A terahertz vacuum electronic device cold cathode grid and preparation method thereof

Abstract

The present invention discloses a cold cathode grid of a terahertz vacuum electronic device, comprising: a grid substrate, which includes a grid through-hole array in the central area of ​​the grid substrate; and a grid support ring, which is located on the grid substrate, and the two are welded together. The grid can be applied to the cold cathode of a terahertz vacuum electronic device, and can achieve good comprehensive performance of the device. The present invention also discloses a method for preparing the cold cathode grid of a terahertz vacuum electronic device.

Description

Technical Field

[0001] The present invention relates to the field of vacuum microelectronics, and more specifically, to a cold cathode grid of a terahertz vacuum electronic device and a preparation method thereof. Background Art

[0002] The traditional definition of terahertz electromagnetic wave radiation frequency range is 0.1-10THz. Terahertz waves themselves have the characteristics of high radiation frequency, small divergence angle, and high signal-to-noise ratio. Therefore, terahertz technology has irreplaceable application value and development prospects in various basic research fields and applied research fields.

[0003] Compared with solid-state and optical terahertz devices, the obvious advantage of terahertz vacuum electronic devices is that they have very large power capacity. They have clear application needs in the country's economic construction, security work, scientific and technological innovation, as well as in national defense fields such as terahertz radar, intersatellite high-speed communication systems, high-resolution imaging of space targets, guidance and electronic countermeasures.

[0004] Since vacuum electronic devices in the terahertz band are very small, this requires not only very high processing precision of tiny parts, but also a well-focused and very fine electron beam, which means that a cathode with a small emission surface and high current density is desired. Traditional hot cathodes used in vacuum electronic devices are difficult to miniaturize and adapt to the needs of terahertz vacuum electronic devices due to their mechanical processing methods and the need for high-temperature heating systems.

[0005] Field emission cathodes do not require additional energy. By simply applying a strong electric field externally to suppress the cathode surface barrier, the barrier height and width can be reduced, allowing the electrons in the emitter to escape through the tunnel effect. Compared with traditional thermal emission cathodes, field emission cold cathodes compatible with micromachining technology have the characteristics of low power consumption, small size, fast response speed, room temperature operation, and high current density, which can meet the needs of terahertz vacuum electronic devices.

[0006] Early field emission cold cathodes were Spindt cathodes, such as Figure 1 As shown, or other similar structure cathodes are representative, such as the cathode described in the US invention patent with publication number US 6369496 B1, which are characterized by having micro-machined integrated gates with a spacing of microns or sub-microns, and the cathode emission array units and micro-gates correspond one to one. However, due to industrial reasons, these structures are difficult to achieve large-area uniformity. The emission non-uniformity of the micro-units in the array limits the improvement of the cathode emission capacity; and because the cathode-gate spacing is very close, it is easy to produce inter-electrode sparking, resulting in a short circuit between the emitter and the gate, and the overall reliability is not high.

[0007] Invention patents with publication numbers CN105428185A and CN105551911A describe non-integrated gate-controlled cathode structures, such as Figure 2 As shown in the figure, the lead-out grid is a metal sheet with a thickness of tens to hundreds of microns, less than 1 mm away from the cathode, and there is a mesh array formed by photolithography or laser processing on the sheet, the aperture is generally tens to hundreds of microns, and the grid wire diameter is tens of microns. Through a specific process flow, the grid and the cathode array are precisely matched, which minimizes the interception of electrons by the gate, improves the efficiency of electron utilization, and reduces the pressure of gate heat dissipation. At the same time, the distance between the cathode substrate and the gate is relatively far, which greatly reduces the short circuit between the cathode and the gate caused by the evaporation of the emission material, and has excellent comprehensive characteristics.

[0008] Non-integrated metal grids are suitable for field emission cold cathodes of terahertz vacuum electronic devices, but the grids required by terahertz vacuum electronic devices are not exactly the same as those described in the above patents. Due to the reduction of the critical dimensions of the device itself, the device requires that the grid aperture, grid wire diameter and grid thickness should be greatly reduced. For example, for a 220GHz device, the typical design value of the grid is a grid aperture of 80-120 microns, and the grid wire diameter and thickness are both 20 microns. As the device frequency increases, the grid thickness will be further reduced from tens of microns to a few microns.

[0009] In the invention patents with publication numbers CN105428185A and CN105551911A, the thickness of the metal grid is tens to hundreds of microns, and its strength and structure are sufficient to support the process of laser processing or photolithography and etching to prepare hole arrays. However, this process is not applicable to cold cathode grids of small-sized terahertz vacuum electronic devices. Metal sheets with a thickness of tens to several microns have poor strength and are difficult to operate during processing or subsequent assembly. In addition, it is difficult for thin metal sheets to resist thermal deformation caused by laser processing, and the burrs on the edges of laser processing that are difficult to completely remove cannot be ignored relative to the size structure; similarly, the flatness deformation caused by insufficient strength makes it difficult to ensure high-quality planar photolithography and etching processes. Therefore, the thickness of the maturely prepared grids currently is basically not less than 50 microns.

[0010] In view of this, it is indeed necessary to provide a stable structure for realizing an ultra-thin metal grid and a method for preparing such an ultra-thin metal grid, which can be applied to the cold cathode of a terahertz vacuum electronic device to achieve good comprehensive performance of the device. Summary of the invention

[0011] Based on the above facts, the first object of the present invention is to provide a terahertz vacuum electronic device cold cathode grid, which can be applied to the terahertz vacuum electronic device cold cathode and can achieve good comprehensive performance of the device.

[0012] The second object of the present invention is to provide a method for preparing a cold cathode grid for a terahertz vacuum electronic device. The method is particularly suitable for preparing a small-sized and high-precision cold cathode grid for a terahertz vacuum electronic device.

[0013] In order to achieve the above first object, the present invention adopts the following technical scheme:

[0014] A terahertz vacuum electronic device cold cathode grid, comprising:

[0015] A grid substrate comprising a grid through-hole array in a central region of the grid substrate;

[0016] A grid support ring is located on the grid substrate, and the two are welded together;

[0017] Wherein, the grid substrate is selected from one of copper, nickel, chromium and gold.

[0018] Furthermore, the grid support ring is located at the edge of the grid substrate, avoiding the grid through-hole array.

[0019] Furthermore, the inner ring of the grid support ring has an inclination angle of 30-70 degrees.

[0020] Furthermore, the grid support ring is selected from one of copper, stainless steel and molybdenum.

[0021] Furthermore, the grid substrate has a thickness of 40 microns to 5 microns.

[0022] Furthermore, the light transmittance of the gate through-hole array is 70%-90%.

[0023] Furthermore, in the gate through hole array, the shapes of the gate through holes are closely packed square, circular, triangular, regular hexagonal or spoke grid.

[0024] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0025] providing a substrate;

[0026] forming an adherent layer of electroplating material on the substrate;

[0027] applying a photoresist on the electroplating material adhesion layer;

[0028] Exposing and developing the photoresist to form a photoresist mold located in the center area of ​​the electroplating material adhesion layer, the pattern of which corresponds to the gate through-hole array pattern one by one;

[0029] forming a gate electroplating layer that completely covers the photoresist mold and the electroplating material adhesion layer;

[0030] Thinning the mixed layer formed by the photoresist mold and the gate electroplating layer until the thickness of the gate electroplating layer reaches the required thickness of the grid substrate;

[0031] Removing the photoresist mold to obtain a grid substrate consisting of a grid electroplating layer;

[0032] Welding the grid support ring to the grid substrate;

[0033] The substrate and the adhesion layer of the electroplating material are removed to obtain the grid.

[0034] Furthermore, the material of the electroplating material adhesion layer is chromium or titanium, and the thickness of the electroplating material adhesion layer is 30 nanometers to 100 nanometers.

[0035] Furthermore, the method of forming the electroplating material adhesion layer is vacuum evaporation coating or magnetron sputtering coating.

[0036] Furthermore, the substrate is a silicon wafer, a silicon oxide wafer, a glass wafer or a metal substrate whose surface parallelism and flatness meet the requirements of photolithography.

[0037] Furthermore, the photoresist is a thick photoresist used in MEMS technology, preferably KMPR photoresist or SU8 photoresist.

[0038] Furthermore, the thinning method is grinding and polishing.

[0039] Furthermore, the thickness of the photoresist mold is greater than the depth of the required gate through-hole array.

[0040] Furthermore, the method of removing the photoresist mold is wet chemical etching, oxygen plasma etching, high temperature ashing or molten salt method.

[0041] Furthermore, the welding method is brazing, laser welding or diffusion welding.

[0042] Furthermore, the material of the gate electroplating layer is selected from copper, nickel, chromium and gold.

[0043] Furthermore, the flattening and polishing are performed by chemical mechanical grinding and polishing methods.

[0044] Furthermore, the method for removing the substrate and the adhesion layer of the electroplating material by etching is a wet chemical etching method, and the etching solution does not damage the grid support ring and the grid substrate.

[0045] The beneficial effects of the present invention are as follows:

[0046] The cold cathode grid of the terahertz vacuum electronic device provided by the present invention realizes an ultra-thin grid substrate structure with a thickness of tens of microns to several microns. The grid support ring effectively keeps the ultra-thin grid substrate from being easily deformed, and can focus the extracted electron beam by relying on the inner ring inclination angle. The ultra-thin grid is combined with the grid hole aperture and grid wire diameter with correspondingly reduced size, which can meet the needs of devices with increasing frequencies.

[0047] The method for preparing a cold cathode grid of a terahertz vacuum electronic device provided by the present invention enables an ultra-thin grid substrate to be completed by electroplating on a nearly ideal flat substrate. The substrate is always firmly attached to the substrate during the entire process, and the high flatness ensures the high quality of the micro-machined graphics. The grid substrate is separated from the substrate only after being firmly welded to the grid support ring, and its flatness is highly retained during the transfer process and the subsequent assembly process.

[0048] In the preparation method, the through-hole array of the grid is directly electroplated through the photoresist model, which can form high-quality gate through-holes with steep characteristic dimensions accurately controlled, and will not produce edge burrs caused by laser processing technology and isotropic side corrosion inclination angles caused by photolithography and etching processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0050] Figure 1 A schematic diagram of an integrated self-aligned gate Spindt cathode structure is shown.

[0051] Figure 2 A schematic diagram of a non-integrated metal grid field emission cold cathode structure is shown.

[0052] Figure 3 A schematic diagram of the cold cathode grid structure of the terahertz vacuum electronic device of the present invention is shown.

[0053] Figures 3A-3I A schematic diagram of the preparation process of the cold cathode grid of the terahertz vacuum electronic device of the present invention is shown: 3A-providing a substrate, 3B-preparing an adhesion layer, 3C-coating a photoresist, 3D-exposure and development to make a photoresist mold, 3E-electroplating the grid material, 3F-grinding and polishing the electroplating layer / photoresist, 3G-removing the photoresist, 3H-welding the grid support ring, and 3I-etching to remove the substrate and the adhesion layer.

[0054] Figure 1 In the figure, the component numbers are respectively represented as: 101 - cathode base, 102 - cathode tip cone, 103 - insulating layer, 104 - gate substrate, 105 - gate through hole.

[0055] Figure 2 In the figure, the component numbers are respectively represented as: 201 - cathode substrate, 202 - cathode array, 203 - insulating layer, 204 - gate substrate, 205 - gate through hole.

[0056] Figure 3 as well as Figures 3A-3IIn the figure, the component numbers are respectively represented as follows: 300 - cold cathode grid of terahertz vacuum electronic device, 301 - substrate, 302 - electroplating material adhesion layer, 303 - photoresist, 304 - photoresist mold, 305 - grid electroplating layer, 306 - grid substrate, 307 - grid through hole, 308 - grid support ring.

[0057] Figure 4 A physical picture of a grid prepared by the present invention is shown. DETAILED DESCRIPTION

[0058] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0059] Example 1

[0060] like Figure 3 As shown, this embodiment provides a terahertz vacuum electronic device cold cathode grid 300, which includes: a grid substrate 306, including a grid through hole array 307 in the central area of ​​the grid substrate 306; a grid support ring 308 is located on the grid substrate 306, and the two are welded together; the material of the grid substrate 306 is selected from one of copper, nickel, chromium, and gold.

[0061] The thickness of the grid substrate 306 ranges from 40 microns to 5 microns according to the frequency band of the terahertz device. In this embodiment, the exemplary thickness is 30 microns to 5 microns, 30 microns to 15 microns, 30 microns to 20 microns, 20 microns to 5 microns, 18 microns to 5 microns, 15 microns to 5 microns, etc., preferably 20 microns. The material of the grid substrate 306 is selected from copper, nickel, chromium, gold, etc. suitable for electroplating. In this embodiment, copper is preferred.

[0062] The grid through hole array 307, in order to achieve the best electron extraction effect, has a through hole shape selected from close-packed square, circular, triangular, regular hexagonal or spoke grid shape, with a light transmittance of 70%-90%. Its thickness is the same as that of the grid substrate 306. The preferred thickness is 20 microns. In this embodiment, the regular hexagonal through hole is preferred, the hexagonal side length is preferably 60 microns, the grid wire diameter is preferably 20 microns, and the corresponding light transmittance is 70%. The area occupied by the grid through hole array 307 is determined according to the actual cold cathode area. In this embodiment, the preferred area is a circular area with a radius of 2 mm.

[0063] The grid support ring 308 is located at the edge of the grid substrate 306, avoiding the grid through-hole array 307. The grid support ring 308 and the grid substrate 306 are welded together, and its main function is to firmly support the grid substrate 306 to keep it flat and not deformed, to help dissipate heat and focus the extracted electron beam. Typically, the size of the grid support ring 308 is in the order of millimeters. In this embodiment, the inner diameter of the bottom of the support ring is preferably 5 mm, the outer diameter of the bottom is 9 mm, and the height of the support ring is 2 mm.

[0064] The grid support ring 308 is selected from materials suitable for vacuum devices such as copper, stainless steel, and molybdenum. In this embodiment, copper is preferred.

[0065] The inner ring tilt angle of the grid support ring 308 can affect the electric field distribution, thereby converging and extracting the electron beam. Typically, the inner ring tilt angle of the grid support ring 308 is in the range of 30-70 degrees. In this embodiment, the inner ring tilt angle is preferably 60 degrees.

[0066] like Figures 3A-3I The embodiment of the technical solution also provides a method for preparing a cold cathode grid 300 of a terahertz vacuum electronic device, which specifically includes the following steps:

[0067] Step 1) providing a substrate 301.

[0068] The substrate 301 is used as the basic support of the entire process flow, and is required to have high flatness, high parallelism and high finish. The materials that meet the requirements include silicon wafers, silicon oxide wafers, glass wafers or metal substrates that have been partially precision polished. In this embodiment, silicon wafers are preferred.

[0069] Step 2) preparing an electroplating material adhesion layer 302 on the substrate 301 .

[0070] In this embodiment, since the material of the grid substrate 306 is selected from copper, nickel, chromium, gold, etc. suitable for electroplating, electroplated copper is preferred. Since copper and the like have poor adhesion to most substrate 301 materials, a layer of electroplated material adhesion layer 302 is first prepared on the substrate 301. The material of the electroplated material adhesion layer 302 is typically selected from metal titanium or chromium. In this embodiment, metal chromium is preferred. The preparation method of the electroplated material adhesion layer 302 is typically selected from vacuum evaporation coating or magnetron sputtering coating. The vacuum evaporation method is simple in equipment and implementation but has poor bonding strength. In this embodiment, magnetron sputtering coating is preferably used for the preparation of the electroplated material adhesion layer 302. The electroplated material adhesion layer 302 is also used as an electrode layer in the electroplating process. The film thickness is typically in the range of 30 nanometers to 100 nanometers. In this embodiment, the electroplated material adhesion layer 302 preferably has a thickness of 100 nanometers.

[0071] Step 3) coating photoresist 303 on the electroplating material adhesion layer 302.

[0072] The photoresist 303 is used to form a mold for the subsequent electroplating process. Typically, the photoresist used in the electroplating process mold is a thick photoresist used in MEMS technology, including KMPR photoresist or SU8 photoresist, both of which are commercially available from MicroChem. There is a certain degree of difficulty in removing the thick film of SU8 photoresist, but it can form excellent graphics; the use process of KMPR photoresist is simple, but the molding performance, especially the steepness of the sidewalls, is slightly poor. In this embodiment, the photoresist 303 is preferably SU8. The electroplating mold formed by the photoresist 303 is used to form a grid substrate 306, and the overall thickness of the electroplating mold should be greater than the thickness of the grid substrate 306, that is, the thickness of the coated photoresist 303 is greater than the thickness of the grid substrate 306 required in the end. In this embodiment, the thickness of the photoresist 303 is preferably 22 microns. In this embodiment, the photoresist 303 is coated using a typical spin coating technique, and the SU8 2015 photoresist is spun once to form a thickness of 22 microns.

[0073] Step 4) The photoresist 303 is exposed and developed to form a photoresist mold 304 located in the central area of ​​the electroplating material adhesion layer 302, the pattern of which corresponds to the gate through hole array pattern one by one.

[0074] The exposure process can be realized by using typical ultraviolet exposure technology, and a specific part of the photoresist 303 is exposed by masking, and the exposed part is retained by a subsequent development process, and the unexposed part is removed to form a photoresist mold 304. The pattern of the photoresist mold 304 corresponds to the required pattern of the gate through hole array 307. In this embodiment, the pattern of the photoresist mold 304 is a regular hexagonal column with a side length of 60 microns and a column height of 22 microns. The spacing between each column is 20 microns, which is equivalent to the wire diameter width of the gate through hole array 307.

[0075] Step 5) Electroplating is performed through the photoresist mold 304 to form a gate electroplating layer 305 .

[0076] The electroplating material adhesion layer 302 is used as the electroplating cathode, and the photoresist mold 304 is used as a mask for electroplating, and a gate electroplating layer 305 is formed in the gap and surface of the photoresist mold 304. It can be understood that the thickness of the gate electroplating layer 305 is greater than the height of the photoresist mold 304, and the gate electroplating layer 305 completely covers the photoresist mold 304.

[0077] In this embodiment, the gate electroplating layer 305 is preferably copper. In order to ensure that the gate substrate 306 preferably has an overall thickness of 20 microns, in this embodiment, electroplating is preferably performed to ensure that the gate electroplating layer 305 completely covers the photoresist mold 304 and the electroplating material adhesion layer 302 exposed in the gaps between the photoresist molds 304, and the plating thickness is about 23 microns.

[0078] Step 6) Thinning the gate electroplating layer 305 / photoresist mold 304 mixed layer to form a grid substrate 306.

[0079] The thinning method is preferably grinding and polishing. The grinding process is to quickly reduce the thickness of the thin film layer to obtain a parallel and flat substrate surface, and the polishing process is to obtain a high-finish substrate surface by slightly removing the material. The high-finish surface without micro-convex burrs is necessary for the application of field emission cold cathode. In this embodiment, the grinding and polishing process is preferably a typical chemical mechanical polishing method in MEMS technology, which relies on large abrasive particles and high grinding disc speed to implement grinding, and small abrasive particles and low grinding disc speed to implement polishing. In this embodiment, chemical mechanical grinding is first performed to reduce the thickness of the gate electroplating layer 305 / photoresist mold 304 mixed layer to a thickness slightly higher than the thickness of the grid substrate 306 (it can be understood that by grinding, the surface of the photoresist mold 304 is at least exposed), preferably 21 microns, and then chemical mechanical polishing is performed to obtain a smooth gate electroplating layer 305 / photoresist mold 304 mixed layer surface, and the thickness is controlled to the desired thickness of the grid substrate 306, preferably 20 microns, that is, a grid substrate 306 with gaps and remnants of the photoresist mold 304 is obtained (it can be seen that it is formed by the remaining electroplating material layer 305).

[0080] This step is to grind and polish the photoresist mold 304 until it is thinned to a desired thickness, where the desired thickness is the desired thickness of the grid substrate 306 .

[0081] Step 7) removing the photoresist mold 304 residues mixed in the grid substrate 306.

[0082] To remove the SU8 photoresist, wet chemical etching, oxygen plasma etching, high temperature ashing or molten salt removal methods can be typically selected. In this embodiment, wet chemical etching is preferred, and the etching liquid is preferably Remover PG, a SU8 photoresist matching remover from MicroChem. After removing the photoresist mold 304 residues mixed with the grid substrate 306, the grid substrate 306 supported on the substrate 301 and the electroplating material adhesion layer 302 is obtained.

[0083] Step 8) Weld the grid support ring 308 and the grid substrate 306 together.

[0084] The purpose of welding the grid support ring 308 and the grid substrate 306 together is to stabilize the grid substrate 306 with the grid support ring 308 to ensure that it remains unchanged during subsequent processes and packaging applications. The grid support ring 308 is prepared by traditional mechanical processing in this embodiment. The welding method can typically use brazing, laser welding and diffusion welding with mature vacuum device processes. In this embodiment, considering that the grid support ring 308 and the grid substrate 306 are made of the same material copper, vacuum diffusion welding is preferably used as the welding process. Align the grid support ring 308 with the center of the grid through-hole array 307, place the grid support ring 308 on the grid substrate 306, place it in a vacuum, apply pressure and high temperature, and weld the grid support ring 308 and the grid substrate 306 together.

[0085] Step 9) removing the substrate 301 and the electroplating material layer 302 to obtain Fig. 3I Grid 300 is shown.

[0086] The removal of the substrate 301 and the electroplating material adhesion layer 302 is to separate the prepared grid 300 from the substrate. The removal method is preferably a corrosion method, preferably, the substrate 301 and the electroplating material adhesion layer 302 are dissolved by wet corrosion, or only the electroplating material adhesion layer 302 is dissolved, and the grid 300 is peeled off from the substrate 301. The selection of the etching solution should take into account the ability to react quickly with the substrate 301 / electroplating material adhesion layer 302 and not damage the grid 300. In this embodiment, a potassium hydroxide solution with a concentration of 30% is preferably used to corrode the substrate 301 and the electroplating material adhesion layer 302 to complete the preparation of the grid 300.

[0087] In a specific example, a terahertz vacuum electronic device cold cathode grid 300 formed by a grid support ring 308 and a grid substrate 306 is obtained from this embodiment. The grid support ring 308 ensures that the ultra-thin grid substrate 306 does not deform, and at the same time assists the grid in heat dissipation, and relies on a preferably 30-70 degree inclination angle, more preferably a 60 degree inclination angle, to influence the electric field to converge the extracted electron beam. The grid substrate 306 is 20 microns thick, and the central area of ​​the substrate with a diameter of 4 mm is densely covered with a through hole array. The through hole shape is a regular hexagon with a side length of 60 microns, the grid wire diameter is 20 microns, and the corresponding light transmittance is 70%. The grid can be used for field emission cold cathodes with a cathode area diameter of 4 mm or less.

[0088] Example 2

[0089] Example 1 is repeated, except that in step 4), the photoresist mold 304 formed by photolithography is in the shape of a square column with a side length of 80 microns and a spacing of 10 microns between each column. Other conditions remain unchanged. The result of the grid 300 obtained in this example is similar to that of Example 1, except that the grid array holes 307 are square hole arrays with a transmittance of 80%.

[0090] Example 3

[0091] Example 1 is repeated, except that in step 3), the coating thickness of the photoresist 303 is changed to 12 microns; in step 5), the thickness of the gate electroplating layer 305 is changed to 13 microns; in step 6), the grinding thickness of the gate electroplating layer 305 / photoresist mold 304 mixed layer is changed to 11 microns, and the polishing thickness is changed to 10 microns. Other conditions remain unchanged. The result of the grid 300 obtained in this example is similar to that of Example 1, except that the thickness of the grid substrate 301 is 10 microns.

[0092] The method of the present invention breaks through the limitation that conventional laser processing or photolithography etching methods can only achieve a grid with a thickness of more than 50 microns, and can achieve an ultra-thin grid with any thickness in the range of 5-50 microns (for example, 5-20 microns), and the grid plane is not easy to deform, the surface finish is better than 100nm, and the edge of the through hole array is smooth and burr-free, which can meet the requirements of the cold cathode of terahertz vacuum electronic devices.

[0093] The grid made by this method, carbon nanotube cold cathode and metal anode form a triode for electron emission test. The results show that for a structure configuration with a cathode diameter of 1 mm, a grid thickness of 20 microns and a transmittance of 80%, when the peak electric field strength is 12V / μm in the pulse state of 1% duty cycle, the anode collects a peak current of 5.8mA, the grid intercepts a peak current of 2.4mA, and the actual effective output current ratio is 70.7%. The grid draws out the current, which is compressed 5-10 times by focusing design to form a fine beam, which can be used in terahertz vacuum electronic devices. The grids obtained in other embodiments can also achieve similar effects and can be used in terahertz vacuum electronic devices.

[0094] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A cold cathode grid for a terahertz vacuum electronic device, characterized in that: It includes: A grid substrate comprising a grid through-hole array in a central region of the grid substrate; A grid support ring is located on the grid substrate, and the two are welded together; Wherein, the grid substrate is selected from one of copper, nickel, chromium and gold; The method for preparing the grid comprises the following steps: providing a substrate; forming an adherent layer of electroplating material on the substrate; applying a photoresist on the electroplating material adhesion layer; Exposing and developing the photoresist to form a photoresist mold located in the center area of ​​the electroplating material adhesion layer, the pattern of which corresponds to the gate through-hole array pattern one by one; forming a gate electroplating layer that completely covers the photoresist mold and the electroplating material adhesion layer; Thinning the mixed layer formed by the photoresist mold and the gate electroplating layer until the thickness of the gate electroplating layer reaches the required thickness of the grid substrate; Removing the photoresist mold to obtain a grid substrate consisting of a grid electroplating layer; Welding the grid support ring to the grid substrate; The substrate and the adhesion layer of the electroplating material are removed to obtain the grid.

2. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The grid support ring is located at the edge of the grid substrate, avoiding the grid through-hole array.

3. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The inner ring of the grid support ring has an inclination angle of 30-70 degrees.

4. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The grid support ring is selected from one of copper, stainless steel and molybdenum.

5. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The thickness of the grid substrate is 40 microns to 5 microns.

6. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The light transmittance of the gate through-hole array is 70%-90%.

7. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: In the gate through hole array, the shapes of the gate through holes are closely packed square, circular, triangular, regular hexagonal or spoke grid.

8. The cold cathode grid for terahertz vacuum electronic devices according to claim 1, characterized in that: The material of the electroplating material adhesion layer is chromium or titanium, and the thickness of the electroplating material adhesion layer is 30 nanometers to 100 nanometers.

9. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The method for forming the electroplating material adhesion layer is vacuum evaporation coating or magnetron sputtering coating.

10. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The photoresist is a thick photoresist used in MEMS technology.

11. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The photoresist is KMPR photoresist or SU8 photoresist.

12. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The thickness of the photoresist mold is greater than the depth of the required gate through hole array.

13. The cold cathode grid for terahertz vacuum electronic devices according to claim 1, characterized in that: The substrate is a silicon wafer, an oxidized silicon wafer, a glass wafer or a metal substrate whose surface parallelism and flatness meet the requirements of photolithography.

14. The cold cathode grid for terahertz vacuum electronic devices according to claim 1, characterized in that: The methods for removing the photoresist mold are wet chemical etching, oxygen plasma etching, high temperature ashing or molten salt method.

15. The cold cathode grid of a terahertz vacuum electronic device according to claim 1, characterized in that: The welding method is brazing, laser welding or diffusion welding.

16. A method for preparing a cold cathode grid for a terahertz vacuum electronic device according to any one of claims 1 to 15.

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