Josephson junction manufacturing method and production line equipment

Abstract

A method and a production line equipment for a Josephson junction, which relates to the technical field of micro-nano processing, includes the steps of: forming a photoresist film layer having an undercut structure on a substrate (201), the undercut structure including a first long hole and a second long hole; forming a first long superconducting layer on the substrate with the undercut structure through the first long hole by performing deposition at a first angle with respect to the substrate with respect to the photoresist film layer; and forming a second long superconducting layer on the substrate with the undercut structure through the second long hole by performing deposition at a second angle with respect to the substrate with respect to the photoresist film layer, the first long superconducting layer and the second long superconducting layer cross each other, and the intersections of the first long superconducting layer and the second long superconducting layer are separated from each other by an oxide layer to form a Josephson junction (203). The present solution does not introduce any additional parasitic junctions, thereby improving the coherence of the qubit assembly.

Description

[Technical Field]

[0001] The present application relates to the technical field of micro- and nano-fabrication, and in particular to a manufacturing method and production line equipment for Josephson junctions.

[0002] This application claims priority to a Chinese patent application filed on March 29, 2022, bearing application number 202210324371.X and entitled "Method for manufacturing Josephson junctions and production line equipment," the entire contents of which are incorporated herein by reference. [Background technology]

[0003] The Josephson junction is currently a popular qubit structure, which can be fabricated using pre-designed photoresist structures.

[0004] In the related art, a Josephson junction can be fabricated by using an electron beam exposure method to form a Dolan bridge-type photoresist structure pattern containing undercuts on a double-layer electron beam photoresist on the surface of a substrate, followed by obliquely depositing a superconducting metal film, oxidizing an insulating layer, and then vertically depositing a superconducting metal film, using a double tilt deposition method.

[0005] The above solution of fabricating Josephson junctions then allows for the introduction of extra Josephson junctions (also called parasitic junctions) into the fabricated qubit assembly, thereby affecting the coherence of the qubit assembly. Summary of the Invention [Problem to be solved by the invention]

[0006] The embodiments of the present application provide a Josephson junction manufacturing method and production line equipment, which can improve the coherence of quantum bit assemblies. [Means for solving the problem]

[0007] In one aspect, there is provided a method for manufacturing a Josephson junction, said method being carried out by a production line facility, said method comprising: fabricating a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel; forming a first elongated superconducting layer on the undercut substrate through the first elongated aperture by depositing the photoresist film layer at a first angle onto the substrate; and a step of forming a second elongated superconducting layer on the undercut structure substrate through the second elongated opening by performing deposition at a second angle inclined to the substrate relative to the photoresist film layer, wherein the first elongated superconducting layer and the second elongated superconducting layer intersect with each other and are separated from each other at their intersections by an oxide layer, thereby forming a Josephson junction.

[0008] In a further aspect, there is provided a production line equipment, the production line equipment including a spin coater, a photolithography tool, and a deposition machine; The spin coater and the photolithography device are used to manufacture a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel; the deposition machine is used to deposit the photoresist film layer on the substrate at a first angle, passing through the first elongated opening to form a first elongated superconducting layer on the substrate with the undercut structure; The deposition machine is further used to produce a second long superconducting layer on the undercut structure substrate through the second long opening by performing deposition at a second angle inclined to the photoresist film layer, and the first long superconducting layer and the second long superconducting layer intersect and are separated from each other at the intersection by an oxide layer, thereby forming a Josephson junction. [Effects of the Invention]

[0009] The beneficial effects of the technical solutions provided in the embodiments of the present application at least include:

[0010] By fabricating a photoresist film layer with an undercut structure on a substrate, the undercut structure having two elongated openings that are not parallel, and fabricating two elongated superconducting layers on the substrate within the undercut structure by oblique deposition at two different angles, which intersect each other and are separated from each other by an oxide layer, in the above solution, one Josephson junction is formed only at the intersection of the two elongated superconducting layers, and no other parasitic junctions are introduced, thereby improving the coherence of the quantum bit assembly. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating the effect of manufacturing a Josephson junction according to the present invention; [Figure 2] 1 is a method flowchart of a method for manufacturing a Josephson junction according to an exemplary embodiment of the present application; [Figure 3] 3 is a schematic diagram of an undercut structure according to the embodiment shown in FIG. 2. FIG. [Figure 4] 1 is a flowchart illustrating a manufacturing process of a Josephson junction according to an exemplary embodiment of the present application. [Figure 5] 1 is a method flowchart of a method for manufacturing a Josephson junction according to an exemplary embodiment of the present application; [Figure 6]6 is a process flow chart for fabricating a Josephson junction according to the embodiment shown in FIG. 5. [Figure 7] 6 is a pattern used in electron beam exposure according to the embodiment shown in FIG. 5. [Figure 8] FIG. 6 is a cross-sectional view of the undercut structure according to the embodiment shown in FIG. 5. [Figure 9] FIG. 6 is a schematic diagram of vapor deposition according to the embodiment shown in FIG. 5. [Figure 10] 6 is a schematic diagram of a three-coating process according to the embodiment shown in FIG. 5. FIG. [Figure 11] FIG. 6 is a diagram showing the effect after photoresist lift-off according to the embodiment shown in FIG. 5. [Figure 12] 6 is a schematic diagram of an undercut pattern and three coating processes according to the embodiment shown in FIG. 5. FIG. [Figure 13] FIG. 6 is a diagram showing the effect after photoresist lift-off according to the embodiment shown in FIG. 5. [Figure 14] FIG. 1 is a schematic diagram of an application scenario of the solution provided in an embodiment of the present application; [Figure 15] 1 is a schematic diagram of a production line facility shown in an exemplary embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0012] First, the meanings of some nouns related to this application will be explained.

[0013] Qubit: In quantum information science, a unit of measurement for quantum information.

[0014] Unlike a classical bit, which can only be in one of two states, 0 or 1, a quantum bit can be in both a 0 state and a 1 state at the same time, i.e., a quantum superposition of 0 and 1.

[0015] Josephson junction: A sandwich structure consisting of a superconducting layer, an insulating layer, and another superconducting layer, and is also called a superconducting tunnel junction.

[0016] A Josephson junction generally has a structure in which an extremely thin barrier layer (thickness ≦ the coherence length of a Cooper electron pair) is sandwiched between two superconductors, such as an S (Superconductor)-I (Semiconductor or Insulator)-S (Superconductor) structure, abbreviated as SIS structure. In a Josephson junction, superconducting electrons can tunnel from one superconducting layer to the other superconducting layer through a thin semiconductor or insulator film by the tunneling effect.

[0017] Parasitic junction: Another Josephson junction introduced during the process of fabricating a Josephson junction.

[0018] Shadow evaporation coating: During evaporative coating, the evaporated material is incident on the surface of the substrate (which may also be called the base) at a predetermined angle, while a photoresist pattern is defined in the incident path to create a barrier of a predetermined shape, so that a film layer is selectively deposited in some places on the substrate surface, but not plated in other places.

[0019] Josephson junction patch: The part of a superconducting quantum chip that connects the Josephson junction to an external circuit.

[0020] Josephson junction bandage: The part of a superconducting quantum chip that connects the Josephson junction patch to an external circuit.

[0021] Ion milling: Removal of oxide layers on a material surface by bombarding the surface with a directed ion beam.

[0022] Oblique evaporation: The evaporated material is deposited as a thin film in a direction not parallel to the normal to the substrate.

[0023] Straight evaporation: Depositing a thin film in a direction where the evaporated material is parallel to the normal to the substrate.

[0024] Lift-off: A process in which the photoresist is dissolved in a remover, simultaneously lifting the metal layer in the photoresist off the substrate.

[0025] Decoherence time: The ability of qubits to maintain different quantum states.

[0026] Undercut structure: A pattern structure formed after developing the photoresist, in which the size of the upper opening is smaller than the size of the lower opening.

[0027] In situ: Multiple processes are carried out in a single vacuum chamber or multiple interconnected vacuum chambers, without the sample / product being moved to an ambient environment.

[0028] Quantum computers have attracted widespread attention due to their significantly superior speed in processing certain problems compared to classical computers. Currently, one possible path to realizing quantum computers is the superconducting quantum computer. Superconducting quantum computers rely on superconducting quantum chips to perform logic gate operations. A superconducting quantum chip can be viewed simply as consisting of an external circuit and a Josephson junction, where the Josephson junction is the core element of the superconducting quantum chip.

[0029] The method for fabricating Josephson junctions is shadow evaporation, which involves in-situ ion milling, oblique incidence deposition, oxidation, and normal incidence deposition to form Josephson junctions. Referring to FIG. 1 , a fabrication diagram of a Josephson junction according to the present invention is shown. Here, FIG. 1 illustrates two Josephson junctions 101 connected in parallel, which are connected to an external circuit by a Josephson junction patch 102. As shown in FIG. 1 , after in-situ ion milling, oblique incidence deposition, oxidation, and normal incidence deposition, a parasitic junction 103 can be formed in the qubit assembly, as shown in the dashed box in FIG. 1 .

[0030] As shown in FIG. 1, when fabricating a Josephson junction according to the above solution, a large-area parasitic junction can be introduced into a quantum bit assembly including the Josephson junction, which affects the decoherence of the quantum bit assembly and further affects the performance of the quantum computing device.

[0031] To improve the performance of qubit assemblies whose structures are Josephson junctions, subsequent embodiments of the present application provide novel Josephson junction fabrication solutions that are applicable to the fabrication of superconducting quantum chips, including planar, flip-chip bonding, and multi-layer stacking.

[0032] 2, a method flowchart of a method for manufacturing a Josephson junction according to an exemplary embodiment of the present application is shown. The method may be performed by a production line facility, and as shown in FIG. 2, the method may include the following steps 201 to 203.

[0033] Step 201: fabricating a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel;

[0034] Here, the undercut structure may refer to a photoresist structure in which a cavity is formed under the upper layer of photoresist by exposing two or more layers of photoresist on a substrate to different degrees of light to a pattern designed therein, and one or more openings in the upper layer of photoresist that are smaller than the cavity are also formed therein.

[0035] For example, refer to Figure 3, which shows a schematic diagram of an undercut structure according to an embodiment of the present application. As shown in Figure 3, there are two layers of photoresist 32 on the upper layer of a substrate 31. After photolithography development is performed on different areas of the two layers of photoresist 32, an undercut structure 33 is formed, and the area of ​​the lower half of the undercut structure 33 is larger than the area of ​​the upper half.

[0036] In an embodiment of the present application, a photoresist film layer with an undercut structure is fabricated on a substrate, the undercut structure including two elongated apertures, wherein the two elongated apertures are not parallel, in other words, the two elongated apertures have one end close to each other and the other end distant from each other.

[0037] Step 202: Obliquely depositing a photoresist film layer onto the substrate at a first angle to form a first elongated superconducting layer on the substrate with an undercut structure through the first elongated aperture.

[0038] In the present embodiment, the direction of deposition at the first angle refers to a direction that is inclined with respect to the normal direction of the substrate and faces the substrate. As can be seen in conjunction with the undercut structure shown in Figure 3, when the first angle is appropriate, a portion of the superconducting material deposited at an angle to the normal direction of the substrate can pass through the aperture at the top of the undercut structure and enter onto the substrate within the undercut structure to form a superconducting layer (another portion of the superconducting material that is obliquely incident on the aperture can be shielded by the sidewall of the aperture).

[0039] In the embodiment of the present application, since the first elongated aperture is elongated, the portion of the deposition material incident on the first elongated aperture at the first angle that is not shielded by the photoresist on top of the undercut structure can form a first elongated superconducting layer on the substrate.

[0040] Step 203: Form a second elongated superconducting layer on the substrate with an undercut structure by forming a second elongated superconducting layer through the second elongated opening by obliquely depositing the photoresist film layer at a second angle. The first elongated superconducting layer and the second elongated superconducting layer intersect with each other, and the intersections of the first elongated superconducting layer and the second elongated superconducting layer are separated from each other by an oxide layer, thereby forming a Josephson junction.

[0041] Similar to the first angle, the second angle refers to a direction that is tilted relative to the normal to the substrate and faces the substrate in a different direction. The deposition material incident on the second elongated aperture at the second angle may form a second elongated superconducting layer on the substrate in the portion not shielded by the photoresist above the undercut structure.

[0042] Here, the positions of the first and second long superconducting layers on the substrate are determined by the positions of the openings in the undercut structure, the height and thickness of the upper photoresist, and the deposition angle (i.e., the first and second angles). By designing the positions of the openings in the undercut structure, the height and thickness of the upper photoresist, and the deposition angle, the first and second long superconducting layers can be made to intersect with each other on the substrate, and by isolating the intersecting regions of the two long superconducting layers from each other by an oxide layer, a Josephson junction can be formed.

[0043] In the above solution, the Josephson junction is obtained by crossing two long superconducting layers with each other, so no other parasitic junctions are introduced.

[0044] As described above, in the solution shown in the embodiment of the present application, a photoresist film layer having an undercut structure is fabricated on a substrate, and the undercut structure has two non-parallel elongated apertures. Two elongated superconducting layers are fabricated on the substrate within the undercut structure by oblique deposition at two different angles, the two layers being separated from each other by an oxide layer and intersecting each other. In the solution, one Josephson junction is formed only at the intersection of the two elongated superconducting layers, without introducing any other parasitic junctions, thereby improving the coherence of the quantum bit assembly.

[0045] Referring to Figure 4, a manufacturing flow chart of the Josephson junction shown in one exemplary embodiment of the present application is shown. As shown in Figure 4, the manufacturing flow of the Josephson junction may be as follows.

[0046] S1: Producing a photoresist film layer on a substrate, the photoresist film layer including an undercut structure, the undercut structure including two elongated openings.

[0047] As shown in FIG. 4, the region on the substrate where the undercut structure is located is region 41, and the undercut structure has a cavity at the bottom and a photoresist other than elongated opening 42 and elongated opening 43 at the top, and the rest of the region other than region 41 is filled with photoresist.

[0048] S2: Oblique deposition is sequentially performed on the photoresist film layer at two different angles, and the deposited material passes through the two elongated apertures to form two elongated superconducting layers on the substrate that intersect with each other and are separated by an oxide layer, thereby forming a Josephson junction.

[0049] Due to the oblique deposition, the positions of the elongated superconducting layers formed on the substrate after the superconducting materials deposited at different angles pass through elongated apertures 42 and elongated apertures 43, respectively, are shifted from the projection positions on the substrate of elongated apertures 42 and elongated apertures 43. This allows the two superconducting layers obtained by deposition through non-intersecting elongated apertures 42 and elongated apertures 43 to intersect and form a Josephson junction.

[0050] 4 , taking the example where elongated aperture 42 and elongated aperture 43 are perpendicular to each other but do not intersect, the first angle is an angle at which the deposition material is incident on the substrate at an angle from the right side to the left side of elongated aperture 42, and when deposited at the first angle, the deposition material passes through elongated aperture 42 to form a elongated superconducting layer 44 on the substrate to the left of elongated aperture 42. The second angle is an angle at which the deposition material is incident on the substrate at an angle from below to above the elongated aperture, and when deposited at the second angle, the deposition material passes through elongated aperture 43 to form a elongated superconducting layer 45 on the substrate above elongated aperture 43. Here, the first angle / second angle may be as shown in FIG. 3, and when the elongated aperture 42 and the elongated aperture 43 are sufficiently close, the elongated superconducting layer 44 and the elongated superconducting layer 45 can cross each other, and if the deposited superconducting layer is oxidized between the two oblique depositions, a Josephson junction 46 can be obtained after the second oblique deposition.

[0051] According to the solution shown in FIG. 2, in the embodiment of the present application, not only can a Josephson junction without a parasitic junction be fabricated, but also a Josephson junction patch can be fabricated without introducing a parasitic junction.

[0052] 5, a method flowchart of a method for manufacturing a Josephson junction according to an exemplary embodiment of the present application is shown. The method may be performed by a production line facility, and as shown in FIG. 5, the method may include the following steps 501 to 506.

[0053] Step 501: fabricating a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel, and the undercut structure further including a first connection portion aperture and a second connection portion aperture.

[0054] In one possible implementation, the extension direction of the first elongated aperture and the extension direction of the second elongated aperture are perpendicular.

[0055] Here, the extension direction of the elongated aperture may refer to the direction in which a straight line segment between both ends of the elongated aperture continues to one / both ends.

[0056] Here, to facilitate the circuit design of the quantum bit assembly, the extension direction of the first elongated aperture and the extension direction of the second elongated aperture may be set perpendicular to each other, so that the two subsequently fabricated elongated superconducting layers that intersect to form a Josephson junction are also perpendicular to each other.

[0057] In another possible implementation, the extension direction of the first elongated aperture and the extension direction of the second elongated aperture may form an angle other than 90°, such as 45°, 60°, and 80°.

[0058] In addition to the two elongated apertures, there are also a first connection aperture and a second connection aperture in the undercut structure, where the first connection aperture and the second connection aperture are used to subsequently fabricate a Josephson junction patch, which is respectively connected to two elongated superconducting layers constituting a Josephson junction.

[0059] In one possible implementation, the steps of manufacturing a photoresist film layer including an undercut structure on a substrate include the following steps S501a to S501h.

[0060] S501a: A first photoresist is spin-coated onto a substrate to a first thickness.

[0061] S501b: The first photoresist is subjected to a hardening process.

[0062] S501c: A second photoresist having a second thickness is spin-coated on top of the first photoresist.

[0063] S501d: The second photoresist is subjected to a hardening process.

[0064] In an embodiment of the present application, a first layer of photoresist may be spin-coated on a substrate, and the first photoresist may be hardened by a curing process, such as a baking process, and then a second layer of photoresist may be spin-coated on top of the first photoresist and further hardened by a curing process, thereby forming two layers of photoresist on a substrate.

[0065] Here, the first photoresist and the second photoresist are photoresists made of different materials.

[0066] In the present embodiment, the first photoresist is located below the second photoresist, and an undercut structure needs to be formed, so the first photoresist needs to be exposed while the second photoresist is being held in place. Therefore, in the present embodiment, the first photoresist can more easily meet the exposure conditions than the second photoresist.

[0067] S501e: The second photoresist in the areas of the first elongated aperture and the second elongated aperture is exposed to electron beam.

[0068] S501f: Electron beam exposure is performed on the first photoresist and the second photoresist in the regions of the first connection portion opening and the second connection portion opening.

[0069] S501g: The first photoresist in the area other than the first connection portion opening in the undercut structure area and the second connection portion opening is exposed to electron beams.

[0070] In an embodiment of the present application, for an undercut structure including an elongated aperture and a connecting aperture to be manufactured, the photolithography apparatus may use different degrees of exposure processing for the elongated aperture, the connecting aperture, and other parts of the undercut structure (i.e., the cavity part with the upper shielded portion), respectively, so that the three different positions have different exposure effects.

[0071] For example, in one possible implementation, the photolithography apparatus may first expose a first photoresist. The exposed area includes areas other than the connection portion openings in the undercut structure. Then, the photolithography apparatus further exposes a second photoresist. The exposed area includes an area corresponding to the elongated opening. After the two exposures, the area of ​​the connection portion openings remains unexposed. At this time, the photolithography apparatus can simultaneously expose the first photoresist and the second photoresist in the area of ​​the connection portion openings.

[0072] Furthermore, for example, the above-mentioned multiple exposure steps may be performed simultaneously by a photolithography apparatus. In other words, the photolithography apparatus may simultaneously perform exposure on the first photoresist in areas other than the connection hole in the undercut structure, the second photoresist in areas corresponding to the elongated opening, and the first photoresist and second photoresist in the area of ​​the connection hole.

[0073] S501h: The first photoresist and the second photoresist after the electron beam exposure are developed to obtain a photoresist film layer including an undercut structure.

[0074] After the exposure step S501g, an operator or operating equipment (e.g., the production line equipment) can perform a development process on the photoresist on the base to remove the exposed photoresist and leave a photoresist film layer including the undercut structure.

[0075] In one possible implementation, the step of developing the first photoresist and the second photoresist after the electron beam exposure to obtain a photoresist film layer including an undercut structure includes: a step of developing the exposed first photoresist and the second photoresist in a developer; and cleaning the remaining photolithographically developed photoresist on the substrate with oxygen plasma to obtain a photoresist film layer including an undercut structure.

[0076] In the embodiment of the present application, when the exposed photoresist is subjected to a development process, the exposed first and second photoresists may be first placed in a developer and developed for a certain period of time to remove most of the exposed photoresist, and the remaining developed photoresist may be further cleaned with oxygen plasma.

[0077] Step 502: Depositing a photoresist film layer at a first angle inclined to the substrate to form a first elongated superconducting layer through the first elongated aperture on the substrate with an undercut structure.

[0078] In the embodiment of the present application, the undercut structure further includes a second elongated aperture, so that during the deposition of the photoresist film layer at a first angle inclined relative to the substrate, a third elongated superconducting layer is produced on the substrate with the undercut structure by passing through the second elongated aperture.

[0079] Since the first elongated aperture and the second elongated aperture do not intersect, for tilted deposition at the same angle, the two elongated superconducting layers fabricated on the undercut structure substrate through the two elongated apertures also do not intersect.

[0080] Step 503: The first long superconducting layer is subjected to an oxidation treatment to form an oxide layer on the surface of the first long superconducting layer.

[0081] In the embodiment of the present application, since the Josephson junction to be manufactured is composed of two portions of superconducting material and an insulating layer between the two portions of superconducting material, before manufacturing the second elongated superconducting layer, an oxide layer may first be manufactured on the surface of the first elongated superconducting layer to serve as an insulating layer in the Josephson junction.

[0082] Step 504: Obliquely depositing the photoresist film layer onto the substrate at a second angle to fabricate a second elongated superconducting layer through the second elongated aperture on the substrate with the undercut structure.

[0083] Here, the first long-shaped superconducting layer and the second long-shaped superconducting layer intersect with each other, and the intersection of the first long-shaped superconducting layer and the second long-shaped superconducting layer is separated from each other by an oxide layer, thereby forming a Josephson junction.

[0084] Similarly, during the process of depositing the photoresist film layer at a second angle inclined to the substrate, a fourth elongated superconducting layer is formed on the substrate with the undercut structure through the first elongated opening.

[0085] In the present embodiment, the third elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer, and correspondingly, the fourth elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

[0086] In other words, in the present embodiment, by performing oblique deposition at two angles, respectively, with respect to the two elongated apertures in the undercut structure, four elongated superconducting layers can be formed on the substrate, including first and second elongated superconducting layers that intersect with each other, a third elongated superconducting layer that is independent, and a fourth elongated superconducting layer that is independent, where the first and second elongated superconducting layers that intersect with each other are used to form Josephson junctions, while the third and fourth elongated superconducting layers are not connected to the quantum bit assembly to be fabricated.

[0087] Step 505: Ion milling cleaning is performed on the first long superconducting layer and the second long superconducting layer.

[0088] In an embodiment of the present application, the production line equipment may perform ion milling cleaning on the overlapping area between the first elongated superconducting layer and the projection of the first connection portion opening on the substrate, and on the overlapping area between the second elongated superconducting layer and the projection of the second connection portion opening on the substrate.

[0089] In the embodiment of the present application, a Josephson junction patch to be fabricated subsequently must form a superconducting connection with the Josephson junction. Meanwhile, in the process of fabricating a Josephson junction, an oxidation step is performed, i.e., an oxide layer may be present on the surface of the first long superconducting layer. Therefore, in the embodiment of the present application, before fabricating the Josephson junction patch, the fabricated first long superconducting layer and the second long superconducting layer are first subjected to ion milling cleaning to remove the oxide layer on the surface of the first long superconducting layer.

[0090] In addition, when the third long-shaped superconducting layer and the fourth long-shaped superconducting layer additionally obtained in the manufacturing process of the above superconducting layer are subjected to oxidation treatment in step 503, oxide layers can also be produced on the surfaces of the third long-shaped superconducting layer and the fourth long-shaped superconducting layer.

[0091] In this step, the direction of ion milling cleaning may be perpendicular to the substrate, and accordingly, the cleaned areas include areas not shielded by photoresist in the vertical direction, i.e., the area where the first elongated superconducting layer and the vertical projection of the first connection hole on the substrate overlap (i.e., the area where the vertical projection of the first connection hole on the substrate and the first elongated superconducting layer on the substrate overlap each other), the area where the second elongated superconducting layer and the vertical projection of the second connection hole on the substrate overlap (i.e., the area where the vertical projection of the second connection hole on the substrate and the second elongated superconducting layer on the substrate overlap each other), the area of ​​the vertical projection of the third elongated superconducting layer on the substrate, and the area of ​​the vertical projection of the fourth elongated superconducting layer on the substrate.

[0092] Step 506: By depositing a photoresist film layer perpendicular to the substrate, a first connection portion superconducting layer and a second connection portion superconducting layer are fabricated on the substrate with an undercut structure through the first connection portion opening and the second connection portion opening, and the first connection portion superconducting layer and the first long-shaped superconducting layer form a superconducting connection, and the second connection portion superconducting layer and the second long-shaped superconducting layer form a superconducting connection.

[0093] In an embodiment of the present application, the position of the vertical projection of the first connection portion aperture on the substrate intersects with the first elongated superconducting layer, and the position of the vertical projection of the second connection portion aperture on the substrate also intersects with the second elongated superconducting layer, which can be achieved by designing the first angle and the second angle. Under such design, when the photoresist film layer is deposited perpendicular to the substrate, the deposited superconducting material can produce, on the undercut structure substrate, a first connection portion superconducting layer that forms a superconducting connection with the first elongated superconducting layer and a second connection portion superconducting layer that forms a superconducting connection with the second elongated superconducting layer.

[0094] In the present example, since the superconducting layer on the substrate has already been cleaned by ion milling before vertical deposition, no new Josephson junctions are formed on the substrate after vertical deposition, i.e., no parasitic junctions are introduced.

[0095] In one possible implementation, the environment in which the steps (i.e., steps 502 to 506) described above are performed from the step of depositing the photoresist film layer at a first angle inclined relative to the substrate (also called oblique deposition) to the step of depositing the photoresist film layer perpendicular to the substrate (also called normal deposition) is an in-situ environment.

[0096] Referring to Figure 6, a process flow chart of the fabrication of a Josephson junction according to an embodiment of the present application is shown. As shown in Figure 6, the solution shown in the embodiment of the present application fabricates a Josephson junction by designing a shadow evaporation coating method. As shown in Figure 6, taking the example of two elongated holes perpendicular to each other, the specific flow may be as follows:

[0097] S61: Spin-coat one layer of e-beam photoresist MAA with a thickness of t_M onto a silicon or sapphire substrate.

[0098] S62: The photoresist is hardened by soft baking at 180°C for 7 minutes.

[0099] S63: Based on this, one layer of electron beam photoresist PMMA with thickness t_P is further spin-coated.

[0100] S64: The photoresist is hardened by soft baking at 180°C for 2 minutes, thus forming a two-layer resist structure.

[0101] S65: Electron beam exposure is performed.

[0102] Here, the electron beam exposure dose may be as follows:

[0103] The exposure dose of the PMMA photoresist in the area of ​​the elongated opening is 450 μC / cm^2, the exposure dose of the MAA photoresist in the area of ​​the undercut structure other than the connection opening is 150 μC / cm^2, and the exposure dose of the PMMA+MAA photoresist in the area of ​​the connection opening is 800 μC / cm^2.

[0104] The electron beam exposure process can expose the PMMA+MAA photoresist in the regions of the elongated opening and the connection opening, and the MAA in other regions in the undercut structure.

[0105] The film is developed for 1 minute using a developer of S66:MIBK:IPA=1:3, and then fixed for 0.5 minutes using IPA, thus forming an undercut structure.

[0106] S67: After development, a small amount of residual resist in the pattern area after development is removed by cleaning for 2 minutes using oxygen plasma with a power of 200 W.

[0107] The sample with the patterned structure is then placed in a vacuum chamber that integrates the functions of ion milling, oxidation, and multi-angle coating, and evacuated.

[0108] S68: Under the condition that the rotation angle is 0° and the tilt angle is θ, 60 nm of superconducting metal is evaporated.

[0109] S69: After restoring the tilt angle to 0°, the oxidation time is adjusted according to the desired magnitude of the junction resistance.

[0110] S610: After the oxidation is completed, 60 nm of superconducting metal is evaporated under the condition that the rotation angle is 90° and the tilt angle is θ, thus forming a sandwich structure of metal / oxide layer / metal, i.e., a Josephson junction.

[0111] S611: After forming the bonding area, ion milling cleaning is performed for 3 minutes.

[0112] For example, the ion milling process may be performed by setting the included angle between the ion incident direction and the substrate normal to 30° and setting the substrate rotation speed to 10 rpm. The purpose of ion milling is to remove the oxide layer on the surface of the external circuit.

[0113] S612: Finally, under the condition that the tilt angle is 0° and the rotation angle is an arbitrary angle, 100 nm of superconducting metal is evaporated normally to form a Josephson junction bandage / patch, and the Josephson junction is connected to an external circuit.

[0114] S613: The photoresist is lifted off to obtain Josephson junctions and Josephson junction patches.

[0115] According to the solution shown in FIG. 6, in one possible implementation, the first connection portion aperture is not connected to the first elongated aperture, and the second connection portion aperture is not connected to the second elongated aperture; a projection of the deposition direction at the first angle onto the substrate is perpendicular to the extension direction of the first elongated aperture; The projection of the direction of deposition at the second angle onto the substrate is perpendicular to the extension direction of the second elongated aperture.

[0116] Here, the first elongated superconducting layer and the projection of the first elongated aperture on the substrate do not intersect.

[0117] Furthermore, the second elongated superconducting layer and the projection of the second elongated aperture on the substrate do not intersect.

[0118] Referring to Figure 7, the pattern used for electron beam exposure in an embodiment of the present application is shown. As shown in Figure 7, region 71 represents the area where the electron beam photoresist of the MAA layer disappears after development, region 72 represents the area where the electron beam photoresist of the PMMA layer disappears after development, and region 73 represents the area where the electron beam photoresist of the PMMA + MAA layer both disappears after development. The remaining blank area represents the area where both PMMA and MAA remain after development.

[0119] Based on the above-mentioned Fig. 7, a cross-sectional view of an undercut structure according to an embodiment of the present application is shown in Fig. 8. As shown in Fig. 8, the cross-section is taken along cutting line 74 in Fig. 7.

[0120] Here, region 81 represents the e-beam photoresist of the MAA layer retained after development, region 82 represents the e-beam photoresist of the PMMA layer retained after development, and region 83 represents the substrate. After e-beam exposure and development, the patterns in the PMMA and MAA layers result in an undercut structure, i.e., the area surrounded by the substrate and photoresist in Figure 8.

[0121] In this embodiment, oxygen plasma is used to clean away any remaining electron beam photoresist in the exposed areas of the surface of base 83, and the structure is then placed in a vacuum-integrated ion milling, oxidation, and multi-angle coating facility. In the first step, the structure is coated with a rotation angle of 0° and a tilt angle of θ. A rotation angle of 0° refers to a deposition angle perpendicular to the extension direction of one elongated aperture. In other words, when two elongated apertures are perpendicular, a rotation angle of 90° means that the deposition angle is perpendicular to the extension direction of the other elongated aperture.

[0122] Referring to FIG. 9 in conjunction with FIG. 8, a schematic diagram of deposition according to an embodiment of the present application is shown. As shown in FIG. 9, based on FIG. 8, an evaporation source 91 with a rotatable angle is added. Assuming that the width of MAA pattern definition layer 81 is d_M and the width of PMMA pattern definition layer 82 is d_P, in order to manufacture a Josephson junction that satisfies the conditions, d_M > (t_P + t_M) tan θ > d_P > t_P tan θ must be simultaneously satisfied.

[0123] The width of the Josephson junction 92 defined by this is d_P-t_P·tan θ, where the width of the Josephson junction can be adjusted and controlled by adjusting the θ angle based on satisfying the above relationship.

[0124] After oxidation, the substrate can be rotated by 90° and the θ angle can be adjusted to control the length of the Josephson junction. At the same time, to ensure that no Josephson junction bandage / patch is formed during the above process, the condition (t_P+t_M) tan θ>d_(P+M) must be satisfied, where d_(P+M) is the width of the PMMA+MAA pattern-defining layer 73.

[0125] Referring to Figure 7, after forming the junction area of ​​the Josephson junction, ion milling is used to remove the oxide layer exposed in the 73 region of the external circuit, and then the tilt angle is set to 0° and the rotation angle is set to an arbitrary angle to deposit superconducting material to form the Josephson junction bandage / patch.

[0126] 10, in conjunction with FIG. 7, shows a schematic diagram of the three-time coating process according to an embodiment of the present application. As shown in part (a) of FIG. 10, the vertical deposition symbol 1001 indicates that the superconducting film layer is deposited in a direction perpendicular to the paper surface.

[0127] Corresponding to the three coating processes in Figure 10, the obtained effect is as shown in part (b) of Figure 10, where region 1002 represents the circuit formed after the first coating, region 1003 represents the circuit formed by the second coating, region 1004 represents the Josephson junction formed, and region 1005 represents the Josephson junction bandage / patch formed by the third coating.

[0128] 11 in conjunction with FIG. 10, there is shown an effect diagram after photoresist lift-off according to an embodiment of the present application, where the portion enclosed by the dashed box 1101 is the fabricated Josephson junction.

[0129] In one possible implementation, the first connection aperture is connected to one end of the first elongated aperture, and the second connection aperture is connected to one end of the second elongated aperture; a projection of the deposition direction at the first angle onto the substrate is parallel to a direction extending in the first elongated aperture from the first connection portion aperture to the other end of the first elongated aperture; The projection of the deposition direction at the second angle onto the substrate is parallel to the direction extending in the second elongated aperture from the second connection portion aperture to the other end of the second elongated aperture.

[0130] Here, the projection of the deposition direction at the first angle onto the substrate being parallel to the direction extending from the first connection portion opening to the other end of the first elongated opening in the first elongated opening means that the direction obtained from the projection of the deposition direction at the first angle onto the substrate is parallel to the direction extending from the first connection portion opening to the other end of the first elongated opening in the first elongated opening, and also means that the direction obtained from the projection of the deposition direction at the first angle onto the substrate is the same as the direction extending from the first connection portion opening to the other end of the first elongated opening in the first elongated opening.

[0131] Similarly, the projection of the deposition direction at the second angle onto the substrate being parallel to the direction extending from the second connection portion opening to the other end of the second elongated opening in the second elongated opening means that the direction obtained from the projection of the deposition direction at the second angle onto the substrate is parallel to the direction extending from the second connection portion opening to the other end of the second elongated opening in the second elongated opening, and also means that the direction obtained from the projection of the deposition direction at the second angle onto the substrate is the same as the direction extending from the second connection portion opening to the other end of the second elongated opening in the second elongated opening.

[0132] The solution shown in the embodiments of the present application uses shadow deposition to define the junction area of ​​the Josephson junction under a hollow photoresist structure, thereby preventing damage to the Josephson junction due to ion bombardment. Therefore, in addition to the solutions shown in Figures 7 to 10, other similar solutions may be used, such as fabricating the Josephson junction under the upper photoresist in an undercut structure using oblique deposition. A possible alternative solution is provided below.

[0133] Referring to Figure 12, a schematic diagram of the undercut pattern and three coating processes according to an embodiment of the present application is shown. As shown in Figure 12, still taking the cross section shown in Figure 8 as an example, the requirements for the deposition angle and opening size are t_P·tanθ>d_P and (t_P+t_M)tanθ>d_(P+M).

[0134] As shown in Figure 12, the first deposition is performed with a rotation angle of 90° and a tilt angle θ of any value that satisfies the above requirements. The second deposition is performed with a rotation angle of 0° and a tilt angle θ of any value that satisfies the above requirements. The Josephson junction is then formed by the first two depositions. Ion milling is then performed to remove the oxide layer from the contact area with the external circuit. The third deposition is performed with a rotation angle of any value and a tilt angle of 0° to form the Josephson junction patch / bandage.

[0135] Referring to FIG. 13 in conjunction with FIG. 12, an effect diagram after photoresist lift-off according to an embodiment of the present application is shown.

[0136] The solutions shown in the above embodiments of the present application can achieve the following effects.

[0137] 1) Eliminate the parasitic junctions introduced during the manufacturing process of Josephson junctions.

[0138] 2) Eliminate damage to the substrate surface caused by ion milling and improve contact between the superconducting film layer and the substrate interface.

[0139] 3) The function of Josephson junction bandage and Josephson junction patch is combined to complete the fabrication of Josephson junction and Josephson junction bandage / patch in situ, simplifying the process flow.

[0140] 4) Protecting the Josephson junction, avoiding ion bombardment and reducing the risk of destruction of the Josephson junction.

[0141] 5) The size of the Josephson junction can be adjusted by selecting the coating angle.

[0142] 6) This solution is also applicable to fabricating nanoscale Josephson junctions using ultraviolet photoresist structures with a minimum resolution of about 1 um, such as ultraviolet exposure or laser direct writing.

[0143] As described above, in the solution shown in the embodiment of the present application, a photoresist film layer with an undercut structure having two non-parallel elongated openings is fabricated on a substrate, and two elongated superconducting layers that intersect each other and are separated from each other by an oxide layer are fabricated on the substrate within the undercut structure by oblique deposition at two different angles. In the solution, one Josephson junction is formed only at the intersection of the two elongated superconducting layers, without introducing any other parasitic junctions, thereby improving the coherence of the quantum bit assembly.

[0144] 14 shows a schematic diagram of an application scenario of the solution provided in one embodiment of the present application. As shown in FIG. 14, the application scenario may be a superconducting quantum computing platform, which may include a quantum computing device 141, a dilution refrigerator 142, a control device 143, and a computer 144.

[0145] The quantum computing device 141 is a circuit that operates on a physical quantum bit, and the quantum computing device 141 can be realized as a quantum chip, for example, a superconducting quantum chip that is near absolute zero. The dilution refrigerator 142 is used to provide an absolute zero environment for the superconducting quantum chip. Here, the physical quantum bit can be a Josephson junction fabricated by the method shown in the above embodiment of the present application.

[0146] Control facility 143 is used to control quantum computing device 141, and computer 144 is used to control control facility 143. For example, a programmed quantum program is compiled as instructions in software in computer 144 and sent to control facility 143 (e.g., an electronic / microwave control system), and control facility 143 converts the instructions into electronic / microwave control signals that are input to dilution refrigerator 142 to control superconducting qubits at a temperature below 10 mK. The readout process is the opposite, and the readout waveform is transmitted to quantum computing device 141.

[0147] FIG. 15 shows a schematic diagram of a production line equipment shown in an exemplary embodiment of the present application. As shown in FIG. 15, the production line equipment includes a spin coater 1501, a photolithography device 1502, and a deposition machine 1503. The spin coater 1501 and the photolithography device 1502 are used to manufacture a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel, the deposition machine 1503 is used to deposit the photoresist film layer on the substrate at a first angle in a tilted manner, so as to pass through the first elongated opening and form a first elongated superconducting layer on the substrate with the undercut structure; The deposition machine 1503 is further used to produce a second long superconducting layer on the undercut structure substrate through the second long opening by performing deposition at a second angle inclined to the substrate relative to the photoresist film layer, and the first long superconducting layer and the second long superconducting layer intersect and are separated from each other at the intersection by an oxide layer, thereby forming a Josephson junction.

[0148] In one possible embodiment, in the process of depositing the photoresist film layer on the substrate at a first angle, the deposition machine 1503 is further used to form a third long superconducting layer on the undercut structure substrate through the second long opening; The third elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

[0149] In one possible embodiment, in the process of depositing the photoresist film layer on the substrate at a second angle, the deposition machine 1503 is further used to form a fourth long superconducting layer on the undercut structure substrate through the first long opening; The fourth elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

[0150] In one possible implementation, the deposition machine 1503 is further used to perform an oxidation treatment on the first long superconducting layer before depositing the photoresist film layer on the substrate at a second angle, thereby producing an oxide layer on the surface of the first long superconducting layer.

[0151] In one possible implementation, the first elongated superconducting layer and the projection of the first elongated aperture on the substrate do not intersect, the second elongated superconducting layer and the projection of the second elongated aperture on the substrate do not intersect, and the undercut structure further includes a first connection portion aperture and a second connection portion aperture; The deposition machine 1503 is further used to deposit the photoresist film layer perpendicular to the substrate, passing through the first connection hole and the second connection hole to produce a first connection portion superconducting layer and a second connection portion superconducting layer on the undercut structure substrate, and the first connection portion superconducting layer and the first long-shaped superconducting layer form a superconducting connection, and the second connection portion superconducting layer and the second long-shaped superconducting layer form a superconducting connection.

[0152] In one possible embodiment, the extension direction of the first elongated aperture and the extension direction of the second elongated aperture are perpendicular to each other.

[0153] In one possible implementation, the first connection portion aperture is not connected to the first elongated aperture, and the second connection portion aperture is not connected to the second elongated aperture; a projection of the deposition direction at the first angle onto the substrate is perpendicular to an extension direction of the first elongated aperture; The projection of the second angled deposition direction onto the substrate is perpendicular to the extension direction of the second elongated aperture.

[0154] In one possible implementation, the first connection aperture is connected to one end of the first elongated aperture, and the second connection aperture is connected to one end of the second elongated aperture; a projection of the deposition direction at the first angle on the substrate is parallel to a direction extending in the first elongated aperture from the first connection portion aperture to the other end of the first elongated aperture; The projection of the second angled deposition direction onto the substrate is parallel to a direction extending in the second elongated aperture from the second connection portion aperture to the other end of the second elongated aperture.

[0155] As shown in FIG. 15, in one possible implementation, the production line equipment further includes an etching machine 1504; The etching machine 1504 is used to perform ion milling cleaning on the overlapping area between the first elongated superconducting layer and the projection of the first connection hole on the substrate, and the overlapping area between the second elongated superconducting layer and the projection of the second connection hole on the substrate before the deposition machine performs deposition on the photoresist film layer perpendicular to the substrate.

[0156] In one possible implementation, the production line equipment further includes a hot plate 1505; The spin coater 1501 is used to spin coat a first photoresist having a first thickness onto the substrate; The hot plate 1505 is used to perform a hardening process on the first photoresist. The spin coater 1501 is used to spin coat a second photoresist having a second thickness on the first photoresist; The hot plate 1505 is used to perform a hardening process on the second photoresist. The photolithography apparatus 1502 is used to perform electron beam exposure on the second photoresist in the areas of the first elongated opening and the second elongated opening, perform electron beam exposure on the first photoresist and the second photoresist in the areas of the first connection portion opening and the second connection portion opening, and perform electron beam exposure on the first photoresist in the area of ​​the undercut structure other than the first connection portion opening and the second connection portion opening, and the photoresist film layer including the undercut structure is obtained by developing the first photoresist and the second photoresist after electron beam exposure.

[0157] In one possible implementation, the photoresist film layer including the undercut structure is obtained by developing the exposed first photoresist and the second photoresist in a developer, and then cleaning the photoresist remaining on the substrate after photolithography development with oxygen plasma.

[0158] Optionally, the production line equipment may further include a processor that is electrically connected to the spin coater 1501, the photolithography device 1502, the deposition device 1503, the etching device 1504, and the hot plate 1505, respectively, and may be used to control the spin coater 1501, the photolithography device 1502, the deposition device 1503, the etching device 1504, and the hot plate 1505, etc.

[0159] Optionally, the production line equipment further includes a power supply, which is used to provide power to electrical equipment such as the processor, spin coater 1501, photolithography equipment 1502, deposition machine 1503, etching machine 1504, and hot plate 1505.

[0160] Optionally, each machine is spatially connected by a conveyor, or a robot arm is used to complete the movement of the products between each machine.

[0161] Optionally, the production line equipment may further include a memory, which may be adapted to store at least one computer instruction, and the processor executes the at least one computer instruction to cause the production line equipment to perform the method for manufacturing the Josephson junction.

[0162] In one exemplary embodiment, a computer-readable storage medium is further provided, having stored thereon at least one computer instruction that, when executed by a processor in production line equipment, causes the production line equipment to perform the method for manufacturing the Josephson junction.

[0163] In an exemplary embodiment, there is further provided a computer program product or a computer program including computer instructions stored on a computer-readable storage medium, the computer instructions being read by a processor of a production line equipment from the computer-readable storage medium, and the processor executing the computer instructions to cause the production line equipment to perform the method for manufacturing Josephson junctions. [Explanation of symbols]

[0164] 42 Open hole 43 Open hole 44 Superconducting layer 45 Superconducting layer 46 Josephson junction 73 MAA Pattern Definition Layer 74 Cutting line 81 MAA Pattern Definition Layer 82 PMMA pattern definition layers 83 Base 91 Evaporation Source 92 Josephson junction 101 Josephson junction 102 Josephson junction patch 103 Parasitic Junction 141 Quantum Computing Devices 142 Dilution Refrigerator 144 Computers 1501 Spin Coater 1502 Photolithography equipment 1503 Vapor deposition machine 1504 Etching machine 1505 Hot Plate

Claims

1. 1. A method of manufacturing a Josephson junction, performed by production line equipment, said method comprising: fabricating a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel; forming a first elongated superconducting layer on the undercut substrate through the first elongated aperture by depositing a first angle on the substrate relative to the photoresist film layer, the first angle projected onto the substrate being perpendicular to the longitudinal direction of the first elongated aperture; and forming a second elongated superconducting layer on the undercut substrate through the second elongated aperture by performing deposition at a second angle inclined to the substrate with respect to the photoresist film layer, wherein the projection of the second angle onto the substrate is perpendicular to the longitudinal direction of the second elongated aperture, the first elongated superconducting layer and the second elongated superconducting layer intersect with each other, and an oxide layer separates the first elongated superconducting layer and the second elongated superconducting layer from each other at their intersections, thereby forming a Josephson junction.

2. a third elongated superconducting layer is formed on the undercut substrate through the second elongated opening during deposition of the photoresist film layer at a first angle on the substrate; 2. The method of claim 1, wherein the third elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

3. a step of depositing a fourth elongated superconducting layer on the substrate with the undercut structure through the first elongated opening during a deposition process inclined at a second angle relative to the photoresist film layer; 2. The method of claim 1, wherein the fourth elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

4. before the step of obliquely depositing onto the substrate at a second angle relative to the photoresist film layer; 2. The method of claim 1, further comprising the step of performing an oxidation treatment on the first elongated superconducting layer to form an oxide layer on a surface of the first elongated superconducting layer.

5. the first elongated superconducting layer and a projection of the first elongated aperture on the substrate do not intersect, the second elongated superconducting layer and a projection of the second elongated aperture on the substrate do not intersect, the undercut structure further includes a first connection portion aperture and a second connection portion aperture, and the method further comprises:

2. The method of claim 1, further comprising the step of: depositing the photoresist film layer perpendicular to the substrate, passing through the first connection opening and the second connection opening, to fabricate a first connection portion superconducting layer and a second connection portion superconducting layer on the undercut structured substrate, wherein the first connection portion superconducting layer and the first elongated superconducting layer form a superconducting connection, and the second connection portion superconducting layer and the second elongated superconducting layer form a superconducting connection.

6. before the step of depositing the photoresist film layer perpendicular to the substrate, 6. The method of claim 5, further comprising the step of performing ion milling cleaning on an overlapping region between the first elongated superconducting layer and a projection of the first connection portion opening on the substrate, and an overlapping region between the second elongated superconducting layer and a projection of the second connection portion opening on the substrate.

7. 7. The method according to claim 5, wherein the steps between the step of depositing the photoresist film layer at a first angle to the substrate and the step of depositing the photoresist film layer perpendicular to the substrate are performed in an in situ environment.

8. 6. The method of claim 5, wherein the extension direction of the first elongated aperture and the extension direction of the second elongated aperture are perpendicular.

9. 6. The method of claim 5, wherein the first connector aperture is not connected to the first elongated aperture and the second connector aperture is not connected to the second elongated aperture.

10. The step of fabricating a photoresist film layer including an undercut structure on a substrate includes: spin-coating a first photoresist to a first thickness onto the substrate; performing a hardening process on the first photoresist; spin-coating a second photoresist of a second thickness on top of the first photoresist; performing a hardening process on the second photoresist; performing electron beam exposure on the second photoresist in the area of ​​the first elongated aperture and the second elongated aperture; performing electron beam exposure on the first photoresist and the second photoresist in the regions of the first connection portion opening and the second connection portion opening; performing electron beam exposure on the first photoresist in an area other than the first connection portion opening in the undercut structure area and the second connection portion opening; and developing the first photoresist and the second photoresist after electron beam exposure to obtain the photoresist film layer including the undercut structure.

11. The step of developing the first photoresist and the second photoresist after electron beam exposure to obtain the photoresist film layer including the undercut structure includes: a step of developing the first photoresist and the second photoresist after exposure in a developer; and cleaning the remaining photolithographically developed photoresist on the substrate with oxygen plasma to obtain the photoresist film layer including the undercut structure.

12. A production line facility, the production line facility including a spin coater, a photolithography device, and a deposition machine; The spin coater and the photolithography device are used to manufacture a photoresist film layer including an undercut structure on a substrate, the undercut structure including a first elongated aperture and a second elongated aperture, the first elongated aperture and the second elongated aperture being non-parallel; the deposition machine is used to produce a first elongated superconducting layer on the substrate with the undercut structure by performing deposition on the substrate at an inclined first angle relative to the photoresist film layer through the first elongated opening, wherein a projection of the first angle onto the substrate is perpendicular to the longitudinal direction of the first elongated opening; the deposition machine is further used to produce a second elongated superconducting layer on the undercut structure substrate by performing deposition at a second angle inclined to the substrate with respect to the photoresist film layer and passing through the second elongated opening, wherein the projection of the second angle onto the substrate is perpendicular to the longitudinal direction of the second elongated opening; and the first elongated superconducting layer and the second elongated superconducting layer intersect and are separated from each other at the intersection by an oxide layer, thereby forming a Josephson junction.

13. In the process of depositing the photoresist film layer on the substrate at a first angle, the deposition machine is further used to form a third long superconducting layer on the substrate having the undercut structure by passing through the second long opening; 13. The production line equipment according to claim 12, wherein the third elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

14. In the process of depositing the photoresist film layer on the substrate at a second angle, the deposition machine is further used to form a fourth elongated superconducting layer on the substrate having the undercut structure by passing through the first elongated opening; 13. The production line equipment according to claim 12, wherein the fourth elongated superconducting layer does not intersect with the first elongated superconducting layer and the second elongated superconducting layer.

15. 13. The production line equipment of claim 12, wherein the deposition machine is further used to perform an oxidation treatment on the first long superconducting layer before performing deposition on the substrate at a second angle with respect to the photoresist film layer, thereby forming an oxide layer on the surface of the first long superconducting layer.

16. the first elongated superconducting layer and a projection of the first elongated aperture on the substrate do not intersect, the second elongated superconducting layer and a projection of the second elongated aperture on the substrate do not intersect, and the undercut structure further includes a first connection portion aperture and a second connection portion aperture; 13. The production line equipment of claim 12, wherein the deposition machine is further used to deposit the photoresist film layer perpendicular to the substrate, passing through the first connection portion opening and the second connection portion opening to manufacture a first connection portion superconducting layer and a second connection portion superconducting layer on the substrate with the undercut structure, wherein the first connection portion superconducting layer and the first elongated superconducting layer form a superconducting connection, and the second connection portion superconducting layer and the second elongated superconducting layer form a superconducting connection.

17. The production line equipment further includes an etching machine; 17. The production line equipment of claim 16, wherein the etching machine is used to perform ion milling cleaning on an overlapping area between the first elongated superconducting layer and a projection of the first connection portion opening on the substrate, and an overlapping area between the second elongated superconducting layer and a projection of the second connection portion opening on the substrate, before the deposition machine performs deposition on the photoresist film layer perpendicular to the substrate.

18. 17. The production line equipment according to claim 16, wherein the extension direction of the first elongated aperture and the extension direction of the second elongated aperture are perpendicular to each other.

19. The production line equipment further includes a hot plate; the spin coater is used to spin coat a first photoresist to a first thickness on the substrate; the hot plate is used to perform a hardening process on the first photoresist, the spin coater is further used to spin coat a second photoresist having a second thickness on top of the first photoresist; the hot plate is further used to perform a hardening process on the second photoresist; the photolithography apparatus, exposing the second photoresist in the area of ​​the first elongated aperture and the second elongated aperture to an electron beam; performing electron beam exposure on the first photoresist and the second photoresist in the regions of the first connection portion opening and the second connection portion opening; and exposing the first photoresist in an area other than the first connection portion opening in the undercut structure area and the second connection portion opening to electron beam exposure, 13. The production line equipment of claim 12, wherein the photoresist film layer including the undercut structure is obtained by developing the first photoresist and the second photoresist after electron beam exposure.

Images