Nonlinear inductors, josephson junctions and methods of their fabrication and performance improvement

Abstract

The application discloses a nonlinear inductor, a Josephson junction and a method for manufacturing and improving performance thereof, and belongs to the field of quantum chip manufacturing. The Josephson junction comprises a first conductor layer, an insulating layer and a second conductor layer which are sequentially distributed; and the insulating layer is in a crystal state. The Josephson junction constructed in this form can obtain good interface quality and better current-voltage characteristics provided by the insulating layer in the crystal state.

Description

Technical Field

[0001] This application belongs to the field of quantum information, especially the field of quantum chip manufacturing. In particular, this application relates to a nonlinear inductor, a Josephson junction, and methods for manufacturing and improving the performance of the same. Background Technology

[0002] Josephson junctions, which can be used as switching elements, are applied in superconducting quantum circuits and can significantly influence the circuit's operating margin. The aluminum-based Josephson junction (Al / AlOx / Al) is the most widely used type. The Al / AlOx / Al form of the Josephson junction has a sandwich structure; its layered structure consists of a bottom Al electrode, an AlOx barrier layer, and a top Al electrode. However, current Josephson junctions of this type still have some performance issues in practical applications. For example, the coherence time of superconducting qubits formed using them needs further improvement, or the detection sensitivity of detection devices built based on them, such as superconducting interferometers, is low. Summary of the Invention

[0003] This application provides an example of a nonlinear inductor, a Josephson junction, and a method for fabricating and improving its performance. By introducing a crystalline insulating layer into the Josephson junction, the problems caused by the currently used amorphous AlOx barrier layer can be better avoided, thus obtaining a high-quality Josephson junction.

[0004] The solution presented in this application is implemented through the following steps.

[0005] In a first aspect, examples of this application present a Josephson knot, comprising:

[0006] First conductor layer; An insulating layer is formed on the surface of the first conductor layer; the insulating layer is crystalline. The first conductor layer is formed on the back side of the insulating layer; The first conductor layer and the second conductor layer are respectively in contact with the insulating layer, and the insulating layer is sandwiched between the first conductor layer and the second conductor layer.

[0007] Currently, most Josephson junctions use amorphous AlOx as the barrier layer. However, amorphous AlOx contains many defects, which introduce corresponding defects into the Josephson junctions fabricated based on it, thus affecting the performance of the Josephson junction.

[0008] In contrast, the example in this application uses a crystalline insulating layer as the barrier layer, which has fewer defects than an amorphous layer, thus offering greater potential for improving the performance of the Josephson junction. For example, the crystalline barrier layer has more uniform transmittance in space, which can be used to improve the current-voltage characteristics of the Josephson junction; furthermore, fewer structural defects can reduce noise introduced by structural defects, thereby preventing a shortening of the coherence time of the qubit and preventing a decrease in the detection sensitivity of the superconducting interferometer device fabricated based on it.

[0009] According to some examples of this application, one or both of the first conductor layer and the second conductor layer are grown with a selected crystal orientation; Optionally, the first conductor layer and the second conductor layer are grown with selected crystal orientations, and the crystal orientations of the first conductor layer and the second conductor layer are the same.

[0010] According to some examples of this application, there is a first preset difference between the lattice parameters of the insulating layer and the lattice parameters of the first conductor layer; And / or, there is a second preset difference between the lattice parameters of the insulating layer and the lattice parameters of the second conductor layer; Optionally, the first preset value is equal to the second preset value.

[0011] According to some examples in this application, the first conductor layer and the second conductor layer are made of the same material; And / or, the first conductor layer and the second conductor layer are aluminum, and the insulating layer is aluminum nitride; And / or, the insulating layer is monocrystalline.

[0012] In a second aspect, an example of this application presents a nonlinear inductor having the aforementioned Josephson junction.

[0013] In a third aspect, examples of this application propose a method for improving the performance of a Josephson junction, the performance of which also includes critical current uniformity and interface defects of the Josephson junction, the interfaces including the interface between the upper electrode layer and the barrier layer, and the interface between the lower electrode layer and the barrier layer, the Josephson junction comprising a sequentially distributed upper electrode layer, a barrier layer, and a lower electrode layer, the method comprising: In the process of fabricating a Josephson junction, operations are performed to make the barrier layer crystalline; and the materials of the upper electrode layer, the barrier layer, and the lower electrode layer are selected such that the upper electrode layer is lattice-matched with the barrier layer, and / or the lower electrode layer is lattice-matched with the barrier layer.

[0014] According to some examples of this application, the operation includes creating a barrier layer by radio frequency plasma nitriding or nitrogen radical nitriding; And / or, the lower electrode layer is aluminum, the barrier layer is aluminum nitride, and the operation includes forming crystalline aluminum nitride by providing nitrogen plasma and bonding it with aluminum on the surface of the lower electrode layer; Optionally, performance features include adjustable critical current.

[0015] In a fourth aspect, examples of this application provide a method for manufacturing a Josephson junction, the method comprising: using plasma energy to cause nitrogen to react with aluminum on the surface of a lower electrode layer under high energy to generate a crystalline aluminum nitride barrier layer, wherein the lower electrode layer is formed on the surface of a substrate and is made of aluminum. An aluminum top electrode layer is formed on the surface of the barrier layer.

[0016] According to some examples of this application, the plasma is provided by nitrogen ions, and the method of reacting nitrogen with aluminum on the surface of the lower electrode layer to generate a crystalline aluminum nitride barrier layer under plasma-powered conditions includes: bombarding the lower electrode layer with nitrogen plasma to form a crystalline aluminum nitride barrier layer. Alternatively, the plasma is provided by inert gas element ions. Under plasma-powered conditions, a method for reacting nitrogen with aluminum on the surface of the lower electrode layer to generate a crystalline aluminum nitride barrier layer includes: bombarding a lower electrode target material adsorbed with nitrogen with inert gas plasma to deposit and form a crystalline aluminum nitride barrier layer on the surface of the lower electrode layer.

[0017] According to some examples of this application, the upper electrode layer and the lower electrode layer are fabricated by magnetron sputtering; And / or, the manufacturing methods of the upper electrode layer and the lower electrode layer sequentially include: forming an electrode window by photolithography with a double layer of photoresist, depositing aluminum in the window by magnetron sputtering, and then peeling it off.

[0018] According to some examples of this application, when the barrier layer is fabricated by bombarding the lower electrode layer with nitrogen plasma, the method includes selecting to adjust the amount and bombardment time of the nitrogen plasma by controlling the amount and duration of nitrogen supply so that the fabricated Josephson junction has a given critical current density. And / or, the extension directions of the upper electrode layer and the lower electrode layer are intersecting.

[0019] The solution in this application example has at least the following beneficial effects: Using a crystalline insulating layer as the barrier layer of a Josephson junction allows the junction to benefit from its crystalline properties. For example, crystals have fewer structural defects than amorphous materials, thus reducing noise caused by structural defects and improving the coherence time of the superconducting qubits constructed using the Josephson junction in this application example. Attached Figure Description

[0020] To illustrate this more clearly, the accompanying drawings used in the description will be briefly introduced below.

[0021] Figure 1 This is a schematic diagram of the structure of a Josephson knot in the example of this application; Figure 2 This is a schematic diagram of another Josephson knot structure in the examples of this application; Figure 3 This is a schematic diagram of a process for manufacturing a Josephson knot, as shown in the example of this application. Figure 4 This application discloses a schematic diagram of the configuration structure of the barrier c-layer manufacturing equipment in the process flow of manufacturing Josephson junctions according to Embodiment 1 of this application; Figure 5 This application discloses a schematic diagram of the configuration structure of the barrier layer manufacturing equipment in the process flow of manufacturing Josephson junctions according to Embodiment 2 of this application; Figure 6 A flowchart illustrating the main steps in the manufacturing process of the Josephson junction in this application example is shown. Detailed Implementation

[0022] Quantum chips are the core components of quantum computers, and one of the important elements in quantum chips is the Josephson junction.

[0023] Josephson junctions possess a non-equidistant energy level system, and therefore their lowest two energy levels can be used to construct a two-level system in a superconducting qubit. The structure of a Josephson junction is generally a SIS structure, i.e., a sandwich structure of a superconducting layer-insulator-superconducting layer. Currently, Josephson junctions are typically fabricated using metallic Al.

[0024] The quality of Josephson junctions largely determines the performance of quantum chips and quantum computers. Therefore, there is a widespread pursuit of higher quality Josephson junctions. However, the quality of a Josephson junction can be influenced by factors such as material selection and manufacturing processes, making it difficult to obtain a high-quality Josephson junction.

[0025] As mentioned earlier, the applicant used an Al-based Josephson junction, specifically the Al / AlOx / Al form. However, its performance in practice is not satisfactory, or rather, it has considerable room for improvement. For example, in practical implementation, the inventors realized that the coherence time of qubits formed based on Al-based Josephson junctions needs to be improved or further enhancement can be explored, or that its sensitivity needs to be improved when used to fabricate devices such as superconducting interferometers.

[0026] Through research, the inventors discovered that although many factors may affect the performance of the Josephson junction, one important and easily adjustable factor is the barrier layer in the Josephson junction, namely the AlOx barrier layer.

[0027] Because current AlOx barrier layers are amorphous, they exhibit numerous structural defects, leading to noise and limiting the coherence time of qubits and the detection sensitivity of superconducting interferometers. Conversely, the problems of amorphous AlOx barrier layers can be easily and effectively mitigated, optimized, and improved through manufacturing processes. More specifically, the amorphous structure of AlOx barrier layers results in significant inhomogeneities (such as elemental composition across length / thickness ranges); furthermore, the interface between aluminum and the amorphous AlOx barrier layer contains numerous structural defects.

[0028] Based on the above understanding, the inventors believe that an alternative improvement is to use a crystalline barrier layer in the Josephson junction. However, directly using a crystalline barrier layer in an Al-based Josephson junction, such as fabricating an AlOx barrier layer as a crystalline layer, may not be so easy to achieve, or may have other drawbacks.

[0029] For example, the lattice parameter of Al is 2.81 Å, and the lattice parameter of alumina is 9.7 Å. Even if a crystalline AlOx barrier layer is used, there will still be a problem of large lattice parameter mismatch between the two (Al superconducting layer and AlOx barrier layer), which will result in severe structural defects at the contact interface.

[0030] Furthermore, a commonly used Al-based Josephson junction is the Al / AlOx / Al structure. This structure is typically fabricated using electron beam evaporation because it is compatible with the fabrication processes of Al electrodes and AlOx barrier layers.

[0031] One example of the manufacturing process is as follows: The bottom Al electrode and the top Al electrode are fabricated using an electron beam. The fabrication of the AlOx barrier layer requires the introduction of high-purity oxygen to oxidize the bottom Al electrode. Therefore, a sample transfer step is necessary during the AlOx barrier layer fabrication process. After the bottom Al electrode is deposited, the sample is transferred to a dedicated oxidation chamber to oxidize the bottom Al, thus fabricating the AlOx barrier layer. In other words, the fabrication steps of the aluminum film / aluminum electrode and the fabrication steps of the aluminum oxide barrier layer are completed in different chambers.

[0032] Oxidation can be categorized into two types: static oxidation and dynamic oxidation.

[0033] Static oxidation refers to oxidation by introducing a fixed amount of oxygen.

[0034] Dynamic oxidation refers to a method of oxidation that maintains constant chamber pressure while controlling the flow rate of oxygen.

[0035] In some practices, more complex oxidation processes are chosen to achieve multiple oxidation cycles. For example, an Al film is prepared, transferred to a dedicated oxidation chamber, and oxidized once to form an AlOx barrier layer; another Al film is prepared, transferred to the dedicated oxidation chamber again, and oxidized once more to form an AlOx barrier layer, and so on, to form an AlOx barrier layer.

[0036] In the aforementioned process for fabricating Josephson junctions in Al / AlOx / Al form using electron beam evaporation, the AlOx barrier layer produced by electron beam evaporation, regardless of whether it involves static / dynamic oxidation or multiple oxidation processes, is always amorphous and suffers from lattice mismatch with Al. Furthermore, the oxidation process is complex, requiring operation in different cavities, which increases the overall technological difficulty.

[0037] Based on the above, in the example of this application, the inventors propose using a crystalline barrier layer in the Josephson junction. Furthermore, by combining the selection of the upper and lower electrodes in the Josephson junction with the crystalline barrier layer (to reduce contact interface defects), the performance of the Josephson junction is further improved.

[0038] Based on the above analysis and the inventor's research, this application discloses a Josephson junction comprising a first conductor layer, an insulating layer, and a second conductor layer stacked sequentially. In some non-limiting embodiments, the first and second conductor layers may be independently selected as aluminum, and the insulating layer may be selected as aluminum nitride.

[0039] An insulating layer is formed on the surface of the first conductor layer, while the first conductor layer is formed on the back side of the insulating layer. Therefore, the first conductor layer and the second conductor layer are in contact with the insulating layer, with the insulating layer sandwiched between them. In other words, the insulating layer can be formed on top of the first conductor layer, and the second conductor layer can be formed on top of the insulating layer.

[0040] The illustrated scheme can be consulted. Figure 1 and Figure 2 .

[0041] Figure 1 In the Josephson junction 100A, there are a first conductor layer 101a, an insulating layer 102a, and a second conductor layer 103a. The first conductor layer 101a and the second conductor layer 103a have the same orientation, that is, they are distributed along the same extension trajectory.

[0042] Figure 2 In the Josephson junction 100B, a first conductor layer 101b, an insulating layer 102b, and a second conductor layer 103b are included. The first conductor layer 101b and the second conductor layer 103b have different orientations. Figure 2The example is a distribution along crisscrossing (such as perpendicular) extended trajectories.

[0043] Specifically, the insulating layer is crystalline (single crystal or polycrystalline; single crystal can achieve more desirable results). By using a crystalline insulating layer as a barrier layer, the structural defects and other problems present in amorphous materials can be avoided.

[0044] Based on similar applications, in some examples, the first and second conductor layers can also be constructed in crystalline form. Therefore, by selecting the process or materials, one or both of the first and second conductor layers can be grown in a selected crystal orientation to obtain superconductor layers with crystalline structures. In particular, in some examples, the first and second conductor layers can be grown in the same selected crystal orientation, i.e., the crystal orientations of the first and second conductor layers are identical.

[0045] Since the first conductor layer can be formed directly on the substrate, its crystal orientation can be based on the crystal structure of the substrate. Therefore, the substrate can be a crystalline substrate. For example, considering applications in superconducting quantum computers, the substrate could be crystalline sapphire or high-resistivity silicon.

[0046] As mentioned earlier, in Josephson junctions, interlayer contact interface defects can also degrade junction performance. Therefore, it is advantageous to purposefully select the contact interface structure. For example, controlling the lattice matching degree between the first conductor layer and the insulating layer, and the lattice matching degree between the second conductor layer and the insulating layer. Thus, in some examples, factors such as material and process can be selected to control a first preset difference between the lattice parameters of the insulating layer and the lattice parameters of the first conductor layer. Similarly, factors such as material and process can be selected to control a second preset difference (which may be the same as the first preset difference) between the lattice parameters of the insulating layer and the lattice parameters of the second conductor layer.

[0047] In other words, by controlling the degree of interlayer matching in a Josephson junction, structural defects at the interlayer contact interface can be reduced. That is, at the contact interface, the higher the degree of lattice parameter matching between the two layers, the fewer structural defects will be at the contact interface. For example, the degree of lattice matching can be measured using lattice mismatch. The lattice mismatch can be the ratio of twice the absolute value of the difference between the two lattice constants to the sum of their lattice constants; or, the ratio of the absolute value of the difference between the two lattice constants to the bits of one of their lattice constants. Therefore, in some examples, the interlayer lattice mismatch can be limited to less than 20%, or less than 10%, or less than 5%.

[0048] As mentioned earlier, the materials of each layer in a Josephson junction can also be related to its performance. In some examples, the first and second conductor layers can be made of the same material. In this way, the first and second conductor layers can be manufactured using the same equipment or similar / even identical processes, thereby reducing equipment debugging and switching operations in the manufacturing process. This can also reduce the difficulty of operation and improve the consistency of the process to a certain extent, which in turn helps to obtain higher quality junctions.

[0049] The Josephson structure in this application example has been described in detail above; now we turn to the description of its application case.

[0050] A nonlinear inductor can be constructed based on the Josephson junction described above, which includes at least the Josephson junction. Furthermore, for ease of use, it can be configured with connection structures (such as microstrip lines, coplanar waveguide transmission lines, etc.) to connect with other components. Alternatively, the nonlinear inductor with the Josephson junction can be combined with packaging processes (such as potting) to construct a standalone device, i.e., a discrete device.

[0051] In addition, based on the description of the above scheme and the analysis of actual conditions, this application also discloses a method for improving the performance of Josephson junctions.

[0052] The performance also includes the critical current consistency of the Josephson junction.

[0053] As mentioned earlier, in existing schemes using aluminum-based Josephson junctions, the structure is Al / AlOx / Al, where AlOx exists in an amorphous form. Therefore, compared to a crystalline barrier layer, amorphous AlOx presents more microstructural problems, such as poorer spatial transmittance and lower-quality current-voltage characteristics. The lower-quality current-voltage characteristics include batch-to-batch quality inconsistencies between Josephson junctions manufactured using the same process but from different batches, such as significant differences or large gaps in critical current densities between batches, and disorder / uncontrollability.

[0054] In the example of this application, taking a Josephson junction comprising an upper electrode layer, a barrier layer, and a lower electrode layer arranged sequentially as an example, the disclosed method for improving the critical current uniformity of a Josephson junction includes: performing an operation during the fabrication of the Josephson junction to make the barrier layer crystalline; and selecting the materials of the upper electrode layer, the barrier layer, and the lower electrode layer such that the upper electrode layer is lattice-matched with the barrier layer, and / or the lower electrode layer is lattice-matched with the barrier layer.

[0055] The lattice matching therein may, for example, be quantified and compared via the aforementioned lattice mismatch. Alternatively, the comparison may be performed by configuring the degree of lattice adaptation between the barrier layer and the upper electrode or lower electrode to be greater than the degree of lattice adaptation between aluminum and aluminum oxide in the existing Al / AlOx / Al Josephson junction.

[0056] That is, the absolute value of the difference between the lattice constants of aluminum and aluminum oxide in the existing Al / AlOx / Al Josephson junction is (A), and the absolute value of the difference between the lattice constants of the electrode layer and the barrier layer in the Josephson junction of the example scheme of the present application is B. Therefore, when B<A, it can be regarded as the lattice matching described in the examples of the present application. For example, the lattice parameter of Al is 2.81 Å, the lattice parameter of AlN is 3.11 Å, and the lattice parameter of aluminum oxide is 9.7 Å. Therefore, compared with the Al-aluminum oxide contact interface, the lattice parameters of the Al and AlN contact interface are more adapted, and an improved structure of the contact interface can be obtained.

[0057] Therefore, the scheme of the examples of the present application can obtain better current-voltage characteristics than the existing Al / AlOx / Al Josephson junction.

[0058] In addition, in the examples of the present application, the barrier layer is in a crystalline state. If the upper electrode layer is also in a crystalline state, the interface defects between the barrier layer and the upper electrode layer are relatively smaller than the case where either or both of them are amorphous. Similarly, the barrier layer is in a crystalline state, and if the lower electrode layer is also in a crystalline state, the interface defects between the barrier layer and the lower electrode layer are relatively smaller than the case where either or both of them are amorphous.

[0059] Further, since the lattice parameters of crystals of different materials may have significant differences, the defects at the contact interface of the crystals in contact with each other are associated with the lattice parameters of the two. For example, if the lattice parameters of the two are more matched, the defects at the contact interface are small.

[0060] In a specific implementation of the above scheme, in an optional example: the operation selected to obtain the crystalline barrier layer includes, for example, fabricating the barrier layer by radio frequency plasma nitridation or nitrogen radical nitridation. When the lower electrode layer (or the upper electrode layer, or both) is selected as aluminum and the barrier layer is selected as aluminum nitride, the operation includes providing nitrogen plasma, which combines with aluminum on the surface of the lower electrode layer to form crystalline aluminum nitride. Alternatively, other schemes may be pulsed laser deposition to fabricate the barrier layer. That is, the plasma may be formed by magnetron sputtering, radio frequency plasma, pulsed laser deposition, or the like, and then used to fabricate the barrier layer.

[0061] Preferably, fabricating the barrier layer in the above manner can help improve the critical current tunability of the Josephson junction. Therefore, it is understood that the aforementioned performance can also include the critical current tunability of the Josephson junction. This critical current tunability includes, for example, the ability to purposefully adjust the critical current density through its fabrication process. For instance, in an example of a barrier layer fabricated using nitrogen plasma nitriding, the critical current density of the Josephson junction in the barrier layer can be controlled by adjusting the nitrogen flow rate and nitriding time, which is difficult to achieve with a Josephson junction using AlOx as the barrier layer (including the relatively difficult-to-achieve crystalline state).

[0062] To facilitate implementation of the schemes exemplified in this application by those skilled in the art, a method for manufacturing a Josephson junction is also disclosed below. This method primarily achieves the reaction of nitrogen and aluminum under high-energy conditions to form aluminum nitride. The high-energy reaction is provided and achieved, for example, through plasma power supply.

[0063] Therefore, in the example, such as Figure 3 As shown, the method for manufacturing a Josephson junction includes: reacting nitrogen with aluminum on the surface of a lower electrode layer under plasma-powered conditions to generate a crystalline aluminum nitride barrier layer, wherein the lower electrode layer is formed on the surface of a substrate and is made of aluminum; and forming an upper electrode layer made of aluminum on the surface of the barrier layer.

[0064] The plasma can be provided by nitrogen, a reactant, for example, a plasma formed by nitrogen ions. Alternatively, the plasma can be provided by a non-reactant / inert gas element (which can be a rare gas element, such as argon), for example, an inert gas plasma, such as a plasma formed by argon ions.

[0065] In particular, when the barrier layer is fabricated by using nitrogen plasma / bombarding the lower electrode layer with nitrogen plasma, the fabrication process of the barrier layer may include: selecting to adjust the amount and bombardment time of nitrogen plasma by controlling the amount and duration of nitrogen supply so that the fabricated Josephson junction has a given critical current density.

[0066] Therefore, the operations for forming a crystalline barrier layer include: bombarding the lower electrode layer with nitrogen plasma to form a crystalline aluminum nitride barrier layer, or bombarding a lower electrode target material (which has the same material as the lower electrode layer, such as aluminum, and can therefore also be called an aluminum target material) with inert gas plasma and depositing the resulting aluminum nitride on the surface of the lower electrode layer, or reacting the nitrogen generated by the bombardment with aluminum on the surface of the lower electrode layer to form a crystalline aluminum nitride barrier layer, wherein the lower electrode layer is formed on the substrate surface and is made of aluminum.

[0067] In addition, the upper and lower electrode layers can be fabricated using various film deposition processes in integrated circuits, and this application does not impose any particular limitations on them. For example, the upper and lower electrode layers can be deposited using various deposition methods, such as chemical vapor deposition, physical vapor deposition (e.g., evaporation or sputtering), and other deposition processes. Exemplary examples include ion beam assisted deposition (IBAD), vacuum evaporation, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), chemical vapor deposition (CVD), and magnetron sputtering.

[0068] Furthermore, it may be necessary to remove one or more materials from the film during the manufacturing process to create a structure with a specific shape or configuration. Therefore, depending on the material to be removed, the removal process may include, for example, wet etching, dry etching, or lift-off processes. Additionally, known lithographic techniques (e.g., photolithography or electron beam lithography) can be used to pattern the materials forming the circuit elements described herein.

[0069] For example, the fabrication method of the upper and lower electrode layers can sequentially include: forming electrode windows on the substrate surface by photolithography using a double layer of photoresist, depositing aluminum in the windows by magnetron sputtering, and then peeling off the electrodes to form a Josephson junction. Depending on the extension and layout of the upper and lower electrodes, the orientation of the electrode windows is also different. Therefore, the extension directions of the upper and lower electrode layers can be the same or intersecting, for example, in... Figure 1 and Figure 2 As shown in the document.

[0070] In some examples, the upper and lower electrode layers can also be fabricated by magnetron sputtering. In this example, the step of transferring the material to another device for oxidation to form / AlOx, as described in the Al / AlOx / Al Josephson junction fabrication process, can be avoided. Therefore, by using magnetron sputtering to fabricate aluminum upper and lower electrodes and plasma to fabricate the AlN crystalline barrier layer, the process can be simplified, and the barrier layer can be prepared using nitrogen nitriding in the same chamber.

[0071] Generally, the respective structures are manufactured using plasma sputtering or its improved techniques.

[0072] Plasma sputtering is a physical vapor deposition technique that uses rare gases in a vacuum chamber to generate plasma through glow discharge to bombard the target material, causing atoms in the target material to be sputtered out and fall onto the surface of the workpiece to form a thin film.

[0073] The general process of plasma sputtering can be described as follows: First, a rare gas (such as argon) in a vacuum chamber is used to generate plasma through glow discharge. Positively charged argon ions are accelerated by applying a bias or other methods, causing them to bombard a planar substrate / target made of high-purity target material. This causes atoms on the target to detach from the target mass and exit, passing through the vacuum and landing on the surface of the workpiece to form a thin film. For example, in the fabrication of the lower electrode, atoms from an aluminum target can form a thin film on a substrate such as silicon.

[0074] It is worth noting that, for the sake of brevity, conventional techniques related to the manufacture of semiconductors and / or superconducting devices and integrated circuits (ICs) may or may not be described in detail herein. Furthermore, the various tasks and process steps described herein may be incorporated into more comprehensive procedures or processes with additional steps or functionalities not described in detail herein. In particular, the various steps in the manufacture of semiconductors and / or superconducting devices and semiconductor / superconductor-based ICs are well-known; therefore, for the sake of brevity, many conventional steps will be mentioned only briefly or will be omitted entirely without providing well-known process details.

[0075] Example 1 This example relates to the preparation of an AlN barrier layer via radio frequency plasma nitridation.

[0076] Please refer to the equipment configuration for AlN barrier layer fabrication. Figure 4 ;exist Figure 6 In the diagram, S1 represents the exposure pattern of the photoresist used to fabricate the bottom Al electrode; S2 represents the structure of the bottom electrode deposited in the photolithography window; S3 represents the structure of the barrier layer formed on the bottom electrode; S4 represents the exposure pattern of the photoresist used to fabricate the top Al electrode; S5 represents the structure of the top electrode (two electrodes) deposited in the photolithography window; and S6 represents the structure of the Josephson junction remaining after photoresist stripping.

[0077] See Figure 4 and Figure 6 The process of this example Josephson knot mainly includes: 1. Preparation of the bottom Al electrode; 2. Preparation of the AlN barrier layer; 3. Preparation of the top Al electrode; 4. Resin washing and peeling.

[0078] The steps of Josephson's knot are as follows.

[0079] 1. Fabrication of the underlying Al electrode (1) Exposure of the bottom Al electrode: The bottom Al electrode is exposed by electron beam exposure. The process includes spin coating of PMMA (polymethyl methacrylate) + MMA (methyl methacrylate) double layer adhesive, electron beam exposure, and development.

[0080] (2) An Al film was deposited by magnetron sputtering to prepare the bottom Al electrode. The process included evacuating the vacuum to 1000°C. 6 After argon gas is introduced and glow discharge is generated, the Al target baffle is opened. Following pre-sputtering, Al sputtering is performed. The magnetron sputtering parameters for Al film deposition are: target: Al target, initial pressure: 10... 6 Pa, power 500W, Ar flow rate 30sccm, thickness 50nm.

[0081] 2. AlN Barrier Layer Fabrication: After the underlying Al electrode is fabricated, AlN is then prepared using radio frequency plasma nitriding. The process involves closing the Al target baffle, applying a bias voltage to the electrode plate containing the substrate, introducing nitrogen gas, and generating nitrogen plasma. The Al atoms on the surface of the Al electrode in the nitrogen plasma combine to form AlN.

[0082] The parameters for radio frequency plasma nitriding are: power 500W, voltage 350V, N2 flow rate 10sccm, working pressure set to 0.5Pa, and thickness 5nm.

[0083] 3. Fabrication of the top Al electrode: (1) Exposure of the bottom Al electrode: The top Al electrode is exposed by electron beam exposure. The process includes spin coating of PMMA+MMA double layer adhesive, electron beam exposure, and development.

[0084] (2) An Al film was deposited by magnetron sputtering to prepare the top Al electrode. The parameters for magnetron sputtering Al film were: target material: Al target material, initial pressure: 10 6 Pa, power 500W, Ar flow rate 30sccm, thickness 90nm.

[0085] 4. Use NMP / IPA to wash the adhesive, peel it off, and the Al / AlN / Al Josephson junction is prepared.

[0086] Example 2 This example relates to the preparation of an AlN barrier layer via radical nitridation.

[0087] Please refer to the equipment configuration for AlN barrier layer fabrication. Figure 5 ;exist Figure 6In the diagram, S1 represents the exposure pattern of the photoresist used to fabricate the bottom Al electrode; S2 represents the structure of the bottom electrode deposited in the photolithography window; S3 represents the structure of the barrier layer formed on the bottom electrode; S4 represents the exposure pattern of the photoresist used to fabricate the top Al electrode; S5 represents the structure of the top electrode (two electrodes) deposited in the photolithography window; and S6 represents the structure of the Josephson junction remaining after photoresist stripping.

[0088] See Figure 5 and Figure 6 The process of this example Josephson knot mainly includes: 1. Fabrication of the bottom Al electrode; 2. Fabrication of the AlN barrier layer; 3. Fabrication of the top Al electrode; 4. Resin washing and peeling.

[0089] The steps of Josephson's knot are as follows.

[0090] 1. Fabrication of the underlying Al electrode (1) Exposure of the bottom Al electrode: The bottom Al electrode is exposed by electron beam exposure. The process includes spin coating of PMMA+MMA double layer adhesive, electron beam exposure, and development.

[0091] (2) An Al film was deposited by magnetron sputtering to prepare the bottom Al electrode. The process included evacuating the vacuum to 1000°C. -6 After argon gas is introduced and glow discharge is generated, the Al target baffle is opened. Following pre-sputtering, Al sputtering is performed. The magnetron sputtering parameters for Al film deposition are: target: Al target, initial pressure: 10... -6 Pa, power 500W, Ar flow rate 30sccm, thickness 50nm.

[0092] 2. Preparation of AlN barrier layer: After the preparation of the bottom Al electrode is completed, nitrogen gas is introduced. Argon ions bombard the Al target material and the adsorbed nitrogen gas at the same time. The two combine to form AlN.

[0093] The parameters for free radical nitridation are: power 500W, N2 flow rate 10sccm, working pressure 0.5Pa, and thickness 5nm.

[0094] 3. Fabrication of the top Al electrode: (1) Exposure of the bottom Al electrode: The top Al electrode is exposed by electron beam exposure. The process includes spin coating of PMMA+MMA double layer adhesive, electron beam exposure, and development.

[0095] (2) An Al film was deposited by magnetron sputtering to prepare the top Al electrode. The parameters for magnetron sputtering Al film were: target material: Al target material, initial pressure: 10 -6 Pa, power 500W, Ar flow rate 30sccm, thickness 90nm.

[0096] 4. Use NMP / IPA to wash the adhesive, peel it off, and the Al / AlN / Al Josephson junction is prepared.

[0097] The embodiments described above with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0098] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, one or more embodiments have been described above with reference to the accompanying drawings. Throughout the description, similar reference numerals are used to denote similar components. In the foregoing description, numerous specific details have been set forth for illustrative purposes in order to provide a more thorough understanding of one or more embodiments. However, it will be apparent that one or more embodiments may be practiced in various circumstances without these specific details, and the embodiments may be combined with and referenced to each other without contradiction.

[0099] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0100] Additionally, it should be understood that when a layer (or film), region, pattern, or structure is referred to as being "on" a substrate, layer (or film), region, and / or pattern, it can be located directly on another layer or substrate, and / or intercalation layers may also be present. Furthermore, it should be understood that when a layer is referred to as being "under" another layer, it can be located directly under that layer, and / or one or more intercalation layers may also be present. Additionally, references to "on" and "under" the layers may be made based on the accompanying drawings.

[0101] The above description, based on the embodiments shown in the drawings, details the structure, features, and effects of this application. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A Josephson knot, characterized in that, include: First conductor layer; An insulating layer formed on the surface of the first conductor layer, wherein the insulating layer is crystalline; A second conductor layer is formed on the back side of the insulating layer; The first conductor layer and the second conductor layer are respectively in contact with the insulating layer, and the insulating layer is sandwiched between the first conductor layer and the second conductor layer; The Josephson knot is manufactured by the following method: Using plasma as energy, nitrogen reacts with aluminum on the surface of the lower electrode layer under high energy to generate a crystalline aluminum nitride barrier layer, wherein the lower electrode layer is formed on the substrate surface and is made of aluminum; and an upper electrode layer made of aluminum is formed on the surface of the barrier layer. The plasma is provided by inert gas element ions. Under plasma-powered conditions, a method for reacting nitrogen with aluminum on the surface of the lower electrode layer to generate a crystalline aluminum nitride barrier layer includes: bombarding a lower electrode target material adsorbed with nitrogen with inert gas plasma to deposit and form a crystalline aluminum nitride barrier layer on the surface of the lower electrode layer.

2. The Josephson knot according to claim 1, characterized in that, One or both of the first conductor layer and the second conductor layer are grown with a selected crystal orientation.

3. The Josephson knot according to claim 2, characterized in that, The first conductor layer and the second conductor layer are grown with selected crystal orientations, and the crystal orientations of the first conductor layer and the second conductor layer are the same.

4. The Josephson knot according to claim 1, 2, or 3, characterized in that, There is a first preset difference between the lattice parameters of the insulating layer and the lattice parameters of the first conductor layer; And / or, there is a second preset difference between the lattice parameters of the insulating layer and the lattice parameters of the second conductor layer.

5. The Josephson knot according to claim 1, 2, or 3, characterized in that, The lattice parameters of the insulating layer and the lattice parameters of the first conductor layer have a first preset difference; the lattice parameters of the insulating layer and the lattice parameters of the second conductor layer have a second preset difference; the first preset value and the second preset value are equal.

6. The Josephson knot according to claim 1, characterized in that, The first conductor layer and the second conductor layer are made of the same material; And / or, the first conductor layer and the second conductor layer are aluminum, and the insulating layer is aluminum nitride; And / or, the insulating layer is a single crystal.

7. A nonlinear inductor, characterized in that, It has a Josephson knot as described in any one of claims 1 to 6.

8. A method for improving the performance of a Josephson junction, the performance including critical current uniformity and interface defects of the Josephson junction, the Josephson junction comprising a top electrode layer, a barrier layer, and a bottom electrode layer sequentially distributed, the interfaces including the interface between the top electrode layer and the barrier layer, and the interface between the bottom electrode layer and the barrier layer, characterized in that, The method includes: During the fabrication of the Josephson junction, operations are performed to make the barrier layer crystalline; and, Choose the materials of the upper electrode layer, barrier layer and lower electrode layer so that the upper electrode layer is lattice-matched with the barrier layer and / or the lower electrode layer is lattice-matched with the barrier layer. The Josephson knot is manufactured by the following method: Using plasma as energy, nitrogen reacts with aluminum on the surface of the lower electrode layer under high energy to generate a crystalline aluminum nitride barrier layer, wherein the lower electrode layer is formed on the substrate surface and is made of aluminum; and an upper electrode layer made of aluminum is formed on the surface of the barrier layer. The plasma is provided by inert gas element ions. Under plasma-powered conditions, a method for reacting nitrogen with aluminum on the surface of the lower electrode layer to generate a crystalline aluminum nitride barrier layer includes: bombarding a lower electrode target material adsorbed with nitrogen with inert gas plasma to deposit and form a crystalline aluminum nitride barrier layer on the surface of the lower electrode layer.

9. The method according to claim 8, characterized in that, The operation includes manufacturing the barrier layer by radio frequency plasma nitridation or nitrogen radical nitridation; And / or, the lower electrode layer is aluminum, the barrier layer is aluminum nitride, and the operation includes forming crystalline aluminum nitride by providing nitrogen plasma and bonding it with aluminum on the surface of the lower electrode layer.

10. The method according to claim 8, characterized in that, The performance also includes the adjustable critical current of the Josephson junction.

11. A method for manufacturing Josephson knots, characterized in that, The method includes: Using plasma as energy, nitrogen reacts with aluminum on the surface of the lower electrode layer under high energy to generate a crystalline aluminum nitride barrier layer, wherein the lower electrode layer is formed on the substrate surface and is made of aluminum. In addition, an aluminum top electrode layer is formed on the surface of the barrier layer; The plasma is provided by inert gas element ions. Under plasma-powered conditions, a method for reacting nitrogen with aluminum on the surface of the lower electrode layer to generate a crystalline aluminum nitride barrier layer includes: bombarding a lower electrode target material adsorbed with nitrogen with inert gas plasma to deposit and form a crystalline aluminum nitride barrier layer on the surface of the lower electrode layer.

12. The method according to claim 11, characterized in that, The upper and lower electrode layers are manufactured by magnetron sputtering. And / or, the manufacturing methods of the upper electrode layer and the lower electrode layer sequentially include: forming an electrode window by photolithography with a double layer of photoresist, depositing aluminum in the window by magnetron sputtering, and then peeling it off.

13. The method according to claim 11 or 12, characterized in that, When the barrier layer is fabricated by bombarding the lower electrode layer with nitrogen plasma, the method includes selecting to adjust the amount and bombardment time of the nitrogen plasma by controlling the amount and duration of nitrogen supply so that the fabricated Josephson junction has a given critical current density. And / or, the extension directions of the upper electrode layer and the lower electrode layer are intersecting.

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