First-order gradient parallel SQUID current sensor and preparation method

Abstract

The present application relates to a first-order gradient parallel SQUID current sensor and a preparation method. The loop electrode forms a closed loop. The first superconducting film structure of the first Josephson junction structure is arranged on the loop electrode. The first superconducting film structure of the second Josephson junction structure is arranged on the loop electrode. The first Josephson junction structure and the second Josephson junction structure are arranged at intervals on the loop electrode to form a SQUID loop. At this time, a parallel inductance structure is formed between the first Josephson junction structure and the second Josephson junction structure in the SQUID loop, which can reduce the SQUID loop inductance, so that the critical current range of the SQUID when working is wider, and can effectively offset the external magnetic field interference.

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 and a preparation method thereof. Background Art

[0002] The superconducting quantum interference device (SQUID) is a precision current and magnetic field measuring instrument with extremely high current sensitivity and magnetic field sensitivity. The superconducting transition edge detector (TES detector) has high sensitivity, but low noise level and weak output signal. Its signal readout requires a SQUID current sensor with high current sensitivity and matching noise level.

[0003] SQUID current sensors are easily interfered by external magnetic fields during operation, and usually work with TES detectors in environments without magnetic shielding or with poor magnetic shielding. Therefore, the SQUID current sensor needs to be designed as a gradient structure to reduce the influence of external magnetic fields. However, traditional SQUID current sensors mostly use a series structure, which results in a narrow critical current range when the SQUID is working, which is not conducive to offsetting external magnetic field interference. Summary of the invention

[0004] Based on this, it is necessary to provide a first-order gradient parallel SQUID current sensor and a preparation method to address the above problems.

[0005] The present application provides a first-order gradient parallel SQUID current sensor. The first-order gradient parallel SQUID current sensor includes a loop electrode, a first Josephson junction structure and a second Josephson junction structure. The loop electrode forms a closed loop. The first superconducting film structure of the first Josephson junction structure is arranged on the loop electrode. The first superconducting film structure of the second Josephson junction structure is arranged on the loop electrode. And the first Josephson junction structure and the second Josephson junction structure are arranged at intervals.

[0006] In one embodiment, the first-order gradient parallel SQUID current sensor further includes an input coil. The input coil is disposed on the surface of the loop electrode. The input coil is insulated from the loop electrode. The input coil is used to input a superconducting transition edge detector signal.

[0007] In one embodiment, the loop electrode 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 to form a closed loop.

[0008] In one embodiment, the first superconducting thin film structure of the first Josephson junction structure is disposed at a first end of the first loop electrode. The first superconducting thin film structure of the second Josephson junction structure is disposed at a second end of the first loop electrode.

[0009] In one embodiment, the first Josephson junction structure and the second Josephson junction structure are arranged on the same horizontal line. The first loop electrode and the second loop electrode are arranged symmetrically about the horizontal line.

[0010] In one embodiment, the input coil includes a first input loop and a second input loop. The first input loop is insulated and arranged on the surface of the first loop electrode. The second input loop is insulated and arranged on the surface of the second loop electrode. The first input loop and the second input loop are connected end to end in sequence to form the input coil.

[0011] In one embodiment, the first input loop and the second input loop are connected end to end via an input loop connection structure.

[0012] In one embodiment, the first-order gradient parallel SQUID current sensor further includes a first terminal resistor and a second terminal resistor. The first terminal resistor is connected in parallel to the first Josephson junction structure. The second terminal resistor is connected in parallel to the second Josephson junction structure.

[0013] In one embodiment, the first-order gradient parallel SQUID current sensor further includes a positive electrode connection structure and a negative electrode connection structure. The positive electrode connection structure is connected to the loop electrode. The negative electrode connection structure is respectively connected to the second superconducting film structure of the first Josephson junction structure and the second superconducting film structure of the second Josephson junction structure.

[0014] In one embodiment, the present application provides a method for preparing a first-order gradient parallel SQUID current sensor, comprising:

[0015] Providing a substrate, and preparing a silicon dioxide film on the surface of the substrate;

[0016] Sequentially forming a first superconducting film layer, a first insulating layer and a second superconducting film layer on a surface of the silicon dioxide film away from the substrate;

[0017] Etching the second superconducting film layer to the first insulating layer to form a second superconducting film structure;

[0018] Etching the first insulating layer to the first superconducting film to form a first insulating structure, wherein the first insulating structure covers the second superconducting film structure;

[0019] Etching the first superconducting film layer to the silicon dioxide film to form a loop electrode and a first superconducting film structure;

[0020] Preparing a second insulating layer on the surface of the silicon dioxide film, the surface of the loop electrode, the surface of the first insulating structure, and the surface of the second superconducting thin film structure;

[0021] Etching the second insulating layer to the loop electrode and the second superconducting thin film structure respectively to form a plurality of connecting through holes and the second insulating structure;

[0022] Preparing a terminal resistor on the surface of the second insulating structure between the plurality of connecting through holes;

[0023] Depositing a lead superconducting thin film layer on the surface of the plurality of connecting through holes and the second insulating structure;

[0024] The lead superconducting thin film layer is etched to the second insulating structure to form an input coil and a connecting structure.

[0025] The first-order gradient parallel SQUID current sensor and preparation method. The loop electrode is a superconducting thin film material. The loop electrode forms a closed loop, and the first Josephson junction structure and the second Josephson junction structure are arranged at intervals on the loop electrode to form a SQUID loop. At this time, a parallel inductance structure is formed between the first Josephson junction structure and the second Josephson junction structure in the SQUID loop, which can reduce the SQUID loop inductance, so that the critical current range of the SQUID when working is wider, and can effectively offset the external magnetic field interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. 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.

[0027] Figure 1 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0028] Figure 2 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0029] Figure 3 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0030] Figure 4 Schematic diagram of the circuit structure of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0031] Figure 5 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0032] Figure 6 Schematic diagram of the structure of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0033] Figure 7 This is a SEM morphology image of a first-order gradient parallel SQUID current sensor provided in an embodiment.

[0034] Figure 8 Schematic diagram of a cross-section of a first-order gradient parallel SQUID current sensor provided in one embodiment.

[0035] Fig. 9 Schematic diagram of a cross-section of a first-order gradient parallel SQUID current sensor provided in an embodiment.

[0036] Fig.10 FIG. 4 is a V-Φ curve of an input coil in a first-order gradient parallel SQUID current sensor provided in an embodiment.

[0037] Description of reference numerals:

[0038] 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, first resistor connection structure 611, second resistor connection structure 612, second terminal resistor 620, third resistor connection structure 621, fourth resistor connection structure 622, positive electrode connection structure 710, negative electrode connection structure 720, substrate 10, silicon dioxide film 110, second superconducting film structure 120, first insulating structure 130, connecting through hole 140, second insulating structure 150, first superconducting film structure 160. DETAILED DESCRIPTION

[0039] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] 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 belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0041] 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 intervening elements or layers may be present. 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,

[0042] There is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, doping type or part discussed below can be represented as a second element, component, region, layer or part; for example, the first doping type can be referred to as the second doping type, and similarly, the second doping type can 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 can be P-type and the second doping type can be N-type, or the first doping type can be N-type and the second doping type can be P-type.

[0043] Spatially relative terms such as "below", "beneath", "beneath", "above", "above", etc., may be used herein to describe the relationship of one element or feature to other elements or features shown in the figures. It should be understood that the spatially relative terms also encompass different orientations of the device in use and operation in addition to the orientation shown in the figures. For example, if the device in the figures is turned over, elements or features described as "below" or "beneath" or "under" the other elements would be oriented above the other elements.

[0044] or feature "on". Thus, the exemplary terms "below" and "beneath" can encompass both an orientation of above and below. Furthermore, the device may be comprised of alternative orientations (eg, rotated 90 degrees or at other orientations), and the spatial descriptors used herein should be interpreted accordingly.

[0045] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the relevant listed items.

[0046] Embodiments of the application are described herein with reference to cross-sectional views that are schematic diagrams of ideal embodiments (and intermediate structures) of the application, so that variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances can be expected. Therefore, embodiments of the application should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. Therefore, the regions shown in the figures are schematic in nature, their shapes do not represent the actual shapes of the regions of the device, and do not limit the scope of the application.

[0047] See also Figure 1 The present application provides a first-order gradient parallel SQUID current sensor 100. The first-order gradient parallel SQUID current sensor 100 includes a loop electrode 20, a first Josephson junction structure 510 and a second Josephson junction structure 520. The loop electrode 20 forms a closed loop. The first superconducting film structure of the first Josephson junction structure 510 is disposed on the loop electrode 20. The first superconducting film structure of the second Josephson junction structure 520 is disposed on the loop electrode 20. The first Josephson junction structure 510 and the second Josephson junction structure 520 are spaced apart.

[0048] In this embodiment, the loop electrode 20 is made of a superconducting thin film material. The loop electrode 20 forms a closed loop, and the first Josephson junction structure 510 and the second Josephson junction structure 520 are arranged at intervals on the loop electrode 20 to form the main structure of the SQUID loop. At this time, a parallel inductance structure is formed between the first Josephson junction structure 510 and the second Josephson junction structure 520 in the SQUID loop, which can reduce the SQUID loop inductance, make the critical current range of the SQUID wider when working, and can effectively offset the external magnetic field interference.

[0049] Furthermore, the SQUID loop formed by the loop electrode 20, the first Josephson junction structure 510 and the second Josephson junction structure 520 adopts a first-order gradient simple structure, which is conducive to reducing external magnetic field interference.

[0050] See also Figure 2In one embodiment, the first-order gradient parallel SQUID current sensor 100 further includes an input coil 30. The input coil 30 is disposed on the surface of the loop electrode 20. The input coil 30 is insulated from the loop electrode 20. The input coil 30 is used to input a superconducting transition edge detector signal. The input coil 30 is connected to a superconducting transition edge detector (TES) for inputting a TES signal.

[0051] In this embodiment, the input coil 30 is made of superconducting thin film material. The input coil 30 is insulated on the loop electrode 20, and forms 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 on the surface of the loop electrode 20, forming an upper and lower overlapping coupling structure, so that the coupling between the input coil 30 and the SQUID loop is more matched, and the coupling coefficient is increased. At the same time, the SQUID loop forms a simple first-order gradient structure, and through the parallel inductance structure, the coupling area with the input coil 30 is increased. The coupling structure is simple, which is more conducive to the detection of TES signals.

[0052] In one embodiment, the first-order gradient parallel SQUID current sensor 100 further includes a feedback coil. The feedback coil is spaced apart from the loop electrode 20, and the input coil 30 is disposed on the surface of the loop electrode 20, thereby realizing the spacing between the feedback coil and the input coil 30. When the feedback coil is connected to the test system, that is, connected to the flux locking loop, an appropriate current will flow into the feedback coil for flux locking, providing a stable magnetic field environment for the input coil 30 and the SQUID loop, and avoiding interference during the detection process.

[0053] In one embodiment, the loop electrode 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 to form a closed loop.

[0054] In this embodiment, Figure 2 The first loop electrode 210 and the second loop electrode 220 are as follows Figure 2 The bottom gray area (or Figure 2The second loop electrode 220 is connected to the first end of the first loop electrode 210. The second loop electrode 220 is connected to the second end of the first loop electrode 210. At this time, the second loop electrode 220 and the first loop electrode 210 form a closed connection loop without crossing each other. Therefore, when the first Josephson junction structure 510 and the second Josephson junction structure 520 are arranged at intervals on the loop electrode 20, a SQUID loop with a parallel inductance structure can be formed.

[0055] In one embodiment, the first superconducting film structure of the first Josephson junction structure 510 is disposed at a first end of the first loop electrode 210 . The first superconducting film structure of the second Josephson junction structure 520 is disposed at a second end of the first loop electrode 210 .

[0056] In this embodiment, the first Josephson junction structure 510 and the second Josephson junction structure 520 are arranged at the first end and the second end 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 arranged at the first end and the second end of the second loop electrode 220. The first loop electrode 210 and the second loop electrode 220 are symmetrically arranged with respect to the first Josephson junction structure 510 and the second Josephson junction structure 520. When the loop electrode 20 is passed with current, the interference generated by itself can be offset by the symmetrical arrangement, thereby avoiding interference during the detection process.

[0057] 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 two Josephson junctions connected in parallel is converted into a circuit structure as shown in FIG. Figure 4 shown.

[0058] Therefore, 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 means of parallel inductance. And the SQUID loop and the input coil 30 form an upper and lower overlapping coupling structure. Therefore, the first-order gradient parallel SQUID current sensor 100 forms a SQUID current sensor with a first-order gradient parallel inductance structure, which has a simple coupling structure and can reduce the SQUID loop inductance, so that the critical current range of the SQUID is wider when it is working, which is conducive to reducing external magnetic field interference and facilitating the coupling matching between the input coil 30 and the SQUID loop.

[0059] See also Figure 3 In one embodiment, the first Josephson junction structure 510 and the second Josephson junction structure 520 are arranged on the same horizontal line. The first loop electrode 210 and the second loop electrode 220 are arranged symmetrically about the horizontal line.

[0060] 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 is passed through the loop electrodes 20, the symmetrical arrangement can offset the interference generated by themselves, thereby avoiding interference during the detection process.

[0061] See also Figure 2 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 first loop electrode 210. The second input loop 320 is insulated and disposed on the surface of the second loop electrode 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.

[0062] In this embodiment, 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 2 As shown by the dotted line shown in . The input coil 30 is connected to a superconducting transition edge detector (TES) for inputting a TES signal. When a TES signal is input, the input current in the input coil 30 changes, causing the magnetic field to change. At this time, the SQUID loop enters a resistive state under the action of the bias magnetic field, and the SQUID loop forms a voltage bias, thereby obtaining the change of the TES signal and realizing the readout of the TES detector signal.

[0063] The first input loop 310 is insulated and arranged on the surface of the first loop electrode 210. The second input loop 320 is insulated and arranged on the surface of the second loop electrode 220. At this time, through the corresponding arrangement of the first input loop 310 and the first loop electrode 210, and the corresponding arrangement of the second input loop 320 and the second loop electrode 220, the upper and lower overlapping coupling structure of the input coil 30 and the loop electrode 20 can be more matched. Therefore, by the input coil 30 being insulated and arranged on the surface of the loop electrode 20, an upper and lower overlapping coupling structure is formed, so that the coupling between the input coil 30 and the SQUID loop is more matched, and the coupling coefficient is increased.

[0064] See also Figure 2 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 .

[0065] 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.

[0066] 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.

[0067] See also Figure 5 In one embodiment, the first-order gradient parallel SQUID current sensor 100 further includes a first terminal resistor 610 and a second terminal resistor 620. The first terminal resistor 610 is connected in parallel with the first Josephson junction structure 510. The second terminal resistor 620 is connected in parallel with the second Josephson junction structure 520. The first terminal resistor 610 and the second terminal resistor 620 are used to reduce signal reflection. The loop electrode 20, the first Josephson junction structure 510, the second Josephson junction structure 520, the first terminal resistor 610 and the second terminal resistor 620 form a complete SQUID loop.

[0068] In this embodiment, one end of the first terminal resistor 610 is connected to the loop electrode 20, and then connected to the first superconducting film structure 160 (lower Nb film) of the first Josephson junction structure 510. The other end of the first terminal resistor 610 is connected to the second superconducting film structure 120 (upper Nb film) of the first Josephson junction structure 510, so as to achieve the parallel connection between the first terminal resistor 610 and the first Josephson junction structure 510. One end of the second terminal resistor 620 is connected to the loop electrode 20, and then connected to the first superconducting film structure 160 (lower Nb film) of the second Josephson junction structure 520. The other end of the second terminal resistor 620 is connected to the second superconducting film structure 120 (upper Nb film) of the second Josephson junction structure 520, so as to achieve the parallel connection between the second terminal resistor 620 and the second Josephson junction structure 520.

[0069] In one embodiment, the first terminal resistor 610 is connected in parallel with the first Josephson junction structure 510 through 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 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 film structure 160 (lower Nb film) of the first Josephson junction structure 510, that is, the loop electrode 20.

[0070] Similarly, the second terminal resistor 620 is connected in parallel with the second Josephson junction structure 520 through the third resistor connection structure 621 and the fourth resistor connection structure 622. The third resistor connection structure 621 is connected to the second superconducting 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 film structure 160 (lower Nb film) of the second Josephson junction structure 520, that is, the loop electrode 20.

[0071] See also Figure 5 In one embodiment, the first-order gradient parallel SQUID current sensor 100 further includes a positive electrode connection structure 710 and a negative electrode connection structure 720. The positive electrode connection structure 710 is connected to the loop electrode 20. The negative electrode connection structure 720 is connected to the second superconducting film structure of the first Josephson junction structure 510 and the second superconducting film structure of the second Josephson junction structure 520, respectively.

[0072] In this embodiment, the positive and negative electrodes of the SQUID loop formed by the first Josephson junction structure 510 and the second Josephson junction structure 520 in parallel are led out through the positive electrode connection structure 710 and the negative electrode connection structure 720. 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 to detect the voltage of the SQUID loop, thereby obtaining the change of the TES signal and realizing the TES detector signal readout.

[0073] The second superconducting film structure of the first Josephson junction structure 510 and the second superconducting film structure of the second Josephson junction structure 520 are respectively connected through the negative electrode connection structure 720. At this time, it can also be understood that the second superconducting film structure of the first Josephson junction structure 510 and the second superconducting film structure of the second Josephson junction structure 520 are connected through 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.

[0074] 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, realizing the connection of the first terminal resistor 610, the second superconducting film structure 120 (upper Nb film) of the first Josephson junction structure 510, the second superconducting 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.

[0075] See also Figure 6 In one embodiment, the first Josephson junction structure 510 and the second Josephson junction structure 520 are symmetrically arranged about a vertical line. The loop electrode 20 is symmetrically arranged about the vertical line.

[0076] In this embodiment, the first Josephson junction structure 510, the second Josephson junction structure 520, and the loop electrode 20 are all symmetrical about the vertical line, so that the formed SQUID loop forms a structure that is symmetrical about both the horizontal line and the vertical line. At this time, 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 central symmetrical structure. Therefore, when the loop electrode 20 is passed with current, the symmetrical structure of the SQUID loop can offset the interference generated by itself, thereby avoiding interference during the detection process.

[0077] In one embodiment, the first terminal resistor 610 and the second terminal resistor 620 are symmetrically arranged with respect to the vertical line.

[0078] In this embodiment, the first terminal resistor 610, the second terminal resistor 620, the first Josephson junction structure 510, the second Josephson junction structure 520, the loop electrode 20, the first input loop 310, and the second input loop 320 form an overall structure that forms a symmetrical structure.

[0079] See also Figure 7 , in one embodiment, Figure 7 This is the SEM morphology of the current sensor based on superconducting quantum interference device.

[0080] See also Figure 8 and Fig. 9 In one embodiment, the present application provides a method for preparing a first-order gradient parallel SQUID current sensor, comprising:

[0081] S10, providing a substrate 10, and preparing a silicon dioxide film 110 on the surface of the substrate 10;

[0082] S20, sequentially forming a first superconducting film layer, a first insulating layer, and a second superconducting film layer on a surface of the silicon dioxide film 110 away from the substrate 10;

[0083] S30, etching the second superconducting film layer to the first insulating layer to form a second superconducting film structure 120;

[0084] S40, etching the first insulating layer to the first superconducting film layer to form a first insulating structure 130, wherein the first insulating structure 130 covers the second superconducting film structure 120;

[0085] S50, etching the first superconducting film layer to the silicon dioxide film 110, to form the loop electrode 20 and the first superconducting film structure 160;

[0086] S60, preparing a second insulating layer on the surface of the silicon dioxide film 110, the surface of the loop electrode 20, the surface of the first insulating structure 130, and the surface of the second superconducting film structure 120;

[0087] S70, etching the second insulating layer to the loop electrode 20 and the second superconducting thin film structure 120, respectively, to form a plurality of connecting through holes 140 and a second insulating structure 150;

[0088] S80, preparing a terminal resistor 60 on the surface of the second insulating structure 150 between the plurality of connecting through holes 140;

[0089] S90, depositing a lead superconducting thin film layer on the surfaces of the plurality of connecting through holes 140 and the second insulating structure 150;

[0090] S100, etching the lead superconducting thin film layer to the second insulating structure 150, forming the input coil 30 and the connection structure.

[0091] In this embodiment, in S20, a first superconducting thin film layer (lower Nb film), a first insulating layer (AlO x ) and the second superconducting film layer (upper Nb film), forming Nb / AlO x / Nb three-layer film.

[0092] 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) is used to make the first insulating structure 130 completely cover the second superconducting 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 film structure 120. By covering the second superconducting film structure 120 with the first insulating structure 130, it can be ensured that the formed Nb / AlO x / Nb Josephson junction region has no side leakage, which is beneficial to the quality stability of the Josephson junction in the SQUID loop.

[0093] In the step S50, the loop electrode 20 and the first superconducting film structure 160 are the same layer of superconducting film. The first superconducting film layer is etched to form a SQUID loop electrode pattern (i.e., the loop electrode 20) and the first superconducting film structure 160 of the Josephson junction (8 and Fig. 9 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, and both are formed by etching the first superconducting film layer. Figure 2 The loop electrode 20 and the input loop connection structure 330 are structured as follows. At this time, the first superconducting film structure 160, the second superconducting 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).

[0094] 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 2 The positive electrode connection structure 710 in the embodiment. 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 2 The negative electrode connection structure 720 in the embodiment. Meanwhile, the second insulating structure 150 can be used to realize Figure 2 It has an isolation and insulation effect between overlapping structures such as the loop electrode 20 and the input coil 30.

[0095] In the S80, the terminal resistor 60 (the first terminal resistor 610 and the second terminal resistor 620) (see Figure 5 The structure in the middle is arranged close to the Josephson junction and serves as the terminal resistance of the first-order gradient parallel SQUID current sensor 100.

[0096] In the S90, a lead superconducting film layer is deposited on the surface of the plurality of the connecting through holes 140 and the second insulating structure 150. The lead superconducting film layer is a Nb film. In the S100, the lead superconducting film layer (Nb film) is etched to form the input coil 30 and the connecting structure. The connecting structure may be the connecting structure involved in the above-mentioned embodiment, such as Figure 5 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.

[0097] Therefore, through the preparation method of the first-order gradient parallel SQUID current sensor, the first insulating structure 130 covers the second superconducting film structure 120, which can ensure that the Josephson junction area does not leak, which is beneficial to the quality stability of the Josephson junction in the SQUID. At the same time, the first-order gradient parallel SQUID current sensor 100 prepared by the preparation method of the first-order gradient parallel SQUID current sensor can increase the coupling area, effectively offset the external magnetic field interference, and is more conducive to the readout of the TES signal.

[0098] 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 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 60 (PdAu film) is 50 nm to 500 nm. The thickness of the lead superconducting film layer (Nb film) is 300 nm to 800 nm.

[0099] In one embodiment, Nb / AlO is prepared by magnetron sputtering. x / Nb three-layer film, AlO x The oxidation pressure of the film is 100 mTorr~5000 mTorr, and the oxidation time is 5 hours~24 hours. The area of ​​the Josephson junction region is (the second superconducting film structure 120) 1 μm 2 ~100 μm 2 .

[0100] Specifically, in one embodiment, the method for preparing the first-order gradient parallel SQUID current sensor comprises:

[0101] The Nb / AlO film was prepared by magnetron sputtering on a 2-inch single crystal high-resistance silicon wafer 10 with a 100 nm thick SiO2 film 110. x / Nb three-layer film with thicknesses of 100 nm, 5 nm and 100 nm 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.

[0102] Based on the above steps, the first photolithography was performed and the upper Nb film was 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).

[0103] 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. Among them, AlO x The structure 130 completely covers the upper pattern 120 .

[0104] Based on the above steps, a third photolithography is performed to etch the bottom Nb film to obtain a SQUID loop pattern.

[0105] Based on the above steps, a 200 nm thick SiO2 film is grown by low temperature chemical vapor deposition, and then a third photolithography is performed and the SiO2 film is etched to obtain a through-hole connection structure 140 between the Nb line layer and the lower Nb film. The remaining SiO2 film is the second insulating structure 150.

[0106] Based on the above steps, a fourth photolithography is performed, and a 50 nm thick PdAu film is prepared as a resistor layer by electron beam evaporation, and the PdAu resistor 60 is obtained by peeling.

[0107] Based on the above steps, a 300 nm thick Nb film is deposited by magnetron sputtering, and then the fifth photolithography is performed and the Nb film is etched to obtain the input coil 30 and the connection structure pattern.

[0108] Based on the above steps, the 2-inch sample is sliced ​​to obtain a first-order gradient parallel SQUID current sensor 100 .

[0109] In one embodiment, the method for preparing the first-order gradient parallel SQUID current sensor comprises:

[0110] The Nb / AlO film was prepared by magnetron sputtering on a 2-inch single crystal high-resistance silicon wafer 10 on which a 1000 nm thick SiO2 film 110 was grown. x / Nb three-layer film with thicknesses of 500 nm, 30 nm and 500 nm 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.

[0111] Based on the above steps, the first photolithography was performed and the upper Nb film was 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).

[0112] 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 .

[0113] Based on the above steps, a third photolithography is performed to etch the bottom Nb film to obtain a SQUID loop pattern.

[0114] Based on the above steps, a 600 nm thick SiO2 film is grown by low temperature chemical vapor deposition, and then a third photolithography is performed and the SiO2 film is etched to obtain a through-hole connection structure 140 between the Nb line layer and the lower Nb film. The remaining SiO2 film is the second insulating structure 150.

[0115] Based on the above steps, a fourth photolithography is performed, and a 500 nm thick PdAu film is prepared as a resistor layer by electron beam evaporation, and the PdAu resistor 60 is obtained by peeling.

[0116] Based on the above steps, a 800 nm thick Nb film is deposited by magnetron sputtering, and then the fifth photolithography is performed and the Nb film is etched to obtain the input coil 30 and the connection structure pattern. Based on the above steps, the 2-inch sample is sliced ​​to obtain the first-order gradient parallel SQUID current sensor 100.

[0117] See also Fig.10 , the flux-to-voltage conversion coefficient of the input coil in the first-order gradient parallel SQUID current sensor 100 is 10 μV / Φ0.

[0118] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0119] 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.

[0120] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A first-order gradient parallel SQUID current sensor, characterized in that: include: Loop electrodes, forming a closed loop; a first Josephson junction structure, wherein a first superconducting thin film structure of the first Josephson junction structure is arranged on the loop electrode; A second Josephson junction structure, wherein a first superconducting thin film structure of the second Josephson junction structure is arranged on the loop electrode, and the first Josephson junction structure and the second Josephson junction structure are arranged at intervals; The loop electrode comprises: a 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; The first superconducting film structure of the first Josephson junction structure is arranged at the first end of the first loop electrode, and the first superconducting film structure of the second Josephson junction structure is arranged at the second end of the first loop electrode; the first Josephson junction structure and the second Josephson junction structure are arranged on the same horizontal line, and the first loop electrode and the second loop electrode are symmetrically arranged about the horizontal line.

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

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

4. The first-order gradient parallel SQUID current sensor according to claim 3, characterized in that: The first input loop and the second input loop are connected end to end via an input loop connection structure.

5. The first-order gradient parallel SQUID current sensor according to claim 1, characterized in that: The first-order gradient parallel SQUID current sensor also includes: a first terminal resistor connected in parallel with the first Josephson junction structure; The second terminal resistor is connected in parallel with the second Josephson junction structure.

6. The first-order gradient parallel SQUID current sensor according to claim 1, characterized in that: The first-order gradient parallel SQUID current sensor also includes: A positive electrode connection structure connected to the loop electrode; The negative electrode connection structure is respectively connected to the second superconducting film structure of the first Josephson junction structure and the second superconducting film structure of the second Josephson junction structure.

7. A method for preparing a first-order gradient parallel SQUID current sensor according to any one of claims 1 to 6, 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 film layer, a first insulating layer and a second superconducting 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 second superconducting thin film structure; Etching the first insulating layer to the first superconducting thin film layer to form a first insulating structure, wherein the first insulating structure covers the second superconducting thin film structure; Etching the first superconducting film layer to the silicon dioxide film to form a loop electrode and a first superconducting film structure; Preparing a second insulating layer on the surface of the silicon dioxide film, the surface of the loop electrode, the surface of the first insulating structure, and the surface of the second superconducting thin film structure; Etching the second insulating layer to the loop electrode and the second superconducting thin film structure respectively to form a plurality of connecting through holes and the second insulating structure; Preparing a terminal resistor on the surface of the second insulating structure between the plurality of connecting through holes; Depositing a lead superconducting thin film layer on the surface of the plurality of connecting through holes and the second insulating structure; The lead superconducting thin film layer is etched to the second insulating structure to form an input coil and a connecting structure.

8. The method according to claim 7, characterized in that The first insulating layer is aluminum oxide, and the first insulating layer is etched to the first superconducting thin film layer to form a first insulating structure, including: The first insulating layer is etched by wet etching to the first superconducting thin film layer to form a first insulating structure.

9. The method according to claim 7, characterized in that: The loop electrode and the first superconducting film structure are a same layer of superconducting film.

10. The method according to claim 7, characterized in that The thickness of the silicon dioxide film is 100 nm to 1000 nm.

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