CN114824054A - VN-based SNS Josephson junction and preparation method thereof - Google Patents

Abstract

The invention provides a VN-based SNS Josephson junction and a preparation method thereof, wherein the preparation method of the VN-based SNS Josephson junction comprises the following steps of providing a substrate, forming a functional material layer comprising a NbN bottom layer film, a VN barrier layer and a NbN top layer film on the substrate by adopting direct current reactive magnetron sputtering, etching the functional material layer to form a functional layer comprising a bottom electrode, a VN junction barrier layer and a top electrode, forming an isolation layer covering the exposed surface of the functional layer and the upper surface of the substrate, forming a first contact hole and a second contact hole on the isolation layer, forming a wiring layer covering the isolation layer and filling the first contact hole and the second contact hole, and etching the wiring layer to form a first wiring part and a second wiring part. The VN barrier layer which is metallic at low temperature is formed by a direct-current reaction magnetron sputtering method, so that the VN junction barrier layer which is high in flatness, stable in composition, stable in resistivity and good in uniformity is obtained, and the quality of a Josephson junction is improved.

Description

VN-based SNS Josephson junction and preparation method thereof

Technical Field

The invention belongs to the field of superconducting electronics, and relates to a SNS Josephson junction based on VN and a preparation method thereof.

Background

The advantage of a superconducting Single Flux Quantum (SFQ) circuit with a Josephson junction as a basic unit in speed and power consumption makes the circuit have wide application prospect in the fields of high-performance calculation, voltage reference, high-precision analog-to-digital conversion and the like. At present, the mainstream of a superconducting integrated circuit is formed based on a superconducting Nb material and an Nb/Al-AlOx/Nb Josephson junction external parallel resistor, but the integration level and high-frequency application of the circuit are limited in material and structure due to the existence of small inductance, energy gap and shunt resistance of Nb. Parasitic inductance and capacitance introduced by the SIS junction ultrathin (1-3 nm) barrier layer and the bypass resistor face serious challenges in process repeatability and stability, and the comprehensive performances of critical current density, characteristic voltage and the like of the SIS junction ultrathin (1-3 nm) barrier layer and the bypass resistor far cannot meet the development requirements in the field of superconducting electronics and become a main bottleneck restricting the development of Josephson devices.

The Cooper pair in a Superconductor-Normal metal-Superconductor (SNS) junction realizes superconducting coupling 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, the SNS junction has a high S/N interface electron transmittance, and has a high critical current density (J) comparable to that of the SIS junction when the N layer is thick (d-10 nm) _c ) And the repeatability and stability of the process are ensured. However, the characteristic voltage (I) of SNS junctions compared to SIS junctions _c R _n ) And the characteristic voltage of the SNS junction is closely related to the material characteristics of the barrier layer and the S/N interface characteristics. In addition, the small superconducting coherence length (5 nm) of NbN places higher demands on the interface control of three-layer films. Therefore, selecting a proper barrier layer material and preparing a three-layer film with a clean interface becomes an important technical problem to be solved in the field of NbN SNS Josephson junctions. The current mainstream of NbN-series Josephson junctions is NbN/AlN/NbN junctions, which have small leakage current and large energy gap voltage (>5mV)，J _c In the range of several tens to several thousands A/cm ² The range varies. AlN can realize the transformation from an insulation state to a normal state through a stoichiometric control ratio, however, the AlN shows a piezoelectric effect due to the enhanced quantum-phonon coupling effect, the crystal structure of the AlN barrier layer needs to be accurately controlled to inhibit the influence of the piezoelectric effect on the performance of the Josephson junction, the potential barrier of the AlN barrier layer is difficult to control, and the obtained NbN/AlN/ion ratio is/isThe interfaces between the three layers of the NbN functional material layer are not sharp.

Therefore, a method for preparing a josephson junction with a clear interface and a controllable barrier at the interface of the barrier layer is urgently needed.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a VN-based SNS josephson junction and a method for preparing the same, which are used to solve the problems of unclear interfaces between film layers in a functional material layer and difficulty in adjusting a barrier at an interface of a barrier layer in the prior art when preparing a josephson junction.

To achieve the above and other related objects, the present invention provides a method for preparing a VN-based SNS josephson junction, comprising the steps of:

providing a substrate;

forming a functional material layer on the substrate by adopting direct-current reactive magnetron sputtering, wherein the functional material layer comprises a laminated NbN bottom layer film, a VN barrier layer and a NbN top layer film;

etching the functional material layer to form a functional layer comprising a bottom electrode, a VN junction barrier layer and a top electrode, and forming an isolation layer covering the exposed surface of the functional layer and the upper surface of the substrate;

forming a first contact hole and a second contact hole in the isolation layer, wherein the top electrode is exposed at the bottom of the first contact hole, and the bottom electrode is exposed at the bottom of the second contact hole;

and forming a wiring layer filled in the first contact hole and the second contact hole in the isolation layer, and etching the wiring layer to form a first wiring part and a second wiring part, wherein the first wiring part is electrically connected with the top electrode through the first contact hole, and the second wiring part is electrically connected with the bottom electrode through the second contact hole.

Optionally, the substrate comprises magnesium oxide.

Optionally, in the NbN underlayer film, the Nb atom proportion is the same as the N atom proportion; in the VN barrier layer, the proportion of V atoms is different from that of N atoms; in the NbN top layer film, the Nb atom proportion is the same as the N atom proportion.

Optionally, the barrier of the VN barrier layer is modulated according to the ratio of V atoms to N atoms in the VN barrier layer.

Optionally, in the process of forming the functional layer, the functional material layer is etched first to define a bottom electrode, and then the NbN top layer film and the VN barrier layer are etched to obtain the top electrode and the VN junction barrier layer.

Optionally, the NbN top layer film and the VN barrier layer are further etched to obtain the top electrode and the VN junction barrier layer, and the top electrode is in smooth transition connection with the sidewall of the VN junction barrier layer.

Optionally, the VN junction barrier layer is circular in shape and has a diameter in the range of 1.6 to 3.0 μm.

Optionally, the top electrode has a thickness ranging from 150nm to 250nm, the VN junction barrier layer has a thickness ranging from 5nm to 30nm, and the top electrode has a thickness ranging from 150nm to 250nm

Optionally, the material of the wiring layer includes NbN, and the thickness of the wiring layer is in a range of 300nm to 400 nm.

The invention also provides a VN-based SNS Josephson junction which is prepared by adopting the preparation method.

As described above, the VN barrier layer in the SNS josephson junction and the preparation method thereof according to the present invention are formed by a dc reactive magnetron sputtering method to obtain a thicker VN barrier layer, the formed VN barrier layer can form a clear interface with the NbN bottom layer film and the top layer film, and by adjusting and controlling process parameters in the process of forming the VN barrier layer, a VN barrier layer with high density, stable composition, high interface flatness, good uniformity, controllable resistivity, and metallic property at low temperature can be obtained, which has a high industrial utility value.

Drawings

Fig. 1 shows a flow chart of a method for preparing a VN-based SNS josephson junction of the present invention.

Fig. 2 shows a schematic sectional structure of a provided substrate for the VN-based SNS josephson junction manufacturing method of the present invention.

Fig. 3 is a schematic cross-sectional structure view showing a functional material layer formed in the VN-based SNS josephson junction manufacturing method of the present invention.

Fig. 4 is a schematic sectional view showing the VN-based SNS josephson junction of the present invention after defining the bottom electrode.

Fig. 5 is a schematic cross-sectional view showing a TaN junction barrier layer and a top electrode defined by the VN-based SNS josephson junction manufacturing method of the present invention.

Fig. 6 is a schematic cross-sectional view showing the isolation layer formed according to the VN-based SNS josephson junction manufacturing method of the present invention.

Fig. 7 is a schematic sectional view showing the first contact hole and the second contact hole after the VN-based SNS josephson junction of the present invention is formed.

Fig. 8 is a schematic sectional structure view showing a wiring layer after formation according to the VN-based SNS josephson junction manufacturing method of the present invention.

Fig. 9 is a schematic sectional view showing the first and second wiring portions formed in the VN-based SNS josephson junction manufacturing method of the present invention.

Fig. 10 shows a current-voltage diagram for a VN-based SNS josephson junction of the present invention.

Description of the element reference

1 substrate

11 NbN underlayer film

111 bottom electrode

12 VN barrier layer

121 VN junction barrier layer

13 NbN top layer film

131 top electrode

14 functional layers

2 isolating layer

21 first contact hole

22 second contact hole

3 wiring layer

31 first wiring part

32 second wiring part

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.

Please refer to fig. 1 to 10. 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 components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

Example one

This example provides a method for preparing an SNS josephson junction based on NbN, as shown in fig. 1, which is a flow chart of the method for preparing the SNS josephson junction, comprising the steps of:

s1: providing a substrate;

s2: forming a functional material layer on the substrate by adopting direct-current reactive magnetron sputtering, wherein the functional material layer comprises a laminated NbN bottom layer film, a VN barrier layer and a NbN top layer film;

s3: etching the functional material layer to form a functional layer comprising a bottom electrode, a VN junction barrier layer and a top electrode, and forming an isolation layer covering the exposed surface of the functional layer and the upper surface of the substrate;

s4: forming a first contact hole and a second contact hole in the isolation layer, wherein the top electrode is exposed at the bottom of the first contact hole, and the bottom electrode is exposed at the bottom of the second contact hole;

s5: and forming a wiring layer filled in the first contact hole and the second contact hole on the isolation layer, and etching the wiring layer to form a first wiring part and a second wiring part, wherein the first wiring part is electrically connected with the top electrode through the first contact hole, and the second wiring part is electrically connected with the bottom electrode through the second contact hole.

Referring to fig. 2, the step S1 is executed: providing a substrate 1, wherein the substrate 1 comprises one of a single-layer structure and a stacked-layer structure, and since the performance of the SNS josephson junction is related to the resistivity of the barrier material and the interface flatness of the superconducting material layer/normal metal material barrier layer, the substrate 1 needs to ensure that the surface waviness of the functional material layer grown on the substrate 1 is small, i.e. the flatness of the upper surface of the functional material layer grown is ensured.

Specifically, the material of the substrate 1 includes magnesium oxide or other suitable materials, and the thickness of the substrate 1 may be set according to actual needs. In this embodiment, a single layer of magnesium oxide with a thickness of 0.4mm is selected as the substrate 1, so as to ensure high flatness of the upper surface of the functional material layer grown on the substrate 1, and meanwhile, the substrate 1 is adapted to the subsequent equipment requirement for forming the functional material layer.

Referring to fig. 3 to 6, the steps S2 and S3 are executed: forming a functional material layer on the substrate 1 by adopting direct current reactive magnetron sputtering, wherein the functional material layer comprises a laminated NbN bottom layer film 11, a laminated VN barrier layer 12 and a laminated NbN top layer film 13; and etching the functional material layer to form a functional layer 14 comprising a bottom electrode 111, a VN junction barrier layer 121 and a top electrode 131, and forming an isolation layer 2 covering the exposed surface of the functional layer 14 and the upper surface of the substrate 1.

Specifically, as shown in fig. 3, in order to form a schematic cross-sectional structure after the functional material layer is formed, the NbN underlayer film 11 is formed on the upper surface of the substrate 1 by using dc reactive magnetron sputtering, and the metering ratio of Nb to N is controlled to be 1:1 in the process of forming the NbN underlayer film 11, so as to ensure that the NbN underlayer film 11 exhibits superconducting characteristics at a low temperature, and simultaneously, the sputtering time and power are adjusted to obtain the NbN underlayer film 11 with a preset thickness and a flat upper surface.

Specifically, the VN barrier layer 12 is formed by a direct current reactive magnetron sputtering method after the NbN underlayer film 11 is formed, and the thickness of the VN barrier layer 12 is in a range of 5nm to 30 nm.

Specifically, in the process of forming the VN barrier layer 12, the metering ratio of V and N is precisely controlled to obtain the metallic VN barrier layer 12, and the reactive sputtering time and the reactive sputtering power are simultaneously adjusted to obtain the VN barrier layer 12 with a preset thickness, high upper surface flatness, high interface flatness with the NbN underlayer film 11, good repeatability and good uniformity.

Specifically, in the process of forming the VN barrier layer 12, inert gas shielding gas needs to be continuously introduced to prevent the formation of an oxide at the interface, so that the problem of poor process stability is avoided, and the quality of preparing the VN barrier layer 12 is ensured. In this example, argon (Ar) was selected as the shielding gas.

As an example, the VN barrier layer 12 exhibits normal metallic behavior at low temperatures, and the V to N stoichiometry of the VN barrier layer film deviates from 1:1, regulating nitrogen (N) during fabrication ₂ ) The ratio of the V element atoms is higher than that of the N element atoms, and the ratio of the Nb element to the N element in the VN barrier layer 12 is different, and the resistivity of the VN barrier layer 12 is also different, that is, the resistivity of the VN barrier layer 12 can be freely adjusted by adjusting the ratio of the V element to the N element in the VN barrier layer 12, so that the VN barrier layer 12 with a suitable resistivity is obtained.

For example, after the VN barrier layer 12 is formed, the NbN top layer film 13 is formed on the upper surface of the VN barrier layer 12 by a dc reactive magnetron sputtering method.

Specifically, in the process of forming the NbN top layer film 13, the metering ratio of Nb to N is precisely controlled to be 1:1 so that the obtained NbN top layer film 13 has superconducting characteristics at a low temperature, and the reactive sputtering time and the reactive sputtering power are simultaneously regulated and controlled so as to obtain the NbN top layer film 13 with a preset thickness and high interface flatness, good repeatability and good uniformity with the VN barrier layer 12.

Specifically, the NbN underlayer film 11 and the top layer film 13 both have a high superconducting transition temperature (T) and a high tg _c 16.5K), large superconducting energy gap (delta-3 meV) and high characteristic frequency (1.4 THz).

For example, in the NbN underlayer film 11, the atomic proportion of Nb is the same as the atomic proportion of N; in the VN barrier layer 12, the ratio of V atoms is different from the ratio of N atoms; in the NbN top layer film 13, the Nb atomic proportion is the same as the N atomic proportion.

As an example, the barrier of the VN barrier layer 12 is regulated according to the proportion of V atoms to N atoms in the VN barrier layer 12, that is, the VN barrier layer 12 resistivity is regulated by regulating V atoms to N atoms in the VN barrier layer 12, which in turn regulates the barrier at the interface between the VN barrier layer 12 and the NbN bottom layer film 11 and the NbN top layer film 13.

Specifically, the VN barrier layer 12 is a VN layer having a different Nb to N stoichiometric ratio and being metallic.

Specifically, in the process of forming the VN barrier layer 12, the time for forming the VN barrier layer 12 is controlled by adjusting and controlling the process parameters.

Specifically, after the VN barrier layer 12 is formed, the NbN top layer film 13 is formed on the upper surface of the VN barrier layer 12 by using direct current reactive magnetron sputtering, and the metering ratio of Nb to N is controlled to be 1:1 in the process of forming the NbN top layer film 13, so as to ensure that the NbN top layer film 13 exhibits superconducting characteristics at a low temperature, and simultaneously, the sputtering time and power are adjusted, so as to obtain the NbN top layer film 13 with a preset thickness and a flat upper surface.

As an example, in the process of forming the functional layer 14, the functional material layer is etched first to define a bottom electrode 111, and then the NbN top layer film 13 and the VN barrier layer 12 are etched to obtain the top electrode 131 and the VN junction barrier layer 121.

Specifically, as shown in FIG. 4, to form the bottom electrode111, etching the functional material layer by step exposure and inductively coupled plasma etching or other suitable method to form the bottom electrode 111, wherein the etching gas may include CF ₄ And Ar.

Specifically, as shown in fig. 5, in order to form the VN junction barrier layer 121 and the top electrode 131, the NbN top layer film 13 and the VN barrier layer 12 are etched by step exposure, inductively coupled plasma etching or other suitable methods to form the VN junction barrier layer 121 and the top electrode 131, and the etching gas may include CF ₄ And Ar.

Specifically, the NbN top layer film 13 and the VN barrier layer 12 are etched in one step to obtain the VN junction barrier layer 121 and the top electrode 131, and the top electrode 121 is connected with the sidewall of the VN junction barrier layer 131 in a smooth transition manner, so that the step of forming the functional layer 14 is simplified, the straightness of etching and the uniformity of the sidewall of the VN junction barrier layer 121 and the top electrode 131 are ensured, and the uneven distribution of the size of the VN junction barrier layer in the vertical direction is effectively avoided.

Illustratively, the VN junction barrier layer 121 is circular in shape and has a diameter in the range of 1.6 μm to 3.0 μm.

Specifically, as shown in fig. 6, in order to show a schematic cross-sectional structure after the isolation layer 2 is formed, the thickness of the isolation layer 2 ranges from 200nm to 300nm, and preferably, the thickness of the isolation layer 2 is 250 nm.

Specifically, the method for forming the isolation layer 2 includes physical vapor deposition, chemical vapor deposition, or other suitable methods.

Specifically, the material of the isolation layer 2 includes silicon dioxide, silicon nitride, or other suitable insulating materials. In this example, a silicon dioxide layer is used as the isolation layer 2.

Referring to fig. 7 and 9, the steps S4 and S5 are executed: forming a first contact hole 21 and a second contact hole 22 in the isolation layer 2, wherein the top electrode 131 is exposed at the bottom of the first contact hole 21, and the bottom electrode 111 is exposed at the bottom of the second contact hole 22; forming a wiring layer 3 on the isolation layer 2 and filling the first contact hole 21 and the second contact hole 22, and etching the wiring layer 3 to form a first wiring portion 31 and a second wiring portion 32, wherein the first wiring portion 31 is electrically connected to the top electrode 131 through the first contact hole 21, and the second wiring portion 32 is electrically connected to the bottom electrode 111 through the second contact hole 22.

Specifically, the method for forming the first contact hole 21 and the second contact hole 22 includes step exposure and reactive ion etching or other suitable methods.

As an example, as shown in fig. 7, in order to illustrate the cross-sectional structure after the first contact hole 21 and the second contact hole 22 are formed, the opening diameter of the first contact hole ranges from 1.2 μm to 2.6 μm, and the opening diameter of the second contact hole ranges from 1.2 μm to 2.6 μm.

Specifically, the wiring layer 3 is formed by direct current reactive sputtering or other suitable method.

As an example, as shown in fig. 8, in order to schematically show a cross-sectional structure after forming the wiring layer 3, a material of the wiring layer 3 includes NbN or other suitable material, a thickness of the wiring layer 3 is in a range of 300nm to 400nm, and preferably, a thickness of the wiring layer 3 is 350 nm. In this embodiment, NbN is selected as a material of the wiring layer 3.

Specifically, as shown in fig. 9, in order to form the first wiring portion 31 and the second wiring portion 32 by using the schematic cross-sectional structure shown after the step exposure and the inductively coupled plasma etching or other suitable methods to etch the wiring layer 3 to form the first wiring portion 31 and the second wiring portion 32, the etching gas may include CF ₄ And Ar.

In the preparation method of the SNS josephson junction based on NbN of the present embodiment, the VN barrier layer 12 is formed by redesigning the process of forming the VN barrier layer 12, the dc reactive sputtering process is used to form the VN barrier layer 12, the composition of the VN barrier layer 12 formed by the dc reactive sputtering process does not change with thickness, the resistivity is stable, the uniformity is good, and the repeatability is high, the quality of the VN barrier layer 12 is improved, the formed VN barrier layer 12, the NbN bottom layer film 11 and the NbN top layer film 13 have clear and flat interfaces, and thus the quality of the SNS josephson junction of NbN is improved. In addition, the VN barrier layer 12 formed by the dc reactive sputtering method can freely control the resistivity, thickness, production period, and Nb to N stoichiometric ratio of the VN barrier layer 12 by controlling the process parameters.

Example two

In this embodiment, a VN-based SNS josephson junction is provided, as shown in fig. 9, which is a schematic sectional structure diagram of the SNS josephson junction, and the VN-based SNS josephson junction is manufactured by the VN-based SNS josephson junction manufacturing method described in the first embodiment.

Specifically, the SNS josephson junction of the VN includes the substrate 1, the functional layer 14, the isolation layer 2, the first wiring portion 31, the second wiring portion 32, the first through hole 311, and the second through hole 321, wherein the functional layer 14 is located on the substrate 1, the functional layer 14 includes the bottom electrode 111, the VN junction barrier layer 121, and the top electrode 131 stacked upward, the isolation layer 2 covers the upper surface of the substrate 1 and the exposed surface of the functional layer 14, the isolation layer 2 is provided with the first contact hole 21 whose bottom exposes the top electrode 131, and the second contact hole 22 whose bottom exposes the bottom electrode 111, the first wiring portion 31 fills the first contact hole 21, and the first wiring portion 31 is provided with the first through hole 311, the second wiring portion 32 fills the second contact hole 22, and a second via hole 321 is provided in the second wiring portion 32.

Specifically, the first wiring portion 31 is electrically connected to the top electrode 131 through the first contact hole 21, and the second wiring portion 32 is electrically connected to the bottom electrode 111 through the second contact hole 22.

Specifically, the first through hole 311 and the second through hole 321 are used to lead out the first wiring portion 31 and the second wiring portion 32, respectively.

Specifically, the VN junction barrier layer 121 has a thickness ranging from 5nm to 30nm, the top electrode 131 has a thickness ranging from 150nm to 250nm, the isolation layer 2 has a thickness ranging from 200nm to 300nm, and preferably, the bottom electrode 111 has a thickness of 200nm, the top electrode has a thickness of 200nm, and the isolation layer 2 has a thickness of 250 nm.

Specifically, the VN film in the VN junction barrier layer 121 prepared by the method in the first embodiment has a uniform film layer, high density, stable composition, and high interface flatness, and effectively avoids the deviation phenomenon of the stoichiometric ratio of the barrier layer, and the stoichiometric ratio of the NbN film in the VN junction barrier layer 121 is controllable, so that VN films with different electrical characteristics can be prepared, and VN films with the same electrical properties can be repeatedly obtained.

Specifically, VN in the VN junction barrier layer 121 and NbN in the top electrode 131 and the bottom electrode 111 are both nitrides, and the functional material layers forming the functional layer 14 are all obtained by a direct-current reactive magnetron sputtering method, so that the prepared NbN/VN/NbN film has high quality and a clean interface.

Specifically, the VN-based SNS Josephson junction prepared by the method in the first embodiment obtains a high-quality Josephson junction, eliminates a parallel resistor, and improves the integration level of a superconducting single magnetic flux sub-circuit.

Specifically, as shown in fig. 10, it can be seen that the SNS josephson junction based on VN is a josephson junction whose current-voltage curve is a non-hysteresis curve, in order to obtain a current-voltage curve obtained by the SNS josephson junction energization test prepared by the method in example one.

The SNS Josephson junction based on VN is prepared by the method in the first embodiment, the film layer of the VN junction barrier layer 121 in the SNS Josephson junction is uniform, high in density, stable in components, high in interface flatness and metallic at low temperature, the VN junction barrier layer 121, the top electrode 131 and the bottom electrode 111 are the same in composition, and the prepared NbN/VN/NbN film is high in quality and clean in interface, the quality of the prepared Josephson junction is improved, parallel resistance is eliminated, and the integration level of a superconducting single magnetic flux sub-circuit is improved.

In conclusion, the VN-based SNS Josephson junction and the preparation method thereof select the VN which presents metallicity at low temperature as the barrier layer, and form the barrier layer by adopting a direct-current reaction magnetron sputtering method, so as to obtain the VN barrier layer which has high density, no thickness change of components, controllable resistivity and good uniformity and presents metallicity at low temperature, and the barrier at the interface between the VN barrier layer and the NbN top layer film and the NbN bottom layer film can be controlled, so that the quality of the prepared functional material layer is high, the interface is clear and clean, and the quality of the Josephson junction is improved. In addition, by regulating and controlling the technological parameters for preparing the VN barrier layer, the thickness and the preparation period of the VN barrier layer and the stoichiometric ratio of V to N can be freely regulated and controlled, a parallel resistor is not needed, and the integration level of the Josephson junction is improved. Therefore, the present invention effectively overcomes various disadvantages of 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 (10)

1. A preparation method of a VN-based SNS Josephson junction is characterized by comprising the following steps:

providing a substrate;

forming a functional material layer on the substrate by adopting direct-current reactive magnetron sputtering, wherein the functional material layer comprises a laminated NbN bottom layer film, a VN barrier layer and a NbN top layer film;

etching the functional material layer to form a functional layer comprising a bottom electrode, a VN junction barrier layer and a top electrode, and forming an isolation layer covering the exposed surface of the functional layer and the upper surface of the substrate;

forming a first contact hole and a second contact hole in the isolation layer, wherein the top electrode is exposed at the bottom of the first contact hole, and the bottom electrode is exposed at the bottom of the second contact hole;

and forming a wiring layer filled in the first contact hole and the second contact hole on the isolation layer, and etching the wiring layer to form a first wiring part and a second wiring part, wherein the first wiring part is electrically connected with the top electrode through the first contact hole, and the second wiring part is electrically connected with the bottom electrode through the second contact hole.

2. A method of making a VN-based SNS josephson junction according to claim 1, wherein: the substrate material comprises magnesium oxide.

3. A method of making a VN-based SNS josephson junction according to claim 1, wherein: in the NbN underlayer film, the Nb atom proportion is the same as the N atom proportion; in the VN barrier layer, the proportion of V atoms is different from that of N atoms; in the NbN top layer film, the Nb atom proportion is the same as the N atom proportion.

4. A method of making a VN-based SNS josephson junction according to claim 1, wherein: the potential barrier of the VN potential barrier layer is regulated and controlled according to the ratio of V atoms to N atoms in the VN potential barrier layer.

5. A method of manufacturing a VN-based SNS josephson junction according to claim 1, comprising in the process of forming the functional layer: and etching the functional material layer to define a bottom electrode, and etching the NbN top layer film and the VN barrier layer to obtain the top electrode and the VN junction barrier layer.

6. A method of preparing a VN-based SNS Josephson junction according to claim 5, wherein: and etching the NbN top layer film and the VN barrier layer in one step to obtain the top electrode and the VN junction barrier layer, wherein the top electrode is in smooth transition connection with the side wall of the VN junction barrier layer.

7. A method of making a VN-based SNS josephson junction according to claim 1, wherein: the VN junction barrier layer is circular in shape and has a diameter ranging from 1.6 mu m to 3.0 mu m.

8. A method of making a VN-based SNS josephson junction according to claim 1, characterized in that: the top electrode is 150 nm-250 nm thick, the VN junction barrier layer is 5 nm-30 nm thick, and the top electrode is 150 nm-250 nm thick.

9. A method of making a VN-based SNS josephson junction according to claim 1, wherein: the material of the wiring layer comprises NbN, and the thickness of the wiring layer ranges from 300nm to 400 nm.

10. A VN-based SNS josephson junction, characterized in that: the VN-based SNS Josephson junction is manufactured by the method for manufacturing the VN-based SNS Josephson junction as claimed in any one of claims 1-9.

Images