First-order gradient parallel SQUID current sensor array and preparation method

Abstract

The present application relates to a first-order gradient parallel SQUID current sensor array and a preparation method. Two Josephson junction structures are arranged at intervals on a loop electrode to form a SQUID loop. Each loop electrode forms a closed loop. A parallel inductance structure is formed between the two Josephson junction structures in each SQUID loop, which can reduce the SQUID loop inductance, make the critical current range of the SQUID wider when working, and effectively offset the external magnetic field interference. A SQUID loop formed by a loop electrode, a first Josephson junction structure and a second Josephson junction structure adopts a simple first-order gradient structure, which is conducive to reducing external magnetic field interference. The negative connection structure corresponding to a loop electrode is connected to the positive connection structure corresponding to an adjacent loop electrode, so that multiple SQUID loops are connected in series to form a first-order gradient parallel SQUID current sensor array.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to a first-order gradient parallel SQUID current sensor array and a preparation method thereof. Background Art

[0002] The superconducting quantum interference device (SQUID) is a precision instrument for measuring current and magnetic field. It has extremely high current sensitivity and magnetic field sensitivity and can be used for signal readout of low-noise detectors such as superconducting transition edge detectors (TES) and magnetic metal microcalorimeters (MMC).

[0003] Superconducting transition edge detectors (TES detectors) can be used as bolometers for millimeter wave detection, as microcalorimeters for X-ray detection, and as single-photon detectors for visible light. Although high-performance TES detectors offer high sensitivity, their noise levels are low, resulting in weak output signals. Signal readout requires a SQUID current sensor with high current sensitivity and a matching noise level.

[0004] SQUID current sensors are highly susceptible to interference from external magnetic fields during operation, and they often operate alongside TES detectors in environments with no or poor magnetic shielding. Therefore, SQUID current sensors must be designed with a gradient structure to mitigate the effects of external magnetic fields. However, conventional SQUID current sensor arrays often employ a series structure, resulting in a narrow critical current range during SQUID operation, making it difficult to offset external magnetic field interference. Summary of the Invention

[0005] Based on this, it is necessary to provide a first-order gradient parallel SQUID current sensor array and a preparation method to address the above problems.

[0006] The present application provides a first-order gradient parallel SQUID current sensor array. The first-order gradient parallel SQUID current sensor array includes multiple loop electrodes, multiple first Josephson junction structures, multiple second Josephson junction structures, multiple positive electrode connection structures, and multiple negative electrode connection structures. The multiple loop electrodes form a closed loop. The first superconducting thin film structure of each first Josephson junction structure is disposed on each loop electrode. The first superconducting thin film structure of each second Josephson junction structure is disposed on each loop electrode. The first Josephson junction structure and the second Josephson junction structure are spaced apart. Each positive electrode connection structure is connected to each loop electrode. Each negative electrode connection structure is respectively connected to the second superconducting thin film structure of the first Josephson junction structure and the second superconducting thin film structure of the second Josephson junction structure. The negative electrode connection structure corresponding to one loop electrode is connected to the positive electrode connection structure corresponding to an adjacent loop electrode.

[0007] In one embodiment, the first-order gradient parallel SQUID current sensor array further includes an input coil. The input coil is disposed on a surface of the plurality of loop electrodes and is insulated from the plurality of loop electrodes. The input coil is configured to input a superconducting transition edge detector signal.

[0008] In one embodiment, each of the loop electrodes includes a first loop electrode and a second loop electrode. The first end of the second loop electrode is connected to the first end of the first loop electrode. The second end of the second loop electrode is connected to the second end of the first loop electrode. The first loop electrode and the second loop electrode form a closed loop.

[0009] In one embodiment, the first superconducting thin film structure of each first Josephson junction structure is disposed at a first end of each first loop electrode, and the first superconducting thin film structure of each second Josephson junction structure is disposed at a second end of each first loop electrode.

[0010] In one embodiment, each of the first Josephson junction structures and each of the second Josephson junction structures are arranged on the same horizontal line, and each of the first loop electrodes and each of the second loop electrodes are arranged symmetrically about the horizontal line.

[0011] In one embodiment, the input coil includes a first input loop and a second input loop. The first input loop is insulated and disposed on the surface of the plurality of first loop electrodes. The second input loop is insulated and disposed on the surface of the plurality of second loop electrodes. The first and second input loops are connected end-to-end to form the input coil.

[0012] In one embodiment, each of the first Josephson junction structures and each of the second Josephson junction structures are symmetrically arranged about a vertical line, and each of the loop electrodes is symmetrically arranged about the vertical line.

[0013] In one embodiment, the first-order gradient parallel SQUID current sensor array further includes a plurality of first terminal resistors and a plurality of second terminal resistors. Each of the first terminal resistors is connected in parallel to each of the first Josephson junctions. Each of the second terminal resistors is connected in parallel to each of the second Josephson junction structures.

[0014] In one embodiment, each of the first terminal resistors and each of the second terminal resistors are symmetrically arranged about the vertical line.

[0015] In one embodiment, the present application provides a method for preparing a first-order gradient parallel SQUID current sensor array, comprising:

[0016] Providing a substrate, and preparing a silicon dioxide film on the surface of the substrate;

[0017] Sequentially forming a first superconducting thin film layer, a first insulating layer, and a second superconducting thin film layer on a surface of the silicon dioxide film away from the substrate;

[0018] Etching the second superconducting thin film layer to the first insulating layer to form a plurality of second superconducting thin film structures;

[0019] Etching the first insulating layer to the first superconducting thin film layer to form a plurality of first insulating structures, wherein each first insulating structure covers each second superconducting thin film structure;

[0020] Etching the first superconducting thin film layer to the silicon dioxide film to form a plurality of loop electrodes and a plurality of first superconducting thin film structures;

[0021] forming a second insulating layer on the surfaces of the plurality of silicon dioxide films, the surfaces of the plurality of loop electrodes, the surfaces of the plurality of first insulating structures, and the surfaces of the plurality of second superconducting thin film structures;

[0022] Etching the second insulating layer to respectively reach the plurality of loop electrodes and the plurality of second superconducting thin film structures to form a plurality of connecting through holes and a plurality of second insulating structures;

[0023] preparing terminal resistors on surfaces of the plurality of second insulating structures between the plurality of connecting through holes;

[0024] Depositing a lead superconducting thin film layer on the surfaces of the plurality of connecting through holes and the plurality of second insulating structures;

[0025] The lead superconducting thin film layer is etched to the plurality of second insulating structures to form an input coil and a connection structure.

[0026] The first-order gradient parallel SQUID current sensor array and its preparation method: One loop electrode, one first Josephson junction structure and one second Josephson junction structure form a SQUID loop.

[0027] A first Josephson junction structure and a second Josephson junction structure are spaced apart on the loop electrodes to form a SQUID loop. Each loop electrode forms a closed loop. Furthermore, a parallel inductance structure is formed between the first and second Josephson junction structures in each SQUID loop, reducing the SQUID loop inductance and extending the critical current range during SQUID operation, effectively offsetting external magnetic field interference.

[0028] Furthermore, a SQUID loop formed by one of the loop electrodes, one of the first Josephson junction structures, and one of the second Josephson junction structures adopts a first-order gradient simple structure, which is beneficial for reducing external magnetic field interference.

[0029] The negative electrode connection structure is connected to a second superconducting thin film structure of the first Josephson junction structure and a second superconducting thin film structure of the second Josephson junction structure, respectively. In this case, it can also be understood that a second superconducting thin film structure of the first Josephson junction structure and a second superconducting thin film structure of the second Josephson junction structure are connected via the negative electrode connection structure. Furthermore, the negative electrode connection structure, the first Josephson junction structure, the second Josephson junction structure, and the loop electrode form a SQUID loop with two Josephson junctions connected in parallel.

[0030] One of the positive electrode connection structures is connected to the loop electrode. At this point, the positive and negative electrodes of a SQUID loop formed by the parallel connection of the first and second Josephson junction structures are led out through the positive electrode connection structure and the negative electrode connection structure. The negative electrode connection structure corresponding to one of the loop electrodes is connected to the positive electrode connection structure corresponding to an adjacent loop electrode, thereby connecting multiple SQUID loops in series and forming a first-order gradient parallel SQUID current sensor array.

[0031] At the same time, in the first-order gradient parallel SQUID current sensor array, the negative electrode connection structure of the first SQUID loop is connected to the negative electrode of the power supply. In the first-order gradient parallel SQUID current sensor array, the positive electrode connection structure of the last SQUID loop is connected to the positive electrode of the power supply. The positive and negative electrode connection structures can be connected to the positive and negative electrodes of the power supply, enabling detection of the voltage of the first-order gradient parallel SQUID current sensor array, thereby obtaining changes in the TES signal and realizing TES detector signal readout.

[0032] Therefore, by using the first-order gradient structure of the first-order gradient parallel SQUID current sensor array and forming a parallel inductance structure in each SQUID loop, the SQUID loop inductance can be reduced, making the critical current range of the SQUID wider during operation, and effectively offsetting external magnetic field interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0035] Figure 2 Schematic diagram of the circuit structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0036] Figure 3 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0037] Figure 4 Schematic diagram of the structure of a loop electrode, a first Josephson junction structure, and a second Josephson junction structure provided in one embodiment.

[0038] Figure 5 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0039] Figure 6 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0040] Figure 7Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0041] Figure 8 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0042] Figure 9 This is a SEM morphology image of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0043] Figure 10 FIG. 1 is a cross-sectional schematic diagram of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0044] Figure 11 FIG. 1 is a cross-sectional schematic diagram of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0045] Figure 12 FIG. 4 is an IV curve of a first-order gradient parallel SQUID current sensor array provided in one embodiment.

[0046] Description of reference numerals:

[0047] First-order gradient parallel SQUID current sensor 100, loop electrode 20, first loop electrode 210, second loop electrode 220, input coil 30, first input loop 310, second input loop 320, input loop connection structure 330, first Josephson junction structure 510, second Josephson junction structure 520, terminal resistor 60, first terminal resistor 610, second terminal resistor 620, positive electrode connection structure 710, negative electrode connection structure 720, substrate 10, silicon dioxide film 110, second superconducting thin film structure 120, first insulating structure 130, connecting through hole 140, second insulating structure 150, first superconducting thin film structure 160. DETAILED DESCRIPTION

[0048] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0050] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types, and / or portions, these elements, components, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, doping type, or portion from another element, component, region, layer, doping type, or portion. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, doping type or portion discussed below may be represented as a second element, component, region, layer or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as 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.

[0051] Spatially relative terms such as "under," "beneath," "beneath," "under," "above," "above," etc., may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the drawings is turned over, the element or feature described as "under" or "beneath" or "beneath" the other elements will be oriented as "above" the other elements or features. Thus, the exemplary terms "under" and "under" can include both upper and lower orientations. In addition, the device can also include alternative orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0052] As used herein, the singular forms "a," "an," and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include," "comprising," "having," and the like 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 relevant listed items.

[0053] Embodiments of the present invention are described herein with reference to cross-sectional views that are schematic representations of idealized embodiments (and intermediate structures) of the present invention, and variations in the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are anticipated. Accordingly, embodiments of the present invention should not be limited to the specific shapes of the regions illustrated herein, but rather include deviations in shapes due to, for example, manufacturing techniques. Therefore, the regions shown in the figures are schematic in nature, and their shapes do not represent the actual shapes of the regions of the device and do not limit the scope of the present invention.

[0054] See also Figure 1 The present application provides a first-order gradient parallel SQUID current sensor array 100. The first-order gradient parallel SQUID current sensor array 100 includes a plurality of loop electrodes 20, a plurality of first Josephson junction structures 510, a plurality of second Josephson junction structures 520, a plurality of positive electrode connection structures 710, and a plurality of negative electrode connection structures 720. The plurality of loop electrodes 20 form a closed loop. The first superconducting thin film structure of each first Josephson junction structure 510 is disposed on each loop electrode 20. The first superconducting thin film structure of each second Josephson junction structure 520 is disposed on each loop electrode 20. The first Josephson junction structure 510 and the second Josephson junction structure 520 are spaced apart. Each positive electrode connection structure 710 is connected to each loop electrode 20. Each negative electrode connection structure 720 is connected to the second superconducting thin film structure of the first Josephson junction structure 510 and the second superconducting thin film structure of the second Josephson junction structure 520, respectively. The negative electrode connection structure 720 corresponding to one loop electrode 20 is connected to the positive electrode connection structure 710 corresponding to an adjacent loop electrode 20 .

[0055] In this embodiment, the loop electrode 20 is made of a superconducting thin film material. One loop electrode 20, one first Josephson junction structure 510 and one second Josephson junction structure 520 form a SQUID loop (the main component of the SQUID loop).

[0056] A first Josephson junction structure 510 and a second Josephson junction structure 520 are spaced apart on the loop electrode 20 to form a SQUID loop. Each loop electrode 20 forms a closed loop. Furthermore, a parallel inductance structure is formed between the first Josephson junction structure 510 and the second Josephson junction structure 520 in each SQUID loop. This reduces the SQUID loop inductance, broadens the critical current range during SQUID operation, and effectively offsets external magnetic field interference.

[0057] Furthermore, a SQUID loop formed by one of the loop electrodes 20 , one of the first Josephson junction structures 510 and one of the second Josephson junction structures 520 adopts a first-order gradient simple structure, which is beneficial for reducing external magnetic field interference.

[0058] A negative electrode connection structure 720 is connected to the second superconducting thin film structure of the first Josephson junction structure 510 and the second superconducting thin film structure of the second Josephson junction structure 520, respectively. In this case, it can also be understood that the second superconducting thin film structure of the first Josephson junction structure 510 and the second superconducting thin film structure of the second Josephson junction structure 520 are connected via the negative electrode connection structure 720. Furthermore, the negative electrode connection structure 720, the first Josephson junction structure 510, the second Josephson junction structure 520, and the loop electrode 20 form a SQUID loop with two Josephson junctions connected in parallel.

[0059] One of the positive electrode connection structures 710 is connected to the loop electrode 20. At this time, the positive and negative electrodes of a SQUID loop formed by the first Josephson junction structure 510 and the second Josephson junction structure 520 being connected in parallel are led out through one of the positive electrode connection structures 710 and one of the negative electrode connection structures 720. The negative electrode connection structure 720 corresponding to one of the loop electrodes 20 is connected to the positive electrode connection structure 710 corresponding to an adjacent loop electrode 20, so that multiple SQUID loops are connected in series (see Figure 2 As shown), a first-order gradient parallel SQUID current sensor array 100 is formed.

[0060] At the same time, in the first-order gradient parallel SQUID current sensor array 100, the negative electrode connection structure 720 of the first SQUID loop is connected to the negative electrode of the power supply. In the first-order gradient parallel SQUID current sensor array 100, the positive electrode connection structure 710 of the last SQUID loop is connected to the positive electrode of the power supply. The positive and negative electrodes of the power supply can be connected through the positive electrode connection structure 710 and the negative electrode connection structure 720, enabling detection of the voltage of the first-order gradient parallel SQUID current sensor array 100, thereby obtaining changes in the TES signal and realizing TES detector signal readout.

[0061] Therefore, through the first-order gradient structure of the first-order gradient parallel SQUID current sensor array 100 and the formation of a parallel inductance structure in each SQUID loop, the SQUID loop inductance can be reduced, so that the critical current range of the SQUID during operation is wider, and external magnetic field interference can be effectively offset.

[0062] See also Figure 3In one embodiment, the first-order gradient parallel SQUID current sensor array 100 further includes an input coil 30. The input coil 30 is disposed on the surface of the plurality of loop electrodes 20. The input coil 30 is insulated from the plurality of loop electrodes 20. The input coil 30 is used to input a superconducting transition edge detector signal.

[0063] In this embodiment, the input coil 30 is made of superconducting thin film material. The input coil 30 is insulated and arranged on the multiple loop electrodes 20, forming an upper and lower overlapping coupling structure with the SQUID loop. The insulation setting is used to separate the various structures to avoid crosstalk between the currents flowing between each other. It can be understood that the input coil 30 and the SQUID loop exist independently of each other. The input coil 30 is insulated and arranged on the surface of the multiple loop electrodes 20, forming an upper and lower overlapping coupling structure, so that the coupling between the input coil 30 and the multiple SQUID loops is more matched, thereby increasing the coupling coefficient. The input coil 30 is connected to a superconducting transition edge detector (TES) for inputting TES signals.

[0064] At the same time, each SQUID loop forms a simple first-order gradient structure, and increases the coupling area with the input coil 30 through the parallel inductance structure. The coupling structure is simple, which is more conducive to the detection of TES signals.

[0065] In one embodiment, the first-order gradient parallel SQUID current sensor array 100 further includes a feedback coil. The feedback coil is spaced apart from the multiple loop electrodes 20, and the input coil 30 is disposed on the surface of the multiple loop electrodes 20, thereby achieving a spaced-apart arrangement of the feedback coil and the input coil 30. When the feedback coil is connected to the test system, namely, to the flux-locking loop, an appropriate current flows through the feedback coil to achieve flux locking, providing a stable magnetic field environment for the input coil 30 and the multiple SQUID loops, and preventing interference during the detection process.

[0066] See also Figure 4 In one embodiment, each of the loop electrodes 20 includes a first loop electrode 210 and a second loop electrode 220. The first end of the second loop electrode 220 is connected to the first end of the first loop electrode 210. The second end of the second loop electrode 220 is connected to the second end of the first loop electrode 210. The first loop electrode 210 and the second loop electrode 220 form a closed loop.

[0067] In this embodiment, the first loop electrode 210 and the second loop electrode 220 are as follows Figure 5 The bottom gray area (or Figure 5(The loop is marked with a dashed line in the middle). The second loop electrode 220 is connected to a first end opposite the first loop electrode 210. The second loop electrode 220 is connected to a second end opposite the first loop electrode 210. In this case, the second loop electrode 220 and the first loop electrode 210 form a closed connected loop, without crossing each other. Thus, when the first Josephson junction structure 510 and the second Josephson junction structure 520 are spaced apart from each other on the loop electrode 20, a SQUID loop with a parallel inductance structure can be formed.

[0068] See also Figure 4 In one embodiment, the first superconducting thin film structure of each first Josephson junction structure 510 is disposed at the first end of each first loop electrode 210 , and the first superconducting thin film structure of each second Josephson junction structure 520 is disposed at the second end of each first loop electrode 210 .

[0069] In this embodiment, the first Josephson junction structure 510 and the second Josephson junction structure 520 are respectively disposed at the first and second ends of the first loop electrode 210. The first end of the second loop electrode 220 is connected to the first end of the first loop electrode 210. The second end of the second loop electrode 220 is connected to the second end of the first loop electrode 210. Furthermore, the first Josephson junction structure 510 and the second Josephson junction structure 520 are also disposed at the first and second ends of the second loop electrode 220. The first and second loop electrodes 210 and 220 are symmetrically disposed with respect to the first and second Josephson junction structures 510 and 520. When current flows through the loop electrodes 20, the symmetrical arrangement can offset interference generated by the loop electrodes 20, thereby preventing interference during the detection process.

[0070] In one embodiment, the first superconducting thin film structure 160 (lower Nb film) of the first Josephson junction structure 510 is connected to the first end of the first loop electrode 210. The first superconducting thin film structure 160 (lower Nb film) of the second Josephson junction structure 520 is connected to the second end of the first loop electrode 210, forming a SQUID loop formed by two Josephson junctions connected in parallel. The SQUID loop formed by the two Josephson junctions connected in parallel is converted into a circuit structure as shown in FIG. Figure 2 shown.

[0071] The loop electrode 20 is arranged in parallel between the first Josephson junction structure 510 and the second Josephson junction structure 520, forming a SQUID loop with a first-order gradient parallel structure. The SQUID loop increases the coupling area with the input coil 30 by using a parallel inductor. And the SQUID loop and the input coil 30 form an upper and lower overlapping coupling structure. Therefore, the first-order gradient parallel type SQUID current sensor array 100 includes a plurality of SQUID current sensors with a first-order gradient parallel inductance structure. The coupling structure is simple, which can reduce the SQUID loop inductance, making the critical current range of the SQUID wider when working, which is conducive to reducing external magnetic field interference and facilitating the coupling matching between the input coil 30 and the SQUID loop.

[0072] See also Figure 4 In one embodiment, each of the first Josephson junction structures 510 and each of the second Josephson junction structures 520 are disposed on the same horizontal line. Each of the first ring electrodes 210 and each of the second ring electrodes 220 are disposed symmetrically about the horizontal line.

[0073] In this embodiment, the first loop electrode 210 and the second loop electrode 220 are symmetrically arranged about the horizontal line to form a symmetrical structure. When current flows through each loop electrode 20, the symmetrical arrangement can offset the interference generated by each other, thereby avoiding interference during the detection process.

[0074] See also Figure 6 、 Figure 7 and Figure 8 In one embodiment, the input coil 30 includes a first input loop 310 and a second input loop 320. The first input loop 310 is insulated and disposed on the surface of the plurality of first loop electrodes 210. The second input loop 320 is insulated and disposed on the surface of the plurality of second loop electrodes 220. The first input loop 310 and the second input loop 320 are connected end to end in sequence to form the input coil 30. Figure 6 As shown in the black lines and as Figure 7 As shown by the black dashed line in .

[0075] In this embodiment, the first input loop 310 and the second input loop 320 are connected end to end to form the input coil 30. Figure 6As shown. The input coil 30 is connected to a superconducting transition edge detector (TES) for inputting TES signals. When the TES signal is input, the input current in the input coil 30 changes, causing the magnetic field to change. At this time, the multiple SQUID loops enter a resistive state under the action of the bias magnetic field, forming a voltage bias across the SQUID loops, thereby obtaining the changes in the TES signal and enabling TES detector signal readout.

[0076] The first input loop 310 is insulated and disposed on the surface of the plurality of first loop electrodes 210. The second input loop 320 is insulated and disposed on the surface of the plurality of second loop electrodes 220. The corresponding arrangement of the first input loop 310 with the plurality of first loop electrodes 210, and the corresponding arrangement of the second input loop 320 with the plurality of second loop electrodes 220, allows for a more closely aligned vertically overlapping coupling structure between the input coil 30 and the plurality of loop electrodes 20.

[0077] Thus, the input coil 30 is insulated and arranged on the surfaces of the plurality of loop electrodes 20 to form an upper and lower overlapping coupling structure, so that the coupling between the input coil 30 and the SQUID loop is more matched, thereby increasing the coupling coefficient.

[0078] See also Figure 6 In one embodiment, the first input loop 310 and the second input loop 320 are connected end to end via an input loop connection structure 330 .

[0079] In this embodiment, the first input loop 310 and the second input loop 320 are connected end to end through the input loop connection structure 330 to form an open link. At this time, the input coil 30 has two connection ports, such as A+ terminal and A- terminal ( Figure 2 as shown), used as input and output terminals.

[0080] The input loop connection structure 330 and the loop electrode 20 are arranged on the same layer, and both are made of superconducting thin film materials.

[0081] See also Figure 4 In one embodiment, each of the first Josephson junction structures 510 and each of the second Josephson junction structures 520 are symmetrically arranged about a vertical line. Each of the loop electrodes 20 is symmetrically arranged about the vertical line.

[0082] In this embodiment, the first Josephson junction structure 510, the second Josephson junction structure 520, and the loop electrode 20 are all symmetrical about a vertical line, resulting in a SQUID loop that is symmetrical about both horizontal and vertical lines. In this case, the first Josephson junction structure 510 and the first loop electrode 210 are rotated 180° to obtain the second Josephson junction structure 520 and the second loop electrode 220. The SQUID loop forms a centrally symmetrical structure. Consequently, when current flows through the multiple loop electrodes 20, the symmetrical structure of the SQUID loop can cancel out any interference generated by the loop electrodes, thereby preventing interference during the detection process.

[0083] See also Figure 8 In one embodiment, the first-order gradient parallel SQUID current sensor array 100 further includes a plurality of first terminal resistors 610 and a plurality of second terminal resistors 620. Each first terminal resistor 610 is connected in parallel with each first Josephson junction structure 510. Each second terminal resistor 620 is connected in parallel with each second Josephson junction structure 520. The first terminal resistors 610 and the second terminal resistors 620 are used to reduce signal reflections. The loop electrode 20, the first Josephson junction structure 510, the second Josephson junction structure 520, the first terminal resistors 610, and the second terminal resistors 620 form a complete SQUID loop.

[0084] In this embodiment, one end of a first terminal resistor 610 is connected to a loop electrode 20, and further connected to the first superconducting thin film structure 160 (lower Nb film) of the first Josephson junction structure 510. The other end of a first terminal resistor 610 is connected to the second superconducting thin film structure 120 (upper Nb film) of the first Josephson junction structure 510, thereby achieving a parallel connection between the first terminal resistor 610 and the first Josephson junction structure 510.

[0085] One end of a second terminal resistor 620 is connected to a loop electrode 20, and further connected to the first superconducting thin film structure 160 (lower Nb film) of a second Josephson junction structure 520. The other end of a second terminal resistor 620 is connected to the second superconducting thin film structure 120 (upper Nb film) of a second Josephson junction structure 520, thereby achieving a parallel connection between the second terminal resistor 620 and the second Josephson junction structure 520.

[0086] In one embodiment, a first terminal resistor 610 is connected in parallel to a first Josephson junction structure 510 via a first resistor connection structure 611 and a second resistor connection structure 612. The first resistor connection structure 611 is connected to the second superconducting thin film structure 120 (upper Nb film) of the first Josephson junction structure 510. The second resistor connection structure 612 is connected to the first superconducting thin film structure 160 (lower Nb film) of the first Josephson junction structure 510, i.e., the loop electrode 20.

[0087] Similarly, a second terminal resistor 620 is connected in parallel to a second Josephson junction structure 520 via a third resistor connection structure 621 and a fourth resistor connection structure 622. The third resistor connection structure 621 is connected to the second superconducting thin film structure 120 (upper Nb film) of the second Josephson junction structure 520. The fourth resistor connection structure 622 is connected to the first superconducting thin film structure 160 (lower Nb film) of the second Josephson junction structure 520, i.e., the loop electrode 20.

[0088] In one embodiment, the negative electrode connection structure 720, the first resistor connection structure 611, and the third resistor connection structure 621 are the same connection structure, which realizes the connection between the first terminal resistor 610, the second superconducting thin film structure 120 (upper Nb film) of the first Josephson junction structure 510, the second superconducting thin film structure 120 (upper Nb film) of the second Josephson junction structure 520, and the second terminal resistor 620. Specifically, the first resistor connection structure 611, the third resistor connection structure 621, and the negative electrode connection structure 720 are Nb film lead layer structures.

[0089] In one embodiment, each of the first terminal resistors 610 and each of the second terminal resistors 620 are symmetrically arranged about the vertical line.

[0090] In this embodiment, the overall structure formed by multiple first terminal resistors 610, multiple second terminal resistors 620, multiple first Josephson junction structures 510, multiple second Josephson junction structures 520, multiple loop electrodes 20, multiple first input loops 310, and multiple second input loops 320 forms a symmetrical structure.

[0091] See also Figure 9 In one embodiment, Figure 9 This is the SEM morphology of the current sensor based on superconducting quantum interference device.

[0092] See also Figure 10 and Figure 11(The preparation process of a SQUID is shown. A SQUID array can also be prepared using this method.) In one embodiment, the present application provides a method for preparing a first-order gradient parallel SQUID current sensor array, comprising:

[0093] S10, providing a substrate 10, and forming a silicon dioxide film 110 on the surface of the substrate 10;

[0094] S20, sequentially forming a first superconducting thin film layer, a first insulating layer, and a second superconducting thin film layer on a surface of the silicon dioxide film 110 away from the substrate 10;

[0095] S30, etching the second superconducting thin film layer to the first insulating layer to form a plurality of second superconducting thin film structures 120;

[0096] S40, etching the first insulating layer to the first superconducting thin film layer to form a plurality of first insulating structures 130, each of the first insulating structures 130 covering each of the second superconducting thin film structures 120;

[0097] S50 , etching the first superconducting thin film layer to the silicon dioxide film 110 to form a plurality of loop electrodes 20 and a plurality of first superconducting thin film structures 160 ;

[0098] S60, forming a second insulating layer on the surfaces of the plurality of silicon dioxide films 110, the surfaces of the plurality of loop electrodes 20, the surfaces of the plurality of first insulating structures 130, and the surfaces of the plurality of second superconducting thin film structures 120;

[0099] S70 , etching the second insulating layer to the plurality of loop electrodes 20 and the plurality of second superconducting thin film structures 120 , respectively, to form a plurality of connecting through holes 140 and a plurality of second insulating structures 150 ;

[0100] S80 , preparing terminal resistors 60 on the surfaces of the plurality of second insulating structures 150 between the plurality of connecting through holes 140 ;

[0101] S90, depositing a lead superconducting thin film layer on the surfaces of the plurality of connecting through holes 140 and the plurality of second insulating structures 150;

[0102] S100 , etching the lead superconducting thin film layer to the plurality of second insulating structures 150 to form the input coil 30 and the connection structure.

[0103] In this embodiment, in the step S20, a first superconducting thin film layer (lower Nb film), a first insulating layer (AlO film), and a second insulating layer (AlO film) are sequentially prepared by magnetron sputtering. x) and the second superconducting thin film layer (upper Nb film), forming Nb / AlO x / Nb three-layer film.

[0104] In the S30 and S40, the second superconducting film and the first insulating layer are etched respectively to form the second superconducting film structure 120 and the first insulating structure 130. In the S40, the first insulating layer is aluminum oxide (AlO x ), wet etching the first insulating layer (aluminum oxide) so that the first insulating structure 130 completely covers the second superconducting thin film structure 120. It can be understood that the area of the first insulating structure 130 is larger than the area of the second superconducting thin film structure 120. By covering the second superconducting thin film structure 120 with the first insulating structure 130, it can be ensured that the formed Nb / AlO x The / Nb Josephson junction region has no side leakage, which is beneficial to the quality stability of the Josephson junction in the SQUID loop.

[0105] In the step S50, the loop electrode 20 and the first superconducting thin film structure 160 are the same layer of superconducting thin film. The first superconducting thin film layer is etched to form a SQUID loop electrode pattern (i.e., the loop electrode 20) and the first superconducting thin film structure 160 of the Josephson junction (10 and Figure 11 Only the first superconducting film structure 160 is shown schematically. At this time, it can be understood that the first superconducting film structure 160 and the SQUID loop electrode pattern are an integrated structure, both of which are formed by etching the first superconducting film layer. Figure 6 The plurality of loop electrodes 20 and the input loop connection structure 330 and other structures.

[0106] At this time, the first superconducting thin film structure 160, the second superconducting thin film structure 120, and the first insulating structure 130 form a Josephson junction structure. The two Josephson junction structures and the loop electrode 20 form a superconducting quantum interference device loop (SQUID loop).

[0107] In the step S70, the plurality of connecting through holes 140 are used to deposit the Nb film. At this time, the Nb film is electrically connected to the loop electrode 20 through the connecting through holes 140. Figure 1 The positive electrode connection structure 710 in the embodiment of the present invention. The Nb film can be electrically connected to the second superconducting thin film structure 120 (the upper Nb film of the Josephson junction) through the connecting through hole 140. Figure 1 The negative electrode connection structure 720 in the embodiment. At the same time, the second insulating structure 150 can be used to achieve Figure 1 It provides isolation and insulation between overlapping structures such as the loop electrode 20 and the input coil 30.

[0108] In the step S80, the terminal resistor 60 (the first terminal resistor 610 and the second terminal resistor 620) (see Figure 5 The middle structure) is arranged close to the Josephson junction and serves as the terminal resistance of the first-order gradient parallel SQUID current sensor 100.

[0109] In the step S90, a lead superconducting thin film layer is deposited on the surfaces of the plurality of connecting through holes 140 and the second insulating structure 150. The lead superconducting thin film layer is a Nb film.

[0110] In the step S100, the lead superconducting thin film layer (Nb film) is etched to form the input coil 30 and the connection structure. The connection structure may be the connection structure involved in the above embodiment, such as Figure 8 The first resistor connection structure 611, the second resistor connection structure 612, the third resistor connection structure 621, the fourth resistor connection structure 622, the positive electrode connection structure 710, the negative electrode connection structure 720, etc.

[0111] Therefore, through the fabrication method of the first-order gradient parallel SQUID current sensor array, the first insulating structure 130 covers the second superconducting thin film structure 120, ensuring that the Josephson junction region does not leak, which is beneficial for stabilizing the quality of the Josephson junction in the SQUID. Furthermore, the first-order gradient parallel SQUID current sensor array 100 prepared through the fabrication method of the first-order gradient parallel SQUID current sensor array can increase the coupling area, effectively offset external magnetic field interference, and further facilitate the readout of TES signals.

[0112] In one embodiment, the thickness of the silicon dioxide film 110 is 100 nm to 1000 nm. The thickness of the first superconducting film layer (lower Nb film) is 100 nm to 500 nm. The first insulating layer (AlO x ) has a thickness of 5 nm to 30 nm. The thickness of the second superconducting thin film layer (upper Nb film) is 100 nm to 500 nm. The thickness of the second insulating structure 150 is 200 nm to 600 nm. The thickness of the terminal resistor structure 60 (PdAu thin film) is 50 nm to 500 nm. The thickness of the lead superconducting thin film layer (Nb thin film) is 300 nm to 800 nm.

[0113] In one embodiment, Nb / AlO is prepared by magnetron sputtering. x / Nb three-layer film, AlO xThe oxidation pressure of the film is 100mTorr to 5000mTorr, and the oxidation time is 5 hours to 24 hours. The area of the Josephson junction region is (the second superconducting thin film structure 120) 1μm 2 ~100μm 2 .

[0114] Specifically, in one embodiment, the method for preparing the first-order gradient parallel SQUID current sensor array includes:

[0115] The Nb / AlO film was deposited on a 2-inch single crystal high-resistance silicon wafer 10 with a 100 nm thick SiO2 film 110 by magnetron sputtering. x / Nb three-layer film with thickness of 100nm, 5nm and 100nm respectively. Among them, AlO was prepared by magnetron sputtering x The membrane was prepared at an oxidation pressure of 100 mTorr and an oxidation time of 5 hours.

[0116] Based on the above steps, the first photolithography is performed and the upper Nb film is etched to obtain an area of 1 μm 2 The upper layer pattern of the Josephson junction region (the second superconducting thin film structure 120).

[0117] Based on the above steps, a second photolithography is performed to etch the middle layer AlO by wet etching. x film, forming AlO x Structure 130, the middle layer pattern of the Josephson junction region is obtained. x The structure 130 completely covers the upper pattern 120 .

[0118] Based on the above steps, a third photolithography is performed to etch the bottom Nb film to obtain a SQUID loop pattern.

[0119] Based on the above steps, a 200nm thick SiO2 film is grown using low-temperature chemical vapor deposition. A third photolithography step is then performed, and the SiO2 film is etched to form a through-hole connection structure 140 between the Nb line layer and the underlying Nb film. The remaining SiO2 film serves as the second insulating structure 150.

[0120] Based on the above steps, a fourth photolithography is performed, and a 50 nm thick PdAu thin film is prepared as a resistor layer by electron beam evaporation, and then peeled off to obtain the PdAu resistor 60 .

[0121] Based on the above steps, a 300 nm thick Nb film is deposited by magnetron sputtering, and then a fifth photolithography is performed and the Nb film is etched to obtain the input coil 30 and the connection structure pattern.

[0122] Based on the above steps, the 2-inch sample is diced to obtain a first-order gradient parallel SQUID current sensor array 100 .

[0123] In one embodiment, the method for preparing the first-order gradient parallel SQUID current sensor array includes:

[0124] The Nb / AlO film was prepared by magnetron sputtering on a 2-inch single crystal high-resistance silicon wafer 10 with a 1000 nm thick SiO2 film 110. x / Nb three-layer film with thickness of 500nm, 30nm and 500nm respectively. Among them, AlO was prepared by magnetron sputtering. x The membrane was prepared at an oxidation pressure of 5000 mTorr and an oxidation time of 24 hours.

[0125] Based on the above steps, the first photolithography is performed and the upper Nb film is etched to obtain an area of 100 μm 2 The upper layer pattern of the Josephson junction region (the second superconducting thin film structure 120).

[0126] Based on the above steps, a second photolithography is performed to etch the middle layer AlO by wet etching. x film, forming AlO x Structure 130. wherein AlO x The structure 130 completely covers the upper pattern 120 .

[0127] Based on the above steps, a third photolithography is performed to etch the bottom Nb film to obtain a SQUID loop pattern.

[0128] Based on the above steps, a 600nm thick SiO2 film is grown using low-temperature chemical vapor deposition. A third photolithography step is then performed, and the SiO2 film is etched to form a through-hole connection structure 140 between the Nb line layer and the underlying Nb film. The remaining SiO2 film serves as the second insulating structure 150.

[0129] Based on the above steps, a fourth photolithography is performed, and a 500 nm thick PdAu thin film is prepared as a resistor layer by electron beam evaporation, and then peeled off to obtain the PdAu resistor 60 .

[0130] Based on the above steps, an 800nm thick Nb film was deposited using magnetron sputtering. A fifth photolithography process was then performed, followed by etching of the Nb film to produce the input coil 30 and the connection structure pattern. Based on the above steps, a 2-inch sample was diced to produce the first-order gradient parallel SQUID current sensor array 100.

[0131] See also Figure 12, the critical current of the first-order gradient parallel SQUID current sensor array 100 is 80 μA.

[0132] Throughout this specification, references to terms such as "some embodiments," "other embodiments," and "desired embodiments" indicate that a particular feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present application. The schematic descriptions of these terms throughout this specification do not necessarily refer to the same embodiment or example.

[0133] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features of the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0134] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A first-order gradient parallel SQUID current sensor array, characterized in that: include: Multiple loop electrodes form a closed loop; a plurality of first Josephson junction structures, wherein the first superconducting thin film structure of each of the first Josephson junction structures is disposed on each of the loop electrodes; a plurality of second Josephson junction structures, wherein the first superconducting thin film structure of each second Josephson junction structure is disposed on each of the loop electrodes, and the first Josephson junction structure and the second Josephson junction structure are spaced apart from each other; a plurality of positive electrode connection structures, each of the positive electrode connection structures being connected to each of the loop electrodes; a plurality of negative electrode connection structures, each of the negative electrode connection structures being connected to the second superconducting thin film structure of the first Josephson junction structure and the second superconducting thin film structure of the second Josephson junction structure; The negative electrode connection structure corresponding to one of the loop electrodes is connected to the positive electrode connection structure corresponding to an adjacent loop electrode; Each of the loop electrodes comprises: first loop electrode; a second loop electrode, wherein a first end of the second loop electrode is connected to a first end of the first loop electrode, and a second end of the second loop electrode is connected to a second end of the first loop electrode to form a closed loop; Each of the first Josephson junction structures and each of the second Josephson junction structures are arranged on the same horizontal line, and each of the first loop electrodes and each of the second loop electrodes are arranged symmetrically about the horizontal line.

2. The first-order gradient parallel SQUID current sensor array according to claim 1, characterized in that: The first-order gradient parallel SQUID current sensor array further includes: An input coil is provided on the surface of the plurality of loop electrodes, and the input coil is insulated from the plurality of loop electrodes; The input coil is used to input a superconducting transition edge detector signal.

3. The first-order gradient parallel SQUID current sensor array according to claim 1, characterized in that: The first superconducting thin film structure of each first Josephson junction structure is arranged at the first end of each first loop electrode, and the first superconducting thin film structure of each second Josephson junction structure is arranged at the second end of each first loop electrode.

4. The first-order gradient parallel SQUID current sensor array according to claim 2, characterized in that: The input coil comprises: A first input loop is insulated and disposed on the surface of the plurality of first loop electrodes; A second input loop is insulated and disposed on the surface of the plurality of second loop electrodes; The first input loop and the second input loop are connected end to end in sequence to form the input coil.

5. The first-order gradient parallel SQUID current sensor array according to claim 1, characterized in that: Each of the first Josephson junction structures and each of the second Josephson junction structures are symmetrically arranged about a vertical line; Each of the loop electrodes is symmetrically arranged about the vertical line.

6. The first-order gradient parallel SQUID current sensor array according to claim 5, characterized in that: The first-order gradient parallel SQUID current sensor array further includes: a plurality of first terminal resistors, each of the first terminal resistors being connected in parallel with each of the first Josephson junction structures; A plurality of second terminal resistors are provided, each of the second terminal resistors being connected in parallel with each of the second Josephson junction structures.

7. The first-order gradient parallel SQUID current sensor array according to claim 6, characterized in that: Each of the first terminal resistors and each of the second terminal resistors are symmetrically arranged about the vertical line.

8. The first-order gradient parallel SQUID current sensor array according to claim 6, wherein each of the first terminal resistors is connected in parallel with each of the first Josephson junction structures, comprising: Each of the first terminal resistors is connected in parallel to each of the first Josephson junction structures through a first resistor connection structure and a second resistor connection structure.

9. The first-order gradient parallel SQUID current sensor array according to claim 6, wherein each of the second terminal resistors is connected in parallel with each of the second Josephson junction structures, comprising: Each of the second terminal resistors is connected in parallel to each of the second Josephson junction structures through a third resistor connection structure and a fourth resistor connection structure.

10. A method for preparing a first-order gradient parallel SQUID current sensor array according to any one of claims 1 to 9, characterized in that: The method comprises: Providing a substrate, and preparing a silicon dioxide film on the surface of the substrate; Sequentially forming a first superconducting thin film layer, a first insulating layer, and a second superconducting thin film layer on a surface of the silicon dioxide film away from the substrate; Etching the second superconducting thin film layer to the first insulating layer to form a plurality of second superconducting thin film structures; Etching the first insulating layer to the first superconducting thin film layer to form a plurality of first insulating structures, wherein each first insulating structure covers each second superconducting thin film structure; Etching the first superconducting thin film layer to the silicon dioxide film to form a plurality of loop electrodes and a plurality of first superconducting thin film structures; forming a second insulating layer on the surfaces of the plurality of silicon dioxide films, the surfaces of the plurality of loop electrodes, the surfaces of the plurality of first insulating structures, and the surfaces of the plurality of second superconducting thin film structures; Etching the second insulating layer to respectively reach the plurality of loop electrodes and the plurality of second superconducting thin film structures to form a plurality of connecting through holes and a plurality of second insulating structures; preparing terminal resistors on surfaces of the plurality of second insulating structures between the plurality of connecting through holes; Depositing a lead superconducting thin film layer on the surfaces of the plurality of connecting through holes and the plurality of second insulating structures; The lead superconducting thin film layer is etched to the plurality of second insulating structures to form an input coil and a connection structure.

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