Josephson junction barrier layer thickness monitoring method

Abstract

The invention provides a Josephson junction barrier layer thickness monitoring method comprising the following steps: providing a substrate, forming a Josephson junction on one side of the substrate, the Josephson junction comprising a first superconducting material layer, a barrier layer and a second superconducting material layer which are stacked on the substrate in sequence, carrying out area division on the upper surface of the second superconducting material layer, and forming a Josephson junction barrier layer thickness on the upper surface of the second superconducting material layer; a thickness measurement area is determined, a patterned photoetching layer is formed on the second superconducting material layer, a first opening for exposing the thickness measurement area is formed in the photoetching layer, the second superconducting material layer in the thickness measurement area is etched and thinned based on the photoetching layer, and the thickness of the thinned second superconducting material layer is larger than 0 nm and smaller than 20 nm. And measuring the thickness measurement area by using an ellipsometer to obtain the thickness value of the barrier layer. According to the method for monitoring the thickness of the Josephson junction barrier layer, rapid and nondestructive measurement of the thickness and uniformity of the large-size wafer-level barrier layer is realized by using the ellipsometer, and the requirements of a large-scale high-Jc superconducting integrated circuit can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor integrated circuit manufacturing, and relates to a method for monitoring the thickness of a Josephson junction barrier layer. Background Art

[0002] Devices based on the Josephson effect and their applications have always been a research hotspot in the field of superconducting electronics, including single flux quantum circuits (SFQ), superconducting quantum interference devices (SQUID), superconducting quantum bits (Qubit), programmable Josephson voltage standards (PJVS), etc. The core basic unit of these superconducting devices and circuits is the Josephson junction (JJ). The Josephson junction consists of a sandwich structure formed by two superconductors separated by a very thin insulating layer (a few nanometers). Superconducting devices and circuits based on the Josephson junction mainly utilize the macroscopic quantum effect in the Josephson effect or the quantum control phenomenon of the Josephson junction under an external field, so that they exhibit excellent device performance. For example, the superconducting SFQ circuit has significant advantages of high frequency and low power consumption and is one of the optional solutions for next-generation high-performance computing. The SQUID is the most sensitive flux sensor currently, and can detect changes equivalent to nearly one ten-billionth of the earth's magnetic field.

[0003] One of the main parameter indicators of superconducting devices and circuits based on the Josephson junction is the critical current density (J c ). For different application scenarios, the required range of J c of the Josephson junction is also different. For example, the J c of the junction in the SFQ circuit is several thousand to dozens of thousand A / cm 2 , and the higher the operating frequency of the SFQ, the larger the required J c . The higher the scale of the superconducting circuit, the larger the required J c ; the J c of the junction in the SQUID is several to several hundred A / cm 2 , the J c of the junction in the Qubit is several hundred to several thousand A / cm 2 , and the J c of the junction in the quantum voltage standard is several dozen to several hundred A / cm 2 . It can be seen that realizing the control of the critical current density of the Josephson junction is the key basis for fabricating superconducting devices and circuits.

[0004] The superconducting devices and circuits that were first studied and actually applied on a large scale, the Josephson junction material system mainly based on low-temperature superconductivity. Among them, the Nb / Al-AlO x / Nb Josephson junction has the advantages of long life, high quality, good controllability, etc., and is the most widely used Josephson junction at present. The Nb / Al-AlO x / Nb structure uses an oxidized intermediate metal layer Al to form a very thin AlO x insulating layer as a weak link to connect the upper and lower Nb superconducting electrode layers. The AlO x layer is also called the barrier layer. The thickness of the barrier layer AlO x is generally several nanometers. Its thickness and uniformity are the most important factors determining the J x of the Nb / Al-AlO c / Nb junction, and also directly affect the performance of the final superconducting devices and circuits. On the one hand, the size of the J c of the Josephson junction is controlled by adjusting the thickness of the barrier layer. This requires accurate measurement of the thickness of such a thin barrier layer in the Josephson junction process. While providing feedback to guide the optimization of process parameters, it also realizes the monitoring of process stability. On the other hand, the research and development and preparation of array devices and large-scale integrated circuits require accurate measurement of the thickness uniformity of the barrier layer at the wafer level to evaluate the consistency of the performance of devices and circuits.

[0005] During the wafer processing of Josephson junction superconducting devices and circuits, process control monitor chips (PCM) are usually designed on the wafer to measure process parameters such as lithography accuracy, alignment accuracy, etch step height, and insulating layer film thickness for each batch, in order to verify the reliability, uniformity, and repeatability of the process. However, the superconducting circuit PCM chip does not have the ability to monitor the thickness and uniformity of the barrier layer in its core unit Josephson junction. The main reasons are as follows: (1) The thickness of the Nb superconducting thin film on the intermediate barrier layer is several hundred nanometers thick, and it is difficult for conventional optical film thickness detection methods to penetrate, so it is impossible to effectively measure the thickness of the intermediate barrier layer; (2) The intermediate AlO x barrier layer thin film is only a few nanometers thick. When etching to form a step height, it is extremely easy to over-etch, and it is very difficult to accurately construct the barrier layer step. At the same time, the height measurement error of the step gauge for a few nanometers thick is also relatively large.

[0006] At present, there are mainly two methods for the feedback adjustment of the thickness of the AlO x barrier layer in the Josephson junction preparation process. The first is the direct method, that is, using a transmission electron microscope (TEM) to measure the AlO xThe thickness is directly measured. Usually, a part of the Josephson junction region is intercepted by physical cutting methods such as focused ion beam cutting (FIB), and then the cross-sectional multilayer film structure of the junction region is analyzed by TEM to determine the thickness of the AlO x barrier layer. However, this method requires damaging the sample, and the FIB cross-section sample preparation and TEM observation take a long time and are costly. The second is the indirect method, which does not directly measure the thickness of the AlO x barrier layer. Instead, a relationship curve between the oxidation conditions and the critical current density is first established through multiple experiments. Then, after each chip fabrication, the critical current density of the Josephson junction is measured. Whether the oxidation process is stable is verified according to whether the measurement result of the critical current density meets the expectation. If there is a deviation, the oxidation conditions are adjusted according to the established relationship curve between the oxidation conditions and the critical current density. However, this method conducts current-voltage tests on the Josephson junction in the liquid helium temperature range, which requires consuming expensive liquid helium and is costly. More importantly, for the detection of the thickness uniformity of the barrier layer in wafer-level samples, both of the above two methods require sampling and detecting the wafer samples at different positions. As the wafer size increases, the number of samples taken will be larger, and the detection time and cost will both increase significantly. It can be seen that the existing two methods have extremely low detection efficiency and huge costs for the detection of the thickness uniformity of the barrier layer in wafer-level samples.

[0007] Therefore, how to provide a monitoring method for the thickness of the Josephson junction barrier layer to accurately measure the thickness of the barrier layer and meet the R & D requirements of large-scale high-J c superconducting integrated circuits has become an important problem that needs to be solved urgently by those skilled in the art.

[0008] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solutions of the present application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art just because these solutions are described in the background art part of the present application. Summary of the Invention

[0009] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a monitoring method for the thickness of the Josephson junction barrier layer, which is used to solve the problem that it is difficult to accurately measure the thickness of the barrier layer in the prior art and meet the R & D requirements of large-scale high-J c superconducting integrated circuits.

[0010] To achieve the above purpose and other related purposes, the present invention provides a monitoring method for the thickness of the Josephson junction barrier layer, including the following steps:

[0011] Provide a substrate, and form a Josephson junction on one side of the substrate. The Josephson junction includes a first superconducting material layer, a barrier layer, and a second superconducting material layer stacked in sequence on the substrate;

[0012] Divide the upper surface of the second superconducting material layer into regions to determine a thickness measurement region;

[0013] Form a patterned photolithography layer on the second superconducting material layer, and a first opening exposing the thickness measurement region is formed in the photolithography layer;

[0014] Etch and thin the second superconducting material layer in the thickness measurement region based on the photolithography layer, and the thickness of the thinned second superconducting material layer is greater than 0 nm and less than 20 nm;

[0015] Measure the thickness measurement region with an ellipsometer to obtain the thickness value of the barrier layer.

[0016] Optionally, the thickness range of the first superconducting material layer is 140 nm to 160 nm, the thickness range of the second superconducting material layer is 140 nm to 160 nm, and the thickness range of the barrier layer is 1 nm to 5 nm.

[0017] Optionally, the upper surface of the second superconducting material layer further includes a profilometer measurement region located on one side of the thickness measurement region for measuring the thickness of the thinned first superconducting material layer, and a second opening exposing the profilometer measurement region is further provided in the photolithography layer.

[0018] Optionally, the shape of the thickness measurement region is square, and the shape of the profilometer measurement region is rectangular.

[0019] Optionally, the length of one side of the thickness measurement region ranges from 1 mm to 2 mm.

[0020] Optionally, the length range of the profilometer measurement region is 190 μm to 210 μm, and the width range of the profilometer measurement region is 20 μm to 40 μm.

[0021] Optionally, the material of the first superconducting material layer includes any one of niobium nitride, niobium, and niobium-titanium alloy, and the material of the second superconducting material layer includes any one of niobium nitride, niobium, and niobium-titanium alloy.

[0022] Optionally, the material of the barrier layer includes any one of aluminum oxide, magnesium oxide, aluminum nitride, titanium nitride, and boron nitride.

[0023] Optionally, the method for forming the barrier layer includes any one of an oxidation method and a sputtering method, and the methods for forming the first superconducting material layer and the second superconducting material layer include any one of a physical vapor deposition method and a chemical vapor deposition method.

[0024] Optionally, the number of the thickness measurement regions is multiple, and the multiple thickness measurement regions are arranged at intervals and distributed in a dot matrix structure. After obtaining the thickness value of the barrier layer, a step of drawing a thickness distribution map is further included.

[0025] As described above, the method for monitoring the thickness of the Josephson junction barrier layer of the present invention includes: providing a substrate, forming a Josephson junction on one side of the substrate, the Josephson junction including a first superconducting material layer, a barrier layer, and a second superconducting material layer sequentially stacked on the substrate, dividing the upper surface of the second superconducting material layer to determine a thickness measurement region, forming a patterned photoresist layer on the second superconducting material layer, a first opening exposing the thickness measurement region is opened in the photoresist layer, etching and thinning the second superconducting material layer in the thickness measurement region based on the photoresist layer, the thickness of the thinned second superconducting material layer is greater than 0 nm and less than 20 nm, using an ellipsometer to measure the thickness measurement region to obtain the thickness value of the barrier layer. The method for monitoring the thickness of the Josephson junction barrier layer of the present invention realizes rapid and non-destructive measurement of the thickness and its uniformity of the large-size wafer-level barrier layer by using an ellipsometer during the superconducting device and circuit chip manufacturing process, and can meet the R & D requirements of large-scale high-J c superconducting integrated circuits. Description of the Drawings

[0026] Figure 1 Shown is a process flow chart of the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0027] Figure 2 Shown is a schematic diagram of a structure obtained after forming a Josephson junction on one side of the substrate in the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0028] Figure 3 Shown is a schematic diagram of another structure obtained after forming a Josephson junction on one side of the substrate in the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0029] Figure 4 Shown is a top view of the structure obtained after region division in the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0030] Figure 5 Shown as Figure 4 an enlarged view of region A in

[0031] Figure 6 Shown is a schematic diagram of the structure obtained after forming a patterned photoresist layer in the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0032] Figure 7 Shown is a schematic diagram of the structure obtained after etching and thinning in the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0033] Figure 8 Shown as Figure 7 A schematic structural diagram of the medium thickness measurement area.

[0034] Figure 9 Shown as a schematic diagram of measuring the thickness measurement area with an ellipsometer in the method for monitoring the thickness of the Josephson junction barrier layer of the present invention.

[0035] Description of reference numerals

[0036] 1 Substrate

[0037] 2 Josephson junction

[0038] 21 First superconducting material layer

[0039] 22 Barrier layer

[0040] 23 Second superconducting material layer

[0041] 24 Metal layer

[0042] 3 Thickness measurement area

[0043] 4 Profilometer measurement area

[0044] 5 Photolithography layer

[0045] 6 First opening

[0046] 7 Ellipsometer

[0047] Steps S1 to S5 Detailed implementation manners

[0048] The following describes the implementation manners of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] It should be emphasized that the term "including / containing" when used herein refers to the presence of features, whole things, steps or components, but does not exclude the presence or addition of one or more other features, whole things, steps or components.

[0050] Features described and / or shown for one implementation manner can be used in the same or similar manner in one or more other implementation manners, combined with features in other implementation manners, or replace features in other implementation manners.

[0051] When describing embodiments of the present invention in detail, for ease of explanation, schematic diagrams showing the structure of the device may be enlarged locally in a non-general proportion, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0052] For convenience of description, spatial relationship terms such as "under", "below", "lower than", "beneath", "above", "on" etc. may be used herein to describe the relationship between an element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to encompass other directions of the device in use or operation, in addition to the directions depicted in the drawings. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers.

[0053] In the context of the present application, the structure in which the first feature is "above" the second feature may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0054] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0055] Please refer to Figure 1 , which is shown as a process flow diagram of the method for monitoring the thickness of the Josephson junction barrier layer of the present invention, and includes the following steps:

[0056] S1: Provide a substrate, and form a Josephson junction on one side of the substrate. The Josephson junction includes a first superconducting material layer, a barrier layer, and a second superconducting material layer stacked in sequence on the substrate;

[0057] S2: Divide the upper surface of the second superconducting material layer to determine a thickness measurement area;

[0058] S3: Form a patterned photoresist layer on the second superconducting material layer. A first opening exposing the thickness measurement area is formed in the photoresist layer;

[0059] S4: Etch and thin the second superconducting material layer in the thickness measurement area based on the photoresist layer. The thickness of the thinned second superconducting material layer is greater than 0 nm and less than 20 nm;

[0060] S5: Measure the thickness measurement area using an ellipsometer to obtain the thickness value of the barrier layer.

[0061] Next, in conjunction with Figures 2 to 9 , each step of the method for monitoring the thickness of the Josephson junction barrier layer of the present invention will be described in detail.

[0062] First, please refer to Figure 2 , and perform step S1: Provide a substrate 1, and form a Josephson junction 2 on one side of the substrate 1. The Josephson junction 2 includes a first superconducting material layer 21, a barrier layer 22, and a second superconducting material layer 23 that are sequentially stacked on the substrate 1.

[0063] As an example, the thickness range of the first superconducting material layer 21 is 140 nm to 160 nm, the thickness range of the second superconducting material layer 23 is 140 nm to 160 nm, and the thickness range of the barrier layer 22 is 1 nm to 5 nm. In this embodiment, the thickness of the first superconducting material layer 21 and the second superconducting material layer 23 is 150 nm, and the thickness of the barrier layer 22 is 1.5 nm.

[0064] As an example, the material of the first superconducting material layer 21 includes any one of niobium nitride, niobium, and niobium-titanium alloy, and the material of the second superconducting material layer 23 includes any one of niobium nitride, niobium, and niobium-titanium alloy. In other examples, the materials of the first superconducting material layer 21 and the second superconducting material layer 23 can also use other suitable superconducting materials.

[0065] As an example, the material of the barrier layer 22 includes any one of aluminum oxide, magnesium oxide, aluminum nitride, titanium nitride, and boron nitride. In other examples, the material of the barrier layer 22 can also use other suitable insulating materials.

[0066] As an example, the method for forming the barrier layer 22 includes any one of the oxidation method and the sputtering method, and the methods for forming the first superconducting material layer 21 and the second superconducting material layer 23 include any one of the physical vapor deposition method and the chemical vapor deposition method.

[0067] As an example, please refer to Figure 3 , which shows a schematic diagram of another structure obtained after forming the Josephson junction 2 on one side of the substrate 1. The Josephson junction 2 further includes a metal layer 24. In this embodiment, the structure of the Josephson junction 2 is the Nb / Al-AlO x / Nb structure, where the metal layer 24 is an Al layer, and the barrier layer 22 is an AlO x layer, and the AlO x layer is obtained by oxidizing the Al layer.

[0068] Please refer to FIG. 4 again. Perform step S2: Divide the upper surface of the second superconducting material layer 23 to determine the thickness measurement area 3.

[0069] Specifically, the thickness measurement area 3 is used to receive the incident light of the subsequent ellipsometer 7, and its area is larger than the spot size of the ellipsometer 7, so as to ensure that the incident light of the ellipsometer 7 can fully hit the upper surface of the thickness measurement area 3, and accurately measure the thickness of the barrier layer 22 in the thickness measurement area 3.

[0070] As an example, please refer to Figure 5 , which shows Figure 4 an enlarged view of area A in FIG., the shape of the thickness measurement area 3 is square. In other embodiments, the shape of the thickness measurement area 3 can also be other shapes, such as circular, rectangular or trapezoidal, etc.

[0071] As an example, the side length range of the thickness measurement area 3 is 1 mm to 2 mm. In this embodiment, the side length of the thickness measurement area 3 is 1.5 mm.

[0072] It should be noted that since Figure 6 , Figure 7 and Figure 9 are all structural cross-sectional views, for the convenience of illustration, Figure 6 , Figure 7 and Figure 9 use area I to represent the thickness measurement area 3.

[0073] Please refer to Figure 6 again. Perform step S3: Form a patterned photoresist layer 5 on the second superconducting material layer 23, and a first opening 6 exposing the thickness measurement area 3 is formed in the photoresist layer 5. Among them, the area covered by the photoresist layer 5 is used to form the required Josephson junction 2 device and other subsequent chip manufacturing processes.

[0074] Please refer to Figure 7 again. Perform step S4: Etch and thin the second superconducting material layer 23 in the thickness measurement area 3 based on the photoresist layer 5. The thickness of the thinned second superconducting material layer 23 is greater than 0 nm and less than 20 nm.

[0075] As an example, please refer to Figure 8 , which shows Figure 7 a schematic structural diagram of the thickness measurement area 3 in FIG., where the structure of the Josephson junction 2 is Nb / Al-AlO x / Nb structure, including a substrate, a Nb layer, an Al layer and an AlO x layer. After etching and thinning the top Nb layer, the thickness of the top Nb layer is 10 nm.

[0076] As an example, please refer back to Figure 5 The upper surface of the second superconducting material layer 23 further includes a profilometer measurement area 4 located on one side of the thickness measurement area 3. The profilometer measurement area 4 is used to measure the thickness of the etched first superconducting material layer 21. That is to say, the thickness of the etched and thinned first superconducting material layer 21 can be monitored through the profilometer measurement area 4.

[0077] As an example, a second opening exposing the profilometer measurement area 4 is further provided in the photolithography layer 5, so that the profilometer measurement area 4 can monitor the thickness change of the first superconducting material layer 21.

[0078] As an example, the shape of the profilometer measurement area 4 is rectangular. Among them, the length range of the profilometer measurement area 4 is 190 μm to 210 μm, and the width range of the profilometer measurement area 4 is 20 μm to 40 μm. In this embodiment, the length of the profilometer measurement area 4 is 200 μm, and the width of the profilometer measurement area 4 is 30 μm.

[0079] Please refer back to Figure 9 and perform step S5: Measure the thickness measurement area 3 with an ellipsometer to obtain the thickness value of the barrier layer 22.

[0080] Specifically, since the thickness of the first superconducting material layer 21 in the thickness measurement area 3 is very thin, the incident light of the ellipsometer can penetrate the first superconducting material layer 21 and enter the barrier layer 22. Then, by using the known incident light wavelength, incident angle, and the optical constants of the barrier layer 22, and utilizing the Fresnel equation and related models, the thickness of the barrier layer 22 is calculated, thereby obtaining the thickness value of the barrier layer 22. And the second superconducting material layer 23 is relatively thick and the incident light of the ellipsometer cannot penetrate it. When measuring the thickness, the second superconducting material layer 23 and the substrate 1 are treated as an infinitely thick substrate 1.

[0081] As an example, as Figure 4 shown, the number of the thickness measurement areas 3 is multiple, and the multiple thickness measurement areas 3 are arranged at intervals and distributed in a dot matrix structure. After obtaining the thickness value of the barrier layer 22, it further includes the step of drawing a thickness distribution map.

[0082] Specifically, the device is usually fabricated by performing a wafer run on an entire wafer. A wafer can simultaneously fabricate many chips with the same structure. Figure 4 The small squares in Figure 4The thickness measurement areas 3 described above are arranged at intervals and distributed in a dot matrix structure. In this embodiment, the size of the wafer is 4 inches. In other embodiments, the size of the wafer can also be 6 inches, 8 inches, and 12 inches. Finally, through the drawn thickness distribution map, the uniformity of the thickness of the barrier layer 22 within the wafer can be measured.

[0083] It should be noted that during the wafer fabrication process, an ellipsometer is used to measure the thickness of the barrier layer at the large-size wafer level. It can perform non-destructive, large-range, multi-point distributed, and rapid measurements on samples, and can master the preparation and precise control of the barrier layers of Josephson junctions with different J c superconducting integrated circuits, laying a technical foundation for the subsequent large-scale high-J c superconducting integrated circuit R & D, thus promoting the rapid transition of superconducting integrated circuits from the R & D stage of 4-inch wafers to the productization stage of 12-inch wafers, and expanding the application scope of superconducting integrated circuits and superconducting devices.

[0084] In summary, the method for monitoring the thickness of the barrier layer of the Josephson junction of the present invention includes: providing a substrate, forming a Josephson junction on one side of the substrate, the Josephson junction including a first superconducting material layer, a barrier layer, and a second superconducting material layer stacked in sequence on the substrate, dividing the upper surface of the second superconducting material layer to determine the thickness measurement area, forming a patterned photolithography layer on the second superconducting material layer, a first opening exposing the thickness measurement area is opened in the photolithography layer, etching and thinning the second superconducting material layer in the thickness measurement area based on the photolithography layer, the thickness of the thinned second superconducting material layer is greater than 0 nm and less than 20 nm, using an ellipsometer to measure the thickness measurement area to obtain the thickness value of the barrier layer. The method for monitoring the thickness of the barrier layer of the Josephson junction of the present invention uses an ellipsometer to achieve rapid and non-destructive measurement of the thickness and its uniformity of the barrier layer at the large-size wafer level during the wafer fabrication process of superconducting devices and circuits, and can meet the R & D requirements of large-scale high-J c superconducting integrated circuits. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0085] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for monitoring the thickness of a Josephson junction barrier layer, characterized in that, The method includes the following steps: Provide a substrate, and form a Josephson junction on one surface of the substrate. The Josephson junction includes a first superconducting material layer, a barrier layer, and a second superconducting material layer that are sequentially stacked on the substrate. Divide the upper surface of the second superconducting material layer to determine a thickness measurement area. Form a patterned photolithography layer on the second superconducting material layer. A first opening exposing the thickness measurement area is formed in the photolithography layer. Etch and thin the second superconducting material layer in the thickness measurement area based on the photolithography layer. The thickness of the thinned second superconducting material layer is greater than 0 nm and less than 20 nm. Measure the thickness measurement area using an ellipsometer to obtain the thickness value of the barrier layer.

2. The monitoring method for the thickness of the Josephson junction barrier layer according to claim 1, characterized in that: The thickness range of the first superconducting material layer is 140 nm to 160 nm, the thickness range of the second superconducting material layer is 140 nm to 160 nm, and the thickness range of the barrier layer is 1 nm to 5 nm.

3. The monitoring method for the thickness of the Josephson junction barrier layer according to claim 1, characterized in that: The upper surface of the second superconducting material layer further includes a profilometer measurement area located on one side of the thickness measurement area for measuring the thickness of the thinned first superconducting material layer. A second opening exposing the profilometer measurement area is also formed in the photolithography layer.

4. The method for monitoring the thickness of the Josephson junction barrier layer according to claim 3, characterized in that: The shape of the thickness measurement area is square, and the shape of the profilometer measurement area is rectangular.

5. The monitoring method of the Josephson junction barrier layer thickness according to claim 4, characterized in that: The unilateral length range of the thickness measurement area is 1 mm to 2 mm.

6. The monitoring method of the thickness of the Josephson junction barrier layer according to claim 3, characterized in that: The length range of the profilometer measurement area is 190 μm to 210 μm, and the width range of the profilometer measurement area is 20 μm to 40 μm.

7. The method for monitoring the thickness of the Josephson junction barrier layer according to claim 1, wherein: The material of the first superconducting material layer includes any one of niobium nitride, niobium, and niobium-titanium alloy. The material of the second superconducting material layer includes any one of niobium nitride, niobium, and niobium-titanium alloy.

8. The method for monitoring the thickness of the Josephson junction barrier layer according to claim 1, characterized in that: The material of the barrier layer includes any one of aluminum oxide, magnesium oxide, aluminum nitride, titanium nitride, and boron nitride.

9. The method for monitoring the thickness of the Josephson junction barrier layer according to claim 1, characterized in that: The method for forming the barrier layer includes any one of an oxidation method and a sputtering method. The method for forming the first superconducting material layer and the second superconducting material layer includes any one of a physical vapor deposition method and a chemical vapor deposition method.

10. The monitoring method for the thickness of the Josephson junction barrier layer according to claim 1, characterized in that: The number of the thickness measurement areas is multiple. The multiple thickness measurement areas are spaced apart and distributed in a dot matrix structure. After obtaining the thickness value of the barrier layer, the step of drawing a thickness distribution map is further included.

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