A method for peeling a substrate of a micro coaxial transmission line and a micro coaxial transmission line

Abstract

The present invention provides a method for peeling a substrate of a micro-coaxial transmission line and a micro-coaxial transmission line, belonging to the technical field of micro-coaxial production. The peeling method includes: obtaining a wafer substrate; wherein the wafer substrate is made of a transparent material; bonding a metal sheet on the wafer substrate; preparing a micro-coaxial transmission line on the metal sheet; wherein, the metal activity of the metal sheet is stronger than that of copper; performing laser debonding process on the wafer substrate and the metal sheet to debond them, so that the wafer substrate is separated from the metal sheet. This peeling method is simple and efficient in operation, and can conveniently and non-destructively separate the wafer substrate from the device after processing the micro-coaxial device, maintaining the integrity and performance of the device; moreover, the substrate will not be damaged after separation and can be reused repeatedly, which can save materials and production costs.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-coaxial production, and in particular to a method for stripping a micro-coaxial transmission line substrate and a micro-coaxial transmission line. Background Art

[0002] Micro-coaxial transmission lines, as the basic circuit unit of radio frequency devices fabricated using micro-electromechanical systems (MEMS) technology, offer numerous advantages, including small size, light weight, low loss, high isolation, and excellent heat dissipation. In recent years, they have become a hot topic in millimeter-wave radio frequency technology research. During the production process, micro-coaxial transmission lines are typically fabricated on a silicon wafer substrate through a multi-layer stacking process, such as thick-resist photolithography, electroplating, and planarization. Finally, sacrificial layer release technology is used to achieve device formation. In micro-coaxial transmission line devices, the outer conductor itself is similar to an independent packaging structure. In many cases, the bottom surface of the outer conductor is directly grounded. After processing, it loses its primary function as a substrate carrier during device processing. Therefore, micro-coaxial devices typically remove the wafer used as a substrate during processing.

[0003] Prior art CN115411476A discloses a miniaturized, all-metal micro-coaxial microwave filter chip comprising a filter outer conductor, a micro-coaxial inner conductor, and a radio frequency port. The solution disclosed in this application utilizes a micro-coaxial process for layered fabrication. Micromachining processes, including spin coating of photoresist, photoresist smearing, drying, exposure, development, electroforming, grinding, and polishing, are repeated on a silicon wafer substrate. After each layer is fabricated, the silicon wafer substrate is removed using a grinding process, and finally, the photoresist is removed to complete the filter fabrication. However, the use of a grinding process to remove the substrate causes irreversible damage to the substrate and inevitably damages the bottom surface of the device layer adjacent to the substrate.

[0004] Therefore, there is a need to improve the existing method of removing the substrate of the micro-coaxial transmission line to overcome the defects of the prior art. Summary of the Invention

[0005] In order to overcome the problems existing in the related art, one of the objectives of the present invention is to provide a method for stripping a micro-coaxial transmission line substrate. The stripping method is simple and efficient to operate. After the micro-coaxial device is processed, the wafer substrate and the device can be conveniently and losslessly separated from each other, thereby maintaining the integrity and performance of the device. Moreover, the substrate will not be damaged after separation and can be reused repeatedly, which can save material and production costs.

[0006] A method for stripping a micro-coaxial transmission line substrate, comprising:

[0007] Obtaining a wafer substrate; wherein the wafer substrate is made of a transparent material;

[0008] Bond a metal sheet on a wafer substrate;

[0009] Fabricate a micro coaxial transmission line on the metal sheet; wherein, the metal activity of the metal sheet is stronger than that of copper;

[0010] Use a laser debonding process to debond the wafer substrate and the metal sheet, so that the wafer substrate and the metal sheet are separated.

[0011] In a preferred technical solution of the present invention, after separating the wafer substrate and the metal sheet, it further includes:

[0012] Use an etching solution to remove the metal sheet, and complete the peeling of the micro coaxial transmission line and the metal sheet.

[0013] In a preferred technical solution of the present invention, the bonding of the metal sheet on the wafer substrate includes:

[0014] Coat a bonding adhesive on the wafer substrate and perform preliminary baking;

[0015] Coat a bonding adhesive on the metal sheet and bake;

[0016] Oppositely bond the bonding adhesive on the wafer substrate and the bonding adhesive on the metal sheet, and bond the substrate and the metal sheet by means of vacuum hot pressing.

[0017] In a preferred technical solution of the present invention, the bonding adhesive is a laser-separable liquid bonding adhesive.

[0018] In a preferred technical solution of the present invention, after using the laser debonding process to debond the wafer substrate and the metal sheet, it further includes:

[0019] Use a cleaning agent to clean and wipe off the residual bonding adhesive on the surfaces of the wafer substrate and the iron foil sheet.

[0020] In a preferred technical solution of the present invention, the wafer substrate is a light-transmitting wafer, and the surface roughness Ra of the wafer substrate is < 0.5 nm, the thickness is 0.5 - 1 mm, and the TTV is less than 10 μm.

[0021] In a preferred technical solution of the present invention, the size of the cross-section of the metal sheet is the same as that of the cross-section of the wafer substrate; the thickness of the metal sheet is 0.2 mm - 0.5 mm. [[ID=4,2]]

[0022] In a preferred technical solution of the present invention, the fabrication of the micro coaxial transmission line on the metal sheet includes:

[0023] [[ID=,46]]Fabricate the micro coaxial transmission line by using the processes of seed layer growth, thick film lithography, copper electroplating, and planarization;

[0024] And the thickness of the seed layer is greater than 0.5 μm.

[0025] A second object of the present invention is to provide a micro coaxial transmission line. During the manufacturing process of the transmission line, the substrate is peeled off by using the peeling method of the micro coaxial transmission line substrate as described above to obtain the main body of the micro coaxial transmission line.

[0026] In a preferred technical solution of the present invention, the main body of the micro coaxial transmission line includes an outer conductor, an inner conductor, and an inner conductor support layer. The outer conductor is disposed around the inner conductor, and the inner conductor support layer penetrates through the inner conductor and is connected to the outer conductor.

[0027] The beneficial effects of the present invention are as follows:

[0028] A peeling method for a micro coaxial transmission line substrate provided by the present invention includes: obtaining a wafer substrate, where the wafer substrate is made of a transparent material; bonding a metal sheet on the wafer substrate; preparing a micro coaxial transmission line on the metal sheet, where the metal activity of the metal sheet is stronger than that of copper; using a laser debonding process to debond the wafer substrate and the metal sheet, so that the wafer substrate and the metal sheet are separated. This peeling method is simple and efficient. During the production process, the metal sheet is bonded to the wafer substrate, and after the preparation of the micro coaxial transmission line on the metal sheet is completed, the laser debonding process can be used to separate the wafer substrate from the device without damaging the micro coaxial device, which can ensure the integrity and performance of the device. Compared with the traditional physical or chemical peeling methods, the laser debonding process is more simple and efficient in operation. And since the wafer substrate will not be damaged during the separation process, it can be reused after appropriate cleaning and treatment, reducing the demand for new materials, thereby saving material costs and production costs.

[0029] The present application also provides a micro coaxial transmission line manufactured by using the above peeling method for a micro coaxial transmission line substrate. Since the micro coaxial transmission line uses a non-destructive peeling method, the structure of the micro coaxial transmission line will not be damaged during the peeling process, ensuring the integrity and reliability of the device. Moreover, the substrate in the production process can be reused, so that the micro coaxial transmission line has better cost-effectiveness in the market by saving material and production costs. Description of the Drawings

[0030] Reference Signs:

[0031] 1. Substrate; 2. Bonding Adhesive; 3. Metal Sheet; 4. Seed Layer; 100. Outer Conductor; 200. Inner Conductor; 300. Inner Conductor Support Layer.

[0032] Figure 1 is a flowchart of the peeling method for a micro coaxial transmission line substrate provided by an embodiment of the present invention;

[0033] Figure 2 is a flowchart of bonding a metal sheet on a wafer substrate provided by an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of a wafer substrate provided by an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of bonding glue coated on a wafer substrate provided by an embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of bonding glue coated on a metal sheet provided by an embodiment of the present invention;

[0037] Figure 6 is a schematic diagram of the structure after bonding a metal sheet and a wafer substrate provided by an embodiment of the present invention;

[0038] Figure 7 is provided by an embodiment of the present invention where a seed layer grows on Figure 5 the metal sheet;

[0039] Figure 8 is a schematic diagram of a micro - coaxial transmission line on a seed layer provided by an embodiment of the present invention;

[0040] Figure 9 is a schematic diagram of a micro - coaxial transmission line after stripping the substrate provided by an embodiment of the present invention;

[0041] Figure 10 is a schematic diagram of a micro - coaxial transmission line after removing the metal sheet provided by an embodiment of the present invention. Detailed implementation manners

[0042] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0043] In the preparation process of micro - coaxial transmission lines disclosed in the prior art, the substrate of the micro - coaxial device is usually removed by grinding. However, the method of removing the substrate by grinding process causes irreversible damage to the substrate, and at the same time, it is impossible to avoid damaging the bottom surface of the device layer adjacent to the substrate.

[0044] Based on this, the present application provides a method for stripping the substrate of a micro - coaxial transmission line.

[0045] Embodiment 1

[0046] As Figures 1 - 2As shown in the figure, a method for peeling a micro - coaxial transmission line substrate provided in this embodiment includes:

[0047] S100. Obtain a wafer substrate 1; wherein the wafer substrate is made of a transparent material; specifically, in the method claimed in this application, the wafer substrate 1 is a light - transmissive wafer, and the surface of the wafer substrate is smooth. The wafer substrate should have good rigidity and flatness. For example, the roughness Ra < 0.5 nm, the thickness is 0.5 - 1 mm, and the total thickness variation (TTV) is less than 10 μm.

[0048] S200. Bond a metal sheet 3 onto the wafer substrate; the metal sheet in this application can be an iron foil sheet.

[0049] In a specific implementation manner, the bonding of the metal sheet onto the wafer substrate includes:

[0050] S201. Coat a bonding adhesive 2 on the wafer substrate and perform preliminary baking;

[0051] Specifically, during the process of coating the bonding adhesive on the wafer substrate, a wafer spin coater can be used for spin - coating. The rotation speed is set to 1500 rpm, and the spin - coating time is 60 seconds to ensure the uniformity of the adhesive layer. The coated wafer substrate is placed in an oven for preliminary baking. The baking conditions are baking at 110 °C for 5 minutes and then at 220 °C for 10 minutes to promote the preliminary curing of the adhesive layer. By precisely controlling the thickness of the coated adhesive and the baking conditions, and using vacuum hot - pressing technology, the bonding strength and stability between the wafer substrate and the metal sheet are ensured, providing a solid foundation for the subsequent preparation of the micro - coaxial transmission line.

[0052] S202. Coat the bonding adhesive 2 on the metal sheet 3 and bake it;

[0053] S203. Oppositely bond the bonding adhesive on the wafer substrate and the bonding adhesive on the metal sheet, and bond the substrate and the metal sheet by vacuum hot - pressing. During the process of coating the bonding adhesive on the metal sheet, a blade scraping method can be used to ensure the uniformity of the adhesive layer.

[0054] More specifically, the bonding adhesive is a laser - separable liquid bonding adhesive. In this application, a liquid bonding adhesive capable of laser debonding treatment is selected. The used laser - separable temporary bonding adhesive can be effectively removed during the subsequent peeling process, enabling the wafer substrate to be reused, improving the material utilization rate, and reducing resource waste.

[0055] S300. Fabricate a micro - coaxial transmission line on the metal sheet; wherein, the metal activity of the metal sheet is stronger than that of copper.

[0056] S400. Use a laser debonding process to debond the wafer substrate and the metal sheet, so that the wafer substrate is separated from the metal sheet.

[0057] Further, after separating the wafer substrate from the metal sheet, the following steps are also included:

[0058] S500: Remove the metal sheet using an etching solution to complete the peeling of the micro coaxial transmission line from the metal sheet. Generally, the micro coaxial transmission line is usually realized by electroplated copper. According to the metal activity series, a solution that can corrode the iron foil but not corrode the metal copper is selected. After separation, the metal sheet and the micro coaxial device on its surface are placed in this etching solution to completely corrode and remove the metal sheet.

[0059] In the process of fabricating existing micro coaxial devices, due to processes such as spin coating, electroplating, and planarization, the substrate must be kept rigid and flat, and a flexible substrate cannot be used. When directly fabricating devices such as micro coaxial transmission lines on a rigid substrate, the bottom surface of the device will be firmly connected to the substrate through the sputtered seed layer, making it difficult to achieve flexible separation. A thinner sacrificial metal substrate has insufficient rigidity and is difficult to maintain the flatness of the substrate during the fabrication of micro coaxial lines. However, if a sacrificial metal substrate with a thick adhesive layer is used, problems such as difficult control during the final removal of the substrate and excessive time will be faced. Therefore, in this application, the temporary bonding method is used to bond the thin sacrificial metal substrate to the flat and rigid wafer substrate, which can effectively solve the above contradictions. The laser debonding process in this application is simple, efficient, and can conveniently separate the rigid substrate after fabricating the micro coaxial device.

[0060] In a better embodiment, after debonding the wafer substrate and the metal sheet using the laser debonding process, the following steps are also included:

[0061] Use a cleaning agent to clean and wipe off the residual bonding glue on the surface of the wafer substrate and the iron foil.

[0062] Specifically, a primary cleaning agent corresponding to the selected bonding glue can be used to clean the residual bonding glue on the surface of the wafer substrate and the iron foil to ensure the cleanliness of the device surface. After the primary cleaning, isopropyl alcohol is used again for final cleaning to remove any possible remaining cleaning agent.

[0063] Further, the size of the cross-section of the metal sheet is the same as the size of the cross-section of the wafer substrate; the thickness of the metal sheet is 0.2 mm - 0.5 mm.

[0064] The perfect match of the cross-sectional sizes of the metal sheet and the wafer substrate can ensure more uniform contact between the two during the bonding process, reducing bonding defects caused by size mismatch. Moreover, the precise size match between the metal sheet and the wafer substrate helps to improve the uniformity of the distribution of the bonding glue, thereby improving the bonding quality and ensuring the stability of the micro coaxial transmission line during the fabrication process.

[0065] Further, the preparation of the micro coaxial transmission line on the metal sheet includes:

[0066] The micro coaxial transmission line is manufactured by processes of seed layer growth, thick photoresist lithography, copper electroplating, and planarization;

[0067] And the thickness of the seed layer 4 is greater than 0.5 μm. In this application, the thickness of the seed layer 4 is restricted to be greater than 0.5 μm, which can provide good electroplating adhesion and conductivity for the manufacture of the micro coaxial transmission line, thereby enhancing the conductive performance of the micro coaxial transmission line.

[0068] More specifically, the process of preparing the micro coaxial transmission line on the metal sheet is as follows:

[0069] Seed layer preparation: By using magnetron sputtering method, a 20-nm-thick metal titanium adhesion layer is sputtered and grown on the surface of the silicon wafer with an oxide layer, and then a seed layer with a thickness greater than 0.5 μm is sputtered on the adhesion layer.

[0070] Thick photoresist lithography: By using a spin coater, a photoresist with a thickness greater than 100 microns is spin-coated on the surface of the seed layer. Commonly used photoresists such as AZ125nXT, etc., and through steps such as curing, baking, exposure, and development, the bottom pattern of the micro coaxial transmission line including the outer conductor and the first layer of the inner conductor of the micro coaxial is obtained.

[0071] Electroplating: Through an electroplating machine, the wafer with the formed photolithography pattern is electroplated with metallic copper, and then the thickness of the metallic copper and the photoresist on the surface of the wafer is controlled to the target thickness by a planarization method. In the electroplating process, methods such as plating solution circulation, cathode oscillation, and rotation can be used to assist in making the electroplated copper thickness uniform.

[0072] Wafer planarization: Commonly used planarization methods include mechanical polishing method. Alumina abrasive is used between the polished surface of the wafer and the cast iron grinding disc, and it is ground under the condition of 40 - 100 revolutions per minute to preliminarily planarize the copper layer and the photoresist on the surface of the wafer, and then the wafer is further planarized by chemical mechanical polishing until the thickness of the copper layer and the photoresist is controlled to reach the target thickness and then stop.

[0073] Embodiment 2

[0074] Please refer to Figures 8 - 10 , this embodiment provides a micro coaxial transmission line. During the manufacturing process of this micro coaxial transmission line, the substrate is peeled off by using the peeling method of the micro coaxial transmission line substrate as described above to obtain the micro coaxial.

[0075] Specifically, the main body of the micro coaxial transmission line includes an outer conductor 100, an inner conductor 200, and an inner conductor support layer 300. The outer conductor 100 is disposed around the inner conductor 200, and the inner conductor support layer 300 penetrates through the inner conductor and is connected to the outer conductor.

[0076] The inner conductor support layer of the present application can be a SiC inner conductor support layer, such that the inner conductor support layer penetrates through and is connected to the inner conductor and the outer conductor, which can ensure that the inner conductor support layer is more firm and not easily deformed. Moreover, by using SiC as the inner conductor support layer, its high hardness and wear resistance make the inner conductor support layer more firm and not easily deformed, thereby improving the overall structural stability of the micro coaxial transmission line. Also, during the manufacturing process of the micro coaxial transmission line, the substrate can be reused, so that by saving materials and production costs, the micro coaxial transmission line has better cost - effectiveness in the market.

[0077] Embodiment 3

[0078] Please refer to Figures 1 - 10 , this embodiment provides a method for manufacturing a micro coaxial transmission line with a sapphire inner conductor support structure to elaborate on the peeling method of the micro coaxial transmission line substrate of the present application. The specific steps are as follows:

[0079] (1) Select a 4 - inch fused silica glass wafer with a thickness of 1 mm, a total thickness variation (TTV) of less than 5 μm, and a surface roughness Ra < 0.5 nm.

[0080] (2) Adopt the temporary bonding glue process to bond the selected wafer substrate and an iron foil together by means of vacuum hot pressing or the like.

[0081] Among them, use WLPTB4130 ultraviolet laser - separable temporary bonding glue. Use a wafer spin coater to evenly spin - coat the bonding glue on the surface of the quartz glass wafer. The rotation speed during the spin - coating process is set at 1500 rpm, and the spin - coating time is 60 s. After spin - coating, the wafer is preliminarily baked. The baking process first bakes at 110 °C for 5 min, and then bakes at 220 °C for 10 min.

[0082] Select a pure iron foil with the same size as the 4 - inch fused silica glass wafer, with a thickness of 0.2 mm and a surface roughness Ra < 1 nm. Also use WLPTB4130 ultraviolet laser - separable temporary bonding glue, scrape and coat it evenly on the surface of the selected iron foil with a blade, and place it in an oven for baking. The baking process first bakes at 110 °C for 5 min, and then bakes at 220 °C for 10 min.

[0083] Then, align the bonding glue surfaces of the fused silica substrate wafer and the iron foil, and place them in a vacuum hot press bonding machine for bonding. During the bonding process, the internal pressure of the vacuum hot press bonding machine is lower than 50 Pa, the hot press temperature is 200 °C, the bonding pressure is set at 0.3 MPa, and the bonding time is 600 s.

[0084] (3) On the surface of the bonded iron foil, complete the preparation of the micro coaxial device by using processes such as seed layer growth, thick photoresist lithography, electroplating copper, and planarization. Specifically, it includes:

[0085] Prepare a metal copper seed layer with a thickness of 0.5 μm on the surface of the iron foil by magnetron sputtering.

[0086] Complete the preparation of the micro coaxial transmission line structure on the surface of the iron foil by using processes such as thick photoresist lithography, electroplating copper, planarization, photoresist release, and seed layer etching commonly used in the micro coaxial structure.

[0087] (4) Use the laser debonding process to separate the selected transparent substrate and the iron foil. Specifically, it includes:

[0088] Use the laser debonding process to scan the bonding glue between the substrate and the iron foil through the wafer substrate to achieve debonding. After laser irradiation, the bonding glue loses its bonding viscosity. Among them, the laser beam uses ultraviolet laser with a wavelength of 355 nm, and the energy is set at 200 mj / cm 2 , and the scanning time is 60 s.

[0089] Clean and erase the residual bonding glue on the surface of the wafer substrate and the iron foil by using the cleaning agent corresponding to the WLPTB4130 bonding glue, and then clean it again with isopropyl alcohol to keep the substrate and the iron foil clean.

[0090] (5) Use a selective etching solution to remove the iron foil and complete the peeling of the micro coaxial transmission line from the iron foil.

[0091] Specifically: Place the incompletely separated iron foil and the micro coaxial transmission line with the metal copper structure in a dilute sulfuric acid solution with a volume fraction of 40%, soak it for more than 2 hours at room temperature, completely corrode and remove the iron foil, and complete the separation of the micro coaxial transmission line and the peeling substrate.

[0092] In addition, it should be noted that using words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without otherwise stating, the above words have no special meaning, so it cannot be understood as a limitation on the protection scope of this application.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for peeling a substrate of a micro coaxial transmission line, characterized in that Including: Obtain a wafer substrate; wherein the wafer substrate is made of a transparent material; Bond a metal sheet on the wafer substrate; Fabricate a microcoaxial transmission line on the metal sheet; wherein, the metal activity of the metal sheet is stronger than that of copper; Use a laser debonding process to debond the wafer substrate and the metal sheet, so that the wafer substrate and the metal sheet are separated.

2. The method for peeling a microcoaxial transmission line substrate according to claim 1, characterized in that: After separating the wafer substrate and the metal sheet, it further includes: Use an etching solution to remove the metal sheet, and complete the peeling of the microcoaxial transmission line and the metal sheet.

3. The method for peeling a microcoaxial transmission line substrate according to claim 1, characterized in that: The bonding of the metal sheet on the wafer substrate includes: Coat a bonding adhesive on the wafer substrate and perform preliminary baking; Coat a bonding adhesive on the metal sheet and bake; Align the bonding adhesive on the wafer substrate with the bonding adhesive on the metal sheet and bond the substrate and the metal sheet by vacuum hot pressing.

4. The method for peeling a microcoaxial transmission line substrate according to claim 3, characterized in that: The bonding adhesive is a laser-separable liquid bonding adhesive.

5. The method for peeling a microcoaxial transmission line substrate according to claim 3, characterized in that: After using the laser debonding process to debond the wafer substrate and the metal sheet, it further includes: Use a cleaning agent to clean and wipe off the residual bonding adhesive on the surface of the wafer substrate and the iron foil sheet.

6. The method for peeling a microcoaxial transmission line substrate according to any one of claims 1-5, characterized in that: The wafer substrate is a light-transmitting wafer, and the surface roughness Ra of the wafer substrate is less than 0.5 nm, the thickness is 0.5-1 mm, and the TTV is less than 10 μm.

7. The method for peeling a microcoaxial transmission line substrate according to any one of claims 1-5, characterized in that: The cross-sectional size of the metal sheet is the same as the cross-sectional size of the wafer substrate; the thickness of the metal sheet is 0.2 mm - 0.5 mm.

8. The method for peeling a microcoaxial transmission line substrate according to any one of claims 1-5, characterized in that: The fabrication of the microcoaxial transmission line on the metal sheet includes: Use processes such as seed layer growth, thick film lithography, copper electroplating, and planarization to fabricate the microcoaxial transmission line; And the thickness of the seed layer is greater than 0.5 μm.

9. A micro coaxial transmission line, characterized in that: During the manufacturing process, use the method for peeling a microcoaxial transmission line substrate according to any one of claims 1-8 to peel the substrate to obtain the main body of the microcoaxial transmission line.

10. The microcoaxial transmission line according to claim 9, characterized in that: The main body of the microcoaxial transmission line includes an outer conductor, an inner conductor, and an inner conductor support layer. The outer conductor is arranged around the inner conductor, and the inner conductor support layer penetrates through the inner conductor and is connected to the outer conductor.

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