A method for testing a josephson junction and applications thereof

Abstract

The application discloses a Josephson junction testing method and application thereof, and belongs to the field of quantum chip manufacturing. The Josephson junction testing method comprises element measurement on at least a barrier layer of a Josephson junction. By analyzing and processing the measured element information, element-related target content in the corresponding junction can be obtained, so that the quality of the manufactured Josephson junction can be evaluated, or the advantages and disadvantages of the junction manufacturing process adopted can be judged, so that the process can be improved.

Description

Technical Field

[0001] This application belongs to the field of quantum information, especially the field of quantum chip manufacturing, and in particular, this application relates to one. Background Technology

[0002] The Josephson junction is a core component of quantum chips. The Josephson structure is a sandwich-shaped Al-Al₂O₃-Al structure. The middle layer, Al₂O₃, is an oxide layer with a thickness of approximately 1 nm to 2 nm. This oxide layer significantly influences the performance of the Josephson junction. Currently, research on Josephson junctions mainly focuses on junction resistance, with a lack of research on its elemental composition. Summary of the Invention

[0003] The present application provides a Josephson junction testing method and its application, which can be used to perform elemental analysis on Josephson junctions to obtain information related to the elemental characteristics of Josephson junctions, thereby enabling the evaluation and analysis of Josephson junctions and their manufacturing processes.

[0004] The solution presented in this application is implemented through the following steps.

[0005] In the first aspect, examples of this application present a Josephson knot testing method.

[0006] The method includes:

[0007] Provide a Josephson junction having a first superconductor, a barrier layer, and a second superconductor stacked sequentially; and

[0008] At least elemental measurements should be performed on the barrier layer.

[0009] Currently, research on Josephson junctions focuses primarily on their junction resistance and fabrication process. However, studies using elemental analysis to assess and determine junction quality are rare. Therefore, this application's example involves elemental measurements of at least the barrier layer of the Josephson junction for elemental analysis—such as the type, content, and distribution of elements—which provides positive implications for qualitative or quantitative evaluation of junction quality and process improvement, such as shortening manufacturing cycles, increasing yield, and improving product consistency.

[0010] According to some examples of this application, elemental measurements are performed to determine the content of one or more elements in the barrier layer;

[0011] Alternatively, elemental measurements are performed to determine the content of the same element in the first superconductor, the barrier layer, and the second superconductor.

[0012] According to some examples in this application, the content reflects the distribution of elements in the Josephson outcome partial or bulk phase.

[0013] In a second aspect, examples of this application present a Josephson knot test method. It includes:

[0014] A Josephson junction is provided, having a cross-section defined in the thickness direction. The barrier layer of the Josephson junction in the stacked region has length and thickness dimensions, which are defined by the edge of the barrier layer within the cross-section.

[0015] Measurement operations are performed on at least two regions along the length dimension of the barrier layer to obtain at least two measurement data that correspond one-to-one with the number of regions, and the measurement data contains feature information of various elements in the corresponding regions;

[0016] Process at least two sets of measurements to obtain analytical results for various elements in the Josephson junction.

[0017] By performing measurements on at least two regions along the length of the barrier layer, elemental measurement data from multiple regions can be obtained. This provides a larger data sample, thus more accurately reflecting the elemental composition of the measured Josephson junction. Consequently, utilizing a more realistic and accurate representation of the elemental composition of the junction facilitates the acquisition of more effective information regarding the quality and manufacturing process of the Josephson junction.

[0018] According to some examples of this application, the Josephson knot test method includes one or more of the following features;

[0019] First characteristic: Characteristic information includes: the number of atoms of various elements in the corresponding region, or the content of the number of atoms of various elements in the corresponding region;

[0020] Second characteristic: In the step of processing at least two measurement data to obtain the analytical results of various elements in the Josephson junction, the analytical results are the atomic number content;

[0021] The third feature: processing at least two measurement data to obtain analytical results of various elements in Josephson knots includes: performing single-element content acquisition operations multiple times to obtain the content of various elements, wherein the elements in each acquisition operation are different;

[0022] The operations for obtaining the content of a single element include:

[0023] Select a single element as the target element, extract the content of the target element in each measurement data, and calculate the arithmetic mean of the content of the target element in all measurement data.

[0024] According to some examples of this application, the measurement operation is performed by scanning the Josephson node using a measuring device;

[0025] The measuring equipment includes aberration scanning transmission electron microscope and X-ray energy dispersive spectrometer, or the measurement includes aberration scanning transmission electron microscope and electron energy loss spectrometer.

[0026] According to some examples in this application, the Josephson knot test method includes a first limitation or a second limitation;

[0027] First constraint: The measurement operation is performed in a linear region, which is defined along the thickness direction of the Josephson junction. The measurement operation is performed by scanning the linear region of the Josephson junction in the thickness direction, wherein the size of the linear region measured in the thickness direction is equal to or greater than the thickness of the barrier layer.

[0028] Second limitation: The measurement operation is performed on the surface region, which is defined along the thickness and length directions of the Josephson junction. The measurement operation is: to perform a surface scan on the surface region of the Josephson junction, wherein the dimension of the surface region measured in the thickness direction is equal to or greater than the thickness dimension of the barrier layer, and the dimension of the surface region measured in the length direction is less than the length dimension of the barrier layer.

[0029] According to some examples of this application, the Josephson knot has a width dimension measured in the direction perpendicular to the cross section;

[0030] The width dimension is less than or equal to a preset value, and the preset value depends on the measuring equipment used in the measurement operation, so that the measurement operation obtains measurement data associated with the elements in the Josephson junction bulk phase. Thus, in the step of processing at least two measurement data to obtain the analysis results of various elements in the Josephson junction, the analysis results reflect the content of various elements in the Josephson junction as a whole.

[0031] According to some examples of this application, the cross section of the Josephson junction is obtained by focused ion beam cutting, and the cutting operation is carried out in a manner that gradually approaches the barrier layer from a direction perpendicular to the cross section.

[0032] The Josephson junction has an embedded film of superconductor layer embedded in the Josephson junction at a distance from the stacked region. The embedded film is configured to indicate the position to stop cutting during the dicing operation.

[0033] In a third aspect, some examples of this application present an application of the aforementioned Josephson knot testing method in the fabrication or evaluation of Josephson knots.

[0034] According to some examples of this application, the Josephson junction test method has been used to analyze the relationship between the junction resistance of the Josephson junction and the elemental content of the barrier layer.

[0035] Alternatively, the barrier layer is an oxide layer formed by partially oxidizing the superconductor layer, and the Josephson junction test method is used to analyze the uniformity of oxidation;

[0036] Alternatively, the barrier layer is an oxide layer formed by partially oxidizing the superconductor layer, and the Josephson junction test method is used to analyze the oxide thickness.

[0037] At least some of the beneficial effects of the example solution in this application are illustrated by the following description:

[0038] By performing elemental analysis on at least the barrier layer of the Josephson junction, information related to the measurement items can be obtained. This information can then be used to assess the quality of the Josephson junction and to optimize and improve the manufacturing process in order to obtain Josephson junctions that better meet design expectations and are of higher quality. Attached Figure Description

[0039] To illustrate this more clearly, the accompanying drawings used in the description will be briefly introduced below.

[0040] Figure 1 This is a flowchart illustrating the first Josephson knot testing method in this application example;

[0041] Figure 2 This is a flowchart illustrating the second Josephson knot testing method in this application example;

[0042] Figure 3 public Figure 2 A schematic diagram of the cross-sectional structure of the Josephson knot in the Josephson knot test method shown;

[0043] Figure 4 public Figure 2 The diagram shows a line scan method in the Josephson junction testing procedure. Detailed Implementation

[0044] In superconducting quantum computers, the Josephson junction, which is widely used, has a three-layer stacked / layered structure. It typically employs an aluminum-alumina-aluminum structure. The two superconducting aluminum layers are constructed in a roughly orthogonal manner as elongated strips of a certain thickness. The alumina layer is a very thin structure, which can be described as a barrier layer.

[0045] Typically, the quality of a Josephson junction directly affects the quality of the superconducting qubits based on it, and thus significantly influences the performance of superconducting quantum chips. The industry focuses primarily on the junction resistance of the Josephson junction.

[0046] In the example of this application, the inventors have been able to analyze Josephson knots in a more microscopic and reliable manner by performing elemental characterization of the knots.

[0047] Generally, Josephson junctions can be formed through thermal oxidation. For example, high-purity oxygen is diffused onto the aluminum surface to react and form a barrier layer. Elemental analysis of the Josephson junction provides a clearer picture of the oxidation process and its results, such as the uniformity of oxidation, the thickness of the oxide layer, and the relationship between junction resistance and the distribution and abundance of elements in the junction. Therefore, elemental characterization can provide quantifiable data for improving the manufacturing process of Josephson junctions.

[0048] Therefore, in the example, the inventors proposed a Josephson knot test method. For example... Figure 1 As shown, it includes providing or manufacturing a Josephson junction and performing elemental measurements on the Josephson junction. The Josephson junction has a first superconductor, a barrier layer, and a second superconductor stacked sequentially. Therefore, the measurements are at least performed on the barrier layer of the Josephson junction as elemental measurements.

[0049] The measurement results can vary depending on the specific measurement being performed. In some examples, elemental measurements are conducted to determine the content of one or more elements in the barrier layer of a Josephson junction. For example, this could be used to determine the content of aluminum, oxygen, or other impurity elements such as carbon (which can be introduced, for example, through air, unclean equipment, reagents, raw materials, etc.).

[0050] When elemental measurements of a Josephson junction are not limited to the barrier layer but extend to the superconductor layer, in some examples, elemental measurements of the junction can also be performed to determine the content of the same element in the first superconductor, barrier layer, and second superconductor. For example, the content of aluminum in the first, barrier, and second superconductor layers. Alternatively, the content of oxygen in the first, barrier, and second superconductor layers can be considered.

[0051] Furthermore, depending on the choice of measuring equipment and methods, the measured element content can reflect the distribution of the element in the Josephson outcome partial or bulk phase.

[0052] For example, if the measurement region only covers the barrier layer, the aluminum content reflects the aluminum content in the barrier layer. Alternatively, if the measurement region is designed to cover only a portion of the first superconductor, the barrier layer, and the second superconductor, the measured content reflects the distribution of the element in the Josephson terminal partial phase.

[0053] If the measured area covers multiple regions of the Josephson junction, and each of these regions includes portions located in the first superconductor layer, the barrier layer, and the second barrier layer, then it can be relatively considered to reflect the distribution of elements in the bulk phase of the Josephson junction.

[0054] In short, the local phase and the bulk phase represent the size of the measurement region compared to the overall Josephson junction, respectively. For example, for a one-dimensional structure, if elemental measurements are performed at one or more locations not covering the entire length, it reflects the elemental content in the local phase. Conversely, if the entire length is measured, it reflects the elemental content in the bulk phase.

[0055] For example, for a two-dimensional structure defined by length and width, the element content measured by selecting one or more regions consisting of the full width and part of the length can be considered as the element content in the local phase; while the element measurement by selecting the full width and full length can be considered as the element content in the bulk phase.

[0056] For example, for a three-dimensional structure defined by thickness, length, and width, the element content obtained by measuring one or more locations arbitrarily selected from the entire length and width range and part of the thickness range can be considered as the element content of the local phase, while the opposite can be considered as the element content of the bulk phase.

[0057] For elemental measurements, elemental analysis using TEM (transmission electron microscopy) can be employed, for example. A single line scan allows for the determination of the elemental distribution along a specific line within the Josephson junction. Therefore, the change in the percentage of detected atoms along the scan line can be used to infer the change in elemental content along that line. In some analyses, this measurement reflects the cross-sectional elemental content and its variation along that scan line, but it is difficult to determine the percentage and variation of elemental content across the entire barrier layer, such as the oxide layer (or alternatively, alumina).

[0058] As a beneficial attempt and improvement, in some examples, a higher-resolution spherical aberration TEM can be used to perform continuous line scans of the oxide layer located between the first and second superconductors, and then the data can be superimposed to characterize the overall elemental content and variations of the oxide layer more accurately. Alternatively, continuous surface scanning of spherical aberration electron microscopy can be used to characterize the bulk elemental content of the oxide layer to a greater extent.

[0059] In other examples, the inventors have also proposed a Josephson knot test method, which includes the following steps, combined with Figure 2 , Figure 3 and Figure 4For ease of explanation, the following examples use brief headings to summarize the steps, but these should not be considered as limitations on the Josephson knot test method mentioned.

[0060] Step S101: Provide Josephson knot

[0061] In this step, the Josephson junction has a cross-section defined along the thickness direction (from the first superconductor to the second superconductor). Wherein, according to Figure 3 The cross-section is shown by a sectional view of the Josephson junction cut along the dashed line. The barrier layer of the Josephson junction in the stacked region has length and thickness dimensions, which are defined by the edges of the barrier layer within the cross-section.

[0062] exist Figure 3 In the diagram, the barrier layer of the stacked region is represented by a thick dashed frame. Furthermore, its length dimension is determined by… Figure 3 The horizontal direction of the indicated orientation is determined by measurement, while the thickness dimension is determined by... Figure 3 The vertical direction of the indicated orientation is determined by measurement, while the width dimension is determined by... Figure 3 The orientation shown is determined by measurements perpendicular to the plane of the paper. In superconducting quantum chips, Josephson junctions typically have a sandwich structure. This consists of two superconductor layers (elongated strips, such as aluminum films) and a barrier layer (an aluminum oxide film, for example, formed by oxidation of the surface of an aluminum film first fabricated therein) between and in contact with both layers. Therefore, the stacked region generally represents the overlapping area of ​​the two superconductor layers as observed in the thickness direction.

[0063] The cross-section is obtained by cutting the Josephson junction. The cutting direction is along the thickness direction of the Josephson junction. Considering the size of the Josephson junction, the cutting operation can be achieved through etching in integrated circuit processes or micro / nano fabrication techniques, such as laser etching, chemical etching, plasma etching, etc. Alternatively, it can be further combined with other processes, such as photolithography. The specific implementation of the cutting operation can be selected according to actual needs, and this application does not have any particular limitations in this regard.

[0064] For example, in this example, a focused ion beam (FIB) is chosen for etching to achieve the cut. Specifically, the FIB is used to etch towards the Josephson junction. For instance, using the substrate to which the Josephson junction is attached as a reference, the FIB is incident perpendicularly to the substrate surface. As mentioned earlier, the Josephson junction is relatively thin; therefore, the FIB cuts through the junction, meaning the ion beam can pass through the first superconductor, the barrier layer, and the second superconductor. Thus, the cutting operation directly yields a cross-section exposing the first superconductor, the barrier layer, and the second superconductor.

[0065] Furthermore, due to the fragility of the Josephson junction, cutting it using FIB may result in damage at undesirable locations. Therefore, the Josephson junction can be protected beforehand. This is typically achieved by covering the junction region with a protective film. For example, protection can be achieved by depositing a Pt metal film. The Pt metal film covering region, for example, involves at least the stacked region of the first superconductor, the barrier layer, and the second superconductor.

[0066] Based on this, for example, cutting can be performed from one side to the other along the width direction. Furthermore, considering the potential requirements for junction width during subsequent elemental measurements and the need to balance cutting efficiency, in some examples, cutting from both sides towards the middle along the width direction can be considered. Generally, the cutting operation is performed perpendicular to the cross-section, gradually approaching the barrier layer from a point away; cutting can be stopped when the cutting position is reached.

[0067] Furthermore, when cutting is performed in the presence of a protective layer, determining the cutting position in real time can become more difficult. Therefore, in some examples, it is possible to configure a marker to stop the cutting operation.

[0068] In other words, in some examples, the cross-section of the Josephson junction is obtained by focused ion beam cutting. The Josephson junction has an embedded film. This embedded film is configured in a stacked region away from the Josephson junction and is embedded into the superconducting layer of the Josephson junction. The embedded film is configured to indicate the location where cutting stops during the FIB cutting operation (therefore, the embedded film can also be referred to as a stop layer).

[0069] Since the embedded film is located in the superconductor of the Josephson junction, when the cut is made to form a cross-section, when the cut operation has reached the position of the embedded film (the position of the embedded film has been associated with the barrier layer when the embedded film was designed), the cross-section exposes the embedded film in addition to the first superconductor, the barrier layer, and the second superconductor layer.

[0070] Therefore, during the cutting process, the presence of the embedded membrane in the cross-section indicates whether the cut has been completed. In short, the cutting operation primarily aims to obtain the cross-section of the barrier layer (and potentially the required width). Since directly observing a very thin (nanoscale) barrier layer is difficult, an embedded membrane with a thickness greater than the barrier layer (e.g., a thickness on the micrometer scale) is used as the object of observation. Thus, during the cutting process, the location of the cut can be determined by observing the presence of the embedded membrane within the cross-section.

[0071] The fabrication of a Josephson junction or its dicing operation may require the deposition of one or more materials, such as superconductors, dielectrics, and / or metals. Depending on the materials chosen, these materials can be deposited using deposition processes such as chemical vapor deposition, physical vapor deposition (e.g., evaporation or sputtering), epitaxial techniques, or other deposition processes, exemplary of which include ion beam assisted deposition (IBAD), evaporation, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), chemical vapor deposition (CVD), sol-gel deposition, and magnetron sputtering.

[0072] In addition, it may be necessary to remove one or more materials during the manufacturing process. Depending on the material to be removed, the removal process may include, for example, wet etching, dry etching, or lift-off processes; during which known lithographic techniques (e.g., photolithography or electron beam lithography) may be used to pattern the material forming the circuit elements described herein.

[0073] Step S102: Measure the selected area.

[0074] When only the elements within the barrier layer are of interest, it is possible to select to measure only the barrier layer. Otherwise, it is possible to select to also measure one or both of the first and second superconductors. Typically, it may be necessary to focus more on the barrier layer, therefore, the measurement operation is performed at least with respect to the barrier layer.

[0075] To obtain more comprehensive and realistic measurement data, the measurements were performed in multiple regions / at least two regions. Specifically, measurements were performed on at least two regions of the barrier layer. These at least two regions were selected along the length of the previously obtained cross-section. In the thickness direction, given the dimensions of the Josephson junction, the measurements could cover its thickness; simultaneously, the cutting operation had already thinned the junction, so in the width direction, the measurements could cover its width. In other words, the measurements covered both the width and thickness of the junction, while coverage of the length direction could be achieved through multiple measurements. Thus, the data obtained from the measurements could comprehensively reflect the elemental composition of the Josephson junction.

[0076] It is worth noting that in some cases (such as measurement methods based on the special structure, size, or characteristics of the knot), a single measurement operation may not be able to cover any one or more of the thickness, width, and length of the Josephson knot. In such cases, multiple measurements can be performed to cover these areas. Alternatively, if the data of interest does not require coverage of the entire local area (i.e., focusing on a local region), then one or a few regions can be selected for measurement without covering the entire location.

[0077] In this application example, by performing measurements on at least two regions along the length of the barrier layer, at least two sets of measurement data, each corresponding to a specific number of regions, are obtained. These measurement data contain characteristic information about various elements within the corresponding regions. This characteristic information may include, for example, the type of element, such as aluminum or carbon. It may also include the content and quantity of the element. Furthermore, by processing this information or using a measuring device, information such as the element content included in the characteristic information can be obtained. For example, in some examples, the characteristic information includes: the number of atoms of various elements in the corresponding region, or the atomic content of various elements in the corresponding region.

[0078] Depending on the desired accuracy and measurement results (such as efficiency), different equipment can be selected. For example, as mentioned above, TEM (Transmission Electron Microscopy) can be used for measurement. Further, STEM (Scanning Transmission Electron Microscopy) can be chosen. For higher resolution and other requirements, an Aberration-Corrected Transmission Electron Microscope (AC-TEM) or an Aberration-Corrected Scanning Transmission Electron Microscope (AC-STEM) can be used in conjunction with spherical aberration correction techniques.

[0079] The measurement equipment can fulfill various analytical needs depending on the information collected. For example, by collecting information on inelastic scattered electrons generated when an electron beam passes through a sample, an electron energy loss spectrum (EELS) can be obtained; subsequently, information such as the sample's chemical composition, electronic structure, and chemical bonding can be acquired. Alternatively, by collecting characteristic X-rays excited by the interaction between the sample and the electron beam, energy dispersive spectrometer (EDS) analysis can be performed; for example, elemental mapping and semi-quantitative composition information of the sample can be obtained based on the intensity and wavelength distribution of the X-rays. EDS analysis focuses on the analysis of heavier elements, while EELS analysis focuses on the analysis of lighter elements.

[0080] Therefore, in this example, the measurement operation is performed by scanning the Josephson junction from a direction perpendicular to the cross-section using a measurement device (such as AC-STEM). The scanning method may be, for example, line scanning or area scanning. Furthermore, depending on the analysis being performed, the measurement device may be equipped with instruments such as X-ray energy dispersive spectrometer (EDS analysis) or electron energy loss spectrometer (EELS analysis).

[0081] Line scanning refers to the measurement operation being performed within a linear region. This linear region is defined along the thickness direction of the Josephson junction. The measurement operation involves performing a line scan over the linear region of the Josephson junction, where the measured dimension of the linear region in the thickness direction is equal to or greater than the thickness of the barrier layer. See, for example... Figure 4 With thickness ( Figure 4 Taking a barrier layer (where D represents 1nm-2nm, width 100nm, length 200nm) as an example, 10 line scan data points are uniformly distributed within the length range at 20nm intervals (L). A single line scan data point can reflect the content and changes of Al, C, and O elements along that line as they move from the upper aluminum layer through the oxide layer to the lower aluminum layer. Averaging the 10 line scan data points provides a more accurate overall determination of the Al, O, and C element content and changes within the oxide layer.

[0082] Surface scanning refers to the measurement operation performed on a surface region. This surface region is defined along the thickness and length directions of the Josephson junction. The measurement operation involves performing a surface scan of the Josephson junction's surface region, where the measured dimension of the surface region in the thickness direction is equal to or greater than the thickness of the barrier layer, and the measured dimension of the surface region in the length direction is less than the length of the barrier layer. Similarly, consider a barrier layer with a thickness of 1nm-2nm, a width of 100nm, and a length of 200nm. Within the length range, intervals of 20nm are used... Figure 4The L in the figure represents the area scan data, which is uniformly distributed across 10 area scans (each area is a rectangular region of 1 nm x 10 nm). Therefore, averaging the 10 line scan data can more accurately obtain the overall Al, O, and C element content and variations of the oxide layer.

[0083] EELS analysis examines inelastic scattered electrons formed as they pass through a sample; therefore, it requires a certain sample thickness. In this example, this thickness is related to the width dimension of the Josephson junction measured perpendicular to the cross-section. Furthermore, to obtain content reflecting the elemental composition of the Josephson junction as a whole (bulk phase), the width dimension must be less than or equal to a preset value, which depends on the measurement equipment used in the measurement operation (AC-STEM combined with EELS), ensuring that the measurement operation yields measurement data associated with the elements in the Josephson junction bulk phase.

[0084] Step S103: Process the measurement data and obtain the results.

[0085] In step S102, measurements were performed on at least two regions, thus obtaining at least two corresponding measurement data (each measurement yields corresponding measurement data). Therefore, processing these data yields analytical results for various elements within the Josephson knot.

[0086] It is understood that the analytical results are associated with characteristic information in the measurement data. For example, when the characteristic information is the type of element, the analytical results will include the number of types of elements contained in the Josephson junction, as well as their specific names. Or, for example, when the characteristic information is the type and content of elements, the analytical results will include the number of types of elements contained in the Josephson junction, as well as their specific names and contents. Therefore, by way of example, in the step of processing at least two sets of measurement data to obtain analytical results for various elements in the Josephson junction, the analytical results may be, for example, the atomic number content.

[0087] The processing involves at least two measurements to obtain analytical results for various elements in the Josephson junction. This includes, for example, performing multiple single-element content acquisition operations to obtain the content of each element. Each acquisition operation uses a different element; that is, each acquisition operation will obtain the content of an independent element.

[0088] The process of obtaining the content of a single element includes: selecting a single element as the target element, extracting the content of the target element from each measurement data point (a single measurement operation can obtain data related to multiple elements), and calculating the arithmetic mean of the content of the target element in all measurement data. Therefore, this method generally obtains the analytical results of the target element by performing continuous / multiple measurements and then superimposing the data for processing.

[0089] The above method enables elemental analysis of Josephson junctions, allowing for the acquisition of information such as the oxygen content in the barrier layer and variations in oxygen content across different regions. This elemental information can then be used in the fabrication or evaluation of Josephson junctions. Therefore, the Josephson junction testing method described in the example can be used for fabricating or evaluating Josephson junctions. For instance, the Josephson junction testing method is used to analyze the relationship between the junction resistance of the Josephson junction and the elemental content of the barrier layer. Alternatively, when the barrier layer is an oxide layer formed by partially (usually surface-)oxidizing the superconductor layer, the Josephson junction testing method is used to analyze the uniformity of oxidation, such as whether there are unoxidized regions of the superconductor layer along its length. Furthermore, when the barrier layer is an oxide layer formed by partially oxidizing the superconductor layer, the Josephson junction testing method can also be used to analyze the oxide thickness.

[0090] Overall, the example solution can achieve at least the following positive results.

[0091] 1. Using a spherical aberration electron microscope, the potential barrier layer (such as the oxide layer) in a small area can be magnified as much as possible; the test range can include only the oxide layer.

[0092] 2. By employing continuous surface scanning and superposition (such as calculating the arithmetic mean of multiple measurement data), the bulk elemental content of the overall Josephson junction oxide layer can be characterized; the quantitative analysis of Al, C, and O elements is more accurate.

[0093] 3. This scheme will benefit future research into the relationship between junction resistance and elemental content of the oxide layer, in order to control uneven local oxidation and inconsistent oxide layer thickness during junction fabrication.

[0094] The above description, based on the embodiments shown in the drawings, details the structure, features, and effects of this application. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A Josephson node testing method, characterized in that, include: A Josephson junction is provided having a cross-section defined in the thickness direction, wherein the barrier layer of the Josephson junction in the stacked region has a length dimension and a thickness dimension, the length dimension and thickness dimension being defined by the edge of the barrier layer within the cross-section; Measurement operations are performed on at least two regions along the length dimension of the barrier layer to obtain at least two measurement data that correspond one-to-one with the number of regions, and the measurement data contains feature information of various elements in the corresponding regions; The at least two measurement data are processed to obtain analytical results of various elements in the Josephson junction.

2. The Josephson node testing method according to claim 1, characterized in that, Josephson knot testing methods include one or more of the following characteristics; First feature: The feature information includes: the number of atoms of various elements in the corresponding region, or the content of the number of atoms of various elements in the corresponding region; Second feature: In the step of processing the at least two measurement data to obtain the analytical results of various elements in the Josephson junction, the analytical results are the atomic number content; The third feature: processing the at least two measurement data to obtain the analysis results of various elements in the Josephson junction includes: performing single-element content acquisition operations multiple times to obtain the content of various elements, wherein the elements in each acquisition operation are different; The operation of obtaining the content of a single element includes: Select a single element as the target element, extract the content of the target element in each measurement data, and calculate the arithmetic mean of the content of the target element in all measurement data.

3. The Josephson node testing method according to claim 1, characterized in that, The measurement operation was performed by scanning the Josephson node using measuring equipment; The measuring equipment includes aberration scanning transmission electron microscope and X-ray energy dispersive spectrometer, or the measurement includes aberration scanning transmission electron microscope and electron energy loss spectrometer.

4. The Josephson node testing method according to claim 3, characterized in that, Josephson knot testing methods include either the first or second limitation; First limitation: The measurement operation is performed in a linear region, and the linear region is defined along the thickness direction of the Josephson junction. The measurement operation is performed by: performing a line scan on the linear region of the Josephson junction, wherein the measured size of the linear region in the thickness direction is equal to or greater than the thickness size of the barrier layer. Second limitation: The measurement operation is performed in a surface region, which is defined along the thickness and length directions of the Josephson junction. The measurement operation is: performing a surface scan on the surface region of the Josephson junction, wherein the dimension of the surface region measured in the thickness direction is equal to or greater than the thickness dimension of the barrier layer, and the dimension of the surface region measured in the length direction is less than the length dimension of the barrier layer.

5. The Josephson node testing method according to claim 1, characterized in that, Josephson knots have a width dimension measured perpendicular to the cross-section. The width dimension is less than or equal to a preset value, and the preset value depends on the measuring equipment used in the measurement operation, so that the measurement operation obtains measurement data associated with the elements in the Josephson junction bulk phase, and thus in the step of processing the at least two measurement data to obtain the analysis results of various elements in the Josephson junction, the analysis results reflect the content of various elements in the Josephson junction as a whole.

6. The Josephson node testing method according to any one of claims 1 to 5, characterized in that, The cross-section of the Josephson junction is obtained by focused ion beam cutting, and the cutting operation is carried out in a manner that gradually approaches the barrier layer from a position away from the barrier layer along a direction perpendicular to the cross-section. The Josephson junction has an embedded film of superconductor layer embedded in the Josephson junction at a distance from the stacked region. The embedded film is configured to indicate the position to stop cutting during a cutting operation.

7. The application of the Josephson junction testing method according to any one of claims 1 to 6 in the fabrication or evaluation of Josephson junctions, wherein the Josephson junction testing method is used to analyze the relationship between the junction resistance of the Josephson junction and the elemental content of the barrier layer. Alternatively, the barrier layer is an oxide layer formed by partially oxidizing the superconductor layer, and the Josephson junction test method is used to analyze the uniformity of oxidation; Alternatively, the barrier layer is an oxide layer formed by partially oxidizing the superconductor layer, and the Josephson junction test method is used to analyze the oxide thickness.

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