Method for manufacturing cathode conductive substrate of gated image intensifier based on nanoimprint technology

Abstract

The invention relates to the technical field of manufacturing a cathode conductive base of an image intensifier, and discloses a manufacturing method of a cathode conductive base of a gated image intensifier based on nanoimprint technology. The manufacturing method comprises the following process steps: S1: plating a metal conductive base film layer on the substrate surface of a cathode window; S2: then dripping nanoimprint ultraviolet curing glue on the surface of the metal conductive base film layer and coating it evenly to form an ultraviolet curing glue layer; S3: closely fitting an imprinting mold on the surface of the ultraviolet curing glue layer and slowly pressing the ultraviolet curing glue layer to form a combination; S4: uniformly irradiating the combination with ultraviolet light, removing the imprinting mold after the ultraviolet curing glue is cured, and forming an imprinting curing glue layer on the surface of the metal conductive base film layer; the metal conductive base manufactured by the invention can effectively reduce the effective resistance of the cathode, reduce the RC time constant between the cathode and the MCP input surface, and reduce the exposure time of the gated image intensifier to less than 3 nanoseconds or even below sub-nanoseconds.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing a cathode conductive base of an image intensifier, and in particular to a manufacturing method of a cathode conductive base of a gated image intensifier based on a nano-imprinting technology. Background Art

[0002] Gated image intensifiers have nanosecond or even sub-nanosecond time resolution and micron-level spatial resolution. As a core time-space resolution imaging detection device, it is widely used in biomedicine, materials science, high energy density physics, situational awareness, laser 3D imaging and other military and civilian fields. Time resolution is the core indicator for measuring the time test accuracy of gated image intensifiers, mainly referring to the shortest exposure time of gated image intensifiers. Since the gated electric pulse is between the loaded cathode and the input surface of the MCP (microchannel plate), its response speed is mainly determined by the RC constant in this equivalent circuit. Since the photocathode material of the image intensifier is mainly a semiconductor with poor conductivity, its RC time constant is large, and it is difficult to achieve fast opening and closing of the gate under the gate voltage. Therefore, it is necessary to make a conductive substrate layer with a certain transmittance and good conductivity between the cathode window and the photocathode material, so that it and the photocathode material can serve as a path for transmitting the gated electric pulse, reduce its effective resistivity, thereby reducing the RC time constant and shortening the opening time of the gated image intensifier.

[0003] The traditional solution is to evaporate a metal film layer (Al, Ni, Cr, Au, etc.) as a conductive substrate on the window substrate inside the cathode manufacturing chamber before making the image intensifier cathode, and then make the photocathode on the metal conductive substrate. However, this method cannot accurately control the film thickness of the conductive substrate, resulting in uneven gating performance of the image intensifier. At the same time, the entire surface coating on the cathode surface will reduce the transmittance of the cathode window, thereby reducing the cathode response sensitivity of the entire tube. In theory, the cathode conductive substrate can be made into a metal microstructure with a nano-grid and similar topological structure by photolithography, which can improve the cathode conductivity while ensuring the transmittance. However, since the image intensifier is an electric vacuum device, the thickness of its cathode window is relatively thick (>5.4mm) to withstand the impact of one atmosphere, and the traditional photolithography machine can only process thin substrates with a thickness of <2~3mm, so it is impossible to use mature semiconductor photolithography technology to complete the production of nano-microstructure conductive substrates. Therefore, it is necessary to propose a new technical method that can produce a metal microstructure with a nanogrid (or a similar periodic structure) on a thicker cathode window substrate as the cathode conductive substrate of the image intensifier. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above-mentioned problems existing in the prior art manufacturing of image intensifiers, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to provide a method for manufacturing a gated image intensifier cathode conductive substrate based on nanoimprint technology, which aims to solve the problem of how to manufacture a layer of metal conductive substrate with a nano-microstructure between the image intensifier photocathode and the input light window, thereby effectively shortening the exposure time of the gated image intensifier.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology, the manufacturing method comprising the following process steps:

[0008] S1: Plating a metal conductive base film layer on the substrate surface of the cathode window;

[0009] S2: Then, a nanoimprint UV curing adhesive is dripped onto the surface of the metal conductive base film layer and evenly coated to form a UV curing adhesive layer;

[0010] S3: closely attaching the imprinting mold to the surface of the UV-curing adhesive layer and slowly pressing it into the UV-curing adhesive layer to form a combination;

[0011] S4: The combined body is evenly irradiated with ultraviolet light, and after the ultraviolet curing adhesive is cured, the imprinting mold is removed to form an imprinting curing adhesive layer on the surface of the metal conductive base film layer.

[0012] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, the substrate is selected from AVG optical glass, fused quartz, magnesium fluoride, calcium fluoride or an optical fiber panel.

[0013] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, before plating a metal conductive substrate film layer on the substrate surface, the substrate surface needs to be polished and flattened to the nanometer level.

[0014] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, the polished substrate is ultrasonically cleaned alternately with anhydrous ethanol and deionized water to remove impurities on the substrate surface, and then dried.

[0015] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, wherein: the metal conductive substrate film layer includes Ni / Au layer, Cr / Au layer, Cr layer and Ni layer materials from bottom to top; and the thickness of Ni in the Ni / Au layer is greater than 10nm, and the thickness of Au is greater than 200nm; the thickness of Cr in the Cr / Au layer is greater than 10nm, the thickness of Au is greater than 200nm, the thickness of the Cr layer is greater than 300nm, and the thickness of the Ni layer is greater than 300nm.

[0016] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, the nanoimprint UV curing glue is coated by high-speed rotation, and the rotation speed ranges from 3000 to 4000 revolutions per minute, and the thickness of the coating layer is less than 50 nm.

[0017] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, the imprint mold is manufactured on a fused quartz base that is transparent or translucent to ultraviolet light by using a photolithography process or electron beam direct writing.

[0018] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, wherein: the nano-microstructure pattern forms protrusions and recesses on the imprinting mold, and the depth of the protrusions or recesses is greater than 100nm; the nano-microstructure pattern includes a periodic grid shape or a honeycomb shape.

[0019] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology of the present invention, the formed imprinted cured adhesive layer is processed, and the following process steps are also included:

[0020] S5: using a reactive ion etching method to remove the residual colloid in the imprinted cured glue layer corresponding to the metal area to be etched, so as to expose the surface of the metal conductive base film layer to be etched;

[0021] S6: etching the metal conductive base film layer corresponding to the recessed portion of the nano-microstructure pattern region by wet etching until the substrate material of the cathode window is exposed;

[0022] S7: removing the imprinted cured adhesive layer to obtain a substrate with a nano-microstructure.

[0023] As a preferred solution of the method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology described in the present invention, the imprinted cured adhesive layer is removed by immersing the substrate that has completed the nanoimprint process in an acetone solution for ultrasonic cleaning, and then repeatedly rinsing it with anhydrous ethanol and deionized water.

[0024] Beneficial effects of the present invention:

[0025] Compared with the film layer of metal vapor-deposited on the cathode window by traditional process, the metal conductive substrate with nano-microstructure produced by the present invention has higher effective transmittance and lower resistivity, and the thickness and structure are controllable, which is convenient for large-scale industrial production. Compared with the method of producing a metal conductive substrate with nano-microstructure by photolithography process, this method has no restriction on the thickness of the cathode window and can be implemented on the existing cathode window greater than 5.5mm, which has higher feasibility. The cathode conductive substrate produced by the method proposed by the present invention can effectively reduce the effective resistance of the cathode, reduce the RC time constant between the cathode and the MCP input surface, and reduce the exposure time of the gated image intensifier to less than 3 nanoseconds or even below sub-nanoseconds. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0027] Figure 1 It is a schematic diagram of the longitudinal cross-sectional structure of the cathode window substrate of the method for manufacturing the cathode conductive substrate of a gated image intensifier based on the nanoimprint technology of the present invention.

[0028] Figure 2 It is a schematic diagram of the cross-sectional structure of an imprinting mold of a method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology of the present invention.

[0029] Figure 3 The present invention is a schematic diagram of the graphic structure in the imprinting mold of the method for manufacturing the cathode conductive substrate of the gated image intensifier based on the nanoimprint technology.

[0030] Figure 4~Figure 11 The present invention is a schematic diagram of the process of manufacturing a cathode conductive substrate for a gated image intensifier based on nanoimprint technology.

[0031] Fig.12 It is a schematic diagram of the top plan structure of a metal conductive substrate with a nano-microstructure in the method for manufacturing a cathode conductive substrate of a gated image intensifier based on the nanoimprint technology of the present invention.

[0032] Fig.13 Image intensifier door opening time test data using conductive substrates made using existing technology;

[0033] Fig.14 The test data of the opening time of the image intensifier with a conductive substrate produced by the method of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0037] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0038] Reference Figures 1 to 12 , as one embodiment of the present invention, provides a method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology, and the manufacturing method includes the following process steps:

[0039] S1: Substrate coating: coating a metal conductive base film layer on the substrate surface of the cathode window;

[0040] The selected cathode window substrate (referred to as "substrate" in the process implementation process) has a "convex" step glass cross section and is a cylindrical shape formed by rotating stacking as a whole, as shown in the attached figure. Figure 1 Its materials include but are not limited to AVG optical glass, fused quartz, magnesium fluoride, calcium fluoride, optical fiber panel, etc. The circular surface on the top is the surface that needs to be processed by nanoimprinting process to produce microstructure metal conductive substrate pattern.

[0041] It should be noted that before the metal conductive base film layer is plated on the substrate surface, the substrate surface needs to be thoroughly optically mirror polished and flattened to the nanometer level (substrate polishing).

[0042] The polished substrate is then ultrasonically cleaned alternately with anhydrous ethanol and deionized water to remove impurities on the substrate surface, and then dried for later use (substrate cleaning).

[0043] Furthermore, the plated metal conductive base film layer includes Ni / Au layer, Cr / Au layer, Cr layer and Ni layer materials from bottom to top; and the thickness of Ni in the Ni / Au layer is greater than 10nm, and the thickness of Au is greater than 200nm; the thickness of Cr in the Cr / Au layer is greater than 10nm, the thickness of Au is greater than 200nm, the thickness of the Cr layer is greater than 300nm, and the thickness of the Ni layer is greater than 300nm.

[0044] S2: Film coating: Then, the nano-imprint UV curing glue is dripped onto the surface of the metal conductive base film layer and evenly coated to form a UV curing glue layer;

[0045] The nanoimprint UV curing adhesive is coated by high-speed rotation at a speed ranging from 3000 to 4000 rpm, so that the nanoimprint UV curing adhesive is evenly coated on the substrate surface and the thickness of the coating layer is less than 50 nm.

[0046] S3: Mold imprinting: The imprinting mold is tightly attached to the surface of the UV-curing adhesive layer and slowly pressed into the UV-curing adhesive layer to form a combination;

[0047] Specifically, the imprint mold needs to be made in advance, which is the core component in the nanoimprint process. It can be made of materials that are transparent or semi-transparent to ultraviolet light, such as fused quartz; the imprint mold as a whole has a certain thickness and structural strength to meet the structural requirements of pressing nano patterns on the substrate surface during the process. On the contact surface between the imprint mold and the substrate, the nano-microstructure pattern to be imprinted can be made using traditional photolithography or electron beam direct writing exposure.

[0048] In this embodiment, the nano-microstructure pattern includes but is not limited to a periodic grid or honeycomb shape, and its pattern structure is as follows: Figure 2 As shown in . One feasible size is a grid line width of 500nm and a grid period of 5μm. The black strips are depressions on the contact surface of the imprint mold, and the blank areas are protrusions on the contact surface of the imprint mold. The cross section of the graphic structure on the contact surface of the imprint mold is shown in Figure 3 The depth of the protrusions or depressions is greater than 100 nm.

[0049] The imprinting mold is pressed into the UV-curing adhesive layer by a nano-imprinting machine, so that the mold and the adhesive layer fit tightly. During this process, the flowable nano-imprinting UV-curing adhesive will be squeezed out of the protruding part of the mold and fill the concave part through the capillary effect.

[0050] S4: UV curing: The combination is evenly irradiated with UV light, and after the UV curing adhesive is cured, the imprinting mold is immediately removed to form an imprinting curing adhesive layer on the surface of the metal conductive base film layer.

[0051] S5: etching residual glue: using reactive ion etching to remove the residual glue in the imprinted cured glue layer corresponding to the metal area to be etched, so as to expose the surface of the metal conductive base film layer to be etched;

[0052] S6: Pattern etching: Wet etching is used to etch the metal conductive base film layer corresponding to the concave portion below the nano-microstructure pattern area until the substrate material of the cathode window is exposed;

[0053] S7: Removing residual adhesive: removing the imprinted cured adhesive layer to obtain a substrate with a nano-microstructure.

[0054] Specifically, the imprinted cured adhesive layer is removed by immersing the substrate (cathode window substrate) that has completed the nanoimprint process in an acetone solution for ultrasonic cleaning, and then repeatedly rinsed with anhydrous ethanol and deionized water to remove the remaining residual adhesive.

[0055] After the above process is completed, the nano-microstructured metal conductive substrate on the cathode window can be inspected under a microscope to confirm the success rate and yield rate of the process.

[0056] Implementation Examples

[0057] S1: Substrate coating: coating a metal conductive base film layer on the substrate surface of the cathode window;

[0058] The selected cathode window base (called "substrate") has a cylindrical cross-section of a "convex" stepped glass, and the process surface of the microstructure to be fabricated is a perfect circular surface with a diameter of 18 mm.

[0059] The substrate surface is thoroughly optically mirror polished to achieve a flatness of ≤50nm.

[0060] The polished substrate was ultrasonically cleaned with anhydrous ethanol and deionized water with a purity of more than 99%, alternating for 6 times, each time for ≥ 10 minutes, to remove impurities on the surface of the substrate, and then dried for standby use.

[0061] The metal conductive substrate is plated by magnetron sputtering, and the metal film layers are Cr (100nm) / Au (100nm) from bottom to top.

[0062] S2: Film coating: Then, the nano-imprint UV curing glue is dripped onto the surface of the metal conductive base film layer and evenly coated to form a UV curing glue layer;

[0063] Among them, the nanoimprint UV curing adhesive (IPNR-PC1000) is coated by high-speed rotation, and the rotation speed range is 3000~4000 rpm, so that the nanoimprint UV curing adhesive is evenly coated on the substrate surface, and the thickness of the coating layer is about 40nm.

[0064] S3: Mold imprinting: The imprinting mold is tightly attached to the surface of the UV-curing adhesive layer and slowly pressed into the UV-curing adhesive layer to form a combination;

[0065] The imprinting mold is pressed into the UV-curing adhesive layer by a nanoimprint machine so that the mold and the adhesive layer fit tightly. During this process, the flowable nanoimprint UV-curing adhesive will be squeezed out of the protruding parts of the mold and fill the recessed parts through the capillary effect. The pressing time between the mold and the cathode window process surface is >5 minutes per time.

[0066] S4: UV curing: The combination is evenly irradiated with ultraviolet light of a wavelength of 266 nm, and the irradiation time is >5 minutes per time. After the UV curing adhesive is cured, the imprinting mold is immediately removed to form an imprinting curing adhesive layer on the surface of the metal conductive base film layer.

[0067] The adhesive layer produced by this process is in a grid shape, with a grid stripe line width of 500nm and a grid period of 5μm.

[0068] S5: etching residual glue: using reactive ion etching to remove the residual glue in the imprinted cured glue layer corresponding to the metal area to be etched, so as to expose the surface of the metal conductive base film layer to be etched;

[0069] The reactive ion etching process parameters are as follows: O2 flow rate 30 sccm; gas pressure 170 mTorr; RF (radio frequency) power 85 W; time 30 s.

[0070] S6: Pattern etching: Wet etching is used to etch the metal conductive base film layer corresponding to the concave portion below the nano-microstructure pattern area until the substrate material of the cathode window is exposed;

[0071] The Au metal layer can be corroded by using Au corrosive solution; the Cr metal layer can be corroded by using saturated ammonium cerium nitrate solution.

[0072] S7: Removing residual adhesive: removing the imprinted cured adhesive layer to obtain a substrate with a nano-microstructure.

[0073] Specifically, the imprinted cured adhesive layer is removed by immersing the substrate (cathode window substrate) that has completed the nanoimprint process in an acetone solution for ultrasonic cleaning (power 100%, time > 10 minutes), and then repeatedly rinsed with anhydrous ethanol and deionized water to remove the remaining residual adhesive (single rinse time is greater than 5 minutes, and the number of repetitions is > 6 times).

[0074] In summary, the nano-conductive substrate made based on the present invention can effectively shorten the exposure time of the gated image intensifier. According to experimental tests, the image intensifier made by the conventional method of making the conductive substrate has a gate opening time of 98ns (e.g. Fig.13 The method provided by the present invention is used to manufacture an image intensifier with a conductive substrate, and its gate opening time is 1.1ns (as shown in FIG. Fig.14 As shown). It can be seen that the conductive substrate prepared by this experimental method can significantly shorten the exposure time of the gated image intensifier.

[0075] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology, characterized in that: The process steps include: Plating a metal conductive base film layer on the substrate surface of the cathode window; Then, a nano-imprint UV curing adhesive is dripped onto the surface of the metal conductive base film layer and evenly coated to form a UV curing adhesive layer; The imprinting mold is tightly attached to the surface of the UV-curing adhesive layer and slowly pressed into the UV-curing adhesive layer to form a combined body; The combined body is evenly irradiated with ultraviolet light, and after the ultraviolet curing adhesive is cured, the imprinting mold is removed to form an imprinting curing adhesive layer on the surface of the metal conductive base film layer; The substrate is selected from AVG optical glass, fused quartz, magnesium fluoride, calcium fluoride or optical fiber panel; Before plating the metal conductive base film layer on the substrate surface, the substrate surface needs to be polished and flattened to the nanometer level; The polished substrate is ultrasonically cleaned alternately with anhydrous ethanol and deionized water to remove impurities on the surface of the substrate, and then dried; The formed embossed cured adhesive layer is processed, and the steps include: Reactive ion etching is used to remove the residual colloid in the imprinted cured glue layer corresponding to the metal area to be etched, so that the surface of the metal conductive base film layer to be etched is exposed; Then, the metal conductive base film layer corresponding to the recessed portion below the nano-microstructure pattern area is etched by wet etching until the substrate material of the cathode window is exposed; Removing the imprinted cured adhesive layer to obtain a substrate with a nano-microstructure; The method for removing the imprint cured adhesive layer is to immerse the substrate after the nanoimprint process in an acetone solution for ultrasonic cleaning, and then rinse it repeatedly with anhydrous ethanol and deionized water.

2. The method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology according to claim 1, characterized in that: The metal conductive base film layer includes Ni / Au layer, Cr / Au layer, Cr layer and Ni layer materials from bottom to top; The thickness of Ni in the Ni / Au layer is greater than 10 nm, and the thickness of Au is greater than 200 nm; the thickness of Cr in the Cr / Au layer is greater than 10 nm, and the thickness of Au is greater than 200 nm, the thickness of the Cr layer is greater than 300 nm, and the thickness of the Ni layer is greater than 300 nm.

3. The method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology according to claim 2, characterized in that: The nanoimprint UV curing adhesive is coated by high-speed rotation, and the rotation speed ranges from 3000 to 4000 revolutions per minute, and the thickness of the coating layer is less than 50 nm.

4. The method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology according to claim 3, characterized in that: The imprinting mold adopts a photolithography process or an electron beam direct writing method to produce a nanometer microstructure pattern on a fused quartz base that is transparent or semi-transparent to ultraviolet light.

5. The method for manufacturing a cathode conductive substrate of a gated image intensifier based on nanoimprint technology according to claim 4, characterized in that: The nano-microstructure pattern forms protrusions and depressions on the imprinting mold, and the depth of the protrusions or depressions is greater than 100 nm; The nano-microstructure pattern includes a periodic grid shape or a honeycomb shape.

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