to 125kV;
[0087] The surface of the second photoresist is exposed using an electron beam, causing a portion of the second photoresist layer 5 to be penetrated. The exposed second photoresist layer 5 is then placed in a pre-set developing solution for 140–150 seconds of development and 20–30 seconds of fixing, forming a second trench 51 at the penetration point. It should be understood that during the second photolithography process, because the cross-sectional area of the mesa structure 6 is larger than the sum of the cross-sectional areas of the micropillars 3 and the positioning structure 4, its development process takes longer to ensure a clear outline of the mesa structure 6.
[0088] In some embodiments, in step S5 above, etching the side of the substrate 1 near the second trench 51 includes:
[0089] Carbon tetrafluoride and oxygen are provided to obtain a reaction gas based on carbon tetrafluoride and oxygen. The reaction gas passes through the second trench 51 on the second photoresist layer 5 and is etched on the substrate 1 to form a groove with a depth of 20μm to 100μm. The unetched part of the substrate 1 near the second photoresist layer 5 forms a mesa structure 6.
[0090] For example, a radio frequency power of 150-300W can be used with carbon tetrafluoride (CF4) and oxygen (O2) as the reaction gases to etch a substrate 1 without the protection of the first photoresist layer 2 to a depth of 1μm. The unetched portion of the substrate 1 forms micropillars 3 and positioning structures 4, with a height of 50μm. It should be noted that the height of the micropillars 3 and positioning structures 4 is 20μm to 100μm. It should be understood that since the substrate 1 near the second trench 51 is not protected by photoresist, during the etching process on the side of the substrate 1 near the second trench 51, the surface of the substrate 1 without the protection of the second photoresist layer 5 will be etched with grooves corresponding to the second trench 51, while the surface of the substrate 1 protected by the second photoresist layer 5 cannot be etched, thus forming a mesa structure 6. The mesa structure 6 formed in this embodiment helps to calibrate the angle of the electron beam entering the acceleration channel, thereby improving stability during acceleration.
[0091] In step S6 above, the substrate 1, which has completed the second etching, is sequentially immersed in acetone and isopropanol to remove residual photoresist, thus completing the fabrication of the dielectric laser accelerator 10.
[0092] For example, please refer to the following in sequence. Figures 3a to 3h . Figures 3a to 3hThe fabrication method of the laser accelerator 10 is shown in sequence. First, a conductive doped diamond crystal raw material is provided and cut to obtain a substrate 1. A first photoresist layer 2 is formed on one side of the substrate 1. Corresponding to the first region A1 of the substrate 1, the first photoresist layer 2 is subjected to a first photolithography using an electron beam, so that part of the first photoresist layer 2 is penetrated to form a first trench 21. Then, carbon tetrafluoride and oxygen are used as reactant gases to etch the surface of the substrate 1 through the first trench 21 to obtain micropillars 3 and positioning structures 4. Further, the first photoresist layer 2 is removed, and a second photoresist layer 5 is formed. The second photoresist layer 5 is subjected to a second photolithography corresponding to the second region A2 of the substrate 1, so that part of the second photoresist layer 5 is penetrated to form a second trench 51. Then, carbon tetrafluoride and oxygen are used as reactant gases to etch the surface of the substrate 1 through the first trench 21 to obtain a mesa structure 6. The second photoresist layer 5 is removed to obtain the laser accelerator 10.
[0093] The second embodiment of this disclosure also provides a laser accelerator 10, which is prepared by the laser accelerator 10 preparation method described above.
[0094] This embodiment provides a laser accelerator 10, which, after acceleration, can be used as a light source in photolithography. Specifically, the electron beam accelerated by the accelerator has a shorter wavelength and is directly used as a light source for direct-write photolithography, irradiating the photoresist to modify it and form smaller patterns.
[0095] The above provides a detailed description of a laser accelerator and its fabrication method disclosed in the embodiments of this disclosure. Specific examples have been used to illustrate the principles and implementation methods of this disclosure. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this disclosure. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this disclosure. Therefore, the content of this specification should not be construed as a limitation of this disclosure. Any modifications, equivalent substitutions, and improvements made within the principles of this disclosure should be included within the protection scope of this disclosure.
Claims
1. A method of producing a laser accelerator, characterized by, The method comprises: providing a doped diamond crystal raw material with electric conductivity, and processing the raw material to obtain a substrate (1); a first photoresist layer (2) is arranged on one side of the substrate (1) corresponding to a first region (A1) of the substrate (1), and first photoetching is performed on the first photoresist layer (2) to form a first groove (21) by penetrating part of the first photoresist layer (2); the side of the substrate (1) close to the first groove (21) is etched to form micro columns (3) and positioning structures (4) on the side of the substrate (1) close to the first photoresist layer (2); a second photoresist layer (5) is arranged on the side of the substrate (1) where the micro columns (3) and the positioning structures (4) are formed, corresponding to a second region (A2) of the substrate (1), and second photoetching is performed on the second photoresist layer (5) to form a second groove (51) by penetrating part of the second photoresist layer (5); the side of the substrate (1) close to the second groove (51) is etched to form a mesa structure (6) on the side of the substrate (1) close to the second photoresist layer (5); the first photoresist layer (2) and the second photoresist layer (5) on the substrate (1) are removed to obtain a laser accelerator (10).
2. The method of claim 1, wherein: The method comprises: hydrogen, acetone and methanol are provided, and the acetone and the methanol are mixed to form an organic mixture; a diamond seed layer is provided, and the diamond seed layer is placed in a closed reaction chamber for first heating treatment; the organic mixture is introduced into the reaction chamber at a first preset flow rate, and the hydrogen is introduced into the reaction chamber at a second preset flow rate to form a mixed gas; a boron source is provided, and the mixed gas and the diamond seed layer in the reaction chamber are subjected to second heating treatment, and then the boron source is introduced into the reaction chamber, and a doped diamond layer is formed on the diamond seed layer by using a vapor deposition method; the diamond seed layer is removed to obtain a doped diamond crystal raw material with electric conductivity.
3. The method of claim 2, wherein: The first preset flow rate is 3-20 sccm, and the second preset flow rate is 100-200 sccm.
4. The method of claim 2, wherein: The doped diamond crystal raw material with electric conductivity has a resistivity of 0.01-5 Ω· Ωm.
5. The method of claim 1, wherein: The method comprises: the doped diamond crystal raw material is cut and ground to obtain the substrate (1), and the substrate (1) has opposite upper and lower surfaces which are parallel to each other.
6. The method of claim 1, wherein: The method comprises: an electron beam with a voltage of 15 kV-125 kV is provided; Exposing the surface of the first photoresist layer to the electron beam so that part of the first photoresist layer (2) is penetrated, and placing the exposed first photoresist layer (2) in a preset developing solution for developing for 80-90 seconds and fixing for 20-30 seconds, so that the first trench (21) is formed at the penetrated part of the first photoresist layer (2).
7. The method of claim 6, wherein: The etching of the side of the substrate (1) close to the first trench (21) comprises: Carbon tetrafluoride and oxygen are provided, and a reaction gas is obtained based on the carbon tetrafluoride and the oxygen, the reaction gas passes through the first trench (21) on the first photoresist layer (2), and a groove with a depth of 0.1-10 μm is etched on the substrate (1), and the part of the substrate (1) close to the first photoresist layer (2) which is not etched forms the micro column (3) and the positioning structure (4).
8. The method of claim 1, wherein: The second photoresist layer (5) is subjected to a second photoetching to penetrate part of the second photoresist layer (5) to form the second trench (51) comprises: An electron beam with a voltage of 15-125 kV is provided. Exposing the surface of the second photoresist layer to the electron beam so that part of the second photoresist layer (5) is penetrated, and placing the exposed second photoresist layer (5) in a preset developing solution for developing for 140-150 seconds and fixing for 20-30 seconds, so that the second trench (51) is formed at the penetrated part of the second photoresist layer (5).
9. The method of claim 8, wherein: The etching of the side of the substrate (1) close to the second trench (51) comprises: Carbon tetrafluoride and oxygen are provided, and a reaction gas is obtained based on the carbon tetrafluoride and the oxygen, the reaction gas passes through the second trench (51) on the second photoresist layer (5), and a groove with a depth of 20-100 μm is etched on the substrate (1), and the part of the substrate (1) close to the second photoresist layer (5) which is not etched forms the mesa structure (6).
10. A laser accelerator characterized by: The laser accelerator (10) is prepared by the preparation method of the laser accelerator according to any one of claims 1-9.