First-order gradient series SQUID current sensor and preparation method

Abstract

The present application relates to a first-order gradient series SQUID current sensor and a preparation method. The input coil is insulated and arranged on the surface of the loop electrode, forming an overlapping coupling structure between the input coil and the loop electrode, so that the coupling between the input coil and the SQUID loop is more matched, and the coupling coefficient is increased. The first superconducting film structure of the first Josephson structure is arranged at the first end of the loop electrode, and the first superconducting film structure of the second Josephson structure is arranged at the second end of the loop electrode, forming a first-order gradient series inductance structure SQUID, which can effectively offset external magnetic field interference. In addition, the feedback coil is arranged around the loop electrode to provide a stable magnetic field environment for the input coil and the SQUID loop.

Description

Technical Field

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

[0002] Superconducting quantum interference device (SQUID) is a precision instrument for measuring current and magnetic field. TES detectors are widely used in cosmic astronomy, high-energy physics, quantum information, photon metrology and other fields. However, the noise level of TES detectors is very low and the output signal is weak. Its signal readout requires a SQUID current sensor with high current sensitivity and noise level matching. The signal readout of all different types and bands of TES detectors requires a SQUID current sensor. Moreover, SQUID current sensors have become the only means of signal readout of TES detectors.

[0003] However, SQUID current sensors are easily disturbed by external magnetic fields during operation, and usually work with TES detectors in environments without magnetic shielding or with poor magnetic shielding. Traditional SQUID current sensors are second-order gradient structures with complex design structures, which are not conducive to the coupling matching between the input coil and the SQUID loop. Summary of the invention

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

[0005] The present application provides a first-order gradient series SQUID current sensor. The first-order gradient series SQUID current sensor includes a loop electrode, an input coil and a feedback coil. The input coil is arranged on the surface of the loop electrode. The input coil is insulated from the loop electrode. The feedback coil is spaced apart from the loop electrode. The feedback coil is arranged around the loop electrode. The input coil is used to input a superconducting transition edge detector signal. The feedback coil is used for flux locking.

[0006] In one embodiment, the loop electrode comprises a first loop electrode and a second loop electrode. The second loop electrode is connected end to end with the first loop electrode to form the loop electrode. The second loop electrode is symmetrically arranged with the first loop electrode.

[0007] In one embodiment, the input coil includes a first input loop and a second input loop. The first input loop is insulated from the first loop electrode. The second input loop is insulated from 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.

[0008] In one embodiment, the feedback coil includes a first feedback loop and a second feedback loop. The first feedback loop is arranged around the first input loop. The second feedback loop is arranged around the second input loop. The first feedback loop and the second feedback loop are connected end to end in sequence to form the feedback coil.

[0009] In one embodiment, the first feedback loop is arranged around the first input loop to form a first feedback opening. The first input loop is arranged around to form a first input opening. The first input opening is arranged opposite to the first feedback opening.

[0010] In one embodiment, the first feedback loop and the second feedback loop are connected end to end via a feedback loop connection structure. The first input loop and the second input loop are connected end to end via an input loop connection structure. The feedback loop connection structure is arranged opposite to the input loop connection structure.

[0011] In one embodiment, the loop electrode has a first end and a second end, and the first-order gradient series SQUID current sensor further includes a first Josephson structure and a second Josephson structure. The first superconducting film structure of the first Josephson structure is disposed at the first end. The first superconducting film structure of the second Josephson structure is disposed at the second end.

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

[0013] In one embodiment, the first-order gradient series 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 second end. The negative electrode connection structure is respectively connected to the second superconducting film structure of the first Josephson structure and the second superconducting film structure of the second Josephson structure.

[0014] In one embodiment, the present application provides a method for preparing a first-order gradient series 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, a feedback coil and a connection structure.

[0025] The first-order gradient series SQUID current sensor and its preparation method. The first loop electrode, the feedback coil and the input coil are all made of superconducting thin film materials. The loop electrode is a loop formed by connecting multiple curves end to end in sequence (such as Figure 2 The input coil is insulated on the surface of the loop electrode (a part of the SQUID loop), and forms an upper and lower overlapping coupling structure with the SQUID loop. The insulation is used to separate the structures to avoid crosstalk between the currents flowing between them. At this time, the feedback coil, the input coil and the SQUID loop exist independently of each other. The upper and lower overlapping coupling structure of the input coil and the loop electrode makes the coupling between the input coil and the SQUID loop more matched, thereby increasing the coupling coefficient. The input coil is connected to a superconducting transition edge detector (TES) for inputting TES signals.

[0026] At the same time, the feedback coil is spaced apart from the loop electrode, and the input coil is disposed on the surface of the loop electrode, thereby realizing the spacing between the feedback coil and the input coil. 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 and the SQUID loop, and avoiding interference during the detection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 Schematic diagram of the structure of a first-order gradient series SQUID current sensor provided in one embodiment.

[0029] Figure 2 Schematic diagram of the structure of a first-order gradient series SQUID current sensor provided in one embodiment.

[0030] Figure 3 Schematic diagram of the structure of a first-order gradient series SQUID current sensor provided in one embodiment.

[0031] Figure 4 Schematic diagram of the structure of a first-order gradient series SQUID current sensor provided in one embodiment.

[0032] Figure 5 Schematic diagram of the circuit structure of a first-order gradient series SQUID current sensor provided in an embodiment.

[0033] Figure 6 Schematic diagram of the structure of a first-order gradient series SQUID current sensor provided in one embodiment.

[0034] Figure 7 Schematic diagram of a cross-section of a first-order gradient series SQUID current sensor provided in one embodiment.

[0035] Figure 8 Schematic diagram of a cross-section of a first-order gradient series SQUID current sensor provided in one embodiment.

[0036] Description of reference numerals:

[0037] First-order gradient series SQUID current sensor 100, loop electrode 20, input coil 30, feedback coil 40, first loop electrode 210, second loop electrode 220, first input loop 310, second input loop 320, first feedback loop 410, second feedback loop 420, first feedback opening 411, first input opening 311, feedback loop connection structure 430, input loop connection structure 330, first input loop connection structure 331, second input loop connection structure 332, third input A loop connection structure 333, a first Josephson structure 510, a second Josephson structure 520, a first terminal resistor 610, a second terminal resistor 620, a substrate 10, a silicon dioxide film 110, a second superconducting film structure 120, a first insulating structure 130, a first superconducting film structure 160, a connecting through hole 140, a second insulating structure 150, a terminal resistor 60, a first resistor connection structure 611, a second resistor connection structure 612, a third resistor connection structure 621, and a fourth resistor connection structure 622 are provided. DETAILED DESCRIPTION

[0038] 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.

[0039] 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.

[0040] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there are no intervening elements or layers. 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 parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are merely 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 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.

[0041] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like 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 accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0042] 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.

[0043] 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.

[0044] See also Figure 1 and Figure 2 The present application provides a first-order gradient series SQUID current sensor 100. The first-order gradient series SQUID current sensor 100 includes a loop electrode 20, an input coil 30, and a feedback coil 40. 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 feedback coil 40 is spaced apart from the loop electrode 20. The feedback coil 40 is disposed around the loop electrode 20. The input coil 30 is used to input a superconducting transition edge detector signal. The feedback coil 40 is used for flux locking.

[0045] In this embodiment, the first loop electrode 20, the feedback coil 40 and the input coil 30 are all made of superconducting thin film materials. The loop electrode 20 is a loop formed by connecting multiple curves end to end in sequence (such as Figure 2 The input coil 30 is insulated and arranged on the surface of the loop electrode 20 (a part of the SQUID loop), 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. At this time, the feedback coil, the input coil and the SQUID loop exist independently of each other. The upper and lower overlapping coupling structure of the input coil 30 and the loop electrode 20 makes the coupling between the input coil 30 and the SQUID loop more matched, thereby increasing the coupling coefficient. The input coil 30 is connected to a superconducting transition edge detector (TES) for inputting a TES signal.

[0046] At the same time, the feedback coil 40 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 spaced arrangement of the feedback coil 40 and the input coil 30. When the feedback coil 40 is connected to the test system, that is, connected to the flux locking loop, an appropriate current will flow into the feedback coil 40 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.

[0047] In one embodiment, the loop electrode 20 includes a first loop electrode 210 and a second loop electrode 220. The second loop electrode 220 is connected to the first loop electrode 210 end to end to form the loop electrode 20. The second loop electrode 220 and the first loop electrode 210 are symmetrically arranged.

[0048] In this embodiment, Figure 2 The first loop electrode 210 and the second loop electrode 220 are as shown in Figure 2 The bottom gray area (or Figure 2 The second loop electrode 220 is connected to the first loop electrode 210 end to end in sequence to form a complete connection loop. At the same time, the second loop electrode 220 is symmetrically arranged with the first loop electrode 210. 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.

[0049] See also Figure 3 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 from the first loop electrode 210. The second input loop 320 is insulated from 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.

[0050] 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 3 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 the 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 TES detector signal readout.

[0051] The first input loop 310 is arranged on the surface of the first loop electrode 210 and is insulated. The second input loop 320 is arranged on the surface of the second loop electrode 220 and is insulated. 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. Thus, the coupling between the input coil 30 and the SQUID loop is more matched, and the coupling coefficient is increased.

[0052] In one embodiment, the number of turns of the input coil 30, the number of loops of the first input loop 310, and the number of loops of the second input loop 320 are all equal. Figure 3 As shown, the number of turns of the input coil 30 is 2, and the number of loops of the first input loop 310 and the second input loop 320 are both 2. In order to improve the coupling coefficient between the input coil 30 and the SQUID loop, the number of turns of the input coil in the present application is greater than or equal to 2.

[0053] See also Figure 1 In one embodiment, the feedback coil 40 includes a first feedback loop 410 and a second feedback loop 420. The first feedback loop 410 is arranged around the first input loop 310. The second feedback loop 420 is arranged around the second input loop 320. The first feedback loop 410 and the second feedback loop 420 are connected end to end in sequence to form the feedback coil 40.

[0054] In this embodiment, the first feedback loop 410 and the second feedback loop 420 are connected end to end in sequence to form the feedback coil 40. Figure 1 When the feedback coil 40 is connected to the flux locking loop, an appropriate current will flow into the feedback coil 40 for flux locking, providing a stable magnetic field environment for the input coil 30 and the SQUID loop to avoid interference during the detection process.

[0055] The first feedback loop 410 is arranged around the first input loop 310, and at this time, the first feedback loop 410 is also arranged around the first loop electrode 210. The second feedback loop 420 is arranged around the second input loop 320, and at this time, the second feedback loop 420 is also arranged around the second loop electrode 220. By surrounding the first feedback loop 410 and the second feedback loop 420, a better surrounding magnetic field environment can be provided. At the same time, the first feedback loop 410 and the second feedback loop 420 are respectively spaced apart from the first input loop 310 and the second input loop 320 to avoid mutual interference. Furthermore, the feedback coil 40, the input coil 30 and the SQUID loop exist independently of each other.

[0056] See also Figure 3 In one embodiment, the first feedback loop 410 is arranged around the first input loop 310 to form a first feedback opening 411. The first input loop 310 is arranged around to form a first input opening 311. The first input opening 311 is arranged opposite to the first feedback opening 411.

[0057] In this embodiment, the first loop electrode 210 and the second loop electrode 220 form a symmetrical structure. The first loop electrode 210, the first input loop 310 and the first feedback loop 410, the second loop electrode 220, the second input loop 320 and the second feedback loop 420, as a whole, form a symmetrical structure that is symmetrical about a horizontal line. At the same time, when the feedback coil 40 is arranged around the input coil 30, a first feedback opening 411 is formed. When the input coil 30 is insulated and arranged on the surface of the loop electrode 20, a first input opening 311 is also formed. At this time, the first input opening 311 and the first feedback opening 411 are arranged relative to each other, and can be distributed on both sides of the first loop electrode 210. At this time, the overall structure of the first-order gradient series SQUID current sensor 100 forms a symmetrical structure, which can offset the interference generated by itself.

[0058] In one embodiment, the second feedback loop 420 is disposed around the second loop electrode 220 to form a second feedback opening 421. The second input loop 320 is insulated and disposed on the surface of the second loop electrode 220 to form a second input opening 321. The second input opening 321 and the second feedback opening 421 are disposed on opposite sides of the second loop electrode 220.

[0059] In this embodiment, the relative arrangement of the first input opening 311 and the first feedback opening 411 is similar to that in the above embodiment. The first input opening 311, the first feedback opening 411, the second input opening 321, and the second feedback opening 421 achieve symmetry of the overall structure.

[0060] See also Figure 4 In one embodiment, the first feedback loop 410 and the second feedback loop 420 are connected via a feedback loop connection structure 430 (eg, Figure 4 The first input loop 310 and the second input loop 320 are connected end to end via an input loop connection structure 330 (shown as a solid line in the middle). Figure 4 The number of the input loop connection structures 330 is related to the number of turns of the input coil 30, for example, Figure 4As shown, when the number of turns of the input coil 30 is 2 (the number of loops of the first input loop 310 and the number of loops of the second input loop 320 are both 2), the input loop connection structure 330 includes a first input loop connection structure 331, a second input loop connection structure 332 and a third input loop connection structure 333, and the number of the input loop connection structures 330 is 3. The feedback loop connection structure 430 is arranged opposite to the input loop connection structure 330.

[0061] In this embodiment, the feedback loop connection structure 430 and the input loop connection structure 330 are opposite to the two sides of the loop electrode 20, and the head and tail of each structure are connected in sequence to form the feedback coil 40 and the input coil 30. At this time, the first feedback loop 410, the second feedback loop 420, the feedback loop connection structure 430, the first input loop 310, the second input loop 320 and the input loop connection structure 330 form a symmetrical structure about the horizontal line and the vertical line (such as Figure 4 As shown), it is used to offset the interference generated by itself.

[0062] See also Figure 2 In one embodiment, the loop electrode 20 has a first end and a second end, and the first-order gradient series SQUID current sensor 100 further includes a first Josephson structure 510 and a second Josephson structure 520. The first superconducting film structure of the first Josephson structure 510 is disposed at the first end. The first superconducting film structure of the second Josephson structure 520 is disposed at the second end.

[0063] In this embodiment, the first superconducting thin film structure 160 (lower Nb film) of the first Josephson structure 510 is connected to the first end of the loop electrode 20, and the first superconducting thin film structure 160 (lower Nb film) of the second Josephson structure 520 is connected to the second end of the loop electrode 20, 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 5 shown.

[0064] Furthermore, the loop electrode 20 is an open loop having a first end and a second end. The first superconducting film structure of the first Josephson structure 510 is arranged at the first end, and the first superconducting film structure of the second Josephson structure 520 is arranged at the second end, so that the loop electrode 20 is arranged in series between the first Josephson structure 510 and the second Josephson structure 520, forming a SQUID loop of a first-order gradient series inductance structure. The SQUID loop increases the coupling area with the input coil 30 and the feedback coil 40 by means of series inductance.

[0065] Therefore, the first end and the second end of the loop electrode 20 are connected to the first Josephson structure 510 and the second Josephson structure 520 respectively, forming a SQUID loop with a first-order gradient structure, which effectively offsets external magnetic field interference.

[0066] See also Figure 1 In one embodiment, the first-order gradient series 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 structure 510. The second terminal resistor 620 is connected in parallel with the second Josephson 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 structure 510, the second Josephson structure 520, the first terminal resistor 610 and the second terminal resistor 620 form a complete SQUID loop.

[0067] In this embodiment, the first terminal resistor 610 and the second terminal resistor 620 are symmetrical about a vertical line to form a symmetrical structure. At the same time, the first terminal resistor 610 is connected in parallel with the first Josephson structure 510 through a first resistor connection structure 611 and a second resistor connection structure 612. Specifically, the first resistor connection structure 611 is connected to the second superconducting film structure 120 (upper Nb film) of the first Josephson structure 510. The second resistor connection structure 612 is connected to the first superconducting film structure 160 (lower Nb film) of the first Josephson structure 510, that is, the loop electrode 20.

[0068] Similarly, the second terminal resistor 620 is connected in parallel with the second Josephson structure 520 through the third resistor connection structure 621 and the fourth resistor connection structure 622. Specifically, the third resistor connection structure 621 is connected to the second superconducting film structure 120 (upper Nb film) of the second Josephson structure 520. The fourth resistor connection structure 622 is connected to the first superconducting film structure 160 (lower Nb film) of the second Josephson structure 520, that is, the loop electrode 20.

[0069] In one embodiment, the first-order gradient series SQUID current sensor 100 further includes a positive electrode connection structure and a negative electrode connection structure. The positive electrode connection structure is connected to the second end. The negative electrode connection structure is connected to the second superconducting thin film structure (upper Nb film) of the first Josephson structure 510 and the second superconducting thin film structure 120 (upper Nb film) of the second Josephson structure 520, respectively.

[0070] In this embodiment, the positive and negative electrodes of the SQUID loop formed by connecting the first Josephson structure 510 and the second Josephson structure 520 in parallel are led out through the positive electrode connection structure and the negative electrode connection structure. The positive and negative electrodes of the power supply can be connected through the positive electrode connection structure and the negative electrode connection structure to detect the voltage of the SQUID loop, thereby obtaining the change of the TES signal and realizing the TES detector signal readout.

[0071] In one embodiment, the negative electrode connection structure, 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 structure 510, the second superconducting film structure 120 (upper Nb film) of the second Josephson 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 are Nb film lead layer structures.

[0072] In one embodiment, the first-order gradient series SQUID current sensor 100 further includes a plurality of auxiliary structures. Through the auxiliary structures, the structure of the current sensor 100 is symmetrical to offset the interference caused by the structure of the current sensor 100 itself.

[0073] In one embodiment, the feedback coil 40 is provided with an insulating structure at the contacting parts with the loop electrode 20 and the input coil 30 to separate them and avoid the crosstalk between the currents flowing therebetween. At this time, the feedback coil 40, the input coil 30 and the SQUID loop exist independently of each other.

[0074] See also Figure 6 In one embodiment, the loop electrode 20 further includes a first curved structure 231, a second curved structure 232, and a third curved structure 233. The second curved structure 232 is disposed between the first curved structure 231 and the third curved structure 233. The first end of the first curved structure 231 is connected to the first end of the second curved structure 232. The second end of the first curved structure 231 is connected to the first end of the third curved structure 233. The second end of the second curved structure 232 is the first end of the loop electrode 20. The second end of the third curved structure 233 is the second end of the loop electrode 20.

[0075] In this embodiment, the first end of the first curved structure 231 is connected to the first end of the second curved structure 232, and the second end of the first curved structure 231 is connected to the first end of the third curved structure 233, forming a curved loop. At this time, a loop electrode 20 having a first end and a second end is formed by the first curved structure 231, the second curved structure 232, and the third curved structure 233. The first superconducting film structure of the first Josephson structure 510 is connected to the first end of the loop electrode 20, and the first superconducting film structure of the second Josephson structure 520 is connected to the second end of the loop electrode 20, forming a series inductance structure, thereby increasing the coupling area with the input coil 30 and the feedback coil 40.

[0076] In one embodiment, the second end of the first curved structure 231 is connected to the first end of the third curved structure 233 through the first port connection structure 212. The first port connection structure 212 is disposed on the surface of the first curved structure 231, the surface of the second curved structure 232, and the surface of the third curved structure 233. The first port connection structure 212 and the second curved structure 232 are insulated from each other.

[0077] In this embodiment, the first port connection structure 212 is connected to the second end of the first curved structure 231 and the first end of the third curved structure 233. At this time, the first curved structure 231 and the third curved structure 233 are symmetrical about the third curved structure 233, thereby forming a symmetrical structure, which is conducive to offsetting the interference caused by its own structure. At the same time, the first port connection structure 212 and the second curved structure 232 are insulated, and the first port connection structure 212 crosses the second curved structure 232 and is connected to the first curved structure 231 and the third curved structure 233 respectively, forming a symmetrical first loop electrode 210 and the second loop electrode 220.

[0078] In one embodiment, the first end of the first curved structure 231 is connected to the first end of the second curved structure 232 through the second port connection structure 211 .

[0079] In this embodiment, the first end of the first curve structure 231 and the first end of the second curve structure 232 are connected in series end to end through the second port connection structure 211. The structure of the second port connection structure 211 is the same as that of the negative electrode connection structure, which is used to achieve a symmetrical structural setting, offset the interference generated by itself, and thus avoid interference during the detection process.

[0080] Therefore, the first curve structure 231 , the second curve structure 232 , the third curve structure 233 , the first port connection structure 212 , and the second port connection structure 211 are connected in series to form the loop electrode 20 .

[0081] See also Figure 7 and Figure 8 In one embodiment, the present application provides a method for preparing a first-order gradient series SQUID current sensor, comprising:

[0082] S10, providing a substrate 10, and preparing a silicon dioxide film 110 on the surface of the substrate 10;

[0083] 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;

[0084] S30, etching the second superconducting film layer to the first insulating layer to form a second superconducting film structure 120;

[0085] 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;

[0086] S50, etching the first superconducting thin film layer to the silicon dioxide thin film 110, to form the loop electrode 20 and the first superconducting thin film structure 160;

[0087] 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;

[0088] 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;

[0089] S80, preparing a terminal resistor 60 on the surface of the second insulating structure 150 between the plurality of connecting through holes 140;

[0090] 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;

[0091] S100, etching the lead superconducting thin film layer to the second insulating structure 150, forming the input coil 30, the feedback coil 40 and the connection structure.

[0092] 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 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 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 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 and the first superconducting film structure 160 of the Josephson junction. At this point, 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. The SQUID loop pattern is as follows: Figure 2 At this time, the first superconducting film structure 160, the second superconducting film structure 120, and the first insulating structure 130 form a Josephson structure.

[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 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 connection through hole 140. The negative electrode connection structure can be led out through the connection through hole 140. At the same time, the second insulating structure 150 can be realized Figure 2 The loop electrode 20, the input coil 30, the feedback coil 40 and other overlapping structures are isolated and insulated. In the S80, the terminal resistor 60 (the first terminal resistor 610 and the second terminal resistor 620) (see Figure 1The structure in the middle is arranged close to the Josephson junction and serves as the terminal resistance of the current sensor 100.

[0095] 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, and the lead superconducting film layer is a Nb film. In the S100, the lead superconducting film layer (Nb film) is etched to form the feedback coil 40, the input coil 30 and the connection structure, etc. The connection structure may be the connection structure involved in the above embodiment.

[0096] Therefore, through the preparation method of the first-order gradient series 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 current sensor 100 prepared by the preparation method of the first-order gradient series SQUID current sensor can increase the coupling area, effectively offset the external magnetic field interference, reduce the parasitic capacitance, and is more conducive to the readout of the TES signal.

[0097] 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 5nm to 30nm. The thickness of the second superconducting thin film layer (upper Nb film) is 100nm to 500nm. The thickness of the second insulating structure 150 is 200nm to 600nm. The thickness of the terminal resistor 60 (PdAu film) is 50nm to 500nm. The thickness of the lead superconducting thin film layer (Nb film) is 300nm to 800nm.

[0098] 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 to 5000 mTorr, and the oxidation time is 5 hours to 24 hours. The area of ​​the Josephson junction region (the second superconducting film structure 120) is 1 μm 2 ~100μm 2 .

[0099] Specifically, in one embodiment, the method for preparing the first-order gradient series SQUID current sensor comprises:

[0100] When growing 100nm thick SiO 2 The Nb / AlO film 110 is prepared by magnetron sputtering on a 2-inch single crystal high-resistance silicon wafer 10. x / Nb three-layer film with thicknesses 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.

[0101] 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).

[0102] 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 .

[0103] Based on the above steps, a third photolithography is performed to etch the bottom Nb film to obtain a SQUID loop pattern.

[0104] Based on the above steps, a 200nm thick SiO 2 The film is then subjected to a third photolithography step and the SiO 2 The remaining SiO 2 The film is the second insulating structure 150 .

[0105] 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.

[0106] 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 feedback coil 40, the input coil 30 and the connection structure pattern.

[0107] Based on the above steps, the 2-inch sample was sliced ​​to obtain a first-order gradient series SQUID current sensor.

[0108] In one embodiment, the method for preparing the first-order gradient series SQUID current sensor comprises:

[0109] When growing 1000nm thick SiO 2 The Nb / AlO film 110 is prepared by magnetron sputtering on a 2-inch single crystal high-resistance silicon wafer 10. x / Nb three-layer film with thicknesses 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.

[0110] 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).

[0111] 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 .

[0112] Based on the above steps, a third photolithography is performed to etch the bottom Nb film to obtain a SQUID loop pattern.

[0113] Based on the above steps, a 600nm thick SiO 2 The film is then subjected to a third photolithography step and the SiO 2 The remaining SiO 2 The film is the second insulating structure 150 .

[0114] 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 then the PdAu resistor 60 is obtained by peeling.

[0115] 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 feedback coil 40, the input coil 30 and the connection structure pattern.

[0116] Based on the above steps, the 2-inch sample was sliced ​​to obtain a first-order gradient series SQUID current sensor.

[0117] 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.

[0118] 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.

[0119] 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 series SQUID current sensor, characterized in that: include: Loop electrodes; An input coil is arranged on the surface of the loop electrode, and the input coil is insulated from the loop electrode; A feedback coil is arranged at a distance from the loop electrode, and the feedback coil is arranged around the loop electrode; The input coil is used to input a superconducting transition edge detector signal, and the feedback coil is used for magnetic flux locking; The loop electrode comprises: a first loop electrode; a second loop electrode, connected end to end with the first loop electrode in sequence to form the loop electrode; the second loop electrode is symmetrically arranged with the first loop electrode; The input coil comprises: a first input loop, which is insulated from the first loop electrode; a second input loop, which is insulated from 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; The feedback coil includes: a first feedback loop, which is arranged around the first input loop; a second feedback loop, which is arranged around the second input loop; the first feedback loop and the second feedback loop are connected end to end in sequence to form the feedback coil; The first feedback loop is arranged around the first input loop to form a first feedback opening; the first input loop is arranged around to form a first input opening, and the first input opening is arranged opposite to the first feedback opening.

2. The first-order gradient series SQUID current sensor according to claim 1, characterized in that: The first feedback loop and the second feedback loop are connected end to end via a feedback loop connection structure; The first input loop and the second input loop are connected end to end via an input loop connection structure; The feedback loop connection structure is arranged opposite to the input loop connection structure.

3. The first-order gradient series SQUID current sensor according to claim 1, characterized in that: The loop electrode has a first end and a second end, and the first-order gradient series SQUID current sensor further includes: a first Josephson structure, wherein a first superconducting thin film structure of the first Josephson structure is disposed at the first end; A second Josephson structure, wherein the first superconducting thin film structure of the second Josephson structure is arranged at the second end.

4. The first-order gradient series SQUID current sensor according to claim 3, characterized in that: The first-order gradient series SQUID current sensor also includes: A first terminal resistor connected in parallel with the first Josephson structure; A second terminal resistor is connected in parallel with the second Josephson structure.

5. The first-order gradient series SQUID current sensor according to claim 3, characterized in that: The first-order gradient series SQUID current sensor also includes: a positive electrode connection structure connected to the second end; The negative electrode connection structure is connected to the second superconducting film structure of the first Josephson structure and the second superconducting film structure of the second Josephson structure respectively.

6. The first-order gradient series SQUID current sensor according to claim 1, characterized in that: The number of turns of the input coil, the number of loops of the first input loop, and the number of loops of the second input loop are all equal.

7. The first-order gradient series SQUID current sensor according to claim 1, characterized in that: The first loop electrode, the first input loop and the first feedback loop, and the second loop electrode, the second input loop and the second feedback loop, as a whole, form a symmetrical structure that is symmetrical about a horizontal line.

8. The first-order gradient series SQUID current sensor according to claim 1, characterized in that: The second feedback loop is arranged around the second loop electrode to form a second feedback opening.

9. The first-order gradient series SQUID current sensor according to claim 8, characterized in that: The second input loop is insulated and arranged on the surface of the second loop electrode to form a second input opening; the second input opening and the second feedback opening are arranged on opposite sides of the second loop electrode.

10. A method for preparing a first-order gradient series SQUID current sensor 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 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, a feedback coil and a connection structure.

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