Silicon-based all-dielectric terahertz metamaterial device and preparation method thereof

Abstract

The application provides a preparation method of a silicon-based all-dielectric terahertz metamaterial device, which has a surface structure capable of supporting multiple resonances in a terahertz wave band, and the surface structure is formed by groove and via structure units periodically etched on a silicon wafer surface to form a multiple resonance structure in the terahertz wave band; the groove and via structure unit is composed of a groove, a protrusion and two vias located in the middle of the groove and the protrusion; when the surface structure performs electromagnetic induction on the terahertz wave, one end of the groove is processed to face the incident end of the terahertz wave, and the other end without the groove is processed to face the emission end of the terahertz wave; and the technical scheme can realize the preparation of silicon-based microstructures with two different groove depths on the same silicon wafer surface through multiple photoetching technologies and deep silicon etching.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of terahertz metamaterials, and particularly relates to a silicon-based all-dielectric terahertz metamaterial device and a preparation method thereof. BACKGROUND

[0002] The surface plasmon resonance effect generated by the terahertz metamaterial has the characteristics of efficiently regulating electromagnetic waves. Therefore, breakthrough progress has been made in the miniaturization application of resonant devices, such as modulators, polarizers, lasers and sensors. At present, the commonly used method is to use metal structures to excite plasmon resonance, and the metal is accompanied by fixed ohmic loss. The all-dielectric metamaterial is concerned due to its low loss characteristics. However, how to efficiently prepare the all-dielectric terahertz metamaterial with high quality and high precision to meet the use requirements is the key to the development of terahertz science and technology.

[0003] At present, the commonly used terahertz metamaterial micro-nano processing technology mainly includes traditional photolithography technology, electron beam exposure and femtosecond laser direct writing, and these processing technologies are mainly used to meet the processing requirements of metal microstructures. However, for the processing of all-dielectric metamaterials, for example, when multiple pattern processing is required on silicon, the processing precision and etching depth, perpendicularity and the like often cannot meet the expected requirements, and the device cannot achieve the expected performance effect. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a silicon-based all-dielectric terahertz metamaterial device and a preparation method thereof. Through multiple photolithography technology and deep silicon etching, two kinds of through-hole type silicon-based microstructures with different groove depths can be prepared on the surface of the same silicon wafer.

[0005] To achieve the above purpose, the present application adopts the following technical scheme: a silicon-based all-dielectric terahertz metamaterial device has a surface structure capable of supporting multiple resonances in the terahertz wave band. The surface structure is formed by periodically etching groove and through-hole structure units on the surface of a silicon wafer to form a multiple resonance structure in the terahertz wave band. The groove and through-hole structure unit is composed of a groove, a protrusion and two through-holes located in the middle of the groove. When the surface structure induces electromagnetic waves, one end of the groove is processed towards the incident end of the terahertz wave, and the other end without the groove is processed towards the emission end of the terahertz wave.

[0006] In a preferred embodiment: the silicon wafer is a silicon wafer with a thickness of 200 μm; the groove and through-hole structure units are uniformly etched in rows on the silicon surface, and the period is 260 and 130 μm; in the groove and through-hole structure unit, the groove width is 130 μm, the depth is 14 and 20 μm respectively, the protrusion width is 130 μm, and the size of the two through-holes is 80 μm.

[0007] This invention also provides a method for fabricating a silicon-based all-dielectric terahertz metamaterial device, which fabricates the aforementioned silicon-based all-dielectric terahertz metamaterial device: for forming a surface structure that can support multiple resonances in the terahertz band, and the surface can be further divided into through-hole silicon-based terahertz metamaterials with different groove depths, comprising the following steps:

[0008] Step S1: Photoresist is applied to the silicon wafer. The periodic groove pattern on the photomask is copied onto the photoresist using a photolithography process. Then, deep silicon etching is used to etch the exposed groove positions on the silicon wafer to form grooves with depths of 14 and 20 μm.

[0009] Step S2: Photoresist is applied to the silicon-based terahertz metamaterial with groove pattern processed in step S1. The through-hole structure is copied onto the photoresist through photolithography, and then the exposed through-hole structure area is further etched through deep silicon etching.

[0010] In a preferred embodiment: the specific method in step S1 is as follows:

[0011] Step S11: The silicon wafer is placed in acetone and isopropanol solutions in sequence for ultrasonic cleaning to remove surface contaminants, and then subjected to plasma treatment to improve surface activity.

[0012] Step S12: Place the processed silicon wafer on a spin coater, then drop an appropriate amount of photoresist onto it, and perform two spin coat processes at a uniform speed; then place the sample with photoresist spin-coated on a hot plate to bake to enhance the adhesion of the photoresist.

[0013] Step S13: Project the groove pattern on the photomask onto the photoresist film using an MA6 lithography machine.

[0014] Then perform exposure processing.

[0015] The photoresist in the light portion undergoes a degradation reaction and becomes soluble in the developing solution, followed by a developing process to remove the light.

[0016] Resin film forming groove diagram

[0017] It is coated onto a silicon wafer and then subjected to a hard coating process to enhance the adhesion of the photoresist film;

[0018] Step S14: Place the silicon wafer with the photoresist pattern on the surface into the ICP etching machine and perform deep silicon etching based on the Bosch etching process. Specifically, passivation gas C4F8 and etching gas SF6 are alternately circulated in the etching machine to perform a passivation-etching chemical reaction on the silicon wafer, thereby transferring the groove pattern on the photoresist onto the silicon wafer.

[0019] Step S15: Put the silicon wafer into acetone and isopropyl alcohol solution for ultrasonic cleaning, and then dry it with air gun and perform plasma cleaning to remove photoresist and impurities remaining in the groove.

[0020] In a preferred embodiment, in step S2, the specific method is as follows:

[0021] Step S21: Put the silicon wafer with groove pattern on the glue sprayer for twice glue spraying, and then place the silicon wafer sample sprayed with photoresist on the hot plate for baking to enhance the adhesion of the photoresist.

[0022] Step S22: Project the via pattern on the mask onto the photoresist film by MA6 photoetching machine, and then perform exposure treatment to make the exposed part of the photoresist undergo degradation reaction and be soluble in the developing solution, and then perform developing treatment to form the via pattern on the silicon wafer, and then perform film hardening treatment to enhance the adhesion of the photoresist film.

[0023] Step S23: Put the silicon wafer with photoresist pattern on the ICP etching machine to perform deep silicon etching based on Bosch etching process, specifically: alternately input passivation gas C4F8 and etching gas SF6 in the etching machine to perform passivation-etching chemical reaction on the silicon wafer, thereby transferring the via pattern on the photoresist to the silicon wafer to form a silicon surface with preset via.

[0024] Step S24: Put the silicon wafer with preset groove and via into acetone and isopropyl alcohol solution for ultrasonic cleaning, and then dry it with air gun and perform plasma cleaning to remove excess photoresist and residual silicon impurities in the via.

[0025] In a preferred embodiment, the silicon wafer processed in step S2 is cut by a cutting machine to divide it into four 15mm×15mm silicon-based full-dielectric terahertz metamaterial array structures with groove depth of 14μm and four 15mm×15mm silicon-based full-dielectric terahertz metamaterial array structures with groove depth of 20μm.

[0026] In a preferred embodiment: in the ultrasonic cleaning, ultrasonic cleaning in acetone for 10 minutes, ultrasonic cleaning in isopropyl alcohol for 5 minutes; in the plasma cleaning, the time is 5 minutes; the photoresist is AZ6130; when the spin coater is used for spin coating, the first rotation speed is 500 rpm, the spin coating time is 5 seconds, the second rotation speed is 2000 rpm, the spin coating time is 30 seconds, the baking temperature of the baking machine is 100 DEG C, and the baking time is 3 minutes; in the exposure process, the exposure time of the groove pattern is 3.2 seconds; the developing solution is TMAH developing solution with a concentration of 2.38%, and the developing time is 50 seconds; the baking hardening process adopts a temperature of 100 DEG C, and the baking time is 3 minutes; in the Bosch etching process, the groove etching depth is 14 and 20 mu m, and the through-hole etching depth is 200 mu m, in the process, the flow rate of the passivation gas C4F8 gas is 190 sccm, the flow rate of the etching gas SF6 gas is 450 sccm, and the etching rate is 5.04 mu m / min.

[0027] In a preferred embodiment: the photoresist is RS220; in the spray coating process, the spray coating temperature is 100 DEG C, the spray coating air pressure is 0.5 mbar, and the spray coating distance is 50 mm.

[0028] In the exposure process, the exposure time of the through-hole pattern is 15 seconds; the developing solution is TMAH developing solution with a concentration of 2.38%, and the developing time is 90 seconds; the baking hardening process adopts a temperature of 100 DEG C, and the baking time is 10 minutes.

[0029] In a preferred embodiment: the laser wavelength of the cutting machine is 1342 nm, and the cutting speed is 300 mm / s.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] (1) By combining multiple photoetching and deep silicon etching micro-machining processes, the characteristics of precise geometric pattern replication and high-precision and high-aspect-ratio geometric structure etching of each process can be fully utilized, and a more complex geometric pattern can be machined on a silicon wafer, thereby solving the problem of low machining precision of other methods on a full dielectric metamaterial.

[0032] (2) The present application uses double-sided polished silicon wafers as a substrate material, and the prepared silicon-based full dielectric terahertz metamaterial has stable structure, high quality factor of resonance frequency, and can support terahertz surface multiple resonance modes, and is very suitable for application in various high-performance terahertz functional devices. BRIEF DESCRIPTION OF DRAWINGS

[0033] ATTACHMENT Fig. 1 It is an electron microscope top view of the silicon-based full dielectric terahertz metamaterial of the preferred embodiment of the present application.

[0034] Appendix Fig. 2 A schematic diagram showing the comparative transmission spectra of silicon-based all-dielectric terahertz metamaterials with etched groove depths of 14 and 20 μm, according to a preferred embodiment of the present invention;

[0035] Appendix Fig. 3 This is a schematic diagram of the system experiment of a preferred embodiment of the present invention;

[0036] In the diagram: 1-Terahertz wave transmitter; 2-Emitted terahertz wave; 3-Silicon wafer; 4-Groove; 5-Through hole; 6-Emitted terahertz wave; 7-Terahertz wave receiver; 8-Analysis device. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0039] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] like Figs. 1-3 As shown, a silicon-based all-dielectric terahertz metamaterial device has a surface structure that can support multiple resonances in the terahertz band. The surface structure forms a multiple resonance structure in the terahertz band by periodically etched grooves 4 and through holes 5 on the silicon wafer surface. The groove and through hole structural unit is composed of grooves, protrusions and two through holes located in the middle of them. When the surface structure electromagnetically induces terahertz waves, the end with the groove faces the incident end of the terahertz wave, and the end without the groove faces the emitting end of the terahertz wave.

[0041] The silicon wafer 3 has a silicon wafer surface with a thickness of 200 μm; the structural units of the grooves and vias are uniformly etched in rows and columns on the silicon surface with a period of 260 and 130 μm; in the structural units of the grooves and vias, the groove width is 130 μm, the depth is 14 and 20 μm respectively, the groove width is 130 μm, and the two vias are 80 μm in size.

[0042] The application discloses a preparation method of a silicon-based full-dielectric terahertz metamaterial device, and relates to the technical field of terahertz metamaterials.

[0043] Step S1: coating photoresist on a silicon wafer, copying a periodic groove pattern on a mask onto the photoresist through a photoetching process, and etching exposed groove positions of the silicon wafer through deep silicon etching to form grooves with a depth of 14 and 20 micrometers;

[0044] Step S2: coating photoresist on the silicon wafer with the groove pattern processed in step S1, copying a through-hole structure onto the photoresist through a photoetching process, and further etching the exposed through-hole structure area through deep silicon etching.

[0045] In the step S1, the specific method is as follows:

[0046] Step S11: sequentially placing the silicon wafer into acetone and isopropyl alcohol solutions for ultrasonic cleaning to remove surface contaminants, and then performing plasma treatment to improve surface activity;

[0047] Step S12: placing the treated silicon wafer on a photoresist coating machine, then dropping appropriate photoresist, and performing twice photoresist coating treatment at a constant speed; then placing the sample with the photoresist spin-coated on a hot plate for baking to enhance the adhesion of the photoresist;

[0048] Step S13: projecting the groove pattern on the mask onto the photoresist film through an MA6 photoetching machine, then performing exposure treatment, so that the photoresist in the exposed part is degraded and soluble in a developing solution, then performing developing treatment to form the groove pattern on the photoresist film on the silicon wafer, and then performing film hardening treatment to enhance the adhesion of the photoresist film;

[0049] Step S14: placing the silicon wafer with the photoresist pattern on the surface in an ICP etching machine, and performing deep silicon etching based on a Bosch etching process, specifically, alternately circulating and inputting a passivation gas C4F8 and an etching gas SF6 in the etching machine to perform a passivation-etching chemical reaction on the silicon wafer, so that the groove pattern on the photoresist is transferred to the silicon wafer;

[0050] Step S15: sequentially placing the silicon wafer into acetone and isopropyl alcohol solutions for ultrasonic cleaning, then blowing dry with an air gun, and then performing plasma cleaning to remove the photoresist and impurities remaining in the grooves.

[0051] In the step S2, the specific method is as follows:

[0052] Step S21: placing the silicon wafer with the groove pattern on the photoresprit coating machine, then performing twice photoresist coating treatment; then placing the silicon wafer sample with the photoresist sprayed on the hot plate for baking to enhance the adhesion of the photoresist;

[0053] Step S22: The via pattern on the mask is projected onto the photoresist film by the MA6 photoetching machine, and then the photoresist in the exposed part is subjected to a degradation reaction and is soluble in the developing solution, and then the photoresist film is subjected to a developing treatment to form a via pattern on the silicon wafer, and then a hardening treatment is performed to enhance the adhesion of the photoresist film;

[0054] Step S23: The silicon wafer with the photoresist pattern on the surface is placed in the ICP etching machine to perform deep silicon etching based on the Bosch etching process, specifically: the passivation gas C4F8 and the etching gas SF6 are alternately and cyclically introduced into the etching machine to perform the chemical reaction of passivation-etching on the silicon wafer, thereby transferring the via pattern on the photoresist to the silicon wafer to form a silicon surface with a preset via;

[0055] Step S24: The silicon wafer with the preset groove and via is sequentially placed in the acetone and isopropyl alcohol solution for ultrasonic cleaning, and then is blown dry by an air gun and then is subjected to a plasma cleaning to remove the excess photoresist and residual silicon impurities in the via.

[0056] The silicon wafer processed in step S2 is cut by a cutting machine to divide it into four 15mm×15mm silicon-based full-dielectric terahertz metamaterial array structures with a groove depth of 14μm and four 15mm×15mm silicon-based full-dielectric terahertz metamaterial array structures with a groove depth of 20μm.

[0057] In the ultrasonic cleaning, ultrasonic cleaning is performed in acetone for 10 minutes and in isopropyl alcohol for 5 minutes; in the plasma cleaning, the time is 5 minutes;

[0058] The photoresist is AZ6130; when the spin coater performs the spin coating treatment, the first rotation speed is 500rpm, the spin coating time is 5 seconds, the second rotation speed is 2000rpm, the spin coating time is 30 seconds, the baking temperature of the baking machine is 100℃, and the baking time is 3 minutes;

[0059] In the exposure treatment, the exposure time of the groove pattern is 3.2 seconds; the developing solution is a TMAH developing solution with a concentration of 2.38%, and the developing time is 50 seconds; the baking temperature for the hardening treatment is 100℃, and the baking time is 3 minutes;

[0060] The groove etching depth of the Bosch etching process is 14 and 20μm, and the via etching depth is 200μm; in this process, the flow rate of the passivation gas C4F8 is 190sccm, the flow rate of the etching gas SF6 is 450sccm, and the etching rate is 5.04μm / min.

[0061] The photoresist is RS220; in the photoresist spraying process, the spraying temperature is 100 DEG C, the spraying air pressure is 0.5 mbar, and the spraying distance is 50 mm;

[0062] In the exposure process, the exposure time of the through-hole pattern is 15 seconds; the developing solution is TMAH developing solution with a concentration of 2.38%, and the developing time is 90 seconds; the temperature used in the baking hardening process is 100 DEG C, and the baking time is 10 minutes.

[0063] The laser wavelength of the cutting machine is 1342 nm, and the cutting speed is 300 mm / s.

[0064] In this example, when the silicon-based full-dielectric terahertz metamaterial chip with different groove depths is evaluated, the performance is tested on a terahertz time-domain spectrum (TDS-TDS) system test device, a chip loading platform is installed and fixed in the transmission light path measurement area of the TDS-TDS system, and then the silicon-based full-dielectric terahertz metamaterials with etched 14 and 20 μm grooves are placed into the chip loading platform, and the end with the groove is processed towards the incident direction of the terahertz wave.

[0065] When excited, the terahertz emitter 1 in the TDS-TDS system emits a terahertz wave 2, which is incident from one end of the metamaterial chip, and the terahertz incident wave of a specific frequency band will form multiple local surface plasmon resonances on the surface of the processed silicon-based full-dielectric terahertz metamaterial, and then is emitted from the other end without processing the groove, and the emitted terahertz wave 6 is detected by the terahertz detector 7 in the TDS-TDS system. The resonance performance of the metamaterial is represented by the quality factor Q: Q = f / FWHM, wherein f and FWHM are the resonance frequency and the full width at half maximum of the transmission spectrum of the silicon-based full-dielectric terahertz metamaterial, respectively.

[0066] As can be seen from the results of the display of the analysis device 8 in the figure, two resonance peaks are excited in the experimental transmission spectrum, and the Q value decreases with the increase of the groove depth. Among them, when the groove depth is 14 μm, the first-order and second-order resonance frequencies are 0.6755 and 0.8119, and the Q values are 124.8 and 62.5, respectively; when the groove depth is 20 μm, the first-order and second-order resonance frequencies are 0.6771 and 0.8104, and the Q values are 47.8 and 44.7, respectively.

[0067] The above test results show that the silicon-based full-dielectric terahertz metamaterial prepared by combining multiple photoetching and deep silicon etching microprocessing processes has good performance, stable structure, high quality factor of resonance frequency, and can support multiple terahertz surface resonance modes, and is very suitable for application in various high-performance terahertz functional devices. Therefore, the terahertz metamaterial of the present application has good application prospect.

[0068] Although the present application has been described in detail through specific embodiments, those skilled in the art should understand that any form and detail changes made on the basis of the present application, without exceeding the scope of the claims, are within the scope of the present application.

Claims

1. A method for preparing a silicon-based all-dielectric terahertz metamaterial device with surface structure capable of supporting multiple resonances in the terahertz waveband, characterized in that: The surface structure forms a multiple resonance structure of a terahertz wave band with groove and via structure units etched periodically on the surface of the silicon wafer; the groove and via structure units are composed of a groove, a protrusion and two vias in the middle of the groove; when the surface structure induces electromagnetic waves, one end of the groove is towards the incident end of the terahertz wave, and the other end without the groove is towards the emission end of the terahertz wave; The preparation of the silicon-based full-dielectric terahertz metamaterial device comprises the following steps: Step S1: coating photoresist on the silicon wafer, copying the periodic groove pattern on the mask to the photoresist through a photoetching process, and etching the exposed groove position of the silicon wafer through deep silicon etching to form grooves with different depths; Step S2: coating photoresist on the silicon-based terahertz metamaterial with the groove pattern processed in step S1, copying the via structure to the photoresist through a photoetching process, and further etching the exposed via structure area through deep silicon etching; The silicon wafer is a silicon wafer surface with a thickness of 200 μm; the groove and via structure units are etched uniformly in rows and columns on the silicon surface, and the period is 260 and 130 μm; in the groove and via structure units, the groove width is 130 μm, and the depth is 14 and 20 μm respectively, the protrusion width is 130 μm, and the size of the two vias is 80 μm; In step S1, the exposed groove position of the silicon wafer is etched through deep silicon etching to form grooves with a depth of 14 and 20 μm.

2. The method of claim 1, wherein the method further comprises: In step S1, the specific method is: Step S11: sequentially placing the silicon wafer in acetone and isopropyl alcohol solutions for ultrasonic cleaning to remove surface contaminants, and then performing plasma treatment to improve surface activity; Step S12: placing the treated silicon wafer on a spin coater, then dropping an appropriate amount of photoresist, and performing two uniform glue treatments at a uniform speed; then placing the sample with the spin-coated photoresist on a hot plate for baking to enhance the adhesion of the photoresist; Step S13: projecting the groove pattern on the mask to the photoresist film through the MA6 photoetching machine, and then performing exposure treatment, The photoresist film undergoes a degradation reaction and can be dissolved in a developer, and then the photoresist film is developed to form a groove pattern Coating on the silicon wafer, and then performing a hard film treatment to enhance the adhesion of the photoresist film; Step S14: placing the silicon wafer with the photoresist pattern on the surface in an ICP etching machine, and performing deep silicon etching based on the Bosch etching process, specifically: circulating and alternately introducing the passivation gas C4F8 and the etching gas SF6 in the etching machine to perform the passivation-etching chemical reaction on the silicon wafer, thereby transferring the groove pattern on the photoresist to the silicon wafer; Step S15: sequentially placing the silicon wafer in acetone and isopropyl alcohol solutions for ultrasonic cleaning, blowing dry with an air gun, and then performing plasma cleaning to remove the photoresist and impurities remaining in the groove.

3. The method of claim 1, wherein the method further comprises: In step S2, the specific method is: Step S21: placing the silicon wafer with the groove pattern on a spin coater for two times of glue spraying treatment; then placing the silicon wafer sample with the sprayed photoresist on a hot plate for baking to enhance the adhesion of the photoresist; Step S22: project the via pattern on the mask onto the photoresist film by the MA6 photoetching machine, and then perform an exposure process to make the exposed part of the photoresist undergo a degradation reaction and be soluble in the developing solution, and then perform a developing process to form a via pattern on the photoresist film on the silicon wafer, and then perform a hard baking process to enhance the adhesion of the photoresist film; Step S23: place the silicon wafer with the photoresist pattern on the surface in the ICP etching machine to perform deep silicon etching based on the Bosch etching process, specifically: alternately and cyclically introduce the passivation gas C4F8 and the etching gas SF6 into the etching machine to perform the passivation-etching chemical reaction on the silicon wafer, thereby transferring the via pattern on the photoresist to the silicon wafer to form a silicon surface with a preset via; Step S24: sequentially place the silicon wafer with the preset groove and via into the acetone and isopropyl alcohol solutions for ultrasonic cleaning, blow dry with an air gun, and then perform plasma cleaning to remove the excess photoresist and residual silicon impurities in the via.

4. The method of claim 1, wherein the method further comprises: The silicon wafer processed in step S2 is cut by a cutting machine to divide it into four 15 mm×15 mm silicon-based full-dielectric terahertz metamaterial array structures with a groove depth of 14 μm and four 15 mm×15 mm silicon-based full-dielectric terahertz metamaterial array structures with a groove depth of 20 μm.

5. The method of claim 2, wherein the method further comprises: In the ultrasonic cleaning, ultrasonic cleaning is performed in acetone for 10 minutes and in isopropyl alcohol for 5 minutes; in the plasma cleaning, the time is 5 minutes; the photoresist is AZ6130; when the spin coater performs the spin coating process, the first rotation speed is 500 rpm, the spin coating time is 5 seconds, the second rotation speed is 2000 rpm, the spin coating time is 30 seconds, the baking temperature of the baking machine is 100℃, and the baking time is 3 minutes; in the exposure process, the exposure time of the groove pattern is 3.2 seconds; the developing solution is TMAH developing solution with a concentration of 2.38%, and the developing time is 50 seconds; the baking temperature of the hard baking process is 100℃, and the baking time is 3 minutes; the groove etching depth of the Bosch etching process is 14 and 20 μm, and the via etching depth is 200 μm; in this process, the flow rate of the passivation gas C4F8 is 190 sccm, the flow rate of the etching gas SF6 is 450 sccm, and the etching rate is 5.04 μm / min.

6. The method of claim 3, wherein the method further comprises: The photoresist is RS220; in the photoresin spraying process, the spraying temperature is 100℃, the spraying air pressure is 0.5 mbar, and the spraying distance is 50 mm; In the exposure process, the exposure time of the via pattern is 15 seconds; the developing solution is TMAH developing solution with a concentration of 2.38%, and the developing time is 90 seconds; the baking temperature of the hard baking process is 100℃, and the baking time is 10 minutes.

7. The method of claim 4, wherein the method further comprises: The laser wavelength of the cutting machine is 1342 nm, and the cutting speed is 300 mm / s.

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