阅读说明：本技术 二阶梯度重叠耦合型squid电流传感器以及制备方法 (Second-order gradient overlapping coupling SQUID current sensor and preparation method thereof ) 是由 徐达 李劲劲 钟青 王雪深 于 2021-08-24 设计创作，主要内容包括：本申请涉及一种二阶梯度重叠耦合型SQUID电流传感器以及制备方法。反馈线圈与输入线圈均绝缘设置于第一环路电极(SQUID环路的一部分)表面,形成了上下重叠耦合结构,使得输入线圈与SQUID环路的耦合更加匹配,增大了耦合系数。第一环路电极、第二环路电极、第三环路电极、第四环路电极、第一约瑟夫森结结构、第二约瑟夫森结结构之间并联连接,形成了二阶梯度并联电感结构的SQUID环路,可有效抵消外界磁场干扰。因此,通过二阶梯度重叠耦合型SQUID电流传感器,重叠耦合结构耦合系数大,有利于减弱外界磁场干扰,有利于输入线圈与SQUID环路的耦合匹配。(The application relates to a second-order gradient overlapping coupling SQUID current sensor and a preparation method thereof. The feedback coil and the input coil are arranged on the surface of a first loop electrode (part of the SQUID loop) in an insulating mode, and a vertically overlapped coupling structure is formed, so that the input coil and the SQUID loop are coupled more closely, and the coupling coefficient is increased. The first loop electrode, the second loop electrode, the third loop electrode, the fourth loop electrode, the first Josephson junction structure and the second Josephson junction structure are connected in parallel, so that a SQUID loop of a second-order gradient parallel inductance structure is formed, and external magnetic field interference can be effectively counteracted. Therefore, the second-order gradient overlapping coupling type SQUID current sensor has a large overlapping coupling coefficient, so that the external magnetic field interference can be weakened, and the coupling matching between the input coil and the SQUID loop can be facilitated.)

1. A second-order gradient overlap-coupled SQUID current sensor, comprising:

a first loop electrode;

the input loop is arranged on the surface of the first loop electrode, and the input loop and the first loop electrode are arranged in an insulating way;

the input loop is used for inputting superconducting transition edge detector signals; and

and the feedback coil and the input loop are arranged on the surface of the first loop electrode at intervals, the feedback coil and the first loop electrode are arranged in an insulating way, and the feedback coil is used for magnetic flux locking.

2. The second order gradient overlap coupling SQUID current sensor according to claim 1, further comprising a second loop electrode, a third loop electrode, and a fourth loop electrode, the first loop electrode, the second loop electrode, the third loop electrode, and the fourth loop electrode being sequentially arranged in a clockwise direction;

the second loop electrode is rotated 90 ° relative to the first loop electrode;

the third loop electrode is rotated 180 ° relative to the first loop electrode;

the fourth loop electrode is rotated 270 ° relative to the first loop electrode.

3. The second order gradient overlap-coupled SQUID current sensor according to claim 2,

the first end of the first loop electrode is connected with the first end of the second loop electrode through a first connecting structure;

the second end of the first loop electrode is connected with the second end of the second loop electrode through a second connecting structure;

the first end of the third loop electrode is connected with the first end of the fourth loop electrode through a third connecting structure;

and the second end of the third loop electrode is connected with the second end of the fourth loop electrode through a fourth connecting structure.

4. The second order gradient overlap coupled SQUID current sensor according to claim 3, wherein said second order gradient overlap coupled SQUID current sensor comprises:

a first Josephson junction structure connected to the first and fourth connection structures through fifth connection structures, respectively;

a second josephson junction structure is connected to the second connection structure and the third connection structure, respectively, by a sixth connection structure.

5. The second order gradient overlap-coupled SQUID current sensor according to claim 4, wherein the first and second josephson junction structures are disposed at intervals at geometric center positions formed by the first, second, third and fourth loop electrodes.

6. The second order gradient overlap-coupled SQUID current sensor according to claim 2, wherein the feedback coil is disposed near an edge of the first loop electrode away from a point of symmetry;

the feedback coil is disposed proximate an edge of the second loop electrode proximate the point of symmetry;

the feedback coil is arranged close to the edge of the third loop electrode far away from the symmetrical point;

the feedback coil is disposed near an edge of the fourth loop electrode near the point of symmetry.

7. The second order gradient overlap-coupled SQUID current sensor according to claim 2, wherein the input loop comprises:

a first input loop;

a second input loop having a radius greater than a radius of the first input loop;

a third input loop (330) having a radius greater than a radius of the second input loop.

8. The second order gradient overlap-coupled SQUID current sensor according to claim 7, wherein the feedback coil and the third input loop are disposed to surround the first loop electrode.

9. The second-order gradient overlap-coupled SQUID current sensor according to claim 8, wherein the first input loop, the second input loop, and the third input loop are sequentially connected end-to-end to form a first input structure;

the second-order gradient overlapping coupling SQUID current sensor comprises a plurality of first input structures which are sequentially connected end to end, and each first input structure is respectively arranged on the surface of the first loop electrode, the surface of the second loop electrode, the surface of the third loop electrode and the surface of the fourth loop electrode.

10. A preparation method of a second-order gradient overlapping coupling SQUID current sensor is characterized by comprising the following steps:

providing a substrate, and preparing a silicon dioxide film on the surface of the substrate;

sequentially preparing a first superconducting thin film layer, a first insulating layer and a second superconducting thin film layer on the surface of the silicon dioxide thin film, which is far away from the substrate;

etching the second superconducting film layer to the first insulating layer to form a second superconducting film structure;

etching the first insulating layer until the first layer of superconducting thin film is etched to form a first insulating structure, wherein the first insulating structure covers the second superconducting thin film structure;

etching the first superconducting thin film layer until the silicon dioxide thin film is etched to form a loop electrode and a first superconducting thin film structure;

preparing a second insulating layer on the surface of the silicon dioxide film, the surfaces of the loop electrodes with different radiuses, the surface of the first insulating structure and the surface of the second superconducting thin film structure;

etching the second insulating layer until the loop electrode and the second superconducting thin film structure are respectively etched to form a plurality of connecting through holes and a second insulating structure;

preparing a terminal resistor on the surface of the second insulating structure among the plurality of connecting through holes;

depositing a lead superconducting thin film layer on the surfaces of the connecting through holes and the second insulating structure;

and etching the lead superconducting film layer until reaching the second insulation structure to form a feedback coil, an input coil and a connection structure.

Technical Field

The application relates to the technical field of electronics, in particular to a second-order gradient overlapping coupling SQUID current sensor and a preparation method thereof.

Background

The superconducting quantum interferometer (SQUID) can be used for signal readout of low-noise detectors such as superconducting transition edge detectors (TESs) and magnetic metal micro-energy devices (MMC). The TES detector has wide application in the fields of space astronomy, high-energy physics, quantum information, photon measurement and the like, can be used as a bolometer for detecting millimeter waves, can also be used as a micro-energy device for detecting X rays, and can also be used as a single photon detector for detecting visible light. The SQUID current sensor is required for signal readout of all different types of TES detectors of different wavebands.

However, SQUID current sensors are highly susceptible to interference from external magnetic fields during operation and are often operated with TES detectors in environments where no or poor magnetic shielding is available. The traditional SQUID current sensor adopts a structure of cross coupling of a SQUID loop, an input coil and a feedback coil, so that the coupling coefficient is small, the inductance of the input coil is large in nH-muH magnitude, and coupling matching of the input coil and the SQUID loop is not facilitated.

Disclosure of Invention

In view of the above, it is necessary to provide a second-order gradient overlap coupling SQUID current sensor and a manufacturing method thereof.

The application provides a second order gradient overlapping coupling type SQUID current sensor, which comprises a first loop electrode, an input loop and a feedback coil. The input loop is arranged on the surface of the first loop electrode. The input loop and the first loop electrode are arranged in an insulating mode. The input loop is used for inputting superconducting transition edge detector signals. The feedback coil and the input loop are arranged on the surface of the first loop electrode at intervals. The feedback coil is insulated from the first loop electrode. The feedback coil is used for flux locking.

In one embodiment, the present application provides a method for manufacturing a second-order gradient overlap-coupled SQUID current sensor, comprising:

providing a substrate, and preparing a silicon dioxide film on the surface of the substrate;

sequentially preparing a first superconducting thin film layer, a first insulating layer and a second superconducting thin film layer on the surface of the silicon dioxide thin film, which is far away from the substrate;

etching the second superconducting film layer to the first insulating layer to form a second superconducting film structure;

etching the first insulating layer until the first layer of superconducting thin film is etched to form a first insulating structure, wherein the first insulating structure covers the second superconducting thin film structure;

etching the first superconducting thin film layer until the silicon dioxide thin film is etched to form a plurality of loop electrodes with different radiuses;

preparing a second insulating layer on the surface of the silicon dioxide film, the surfaces of the loop electrodes with different radiuses, the surface of the first insulating structure and the surface of the second superconducting thin film structure;

etching the second insulating layer until the loop electrode and the second superconducting thin film structure are respectively etched to form a plurality of connecting through holes and a second insulating structure;

preparing a terminal resistor on the surface of the second insulating structure among the plurality of connecting through holes;

depositing a lead superconducting thin film layer on the surfaces of the connecting through holes and the second insulating structure;

and etching the lead superconducting film layer until reaching the second insulation structure to form a feedback coil, an input coil and a connection structure.

According to the second-order gradient overlapping coupling SQUID current sensor and the preparation method thereof, the structure of the input loop can be a polygonal structure, and the input coil is formed. The input coil is connected to a superconducting transition edge detector (TES) for inputting a TES signal. The feedback coil is used for being connected with a test system, namely connected with the magnetic flux locking ring, and is used for carrying out magnetic flux locking, so that a stable magnetic field environment is provided for the input coil, and interference to the detection process is avoided.

The feedback coil and the input coil are both arranged on the surface of the first loop electrode (part of the SQUID loop) in an insulating mode, and a vertically overlapped coupling structure is formed. The structures are separated by insulation to avoid the crosstalk of circulating currents between each other. At this time, the feedback coil, the input loop (a part of the input coil), and the SQUID loop are independent of each other. Therefore, the coupling of the input coil and the SQUID loop is more matched through the upper and lower overlapped coupling structures, and the coupling coefficient is increased.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a second-order gradient overlap coupling SQUID current sensor provided in an embodiment.

Fig. 2 is a schematic structural diagram of a second-order gradient overlap-coupled SQUID current sensor provided in an embodiment.

Fig. 3 is a schematic circuit diagram of a second-order gradient overlap-coupled SQUID current sensor provided in an embodiment;

figure 4 is a cross-sectional schematic diagram of a second order gradient overlap coupled SQUID current sensor provided in an embodiment;

fig. 5 is a schematic cross-sectional view of a second-order gradient overlap-coupled SQUID current sensor provided in an embodiment.

Description of reference numerals:

a second order gradient overlap coupling SQUID current sensor 100, a first loop electrode 20, a first input structure 30, a first input loop 310, a second input loop 320, a third input loop 330, a feedback coil 40, a second loop electrode 50, a third loop electrode 60, a fourth loop electrode 70, a first connection structure 810, a second connection structure 820, a third connection structure 830, a fourth connection structure 840, a first Josephson junction structure 910, a second Josephson junction structure 920, fifth connection structure 850, sixth connection structure 860, seventh connection structure 870, eighth connection structure 880, substrate 10, silicon dioxide film 110, second superconducting thin film structure 120, first insulation structure 130, connection via 140, second insulation structure 150, first superconducting thin film structure 160, termination resistor 670, resistor connection structure 671, positive connection structure 610, and negative connection structure 921.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and/or sections, these elements, components, regions, layers, doping types and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or section from another element, component, region, layer, doping type or section. Thus, a first element, component, region, layer, doping type or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application; for example, the first doping type may be made the second doping type, and similarly, the second doping type may be made the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

Spatial relational terms, such as "under," "below," "under," "over," 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 the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein interpreted accordingly.

As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, in this specification, the term "and/or" includes any and all combinations of the associated listed items.

Embodiments of the application are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments (and intermediate structures) of the application, such that variations from the shapes shown are to be expected due to, for example, manufacturing techniques and/or tolerances. Thus, embodiments of the present application should not be limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing techniques. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present application.

Referring to fig. 1, the present application provides a second-order gradient overlap-coupled SQUID current sensor 100 including a first loop electrode 20, an input loop 30, and a feedback coil 40. The input loop 30 is disposed on the surface of the first loop electrode 20. The input loop 30 is insulated from the first loop electrode 20. The input loop 30 is used to input superconducting transition edge detector signals. The feedback coil 40 is disposed on the surface of the first loop electrode 20 at a distance from the input loop 30. The feedback coil 40 is provided in an insulated manner from the first loop electrode 20. The feedback coil 40 is used for flux locking.

In this embodiment, the first loop electrode 20, the feedback coil 40 and the input coil are all made of superconducting thin film materials. The first loop electrode 20 has a regular polygonal structure, such as a regular hexagon, a regular octagon, etc. The first loop electrode 20 forms a geometric center. The structure of the input loop is also a polygonal structure, forming the input coil. The input coil is connected to a superconducting transition edge detector (TES) for inputting a TES signal. The feedback coil 40 is used for being connected with a test system, namely, a magnetic flux locking ring, and is used for carrying out magnetic flux locking, so that a stable magnetic field environment is provided for the input coil, and interference is avoided in the detection process.

The feedback coil 40 and the input coil are both insulated and arranged on the surface of the first loop electrode 20 (part of the SQUID loop), and form a vertically overlapped coupling structure with the SQUID loop. The structures are separated by insulation to avoid the crosstalk of circulating currents between each other. At this time, the feedback coil 40, the input loop 30 (a part of the input coil), and the SQUID loop are independent of each other. Therefore, the coupling of the input coil and the SQUID loop is more matched through the upper and lower overlapped coupling structures, and the coupling coefficient is increased.

In one embodiment, the second order gradient overlap-coupled SQUID current sensor 100 further includes a second loop electrode 50, a third loop electrode 60, and a fourth loop electrode 70. The first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70 are sequentially disposed in a clockwise direction. The second loop electrode 50 is rotated 90 deg. relative to the first loop electrode 20. The third loop electrode 60 is rotated 180 ° relative to the first loop electrode 20. The fourth loop electrode 70 is rotated 270 deg. relative to the first loop electrode 20.

In this embodiment, the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70 are the same. The first loop electrode 20 and the third loop electrode 60 are disposed on a diagonal line, and the second loop electrode 50 and the fourth loop electrode 70 are disposed on a diagonal line. At this time, the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70 are sequentially and symmetrically disposed in a clockwise direction to form a regular quadrangle by surrounding, and the four loop electrodes are respectively located at four vertexes of the regular quadrangle, so that mutual symmetry is achieved. Therefore, the interference generated by the symmetrical structure can be mutually offset.

In one embodiment, the first loop electrode 20 has a first end and a second end disposed opposite to each other. A first end of the first loop electrode 20 is connected to a first end of the second loop electrode 50 by a first connection structure 810. A second end of the first loop electrode 20 is connected to a second end of the second loop electrode 50 by a second connecting structure 820. At this time, the first and second loop electrodes 20 and 50 are connected in parallel by the first and second connection structures 810 and 820.

The first end of the third loop electrode 60 and the first end of the fourth loop electrode 70 are connected by a third connecting structure 830. A second end of the third loop electrode 60 and a second end of the fourth loop electrode 70 are connected by a fourth connecting structure 840. At this time, the third and fourth loop electrodes 60 and 70 are connected in parallel by the third and fourth connection structures 830 and 840.

In this embodiment, the first loop electrode 20 has a first end and a second end opposite to each other, and may also be understood as a head end and a tail end. At this time, an opening is formed between the first end and the second end shown in fig. 2, and the connection end of the first input loop 310 in each of the first input structures 30 is led out from the opening, and a plurality of the first input structures 30 are connected in series to form the input coil.

The first connection structure 810 and the second connection structure 820 are disposed in parallel between the first loop electrode 20 and the second loop electrode 50, and are connected in parallel to form a symmetrical structure with respect to a vertical direction. The third connecting structure 830 and the fourth connecting structure 840 are disposed in parallel between the third loop electrode 60 and the fourth loop electrode 70, and are connected in parallel to form a symmetrical structure with respect to a vertical direction. The parallel structure of the third loop electrode 60 and the fourth loop electrode 70 and the parallel structure of the first loop electrode 20 and the second loop electrode 50 are symmetrically arranged with respect to a horizontal line. Therefore, the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70 form a mutually symmetrical structure. In addition, the first loop electrode 20 and the second loop electrode 50 are connected in parallel, and the third loop electrode 60 and the fourth loop electrode 70 are connected in parallel, so that a second-order gradient structure of the SQUID loop can be formed, and external magnetic field interference can be effectively counteracted.

Referring to fig. 1 and 3, in one embodiment, the second order gradient overlap coupling SQUID current sensor 100 includes a first josephson junction structure 910 and a second josephson junction structure 920. The first josephson junction structure 910 is connected with the first connection structure 810 and the fourth connection structure 840 through a fifth connection structure 850, respectively. The second josephson junction structure 920 is connected to the second connection structure 820 and the third connection structure 830 through a sixth connection structure 860, respectively.

In this embodiment, the first superconducting thin film structure 160 (lower Nb film) of the first josephson junction structure 910 is connected to the first connection structure 810 and the fourth connection structure 840, respectively. The first superconducting thin film structure 160 (lower Nb film) of the second josephson junction structure 920 is connected to the second connection structure 820 and the third connection structure 830, respectively, to form a SQUID loop in which two josephson junctions are connected in parallel. The SQUID loop formed by the parallel connection of two josephson junctions is converted into a circuit structure as shown in fig. 3.

And, a parallel inductance structure is formed between the two josephson junctions by a parallel structure formed by the first loop electrode 20, the second loop electrode 50, the third loop electrode 60 and the fourth loop electrode 70. Thus, the coupling area with the input coil and the feedback coil 40 is increased by means of the parallel inductance of the SQUID loop.

Therefore, the SQUID loop of the second-order gradient parallel inductance structure formed by the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, the fourth loop electrode 70, the first josephson junction structure 910 and the second josephson junction structure 920 can effectively cancel the external magnetic field interference. And the SQUID loop is respectively coupled with the input coil and the feedback coil 40 in an up-down coupling mode, so that the coupling of the input coil and the SQUID loop is more matched, and the coupling coefficient is increased.

In one embodiment, the first josephson junction structure 910 and the second josephson junction structure 920 are spaced apart from each other at a geometric center formed by the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70.

In this embodiment, the four loop electrodes are respectively located at four vertices of the regular quadrilateral, and surround to form a square space. The first josephson junction structure 910 and the second josephson junction structure 920 are disposed in parallel and spaced at the geometric center of a square. At this time, the structures formed among the first josephson junction structure 910, the second josephson junction structure 920, the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70 are symmetrical to each other, and the influence of the structures itself can be cancelled out.

Referring to fig. 1, in one embodiment, the feedback coil 40 is disposed near an edge of the first loop electrode 20 away from the symmetry point. The feedback coil 40 is disposed near an edge of the second loop electrode 50 near the point of symmetry. The feedback coil 40 is disposed near an edge of the third loop electrode 60 away from the point of symmetry. The feedback coil 40 is disposed near the edge of the fourth loop electrode 70 near the point of symmetry.

In this embodiment, the feedback coil 40 is a loop coil marked by a dotted line shown in fig. 2. The feedback coil 40 is disposed near an edge of the first loop electrode 20 away from the point of symmetry. In this case, the feedback coil 40 and the third input loop 330 surround the first loop electrode 20, and form a vertically overlapping coupling structure. Meanwhile, the feedback coil 40 and the third input loop 330 form a symmetrical structure. Through the structural arrangement of the feedback coil 40 about the symmetrical point, the structure of the current sensor 100 can be more symmetrical, and the influence generated by the structure of the current sensor can be mutually offset.

In one embodiment, the plurality of input loops includes a first input loop 310, a second input loop 320, and a third input loop 330. The first input loop 310 is disposed at the first loop electrode 20. The second input loop 320 surrounds the first input loop 310. The third input loop 330 surrounds the second input loop 320. The radius of the second input loop 320 is greater than the radius of the first input loop 310. The radius of the third input loop 330 is greater than the radius of the second input loop 320.

In this embodiment, a plurality of geometric centers of the first input loop 310, the second input loop 320, and the third input loop 330 are overlapped, and a structure is formed on the surface of the first loop electrode 20, which is spaced outward from the center point in sequence. A plurality of input loops are connected in series end to end in sequence to form an integral input coil. Therefore, the upper and lower overlapping coupling structure of the input coil and the first loop electrode 20 enables the coupling of the input coil and the SQUID loop to be more matched, and the coupling coefficient is increased. Furthermore, when the input current in the input coil changes, the SQUID loop can more accurately reflect the change situation, and is more beneficial to reading TES signals.

In one embodiment, the first input loop 310, the second input loop 320, and the third input loop 330 are serially connected end to end in sequence to form the first input structure 30. The second-order gradient overlap-coupled SQUID current sensor 100 includes a plurality of the first input structures 30 connected in series end to end in this order. Each of the first input structures 30 is disposed on a surface of the first loop electrode 20, a surface of the second loop electrode 50, a surface of the third loop electrode 60, and a surface of the fourth loop electrode 70, respectively.

In this embodiment, each of the first input structures 30 is disposed in one-to-one correspondence with the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70. The first input structures 30 are sequentially connected end to end in series to form the input coil. The input coil is connected with the TES and used for inputting TES signals. When the TES signal is input, the input current in the input coil changes, causing a change in the magnetic field. At the moment, the SQUID loop enters a resistance state under the action of a bias magnetic field, the SQUID loop forms voltage bias, the change condition of TES signals is further obtained, and the signal reading of the TES detector is realized.

Each of the first input structures 30 is disposed on the surface of the first loop electrode 20, the surface of the second loop electrode 50, the surface of the third loop electrode 60, and the surface of the fourth loop electrode 70, respectively, to form a vertically overlapped coupling structure, so that the coupling between the input coil and the SQUID loop is more matched, and the coupling coefficient is increased.

In one embodiment, the current sensor 100 further includes seventh and eighth connecting structures 870, 880. The seventh connecting structure 870 is disposed between the first connecting structure 810 and the second connecting structure 820. Two of the first input structures 30 are connected in series by the seventh connecting structure 870. The eighth connecting structure 880 is disposed between the third connecting structure 830 and the fourth connecting structure 840. Two of said first input structures 30 are connected in series by said eighth connecting structure 880.

In this embodiment, the first connecting structure 810, the seventh connecting structure 870 and the second connecting structure 820 are respectively and symmetrically disposed with respect to a horizontal line with respect to the third connecting structure 830, the eighth connecting structure 880 and the fourth connecting structure 840. The first input structure 30 disposed on the surface of the first loop electrode 20 and the first input structure 30 disposed on the surface of the second loop electrode 50 are sequentially connected in series end to end through the seventh connecting structure 870. The first input structures 30 disposed on the surface of the third loop electrode 60 and the first input structures 30 disposed on the surface of the fourth loop electrode 70 are sequentially connected in series end to end through the eighth connecting structure 880.

In one embodiment, the input end a of the input coil (shown in fig. 1) and the input end B of the feedback coil 40 formed by connecting a plurality of the first input structures 30 in series in sequence are disposed on two sides of a vertical line and are symmetrically disposed about the vertical line.

Referring to fig. 2, in one embodiment, the current sensor 100 further includes a plurality of termination resistors 670, symmetrically disposed about a horizontal line, respectively disposed on two sides of the first josephson junction structure 910 and the second josephson junction structure 920.

Two of the termination resistors 670 are connected in parallel with the first josephson junction structure 910, respectively. Wherein, one end of the termination resistor 670 is connected to the fifth connection structure 850, thereby realizing connection with the upper Nb film of the first josephson junction structure 910. The other end of the termination resistor 670 is connected to the lower Nb film of the first josephson junction structure 910 through a resistor connection structure 671 to form a parallel connection structure.

Similarly, the two termination resistors 670 are respectively connected in parallel with the second josephson junction structure 920. One end of the termination resistor 670 is connected to the sixth connection structure 860, so as to achieve connection to the upper Nb film of the second josephson junction structure 920. The other end of the termination resistor 670 is connected to the lower Nb film of the second josephson junction structure 920 through a resistor connection structure 671, forming a parallel connection structure.

A complete second order gradient parallel SQUID loop is formed by the four termination resistors 670, the first josephson junction structure 910, the second josephson junction structure 920, the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, and the fourth loop electrode 70.

In one embodiment, the positive connection structure 610 is drawn through the third loop electrode 60, and the negative connection structure 921 is drawn through the first superconducting thin film structure (lower Nb film) of the first josephson junction structure 910 and the first superconducting thin film structure (lower Nb film) of the second josephson junction structure 920. Through positive pole connection structure 610 with the positive negative pole that negative pole connection structure 921 can connect the power realizes the detection to the voltage of SQUID loop, and then obtains TES signal's situation of change, has realized TES detector signal and has read out.

In one embodiment, an insulating structure is disposed between the fifth connecting structure 850 and the seventh connecting structure 870, the eighth connecting structure 880, the second connecting structure 820, and the third connecting structure 830, respectively, for separation. The feedback coil 40, the input coil, and the SQUID loop are independent of each other.

Referring to fig. 4 and 5, in an embodiment, the present application provides a method for manufacturing a second-order gradient overlap-coupled SQUID current sensor, including:

s10, providing a substrate 10, and preparing a silicon dioxide film 110 on the surface of the substrate 10;

s20, preparing a first superconducting thin film layer, a first insulating layer and a second superconducting thin film layer on the surface of the silicon dioxide thin film 110 far away from the substrate 10 in sequence;

s30, etching the second layer of superconducting thin film to the first insulating layer to form a second superconducting thin film structure 120;

s40, etching the first insulating layer to the first superconducting thin film to form a first insulating structure 130, where the first insulating structure 130 covers the second superconducting thin film structure 120;

s50, etching the first superconducting thin film layer until the silicon dioxide thin film 110 is etched, and forming a loop electrode and a first superconducting thin film structure 160;

s60, preparing a second insulating layer on the surface of the silicon dioxide thin film 110, the surfaces of the plurality of loop electrodes with different radii, the surface of the first insulating structure 130, and the surface of the second superconducting thin film structure 120;

s70, etching the second insulating layer to the loop electrode and the second superconducting thin film structure 120, respectively, to form a plurality of connecting vias 140 and a second insulating structure 150;

s80, preparing a termination resistor 670 on the surface of the second insulating structure 150 between the plurality of connection vias 140;

s90, depositing a lead superconducting thin film layer on the surfaces of the plurality of connection vias 140 and the second insulation structure 150;

s100, etching the lead superconducting thin film layer to the second insulating structure 150 to form the feedback coil 40, the input coil and the connecting structure.

In this embodiment, in S20, a first superconducting thin film layer (lower Nb film) and a first insulating layer (AlO) were sequentially prepared by a magnetron sputtering method_x) And a second superconducting thin film layer (upper Nb film) forming Nb/AlO_xa/Nb three-layer film. In S30 and S40, the second superconducting thin film and the first insulating layer are etched to form the second superconducting thin film structure 120 and the first insulating structure 130, respectively. In the S40, the first insulating layer is aluminum oxide (AlO)_x) Wet etching is performed on the first insulating layer (alumina) so that the first insulating structure 130 completely covers the second superconducting thin film structure 120. It is understood that the area of the first insulating structure 130 is larger than that of the second superconducting thin film structure 120. The first insulating structure 130 covers the second superconducting thin film structure 120, so that the formed Nb/AlO can be ensured_xthe/Nb Josephson junction area does not leak laterally, which is beneficial to the quality stability of the Josephson junction in the SQUID loop.

In S50, the first superconducting thin film layer is etched to form a SQUID loop pattern and a first superconducting thin film structure 160 of a josephson junction. At this time, it can be understood that the first superconducting thin film structure 160 and the SQUID loop pattern are all formed by etching the first superconducting thin film layer. The SQUID loop pattern is as shown in fig. 2 for the first loop electrode 20, the second loop electrode 50, the third loop electrode 60, the fourth loop electrode 70, the first connection structure 810, the seventh connection structure 870, the second connection structure 820, the third connection structure 830, the eighth connection structure 880, the fourth connection structure 840, etc.

In S70, a plurality of the connecting vias 140 are used to deposit Nb films. At this time, the Nb film is electrically connected to the loop electrode through the connection via 140. Wherein the positive electrode connection structure 610 in fig. 2 can be drawn out through the connection via 140. The Nb film can realize electrical connection with the second superconducting thin film structure 120 (the upper Nb film of the josephson junction) through the connection via 140. Wherein the negative connection structure 921 in fig. 2 can be drawn through the connection via 140. Meanwhile, the second insulating structure 150 can achieve the isolation and insulation function between the overlapped structures in fig. 2. In S80, a plurality of termination resistors 670 (see the structure in fig. 2) are disposed near the josephson junction as termination resistors of the current sensor 100.

In S90, depositing a lead superconducting thin film layer on the surfaces of the plurality of connection through holes 140 and the second insulating structure 150, where the lead superconducting thin film layer is an Nb film. In S100, the lead superconducting thin film layer (Nb film) is etched to form the feedback coil 40, the input coil, and the connection structure. Wherein the connection structures are as described for resistive connection structure 671, said fifth connection structure 850, said sixth connection structure 860, etc. in fig. 1 and 2.

Therefore, by the preparation method of the second-order gradient overlap coupling type SQUID current sensor, the first insulating structure 130 covers the second superconducting thin film structure 120, so that no side leakage of a josephson junction region can be ensured, and the quality stability of the josephson junction in the SQUID is facilitated. Meanwhile, the current sensor 100 is prepared by the preparation method of the second-order gradient overlapping coupling SQUID current sensor, so that the coupling area can be increased, the external magnetic field interference can be effectively counteracted, the parasitic capacitance can be reduced, and the reading of TES signals can be facilitated.

In one embodiment, the thickness of the silicon dioxide thin film 110 is 100nm to 1000 nm. The thickness of the first superconducting thin film layer (lower Nb film) is 100 nm-500 nm. The thickness of the first insulating layer (AlOx) is 5nm to 30 nm. The thickness of the second superconducting thin film layer (upper Nb film) is 100 nm-500 nm. The thickness of the second insulating structure 150 is 200nm to 600 nm. The thickness of the termination resistor 670(PdAu thin film) is 50nm to 500 nm. The thickness of the lead superconducting thin film layer (Nb film) is 300 nm-800 nm.

In one embodiment, the Nb/AlO is prepared by magnetron sputtering_xIn the case of the Nb three-layer film, the oxidation pressure of the AlOx film is 100mTorr to 5000mTorr, and the oxidation time is 5 hours to 24 hours. The Josephson junction area is 1 μm²～100μm²。

Specifically, in one embodiment, the method for manufacturing the second-order gradient overlap-coupled SQUID current sensor includes:

growing SiO with the thickness of 100nm₂Preparing Nb/AlO on 2-inch monocrystal high-resistance silicon wafer 10 of film 110 by magnetron sputtering method_xThe thickness of the/Nb three-layer film is respectively 100nm, 5nm and 100 nm. Wherein, the AlO is prepared by adopting a magnetron sputtering method_xThe membrane was prepared using an oxidation gas pressure of 100mTorr and an oxidation time of 5 hours.

In the aboveCarrying out first photoetching on the basis of the steps, and etching the upper Nb film to obtain the Nb film with the area of 1 mu m²And a top layer pattern 120 of josephson junction regions.

Performing second photoetching on the basis of the steps, and etching the intermediate AlOx film by adopting wet etching to form AlO_xStructure 130. Wherein, AlO_xStructure 130 completely covers upper layer pattern 120.

And carrying out third photoetching on the basis of the steps, and etching the Nb film at the lowest layer to obtain the SQUID loop pattern.

On the basis of the steps, the SiO with the thickness of 200nm is grown by adopting a low-temperature chemical vapor deposition method₂A thin film is etched, and then a third photoetching is carried out, and SiO is etched₂And (5) thin film forming, so as to obtain a through hole connection structure 140 of the Nb wire layer and the Nb film at the lower layer. The remaining SiO₂The thin film is the second insulating structure 150.

And performing fourth photoetching on the substrate, preparing a PdAu film with the thickness of 50nm as a resistance layer by adopting an electron beam evaporation method, and stripping to obtain the PdAu resistor 670.

On the basis of the steps, a 300nm thick Nb film is deposited by adopting a magnetron sputtering method, then, fifth photoetching is carried out, and the Nb film is etched, so that the feedback coil 40, the input coil and the connecting structure pattern are obtained.

And scribing the 2-inch sample on the basis of the steps to obtain the second-order gradient overlap coupling SQUID current sensor.

In one embodiment, the method for manufacturing the second-order gradient overlap-coupled SQUID current sensor includes:

growing SiO with the thickness of 1000nm₂Preparing Nb/AlO on 2-inch monocrystal high-resistance silicon wafer 10 of film 110 by magnetron sputtering method_xThe thickness of the/Nb three-layer film is respectively 500nm, 30nm and 500 nm. Wherein, the AlO is prepared by adopting a magnetron sputtering method_xIn the case of a film, the film was prepared under an oxidation pressure of 5000mTorr for 24 hours.

Performing first photoetching on the basis of the steps, and etching the upper Nb film to obtain the Nb-based film with the area of 100 mu m²And a top layer pattern 120 of josephson junction regions.

Performing second photoetching on the basis of the steps, and etching the intermediate layer AlO by adopting wet etching_xFilm of forming AlO_xStructure 130. Wherein, AlO_xStructure 130 completely covers upper layer pattern 120.

And carrying out third photoetching on the basis of the steps, and etching the Nb film at the lowest layer to obtain the SQUID loop pattern.

On the basis of the steps, growing SiO with the thickness of 600nm by adopting a low-temperature chemical vapor deposition method₂A thin film is etched, and then a third photoetching is carried out, and SiO is etched₂And (5) thin film forming, so as to obtain a through hole connection structure 140 of the Nb wire layer and the Nb film at the lower layer. The remaining SiO₂The thin film is the second insulating structure 150.

And performing fourth photoetching on the substrate, preparing a PdAu film with the thickness of 500nm as a resistance layer by adopting an electron beam evaporation method, and stripping to obtain the PdAu resistor 670.

On the basis of the steps, an Nb film with the thickness of 800nm is deposited by adopting a magnetron sputtering method, then, fifth photoetching is carried out, and the Nb film is etched, so that the feedback coil 40, the input coil and the connecting structure pattern are obtained.

And scribing the 2-inch sample on the basis of the steps to obtain the second-order gradient overlap coupling SQUID current sensor.

In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features of the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.