Josephson junction thin film and preparation method therefor, and semiconductor structure

Abstract

Provided in the present invention are a Josephson junction thin film and a preparation method therefor, and a semiconductor structure. The preparation of the Josephson junction thin film can be completed in the same chamber as ion beam deposition, thereby reducing the oxidation of a superconducting thin film by transportation, such that the relative operation is simpler, the steps are fewer, and the production capacity is also much higher than that of an original multi-chamber linkage. The prepared Josephson junction thin film is not damaged by plasma; a superconducting thin film prepared therefrom has the preferred orientation, and can better reduce resistance; and a barrier layer thin film prepared therefrom has good continuity and lower roughness, and the content of nitrogen or oxygen or silicon in the barrier layer can be accurately regulated and controlled, thereby finally obtaining a Josephson junction having good performance.

Description

A Josephson junction film and its preparation method, semiconductor structure

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 2, 2023, with application number 202310970985.X and invention name “A Josephson junction thin film, its preparation method, and semiconductor structure”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of semiconductor technology, and more particularly to a Josephson junction thin film and a preparation method thereof, as well as a semiconductor structure. Background Art

[0003] According to Moore's Law, the number of transistors on an integrated circuit doubles every 18-24 months, while the size decreases by half. However, in recent years, Moore's Law has struggled to maintain its exponential growth trend. This is due to two main factors: first, quantum tunneling in classical bits and quantum processes causes representation errors, rendering classical computing impossible; second, as devices approach the nanoscale, heat dissipation presents significant challenges. Therefore, quantum computing is the inevitable future of computing.

[0004] The smallest information processing unit of a quantum computer is the qubit, while classical computers use binary 0s or 1s and logic gates to process information. Quantum computers' logical operations rely on qubits (|0>, |1>). Because quantum states are in an uncertain relationship, both states can exist simultaneously. This means each qubit can represent two states simultaneously, rather than the classical 0-or-1 state. Therefore, the most prominent advantage of quantum computing is parallel computing. Each qubit can represent two storage states simultaneously. As the number of qubits increases, quantum information processing capabilities grow exponentially. The greater the amount of information, the more pronounced the advantages of quantum computing, offering unmatched speed and high security computing capabilities compared to conventional computers.

[0005] Superconducting qubits, as one of the solutions for achieving quantum computing, have attracted considerable attention for their ease of design and processing, low power consumption, and scalability. Quantum computing can be achieved using a superconducting qubit solution consisting of a superconducting Josephson junction and a superconducting loop. The Josephson junction is the core component of the superconducting qubit, and obtaining high-quality junctions is a fundamental requirement and a key step in implementing specific qubit solutions. Therefore, developing a simple and damage-free Josephson junction thin film preparation method is a pressing technical challenge for those skilled in the art.

[0006] Summary of the Invention

[0007] 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:

[0008] A method for preparing a Josephson junction thin film is based on an ion beam deposition process and is prepared in situ in a chamber. The method comprises:

[0009] 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;

[0010] 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 facing away from the substrate;

[0011] 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.

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

[0013] The auxiliary ion source is controlled to perform a pre-cleaning process on the surface of the substrate.

[0014] Preferably, in the above preparation method, after forming the upper superconducting layer, the preparation method further comprises:

[0015] 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 facing away from the substrate.

[0016] Preferably, in the above preparation method, the material of the lower superconducting layer is a combination of one or more of Al, Nb, NbN, NbTi, Nb3Sn, Nb3Al, and MgB2.

[0017] Preferably, in the above preparation method, the material of the barrier layer is a semiconductor material or an insulating material.

[0018] Preferably, in the above preparation method, the material of the barrier layer is Al2O3, SiN x 、Ta2O5、 NbSi x , a combination of one or more of MgO.

[0019] Preferably, in the above preparation method, the material of the upper superconducting layer is a combination of one or more of Al, Nb, NbN, NbTi, Nb3Sn, Nb3Al, and MgB2.

[0020] Preferably, in the above preparation method, the reactive gas used in the ion beam deposition process is a combination of one or more of O2, N2, and SiF4.

[0021] 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.

[0022] Preferably, in the above preparation method, the preparation method further comprises:

[0023] During the preparation of the Josephson junction thin film, the substrate is controlled to rotate with the center of the substrate as the axis.

[0024] Preferably, in the above preparation method, the rotation rate of the substrate is controlled to be 1 r / min-200 r / min.

[0025] 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 includes:

[0026] 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, thereby forming a lower superconducting layer with a specific lattice orientation on one side of the substrate.

[0027] 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 facing away from the substrate comprises:

[0028] The relative angles among the sputtering ion source, the third target and the substrate are adjusted to control the sputtering ion source to bombard the third target, thereby forming an upper superconducting layer with a specific lattice orientation on a side of the barrier layer facing away from the substrate.

[0029] 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 facing away from the substrate includes:

[0030] The sputtering ion source is controlled to bombard the second target material, the auxiliary ion source is controlled to generate a reaction ion beam, and the density of the reaction ion beam is regulated to form a barrier layer on a side of the lower superconducting layer away from the substrate.

[0031] Preferably, in the above preparation method, the preparation method further comprises:

[0032] The thicknesses of the lower superconducting layer, the barrier layer and the upper superconducting layer are detected by using a crystal oscillator.

[0033] Preferably, in the above preparation method, the ion beam in the ion beam deposition process is a neutral ion beam.

[0034] 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.

[0035] Preferably, in the above preparation method, the shape of the grid in the sputtering ion source is arc-shaped;

[0036] The radius of the arc is greater than or equal to 300 mm and less than or equal to 800 mm.

[0037] Preferably, in the above preparation method, the barrier layer is an oxide barrier layer, a nitride barrier layer, or a silicide barrier layer;

[0038] When the barrier layer is an oxide barrier layer, the oxygen content is 0.5-2;

[0039] When the barrier layer is a nitride barrier layer, the nitrogen content is 0.5-2;

[0040] When the barrier layer is a silicide barrier layer, the silicon content is 0.5-2.

[0041] 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.

[0042] The present application also provides a Josephson junction film, which is prepared based on any of the preparation methods described above, and includes:

[0043] substrate;

[0044] n stacked structures located on one side of the substrate, wherein the n stacked structures are stacked in sequence in a first direction, the first direction being perpendicular to the plane of the substrate and pointing from the substrate to the stacked structures, and n ≥ 2;

[0045] Wherein, the stacked structure comprises a lower superconducting layer, a barrier layer and an upper superconducting layer stacked in sequence in the first direction;

[0046] The Josephson junction film further comprises:

[0047] A passivation protection layer is located on a side of the nth stacked structure facing away from the substrate.

[0048] The present application also provides a semiconductor structure, which includes the above-mentioned Josephson junction thin film.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a method for preparing a Josephson junction thin film in situ in a single chamber based on an ion beam deposition process, comprising: controlling a sputtering ion source to bombard a first target material to form 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 an auxiliary ion source to generate a reactive ion beam to form a barrier layer on the side of the lower superconducting layer facing away from the substrate; and controlling the sputtering ion source to bombard a third target material to form an upper superconducting layer with a specific lattice orientation on the side of the barrier layer facing away from the substrate. The preparation of the Josephson junction thin film can be completed in the same chamber, reducing oxidation of the superconducting thin film during transmission. The operation is relatively simple, with fewer steps, and the production capacity is much higher than that of the existing multi-chamber linkage method. The prepared Josephson junction thin film is not damaged by plasma, has a preferred orientation, can better reduce resistance, and has good continuity and lower roughness of the barrier layer. Furthermore, the nitrogen, oxygen, or silicon content in the barrier layer can be precisely controlled, ultimately resulting in a Josephson junction with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0052] FIG1 is a schematic diagram of the structure of a superconducting Josephson junction;

[0053] FIG2 is a schematic diagram of the energy level distribution of the Josephson junction;

[0054] FIG3 is a schematic diagram of an ideal Josephson junction IV curve;

[0055] FIG4 is a schematic flow chart of a method for preparing a Josephson junction thin film according to an embodiment of the present invention;

[0056] FIG5 is a schematic diagram of a portion of the structure corresponding to the preparation method shown in FIG4 ;

[0057] FIG6 is a schematic diagram of ion beam deposition provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0059] Refer to Figure 1, which shows 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 barrier, allowing electrons to pass through the intermediate barrier. The current flowing between the superconductors in the absence of voltage is called the Josephson current, while the movement of electrons through the barrier is called Josephson tunneling. Two or more junctions connected by a superconducting path form a Josephson interferometer.

[0060] Refer to Figure 2, which shows a schematic diagram of the energy level distribution of a Josephson junction. The Josephson junction exhibits nonlinear circuit characteristics, with the lowest two energy levels, the ground state and the first excited state, typically serving as the quantum bit's |0> and |1> states, corresponding to 0 and 1 in a classical computer, thus forming a superconducting qubit. Furthermore, the superconducting Josephson junction exhibits negligible energy dissipation, making it an ideal basic building block. Using nonlinear superconducting Josephson junction LC circuits, quantum computer circuits can be quantized, enabling the observation and modulation of macroscopic quantum effects. Based on circuit quantization, the number of Cooper pairs tunneling in the Josephson junction can be altered by controlling the magnitude of the macroscopic current, thereby modulating the quantum states |0> and |1>. Signal storage and computation can then be achieved by varying the voltage signal.

[0061] Refer to Figure 3, which 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 be used to control the height of the potential barrier and the energy level spacing in the potential well. By further controlling the presence or absence of voltage across the Josephson junction, the macroscopic superconducting circuit can indirectly exhibit observable microscopic quantum properties. The IV characteristic curve of an ideal Josephson junction is shown in Figure 3. Based on this, the microscopic quantum states |0> and |1> can be modulated by adjusting the macroscopic bias current, enabling quantum computing.

[0062] While superconducting quantum computing possesses powerful capabilities, the fragility of superconducting junctions severely inhibits its performance. Decoherence time is considered the greatest obstacle to achieving quantum computing. Decoherence refers to the loss of quantum states due to interactions with the surrounding environment and devices. For example, thermal, electrical, and magnetic radiation, as well as material defects, cause the information stored in a quantum computer to decay. This ongoing interaction causes the quantum bit information to collapse into a classical state, impacting the performance of the quantum computer, including computing power, stability, and accuracy.

[0063] Prolonging the decoherence time is currently the most important issue in quantum computing. However, defects are introduced in every step of the process, including the structural design, material preparation, chip manufacturing, and operating environment of superconducting quantum circuits, deteriorating the coherence of superconducting quantum computing. From a microstructural perspective, much of this is attributed to material and surface interface issues. Impurities, oxidation, and defect energy levels can couple with the qubit, causing energy dissipation and phase decoherence in the qubit. This is particularly true in the barrier layer of the Josephson junction, where the electric and magnetic fields are concentrated in the vicinity of the junction. The coupling strength between these defect energy levels and the qubit is even greater, resulting in a direct impact on the coherence time of the qubit. Therefore, during the invention process of this application, it was discovered that comprehensively optimizing the Josephson junction process, especially the thin film deposition process, from both a material and process perspective is the most effective way to prolong the decoherence time and enhance quantum computing performance.

[0064] At present, 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, of which the etching and coating processes are the most critical. The main factors affecting the final coherence expression of the Josephson junction can be roughly divided into several categories:

[0065] 1. Cleanliness of the device core interface, such as

[0066] 1) There are a large number of impurities and defects in the Josephson junction barrier layer, the surface of the superconducting material, and the interface 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.

[0067] 2) Magnetic impurities and magnetic field noise caused by electron spin from surface dangling bonds, surface adsorbed hydrogen and oxygen small molecules, and oxide layer defects will also cause energy loss and decoherence.

[0068] 3) Dielectric loss caused by oxidation of superconducting materials suppresses decoherence time.

[0069] 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 loss and decoherence.

[0070] 3. The decoherence time of the superconducting lattice will also be severely suppressed due to plasma damage.

[0071] 4. Preparation of vacuum conditions. 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.

[0072] 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 first, 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.

[0073] 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.

[0074] 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, which 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.

[0075] 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.

[0076] Refer to Figure 4, which is a flow chart of a method for preparing a Josephson junction thin film provided in an embodiment of the present invention. Refer to Figure 5, which is a partial structural schematic diagram corresponding to the preparation method shown in Figure 4. Refer to Figure 6, which is a schematic diagram of an ion beam deposition provided in an embodiment of the present invention.

[0077] The method for preparing a Josephson junction thin film provided in an embodiment of the present application is based on an ion beam deposition process and is prepared in situ in a chamber, comprising:

[0078] S101: controlling the auxiliary ion source to perform a pre-cleaning process on the surface of the substrate 11.

[0079] 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.

[0080] It should be noted that step S101 can be performed as an optional step in the method for preparing the Josephson junction thin film, that is, step S101 is not a step that must be performed in the method for preparing the Josephson junction thin 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 thin film.

[0081] S102 : controlling a sputtering ion source to bombard a first target material, thereby forming a lower superconducting layer 13 with a specific lattice orientation on one side of the substrate 11 .

[0082] 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 a combination of one or more of Al, Nb, NbN, NbTi, Nb3Sn, Nb3Al, and MgB2. In other words, 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.

[0083] Furthermore, by regulating the relative angle between the sputtering ion source, the first target and the substrate 11 , the sputtering ion source is controlled to bombard the first target, thereby forming a lower superconducting layer 13 with a specific lattice orientation on one side of the substrate 11 .

[0084] That is, a sputtering ion source is controlled to bombard a first target material, which is a superconducting target material, to generate sputtered particles, which are deposited on one side of the substrate 11 to form a lower superconducting layer 13. During 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 be deposited, further reducing the resistance of the lower superconducting layer 13. In other words, the lower superconducting layer 13 has a preferred orientation. In general, angled ion beam deposition can be used to control the lattice orientation of the lower superconducting layer 13, forming a lower superconducting layer 13 with a specific lattice orientation, thereby producing a lower superconducting layer 13 with low resistivity and low heat generation and energy consumption.

[0085] 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 and move to a lower temperature, thereby reducing the operating temperature range of the superconducting junction.

[0086] 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 facing away from the substrate 11 .

[0087] 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 Al2O3, SiN x 、Ta2O5、NbSi x , MgO or one or more combinations thereof, in an 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.

[0088] Furthermore, the sputtering ion source is controlled to bombard the second target, 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 the side of the lower superconducting layer 13 facing away from the substrate 11 .

[0089] That is to say, the sputtering ion source bombards the target material, and at the same time 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.

[0090] 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 adjustable nitrogen / oxygen content allows for the preparation of barrier layers 14 with varying stoichiometric ratios. Alternatively, the nitrogen or oxygen content in the barrier layer 14 can be controlled by introducing nitrogen or oxygen through an auxiliary ion source and applying varying currents to the grid. In general, by controlling the density of the reactive ion beam from the auxiliary ion source, a continuously variable oxide or nitride barrier layer 14 can be prepared.

[0091] Similarly, ion beam deposition can prepare silicide barrier layers 14 with different silicon contents, such as NbSi xThe silicon content in the silicide barrier layer 14 is precisely controlled by ion beam deposition to a silicon content of 0.5-2. The silicon content in the barrier layer 14 can be optionally controlled by introducing SiF4 through an auxiliary ion source and applying different currents to the grid.

[0092] Furthermore, by regulating the ion beam deposition angle, energy and density, the uniformity of the barrier layer 14 can be precisely controlled. Better uniformity can improve the sample yield and reduce the cost of a single chip. By regulating 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.

[0093] 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).

[0094] 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 facing away from the substrate 11 .

[0095] 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 a combination of one or more of Al, Nb, NbN, NbTi, Nb3Sn, Nb3Al, and MgB2. In other words, 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, the contact between the upper superconducting layer 15 and the barrier layer 14 should be as low roughness as possible.

[0096] 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 facing away from the substrate 11 .

[0097] That is, the sputtering ion source is controlled to bombard the third target material, which is a superconducting target material, to generate sputtered particles, which are deposited on the side of the barrier layer 14 facing away from the substrate 11 to form the upper superconducting layer 15. During 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 be deposited, further reducing the resistance of the upper superconducting layer 15. In other words, the upper superconducting layer 15 has a preferred orientation. In general, angled ion beam deposition can be used to adjust the lattice orientation of the upper superconducting layer 15, forming an upper superconducting layer 15 with a specific lattice orientation, thereby producing an upper superconducting layer 15 with low resistivity and low heat generation and energy consumption.

[0098] 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 facing away from the substrate 11 .

[0099] 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.

[0100] It should be noted that steps S102 to S104 are the core and key steps in the embodiment of the present application. FIG4 only illustrates the overall logic of steps S101 to S105. In other words, the formation of the passivation protection layer 16 in step S105 can be performed as an optional step. That is, step S105 is not a required step in the preparation method of the Josephson junction thin film. It simply means that the passivation protection layer 16 is formed after the upper superconducting layer 15 is formed to protect the superconducting junction from contamination by oxygen and water vapor in the air.

[0101] It should be noted that, when depositing different film layers, the angle between the substrate 11 and the auxiliary ion source can be adjusted.

[0102] It should be noted that, based on actual needs, steps S102 to S104 can be cycled to deposit a stacked Josephson junction with a high storage density.

[0103] 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.

[0104] Optionally, in another embodiment of the present invention, the preparation method further comprises:

[0105] 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.

[0106] 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.

[0107] Optionally, in another embodiment of the present invention, the preparation method further comprises:

[0108] 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 using a crystal oscillator.

[0109] 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.

[0110] Optionally, in another embodiment of the present invention, the reactive gas used in the ion beam deposition process is a combination of one or more of O2, N2, and SiF4.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] Optionally, in another embodiment of the present invention, the ion beam of the ion beam deposition process is a neutral ion beam.

[0115] Specifically, in this embodiment, since film damage will deteriorate the decoherence time of the superconducting junction, a neutral ion beam is used to prepare damage-free superconducting films and barrier layers to better exert the performance of the superconducting junction.

[0116] The neutral ion beam of the sputtering ion source includes an ion beam formed by any one or more inert gases among He, Ne, Ar, Kr, and Xe.

[0117] 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 this embodiment of the present invention is less than or equal to 200 eV.

[0118] 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.

[0119] Optionally, in another embodiment of the present invention, the grid in the sputtering ion source is arc-shaped.

[0120] The radius of the arc is greater than or equal to 300 mm and less than or equal to 800 mm.

[0121] 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.

[0122] The following is a further description of the method for preparing the Josephson junction thin film provided by the embodiment of the present invention by means of three specific examples:

[0123] Specific embodiment one:

[0124] 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:

[0125] First, Ar is introduced into the auxiliary ion source to generate a neutral ion beam with a maximum energy angle of 45°-75° to remove oxides on the surface of the substrate 11.

[0126] 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.

[0127] Furthermore, the sputtering ion source is introduced with Ar to generate an ion beam to bombard the NbSi target. The NbSi particles sputtered out of 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 thin film and the gas of the auxiliary ion source are SiF4 and / or Ar.

[0128] 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 out of 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 push 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.

[0129] Finally, Ar 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 O2 and / or Ar.

[0130] Specific embodiment two:

[0131] 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 Al2O3. 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 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:

[0132] 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.

[0133] 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.

[0134] 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 a barrier layer 14 of the Al2O3 film. The gas of the auxiliary ion source is O2 and / or Kr.

[0135] 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.

[0136] 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 silicon oxide passivation protective layer 16. The gas of the auxiliary ion source is O2 and / or Kr.

[0137] Specific embodiment three:

[0138] 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 Al2O3. 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 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:

[0139] First, Xe is introduced into the auxiliary ion source to generate a neutral ion beam with a maximum energy angle of 45°-75° to remove oxides on the surface of the substrate 11.

[0140] Secondly, Xe 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 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°, and the gas of the auxiliary ion source is N2 and / or Xe.

[0141] Furthermore, Xe 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 NbN in the previous step under the reaction and promotion of the ion beam from the auxiliary ion source to form a barrier layer 14 of the Al2O3 film. The gas of the auxiliary ion source is O2 and / or Xe.

[0142] Furthermore, Xe is introduced into the sputtering ion source to generate an ion beam to bombard the upper superconducting layer Nb target. The Nb particles sputtered out of the target are deposited on the upper surface of the barrier layer 14 of the previous step under the push of the auxiliary ion source to form an 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°, and the gas of the auxiliary ion source is N2 and / or Xe.

[0143] Finally, Xe 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 O2 and / or Xe.

[0144] Based on the above embodiment of the present invention, another embodiment of the present invention further provides a Josephson junction film, which is prepared based on the preparation method described in the above embodiment. The Josephson junction film includes:

[0145] 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 structure, and n≥2.

[0146] The stacked structure includes a lower superconducting layer, a barrier layer, and an upper superconducting layer sequentially stacked in the first direction.

[0147] The Josephson junction film further includes a passivation protection layer located on a side of the nth stacked structure facing away from the substrate.

[0148] 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.

[0149] 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 thin film described in the above embodiment.

[0150] The above is a detailed introduction to a Josephson junction thin film, a preparation method thereof, and a semiconductor structure provided by the present invention. Specific examples are used herein 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 ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

[0151] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0152] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that the process, method, article, or apparatus comprising a series of elements inherent to the elements, or also including elements inherent to these processes, methods, articles, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0153] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily 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 is not limited to the embodiments shown herein but is intended to conform 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 angle between the sputtering ion source, the first target material and the substrate is 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 sequentially stacked 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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