A method for preparing a conductive grid window glass substrate based on nanoimprint technology

Abstract

The application discloses a method for preparing a conductive grid window glass substrate based on a nano-imprinting technology, and solves the problem that the surface of the conductive grid window glass substrate prepared by the prior art method has a similar cosine wave fluctuation, the surface is uneven, and a transverse stray current is generated when the conductive grid window glass substrate works in an accelerated electric field. The method comprises the following steps: etching a target pattern on the surface of a glass wafer by using a nano-imprinting process to form a grid groove; depositing a conductive layer on the surface of the glass wafer by a coating process to fill the grid groove; polishing the surface by a chemical mechanical polishing (CMP) process; and finally preparing the conductive grid window glass substrate with a smooth surface by a glass thermal bonding process. When the substrate is used in a fast-response and ultrafast-response photoelectric detection device, the response time can be effectively reduced, and electrons can be quickly supplemented to a photosensitive medium material, so that high-speed time resolution and transient capture of the photoelectric device can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of conductive grid window glass substrate, and in particular to a method for preparing a conductive grid window glass substrate based on nanoimprint technology. BACKGROUND

[0002] Photoelectric devices respond to external electromagnetic radiation based on photoelectric effect and output photoelectric current or voltage signal to external circuit, such as thin film photovoltaic cell, vacuum electron source, vacuum image intensifier tube and other photoelectric detection devices. The indicators for evaluating the performance of the device in the quality factor of the device are photosensitive waveband, quantum efficiency (QE) and response time (RT). The photosensitive waveband is the photosensitive range of the photosensitive medium material in the photoelectric device. The quantum efficiency is the ratio of the number of photons incident on the photosensitive medium material (numerator) to the actual number of photoelectrons produced (denominator). The quantum efficiency spectrum curve can be obtained together with the photosensitive waveband. The response time is the time interval for the photosensitive medium material in the photoelectric device to output a photoelectron after being photosensitive; the smaller the value, the faster the photoelectric device can record the physical phenomenon of the transient state, and the higher the time resolution.

[0003] The light absorption process of the photosensitive medium is in the order of attoseconds, the photoelectron diffusion and emission process is in the order of femtoseconds and picoseconds, and the existing electron gating replenishment time of the vacuum image tube is in the order of nanoseconds. The larger the diameter of the imaging surface of the vacuum image tube, the more serious the iris effect, that is, the longer the time for the gating waveform to spread on the photocathode surface, and the slower the electron replenishment speed. After the photocathode material absorbs light radiation and emits photoelectrons, the photocathode itself is in a state of electron deficiency and needs to be replenished with electrons in time. In order to balance the light transmission of the transmission type photoelectric device and the need for rapid electron replenishment of the photocathode, a conductive grid is used as a base electrode for the photocathode to replenish electrons and transmit light.

[0004] There are many electrode materials that can be matched with the photocathode material, such as metal film, silver nanowire, graphene, etc.; considering the compatibility of the photocathode preparation and the vacuum image tube sealing process in the back-end of the photoelectric device, metal Ni is generally preferred. The process of patterning the conductive layer includes photolithography process and diamond drawing, etc., but directly etching the conductive layer on the surface of the window glass substrate results in a conductive grid with a convex surface, which causes the surface of the photocathode material prepared thereon to have a similar sinusoidal fluctuation, and the transverse stray current is generated when it works in the acceleration electric field. SUMMARY

[0005] The present application aims to provide a method for preparing a conductive grid window glass substrate based on nanoimprint technology, to solve the technical problem that the surface of the conductive grid window glass substrate prepared by the existing method has a similar sinusoidal fluctuation, making the surface uneven, and the transverse stray current is generated when it works in the acceleration electric field.

[0006] The inventive concept of the present application is as follows:

[0007] The present application etches a target pattern on the surface of a glass wafer by a nano-imprinting process to form a grid groove; then deposits a conductive layer on the surface by a coating process to fill the grid groove, and then polishes the surface by a chemical mechanical polishing (CMP) process, and finally prepares a surface flat conductive grid window glass substrate by a glass thermal bonding process. The substrate can be used in fast response and ultrafast response photoelectric detection devices to effectively reduce the response time and quickly replenish electrons to the photosensitive medium material, and can achieve high-speed time resolution and transient capture of photoelectric devices.

[0008] In order to achieve the above-mentioned purpose, complete the above-mentioned inventive concept, the present application adopts the following technical scheme:

[0009] A method for preparing a conductive grid window glass substrate based on a nano-imprinting technology, which is used in a micro-light night vision image tube ultrafast imaging transmission device, and has the following steps:

[0010] Step 1, etching a glass wafer;

[0011] A glass wafer of the same material as the window glass substrate to be prepared is selected, a target pattern is etched on the inner surface of the glass wafer by a nano-imprinting process to obtain a grid groove; the size of the area occupied by the grid groove matches the size of the small circular surface of the window glass substrate to be prepared;

[0012] Step 2, coating a conductive layer;

[0013] A conductive layer with a predetermined thickness is coated in the grid groove;

[0014] Step 3, chemical mechanical polishing and laser cutting;

[0015] The part of the conductive layer that exceeds the inner surface of the glass wafer is removed and the inner surface of the glass wafer is polished flat, and the glass wafer is cut into a wafer with the grid groove; the diameter of the wafer is greater than the diameter of the small circular surface on the vacuum side of the window glass substrate to be prepared for growing a photoelectric cathode material;

[0016] Step 4, bonding with a substrate glass;

[0017] The outer surface of the cut wafer is attached to the small circular surface of the window glass substrate to be prepared, and a homogenous glass bonding process is used to thermally bond the two, so that they become one, and the edge reversal process is used to make the slope of the side of the wafer consistent with that of the window glass substrate to be prepared, thereby completing the preparation of the conductive grid window glass substrate.

[0018] Further, step 1 specifically includes:

[0019] 1.1, draw a GDS layout of a target pattern, the size of the area occupied by the target pattern matches the size of the small circular surface of the window glass substrate to be prepared;

[0020] 1.2, prepare an imprint mold based on the GDS layout, and select a glass wafer made of the same material as the window glass substrate to be prepared;

[0021] 1.3, evenly apply an imprint glue or photoresist on the inner surface of the glass wafer;

[0022] 1.4, contact the imprint mold with the applied imprint glue or photoresist, so that the target pattern on the imprint mold is transferred to the imprint glue;

[0023] 1.5, etch the target pattern on the glass wafer using a dry etching plasma etching process to obtain a grid etching groove, and the size of the area occupied by the grid etching groove matches the size of the small circular surface of the window glass substrate to be prepared;

[0024] 1.6, remove the imprint glue or photoresist, and clean the surface of the glass wafer.

[0025] Further, step 2 is specifically:

[0026] A magnetic sputtering coating process or an evaporation coating process is used to coat a conductive layer of a predetermined thickness in the grid etching groove.

[0027] Further, in step 2:

[0028] The predetermined thickness is 2 times the groove depth of the grid etching groove.

[0029] Further, in step 2, the conductive layer uses Au, Ag, Cu, Cr or Ni.

[0030] Further, step 3 is specifically:

[0031] A chemical mechanical polishing method is used to remove the part of the conductive layer that exceeds the inner surface of the glass wafer and polish it flat, and a laser cutting process is used to cut the glass wafer into a circular piece with the grid etching groove.

[0032] Further, step 4 is specifically:

[0033] The outer surface of the cut-out circular piece and the small circular surface of the window glass substrate to be prepared are respectively cleaned, then the two are correspondingly attached, and a homogenous glass bonding process is used for thermal bonding, so that the two become one whole, and through the edge turning process, the side slope of the circular piece and the window glass substrate to be prepared is consistent, completing the preparation of the conductive grid window glass substrate.

[0034] Further, in step 1:

[0035] The period of the grating groove is 1-500 microns, the line width is 50-2000 nm, and the groove depth is 200-1000 nm.

[0036] Further, in step 1,

[0037] The period of the grating groove is 20 microns, the line width is 1 micron, and the groove depth is 350 nm.

[0038] Further, in step 2, the conductive layer is made of transparent conductive material.

[0039] The transparent conductive material is ITO, IZO, AZO or FTO.

[0040] The beneficial effects of the present application are:

[0041] 1. The present application uses nanoimprint process to etch the surface of the glass wafer, the target pattern has high fidelity, the etching depth is controllable, the groove side and bottom are neat, and the process is stable. In the window glass substrate processing of the micro-light night vision image tube super-fast imaging transmission device, the process not only has better preparation conditions but also can meet the demand of large-scale production.

[0042] 2. The present application uses chemical mechanical polishing (CMP) process to polish and grind the etched surface of the glass wafer coated with the conductive layer, so as to remove the excess conductive layer material in the inner surface of the glass wafer, and only leave the conductive layer in the grating groove of the glass wafer, realizing a non-photolithography process patterning process. While removing the excess conductive layer material on the surface of the glass wafer, the CMP process also realizes the planarization process of the surface of the glass wafer, laying a foundation for the subsequent preparation of high-quality semiconductor photocathode film layer on its surface.

[0043] 3. The conductive grating window glass substrate prepared by the method provided by the present application can be used as the conductive window glass substrate of other transmission type photoelectric devices. By growing single crystal, polycrystalline or amorphous semiconductor film layer, such as photovoltaic semiconductor material to prepare photovoltaic device, X-ray, ultraviolet or infrared sensitive semiconductor material to prepare detection device, or depositing ultra-thin metal layer to prepare X-ray image converter, etc., the application range is wider and the practicality is stronger.

[0044] 4. The method provided by the present application can also use transparent conductive material (such as ITO, IZO, AZO, FTO, etc.) to coat the conductive layer, so as to improve the photoelectric response performance of the corresponding photoelectric device. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 It is a method flow chart for preparing a conductive grating window glass substrate based on nanoimprint technology;

[0046] Figure 2is a scanning electron microscope image after the nanoimprint process in the embodiment of the present application, Fig. a is a front view, and Fig. b is a side view;

[0047] Figure 3 is a confocal microscope image after plating a metal Ni film layer and chemical mechanical polishing in the embodiment of the present application, Fig. a is a center area graph of the conductive grid, and Fig. b is an edge area graph of the conductive grid;

[0048] Figure 4 is a transmittance curve graph of the conductive grid window substrate after bonding in the embodiment of the present application. DETAILED DESCRIPTION

[0049] The technical solutions of the present application will be described clearly and completely in combination with the drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0050] The embodiment of the present application provides a method for preparing a conductive grid window glass substrate based on a nanoimprint technology, which is used for manufacturing a conductive grid window glass substrate, as shown in the figure. Figure 1 The manufacturing process flow includes the following steps:

[0051] Step 1, etching a glass wafer;

[0052] A glass wafer with the same material as the window glass substrate to be prepared is selected, and a nanoimprint process is used to etch a target pattern on the inner surface of the glass wafer to obtain a grid etching groove. The size of the area occupied by the grid etching groove matches the size of the small circular surface of the window glass substrate to be prepared.

[0053] In this embodiment, since a homogeneous bonding process is required subsequently, the glass wafer selected is made of the same material as the window glass substrate to be prepared.

[0054] In this embodiment, borosilicate glass, i.e. Corning 7056 glass, is selected. Other optional glasses include fused quartz glass, domestic brand JGS1, or domestic borosilicate glass.

[0055] A nanoimprint process is used to etch a target pattern on the inner surface of the glass wafer, and a grid etching groove, i.e. a grid-shaped groove, is obtained after etching. A conductive layer is plated in the grid etching groove by sputtering plating, and the inner surface of the glass wafer is polished by a chemical mechanical polishing (CMP) process.

[0056] The method for etching by using a nanoimprint process is as follows:

[0057] Design the high-precision target pattern to be processed: the period is about 20 μm, the line width is about 1 μm, and the groove depth is about 350 nm, which are used as the center conditions of the nanoimprint process. Draw the GDS layout of the target pattern based on the GDS layout, manufacture the corresponding mask, and then prepare the imprint mold. Uniformly coat the imprint glue or photoresist on the inner surface of the selected glass wafer, and contact the imprint mold with the imprint glue. The target pattern on the imprint mold is transferred to the imprint glue or photoresist. Finally, the target pattern is etched on the glass wafer by using the dry etching plasma etching process. Finally, the imprint glue is removed and cleaned. The grid etched groove obtained after processing is shown in the scanning electron microscope image of Figure 2 , Figure 2 In a, the positive view angle is photographed, the actual measured value of the line width is 1.13 μm, and the actual measured value of the grid period is 1.13 μm. Figure 2 In b, the side view angle section is photographed, and the actual measured value of the etched groove depth is 355 nm. Figure 2 In b of the grid pattern structure surface, the imprint glue has not been removed, and the contrast is low and can be distinguished and seen clearly. In actual processing, the pattern structure deviates due to the fluctuations of the nanoimprint process and the plasma etching process, and the structural deviation is acceptable within the range of ≤±5%. The target pattern structure in the present example is only a preferred structure, and other optional sparse target pattern structure parameter ranges are: the period is 5 μm to 500 μm, the line width is 1 μm to 2 μm, the groove depth is 200 nm to 400 nm, or other grid pattern structures.

[0058] The nanoimprint process combined with the plasma etching process is very effective for etching glass materials. The etched pattern has high fidelity, controllable etching depth, and neat etched groove sides and bottom edges. The obtained negative grid surface lays a foundation for the subsequent preparation of the whole conductive grid.

[0059] Step 2, plating a conductive layer;

[0060] A conductive layer with a preset thickness is plated in the grid etched groove etched in step 1.

[0061] On the basis of the target pattern grid grooves made on the inner surface of the glass wafer, an evaporation process is used to plate a conductive layer to fill the grid grooves. Because the Ni conductive grid window has excellent adaptability with the photosensitive medium material photoelectric cathode material (such as alkali antimony photoelectric cathode), and is compatible with the later process. Therefore, the Ni film is preferred to be plated, and other Au, Ag, Cu, Cr and other metals can be selected, in addition, transparent conductive materials such as ITO, IZO, AZO, FTO, etc. can also be used. The conductive layer can be plated by a magnetron sputtering plating process or an evaporation plating process; the evaporation process is preferred in this embodiment, the plating film temperature is about 200°C and the film thickness is preset, and the thickness of the finally plated Ni conductive layer is about 2 times the groove depth of the grid groove, that is, 600-700 nm; to ensure that the grid groove is completely filled with Ni metal. The glass wafer cannot transmit light at this stage, and the visual metal film layer is covered with a metal film.

[0062] Step 3, chemical mechanical polishing and laser cutting;

[0063] The part of the conductive layer beyond the inner surface of the glass wafer is removed and the inner surface of the glass wafer is polished flat, and the glass wafer is cut into a wafer with grid grooves; the diameter of the wafer is greater than the diameter of the small circular surface on the vacuum side of the window glass substrate to be prepared for growing the photoelectric cathode material;

[0064] The excess Ni metal on the grid groove surface of the glass wafer is removed by chemical mechanical polishing (CMP) machine grinding and polishing, and the amount of Ni metal film is adjusted by adjusting the type and amount of polishing liquid and the polishing table pressure, and finally only the metal Ni filled in the grid groove is left as a conductive mesh line. Figure 3 Confocal microscope image after plating metal Ni film layer and chemical mechanical polishing; Figure 3 The a in the figure is the center area image of the conductive grid, from which it can be seen that the conductive metal line grid is clear and has no broken line, and the imaging focus surface is flat. Figure 3 The b in the figure is the edge area image of the conductive grid, in which the conductive metal line grid area and the non-conductive metal line grid area can be clearly distinguished. Figure 3 In the b of the figure, the metal line appears as a bright line due to reflective imaging, and the non-metal area only has the grid groove as a contrast darker line; the imaging difference between the metal line grid area and the non-metal line grid area is distinct, which exactly proves the apparent difference before and after filling the metal material in the grid groove. The surface resistance of the conductive grid area is about 3Ω / □ measured by a four-point probe electrical measurement platform; if the line width remains unchanged and the grid period value decreases, a conductive grid with smaller surface resistance can be obtained, and if the line width remains unchanged and the grid period value increases, a conductive grid with larger surface resistance can be obtained.

[0065] The conductive glass wafer obtained by completing the above process on the glass wafer needs to be further cut by using a laser cutting technology. The 2-inch or 4-inch conductive glass wafer is placed on a cutting machine to be cracked, and then cut into a disc with a diameter of about 20 mm. The diameter of the disc is greater than the diameter of a small circular surface on the window glass substrate to be prepared for growing a photoelectric cathode material in the vacuum side (a standard piece with a diameter of 18 mm in the night vision field), so that subsequent remediation can be performed when there is deviation, and the etched grid groove is also avoided.

[0066] Step 4, bonding with the substrate glass;

[0067] The outer surface (non-structure side) of the cut disc is matched with the small circular surface of the window glass substrate to be prepared, and the two are thermally bonded by using a homogeneous glass bonding process, so that they become one whole, and the disc and the side slope of the window glass substrate to be prepared are consistent through the chamfering process, and the preparation of the conductive grid window glass substrate is completed.

[0068] Specifically, the obtained disc with a conductive grid structure is thermally bonded with the window glass substrate of the vacuum image tube. Homogeneous glass bonding is a complex and lengthy process. The bonding temperature of the borosilicate glass selected in the embodiment is about 600°C. Before bonding, the bonding surface is cleaned and treated with ammonia and other chemicals, so that the bonding interface is transparent and has no turbidity, and the bonding strength is firm. Figure 4 For the transmittance curve of the conductive grid window substrate after bonding, it can be directly observed that the transmittance of the photograph window glass substrate before bonding is > 90%, and the transmittance of the conductive grid window substrate after the conductive grid structure is bonded is reduced to about 73% due to the thickening of the substrate and the light blocking of the metal wire. The sparse grid structure can increase the transmittance of the conductive glass substrate, but the surface resistance will increase; selecting other grid pattern structures can adjust the transmittance value. By carefully observing Figure 4 the cut-off wavelength of the transmittance curve, it can be observed that the cut-off wavelength of the photograph is about 280 nm, and the cut-off wavelength of the conductive grid window glass substrate is blue-shifted to about 260 nm; the blue shift is due to the modulation effect of the grid structure on the incident light field.

[0069] The prepared conductive grid window glass substrate has high ultraviolet-visible-near infrared transmittance, low surface resistance, and smooth inner surface of the conductive substrate, and high-quality semiconductor photosensitive material can be further grown on the surface thereof.

[0070] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any change or replacement within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for fabricating conductive grid window glass substrates based on nanoimprint technology, used in ultrafast imaging transmissive devices for low-light night vision tubes, characterized in that, Includes the following steps: Step 1: Etching the glass wafer; A glass wafer of the same material as the glass substrate to be prepared is selected, and the target pattern is etched on the inner surface of the glass wafer using nanoimprint lithography to obtain a grid groove; the size of the area occupied by the grid groove matches the size of the small circular surface of the glass substrate to be prepared. Step 2: Deposit a conductive layer; A conductive layer of a predetermined thickness is plated inside the groove of the grid. Step 3: Chemical mechanical polishing and laser cutting; Remove the portion of the conductive layer that extends beyond the inner surface of the glass wafer and polish the inner surface of the glass wafer flat. Cut the glass wafer into circular pieces with the grid grooves. The diameter of the circular pieces is larger than the diameter of the small circular surface on the vacuum side of the window glass substrate to be prepared for growing photocathode materials. Step 4: Bonding with the substrate glass; The outer surface of the cut circular piece is attached to the small circular surface of the window glass substrate to be prepared, and the two are thermally bonded using a homogeneous glass bonding process to make them a whole. The side slope of the circular piece and the window glass substrate to be prepared are made consistent by a beveling process, thus completing the preparation of the conductive grid window glass substrate.

2. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 1, characterized in that, Step 1 specifically includes: 1.1 Draw the GDS layout of the target pattern, wherein the size of the area occupied by the target pattern matches the size of the small circular surface of the glass substrate to be prepared; 1.

2. Based on the GDS layout, prepare an imprinting mold, and select a glass wafer of the same material as the glass substrate of the window to be prepared; 1.

3. Apply imprinting adhesive or photoresist evenly to the inner surface of the glass wafer; 1.

4. Bring the embossing mold into contact with the applied embossing adhesive or photoresist, so that the target pattern on the embossing mold is transferred to the embossing adhesive; 1.

5. The target pattern is etched on the glass wafer using a dry etching plasma etching process to obtain a grid groove. The size of the area occupied by the grid groove matches the size of the small circular surface of the glass substrate to be prepared. 1.6 Remove the imprinting adhesive or photoresist and clean the surface of the glass wafer.

3. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 1 or 2, characterized in that, Step 2 is as follows: A conductive layer of a predetermined thickness is deposited in the grid groove using magnetron sputtering or vapor deposition processes.

4. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 3, characterized in that, In step 2: The preset thickness is twice the depth of the grid groove.

5. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 4, characterized in that: In step 2, the conductive layer is made of Au, Ag, Cu, Cr or Ni.

6. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 5, characterized in that, Step 3 specifically involves: The portion of the conductive layer extending beyond the inner surface of the glass wafer is removed by chemical mechanical polishing and then flattened. The glass wafer is then cut into circular pieces with the aforementioned grid grooves using laser cutting technology.

7. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 6, characterized in that, Step 4 is as follows: The outer surface of the cut circular wafer and the small circular surface of the window glass substrate to be prepared are cleaned respectively. Then, the two are bonded together and thermally bonded using a homogeneous glass bonding process to make them a whole. Finally, the side slope of the circular wafer and the window glass substrate to be prepared are made consistent through a beveling process to complete the preparation of the conductive grid window glass substrate.

8. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 7, characterized in that, In step 1: The period range of the grid groove is 1μm to 500μm, the line width is 50nm to 2μm, and the groove depth is 200nm to 1000nm.

9. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 8, characterized in that, In step 1: The grid groove has a period range of 20μm, a line width of 1μm, and a groove depth of 350nm.

10. The method for preparing a conductive grid window glass substrate based on nanoimprint technology according to claim 4, characterized in that: In step 2, the conductive layer is made of a transparent conductive material; The transparent conductive material is ITO, IZO, AZO, or FTO.

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