Josephson junction film, preparation method thereof and semiconductor structure

Abstract

According to the Josephson junction film, the preparation method thereof and the semiconductor structure provided by the invention, the preparation of the Josephson junction film can be completed in the same cavity of ion beam deposition, the oxidation of transmission on a superconducting film is reduced, the operation is relatively simpler, the steps are fewer, and the productivity is much higher than that of the original multi-cavity linkage; the prepared Josephson junction thin film is not damaged by plasma, the prepared superconducting thin film has preferred orientation, the resistance can be better reduced, the prepared barrier layer thin film is good in continuity and lower in roughness, the content of nitrogen or oxygen or silicon in the barrier layer can be accurately regulated and controlled, and finally the Josephson junction with excellent performance is obtained.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and more specifically to a Josephson junction thin film and a preparation method thereof, and a semiconductor structure. Background Art

[0002] According to Moore's Law, the number of transistors that can be accommodated on an integrated circuit will double every 18-24 months, and the volume will be reduced by half. However, in recent years, Moore's Law has been difficult to continue the exponential growth trend. There are two main reasons why Moore's Law is difficult to continue. First, the behavior of quantum tunneling in classical bit quanta will cause expression failure, and classical computing will not be able to proceed; second, the device is close to the nanoscale, and the heat dissipation of the device faces huge challenges. Therefore, quantum computing must be the development direction of future computing.

[0003] The smallest information processing unit of a quantum computer is a quantum bit, while a classical computer uses binary 0 or 1 and logic gates to process information. The logical operations of a quantum computer rely on quantum bits |0>, |1>. Since the quantum state is in an uncertain relationship, the two states may exist at the same time, that is, each quantum bit can represent two states at the same time, rather than the classical state of either 0 or 1. Therefore, the most prominent advantage of quantum computing is parallel computing. Each quantum bit can represent two storage states at the same time. As the number of quantum bits increases, the quantum information processing capability grows exponentially. The greater the amount of information, the more obvious the advantage of quantum computing, which has incomparable, fast, and highly confidential computing capabilities that ordinary computers cannot match.

[0004] As one of the solutions to realize quantum computing, superconducting qubits have attracted much attention for their advantages such as easy design and processing, low power consumption, and easy scalability. Quantum computing can be realized based on the superconducting qubit solution composed of superconducting Josephson junctions and superconducting loops. The Josephson junction is the core device of the superconducting qubit, and obtaining high-quality junctions is the basic requirement and key link for realizing specific qubit solutions. Therefore, how to provide a simple preparation method and to prepare a damage-free Josephson junction film is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of this, in order to solve the above problems, the present invention provides a Josephson junction thin film and a preparation method thereof, and a semiconductor structure. The technical solution is as follows:

[0006] A method for preparing a Josephson junction thin film is based on an ion beam deposition process and is prepared in-situ in the same chamber. The method comprises:

[0007] controlling a sputtering ion source to bombard the first target material to form a lower superconducting layer with a specific lattice orientation on one side of the substrate;

[0008] Controlling the sputtering ion source to bombard the second target material, and controlling the auxiliary ion source to generate a reactive ion beam to form a barrier layer on a side of the lower superconducting layer away from the substrate;

[0009] The sputtering ion source is controlled to bombard the third target material to form an upper superconducting layer with a specific lattice orientation on a side of the barrier layer facing away from the substrate.

[0010] Preferably, in the above preparation method, before forming the lower superconducting layer, the preparation method further comprises:

[0011] The auxiliary ion source is controlled to perform a pre-cleaning process on the surface of the substrate.

[0012] Preferably, in the above preparation method, after forming the upper superconducting layer, the preparation method further comprises:

[0013] The sputtering ion source is controlled to bombard the fourth target material, and the auxiliary ion source is controlled to generate a reactive ion beam to form a passivation protection layer on a side of the upper superconducting layer away from the substrate.

[0014] Preferably, in the above preparation method, the material of the lower superconducting layer is Al, Nb, NbN, NbTi, Nb 3 Sn、Nb 3 Al, MgB 2 A combination of one or more of .

[0015] Preferably, in the above preparation method, the material of the barrier layer is a semiconductor material or an insulating material.

[0016] Preferably, in the above preparation method, the material of the barrier layer is Al 2 O 3 、SiN x 、 2 O 5 、NbSi x , and a combination of one or more of MgO.

[0017] Preferably, in the above preparation method, the material of the upper superconducting layer is Al, Nb, NbN, NbTi, Nb 3 Sn、Nb 3 Al, MgB 2 A combination of one or more of .

[0018] Preferably, in the above preparation method, the reactive gas used in the ion beam deposition process is O 2 、N 2 、SiF 4 A combination of one or more of .

[0019] Preferably, in the above preparation method, the inert gas used in the ion beam deposition process is a combination of one or more of He, Ne, Ar, Kr, and Xe.

[0020] Preferably, in the above preparation method, the preparation method further comprises:

[0021] During the preparation of the Josephson junction thin film, the substrate is controlled to rotate with the center of the substrate as the axis.

[0022] Preferably, in the above preparation method, the rotation rate of the substrate is controlled to be 1 r / min-200 r / min.

[0023] Preferably, in the above preparation method, controlling the sputtering ion source to bombard the first target material to form a lower superconducting layer with a specific lattice orientation on one side of the substrate comprises:

[0024] The relative angles among the sputtering ion source, the first target material and the substrate are adjusted to control the sputtering ion source to bombard the first target material, so as to form a lower superconducting layer with a specific lattice orientation on one side of the substrate.

[0025] Preferably, in the above preparation method, controlling the sputtering ion source to bombard the third target material to form an upper superconducting layer with a specific lattice orientation on a side of the barrier layer away from the substrate comprises:

[0026] The relative angles among the sputtering ion source, the third target material and the substrate are adjusted to control the sputtering ion source to bombard the third target material, so as to form an upper superconducting layer with a specific lattice orientation on a side of the barrier layer away from the substrate.

[0027] Preferably, in the above preparation method, controlling the sputtering ion source to bombard the second target material and controlling the auxiliary ion source to generate a reactive ion beam to form a barrier layer on a side of the lower superconducting layer away from the substrate comprises:

[0028] The sputtering ion source is controlled to bombard the second target material, the auxiliary ion source is controlled to generate a reactive ion beam, and the density of the reactive ion beam is regulated to form a barrier layer on a side of the lower superconducting layer away from the substrate.

[0029] Preferably, in the above preparation method, the preparation method further comprises:

[0030] The thicknesses of the lower superconducting layer, the barrier layer and the upper superconducting layer are detected by using a crystal oscillator.

[0031] Preferably, in the above preparation method, the ion beam in the ion beam deposition process is a neutral ion beam.

[0032] Preferably, in the above preparation method, the neutral ion beam includes an ion beam formed by any one or more inert gases of He, Ne, Ar, Kr, and Xe.

[0033] Preferably, in the above preparation method, the shape of the grid in the sputtering ion source is arc-shaped;

[0034] The radius of the arc is greater than or equal to 300 mm and less than or equal to 800 mm.

[0035] Preferably, in the above preparation method, the barrier layer is an oxide barrier layer, a nitride barrier layer, or a silicide barrier layer;

[0036] When the barrier layer is an oxide barrier layer, the oxygen content is 0.5-2;

[0037] When the barrier layer is a nitride barrier layer, the nitrogen content is 0.5-2;

[0038] When the barrier layer is a silicide barrier layer, the silicon content is 0.5-2.

[0039] Preferably, in the above preparation method, the thickness of the lower superconducting layer accounts for 5%-40% of the thickness of the Josephson junction film.

[0040] The present application also provides a Josephson junction film, which is prepared based on any of the preparation methods described above, and the Josephson junction film comprises:

[0041] substrate;

[0042] n stacking structures located on one side of the substrate, wherein the n stacking structures are stacked in sequence in a first direction, the first direction is perpendicular to the plane where the substrate is located, and points from the substrate to the stacking structures, and n≥2;

[0043] Wherein, the stacked structure comprises a lower superconducting layer, a barrier layer and an upper superconducting layer which are sequentially stacked in the first direction;

[0044] The Josephson junction film further comprises:

[0045] A passivation protection layer is located on a side of the nth stacked structure away from the substrate.

[0046] The present application also provides a semiconductor structure, which includes the Josephson junction film described above.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention provides a method for preparing a Josephson junction film based on an ion beam deposition process in-situ in the same chamber, comprising: controlling a sputtering ion source to bombard a first target material, forming a lower superconducting layer with a specific lattice orientation on one side of a substrate; controlling the sputtering ion source to bombard a second target material, controlling the auxiliary ion source to generate a reactive ion beam to form a barrier layer on the side of the lower superconducting layer away from the substrate; controlling the sputtering ion source to bombard a third target material, forming an upper superconducting layer with a specific lattice orientation on the side of the barrier layer away from the substrate. The preparation of the Josephson junction film can be completed in the same chamber, reducing the oxidation of the superconducting film by transmission, relatively simpler operation, fewer steps, and much higher production capacity than the original multi-chamber linkage. The prepared Josephson junction film will not be damaged by plasma, the prepared superconducting film has a preferred orientation, can better reduce resistance, the prepared barrier layer film has good continuity, lower roughness, and the content of nitrogen, oxygen or silicon in the barrier layer can be precisely controlled, and finally a Josephson junction with excellent performance is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0050] Figure 1 This is a schematic diagram of the structure of a superconducting Josephson junction;

[0051] Figure 2 Schematic diagram of energy level distribution of Josephson junction;

[0052] Figure 3 This is a schematic diagram of the IV curve of an ideal Josephson junction;

[0053] Figure 4 A schematic flow chart of a method for preparing a Josephson junction thin film provided in an embodiment of the present invention;

[0054] Figure 5 for Figure 4 A schematic diagram of a part of the structure corresponding to the preparation method shown;

[0055] Figure 6 A schematic diagram of ion beam deposition provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a superconducting Josephson junction. A Josephson junction consists of two superconductors separated by a very thin semiconductor / insulator, so electrons can pass through the barrier layer in the middle. The current between superconductors when there is no voltage is called the Josephson current, and the movement of electrons through the barrier is called Josephson tunneling. Two or more junctions connected together by a superconducting path constitute a Josephson interferometer.

[0058] refer to Figure 2 , Figure 2 This is a schematic diagram of the energy level distribution of the Josephson junction. The Josephson junction has nonlinear circuit characteristics. Usually, the two lowest energy levels, the ground state and the first excited state, are used as the |0> and |1> states of the quantum bit, corresponding to 0 and 1 of the classical computer, thus forming a superconducting quantum bit. In addition, the energy dissipation of the superconducting Josephson junction is almost negligible, making it an ideal basic building block. With the help of the nonlinear superconducting Josephson junction LC circuit, the quantum computer circuit can be quantized, and the macroscopic quantum effect can be observed and modulated. Based on circuit quantization, the number of Cooper pairs tunneling in the Josephson junction can be changed by controlling the size of the macroscopic current, thereby modulating the quantum states |0> and |1>, and the signal can be stored and calculated with the help of the high and low changes in the voltage signal.

[0059] refer to Figure 3 , Figure 3 This is a schematic diagram of the ideal Josephson junction IV curve. By controlling the bias current I and the Josephson junction critical current I C The ratio of can regulate the height of the potential barrier and the energy level spacing in the potential well. When the voltage at both ends of the Josephson junction is further regulated, the macroscopic superconducting circuit can indirectly show observable microscopic quantum properties. The IV characteristic curve of the ideal Josephson junction is as follows: Figure 3 As shown. Based on this, the microscopic quantum states |0> and |1> can be modulated by adjusting the macroscopic bias current to achieve quantum computing.

[0060] Although superconducting quantum computing has powerful capabilities, the fragility of superconducting junctions seriously inhibits its performance, and decoherence time is considered to be the biggest obstacle to realizing quantum computing. Decoherence refers to the loss of quantum states due to interactions with the surrounding environment and devices, such as thermal, electrical, magnetic radiation environments, material defects, etc., which cause the information stored in the quantum computer to decay. This continuous interaction causes the quantum bit information to collapse into a classical state, affecting the performance of the quantum computer, such as computing power, stability, accuracy, etc.

[0061] Prolonging the decoherence time is currently the most important topic in quantum computing. However, defects will be introduced in various links such as the structural design, material preparation, chip manufacturing, and working environment of superconducting quantum circuits, which will deteriorate the coherence of superconducting quantum computing. From a microscopic structural analysis, most of this is attributed to the material and surface interface. Impurities, oxidation, defect energy levels, etc. will couple with quantum bits, causing energy dissipation and phase decoherence of quantum bits, especially in the barrier layer of the Josephson junction. The electric field and magnetic field are relatively concentrated in the space near the junction, and the coupling strength of these defect energy levels and bits is greater. Therefore, the quality of the Josephson junction process will directly affect the coherence time of the quantum bit. Therefore, in the invention and creation process of this application, it is found that from the perspective of materials and processes, the process scheme of the Josephson junction is fully optimized, especially the thin film deposition process is the most effective way to prolong the decoherence time and improve the performance of quantum computing.

[0062] At present, the research on the decoherence mechanism has achieved certain results. Here we focus on the preparation process of the Josephson junction, which has the greatest impact, among which the etching and coating processes are the most critical. The main factors that affect the final coherence expression of the Josephson junction can be roughly divided into several categories:

[0063] 1. Cleanliness of the device core interface, such as

[0064] 1) There are a large number of impurities and defects in the Josephson junction barrier layer, the surface of superconducting materials, and the interfaces between various materials, such as the natural oxide layer, surface dangling bonds, small molecular cluster adsorption, residual glue, and two-level defects caused by substrate damage, which in turn produce decoherence channels and inhibit the expression of quantum properties.

[0065] 2) Magnetic impurities and magnetic field noise caused by electron spins originating from surface dangling bonds, surface adsorbed hydrogen and oxygen small molecules, and oxide layer defects will also cause energy loss and decoherence.

[0066] 3) Dielectric loss caused by oxidation of superconducting materials suppresses decoherence time.

[0067] 2. Surface roughness. High roughness causes fluctuations in critical current and even leakage current. The greater the surface roughness, the larger the volume of the surface oxide layer, resulting in more losses and decoherence.

[0068] 3. The decoherence time of the superconducting lattice will also be seriously suppressed due to plasma damage.

[0069] 4. Preparation of vacuum conditions and the connection between different process steps will cause secondary oxidation and surface contamination of the device due to exposure to the atmosphere, which is not conducive to reducing losses and improving the overall decoherence of the device.

[0070] It is obvious that the performance of the surface interface is the core of improving the decoherence time of the Josephson junction, and the deposition process is the most directly related to the performance of the surface interface. The quality of the deposition process directly affects the expression of the final performance of the Josephson junction. At present, the Josephson junction is generally deposited by interconnecting multiple chambers. Generally, the substrate surface is cleaned in a pre-clean chamber, and then transferred to the deposition chamber for deposition of the lower superconducting layer, and then the middle barrier layer is deposited. Generally, the barrier layer is also realized by two-step deposition. In order to prevent the superconducting layer from being oxidized, the metal is deposited first, and then the sample is transferred to another oxidation chamber for oxidation of the barrier layer. After that, the sample is transferred to the deposition chamber for deposition of the upper superconductor. In order to prevent the upper superconducting layer from being destroyed by water and oxygen in the air, a passivation protective layer needs to be deposited on it before breaking the vacuum.

[0071] It can be seen that the current preparation method is very cumbersome and requires too much equipment linkage, and the current deposition equipment mostly uses the physical vapor deposition method, which produces Ar + The plasma and the deposited film are in the same chamber, and the plasma will damage the deposited film, seriously deteriorating the performance of the Josephson junction.

[0072] In response to the above problems, the present application provides a Josephson junction film and a preparation method thereof. The preparation of the Josephson junction film can be completed in the same chamber, reducing the oxidation of the superconducting film due to transmission. The operation is relatively simpler, with fewer steps, and the production capacity is much higher than the original multi-chamber linkage. The prepared Josephson junction film will not be damaged by plasma. The prepared superconducting film has a preferential orientation and can better reduce the resistance. The prepared barrier layer film has good continuity and lower roughness, and the nitrogen and oxygen content in the barrier layer can be precisely controlled, ultimately obtaining a Josephson junction with excellent performance.

[0073] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0074] refer to Figure 4 , Figure 4 A schematic diagram of a method for preparing a Josephson junction thin film according to an embodiment of the present invention is provided. Figure 5 , Figure 5 for Figure 4 The schematic diagram of the partial structure corresponding to the preparation method shown in FIG. Figure 6 , Figure 6 A schematic diagram of ion beam deposition provided by an embodiment of the present invention.

[0075] The method for preparing the Josephson junction thin film provided in the embodiment of the present application is based on in-situ same-chamber preparation by ion beam deposition process, comprising:

[0076] S101: Control the auxiliary ion source to perform a pre-cleaning process on the surface of the substrate 11.

[0077] Specifically, in this step, the auxiliary ion source is controlled to pre-clean the surface of the substrate 11 to remove the natural oxide layer 12 and dirt on the surface of the substrate 11, increase the adhesion of the subsequent deposited film layer, and improve the film stability of the Josephson junction thin film.

[0078] It should be noted that step S101 can be performed as a selective step in the method for preparing the Josephson junction film, that is, step S101 is not a step that must be performed in the method for preparing the Josephson junction film. It just means that before forming the lower superconducting layer 13, controlling the auxiliary ion source to pre-clean the surface of the substrate 11 can improve the film stability of the Josephson junction film.

[0079] S102 : controlling a sputtering ion source to bombard a first target material, so as to form a lower superconducting layer 13 with a specific lattice orientation on one side of the substrate 11 .

[0080] Specifically, in this step, the material of the lower superconducting layer 13 is a superconducting material, for example, the material of the lower superconducting layer 13 is Al, Nb, NbN, NbTi, Nb 3 Sn、Nb 3 Al, MgB 2 One or more combinations thereof, that is, any superconducting material can be used to make the lower superconducting layer 13. It should be noted that the lower superconducting layer 13 should minimize the effects of plasma damage, oxidation, etc. on the deterioration of superconducting performance.

[0081] Furthermore, by adjusting the relative angle between the sputtering ion source, the first target material and the substrate 11 , the sputtering ion source is controlled to bombard the first target material, so as to form a lower superconducting layer 13 with a specific lattice orientation on one side of the substrate 11 .

[0082] That is to say, the sputtering ion source is controlled to bombard the first target material, which is a superconducting target material, to generate sputtered particles, and to deposit on one side of the substrate 11 to form the lower superconducting layer 13. In this process, by adjusting the relative angle between the sputtering ion source, the first target material and the substrate 11, the lower superconducting layer 13 with different preferred orientations can also be deposited, which can further reduce the resistance of the lower superconducting layer 13. That is, the lower superconducting layer 13 has a preferred orientation. In general, the lattice orientation of the lower superconducting layer 13 can be adjusted by angled ion beam deposition to form a lower superconducting layer 13 with a specific lattice orientation, so as to prepare a lower superconducting layer 13 with low resistivity and low heat energy consumption.

[0083] It should be noted that the thickness of the lower superconducting layer 13 accounts for 5%-40% of the thickness of the Josephson junction film. If the lower superconducting layer 13 is too thin, the superconducting transition temperature will be affected to move to a lower temperature, thereby reducing the operating temperature range of the superconducting junction.

[0084] S103 : controlling the sputtering ion source to bombard the second target material, and controlling the auxiliary ion source to generate a reactive ion beam to form a barrier layer 14 on a side of the lower superconducting layer 13 away from the substrate 11 .

[0085] Specifically, in this step, the material of the barrier layer 14 is a semiconductor material or an insulating material. For example, the material of the barrier layer 14 is Al 2 O 3 、SiN x 、 2 O 5 、NbSi x , MgO or more combinations thereof, in the embodiment of the present invention, the barrier layer 14 is an oxide barrier layer, a nitride barrier layer or a silicide barrier layer; when the barrier layer 14 is an oxide barrier layer, the oxygen content is 0.5-2; when the barrier layer 14 is a nitride barrier layer, the nitrogen content is 0.5-2; when the barrier layer 14 is a silicide barrier layer, the silicon content is 0.5-2.

[0086] Furthermore, the sputtering ion source is controlled to bombard the second target material, the auxiliary ion source is controlled to generate a reactive ion beam, and the density of the reactive ion beam is regulated to form a barrier layer 14 on a side of the lower superconducting layer 13 away from the substrate 11 .

[0087] That is to say, the sputtering ion source bombards the target material, and the auxiliary ion source generates a reactive ion beam. The sputtered particles react with the reactive ion beam to jointly deposit the intermediate barrier layer 14. By adjusting the density of the reactive ion beam, the content of oxygen / nitrogen / silicon elements in the barrier layer 14 can be precisely controlled to form an oxygen / nitrogen / silicon barrier layer with the expected content.

[0088] That is to say, ion beam deposition can prepare a nitride or oxide barrier layer 14 with adjustable nitrogen / oxygen content, such as AlO x , SiN x The nitrogen / oxygen content can be adjusted to prepare barrier layers 14 with different stoichiometric ratios. Optionally, nitrogen or oxygen can be introduced through an auxiliary ion source and different currents can be applied to the grid to adjust the nitrogen or oxygen content in the barrier layer 14. In general, a barrier layer 14 of continuously changing oxide or nitride can be prepared by adjusting the density of the reactive ion beam of the auxiliary ion source.

[0089] Similarly, ion beam deposition can prepare silicide barrier layers 14 with different silicon contents, NbSi x The silicon content in the barrier layer 14 of the silicide is precisely controlled by ion beam deposition to make the silicon content 0.5-2, and SiF 4 The silicon content in the barrier layer 14 can be adjusted by applying different currents to the grid.

[0090] Furthermore, by adjusting the ion beam deposition angle, energy and density, the uniformity of the barrier layer 14 can be precisely controlled. Better uniformity can improve sample yield and reduce the cost of a single chip. By adjusting the ion beam deposition energy and density, the roughness of the barrier layer 14 can also be precisely controlled. Excessive roughness will deteriorate the decoherence time of the superconducting junction, while low roughness can better exert the performance of the superconducting junction.

[0091] That is to say, in the embodiment of the present application, the barrier layer 14 has good continuity and low roughness, so that the transmission will not be hindered by defects during quantum transmission (tunneling).

[0092] S104 : controlling the sputtering ion source to bombard the third target material, so as to form an upper superconducting layer 15 with a specific lattice orientation on a side of the barrier layer 14 away from the substrate 11 .

[0093] Specifically, in this step, the material of the upper superconducting layer 15 is a superconducting material, for example, the material of the upper superconducting layer 15 is Al, Nb, NbN, NbTi, Nb 3 Sn、Nb 3 Al, MgB 2 One or more combinations thereof, that is, any superconducting material can be used to make the upper superconducting layer 15. It should be noted that the upper superconducting layer 15 should minimize the effects of plasma damage, oxidation, etc. on the deterioration of superconducting performance, and at the same time, it should also ensure that the contact between the upper superconducting layer 15 and the barrier layer 14 has as low a roughness as possible.

[0094] Furthermore, the relative angles among the sputtering ion source, the third target and the substrate 11 are adjusted to control the sputtering ion source to bombard the third target, thereby forming an upper superconducting layer 15 with a specific lattice orientation on the side of the barrier layer 14 away from the substrate 11 .

[0095] That is to say, the sputtering ion source is controlled to bombard the third target material, which is a superconducting target material, to generate sputtered particles, and to deposit the upper superconducting layer 15 on the side of the barrier layer 14 away from the substrate 11. In this process, by adjusting the relative angle between the sputtering ion source, the third target material and the substrate 11, the upper superconducting layer 15 with different preferred orientations can also be deposited, which can further reduce the resistance of the upper superconducting layer 15. That is, the upper superconducting layer 15 has a preferred orientation. In general, the lattice orientation of the upper superconducting layer 15 can be adjusted by angled ion beam deposition to form an upper superconducting layer 15 with a specific lattice orientation, so as to prepare an upper superconducting layer 15 with low resistivity and low heat energy consumption.

[0096] S105 : controlling the sputtering ion source to bombard the fourth target material, and controlling the auxiliary ion source to generate a reactive ion beam to form a passivation protection layer 16 on a side of the upper superconducting layer 15 away from the substrate 11 .

[0097] Specifically, in this step, the sputtering ion source bombards the target material, and the auxiliary ion source generates a reactive ion beam. The sputtered particles react with the reactive ion beam to jointly deposit a passivation protective layer 16. After leaving the chamber, the passivation protective layer 16 can protect the superconducting junction from contamination by oxygen and water vapor in the air.

[0098] It should be noted that step S102 to step S104 are the core key steps in the embodiment of the present application. Figure 4 In the above, only the overall logic of step S101 to step S105 is used as an example to illustrate. That is, step S105 to form the passivation protection layer 16 can be performed as an optional step, that is, step S105 is not a necessary step in the preparation method of the Josephson junction thin film, but the passivation protection layer 16 is formed after the upper superconducting layer 15 is formed, which can protect the superconducting junction from being polluted by oxygen and water vapor in the air.

[0099] It should be noted that when depositing different film layers, the angle between the substrate 11 and the auxiliary ion source can be adjusted.

[0100] It should be noted that, based on actual needs, steps S102 - S104 can be cycled to deposit a stacked Josephson junction with a high storage density.

[0101] From the above description, it can be seen that all processes of the preparation method of the Josephson junction film provided in the embodiment of the present application can be completed in an ion beam deposition chamber, without breaking the vacuum or transmitting, which greatly shortens the time and reduces the deterioration of the superconducting junction by water, oxygen, etc., and the film prepared by ion beam deposition has a preferred orientation resistivity, lower roughness and film damage, and improved decoherence time, which can well solve the problems of the existing preparation of Josephson junctions without the need for other process means.

[0102] Optionally, in another embodiment of the present invention, the preparation method further comprises:

[0103] During the preparation of the Josephson junction thin film, the substrate 11 is controlled to rotate with the center of the substrate 11 as the axis.

[0104] Specifically, in this embodiment, the rotation rate of the substrate 11 is controlled to be 1 r / min-200 r / min, that is, the substrate 11 keeps rotating during the process of depositing the film layer on the substrate 11 to improve the uniformity of the deposited film layer.

[0105] Optionally, in another embodiment of the present invention, the preparation method further comprises:

[0106] The thicknesses of the lower superconducting layer 13 , the barrier layer 14 , the upper superconducting layer 15 and the passivation protection layer 16 are detected by means of a crystal oscillator.

[0107] Specifically, in this embodiment, a crystal oscillator can be used to detect the thickness of the thin film deposition during the deposition process. Monitoring the film thickness can control the actual thickness of the film and ensure that each batch of samples has good stability and repeatability.

[0108] Optionally, in another embodiment of the present invention, the reactive gas used in the ion beam deposition process is O 2 、N 2 、SiF 4 A combination of one or more of .

[0109] Specifically, in this embodiment, the reactive gas is mainly used to form the barrier layer 14, ensuring that the oxygen / nitrogen / silicon elements in the barrier layer 14 can be precisely controlled to form a desired content.

[0110] Optionally, in another embodiment of the present invention, the inert gas used in the ion beam deposition process is a combination of one or more of He, Ne, Ar, Kr, and Xe.

[0111] Specifically, in this embodiment, the inert gas is mainly used to react with the substrate 11 or the target material, and only has the effect of physical sputtering.

[0112] Optionally, in another embodiment of the present invention, the ion beam of the ion beam deposition process is a neutral ion beam.

[0113] Specifically, in this embodiment, since film layer damage will deteriorate the decoherence time of the superconducting junction, a neutral ion beam is used to prepare a damage-free superconducting film and barrier layer to better exert the performance of the superconducting junction.

[0114] The neutral ion beam of the sputtering ion source includes an ion beam formed by any one or more inert gases of He, Ne, Ar, Kr, and Xe.

[0115] Optionally, in another embodiment of the present invention, since the sputtering effect of low-energy deposition is small and will not cause damage to the deposited film, the plasma energy of the auxiliary ion source assisted deposition in the embodiment of the present invention is less than or equal to 200 eV.

[0116] Optionally, in another embodiment of the present invention, the purity of the target material used for sputtering is above 99.99%, and is used to prepare a high-purity film layer to improve the performance of the Josephson junction thin film.

[0117] Optionally, in another embodiment of the present invention, the grid in the sputtering ion source is in an arc shape.

[0118] The radius of the arc is greater than or equal to 300 mm and less than or equal to 800 mm.

[0119] Specifically, in this embodiment, the arc-shaped grid is used to focus the ion beam into the target material, thereby ensuring the purity of the sputtered particles and ultimately ensuring the purity of the deposited film.

[0120] The preparation method of the Josephson junction thin film provided by the embodiment of the present invention is further described below by means of three specific embodiments: Specific embodiment one:

[0122] The thickness of the lower superconducting layer 13 is 50nm-150nm, and the material is Nb. The thickness of the barrier layer 14 is 3nm-10nm, and the material is NbSi X The thickness of the upper superconducting layer 15 is 50nm-150nm, and the material is Nb. The thickness of the passivation protection layer 16 is 10nm-30nm, and the material is silicon oxide. All film layers of the Josephson junction are deposited by ion beam deposition process. The rotation speed of the substrate during all deposition processes is 20r / min-100r / min. The specific steps are as follows:

[0123] First, Ar is introduced into the auxiliary ion source to generate a neutral ion beam with a high energy angle of 45°-75° to remove oxides on the surface of the substrate 11.

[0124] Secondly, Ar is introduced into the sputtering ion source to generate an ion beam to bombard the lower superconducting layer Nb target. The Nb particles sputtered from the target are deposited on the surface of the substrate 11 cleaned in the previous step under the promotion of the auxiliary ion source to form the lower superconducting layer 13 of the Nb thin film. The angle between the wafer and the normal direction of the auxiliary ion source is greater than 15°, and the gas of the auxiliary ion source is also an inert gas.

[0125] Furthermore, the sputtering ion source is introduced with Ar to generate an ion beam to bombard the NbSi target. The NbSi particles sputtered from the target are deposited on the upper surface of the Nb formed in the previous step under the reaction and promotion of the ion beam from the auxiliary ion source. X The barrier layer 14 of the film, the gas of the auxiliary ion source is SiF 4 and / or Ar.

[0126] Furthermore, Ar is introduced into the sputtering ion source to generate an ion beam to bombard the upper superconducting layer Nb target. The Nb particles sputtered from the target are deposited on the upper superconducting layer 15 of the Nb thin film formed on the upper surface of the barrier layer 14 in the previous step under the promotion of the auxiliary ion source. The angle between the wafer and the normal direction of the auxiliary ion source is greater than 15°, and the gas of the auxiliary ion source is also an inert gas.

[0127] Finally, the sputtering ion source is fed with Ar to generate an ion beam to bombard the Si target. The Si particles sputtered from the target are deposited on the upper surface of the upper superconducting layer 15 in the previous step under the reaction and promotion of the auxiliary ion source to form a passivation protective layer 16 of silicon oxide. The gas of the auxiliary ion source is O 2 and / or Ar. Specific embodiment 2:

[0129] The thickness of the lower superconducting layer 13 is 50nm-150nm, and the material is Al. The thickness of the barrier layer 14 is 3nm-10nm, and the material is Al. 2 O 3 The thickness of the upper superconducting layer 15 is 50nm-150nm, and the material is Al. The thickness of the passivation protection layer 16 is 10nm-30nm, and the material is silicon oxide. All the film layers of the Josephson junction are deposited by ion beam deposition process. The sample rotation speed during all deposition processes is 20r / min-100r / min. The specific steps are as follows:

[0130] First, Kr is introduced into the auxiliary ion source to generate a neutral ion beam with a maximum energy angle of 45°-75° to remove dirt and oxides on the surface of the substrate 11.

[0131] Secondly, Kr is introduced into the sputtering ion source to generate an ion beam to bombard the lower superconducting layer Al target. The Al particles sputtered from the target are deposited on the surface of the substrate 11 cleaned in the previous step under the promotion of the auxiliary ion source to form the lower superconducting layer 13 of the Al thin film. The angle between the wafer and the normal direction of the auxiliary ion source is greater than 15°, and the gas of the auxiliary ion source is also an inert gas.

[0132] Furthermore, Kr is introduced into the sputtering ion source to generate an ion beam to bombard the Al target. The Al particles sputtered from the target are deposited on the upper surface of the Al in the previous step under the reaction and promotion of the ion beam from the auxiliary ion source to form Al 2 O 3 The barrier layer 14 of the film, the gas of the auxiliary ion source is O 2 and / or Kr.

[0133] Furthermore, Kr is introduced into the sputtering ion source to generate an ion beam to bombard the upper superconducting layer Al target. The Al particles sputtered from the target are deposited on the upper surface of the barrier layer 14 of the previous step under the promotion of the auxiliary ion source to form an upper superconducting layer 15 of the Al thin film. The angle between the wafer and the normal direction of the auxiliary ion source is greater than 15°, and the gas of the auxiliary ion source is also an inert gas.

[0134] Finally, Kr is introduced into the sputtering ion source to generate an ion beam to bombard the Si target. The Si particles sputtered from the target are deposited on the upper surface of the upper superconducting layer 15 in the previous step under the reaction and promotion of the auxiliary ion source to form a passivation protective layer 16 of silicon oxide. The gas of the auxiliary ion source is O 2 and / or Kr. Specific embodiment three:

[0136] The thickness of the lower superconducting layer 13 is 50nm-150nm, and the material is NbN. The thickness of the barrier layer 14 is 3nm-10nm, and the material is Al. 2 O 3 The thickness of the upper superconducting layer 15 is 50nm-150nm, and the material is NbN. The thickness of the passivation protection layer 16 is 10nm-30nm, and the material is silicon oxide. All the film layers of the Josephson junction are deposited by ion beam deposition process. The sample rotation speed during all deposition processes is 20r / min-100r / min. The specific steps are as follows:

[0137] First, Xe is introduced into the auxiliary ion source to generate a neutral ion beam with a high energy angle of 45°-75° to remove oxides on the surface of the substrate 11.

[0138] Secondly, the sputtering ion source introduces Xe to generate an ion beam to bombard the lower superconducting layer Nb target. The Nb particles sputtered from the target are deposited on the surface of the cleaned substrate 11 in the previous step under the reaction and promotion of the auxiliary ion source to form the lower superconducting layer 13 of the NbN thin film. The angle between the wafer and the normal direction of the auxiliary ion source is greater than 15°. The gas of the auxiliary ion source is N 2 and / or Xe.

[0139] Furthermore, the sputtering ion source is introduced with Xe to generate an ion beam to bombard the Al target. The Al particles sputtered from the target are deposited on the upper surface of the NbN in the previous step under the reaction and promotion of the ion beam from the auxiliary ion source to form Al2 O 3 The barrier layer 14 of the film, the gas of the auxiliary ion source is O 2 and / or Xe.

[0140] Furthermore, the sputtering ion source is introduced with Xe to generate an ion beam to bombard the upper superconducting layer Nb target. The Nb particles sputtered from the target are deposited on the upper surface of the barrier layer 14 in the previous step under the promotion of the auxiliary ion source to form the upper superconducting layer 15 of the NbN thin film. The angle between the wafer and the normal direction of the auxiliary ion source is greater than 15°. The gas of the auxiliary ion source is N 2 and / or Xe.

[0141] Finally, the sputtering ion source is fed with Xe to generate an ion beam to bombard the Si target. The Si particles sputtered from the target are deposited on the upper surface of the upper superconducting layer 15 in the previous step under the reaction and promotion of the auxiliary ion source to form a passivation protective layer 16 of silicon oxide. The gas of the auxiliary ion source is O 2 and / or Xe.

[0142] Based on the above embodiment of the present invention, in another embodiment of the present invention, a Josephson junction film is further provided. The Josephson junction film is prepared based on the preparation method described in the above embodiment. The Josephson junction film includes:

[0143] A substrate; n stacking structures located on one side of the substrate, wherein the n stacking structures are stacked in sequence in a first direction, the first direction is perpendicular to the plane where the substrate is located, and points from the substrate to the stacking structures, and n≥2.

[0144] The stacked structure includes a lower superconducting layer, a barrier layer and an upper superconducting layer which are sequentially stacked in the first direction.

[0145] The Josephson junction film further includes: a passivation protection layer located on a side of the nth stacked structure away from the substrate.

[0146] In this embodiment, the number of stacked layers of the stacked structure is determined based on actual needs, and a stacked Josephson junction with a high storage density is deposited.

[0147] Based on the above embodiment of the present invention, another embodiment of the present invention further provides a semiconductor structure, which includes the Josephson junction film described in the above embodiment.

[0148] The above is a detailed introduction to a Josephson junction thin film and its preparation method and semiconductor structure provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0149] It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0150] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device that includes a series of elements is inherent to the elements, or also includes elements inherent to these processes, methods, articles or devices. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0151] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a Josephson junction thin film, characterized in that: Based on the in-situ same-chamber preparation by ion beam deposition process, the preparation method comprises: controlling a sputtering ion source to bombard the first target material to form a lower superconducting layer with a specific lattice orientation on one side of the substrate; Controlling the sputtering ion source to bombard the second target material, and controlling the auxiliary ion source to generate a reactive ion beam to form a barrier layer on a side of the lower superconducting layer away from the substrate; The sputtering ion source is controlled to bombard the third target material to form an upper superconducting layer with a specific lattice orientation on a side of the barrier layer facing away from the substrate.

2. The preparation method according to claim 1, characterized in that: The method of controlling the sputtering ion source to bombard the first target material to form a lower superconducting layer with a specific lattice orientation on one side of the substrate comprises: The relative angles among the sputtering ion source, the first target material and the substrate are adjusted to control the sputtering ion source to bombard the first target material, so as to form a lower superconducting layer with a specific lattice orientation on one side of the substrate.

3. The preparation method according to claim 1, characterized in that: The step of controlling the sputtering ion source to bombard the third target material to form an upper superconducting layer with a specific lattice orientation on a side of the barrier layer away from the substrate comprises: The relative angles among the sputtering ion source, the third target material and the substrate are adjusted to control the sputtering ion source to bombard the third target material, so as to form an upper superconducting layer with a specific lattice orientation on a side of the barrier layer away from the substrate.

4. The preparation method according to claim 1, characterized in that: The step of controlling the sputtering ion source to bombard the second target material and controlling the auxiliary ion source to generate a reactive ion beam to form a barrier layer on a side of the lower superconducting layer away from the substrate comprises: The sputtering ion source is controlled to bombard the second target material, the auxiliary ion source is controlled to generate a reactive ion beam, and the density of the reactive ion beam is regulated to form a barrier layer on a side of the lower superconducting layer away from the substrate.

5. The preparation method according to claim 1, characterized in that: Before forming the lower superconducting layer, the preparation method further comprises: The auxiliary ion source is controlled to perform a pre-cleaning process on the surface of the substrate.

6. The preparation method according to claim 1, characterized in that: After forming the upper superconducting layer, the preparation method further comprises: The sputtering ion source is controlled to bombard the fourth target material, and the auxiliary ion source is controlled to generate a reactive ion beam to form a passivation protection layer on a side of the upper superconducting layer away from the substrate.

7. The preparation method according to claim 1, characterized in that: The material of the lower superconducting layer is a combination of one or more of Al, Nb, NbN, NbTi, Nb3Sn, Nb3Al, and MgB2.

8. The preparation method according to claim 1, characterized in that: The barrier layer is made of semiconductor material or insulating material.

9. The preparation method according to claim 1, characterized in that: The material of the barrier layer is Al2O3, SiN x 、Ta2O5、NbSi x , and a combination of one or more of MgO.

10. The preparation method according to claim 1, characterized in that: The material of the upper superconducting layer is a combination of one or more of Al, Nb, NbN, NbTi, Nb3Sn, Nb3Al, and MgB2.

11. The preparation method according to claim 1, characterized in that: The reactive gas used in the ion beam deposition process is a combination of one or more of O2, N2, and SiF4.

12. The preparation method according to claim 1, characterized in that: The inert gas used in the ion beam deposition process is a combination of one or more of He, Ne, Ar, Kr, and Xe.

13. The preparation method according to claim 1, characterized in that: The preparation method further comprises: During the preparation of the Josephson junction thin film, the substrate is controlled to rotate with the center of the substrate as the axis.

14. The preparation method according to claim 13, characterized in that: The substrate is controlled to rotate at a rotation rate of 1 r / min-200 r / min.

15. The preparation method according to claim 1, characterized in that: The preparation method further comprises: The thicknesses of the lower superconducting layer, the barrier layer and the upper superconducting layer are detected by using a crystal oscillator.

16. The preparation method according to claim 1, characterized in that: The ion beam in the ion beam deposition process is a neutral ion beam.

17. The preparation method according to claim 16, characterized in that: The neutral ion beam includes an ion beam formed by any one or more inert gases of He, Ne, Ar, Kr, and Xe.

18. The preparation method according to claim 1, characterized in that: The shape of the grid in the sputtering ion source is arc-shaped; The radius of the arc is greater than or equal to 300 mm and less than or equal to 800 mm.

19. The preparation method according to claim 1, characterized in that: The barrier layer is an oxide barrier layer, a nitride barrier layer or a silicide barrier layer; When the barrier layer is an oxide barrier layer, the oxygen content is 0.5-2; When the barrier layer is a nitride barrier layer, the nitrogen content is 0.5-2; When the barrier layer is a silicide barrier layer, the silicon content is 0.5-2.

20. The preparation method according to claim 1, characterized in that: The thickness of the lower superconducting layer accounts for 5%-40% of the thickness of the Josephson junction film.

21. A Josephson junction film, characterized in that: The Josephson junction film is prepared based on the preparation method according to any one of claims 1 to 20, and the Josephson junction film comprises: substrate; n stacking structures located on one side of the substrate, wherein the n stacking structures are stacked in sequence in a first direction, the first direction is perpendicular to the plane where the substrate is located, and points from the substrate to the stacking structures, and n≥2; Wherein, the stacked structure comprises a lower superconducting layer, a barrier layer and an upper superconducting layer which are sequentially stacked in the first direction; The Josephson junction film further comprises: A passivation protection layer is located on a side of the nth stacked structure away from the substrate.

22. A semiconductor structure, characterized in that: The semiconductor structure includes the Josephson junction thin film as claimed in claim 21.

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