Air bridge preparation method, air bridge structure, chip and air bridge preparation system

Abstract

The application discloses an air bridge preparation method, an air bridge structure, a chip and an air bridge preparation system, and relates to the technical field of micro-nano processing. The method comprises the following steps: forming N mound structures on a substrate, the mound structures are in the shape of a column, the mound structures comprise first surfaces and second surfaces opposite to each other, the first surfaces of the N mound structures are connected with the substrate respectively, N is a positive integer; and preparing an air bridge on the substrate with the N mound structures, the second surfaces of the N mound structures are connected with the air bridge respectively. In the method, on the one hand, the mound structures can play a supporting role on the air bridge, thereby improving the stability of the air bridge; on the other hand, since the mound structures are formed before the air bridge, in the air bridge preparation process, the mound structures, as the formed structures, can support and maintain the air bridge material used for forming the air bridge, thereby guaranteeing the smooth formation of the air bridge.

Description

Technical Field

[0001] This application relates to the field of micro-nano fabrication technology, and in particular to an air bridge fabrication method, air bridge structure, chip, and air bridge fabrication system. Background Technology

[0002] An air bridge is a circuit structure that uses a three-dimensional bridge-shaped structure to bridge planar circuits and has wide applications in the chip industry.

[0003] In related technologies, an air bridge includes two piers connecting a base and an arched bridge body between the two piers (the arched bridge body of the air bridge is connected to one side of both the base and the piers). During the fabrication of the air bridge, the piers and the arched bridge body are formed as a single unit. However, when the span of the air bridge is long, the structure of the air bridge becomes unstable. Summary of the Invention

[0004] This application provides a method for fabricating an air bridge, an air bridge structure, a chip, and an air bridge fabrication system. The technical solution provided by this application is as follows:

[0005] According to one aspect of the embodiments of this application, a method for preparing an air bridge is provided, the method comprising:

[0006] N pier structures are formed on the base. The pier structures are columnar in shape and include a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base, where N is a positive integer.

[0007] An air bridge is fabricated on a base having the N pier structures, wherein the second surfaces of the N pier structures are respectively connected to the air bridge.

[0008] According to one aspect of the embodiments of this application, an air bridge structure formed on a substrate is provided, the air bridge structure comprising N pier structures and air bridges, where N is a positive integer;

[0009] The pier structure is columnar in shape, and the pier structure includes a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base.

[0010] The second surfaces of the N pier structures are respectively connected to the air bridge.

[0011] According to one aspect of the present application, a chip is provided, the chip including a substrate and an air bridge, the air bridge being prepared using the air bridge preparation method described above.

[0012] According to one aspect of the embodiments of this application, an air bridge fabrication system is provided, the air bridge fabrication system comprising: a pier structure fabrication device and an air bridge fabrication device;

[0013] The pier structure preparation device is used to form N pier structures on a base. The pier structure is in the shape of a column. The pier structure includes a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base. N is a positive integer.

[0014] The air bridge fabrication apparatus is used to fabricate an air bridge on a substrate having the N pier structures, wherein the second surfaces of the N pier structures are respectively connected to the air bridge.

[0015] The technical solutions provided in this application have at least the following beneficial effects:

[0016] First, a columnar pier structure is formed on the substrate, and then an air bridge is fabricated on the substrate. On the one hand, since the two opposite surfaces of the pier structure connect the substrate and the air bridge respectively, the pier structure can support the air bridge, thereby improving its stability. On the other hand, since the pier structure is formed before the air bridge, it can support and maintain the air bridge material used to form the air bridge during the air bridge fabrication process, thus ensuring the smooth formation of the air bridge. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an arched air bridge provided in one embodiment of this application;

[0018] Figure 2 This is a flowchart of a method for preparing an arched air bridge according to an embodiment of this application;

[0019] Figure 3 This is a schematic diagram of an air bridge structure formed on a substrate according to an embodiment of this application;

[0020] Figure 4 This is a flowchart of an air bridge fabrication method provided in one embodiment of this application;

[0021] Figure 5 This is a schematic diagram of a substrate provided in one embodiment of this application;

[0022] Figure 6 This is a flowchart of an air bridge fabrication method provided in another embodiment of this application;

[0023] Figure 7 This is a schematic diagram of a substrate having a first photoresist layer according to an embodiment of this application;

[0024] Figure 8This is a schematic diagram of a substrate having a processed first photoresist layer according to an embodiment of this application;

[0025] Figure 9 This is a schematic diagram of the substrate after vapor-deposited bridge pier material according to one embodiment of this application;

[0026] Figure 10 This is a schematic diagram of a base with N pier structures provided in one embodiment of this application;

[0027] Figure 11 This is a schematic diagram of a substrate with a second photoresist layer provided in one embodiment of this application;

[0028] Figure 12 This is a schematic diagram of a substrate having a processed second photoresist layer according to an embodiment of this application;

[0029] Figure 13 This is a schematic diagram of the substrate after vapor deposition of air bridge material according to one embodiment of this application;

[0030] Figure 14 This is a schematic diagram of a substrate with an air bridge provided in one embodiment of this application;

[0031] Figure 15 This is a physical schematic diagram of an air bridge structure provided in one embodiment of this application;

[0032] Figure 16 This is a physical schematic diagram of an air bridge structure provided in another embodiment of this application;

[0033] Figure 17 This is a schematic diagram of an air bridge fabrication system provided in one embodiment of this application;

[0034] Figure 18 This is a schematic diagram of an air bridge fabrication system provided in another embodiment of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0036] Before introducing the technical solutions of this application, some terms involved in this application will be explained. The following related explanations are optional solutions and can be arbitrarily combined with the technical solutions of the embodiments of this application, all of which fall within the protection scope of the embodiments of this application. The embodiments of this application include at least some of the following contents.

[0037] Airbridge: A circuit structure used to bridge planar circuits using a three-dimensional bridge-like structure. The specific function of the airbridge will be explained in more detail in the examples below.

[0038] Coplanar waveguide: A transmission device consisting of a central conductor and infinitely large ground planes on both sides, used to transmit microwave signals.

[0039] Lift-off: This is the process in which the underlying photoresist is dissolved in the resist remover, and the material (thin film) attached to the photoresist is also removed along with it.

[0040] Grayscale lithography: This refers to an exposure method in which different exposure doses are applied to different locations in a single exposure.

[0041] Microwave crosstalk: The phenomenon that when microwaves are transmitted in one coplanar waveguide, the corresponding microwave signal can also be detected in another coplanar waveguide.

[0042] Reflow: When photoresist is heated to a certain temperature, the photoresist that has already solidified will regain its fluidity.

[0043] Positive photoresist: After being exposed to light, the photoresist in the exposed areas is eventually removed.

[0044] Negative photoresist: After exposure to light, the photoresist in the unexposed areas is eventually removed, while the photoresist in the exposed areas is eventually retained.

[0045] Superconducting: Below a certain temperature, the electrical resistance of a material abruptly drops to 0, and it exhibits complete diamagnetism.

[0046] In situ: Performing multi-step processes on materials within a single vacuum chamber or multiple interconnected vacuum chambers without exposing the materials to the atmosphere.

[0047] Ion milling: A technique that uses an ion beam to perform milling operations on a solid surface. For example, Ar ions are generated using an ion source and bombarded on a metal surface in a vacuum, thereby removing the natural oxide layer on the metal surface.

[0048] A chip includes important components such as coplanar waveguides and air bridges. An air bridge is generally a three-dimensional bridge structure formed by a thin metal film. In a chip, an air bridge has the following functions: (1) connecting infinite ground planes on both sides of the coplanar waveguide to eliminate the potential difference on both sides of the coplanar waveguide and suppress parasitic modes. (2) serving as a crossover to alleviate wiring congestion caused by the crossing of coplanar waveguides. (3) serving as signal shielding to reduce microwave crosstalk. (4) serving as a coupling device between different structures in the chip.

[0049] A typical air bridge is an arched structure, such as... Figure 1 As shown, the arched air bridge includes piers 11 and a bridge body 12. During the fabrication of the air bridge, the bridge bracing 13 serves to support the bridge body 12, thereby shaping the bridge body 12. The fabrication process of this arched air bridge will be described below.

[0050] Please refer to Figure 2 The flowchart illustrates a method for preparing an arched air bridge according to an embodiment of this application, the method comprising the following steps:

[0051] 1. Provide a substrate for fabricating an arched air bridge.

[0052] 2. Spin-coat the first layer of photoresist onto the substrate.

[0053] 3. Photolithography is performed on the first layer of photoresist to remove the first layer of photoresist on the area corresponding to the bridge pier on the substrate.

[0054] 4. The first layer of photoresist is bridged by high-temperature reflow.

[0055] 5. Remove the oxide layer of the substrate by ion milling.

[0056] 6. Aluminum plating is then applied to the substrate after the above steps have been completed.

[0057] 7. Spin-coat a second layer of photoresist onto the aluminum-plated substrate.

[0058] 8. Photolithography of the second layer of photoresist to remove the second layer of photoresist on the substrate except for the area corresponding to the air bridge.

[0059] 9. Etch away all exposed aluminum film on the substrate.

[0060] 10. Remove all photoresist from the substrate to obtain an arched air bridge.

[0061] In the above-mentioned method for fabricating arched air bridges, the bridge support is formed by photoresist reflow. When the air bridge span is greater than 60µm, the reflow-formed bridge support will appear plateau-shaped, ultimately forming an arched air bridge shape. This shape has poorer stability than an arch. Figure 1As shown, after the photoresist forming the bridge support 13 is released, if the span of the air bridge is large, the bridge body 12 will be difficult to maintain stability. Therefore, the span of the above-mentioned arched air bridge is limited.

[0062] With the development of chip technology, long-distance connections have become a new requirement, and the aforementioned arched air bridge is unable to meet this requirement due to its limited span.

[0063] Based on the above problems, this application provides a new air bridge structure. The piers (pier structures) of this air bridge structure are columnar in shape, and the air bridge is laid on the columnar piers. Since the density and number of piers can be arbitrarily set in the above air bridge structure, air bridges of any length can be realized, so it can be used for long-distance connections.

[0064] Please refer to Figure 3 The diagram illustrates an air bridge structure formed on a substrate according to an embodiment of this application. The air bridge structure includes N pier structures 31 and air bridges 32, where N is a positive integer.

[0065] The pier structure 31 is columnar in shape. For example, the column shape can be cylindrical, prism, etc., and this application does not limit it in this respect.

[0066] The pier structure 31 includes a first surface and a second surface that are positioned opposite each other, and the first surfaces of the N pier structures 31 are respectively connected to the base 50.

[0067] In some embodiments, the first surface and the second surface are parallel. In some embodiments, the first surface and the second surface are congruent.

[0068] As can be seen, in the above-mentioned air bridge structure, the two opposite surfaces of the column-shaped pier structure 31 connect one to the base and the other to the air bridge. Therefore, the pier structure 31 can support the air bridge 32, keeping it stable. With a sufficient number of pier structures 31, the span of the air bridge can be extended indefinitely, no longer limited by the stability issue of the air bridge.

[0069] The following embodiments will describe in detail how the air bridge is prepared. For details not described in the air bridge structure embodiments, please refer to the air bridge preparation method embodiments below.

[0070] Please refer to Figure 4 The diagram shows a flowchart of an air bridge fabrication method provided in one embodiment of the present application, which includes at least one of the following steps 410 to 420.

[0071] Step 410: Form N pier structures on the base. The pier structures are columnar in shape and include a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base, where N is a positive integer.

[0072] The substrate is the basic material for fabricating air bridges, and it can be a chip semi-finished product that integrates some electronic devices and electronic circuits.

[0073] In some embodiments, the substrate includes a substrate and devices formed on the substrate. The substrate is the basic material used to support and build other functional layers during chip fabrication.

[0074] In some embodiments, the substrate material is silicon (Si) or sapphire (Al2O3), and the thickness is 300-500 μm.

[0075] In some embodiments, please refer to Figure 5 The substrate 50 includes a substrate 501 and a coplanar waveguide 502. The coplanar waveguide 502 includes a central conductor 503 and conductor planes 504 (semi-infinite ground planes) located on both sides of the central conductor 503. The material of the coplanar waveguide 502 is a superconducting thin film, such as aluminum (Al), niobium (Nb), titanium nitride (TiN), tantalum (Ta), etc. The trench between the central conductor 503 and the conductor planes 504 is prepared by conventional photolithography and etching processes.

[0076] In some embodiments, the entire area of ​​the first surface of the N pier structures is connected to the base.

[0077] In some embodiments, please refer to Figure 6 Step 410 includes at least one sub-step from steps 411 to 414.

[0078] Sub-step 411: Apply the first photoresist to the substrate to form the first photoresist layer.

[0079] In the embodiments of this application, "on the substrate" refers to the surface of the substrate, and this will not be elaborated further hereafter.

[0080] In some embodiments, a first photoresist is spin-coated onto a substrate. After spin-coating the first photoresist, the first photoresist is heated to evaporate the solvent used in spin-coating the first photoresist, thereby solidifying the first photoresist to obtain a first photoresist layer.

[0081] For example, a first photoresist is spin-coated onto a substrate using a spin coater with a rotation speed of 600 RPM (Revolutions Per Minute). After spin-coating the first photoresist, the substrate is heated for 90 seconds using a hot plate at 100 degrees Celsius to obtain the first photoresist layer.

[0082] For example, please refer to Figure 5 A first photoresist is applied to the substrate 50 to obtain the following result: Figure 7 The substrate 51 shown has a first photoresist layer, and it can be seen that the first photoresist layer 505 is cured on the substrate 50.

[0083] Sub-step 412 involves exposing and developing the first photoresist layer to remove the first photoresist from N regions of the substrate, resulting in the processed first photoresist layer.

[0084] The N regions of the base refer to the surface areas of the base, which are used to connect the N pier structures.

[0085] In some embodiments, exposure and development are performed on the first photoresist layer to remove the first photoresist on N regions of the substrate, such that the N regions are not in contact with the first photoresist (so that the N regions are exposed from the first photoresist layer), resulting in a processed first photoresist layer.

[0086] In some embodiments, exposure and development are performed on the first photoresist layer to remove N first photoresist pillars in the first photoresist layer, resulting in a processed first photoresist layer. The first photoresist pillars are pillar-shaped and include a first surface and a second surface positioned opposite each other. The first surface of each first photoresist pillar contacts one of the aforementioned N regions. The second surface of each second photoresist pillar occupies a portion of the first surface of the first photoresist layer. The first surface of the first photoresist layer is the surface of the first photoresist layer that does not contact the substrate.

[0087] In some embodiments, the first photoresist layer is exposed to obtain the exposed first photoresist layer, the exposed first photoresist layer is then baked (heated) to obtain the baked first photoresist layer, and the baked first photoresist layer is then developed (immersed in a developing solution) to obtain the processed first photoresist layer.

[0088] For example, using 1550mj / cm 2 The first photoresist layer is exposed to a specific exposure dose to obtain the exposed first photoresist layer. After exposure, the substrate with the exposed first photoresist layer is heated to 100 degrees Celsius using a hot plate for 90 seconds to obtain the post-baked first photoresist layer. The substrate with the post-baked first photoresist layer is then immersed in a developing solution for 140 seconds to obtain the processed first photoresist layer.

[0089] In some embodiments, the first photoresist described above is a negative photoresist, and step 412 includes the following steps:

[0090] 1. Expose the first photoresist in the areas other than N regions of the first photoresist layer to obtain the exposed first photoresist layer.

[0091] In some embodiments, laser direct writing (e.g., using a laser direct writing device) is used to expose the first photoresist on the regions other than N regions in the first photoresist layer to obtain the exposed first photoresist layer.

[0092] In some embodiments, a first photoresist layer is covered on N regions using a mask, and the first photoresist layer is exposed (e.g., exposed using an ultraviolet exposure machine) to obtain the exposed first photoresist layer.

[0093] In some embodiments, exposure is performed on the remaining area of ​​the first surface of the first photoresist layer, excluding the second surfaces of each of the N first photoresist pillars, to obtain the exposed first photoresist layer.

[0094] In some embodiments, laser direct writing is used to expose the remaining area of ​​the first surface of the first photoresist layer, excluding the second surfaces of each of the N first photoresist pillars, to obtain the exposed first photoresist layer.

[0095] In some embodiments, a mask is used to cover the area occupied by the second surfaces of each of the N first photoresist pillars on the first surface of the first photoresist layer, and exposure is performed on the first surface of the first photoresist layer to obtain the exposed first photoresist layer.

[0096] 2. Develop the first photoresist layer after exposure to remove the first photoresist in N areas and obtain the processed first photoresist layer.

[0097] In some embodiments, development is performed on the exposed first photoresist layer to remove N first photoresist pillars in the first photoresist layer, resulting in a processed first photoresist layer.

[0098] In the above embodiment, the first photoresist is a negative photoresist. Therefore, when using mask exposure, it is only necessary to use a mask to cover the first photoresist on the N areas where the pier structure is to be set.

[0099] In some embodiments, the first photoresist described above is a positive photoresist, and step 412 includes the following steps:

[0100] 1. Expose the first photoresist in N regions of the first photoresist layer to obtain the exposed first photoresist layer.

[0101] In some embodiments, laser direct writing (e.g., using a laser direct writing device) is used to expose the first photoresist on N regions to obtain the exposed first photoresist layer.

[0102] In some embodiments, a mask is used to cover the first photoresist in areas other than N regions of the first photoresist layer, and the first photoresist layer is exposed (e.g., exposed using an ultraviolet exposure machine) to obtain the exposed first photoresist layer.

[0103] In some embodiments, exposure is performed on the second surfaces of each of the N first photoresist pillars in the first surface of the first photoresist layer to obtain the exposed first photoresist layer.

[0104] In some embodiments, laser direct writing is used to expose the area occupied by the second surface of each of the N first photoresist pillars on the first surface of the first photoresist layer to obtain the exposed first photoresist layer.

[0105] In some embodiments, a mask is used to cover the remaining area of ​​the first surface of the first photoresist layer, excluding the second surfaces of each of the N first photoresist pillars, and exposure is performed on the first surface of the first photoresist layer to obtain the exposed first photoresist layer.

[0106] For example, please refer to Figure 7 Exposure is performed on the second surface 507 of each of the N first photoresist pillars in the first surface 506 of the first photoresist layer 505 to obtain the exposed first photoresist layer.

[0107] 2. Develop the first photoresist layer after exposure to remove the first photoresist in N areas and obtain the processed first photoresist layer.

[0108] In some embodiments, development is performed on the exposed first photoresist layer to remove N first photoresist pillars in the first photoresist layer, resulting in a processed first photoresist layer.

[0109] For example, for adopting such Figure 7 The first photoresist layer obtained after exposure, as shown in the method, is developed to obtain the following: Figure 8 The substrate 52 shown has a processed first photoresist layer. As can be seen, since the first photoresist on N regions is removed, the processed first photoresist layer 508 has N hollow structures 509, so that the N regions on the substrate 50 are directly exposed without being covered by the first photoresist.

[0110] In the above embodiment, the first photoresist is a positive photoresist. Therefore, when using laser direct writing for exposure, the laser only needs to target the first photoresist on the N areas where the support structure is to be set, thereby reducing the implementation complexity of laser direct writing.

[0111] Sub-step 413: On the substrate with the processed first photoresist layer, the bridge pier material is vapor-deposited to obtain the substrate after vapor-depositing the bridge pier material.

[0112] In some embodiments, the pier material is a metallic material, such as an indium film.

[0113] In some embodiments, the thickness of the pier material is about 3 μm, for example, 1 μm to 5 μm.

[0114] For example, a 3µm indium film is deposited on a substrate having a treated first photoresist layer using a thermal evaporation apparatus to obtain a substrate after evaporation of bridge pier material.

[0115] It should be noted that since the N regions on the substrate with the processed first photoresist layer are directly exposed without being covered by the first photoresist, in this sub-step, the pier material is not only deposited on the processed first photoresist layer, but also deposited on the N regions. This portion of the pier material on the N regions is the pier material required to form the N pier structures.

[0116] In some embodiments, the thickness of the pier material in the N regions is less than the thickness of the first photoresist layer. Therefore, the pier material in the N regions will not connect with the pier material on the processed first photoresist layer, so that during the subsequent stripping process, the pier material on the processed first photoresist layer will be removed along with the first photoresist, thereby ensuring the smooth formation of the pier structure.

[0117] For example, in such Figure 8 The bridge pier material is deposited on the substrate 52 with the processed first photoresist layer, as shown, to obtain... Figure 9 As shown in the substrate 53 after the pier material is vapor-deposited, it can be seen that the pier material 510 of the same thickness is vapor-deposited on the processed first photoresist layer 508 and N regions of the substrate 50.

[0118] Sub-step 414 involves removing the processed first photoresist layer from the substrate after the bridge pier material has been vapor-deposited, resulting in a substrate with N pier structures.

[0119] In some embodiments, the substrate after the pier material is vapor-deposited is immersed in a photoresist remover solution, so that the pier material on the first photoresist layer is removed from the substrate along with the first photoresist layer (i.e., peeling occurs), while the pier material in the N regions is retained on the substrate because it is directly vapor-deposited on the substrate, thereby forming a substrate with N pier structures.

[0120] In some embodiments, the adhesive remover is NMP (N-methylpyrrolidone) adhesive remover commonly used in micro-nano processing, or Remover PG adhesive remover; this application does not limit the specific type of adhesive remover.

[0121] In some embodiments, the adhesive remover can be heated in an 80°C water bath to improve the adhesive removal effect; optionally, the water bath heating time can be selected as 2 hours. To achieve good cleanliness, the adhesive remover can be replaced multiple times, and the peeled-off bridge pier material and debris should be cleaned up in a timely manner.

[0122] In some embodiments, the substrate having N pier structures is cleaned with isopropanol and dried with a nitrogen gun to facilitate the subsequent fabrication of air bridges.

[0123] For example, such as Figure 9 As shown, the processed first photoresist layer 508 is removed from the substrate 53 after the bridge pier material is vapor-deposited, resulting in the following: Figure 10 The substrate 54 shown has N pier structures. It can be seen that the N pier structures 31 are connected to the substrate 50 and will not be removed when the first photoresist is removed.

[0124] In the above embodiment, the portion for setting the pier structure is first photolithographically etched in the first photoresist layer on the substrate, and then the pier material is vapor-deposited. Since the pier material connected to the substrate is not peeled off along with the first photoresist, the pier structure can finally be formed on the substrate. Furthermore, in the above method, the pier structure is formed based on the pier material vapor-deposited on N regions, and the thickness of the pier material also determines the height of the air bridge. Since the thickness of the vapor-deposited pier material (such as indium film) can be precisely controlled by a film thickness gauge, compared with the arched air bridge (the height needs to be determined by high-temperature reflow bridge support and cannot be precisely controlled), the height of the air bridge provided in this application embodiment can be precisely controlled, thereby improving the performance of the air bridge (if the height of the air bridge is too low, the air bridge will form parasitic capacitance or inductance with the metal on the substrate, affecting the device performance (except in special cases where the air bridge is intentionally used as a capacitor structure); if the height of the air bridge is too high, the microwave shielding effect of the air bridge will be weakened).

[0125] In some embodiments, the pier material is a metallic material. Before step 410, the above-described air bridge preparation method further includes the following steps:

[0126] The substrate is etched to remove the metal layer in N regions of the substrate, resulting in an etched substrate, which is then used to form N pier structures.

[0127] For example, the substrate is etched to remove the metal thin film used for the coplanar waveguide (conductor plane) in N regions of the substrate, resulting in an etched substrate.

[0128] In the above method, before forming N pier structures on the substrate, the metal layer in the N regions used to set the N pier structures is first etched away, so that the N pier structures formed subsequently are directly connected to the non-metallic substrate (such as Si). This method is suitable for scenarios where it is not desirable for metal pier structures to connect air bridges made of metal materials and metal layers on the substrate at the same time.

[0129] Step 420: On a base with N pier structures, an air bridge is fabricated, and the second surfaces of the N pier structures are respectively connected to the air bridge.

[0130] In some embodiments, the entire area of ​​the second surface of the pier structure is connected to an air bridge.

[0131] In some embodiments, a portion of the second surface of the pier structure is connected to an air bridge.

[0132] In some embodiments, please refer to Figure 6 Step 420 includes at least one of the following sub-steps 421 to 425.

[0133] Sub-step 421: On the substrate having N pier structures, a second photoresist is applied to form a second photoresist layer.

[0134] In some embodiments, a second photoresist is spin-coated onto a substrate having N pile structures. After spin-coating the second photoresist, the second photoresist is heated to evaporate the solvent used in spin-coating the second photoresist, thereby curing the second photoresist to obtain a second photoresist layer.

[0135] In some embodiments, the thickness of the second photoresist layer is greater than the height of the pier structure (the thickness of the pier material).

[0136] For example, a second photoresist is spin-coated onto a substrate with N pier structures using a spin coater with a rotation speed of 1000 RPM. Then, the second photoresist (substrate) is baked on a hot plate at 115 degrees Celsius for 90 seconds to cure the second photoresist, resulting in a second photoresist layer with a thickness of 4.2 μm. The second photoresist layer is thus able to cover the pier structures with a height of 3 μm.

[0137] For example, in such Figure 10 On the substrate 54 with N pier structures shown, a second photoresist is coated to obtain the following: Figure 11 The substrate 55 shown has a second photoresist layer, and it can be seen that the second photoresist layer 511 is cured on the substrate 54 having N pile structures.

[0138] In some embodiments, the second photoresist is a positive photoresist, which facilitates the use of different exposure intensities for different portions of the second photoresist to achieve grayscale exposure.

[0139] Sub-step 422: Perform grayscale exposure on the first region of the first surface of the second photoresist layer to obtain the grayscale exposed second photoresist layer, wherein the first surface of the second photoresist layer is the surface of the second photoresist layer that is not in contact with the substrate.

[0140] Grayscale exposure is performed on the first region, that is, exposure is performed with different exposure intensities (or exposure doses) for different positions in the first region.

[0141] The first area is designated by the technicians and is used to perform grayscale exposures to form the structure of the air bridge.

[0142] In some embodiments, sub-step 422 includes at least one of the following steps:

[0143] 1. Obtain the contrast curve of the second photoresist layer. The contrast curve is used to reflect the relationship between the exposure intensity of the first surface of the second photoresist layer and the remaining thickness of the second photoresist layer after exposure and development.

[0144] The exposure intensity for exposing the first surface of the second photoresist layer can be controlled by the exposure equipment. For example, in the case of a laser direct writing device, the exposure intensity can be controlled by adjusting parameters such as the power, intensity, filter, and focus of the laser direct writing device.

[0145] In some embodiments, a standard 256-level grayscale image is used as an exposure template to expose the experimental second photoresist layer (the surface not in contact with the substrate). Each grayscale level in the exposure template corresponds to a proportion of the maximum exposure dose of the exposure equipment. For example, the first grayscale level corresponds to 0 / 255 of the exposure intensity, and the second grayscale level corresponds to 255 / 255 of the exposure intensity. After exposing the experimental second photoresist layer, it is developed, for example, using an alkaline developer for 50 seconds, to obtain the developed experimental second photoresist layer. After completing the above steps, since the exposure intensities corresponding to different grayscale levels are different, the remaining thickness of the developed experimental second photoresist layer will also vary at different locations (different locations correspond to different grayscale levels). By measuring the remaining thickness at each grayscale level using equipment such as a profilometer or confocal microscope, the contrast curves described above can be plotted.

[0146] Additionally, it should be noted that the parameters of the second photoresist layer used for measuring the contrast curve should be consistent with those of the second photoresist layer (e.g., consistent thickness, consistent type of photoresist, and consistent parameters of the substrate).

[0147] 2. Based on the design parameters of the air bridge, find the corresponding exposure intensity for each position in the first region from the contrast curve.

[0148] In some embodiments, the design parameters of the air bridge include the height of each position of the air bridge (i.e., the distance from each position to the substrate). For the air bridge to meet a set height at a certain position, the remaining photoresist thickness of the processed second photoresist layer at the corresponding position must also meet that set height. Therefore, the exposure intensity corresponding to each position in the first region can be looked up from the contrast curve based on the set height of each position of the air bridge. That is, in this step, the exposure intensity corresponding to each position in the first region is set according to the design shape of the air bridge, thereby precisely controlling the remaining photoresist thickness at each position in the processed second photoresist layer, and thus ensuring that the final air bridge conforms to the design shape.

[0149] 3. Perform grayscale exposure on the first region according to the exposure intensity corresponding to each position in the first region obtained by query, and obtain the second photoresist layer after grayscale exposure.

[0150] For example, please refer to Figure 11 According to the exposure intensity corresponding to each position in the first region 512 obtained by query, grayscale exposure is performed on the first region 512 to obtain the second photoresist layer after grayscale exposure.

[0151] In the above embodiment, the grayscale exposure parameters are determined by querying the contrast curve. With the contrast curve as a reference, the grayscale values ​​corresponding to each position on the air bridge can be accurately set according to the design shape of the air bridge, and the corresponding exposure intensity can be applied at the corresponding position to achieve a precise grayscale exposure effect and achieve accurate control of the shape of the air bridge.

[0152] Sub-step 423 involves developing the second photoresist layer after grayscale exposure to obtain the processed second photoresist layer.

[0153] In some embodiments, the second photoresist layer after grayscale exposure (the substrate having the second photoresist layer after grayscale exposure) is immersed in a developing solution to obtain the processed second photoresist layer.

[0154] It should be noted that in this sub-step, the parameters for developing the second photoresist layer after grayscale exposure should be consistent with the parameters for developing the experimental second photoresist layer after exposure during the measurement of the contrast curve. For example, if an alkaline developer is used to develop the experimental second photoresist layer after exposure for 50 seconds, an alkaline developer should also be used to develop the second photoresist layer after grayscale exposure for 50 seconds.

[0155] For example, in the case of passing through such Figure 11 After development, the second photoresist layer obtained by the method shown in the diagram after grayscale exposure yields the following result: Figure 12The substrate 56 shown has a processed second photoresist layer.

[0156] In some embodiments, a second region of the first surface of the treated second photoresist layer is flush with the second surface of the pier structure (i.e., they are on the same plane). The first surface of the treated second photoresist layer also does not contact the substrate.

[0157] The second area is used to set up the planar structure in the air bridge.

[0158] In some embodiments, exposure is performed on a first sub-region within the first region using a first exposure intensity, such that the second region of the processed second photoresist layer's first surface is flush with the second surface of the pier structure. The first exposure intensity corresponds to the height of the pier structure (i.e., the distance between the first and second surfaces of the pier structure) in the contrast curve. For example, if the height of the pier structure is 3µm, then the remaining thickness corresponding to the first exposure intensity in the contrast curve is 3µm.

[0159] For example, please refer to Figure 12 The second region 514 of the first surface of the processed second photoresist layer 513 is flush with the second surface 515 of the pier structure.

[0160] In the above embodiment, the second region of the first surface of the processed second photoresist layer is flush with the second surface of the pier structure, that is, the processed second photoresist layer just exposes the top of the pier structure. Therefore, the subsequent air bridge material can be directly laid flat on the second region to connect with the second surface of the pier structure, and finally form a planar structure in the air bridge, while the pier structure can play a supporting role for the planar structure.

[0161] In some embodiments, with the plane containing the first surface of the pier structure as the reference plane, the second region of the first surface of the processed second photoresist layer is lower than the second surface of the pier structure, thereby embedding the pier structure into the ultimately formed air bridge.

[0162] In some embodiments, the processed second photoresist layer has cutouts located on both sides of the second region.

[0163] The hollowed-out sections are used to set up the structure that connects to the base in the air bridge.

[0164] In some embodiments, exposure is performed on two second sub-regions in the first region using a second exposure intensity, such that the processed second photoresist layer has cutouts on both sides of the second region, wherein the second exposure intensity corresponds to the remaining thickness 0 in the contrast curve.

[0165] For example, please refer to Figure 12The processed second photoresist layer 513 has a cutout portion 516, which is located on both sides of the second region 514.

[0166] In the above embodiment, the processed second photoresist layer has a cutout area, thereby directly exposing a portion of the substrate (the second photoresist in this portion is completely removed). This portion will be used to form the structure that connects to the substrate in the air bridge, ensuring that the air bridge can still use this portion of the structure to achieve the bridging.

[0167] Additionally, it should be noted that in some embodiments, since the pier structure is made of metal, it has its own conductor function. Therefore, the air bridge in the embodiments of this application may not have a structure connected to the substrate, that is, the processed second photoresist layer may not have any hollowed-out parts.

[0168] Sub-step 424: Deposit air bridge material on the substrate with the processed second photoresist layer to obtain the substrate after depositing air bridge material.

[0169] In some embodiments, the air bridge material is a superconducting thin film material, which can be the same as the material of the coplanar waveguide in the substrate, such as aluminum, niobium, titanium nitride or tantalum, or other superconducting materials, which are not limited in this application.

[0170] For example, in such Figure 12 The air bridge material is deposited on the substrate 56 with the treated second photoresist layer, as shown, to obtain... Figure 13 The substrate 57 shown is after the air bridge material has been vapor-deposited; the air bridge material is, as can be seen, a thin film. This is because the air bridge material 517 in the second region is connected to the second surface of the N pier structures (…). Figure 13 (Not shown in the image) The air bridge material is tightly connected, so the pier structure plays a crucial supporting role. Therefore, as long as the thickness of the air bridge material is controlled within a reasonable range (such as 400nm or more), a stable air bridge structure can be ensured.

[0171] In some embodiments, such as Figure 12 As shown, prior to sub-step 424, the process further includes: removing the oxide layer on the substrate 56 having the processed second photoresist layer by ion milling.

[0172] For example, a substrate having the treated second photoresist layer is placed in the vacuum chamber of a coating apparatus, and the oxide layer on the substrate having the treated second photoresist layer is removed by ion milling. For example, the coating apparatus described above has an ion milling function, and ion milling is performed on the substrate having the treated second photoresist layer for 3 minutes using argon gas at a flow rate of 7 sccm, under a voltage of 400V and a beam current of 21mA, thereby completely removing the oxide layer on the substrate having the treated second photoresist layer.

[0173] Step 424 includes: depositing an air bridge material on a substrate having a processed second photoresist layer in a vacuum environment to obtain a substrate with the air bridge material deposited.

[0174] For example, after ion milling in the coating equipment, the substrate with the processed second photoresist layer is not exposed to the atmosphere, but the air bridge material continues to be deposited inside the coating equipment. The coating equipment maintains a vacuum environment (i.e., the air bridge material is deposited in situ), which effectively prevents the exposed substrate from being oxidized again.

[0175] In some cases, air bridges need to connect coplanar waveguides within a substrate. However, the substrate may have been exposed to the atmosphere during previous processing, inevitably resulting in the formation of an oxide layer on its surface. While this oxide layer has little impact on the structural stability of the coplanar waveguide, it significantly affects its superconducting properties. Therefore, in the embodiments described above, removing the oxide layer on the substrate by ion milling before depositing the air bridge material ensures good superconductivity in the connection between the air bridge and the substrate (coplanar waveguide).

[0176] Sub-step 425 involves removing the processed second photoresist layer from the substrate after the air bridge material has been vaporized, resulting in a substrate with air bridges.

[0177] In some embodiments, the substrate after the above-described vapor-deposited air bridge material is immersed in a stripper solution to perform a stripping process. Since the air bridge and the pier structure (and the substrate) are connected, the air bridge will not be removed by the stripper solution, while the air bridge material outside the air bridge is attached to the surface of the second photoresist. This part of the air bridge material will be removed as the second photoresist dissolves, thereby obtaining a substrate with air bridges.

[0178] In some embodiments, the adhesive remover is NMP adhesive remover or Remover PG adhesive remover.

[0179] In some embodiments, before performing the above-described stripping process, the adhesive remover is heated in a water bath (e.g., at 80 degrees Celsius for 2 hours) to achieve better adhesive removal. During the stripping process, the adhesive remover can be replaced multiple times to achieve better cleanliness. Finally, the substrate with air bridges is cleaned with isopropyl alcohol and then dried with nitrogen to obtain the final air bridge structure.

[0180] For example, please refer to Figure 13 The processed second photoresist layer 513 is removed from the substrate 57 after the air bridge material is deposited, resulting in the following: Figure 14The base 58 with air bridges is shown. It can be seen that the first surfaces of the N pier structures 31 are connected to the base 50, and the second surfaces of the N pier structures 31 are connected to the air bridges 32, thus the N pier structures 31 provide support for the air bridges 32. It should be noted that... Figure 14 The shape of the air bridge 32 shown does not correspond strictly to the previous drawings; it is used hereby as an example only.

[0181] In the above embodiment, grayscale exposure was used in the process of photolithography of the second photoresist, which not only enables the air bridge to be laid on the pier structure, but also allows for more flexible control over the shape of the air bridge.

[0182] In some embodiments, the span of the air bridge is greater than or equal to 60µm, thereby meeting the requirements for cross-bit connections mentioned in the embodiments above.

[0183] In some embodiments, the air bridge has a structure that connects to the base, and the span of the air bridge refers to the distance between the two points where the air bridge connects to the base in a first direction, where the first direction is the direction in which the air bridge extends.

[0184] In some embodiments, N is greater than 1, and the air bridge is not connected to the base. The span of the air bridge refers to the maximum value of the distance between two pier structures in the first direction among the N pier structures.

[0185] In some embodiments, when N is greater than 1, the N pier structures have the same height. Therefore, the air bridge has a stable planar structure laid on top of the N pier structures, which can extend indefinitely as N increases. For example, when N = 4, there will be 4 pier structures of the same height supporting the planar structure of the air bridge.

[0186] The technical solution provided in this application first forms a columnar pier structure on the substrate, and then prepares an air bridge on the substrate. On the one hand, since the two opposite surfaces of the pier structure connect the substrate and the air bridge respectively, the pier structure can play a supporting role for the air bridge, thereby improving the stability of the air bridge. On the other hand, since the pier structure is formed before the air bridge, during the air bridge preparation process, the pier structure, as a pre-formed structure, can support and maintain the air bridge material used to form the air bridge, thereby ensuring the smooth formation of the air bridge.

[0187] Please refer to Figure 15 The diagram shows a physical schematic of an air bridge structure provided in one embodiment of this application.

[0188] As can be seen, in the air bridge structure provided in this application embodiment, the density of the pier structures 31 used to support the air bridge 32 can be arbitrarily set as needed. In principle, the air bridge 32 structure is most stable when the density of the pier structures 31 is infinitely large. However, the pier structures 31 also occupy space for the underlying wiring. Therefore, it is necessary to obtain a suitable pier structure density so that the pier structures occupy as little bottom space as possible, allowing the bottom layer to accommodate more wiring, while ensuring the stability of the air bridge 32. Figure 16 As shown, in some embodiments, air bridge structures with different densities of pier structures 31 are selected to test the upper limit of the stability of the air bridge. It can be seen that when the spacing of the pier structures 31 in the first direction is close to 500 μm, the air bridge 32 can still exist stably. Therefore, the air bridge 32 can be used for long-distance connection.

[0189] In summary, this application proposes a novel air bridge structure (pier-type long bridge), which in principle allows the span of the air bridge to be infinitely long. This span capability far exceeds that of the arched air bridges widely used in the current chip industry, and the height of the pier-type long bridge can be precisely controlled by controlling the height of the pier structure.

[0190] An exemplary embodiment of this application also provides a chip, the chip including a substrate and an air bridge, the air bridge being prepared using the air bridge preparation method described above.

[0191] Please refer to Figure 17 An exemplary embodiment of this application also provides an air bridge fabrication system 1700, which includes a pier structure fabrication device 1710 and an air bridge fabrication device 1720. For details not described in this air bridge fabrication system embodiment, please refer to the air bridge fabrication method embodiment above.

[0192] The pier structure preparation device 1710 and the air bridge preparation device 1720 may be the same physical device or different physical devices, and this application does not limit them in this regard.

[0193] The pier structure preparation device 1710 is used to form N pier structures on a base. The pier structures are columnar in shape and include a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base, and N is a positive integer.

[0194] The air bridge fabrication apparatus 1720 is used to fabricate an air bridge on a substrate having the N pier structures, wherein the second surfaces of the N pier structures are respectively connected to the air bridge.

[0195] In some embodiments, please refer to Figure 18The pier structure preparation device 1710 includes: a first spin coater 1711, a first exposure machine 1712, a first developing machine 1713, a first coating machine 1714, and a first stripping and cleaning machine 1715.

[0196] The first spin coater 1711 is used to coat the first photoresist on the substrate to form a first photoresist layer.

[0197] The first exposure machine 1712 and the first developing machine 1713 are used to perform exposure and development on the first photoresist layer to remove the first photoresist on N regions of the substrate and obtain the processed first photoresist layer.

[0198] The first coating machine 1714 is used to vapor deposit bridge pier material on a substrate having the first photoresist layer after the treatment, to obtain a substrate after vapor depositing bridge pier material.

[0199] The first stripping and cleaning machine 1715 is used to remove the processed first photoresist layer from the substrate after the evaporation of the bridge pier material to obtain a substrate having the N pier structures.

[0200] In some embodiments, the first photoresist is a negative photoresist.

[0201] The first exposure machine 1712 is used to expose the first photoresist on the regions other than the N regions in the first photoresist layer to obtain the exposed first photoresist layer.

[0202] The first developing machine 1713 is used to develop the exposed first photoresist layer to remove the first photoresist on the N regions and obtain the processed first photoresist layer.

[0203] In some embodiments, the first photoresist is a positive photoresist.

[0204] The first exposure machine 1712 is used to expose the first photoresist on the N regions of the first photoresist layer to obtain the exposed first photoresist layer.

[0205] The first developing machine 1713 is used to develop the exposed first photoresist layer to remove the first photoresist on the N regions and obtain the processed first photoresist layer.

[0206] In some embodiments, the thickness of the pier material in the N regions is less than the thickness of the first photoresist layer.

[0207] In some embodiments, the pier structure fabrication apparatus 1710 further includes: an etching machine ( Figure 18 (Not shown in the image).

[0208] The etching machine is used to etch the substrate to remove the metal layer in N regions of the substrate, thereby obtaining an etched substrate, which is used to form the N pier structures.

[0209] In some embodiments, please refer to Figure 18 The air bridge preparation apparatus 1720 includes: a second spin coater 1721, a second exposure machine 1722, a second developing machine 1723, a second coating machine 1724, and a second stripping and cleaning machine 1725.

[0210] It should be noted that the first spin coater 1711 and the second spin coater 1721 can be the same equipment or different equipment; the first exposure machine 1712 and the second exposure machine 1722 can be the same equipment or different equipment; the first developing machine 1713 and the second developing machine 1723 can be the same equipment or different equipment; the first coating machine 1714 and the second coating machine 1724 can be the same equipment or different equipment; the first peel and clean machine 1715 and the second peel and clean machine 1725 can be the same equipment or different equipment; this application does not impose any limitations.

[0211] The second spin coater 1721 is used to coat a second photoresist on a substrate having the N pile structures to form a second photoresist layer.

[0212] The second exposure machine 1722 is used to perform grayscale exposure on a first area of ​​the first surface of the second photoresist layer to obtain a grayscale exposed second photoresist layer, wherein the first surface of the second photoresist layer is the surface of the second photoresist layer that does not contact the substrate.

[0213] The second developing machine 1723 is used to develop the second photoresist layer after grayscale exposure to obtain the processed second photoresist layer.

[0214] The second coating machine 1724 is used to vapor-deposit air bridge material on a substrate having the treated second photoresist layer to obtain a substrate after vapor-depositing air bridge material.

[0215] The second stripping and cleaning machine 1725 is used to remove the treated second photoresist layer from the substrate after the vapor deposition of the air bridge material to obtain a substrate with the air bridge.

[0216] In some embodiments, the second exposure machine 1722 is used to perform grayscale exposure on the first region according to the exposure intensity corresponding to each position in the first region, to obtain the second photoresist layer after grayscale exposure.

[0217] The exposure intensity corresponding to each position in the first region is obtained from the contrast curve of the second photoresist layer based on the design parameters of the air bridge. The contrast curve is used to reflect the relationship between the exposure intensity of the first surface of the second photoresist layer and the remaining thickness of the second photoresist layer after exposure and development.

[0218] In some embodiments, a second region of the first surface of the processed second photoresist layer is flush with the second surface of the pier structure.

[0219] In some embodiments, the processed second photoresist layer has cutouts, which are located on both sides of the second region.

[0220] In some embodiments, the second coating machine 1724 is further configured to remove the oxide layer on the substrate having the treated second photoresist layer by ion milling; and to vapor-deposit the air bridge material on the substrate having the treated second photoresist layer in a vacuum environment to obtain the substrate after vapor-depositing the air bridge material.

[0221] In some embodiments, the second photoresist is a positive photoresist.

[0222] In some embodiments, the span of the air bridge is greater than or equal to 60 μm.

[0223] In some embodiments, when N is greater than 1, the N pier structures have the same height.

[0224] In some embodiments, the system 1700 further includes a computer device ( Figure 17 and Figure 18 (Not shown in the image), the computer device is used to control the various devices in the pier structure preparation device 1710 and the air bridge preparation device 1720.

[0225] It should be understood that "at least two" as mentioned herein refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. Furthermore, the step numbers described herein are merely illustrative of one possible execution order. In some other embodiments, the steps may not be executed in numerical order, such as two steps with different numbers being executed simultaneously, or two steps with different numbers being executed in the reverse order of the illustration. This application does not limit this.

[0226] The above are merely exemplary embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. A method for preparing an air bridge, characterized in that, The method includes: N pier structures are formed on the base. The pier structures are columnar in shape and include a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base, where N is a positive integer. An air bridge is fabricated on a base having the N pier structures, wherein the second surfaces of the N pier structures are respectively connected to the air bridge.

2. The method according to claim 1, characterized in that, The formation of N pier structures on the base includes: A first photoresist is coated on the substrate to form a first photoresist layer; Exposure and development are performed on the first photoresist layer to remove the first photoresist on N regions of the substrate, resulting in a processed first photoresist layer; On a substrate having the first photoresist layer after the treatment, bridge pier material is vapor-deposited to obtain a substrate after vapor-deposited bridge pier material. The processed first photoresist layer is removed from the substrate after the evaporation of the bridge pier material to obtain a substrate with the N pier structures.

3. The method according to claim 2, characterized in that, The first photoresist is a negative photoresist; the process of exposing and developing the first photoresist layer to remove the first photoresist on N regions of the substrate, to obtain a processed first photoresist layer, includes: Exposure is performed on the first photoresist in the regions other than the N regions in the first photoresist layer to obtain the exposed first photoresist layer. The exposed first photoresist layer is developed to remove the first photoresist on the N regions, resulting in the processed first photoresist layer.

4. The method according to claim 2, characterized in that, The first photoresist is a positive photoresist; the process of exposing and developing the first photoresist layer to remove the first photoresist on N regions of the substrate, to obtain a processed first photoresist layer, includes: Exposure is performed on the first photoresist in the N regions of the first photoresist layer to obtain the exposed first photoresist layer; The exposed first photoresist layer is developed to remove the first photoresist on the N regions, resulting in the processed first photoresist layer.

5. The method according to any one of claims 2 to 4, characterized in that, The thickness of the pier material in the N regions is less than the thickness of the first photoresist layer.

6. The method according to any one of claims 2 to 5, characterized in that, The pier material is metal, and before forming N pier structures on the foundation, the process further includes: The substrate is etched to remove the metal layer in N regions of the substrate, resulting in an etched substrate, which is used to form the N pier structures.

7. The method according to any one of claims 1 to 6, characterized in that, The process of fabricating an air bridge on a base having the N pier structures includes: On a substrate having the N pier structures, a second photoresist is applied to form a second photoresist layer. Grayscale exposure is performed on a first region of the first surface of the second photoresist layer to obtain a grayscale exposed second photoresist layer, wherein the first surface of the second photoresist layer is the surface of the second photoresist layer that does not contact the substrate; The second photoresist layer after grayscale exposure is developed to obtain the processed second photoresist layer. An air bridge material is vapor-deposited onto a substrate having the second photoresist layer after the treatment, to obtain a substrate after vapor-deposited air bridge material. The treated second photoresist layer is removed from the substrate after the air bridge material is evaporated to obtain a substrate with the air bridge.

8. The method according to claim 7, characterized in that, The step of performing grayscale exposure on a first region of the first surface of the second photoresist layer to obtain the grayscale-exposed second photoresist layer includes: Obtain the contrast curve of the second photoresist layer, the contrast curve being used to reflect the relationship between the exposure intensity of the first surface of the second photoresist layer and the remaining thickness of the second photoresist layer after exposure and development; Based on the design parameters of the air bridge, the exposure intensity corresponding to each position in the first region is retrieved from the contrast curve; Based on the exposure intensity corresponding to each position in the first region obtained from the query, grayscale exposure is performed on the first region to obtain the second photoresist layer after grayscale exposure.

9. The method according to claim 7 or 8, characterized in that, The second region of the first surface of the processed second photoresist layer is flush with the second surface of the pier structure.

10. The method according to claim 9, characterized in that, The processed second photoresist layer has hollowed-out areas, which are located on both sides of the second region.

11. The method according to any one of claims 7 to 10, characterized in that, Before depositing the air bridge material onto the substrate having the treated second photoresist layer, and obtaining the substrate after depositing the air bridge material, the method further includes: The oxide layer on the substrate having the treated second photoresist layer is removed by ion milling; The process of depositing air bridge material on a substrate having the treated second photoresist layer to obtain a substrate with deposited air bridge material includes: In a vacuum environment, the air bridge material is deposited on a substrate having the treated second photoresist layer to obtain the substrate after the air bridge material is deposited.

12. The method according to any one of claims 7 to 11, characterized in that, The second photoresist is a positive photoresist.

13. The method according to any one of claims 1 to 12, characterized in that, The span of the air bridge is greater than or equal to 60 μm.

14. The method according to any one of claims 1 to 13, characterized in that, When N is greater than 1, the N pier structures have the same height.

15. An air bridge structure formed on a substrate, characterized in that, The air bridge structure includes N pier structures and an air bridge, where N is a positive integer; The pier structure is columnar in shape, and the pier structure includes a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base. The second surfaces of the N pier structures are respectively connected to the air bridge.

16. A chip, characterized in that, The chip includes a substrate and an air bridge, the air bridge being prepared using the method described in any one of claims 1 to 14.

17. An air bridge fabrication system, characterized in that, The air bridge fabrication system includes: a pier structure fabrication device and an air bridge fabrication device; The pier structure preparation device is used to form N pier structures on a base. The pier structure is in the shape of a column. The pier structure includes a first surface and a second surface that are positioned opposite each other. The first surfaces of the N pier structures are respectively connected to the base. N is a positive integer. The air bridge fabrication apparatus is used to fabricate an air bridge on a substrate having the N pier structures, wherein the second surfaces of the N pier structures are respectively connected to the air bridge.

18. The air bridge fabrication system according to claim 17, characterized in that, The pier structure preparation device includes: a first spin coater, a first exposure machine, a first developing machine, a first coating machine, and a first stripping and cleaning machine; The first spin coater is used to coat the first photoresist onto the substrate to form a first photoresist layer; The first exposure machine and the first developing machine are used to perform exposure and development on the first photoresist layer to remove the first photoresist on N regions of the substrate and obtain the processed first photoresist layer. The first coating machine is used to vapor deposit bridge pier material on a substrate having the processed first photoresist layer, to obtain a substrate after vapor depositing bridge pier material; The first stripping and cleaning machine is used to remove the processed first photoresist layer from the substrate after the evaporation of the bridge pier material to obtain a substrate having the N pier structures.

19. The air bridge fabrication system according to claim 17 or 18, characterized in that, The air bridge preparation apparatus includes: a second spin coater, a second exposure machine, a second developing machine, a second coating machine, and a second stripping and cleaning machine; The second spin coater is used to coat a second photoresist onto a substrate having the N pile structures to form a second photoresist layer; The second exposure machine is used to perform grayscale exposure on a first area of ​​the first surface of the second photoresist layer to obtain a grayscale exposed second photoresist layer, wherein the first surface of the second photoresist layer is the surface of the second photoresist layer that does not contact the substrate; The second developing machine is used to develop the second photoresist layer after grayscale exposure to obtain the processed second photoresist layer; The second coating machine is used to vapor-deposit air bridge material on a substrate having the treated second photoresist layer, to obtain a substrate after vapor-depositing air bridge material; The second stripping and cleaning machine is used to remove the treated second photoresist layer from the substrate after the vapor deposition of the air bridge material, to obtain a substrate with the air bridge.

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