High-temperature superconducting quantum interference device and preparation method thereof

Abstract

The invention provides a high-temperature superconducting quantum interference device and a preparation method thereof, a high-temperature SQUID chip and a high-temperature superconducting magnetic flux focusing pickup coil are independently designed respectively, and then the high-temperature SQUID chip and the magnetic flux focusing pickup coil are combined and fixed on a PCB substrate in a glue curing form to form the high-temperature superconducting quantum interference device. According to the preparation mode, the Josephson junction and the high-temperature superconducting magnetic flux focusing pickup coil cannot be prepared on the same layer of film, and the preparation difficulty of the high-temperature superconducting magnetic flux focusing pickup coil is low, so that the preparation yield of the high-temperature superconducting magnetic flux focusing pickup coil is greatly improved; the loss of a large-area thin film caused by large preparation difficulty of the Josephson junction is reduced, and the cost of preparing the high-temperature superconducting quantum interference device is effectively reduced. In addition, limitation of a Josephson junction preparation process is not needed, so that the size of the high-temperature superconducting magnetic flux focusing pickup coil can be further increased, and the detection sensitivity of the superconducting quantum interference device is further improved.

Description

Technical Field

[0001] The present invention relates to the field of superconducting quantum interference devices (SQUIDs), and in particular to a high-temperature superconducting quantum interference device and a preparation method thereof. Background Art

[0002] The principle of superconducting quantum interference device (SQUID) is based on magnetic flux quantization and Josephson effect. In the fields of biological magnetic field detection, earth magnetic field detection, weak current detection, displacement detection, etc., the detection research using superconducting quantum interference device has made great progress, showing the application potential of superconducting quantum interference device in these application fields. Figure 1 As shown in the figure, the superconducting quantum interference device is a magnetic detection device with extremely high sensitivity. One of the widely used configurations is a DC superconducting quantum interference device consisting of a superconducting ring and two Josephson junctions. The equivalent circuit diagram of the DC superconducting quantum interference device is shown in the figure. Figure 2 As shown in a, under a certain bias current, the voltage across the DC superconducting quantum interference device will change periodically with the change of the magnetic flux in the superconducting loop, and the period is fixed to a magnetic flux quantum Φ0 (Φ0≈1×10 -15 T). Since the flux-voltage transfer curve of DC superconducting quantum interference devices is nonlinear, this is very unfavorable for practical applications. Figure 2 As shown in Figure b, in order to further realize the linearization of the flux voltage transfer curve of the DC superconducting quantum interference device, a flux locking circuit (FLL) is introduced into the DC superconducting quantum interference device. By combining the superconducting quantum interference device and the flux locking circuit, the superconducting quantum interference device can realize the linear conversion of the input signal and the output voltage signal. The minimum magnetic field that the superconducting quantum interference device can detect is defined as the magnetic field sensitivity of the device, and the magnetic field sensitivity of the superconducting quantum interference device is positively correlated with the size of the magnetic flux focusing pickup coil of the superconducting quantum interference device, that is, the larger the size of the magnetic flux focusing pickup coil, the higher the magnetic field sensitivity of the superconducting quantum interference device.

[0003] In the prior art, most commonly used high-temperature superconducting materials are ceramic materials, such as yttrium barium copper oxide. It is difficult to grow multilayer films and prepare through holes based on this high-temperature superconducting material. Therefore, high-temperature superconducting quantum interference devices prepared based on high-temperature superconducting materials mostly adopt a planar configuration, that is, the Josephson junction and the magnetic flux focusing pickup coil are prepared on the same layer of yttrium barium copper oxide film. In order to improve the magnetic field sensitivity of the superconducting quantum interference device, it is necessary to increase the size of the magnetic flux focusing pickup coil, which requires the preparation of a larger size of yttrium barium copper oxide film. In this process, due to the high precision requirements of the micro-nano processing of the Josephson junction and the low yield rate, once the preparation of the Josephson junction fails, the yttrium barium copper oxide film used to prepare the high-temperature superconducting magnetic flux focusing pickup coil can no longer be used, resulting in a low yield rate of the high-temperature superconducting quantum interference device. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a high-temperature superconducting quantum interference device and a preparation method thereof, which is used to solve the problem that it is difficult to prepare a high-temperature superconducting flux focusing pickup coil and a Josephson junction on a thin film due to the low yield of the Josephson junction in the prior art, thereby causing the high-temperature superconducting quantum interference device to have a low yield and high preparation cost.

[0005] To achieve the above-mentioned object and other related objects, the present invention provides a method for preparing a high-temperature superconducting quantum interference device, the preparation method at least comprising:

[0006] Providing a substrate, and etching the substrate to form a through hole;

[0007] epitaxially growing a buffer layer and a first high-temperature superconducting thin film layer in sequence on the substrate by magnetron sputtering, and processing the buffer layer, the first high-temperature superconducting thin film layer and the substrate by micromachining technology to form a high-temperature superconducting magnetic flux focusing pickup coil;

[0008] Providing a PCB substrate, fixing the high-temperature superconducting flux focusing pickup coil on the PCB substrate and fixing a high-temperature SQUID chip including a Josephson junction in the through hole;

[0009] A signal connector is arranged on the top of the PCB substrate, and the signal connector is communicatively connected with an external device.

[0010] Optionally, the micromachining process includes photolithography and ion beam etching.

[0011] Optionally, the substrate is a silicon substrate, a magnesium oxide substrate or a sapphire substrate.

[0012] Optionally, the first high-temperature superconducting thin film layer is a yttrium-barium-copper-oxide thin film layer and the thickness of the first high-temperature superconducting thin film layer is 50 nm.

[0013] Optionally, the through hole is in the shape of a square hole, and the through hole is located at the center of the substrate.

[0014] Optionally, the substrate is in the shape of a square substrate, the size of the substrate is 20 mm, and the size of the through hole is 5 mm.

[0015] Optionally, the Josephson junction in the high temperature SQUID chip includes two sub-Josephson junctions.

[0016] The present invention also provides a high-temperature superconducting quantum interference device, which is prepared by the above-mentioned preparation method, and the high-temperature superconducting quantum interference device comprises:

[0017] A substrate, wherein a square through hole is provided at the center of the substrate;

[0018] A buffer layer and a first high-temperature superconducting film layer, wherein the buffer layer and the first high-temperature superconducting film layer are sequentially arranged on the substrate, and the buffer layer, the first high-temperature superconducting film layer and the substrate form a high-temperature superconducting magnetic flux focusing pickup coil;

[0019] A high temperature SQUID chip containing a Josephson junction is embedded in the square through hole and fixed on the PCB substrate together with the high temperature superconducting flux focusing pickup coil;

[0020] The signal connector is used to lead out the high-temperature superconducting flux focusing pickup coil and the SQUID chip, and to communicate with external devices.

[0021] Optionally, the first high-temperature superconducting thin film layer is a yttrium-barium-copper-oxide thin film layer and the thickness of the first high-temperature superconducting thin film layer is 50 nm.

[0022] Optionally, the size of the substrate is 20 mm and the size of the through hole is 5 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a configuration diagram of a superconducting quantum interference device in the prior art.

[0024] Figure 2 Shown is an equivalent circuit diagram of a superconducting quantum interference device in the prior art.

[0025] Figure 3 Shown is a process flow chart of the method for preparing a high-temperature superconducting quantum interference device of the present invention.

[0026] Figures 4 to 6 Shown is a top view of the structure of the high-temperature superconducting quantum interference device of the present invention.

[0027] Figure 7 Shown is a simulation result diagram of the magnetic field focusing effect of the high-temperature superconducting flux focusing pickup coil in the present invention.

[0028] Figure 8 Shown is a comparison of the magnetic field noise power density spectra with and without the high-temperature superconducting flux focusing pickup coil of the present invention.

[0029] Component number description

[0030] 10. Substrate; 101. Through hole; 11. First high-temperature superconducting thin film layer; 12. High-temperature SQUID chip; 13. PCB substrate; 14. Signal connector; S1 to S4. Steps. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0033] For ease of description, spatial relational terms such as “under”, “below”, “below”, “below”, “over”, etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relational terms are intended to include other orientations of the device in use or operation in addition to the orientation depicted in the drawings, and 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 between the first and second features, so that the first and second features may not be in direct contact. In addition, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or one or more intervening layers may also be present.

[0034] Please refer to the attached drawings. It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show the components related to the present invention rather than the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0035] like Figure 3 As shown, the present invention provides a method for preparing a high-temperature superconducting quantum interference device, the preparation method at least comprising:

[0036] S1: providing a substrate 10, and etching the substrate 10 to form a through hole 101;

[0037] S2: epitaxially growing a buffer layer and a first high-temperature superconducting thin film layer 11 in sequence on the substrate 10 by magnetron sputtering, and processing the buffer layer, the first high-temperature superconducting thin film layer 11 and the substrate 10 by micromachining technology to form a high-temperature superconducting magnetic flux focusing pickup coil;

[0038] S3: providing a PCB substrate 13, fixing the high-temperature superconducting flux focusing pickup coil on the PCB substrate 13 and fixing the high-temperature SQUID chip 12 including a Josephson junction in the through hole 101;

[0039] S4: a signal connector 14 is arranged on the top of the PCB substrate 13, and the signal connector 14 is communicatively connected with an external device.

[0040] First, execute step S1, such as Figure 4 As shown, a substrate 10 is provided, and the substrate 10 is etched to form a through hole 101 .

[0041] As an example, the substrate 10 may include one of a silicon substrate 10, a magnesium oxide substrate 10, a sapphire substrate 10 and a silicon carbide substrate 10, and the specific selection may be made according to the needs. The substrate 10 may be a wafer-level substrate 10, such as a 6-inch, 8-inch, 12-inch wafer-level substrate 10, and the shape of the substrate 10 may also be square. In this embodiment, in order to prepare a high-quality first superconducting film layer 11, the substrate 10 is preferably a square sapphire substrate 10 and the size of the substrate 10 is 20 mm. Before etching the provided substrate 10, it is also inspected, including appearance inspection, electrical performance inspection, flatness inspection, size inspection, etc., so that the quality of the substrate 10 can meet the requirements of subsequent process treatment.

[0042] Specifically, the substrate 10 is etched to form a through hole 101 on the substrate 10 . The through hole 101 is a square hole with a size of 5 mm and is located at the exact center of the substrate 10 , that is, the through hole 101 is concentrically arranged with the substrate 10 .

[0043] Then, step S2 is performed, such as Figure 5 As shown, a buffer layer and a first high-temperature superconducting film layer 11 are epitaxially grown in sequence on the substrate 10 by magnetron sputtering, and the buffer layer, the first high-temperature superconducting film layer 11 and the substrate 10 are processed by micromachining technology to form a high-temperature superconducting flux focusing pickup coil.

[0044] Specifically, the present invention can use magnetron sputtering to sequentially epitaxially grow a buffer layer and a first high temperature superconducting film layer 11 on the substrate 10. The buffer layer and the first high temperature superconducting film layer 11 can be grown in different chambers without destroying the vacuum environment.

[0045] As an example, the material of the buffer layer includes cerium oxide, PBCO or SrTiO3, etc. In this embodiment, the material of the buffer layer is preferably cerium oxide. The buffer layer can change the crystal orientation of the growth of the first high-temperature superconducting film layer 11, enhance the lattice matching between the first high-temperature superconducting film layer 11 and the substrate 10, so as to grow a high-quality first high-temperature superconducting film layer 11.

[0046] As an example, the first high temperature superconducting film layer 11 is a yttrium barium copper oxide film layer and the thickness of the first high temperature superconducting film layer 11 is 50 nm. The yttrium barium copper oxide film layer is a high temperature superconducting material with complete anti-magnetic properties. The buffer layer, the first high temperature superconducting film layer 11 and the substrate 10 are etched by micromachining technology to form the following Figure 5 The structure shown in the figure, the micro-fabrication process includes but is not limited to photolithography and etching. Figure 5 As shown, the first high-temperature superconducting film layer 11 is designed to form a fine slit structure by etching on the substrate 10. Due to the complete anti-magnetism of the high-temperature superconducting material, the magnetic field cannot penetrate the first superconducting film layer 11 where the first high-temperature superconducting film layer 11 is located, so that the magnetic field can only pass through the through hole 101 and the fine slit structure, and finally achieve the focusing effect of the magnetic field. Figure 7 As shown, it shows the simulation result diagram of the magnetic field focusing effect of the high-temperature superconducting flux focusing pickup coil in the present invention. The simulation sets the ambient magnetic field to a uniform strong field of 1T. According to the simulation result diagram of the magnetic field focusing effect, the magnetic field strength of the annular region with the first high-temperature superconducting film layer 11 is almost 0, while at the position of the middle through hole 101 and the slit structure, the magnetic field strength can reach 4T, which means that the magnetic field strength in the middle through hole 101 region is magnified by 3 times. The high-temperature SQUID chip 12 is placed in the middle through hole 101 region. The high-temperature superconducting flux focusing pickup coil amplifies the magnetic field, so that the high-temperature SQUID chip 12 is able to detect the magnetic field more efficiently, and finally improves the magnetic field sensitivity of the subsequently formed high-temperature superconducting quantum interference device.

[0047] Then execute step S3, such as Figure 6 As shown, a PCB substrate 13 is provided, the high-temperature superconducting flux focusing pickup coil is fixed on the PCB substrate 13 and the high-temperature SQUID chip 12 including the Josephson junction is fixed in the through hole 101 .

[0048] As an example, the Josephson junction in the high temperature SQUID chip 12 includes two sub-Josephson junctions. It should be noted that taking another wafer and preparing a high temperature SQUID chip 12 including a Josephson junction on the wafer is well known in the art and will not be described in detail here.

[0049] Specifically, a PCB substrate 13 is provided, and the high-temperature superconducting flux focusing pickup coil is first fixed on the PCB substrate 13 through a gluing process, and then the prepared high-temperature SQUID chip 12 containing a Josephson junction is also fixed in the through hole 101 on the substrate 10 through a gluing process and connected to the PCB substrate 13.

[0050] Then execute step S4, such as Figure 6 As shown, a signal connector 14 is disposed on the top of the PCB substrate 13, and the signal connector 14 is communicatively connected with an external device.

[0051] Specifically, a signal connector 14 is provided on the top of the PCB substrate 13 so that the superconducting quantum interference device can communicate with external devices. In addition, the high-temperature superconducting flux focusing pickup coil generally works in a liquid nitrogen environment, so the signal connector 14 provided on the top of the PCB substrate 13 should be able to maintain good conductivity in the liquid nitrogen environment, so as to adapt to the working environment of the high-temperature superconducting flux focusing pickup coil.

[0052] Furthermore, the magnetic field noise power density spectrum of the same high-temperature superconducting quantum interference device before and after the assembly of the high-temperature superconducting flux focusing pickup coil was tested to quantify and compare the effect of the high-temperature superconducting flux focusing pickup coil on the magnetic field sensitivity of the high-temperature superconducting quantum interference device. The noise power density spectrum of the high-temperature superconducting quantum interference device represents the noise level of the device itself. The signal to be measured that is lower than the noise of the device itself will not be detected. Therefore, the magnetic field noise of the high-temperature superconducting quantum interference device itself can be used as a quantitative standard for magnetic field sensitivity.

[0053] like Figure 8 As shown in Figure 2, after using the high-temperature superconducting flux focusing pickup coil, the magnetic field noise (white noise band) of the high-temperature superconducting quantum interference device is reduced from 556fT / Hz1 / 2 to 147fT / Hz1 / 2, which increases the magnetic field sensitivity by about 3.78 times. This result is consistent with Figure 8 The simulation results of the magnetic field focusing effect of the high-temperature superconducting flux focusing pickup coil shown are consistent.

[0054] In another embodiment, if Figure 6 As shown, the present invention provides a high-temperature superconducting quantum interference device, which is prepared by the above method, and the high-temperature superconducting quantum interference device at least comprises:

[0055] A substrate 10, wherein a square through hole 101 is provided at the center of the substrate 10;

[0056] A buffer layer and a first high-temperature superconducting film layer 11, wherein the buffer layer and the first high-temperature superconducting film layer 11 are sequentially arranged on the substrate 10, and the buffer layer, the first high-temperature superconducting film layer 11 and the substrate 10 form a high-temperature superconducting magnetic flux focusing pickup coil;

[0057] A high temperature SQUID chip 12 containing a Josephson junction is embedded in the square through hole 101 and fixed on a PCB substrate 13 together with the high temperature superconducting flux focusing pickup coil;

[0058] The signal connector 14 is used to lead out the high-temperature superconducting flux focusing pickup coil and the high-temperature SQUID chip 12 and communicate with external devices.

[0059] As an example, the substrate 10 is a silicon substrate 10, a magnesium oxide substrate 10 or a sapphire substrate 10, the size of the substrate 10 is 20 mm and the size of the through hole is 5 mm, and the through hole 101 is located at the exact center of the substrate 10, that is, the through hole 101 is concentrically arranged with the substrate 10.

[0060] As an example, the material of the buffer layer includes cerium oxide, PBCO or SrTiO3, etc. In this embodiment, the material of the buffer layer is preferably cerium oxide. The buffer layer can change the crystal orientation of the growth of the first high-temperature superconducting film layer 11, enhance the lattice matching between the first high-temperature superconducting film layer 11 and the substrate 10, so as to grow a high-quality first high-temperature superconducting film layer 11.

[0061] As an example, the first high-temperature superconducting film layer 11 is a yttrium barium copper oxide film layer and the thickness of the first high-temperature superconducting film layer 11 is 50nm. The yttrium barium copper oxide film layer is a high-temperature superconducting material with complete anti-magnetism. The first high-temperature superconducting film layer 11 is designed to form a fine slit structure on the substrate 10 through a micromachining process. Due to the complete anti-magnetism of the high-temperature superconducting material, the magnetic field cannot penetrate the first high-temperature superconducting film layer 11 where the first high-temperature superconducting film layer 11 is located, so that the magnetic field can only pass through the through hole 101 and the fine slit structure, and finally achieve the focusing effect of the magnetic field. The high-temperature SQUID chip 12 is placed in the middle through hole 101 area of ​​the substrate 10. The high-temperature superconducting flux focusing pickup coil amplifies the magnetic field, so that the high-temperature SQUID chip 12 improves the detection capability of the magnetic field, and finally improves the magnetic field sensitivity of the high-temperature superconducting quantum interference device.

[0062] Since the high-temperature superconducting flux focusing pickup coil generally works in a liquid nitrogen environment, the signal connector 14 arranged on the top of the PCB substrate 13 can maintain good conductivity in the liquid nitrogen environment, thereby being able to adapt to the working environment of the high-temperature superconducting flux focusing pickup coil.

[0063] In summary, the present invention provides a high-temperature superconducting quantum interference device and a preparation method thereof, wherein a high-temperature SQUID chip with a Josephson junction and a high-temperature superconducting flux focusing pickup coil are independently designed, and then the high-temperature SQUID chip and the high-temperature superconducting flux focusing pickup coil are combined and fixed on a PCB substrate by gluing to form a high-temperature superconducting quantum interference device. Through this preparation method, the Josephson junction and the high-temperature superconducting flux focusing pickup coil will not be prepared on the same film layer, and since the preparation difficulty of the high-temperature superconducting flux focusing pickup coil is relatively small, the preparation yield of the high-temperature superconducting flux focusing pickup coil is greatly improved, and the loss of a large area of ​​yttrium barium copper oxide film caused by the difficulty of preparing the Josephson junction is greatly reduced, which can effectively reduce the cost of preparing the high-temperature superconducting quantum interference device. In addition, since there is no need to be limited by the Josephson junction preparation process, the size of the high-temperature superconducting flux focusing pickup coil can be further increased, thereby improving the detection sensitivity of the high-temperature superconducting quantum interference device. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0064] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a high-temperature superconducting quantum interference device, characterized in that: The preparation method at least comprises: Providing a substrate, and etching the substrate to form a through hole; epitaxially growing a buffer layer and a first superconducting film layer in sequence on the substrate by magnetron sputtering, and processing the buffer layer, the first high-temperature superconducting film layer and the substrate by micromachining technology to form a high-temperature superconducting magnetic flux focusing pickup coil; Providing a PCB substrate, fixing the high-temperature superconducting flux focusing pickup coil on the PCB substrate and fixing a high-temperature SQUID chip including a Josephson junction in the through hole; A signal connector is arranged on the top of the PCB substrate, and the signal connector is communicatively connected with an external device.

2. The method for preparing a high temperature superconducting quantum interference device according to claim 1, characterized in that: The micromachining process includes photolithography and ion beam etching.

3. The method for preparing a high temperature superconducting quantum interference device according to claim 1, characterized in that: The substrate is a silicon substrate, a magnesium oxide substrate or a sapphire substrate.

4. The method for preparing a high temperature superconducting quantum interference device according to claim 1, characterized in that: The first high temperature superconducting film layer is a yttrium barium copper oxide film layer and the thickness of the first high temperature superconducting film layer is 50 nm.

5. The method for preparing a superconducting quantum interference device according to claim 1, characterized in that: The through hole is in the shape of a square hole, and the through hole is located at the center of the substrate.

6. The method for preparing a superconducting quantum interference device according to claim 1, characterized in that: The substrate is in the shape of a square substrate, the size of the substrate is 20 mm, and the size of the through hole is 5 mm.

7. The method for preparing a superconducting quantum interference device according to claim 1, characterized in that: The Josephson junction in the high temperature SQUID chip includes two sub-Josephson junctions.

8. A high temperature superconducting quantum interference device prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The high temperature superconducting quantum interference device comprises: A substrate, wherein a square through hole is provided at the center of the substrate; A buffer layer and a first high-temperature superconducting film layer, wherein the buffer layer and the first high-temperature superconducting film layer are sequentially arranged on the substrate, and the buffer layer, the first high-temperature superconducting film layer and the substrate form a high-temperature superconducting magnetic flux focusing pickup coil; A high temperature SQUID chip containing a Josephson junction is embedded in the square through hole and fixed on the PCB substrate together with the high temperature superconducting flux focusing pickup coil; The signal connector is used to lead out the high-temperature superconducting flux focusing pickup coil and the high-temperature SQUID chip, and to communicate with external devices.

9. The superconducting quantum interference device according to claim 8, characterized in that: The first high temperature superconducting film layer is a yttrium barium copper oxide film layer and the thickness of the first high temperature superconducting film layer is 50 nm.

10. The superconducting quantum interference device according to claim 8, characterized in that: The size of the substrate was 20 mm and the size of the through hole was 5 mm.

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