CN111969100A - Josephson junction based on TaN and preparation method thereof - Google Patents

Josephson junction based on TaN and preparation method thereof Download PDF

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CN111969100A
CN111969100A CN202010871234.9A CN202010871234A CN111969100A CN 111969100 A CN111969100 A CN 111969100A CN 202010871234 A CN202010871234 A CN 202010871234A CN 111969100 A CN111969100 A CN 111969100A
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layer
tan
nbn
film
barrier layer
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CN111969100B (en
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张露
闫恺心
陈垒
王镇
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Shanghai Institute of Microsystem and Information Technology of CAS
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Shanghai Institute of Microsystem and Information Technology of CAS
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment
    • H10N60/0156—Manufacture or treatment of devices comprising Nb or an alloy of Nb with one or more of the elements of group 4, e.g. Ti, Zr, Hf
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment
    • H10N60/0241—Manufacture or treatment of devices comprising nitrides or carbonitrides
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment
    • H10N60/0912—Manufacture or treatment of Josephson-effect devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/10—Junction-based devices
    • H10N60/12—Josephson-effect devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/80—Constructional details
    • H10N60/805—Constructional details for Josephson-effect devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/80—Constructional details
    • H10N60/85—Superconducting active materials

Abstract

The invention provides a Josephson junction based on TaN and a preparation method thereof, wherein the preparation method comprises the following steps: providing a substrate, forming a NbN bottom layer film, a metal TaN barrier layer and a NbN top layer film, etching and defining a bottom electrode and a junction region, and forming an isolation layer and a wiring layer. According to the invention, the metal TaN barrier layer is formed through an ion nitriding process to obtain the SNS structure Josephson junction, the stability of the resistivity of the barrier layer can be improved, the parallel resistance is not needed, the problems of magnetic flux noise and integration degree of the SIS Josephson junction are solved, the process repeatability and stability are improved, the resistivity, the thickness and the like of the barrier layer material can be freely regulated and controlled through parameters such as ion nitriding time, power and the like, the formation of an insulating layer at an S/N interface is effectively avoided, the surface smoothness is high, and the surface smoothness is highGood nitridation uniformity and improved characteristic voltage I of SNS junctioncRnAnd the defect of high-frequency application of the device is limited, and the development of a high-quality NbN SNS Josephson junction is facilitated.

Description

Josephson junction based on TaN and preparation method thereof
Technical Field
The invention belongs to the field of superconducting electronics, and particularly relates to a Josephson junction based on TaN and a preparation method thereof.
Background
The pursuit of high performance computing systems has never ceased since the introduction of humans into the information age. After a semiconductor transistor-based digital circuit is rapidly developed for more than a half century, the integration level of the transistor is approaching to the physical limit size, Moore's law is about to fail, and digital computation encounters the bottleneck of energy consumption and speed. Superconducting Single Flux Quantum (SFQ) circuits utilize superconducting josephson junctions as switches to represent logical information by the presence or absence of a Single Flux Quantum in a superconducting loop. Compared with a high-low level coding mode of a traditional semiconductor CMOS circuit, the superconducting SFQ circuit has quantized signal precision, the clock frequency of a reconfigurable data path processor based on the SFQ circuit can reach 23GHz, and meanwhile, the power consumption is only 4.1 mW. Simple SFQ digital circuits fabricated using sub-micron josephson junction technology operate at frequencies up to 770 GHz. The advantages of the superconducting SFQ circuit in speed and power consumption enable the superconducting SFQ circuit to have wide application prospects in the fields of high-performance computers, voltage references, single-photon reading, high-precision analog-to-digital conversion and the like.
The most basic and central element of an SFQ circuit is the josephson junction. At present, the mainstream of an SFQ circuit in the world is formed based on a superconducting Nb material and an Nb/AlOx/Nb josephson junction with an additional parallel resistor, and this SIS (super/inductor/super) josephson junction has a high critical current density and a characteristic voltage that meet the application requirements of an RSFQ circuit (an SFQ circuit is also called an RSFQ (rapid Single Flux quantum) circuit), but due to the existence of the parallel resistor, the integration level of the SFQ circuit is structurally limited, and a parasitic inductor is generated, so that the performance of the device is reduced. SNS (super conductor/Normal metal/super conductor) Josephson junctions made of NbN superconducting materials have the advantages of high working temperature, large energy gap voltage, large characteristic voltage, wide critical current density regulation range and the like, so that the SNS junctions have the advantages of high speed and low energy consumption in superconducting high-frequency electronics application. On the other hand, the SNS structure can eliminate the parallel resistance, and the integration level of the SFQ circuit is improved structurally. Thus, a high characteristic voltage (I) is producedcRn) NbN is SNS (social networking service) offerThe sephson junction plays an important role in improving the performance of the SFQ circuit, so that the application of the RSFQ circuit in a plurality of leading edge fields can be expanded. Characteristic voltage (I) of SNS Josephson junctioncRn) The material property of the barrier layer and the interface characteristic of each film layer are strongly dependent, so that the selection of a proper barrier layer material and the preparation of a three-layer film with a clean interface are particularly important. However, the existing josephson junction with the SNS structure is difficult to realize free regulation and control of the physical properties of the barrier layer on the premise of ensuring the stability of the resistivity of the barrier layer, and the uniformity of the thin film in a large-size range is ensured, so that the preparation of the SNS josephson junction with high characteristic voltage is realized.
Therefore, how to provide a josephson junction based on TaN and a preparation method thereof are necessary to solve the above problems.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a josephson junction based on TaN and a method for manufacturing the same, which are used to solve the problems in the prior art that it is difficult to achieve free control of a barrier layer and to ensure uniformity of a thin film in a large size range to achieve SNS josephson junction with high characteristic voltage on the premise of ensuring stability of resistivity of the barrier layer.
To achieve the above and other related objects, the present invention provides a method for preparing a josephson junction based on TaN, comprising the steps of:
providing a substrate;
forming a functional structure material layer on the substrate, wherein the functional structure material layer comprises a NbN bottom layer film, a metal TaN barrier layer and a NbN top layer film which are formed from bottom to top, and the formation of the metal TaN barrier layer comprises the following steps: forming a Ta film on the surface of the NbN underlying film, and performing ion nitriding treatment on the Ta film to obtain the metal TaN barrier layer formed on the NbN underlying film based on the Ta film;
etching the functional structure material layer based on a first etching process to define a bottom electrode in the NbN bottom layer film;
etching the NbN top layer film and the metal TaN barrier layer on the bottom electrode based on a second etching process to define a plurality of junction regions, wherein the metal TaN barrier layer of the junction regions forms a junction barrier layer, and the NbN top layer film of the junction regions forms a top electrode;
forming an isolation layer on the exposed surfaces of the top electrode, the junction barrier layer and the bottom electrode and the substrate around the exposed surfaces, wherein a first connecting hole exposing the top electrode and a second connecting hole exposing the bottom electrode are formed in the isolation layer;
and forming a wiring layer on the isolation layer, wherein the wiring layer comprises a first wiring part electrically connected with the top electrode through the first connecting hole and a second wiring part electrically connected with the bottom electrode through the second connecting hole.
Optionally, the performing the ion nitriding treatment includes: and placing the substrate with the formed Ta film in a vacuum cavity, forming nitrogen-containing plasma based on the vacuum cavity, and bombarding the surface of the Ta film by adopting the nitrogen-containing plasma to finish the ion nitriding treatment, wherein a residual Ta film is arranged between the formed metal TaN barrier layer and the NbN bottom layer film.
Optionally, the metal TaN barrier layer resistivity and thickness are regulated by at least one of time and power of the ion nitridation process.
Optionally, the interface electron permeability coefficient of the josephson junction is adjusted based on the nitriding treatment, wherein the adjusting the interface electron permeability coefficient comprises: by the formula γ ═ psξs)/(ρnξn) Regulating and controlling the interface electron transmission coefficient, wherein gamma represents a ratio, rho represents resistivity, xi represents a coherence length,nrepresents a barrier layer of metal TaN,srepresenting the electrode layer.
Optionally, the critical current density and/or the characteristic voltage of the josephson junction is regulated based on the nitridation process, wherein the critical current density and/or the characteristic voltage of the josephson junction is regulated by formula Jc(d,T)＝Jc0exp(-d/ξn(T)) regulating the critical current density, d represents the thickness of the metal TaN barrier layer, T represents the temperature, Jc0Representative of the fact that,nrepresenting a barrier of metal TaNLayer, ξ represents the coherence length; by the formula Vc(d,T)＝Vc0(d/ξn(T))exp(-d/ξn(T)) regulating the characteristic voltage, d represents the thickness of the metal TaN barrier layer, T represents the temperature, Vc0Representative of the fact that,nrepresenting a metal TaN barrier layer and ξ representing the coherence length.
Optionally, in the process of forming the metal TaN barrier layer based on the nitridation treatment process, the metal TaN barrier layer is directly in contact with the NbN underlayer film or the residual Ta film, and an N element in the metal TaN barrier layer is formed on the surface of the material layer to shield the Nb element.
Optionally, the substrate comprises a single crystal magnesium oxide substrate, the thickness of the substrate being 0.4 mm; the thickness of the NbN underlayer film is between 150nm and 250 nm; the thickness of the metal TaN barrier layer is between 2nm and 8 nm; the thickness of the NbN top layer film is between 150nm and 250 nm; the shape of the junction region comprises a circle, the circle being directly between 1.6 μm-3 μm; the diameter of the first connection hole is between 1.2 μm and 2.6 μm; the diameter of the second connecting hole is between 1.2 and 2.6 mu m.
Optionally, simultaneously etching the NbN bottom layer film, the metal TaN barrier layer, and the NbN top layer film based on the first etching process; and simultaneously etching the NbN top layer film and the metal TaN barrier layer based on the second etching process.
Optionally, the first etching process includes step exposure and inductively coupled plasma etching; the second etching process comprises step exposure and inductively coupled plasma etching; the NbN underlayer film is prepared by a direct-current reactive magnetron sputtering method; the NbN top layer film is prepared by a direct-current reactive magnetron sputtering method; the wiring layer is prepared by a direct current reactive magnetron sputtering method.
The invention also provides a josephson junction based on TaN, the josephson junction is preferably prepared by the preparation method of the josephson junction, of course, other methods can be adopted for preparation, and the josephson junction based on TaN comprises the following steps:
a substrate;
the functional structure layer is formed on the substrate and comprises a bottom electrode, a junction barrier layer and a top electrode from bottom to top, wherein the junction barrier layer comprises a metal TaN layer, the bottom electrode comprises a bottom NbN layer, the top electrode comprises a top NbN layer, and the metal TaN layer is formed on the basis of an ion nitriding treatment process of a Ta film;
the isolation layer is formed on the exposed surfaces of the top electrode, the junction barrier layer and the bottom electrode and on the surrounding substrate, and a first connecting hole exposing the top electrode and a second connecting hole exposing the bottom electrode are formed in the isolation layer;
a wiring layer including a first wiring section electrically connected to the top electrode through the first connection hole and a second wiring section electrically connected to the bottom electrode through the second connection hole.
Optionally, the substrate comprises a single crystal magnesium oxide substrate, the thickness of the substrate being 0.4 mm; the thickness of the NbN underlayer film is between 150nm and 250 nm; the thickness of the metal TaN barrier layer is between 2nm and 8 nm; the thickness of the NbN top layer film is between 150nm and 250 nm; the shape of the junction region comprises a circle, the circle being directly between 1.6 μm-3 μm; the diameter of the first connection hole is between 1.2 μm and 2.6 μm; the diameter of the second connecting hole is between 1.2 and 2.6 mu m.
Optionally, the lower surface of the metal TaN layer is directly contacted with the bottom NbN layer or the residual Ta film; the upper surface of the metal TaN layer is directly contacted with the top NbN layer, and the N element in the metal TaN layer is formed on the surface of the material layer and shields the Nb element.
As described above, according to the Josephson junction based on TaN and the preparation method thereof, the metal TaN barrier layer is formed through the ion nitriding process to be used as the barrier layer of the Josephson junction, the stability of the resistivity of the barrier layer is improved, the SNS structure Josephson junction is prepared without parallel resistors, the problems of magnetic flux noise and integration level of the SIS structure Josephson junction are solved, the problems of poor process repeatability and stability are improved, in addition, the free regulation and control of the barrier layer can be realized through the ion nitriding process, and the electric resistance of the material of the barrier layer is reducedThe resistivity, the thickness and the like can be freely regulated and controlled through parameters such as plasma nitridation time, power and the like, the formation of an insulating layer at an S/N interface is effectively avoided, the characteristics of high surface flatness, good nitridation uniformity and the like are achieved, and the characteristic voltage I of an SNS junction is improvedcRnThe defect of high-frequency application of the device is limited due to the small size, and the research and development of high-quality NbN SNS Josephson junctions are facilitated. Under the premise of ensuring the stability of the resistivity of the TaN barrier layer, the invention can realize the free regulation and control of the physical property of the TaN film and simultaneously ensure the uniformity of the film in a large-size range, thereby becoming a high-characteristic-voltage SNS Josephson junction.
Drawings
Fig. 1 shows a flow chart of an exemplary process for fabricating a TaN-based josephson junction according to the present invention.
Fig. 2 shows a schematic diagram of a structure for providing a substrate in the fabrication of a TaN-based josephson junction according to an example of the present invention.
Fig. 3 is a schematic view showing the formation of a NbN underlayer film in the fabrication of a TaN-based josephson junction according to an example of the present invention.
Fig. 4 is a schematic structural diagram illustrating the formation of a Ta film in the fabrication of a TaN-based josephson junction according to an embodiment of the present invention.
Fig. 5 shows a schematic representation of the formation of a metal TaN barrier layer in the fabrication of a TaN-based josephson junction in accordance with an example of the present invention.
Fig. 6 is a schematic diagram illustrating the formation of a NbN top layer film in the fabrication of a TaN-based josephson junction in accordance with an embodiment of the present invention.
Fig. 7 is a schematic diagram illustrating the definition of a bottom electrode in the fabrication of a TaN-based josephson junction according to an exemplary embodiment of the present invention.
Fig. 8 is a schematic diagram illustrating the junction regions defined in the fabrication of a TaN-based josephson junction according to an exemplary embodiment of the present invention.
Fig. 9 is a schematic diagram illustrating the formation of a spacer layer in the fabrication of a TaN-based josephson junction according to an embodiment of the present invention.
Fig. 10 is a schematic diagram illustrating the formation of a wiring layer in the fabrication of a TaN-based josephson junction according to an exemplary embodiment of the present invention.
FIG. 11 shows a typical I-V curve for an SIS junction.
FIG. 12 shows a typical I-V curve for an SNS junction.
Description of the element reference numerals
101 substrate
102 NbN underlayer film
Film of 103 Ta
104 metal TaN barrier layer
105 residual Ta film
106 NbN top layer film
107 bottom electrode
108 remaining Ta film etch layer
109 junction barrier layer
110 top electrode
111 barrier layer
111a first connection hole
111b second connection hole
112 wiring layer
112a first wiring portion
112b second wiring portion
S1-S6
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. "between … …" means that two endpoint values are included.
In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.
It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed freely, and the layout of the components may be more complicated.
As shown in fig. 1, the present invention provides a method for preparing a josephson junction based on TaN, comprising the steps of:
s1, providing a substrate;
s2, forming a functional structure material layer on the substrate, wherein the functional structure material layer includes a NbN bottom layer film, a metal TaN barrier layer and a NbN top layer film formed from bottom to top, and the formation of the metal TaN barrier layer includes: forming a Ta film on the surface of the NbN underlying film, and performing ion nitriding treatment on the Ta film to obtain the metal TaN barrier layer formed on the NbN underlying film based on the Ta film;
s3, etching the functional structure material layer based on a first etching process to define a bottom electrode in the NbN bottom layer film;
s4, etching the NbN top layer film and the metal TaN barrier layer on the bottom electrode based on a second etching process to define a plurality of junction regions, wherein the metal TaN barrier layer of the junction regions forms a junction barrier layer, and the NbN top layer film of the junction regions forms a top electrode;
s5, forming isolation layers on the exposed surfaces of the top electrode, the junction barrier layer and the bottom electrode and the substrate around the top electrode, wherein the isolation layers are formed with a first connection hole exposing the top electrode and a second connection hole exposing the bottom electrode;
s6, forming a wiring layer on the isolation layer, the wiring layer including a first wiring portion electrically connected to the top electrode through the first connection hole and a second wiring portion electrically connected to the bottom electrode through the second connection hole.
The method for preparing TbN-based josephson junctions according to the present invention will be described in detail with reference to the accompanying drawings, wherein it should be noted that the above sequence does not strictly represent the preparation sequence of the TbN-based josephson junctions protected by the present invention, and those skilled in the art may change according to the actual process steps, and fig. 1 shows only one exemplary TbN-based josephson junction preparation step, and those skilled in the art may change the design according to the conventional choice in the art.
First, as shown in S1 in fig. 1 and fig. 2, step S1 is performed to provide the substrate 101. The substrate 101 may be a single material layer or a stacked structure composed of multiple material layers. In an example, the substrate 101 is selected to be magnesium oxide (MgO), and may be a single crystal magnesium oxide substrate, and is further preferably a single crystal magnesium oxide substrate in a (100) direction, and of course, may be selected to be other common substrates that can achieve the functions of the present invention. The thickness of the substrate 101 is 0.4mm to suit the requirements of the stepper apparatus.
Next, as shown in S2 of fig. 1 and fig. 3-6, step S2 is performed to form a functional structure material layer on the substrate 101, wherein the functional structure material layer includes a NbN bottom layer film 102, a metal TaN barrier layer 104, and a NbN top layer film 106 formed from bottom to top, and the formation of the metal TaN barrier layer 104 includes: as shown in fig. 4, a Ta film 103 is formed on the surface of the NbN underlayer film 102, and the Ta film 103 is subjected to ion nitridation to obtain the metal TaN barrier layer 104 formed on the NbN underlayer film 102 on the basis of the Ta film 103, wherein the barrier layer is a TaN film having a film stoichiometry deviating from 1:1 and exhibiting normal metal behavior at low temperature. For example, it may be a TaNx film having a N/Ta stoichiometric ratio of less than 0.5, optionally 0.2 or 0.3, a body centered cubic or hexagonal structure, and exhibiting normal metallic behavior at low temperatures. In addition, the thickness ratio of the formed metal TaN layer to the Ta layer can depend on the nitridation power and the nitridation time. In one example, the Ta film is not completely consumed, and a remaining Ta film 105 is also formed between the NbN underlayer film 102 and the metal TaN barrier layer 104. Specifically, in this step, the metal TaN barrier layer 104 is formed on the basis of an ion nitridation process, and is used as a barrier layer of a josephson junction by a subsequent process.
Wherein, before the ion nitriding treatment, the method comprises the following steps: the substrate on which the NbN underlayer film 102 is formed is placed in a vacuum chamber and a nitrogen-containing plasma is formed based on the vacuum chamber, that is, a nitrogen-containing plasma such as N formed by high-voltage discharge in the vacuum chamber2 +、N+、N2 2+And ions, wherein the nitrogen-containing plasma is adopted to bombard the surface of the Ta film 103 so as to perform the ion nitriding treatment process. In one example, the Ta film 103 is ion nitrided in situ. For example, the NbN underlayer film 102 and the Ta film 103 are grown by a direct current reactive magnetron sputtering method, and then the ion nitridation process is performed in the same chamber to realize in-situ ion nitridation, and based on the same process chamber, the N source of the NbN underlayer film 102 and the N source for forming the metal TaN barrier layer can be continuously introduced, and the two sources are integrated in the same process program (recipe), thereby simplifying the process and improving the film quality.
By subjecting the Ta film toAfter the above-described particle nitriding treatment, the Ta film 102 is either entirely converted into a metal TaN barrier layer 104 or partially converted into a metal TaN barrier layer 104 by the action of a nitrogen-containing plasma, and the remaining Ta film 103 is left. During this treatment, N is present in the plasma2 +、N+And N2 2+Ions bombard the surface of a sample at a certain speed to effectively remove a surface oxide layer, and the sample is surrounded by nitrogen and ionized nitrogen plasma when an ion nitriding process is carried out, so that the bottom layer is effectively prevented from being oxidized, namely, an insulating layer is prevented from being formed between a metal barrier layer formed subsequently and a bottom electrode, namely, the ion nitriding technology effectively prevents the formation of the insulating layer at the interface of S (the NbN bottom layer film 102)/N (the metal TaN barrier layer 104), prevents a superconductor-insulator-normal metal-insulator-superconductor (SINIS) junction from being formed, and avoids J (NcToo low and poor process stability. The metal NbNx barrier layer 103 formed by the nitridation processing can form a high-flatness NbNx barrier layer and has the advantage of good uniformity. The high flatness and the ultrahigh uniformity of the ion nitriding technology overcome the difficult problems of poor interface diffusion and uniformity of the conventional three-layer film, and are beneficial to the research and development of high-quality NbN SNS Josephson junctions. The TaN film grown by the direct-current reactive magnetron sputtering has the film thickness uniformity of about 5% in a range of 4inch, the film thickness uniformity is poorer than that of ion nitridation in a large-area range, and the junction matrix uniformity has challenges; when a TaN barrier layer is grown by magnetron sputtering, the TaN is positioned in a superconducting-insulator phase transition region, the process window is small, and the process is stable and crossed; the ion nitriding technology effectively prevents the formation of an insulating layer at an S/N interface, and has high nitriding uniformity and good process stability. But due to industry barriers, ion nitriding has not been developed for use in the field.
By way of example, the metal TaN barrier layer 104 may have a thickness of between 2nm and 8nm, and may be, for example, 4nm, 5nm, or 6 nm.
As an example, the metal TaN barrier layer 104 resistivity and thickness are modulated by at least one of time and power of the ion nitridation process. Thus, a free control of the metal TaN barrier layer 104 is achieved, for example, the resistivity and thickness of the metal TaN barrier layer 104 can be freely controlled according to the parameters of the nitridation process. Thereby preparing a high-quality over-damped SNS Josephson junction with a non-hysteresis I-V curve. The SNS Josephson junction with high uniformity and high characteristic voltage can be prepared on the premise of ensuring the resistivity stability of the TaN barrier layer by adjusting the parameters of the ion nitriding technology to realize the free regulation and control of the physical properties of the TaN and the accurate control of the stoichiometric ratio and the thickness of the TaN barrier layer.
As an example, the interface electron permeability coefficient of the josephson junction is controlled based on the nitridation process, wherein the manner of controlling the interface electron permeability coefficient includes: by the formula γ ═ psξs)/(ρnξn) Controlling and controlling the interface electron transmission coefficient, wherein gamma represents a ratio, rho represents resistivity, xi represents a coherence length,nrepresents a barrier layer of metal TaN,sthe electrode layer may represent a top electrode or a bottom electrode. The SNS Josephson junction realizes electron transfer by Andrew reflection, junction performance is related to the resistivity of the barrier layer material and S/N interface characteristics, and the interface electron transmission coefficient depends on the ratio gamma (rho) of the resistivity of the superconducting material and the barrier layer material multiplied by the coherence lengthsξs)/(ρnξn). The method is used for researching barrier layer material parameters, such as the film resistivity and the change trend of the S/N interface electron transmission coefficient when the film thickness changes, and quantitatively disclosing the rule between performance parameters such as the characteristic voltage and the critical current density of the SNS junction and the macroscopic parameters of the barrier layer material.
As an example, the critical current density of a josephson junction is regulated based on the nitridation process, wherein the critical current density is regulated by formula Jc(d,T)＝Jc0exp(-d/ξn(T)) regulating the critical current density, d represents the thickness of the metal TaN barrier layer, T represents the temperature, Jc0Representative of the fact that,nrepresenting a metal TaN barrier layer and ξ representing the coherence length. Thereby realizing the free regulation and control of the critical current density of the Josephson junction. In another example, a characteristic voltage of a josephson junction is modulated based on the nitridation process, by formula Vc(d,T)＝Vc0(d/ξn(T))exp(-d/ξn(T)) regulating the characteristic voltage, d represents the thickness of the metal TaN barrier layer, T represents the temperature, Vc0Representative of the fact that,nrepresenting a metal TaN barrier layer and ξ representing the coherence length. Thereby realizing the free regulation and control of the characteristic voltage of the Josephson junction.
As an example, a NbN underlayer film 102 is formed on the substrate 101. The NbN underlayer film 102 is formed on the entire surface of the substrate 101, in one example, the NbN underlayer film 102, which is an underlying superconducting material, is grown by a dc reactive magnetron sputtering method, and optionally, the thickness of the NbN underlayer film 102 is between 150nm and 250nm, and may be 180nm, 200nm, or 220 nm. NbN means having a high superconducting transition temperature (T)c16.5K), large superconducting energy gap (delta-3 meV) and high characteristic frequency (1.4 THz). The NbN underlayer film 102 is used as a structural basis for preparing a metal TaN barrier layer on one hand, and is used for subsequently manufacturing a Josephson junction bottom electrode on the other hand.
In one example, the NbN top layer film 106, the underlying superconducting material, is grown by a dc reactive magnetron sputtering method, and optionally, the NbN top layer film 106 has a thickness of 150nm to 250nm, which may be 180nm, 200nm, or 220 nm.
As an example, in the process of forming the metal TaN barrier layer based on the nitridation process, the metal TaN barrier layer is directly in contact with the NbN underlayer film or the residual Ta film, and an N element in the metal TaN barrier layer is formed on the surface of the material layer to shield the Ta element.
The TaN material layer formed in the invention is used as a barrier layer, and the materials of the bottom electrode and the top electrode adopted in the invention are combined, so that the barrier layer has the following advantages: the stoichiometric ratio of the TaN film is controllable, and TaN barrier layers with different electrical characteristics can be manufactured; TaN and NbN are nitrides, and a clean interface can be obtained when the three-layer film is prepared; the etching process of the TaN material is similar to that of the NbN material, the process flow is simplified, and the uniformity of the etched side wall is good; TaN is matched with NbN on a lattice structure, has good chemical and thermal stability, and is beneficial to the epitaxial growth of a high-quality NbN/TaN/NbN three-layer film.
In addition, the invention adopts the ion nitriding treatment mode to formThe metallic TaN barrier layer produces remarkable effects, wherein in other examples, the resistivity of the TaN film deposited by adopting a pulse laser method is small and is only a few m omega cm, and the characteristic voltage of the prepared NbN/TaN/NbN SNS junction is relatively low and is only 0.34 mV. The TaN film grown by the magnetron sputtering method has a resistivity of 13m omega cm at 4.2K, and the SNS junction I prepared by the NbN/TaN/NbN three-layer film grown at high temperaturecRnThe value reached 0.78 mV. Growing NbN/TaN/NbN three-layer film in situ by direct current magnetron sputtering method, wherein the temperature is changed from room temperature to 300 ℃ when TaN is grown, so that the TaN film is controlled in a superconducting-insulating transition region, and obtaining I at 4.2K working temperature by SNOP processcRnSNS junctions with a value of 3.74mV, JcIs 14.5kA/cm2I at 10K operating temperaturecRnValue of 0.3mV, JcIs 10kA/cm2. The chemical stoichiometric ratio of the TaN barrier layer is regulated and controlled by adopting a magnetron sputtering mode, and the preparation of the high characteristic voltage SNS Josephson junction can be realized by growing the NbN/TaN/NbN three-layer film in situ. However, the TaN barrier layer corresponding to the high characteristic voltage SNS junction is in the superconducting-insulator phase transition region, and the small change of sputtering parameters in the deposition process of the TaN barrier layer can cause great fluctuation of the resistivity of the TaN barrier layer, so that the inter-wafer repeatability of the SNS junction is poor. In addition, the TaN film prepared by the magnetron sputtering method has poor uniformity in a large-size range, and is not beneficial to the development of large-scale superconducting integrated circuits. The resistivity of the TaN film can be adjusted from 1 to 10 by adopting the ion nitriding technology6The characteristic voltage regulating range is 0.1-5mV, the uniformity of ion nitriding is high, the process stability is good, and the uniformity and the inter-chip repeatability of the barrier layer in a large area range are guaranteed. Next, as shown in S3 of fig. 1 and fig. 6, step S3 is performed to etch the functional structure material layer based on a first etching process to define a bottom electrode 107 in the NbN bottom layer film 102. As an example, the NbN bottom layer film 102, the metal TaN barrier layer 104, and the NbN top layer film 106 are simultaneously etched based on the first etching process to obtain the bottom electrode 107, where the NbN bottom layer film 102, the metal TaN barrier layer 104, and the NbN top layer film 106 have the same constituent elements, and the TaN thin film has the same constituent elements as each otherThe etching process is similar to that of the superconducting electrode NbN, the etching can be completed in one step, the etching uniformity of the side wall is good, and the etching steepness of a junction area is guaranteed. As an example, the first etch process includes step exposure and inductively coupled plasma etching. The etching gas may be CF4 and Ar.
Next, as shown in S4 of fig. 1 and fig. 7, step S4 is performed to etch the NbN top layer 106 and the metal TaN barrier layer 104 on the bottom electrode 107 based on a second etching process to define a plurality of junction regions, wherein the metal TaN barrier layer 104 of the junction regions forms a junction barrier layer 108, the NbN top layer 106 of the junction regions forms a top electrode 110, and when a residual Ta film 105 exists, a residual Ta film etching layer 109 is further formed in this step. As an example, the NbN underlayer film 105 and the metal TaN barrier layer 104 are simultaneously etched based on the second etching process to form respective josephson junctions, where the NbN underlayer film 105 and the metal TaN barrier layer 104 have the same constituent elements, and TaN and NbN can etch a multilayer film to the bottom in one step under the same etching parameters, thereby simplifying the etching step and simultaneously ensuring the etching steepness, effectively avoiding the uneven distribution of the size of the junction regions in the vertical direction, and ensuring the etching steepness of the junction regions. As an example, the second etching process includes step exposure and inductively coupled plasma etching.
As an example, the shape of the junction region comprises a circle, which is directly between 1.6 μm-3 μm, e.g. may be 1.8 μm, 2 μm, 2.5 μm. Therefore, the appropriate critical current density can be obtained, and the high-frequency application of the device is facilitated. Of course, in other examples, the shape of the junction region may also be made into a square junction. The obtained SNS junction is a Josephson junction with a current-voltage curve which is a non-hysteresis curve, and the junction performance is related to the resistivity of the material of the barrier layer and the S/N interface characteristic. The NbN has high superconductive transition temperature (T)c16.5K), large superconducting energy gap (delta-3 meV) and high characteristic frequency (1.4 THz).
Next, as shown in S5 of fig. 1 and fig. 8, step S5 is performed to form an isolation layer 111 on the exposed surfaces of the top electrode 110, the junction barrier layer 109, and the bottom electrode 106 and the surrounding substrate 101, wherein the isolation layer 111 has a first connection hole 111a exposing the top electrode 110 and a second connection hole 111b exposing the bottom electrode 107.
As an example, the diameter of the first connection hole is between 1.2 μm-2.6 μm, e.g. may be 1.5 μm, 2 μm, 2.2 μm; the diameter of the second connection hole is between 1.2 μm and 2.6 μm, for example, 1.5 μm, 2 μm, 2.2 μm. The positions and the number of the first connection holes 111a and the second connection holes 111b can be set according to actual requirements, so as to electrically lead out the top electrode 110 and the bottom electrode 107 subsequently.
In an example, after forming the junction region, an isolation material layer covering the entire surface may be deposited on the substrate 101, and the isolation material layer may be etched by a photolithography process to obtain the first connection hole and the second connection hole, for example, an opening process is performed by using step exposure and reactive ion etching, and SiO uncovered by the photoresist is etched by using the reactive ion etching2And a thin film forming a connection hole connecting the upper film and the wiring layer. The isolation layer 111 is prepared by a chemical vapor deposition method, and the material thereof includes, but is not limited to, a silicon dioxide thin film, and the deposition thickness thereof may be between 180nm and 300nm, such as 200nm, 220nm, and 250nm, which are selected according to the actual device layout.
Finally, as shown in S6 of fig. 1 and fig. 9, step S6 is performed to form a wiring layer 112 on the isolation layer 111, wherein the wiring layer 112 includes a first wiring portion 112a electrically connected to the top electrode 110 through the first connection hole 111a and a second wiring portion 112b electrically connected to the bottom electrode 107 through the second connection hole 111 b.
In one example, the wiring layer 112 is grown by a DC reactive magnetron sputtering method, and the material includes but is not limited to NbN, and the deposition thickness can be between 300nm-400nm, such as 350nm, 380nm, and is selected according to the actual device layout. In an example, after the isolation layer is formed, a wiring material layer covering the entire device surface is formed on the isolation layer, and then the wiring material layer is etched through a photolithography etching process to obtain the wiring layer. Optionally, the wiring layer is prepared by step exposure and inductively coupled plasma etching.
The invention prepares the SNS structure Josephson junction of the freely-regulated barrier layer based on a nitridation process. Josephson junctions are weakly connected superconductors prepared according to the josephson effect. When a superconducting-insulating-superconducting (SIS) structure is formed by a thin film insulating layer between two superconductors, a superconducting tunnel current I with zero voltage related to the phase difference theta of electron wave-pair functions in the superconductors appearss(Is＝Icsin θ) in which IcIs the critical current of the josephson junction. If a voltage difference V exists between the superconductors, the phase difference theta changes with time
Figure BDA0002651187350000111
At this time IsWill be of amplitude IcAnd f is 2 eV/h. The actual josephson junction can be considered as an ideal josephson junction with a parallel resistor R and a capacitor C, the electrical behavior of which can be explained with the RCSJ model. The parallel network has two characteristic times RC and LJ/R, introduction of a damping parameter betac＝RC/(LJ/R)＝2πIcR2C/Φ0: when beta iscWhen the damping coefficient is more than 1, the junction is under-damped, and the I-V curve has hysteresis; when beta iscWhen the value is less than 1, the knot is over-damped, and the I-V curve is a single-value curve. SIS Josephson junctions are usually underdamped junctions and require the addition of a shunt resistor to make the junction betacLess than 1, however, the parallel resistance not only increases the flux noise but also limits the integration of the superconducting circuit. On the other hand, increasing the circuit clock frequency requires thinner barrier layers and smaller junction areas, but when the barrier layer thickness is very thin (d-1 nm) or the junction size is in the submicron range, the process repeatability and stability of the josephson junction are both severely challenging. FIG. 10 is a typical I-V curve for an SIS junction.
Prepared by the inventionThe SNS junction is formed, the nitrogen content is regulated and controlled through an ion nitriding technology, a normal metal TaN barrier layer is formed, and the resistivity, the thickness and the like of the barrier layer material can be freely regulated and controlled through parameters such as ion nitriding time, power and the like. The ion nitriding mode not only effectively avoids the formation of an insulating layer at an S/N interface, but also has the characteristics of high surface flatness, good nitriding uniformity and the like, and is beneficial to the research and development of high-quality NbN SNS Josephson junctions. The Cooper pair in a superconductor-normal metal-superconductor (SNS) junction realizes the coupling of superconductivity on two sides in the form of Andrew reflection at an S/N interface and has a non-hysteresis I-V curve. The SNS junction is the junction of the intrinsic shunt resistor, so that the area required by an external shunt resistor is effectively saved. In addition, SNS junctions have a high transmission of electrons at the S/N interface and have a high J comparable to that of SIS junctions when the N layer is relatively thick (d 10nm)cAnd the repeatability and stability of the process are ensured. However, the characteristic voltage I of SNS junctions compared to SIS junctionscRnSmall, limiting the high frequency applications of the device. Research shows that the characteristic voltage of the SNS junction is closely related to the material characteristics of the barrier layer and the S/N interface characteristics. The scheme of the invention can ensure the clarity of the interface of the SNS Josephson junction while freely regulating and controlling the barrier layer. FIG. 11 is a typical I-V curve for an SNS junction. In addition, compared with the current mainstream Josephson junction, the invention has obvious effect, the current mainstream of the NbN Josephson junction is NbN/AlN/NbN junction, the leakage current is small, and the energy gap voltage is large (the>5mV)，JcIn the range of several tens to several thousands A/cm2The range varies. AlN can realize the transformation from an insulating state to a normal state through a stoichiometric control ratio, however, AlN shows a piezoelectric effect due to the enhanced quantum-phonon coupling effect, and the crystal structure of the AlN thin film needs to be accurately controlled to inhibit the influence of the piezoelectric effect on the performance of the Josephson junction, so AlN is not the best selection scheme of the SNS Josephson barrier layer in NbN system.
In addition, as shown in fig. 10 and referring to fig. 1 to 9, the present invention also provides a josephson junction based on TaN, which is preferably prepared by the method for preparing a josephson junction of the present invention, and of course, may be prepared by other methods, and the josephson junction based on TaN includes:
a substrate 101;
a functional structure layer formed on the substrate, the functional structure layer including, from bottom to top, a bottom electrode 107, a junction barrier layer 109, and a top electrode 110, wherein the junction barrier layer 109 includes a metal TaN layer (corresponding to the metal TaN barrier layer in the description of the preparation method), the bottom electrode 107 includes a bottom NbN layer (corresponding to the NbN bottom layer film in the description of the preparation method), the top electrode 110 includes a top NbN layer (corresponding to the NbN top layer film in the description of the preparation method), and the metal TaN layer is formed based on an ion nitriding treatment process performed on a Ta film; here, part of the names in the structures are different from those described in the manufacturing method due to the manufacturing process, and it can be understood by those skilled in the art based on the manufacturing process and general knowledge herein that the scope of the present invention should not be excessively limited.
An isolation layer 111 formed on the exposed surfaces of the top electrode 110, the junction barrier layer 109, and the bottom electrode 107 and the surrounding substrate 101, wherein a first connection hole 111a exposing the top electrode and a second connection hole 111b exposing the bottom electrode are formed in the isolation layer 111;
a wiring layer 112 including a first wiring section 112a electrically connected to the top electrode 110 through the first connection hole 111a and a second wiring section 112b electrically connected to the bottom electrode 107 through the second connection hole 111 b.
As an example, the substrate 101 comprises a single crystal magnesium oxide substrate, the thickness of the substrate 101 being between 0.2mm-0.6 mm; the thickness of the NbN underlayer film 102 is between 150nm and 250 nm; the thickness of the metal TaN barrier layer 104 is between 2nm and 8 nm; the thickness of the NbN top layer film 106 is between 150nm and 250 nm; the shape of the junction region comprises a circle, the circle being directly between 1.6 μm-3 μm; the diameter of the first connection hole 111a is between 1.2 μm and 2.6 μm; the diameter of the second connection hole 111b is between 1.2 μm and 2.6 μm.
As an example, the lower surface of the metal TaN layer is directly in contact with the bottom NbN layer or the remaining Ta film; the upper surface of the metal TaN layer is directly contacted with the top NbN layer, and the N element in the metal TaN layer is formed on the surface of the material layer and shields the Nb element.
In conclusion, the Josephson junction based on TaN and the preparation method thereof form the metal TaN barrier layer as the barrier layer of the Josephson junction by the ion nitriding process, improve the stability of the resistivity of the barrier layer, prepare the SNS structure Josephson junction without parallel resistors, solve the problems of magnetic flux noise and integration level of the SIS structure Josephson junction, improve the problems of poor process repeatability and stability, in addition, the free regulation and control of the barrier layer can be realized through the ion nitriding process, the resistivity, the thickness and the like of the material of the barrier layer can be freely regulated and controlled through parameters such as the ion nitriding time, the power and the like, the formation of an insulating layer at an S/N interface is effectively avoided, meanwhile, the method has the characteristics of high surface flatness, good nitridation uniformity and the like, improves the defect that the characteristic voltage IcRn of the SNS junction is very small, limits the high-frequency application of a device, and is beneficial to the research and development of high-quality NbN SNS Josephson junctions. Under the premise of ensuring the stability of the resistivity of the TaN barrier layer, the invention can realize the free regulation and control of the physical property of the TaN film and simultaneously ensure the uniformity of the film in a large-size range, thereby becoming a high-characteristic-voltage SNS Josephson junction. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (12)

1. A preparation method of a Josephson junction based on TaN is characterized by comprising the following steps:
providing a substrate;
forming a functional structure material layer on the substrate, wherein the functional structure material layer comprises a NbN bottom layer film, a metal TaN barrier layer and a NbN top layer film which are formed from bottom to top, and the formation of the metal TaN barrier layer comprises the following steps: forming a Ta film on the surface of the NbN underlying film, and performing ion nitriding treatment on the Ta film to obtain the metal TaN barrier layer formed on the NbN underlying film based on the Ta film;
etching the functional structure material layer based on a first etching process to define a bottom electrode in the NbN bottom layer film;
etching the NbN top layer film and the metal TaN barrier layer on the bottom electrode based on a second etching process to define a plurality of junction regions, wherein the metal TaN barrier layer of the junction regions forms a junction barrier layer, and the NbN top layer film of the junction regions forms a top electrode;
forming an isolation layer on the exposed surfaces of the top electrode, the junction barrier layer and the bottom electrode and the substrate around the exposed surfaces, wherein a first connecting hole exposing the top electrode and a second connecting hole exposing the bottom electrode are formed in the isolation layer;
and forming a wiring layer on the isolation layer, wherein the wiring layer comprises a first wiring part electrically connected with the top electrode through the first connecting hole and a second wiring part electrically connected with the bottom electrode through the second connecting hole.
2. The method of preparing a josephson junction based on TaN of claim 1, wherein the performing of the ion nitridation process comprises: and placing the substrate with the formed Ta film in a vacuum cavity, forming nitrogen-containing plasma based on the vacuum cavity, and bombarding the surface of the Ta film by adopting the nitrogen-containing plasma to finish the ion nitriding treatment, wherein a residual Ta film is arranged between the formed metal TaN barrier layer and the NbN bottom layer film.
3. The method of fabricating josephson junctions based on TaN of claim 1, wherein the metal TaN barrier layer resistivity and thickness are tailored by at least one of time and power of the ion nitridation process.
4. The method of preparing a josephson junction based on TaN of claim 3, wherein the interface electron transmission coefficient of the josephson junction is controlled based on the nitridation process, wherein the interface electron transmission coefficient is controlled by a method comprising: by the formula γ ═ psξs)/(ρnξn) Regulating and controlling the interface electron transmission coefficient, wherein gamma represents a ratio, rho represents resistivity, xi represents a coherence length,nrepresents a barrier layer of metal TaN,srepresenting the electrode layer.
5. Method for preparing Josephson junctions based on TaN according to claim 3, characterized in that the critical current density and/or the characteristic voltage of the Josephson junction is modulated on the basis of the nitriding treatment, wherein the critical current density and/or the characteristic voltage of the Josephson junction is determined by formula Jc(d,T)＝Jc0exp(-d/ξn(T)) regulating the critical current density, d represents the thickness of the metal TaN barrier layer, T represents the temperature, Jc0Representative of the fact that,nrepresents a metal TaN barrier layer, and xi represents a coherence length; by the formula Vc(d,T)＝Vc0(d/ξn(T))exp(-d/ξn(T)) regulating the characteristic voltage, d represents the thickness of the metal TaN barrier layer, T represents the temperature, Vc0Representative of the fact that,nrepresenting a metal TaN barrier layer and ξ representing the coherence length.
6. The method of fabricating a Josephson junction based on TaN according to claim 1, wherein during the formation of the metal TaN barrier layer based on the nitridation process, the metal TaN barrier layer is in direct contact with the NbN underlayer film or the remaining Ta film, and the N element in the metal TaN barrier layer is formed on the surface of the material layer to shield the Ta element.
7. The method of preparing a Josephson junction based on TaN according to claim 1, wherein the substrate comprises a single crystal magnesium oxide substrate, the substrate having a thickness of 0.4 mm; the thickness of the NbN underlayer film is between 150nm and 250 nm; the thickness of the metal TaN barrier layer is between 2nm and 8 nm; the thickness of the NbN top layer film is between 150nm and 250 nm; the shape of the junction region comprises a circle, the circle being directly between 1.6 μm-3 μm; the diameter of the first connection hole is between 1.2 μm and 2.6 μm; the diameter of the second connecting hole is between 1.2 and 2.6 mu m.
8. The method of fabricating a josephson junction based on TaN of any of claims 1-7, wherein the NbN bottom layer film, the metal TaN barrier layer, and the NbN top layer film are simultaneously etched based on the first etching process; and simultaneously etching the NbN top layer film and the metal TaN barrier layer based on the second etching process.
9. The method of preparing a TaN based Josephson junction according to claim 8, wherein the first etch process comprises step exposure and inductively coupled plasma etching; the second etching process comprises step exposure and inductively coupled plasma etching; the NbN underlayer film is prepared by a direct-current reactive magnetron sputtering method; the NbN top layer film is prepared by a direct-current reactive magnetron sputtering method; the wiring layer is prepared by a direct current reactive magnetron sputtering method.
10. A TaN-based josephson junction, wherein the TaN-based josephson junction comprises:
a substrate;
the functional structure layer is formed on the substrate and comprises a bottom electrode, a junction barrier layer and a top electrode from bottom to top, wherein the junction barrier layer comprises a metal TaN layer, the bottom electrode comprises a bottom NbN layer, the top electrode comprises a top NbN layer, and the metal TaN layer is formed on the basis of an ion nitriding treatment process of a Ta film;
the isolation layer is formed on the exposed surfaces of the top electrode, the junction barrier layer and the bottom electrode and on the surrounding substrate, and a first connecting hole exposing the top electrode and a second connecting hole exposing the bottom electrode are formed in the isolation layer;
a wiring layer including a first wiring section electrically connected to the top electrode through the first connection hole and a second wiring section electrically connected to the bottom electrode through the second connection hole.
11. The TaN-based josephson junction according to claim 10, wherein the substrate comprises a single crystal magnesium oxide substrate, the substrate having a thickness of 0.4 mm; the thickness of the NbN underlayer film is between 150nm and 250 nm; the thickness of the metal TaN barrier layer is between 2nm and 8 nm; the thickness of the NbN top layer film is between 150nm and 250 nm; the shape of the junction region comprises a circle, the circle being directly between 1.6 μm-3 μm; the diameter of the first connection hole is between 1.2 μm and 2.6 μm; the diameter of the second connecting hole is between 1.2 and 2.6 mu m.
12. The josephson junction based on TaN of any of claims 10-11, wherein the lower surface of the metal TaN layer is in direct contact with the bottom NbN layer or the remaining Ta film; the upper surface of the metal TaN layer is directly contacted with the top NbN layer, and the N element in the metal TaN layer is formed on the surface of the material layer and shields the Nb element.
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