Josephson junction and preparation method thereof

Abstract

The invention provides a Josephson junction and a preparation method thereof. The preparation method comprises the steps that an SOI mask and a substrate are provided, the SOI mask is provided with a first etching window and a second etching window which penetrate through the SOI mask, and the first etching window and the second etching window are provided with at least one intersecting area; fixing the SOI mask on the substrate; forming a first superconducting layer on the substrate exposed from the first etching window; forming an aluminum oxide barrier layer on the first superconducting layer; and forming a second superconducting layer on the substrate exposed out of the second etching window so as to obtain a Josephson junction in the intersection area. According to the method, the SOI mask is used for replacing photoresist, so that the adverse effect of the residual photoresist on the performance of the Josephson junction and the risk that the photoresist is softened or degraded when the deposition process of the superconductor needing to be heated is carried out are avoided.

Description

Technical Field

[0001] The present application relates to the field of quantum chip technology, and in particular to a Josephson junction and a preparation method thereof. Background Art

[0002] As a key device of superconducting quantum circuit, the structure of Josephson junction is generally composed of two superconductors sandwiched by a very thin barrier layer (thickness ≤ the coherence length of Cooper electron pairs), such as S (superconductor)-I (semiconductor or insulator)-S (superconductor) structure, referred to as SIS. Superconducting electrons in the Josephson junction can pass through the semiconductor or insulator film from one side to the other side through the tunnel effect. In the prior art, photoresist is usually used when preparing the Josephson junction, for example, the following preparation method is adopted: photoresist is coated on the substrate, a pattern window is formed after exposure and development, and the Josephson junction is prepared on the exposed area of ​​the pattern window on the substrate. However, the residual photoresist will have an adverse effect on the performance of the Josephson junction. At the same time, when the superconductor deposition process that requires heating is carried out, the photoresist has the risk of softening or degradation. Summary of the invention

[0003] The purpose of this application is to provide a Josephson junction and a method for preparing the same, so as to avoid the adverse effects of residual photoresist on the performance of the Josephson junction and the risk of softening or degradation of the photoresist during the superconductor deposition process requiring heating. The specific technical solution is as follows:

[0004] A first aspect of the present application provides a method for preparing a Josephson junction, characterized by comprising:

[0005] Providing an SOI mask and a substrate, wherein the SOI mask has a first etching window and a second etching window penetrating the SOI mask, and the first etching window and the second etching window have at least one intersection area;

[0006] Fixing the SOI mask on the substrate;

[0007] forming a first superconducting layer on the substrate exposed by the first etching window;

[0008] forming an aluminum oxide barrier layer on the first superconducting layer;

[0009] A second superconducting layer is formed on the substrate exposed by the second etching window to obtain a Josephson junction in the intersection area.

[0010] In some embodiments of the present application, providing the SOI mask includes:

[0011] Providing an SOI wafer, the SOI wafer comprising a first silicon layer, a silicon dioxide layer, and a second silicon layer stacked in sequence;

[0012] Patterning and etching the first silicon layer to form the first etching window and the second etching window;

[0013] The second silicon layer and the silicon dioxide layer are pattern-etched to form a cavity exposing the first etching window and the second etching window, thereby obtaining the SOI mask.

[0014] In some embodiments of the present application, the aluminum oxide barrier layer is a single crystal aluminum oxide barrier layer.

[0015] In some embodiments of the present application, the material of the first superconducting layer is selected from aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: placing the substrate in a closed environment, heating the closed environment to a high temperature, introducing oxygen at a high temperature to oxidize the surface of the first superconducting layer to form a single crystal aluminum oxide barrier layer.

[0016] In some embodiments of the present application, the material of the first superconducting layer is selected from any one of superconducting metals except aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: after depositing an aluminum layer on the first superconducting layer, placing the substrate in a closed environment, heating the closed environment to a high temperature, and introducing oxygen under high temperature to oxidize the aluminum layer to form a single crystal aluminum oxide barrier layer.

[0017] In some embodiments of the present application, the temperature of the closed environment is raised to 280°C to 500°C.

[0018] In some embodiments of the present application, the material of the first superconducting layer is selected from any one of superconducting metals except aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: after depositing an aluminum layer on the first superconducting layer, placing the substrate in a closed environment, oxidizing the deposited aluminum layer at room temperature in the closed environment to form an amorphous aluminum oxide barrier layer, and converting the amorphous aluminum oxide barrier layer into a single crystal aluminum oxide barrier layer by high temperature annealing.

[0019] In some embodiments of the present application, the temperature of the high temperature annealing treatment is 800°C to 2000°C.

[0020] In some embodiments of the present application, the material of the first superconducting layer is selected from any one of superconducting metals except aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: heating the substrate to a high temperature, depositing aluminum on the first superconducting layer under a high temperature state and simultaneously introducing oxygen to form a single crystal aluminum oxide barrier layer.

[0021] In some embodiments of the present application, the substrate is heated to 700° C. to 800° C., and the rate of depositing aluminum is to

[0022] In some embodiments of the present application, the first etching window and the second etching window are perpendicular to each other, the first superconducting layer and the second superconducting layer are formed by an oblique evaporation deposition process, and the evaporation directions are perpendicular to each other.

[0023] In some embodiments of the present application, the preparation method further includes: separating the SOI mask and the substrate.

[0024] A second aspect of the present application provides a Josephson junction obtained according to any of the preparation methods described above.

[0025] Beneficial effects of this application:

[0026] The present application provides a Josephson junction and a preparation method thereof. The preparation method uses an SOI mask instead of a photoresist, which can avoid the adverse effects of the residual photoresist on the performance of the Josephson junction. Since the photoresist is not resistant to high temperatures, the preparation method of the present application also avoids the risk of softening or degrading the photoresist at high temperatures when performing a superconductor deposition process that requires heating, and expands the range of choices for superconductor deposition methods during the preparation process, for example, magnetron sputtering, chemical vapor deposition, and other superconductor deposition methods that require heating can be selected.

[0027] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0029] Figure 1 A schematic diagram of a process for preparing a Josephson junction provided in this application;

[0030] Figure 2 Schematic diagram of the structure of the SOI mask provided in this application before and after patterning;

[0031] Figure 3 A schematic diagram of the process steps of an embodiment of the present application;

[0032] Figure 4 A schematic diagram of the process steps of another embodiment of the present application;

[0033] Figure 5 This is a schematic diagram of the process steps of another embodiment of the present application;

[0034] Reference numerals: 100: SOI mask; 110: first silicon layer; 111: first etching window; 112: second etching window; 120: silicon dioxide layer; 130: second silicon layer; 20: substrate; 30: first superconducting layer; 40: aluminum oxide barrier layer; 50: second superconducting layer. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0036] In the description of the present application, it should be understood that the terms "center", "up", "down", "left", "right", etc., indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0038] In the prior art, photoresist is usually used when preparing Josephson junctions. The use of photoresist usually has the following problems: first, the area where the Josephson junction contacts the substrate is prone to photoresist residue. Even if the photoresist can be dissolved by the photoresist washing process, it is impossible to completely remove it. The residual photoresist will have an adverse effect on the performance of the Josephson junction; second, photoresist is not resistant to high temperatures and has the risk of softening or degradation at high temperatures. It is not suitable for thin film deposition methods that require heating when depositing superconducting layers, such as magnetron sputtering, chemical vapor deposition, etc.

[0039] In addition, in the prior art, when preparing the aluminum oxide barrier layer, the amorphous aluminum oxide barrier layer is obtained by oxidizing Al (111) at room temperature. The single crystal aluminum oxide barrier layer has smaller defects and less loss than the amorphous aluminum oxide barrier layer, so the low temperature performance of the Josephson junction of the single crystal aluminum oxide barrier layer is better. However, the preparation of the single crystal aluminum oxide barrier layer or the conversion of the amorphous aluminum oxide barrier layer into the single crystal aluminum oxide barrier layer requires a relatively high temperature, and the photoresist will soften or degrade when the temperature exceeds the use temperature of the photoresist. Therefore, the preparation method using the photoresist cannot obtain a Josephson junction with a single crystal aluminum oxide barrier layer.

[0040] SOI technology, i.e. silicon on insulating substrate, introduces a buried oxide layer between the top silicon and the back substrate. The present application uses an SOI mask instead of a photoresist to prepare a Josephson junction, thereby avoiding the adverse effects of the residual photoresist on the performance of the Josephson junction, and also avoiding the risk of softening or degradation of the photoresist during the superconductor deposition process that requires heating. At the same time, the preparation method of the present application can obtain a single crystal aluminum oxide barrier layer to reduce the loss of the Josephson junction at low temperatures, so that the prepared Josephson junction has better low-temperature performance.

[0041] refer to Figure 1 The first aspect of the present application provides a method for preparing a Josephson junction, characterized in that it comprises:

[0042] S1: providing an SOI mask 100 and a substrate 20, wherein the SOI mask 100 has a first etching window 111 and a second etching window 112 penetrating the SOI mask 100, and the first etching window 111 and the second etching window 112 have at least one intersection region;

[0043] S2: Fixing the SOI mask 100 on the substrate 20;

[0044] S3: forming a first superconducting layer 30 on the substrate 20 exposed by the first etching window 111;

[0045] S4: forming an aluminum oxide barrier layer 40 on the first superconducting layer 30;

[0046] S5: forming a second superconducting layer 50 on the substrate 20 exposed by the second etching window 112 to obtain a Josephson junction at the intersection region.

[0047] refer to Figure 2 In some embodiments of the present application, providing the SOI mask 100 in step S1 includes:

[0048] Provide an SOI wafer, the SOI wafer comprising a first silicon layer 110, a silicon dioxide layer 120 and a second silicon layer 130 stacked in sequence (refer to Figure 2 (a));

[0049] Patterning and etching the first silicon layer 110 to form a first etching window 111 and a second etching window 112;

[0050] The second silicon layer 130 and the silicon dioxide layer 120 are patterned and etched to form a cavity exposing the first etching window 111 and the second etching window 112, thereby obtaining the SOI mask 100 (refer to Figure 2 (b)).

[0051] For example, the SOI mask 100 can be specifically prepared by the following method: providing an SOI wafer, applying a photoresist on the surface of the first silicon layer 110 of the SOI wafer, exposing the first etching window 111 and the second etching window 112; etching the first silicon layer 110 to the silicon dioxide layer 120, stripping and removing the photoresist, and obtaining the first etching window 111 and the second etching window 112; depositing 2 μm SiO2 and 9 μm Si3N on the surface of the second silicon layer 130 of the SOI wafer. 4; apply photoresist on the surface of the second silicon layer 130 of the SOI wafer to expose the back cavity pattern; etch 2μmSiO2 and 9μmSi3N4 to transfer the back cavity pattern to the SiO2 and Si3N4 layers; deep silicon etch the second silicon layer 130 to the silicon dioxide layer 120; strip off the photoresist, wet remove SiO2, Si3N4 and the silicon dioxide layer 120 to form a cavity exposing the first etching window 111 and the second etching window 112, and obtain the SOI mask 100.

[0052] The present application has no particular restrictions on the thickness of the first silicon layer 110, the silicon dioxide layer 120, and the second silicon layer 130 in the SOI wafer, as long as the purpose of the present application can be achieved. For example, the thickness of the first silicon layer 110 can be 0.1 to 100 μm, the thickness of the silicon dioxide layer 120 can be 0.4 to 4 μm, and the thickness of the second silicon layer 130 can be 300 to 725 μm.

[0053] In some embodiments of the present application, the first etching window 111 and the second etching window 112 in the SOI mask 100 provided in step S1 have at least one intersection area. For example, the number of intersection areas can be 1, 2 or 3. Specifically, there can be one or more first etching windows 111, and there can be one or more second etching windows 112. At least one Josephson junction, such as a single-junction Josephson junction or a double-junction Josephson junction, can be obtained in a single preparation process. The present application has no particular restrictions on the shape of the intersection area, as long as the purpose of the present application can be achieved. For example, the first etching window 111 and the second etching window 112 can be in the shape of long strips, with equal widths and intersecting vertically, so that the shape of the intersection area is a square.

[0054] In some embodiments of the present application, the surface of the first silicon layer 110 of the SOI mask 100 is bonded to the substrate 20 in step S2. The present application has no particular restrictions on the manner in which the SOI mask 100 is fixed to the substrate 20 in step S2, as long as the purpose of the present application can be achieved. For example, the following manner may be adopted: placing the SOI mask 100 and the substrate 20 in two upper and lower clamps; observing under a microscope to align the surface of the first silicon layer 110 of the SOI mask 100 with the substrate 20; and fixing the clamps with screws to further fix the SOI mask 100 and the substrate 20.

[0055] The present application has no particular restrictions on the type of substrate 20, as long as the purpose of the present application can be achieved. The substrate 20 generally includes a substrate, and the present application has no particular restrictions on the type of substrate, as long as the purpose of the present application can be achieved. For example, the substrate can be selected from any one of a silicon substrate, a sapphire substrate, and a silicon carbide substrate.

[0056] In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from aluminum. In other embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from any superconducting metal other than aluminum, for example, it may include but is not limited to any one of niobium, tantalum, rhenium, titanium nitride or niobium titanium nitrogen. The present application has no particular restrictions on the thin film deposition method for forming the first superconducting layer 30, as long as the purpose of the present application can be achieved. For example, the above-mentioned thin film deposition method may include but is not limited to any one of electron beam evaporation, magnetron sputtering, thermal evaporation or atomic layer vapor deposition. The present application has no particular restrictions on the thickness of the first superconducting layer 30, as long as the purpose of the present application can be achieved.

[0057] In some embodiments of the present application, the formation of the aluminum oxide barrier layer 40 in step S4 includes forming a single crystal aluminum oxide barrier layer, or forming an amorphous aluminum oxide barrier layer. In some embodiments of the present application, the formation of the aluminum oxide barrier layer 40 requires the deposition of an aluminum layer first. The present application has no particular restrictions on the above-mentioned method of depositing the aluminum layer, as long as the purpose of the present application can be achieved, for example, it may include but is not limited to any one of electron beam evaporation, magnetron sputtering, thermal evaporation or atomic layer vapor deposition. The present application has no particular restrictions on the thickness of the aluminum oxide barrier layer 40, as long as the purpose of the present application can be achieved.

[0058] In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from aluminum, and forming an aluminum oxide barrier layer 40 on the first superconducting layer 30 in step S4 includes: placing the substrate 20 in a closed environment, introducing oxygen into the closed environment, and oxidizing the surface of the first superconducting layer 30 at room temperature to form an amorphous aluminum oxide barrier layer 40.

[0059] refer to Figure 3In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from aluminum, and forming an aluminum oxide barrier layer on the first superconducting layer 30 in step S4 includes: placing the substrate 20 in a closed environment, heating the closed environment to a high temperature, introducing oxygen at a high temperature to oxidize the surface of the first superconducting layer 30, and forming a single crystal aluminum oxide barrier layer 40. In some embodiments of the present application, the closed environment is heated to 280°C to 500°C. The melting point of aluminum is 660°C. When the temperature exceeds 277°C (550K), Al(111) can be oxidized to form single crystal aluminum oxide.

[0060] In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from any one of superconducting metals other than aluminum, and forming the aluminum oxide barrier layer 40 on the first superconducting layer 30 in step S4 includes: after depositing the aluminum layer on the first superconducting layer 30, placing the substrate 20 in a closed environment, heating the closed environment to a high temperature, and introducing oxygen at a high temperature to oxidize the aluminum layer to form a single-crystalline aluminum oxide barrier layer 40. In some embodiments of the present application, the closed environment is heated to 280°C to 500°C. The melting point of aluminum is 660°C. When the temperature exceeds 277°C (550K), Al(111) can be oxidized to form single-crystalline aluminum oxide.

[0061] In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from any one of superconducting metals other than aluminum, and forming an aluminum oxide barrier layer on the first superconducting layer 30 in step S4 includes: after depositing an aluminum layer on the first superconducting layer 30, placing the substrate 20 in a closed environment, and oxidizing the deposited aluminum layer at room temperature in the closed environment to form an amorphous aluminum oxide barrier layer 40. The room temperature oxidation may be performed by introducing oxygen into the closed environment.

[0062] refer to Figure 4 In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from any one of superconducting metals other than aluminum, and the formation of the aluminum oxide barrier layer 40 on the first superconducting layer 30 in step S4 includes: after depositing an aluminum layer on the first superconducting layer 30, placing the substrate 20 in a closed environment, and oxidizing the deposited aluminum layer at room temperature in the closed environment to form an amorphous aluminum oxide barrier layer. The room temperature oxidation method can be to introduce oxygen into the closed environment. The amorphous aluminum oxide barrier layer is converted into a single crystal aluminum oxide barrier layer 40 by high temperature annealing. In some embodiments of the present application, the temperature of the high temperature annealing treatment is 800°C to 2000°C. Since high temperature annealing treatment is required, the melting point of the material of the first superconducting layer needs to be higher than the annealing temperature at this time.

[0063] In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from any superconducting metal other than aluminum, and the aluminum oxide barrier layer 40 is formed on the first superconducting layer 30 in step S4, including: setting the temperature of the substrate 20 to room temperature, depositing aluminum on the first superconducting layer 30 and introducing oxygen at the same time, to form an amorphous aluminum oxide barrier layer 40. In some embodiments of the present application, the speed of depositing aluminum is to

[0064] refer to Figure 5 In some embodiments of the present application, the material of the first superconducting layer 30 in step S3 is selected from any superconducting metal other than aluminum, and the aluminum oxide barrier layer 40 is formed on the first superconducting layer 30 in step S4, including: heating the substrate 20 to a high temperature, depositing aluminum on the first superconducting layer 30 at a high temperature and introducing oxygen at the same time, to form a single crystal aluminum oxide barrier layer 40. In some embodiments of the present application, the substrate 20 is heated to 700°C to 800°C, and the aluminum deposition rate is to

[0065] In some embodiments of the present application, a Josephson junction is obtained in the intersection area in step S5. Specifically, the first superconducting layer 30 and the aluminum oxide barrier layer 40 are formed at the position exposed by the first etching window 111 on the substrate 20, and the second superconducting layer 50 is formed at the position exposed by the second etching window 112 on the substrate 20. At the position where the intersection area of ​​the first etching window 111 and the second etching window 112 on the substrate 20 is exposed, the structure is the first superconducting layer / aluminum oxide barrier layer / second superconducting layer, that is, a Josephson junction is obtained. The number of intersection areas of the first etching window 111 and the second etching window 112 is the number of Josephson junctions. The present application has no particular restrictions on the material of the second superconducting layer 50 in step S5, as long as the purpose of the present application can be achieved. For example, the material of the second superconducting layer 50 may include but is not limited to any one of aluminum, niobium, tantalum, rhenium, titanium nitride or niobium titanium nitrogen. The present application has no particular restrictions on the thin film deposition method for forming the second superconducting layer 50, as long as the purpose of the present application can be achieved. For example, the above-mentioned thin film deposition method may include but is not limited to any one of electron beam evaporation, magnetron sputtering, thermal evaporation or atomic layer vapor deposition. The present application has no particular restrictions on the thickness of the second superconducting layer 50, as long as the purpose of the present application can be achieved.

[0066] In some embodiments of the present application, the first etching window 111 and the second etching window 112 are perpendicular to each other, the first superconducting layer 30 and the second superconducting layer 50 are formed by an oblique evaporation deposition process, and the evaporation directions are perpendicular to each other to avoid the material of the first superconducting layer 30 from being deposited on the substrate 20 exposed in the second etching window 112.

[0067] In some embodiments of the present application, the preparation method further comprises step S6: separating the SOI mask 100 and the substrate 20. The present application has no particular limitation on the method of separating the SOI mask 100 and the substrate 20 in step S6, as long as the purpose of the present application can be achieved.

[0068] The second aspect of the present application provides a Josephson junction obtained by the preparation method described in any of the above items. The Josephson junction provided by the present application can avoid the adverse effects of the residual photoresist on the performance of the Josephson junction, and can also avoid the risk of softening or degradation of the photoresist during the superconductor deposition process that requires heating. At the same time, the Josephson junction using a single crystal aluminum oxide barrier layer has better low temperature performance.

[0069] Example

[0070] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0071] Example 1

[0072] refer to Figure 3 Embodiment 1 of the present application provides a method for preparing a Josephson junction, the structure of which is aluminum / single crystal aluminum oxide / aluminum, and the preparation method comprises the following steps:

[0073] S11: providing an SOI mask and a substrate, wherein the SOI mask has a first etching window and a second etching window penetrating the SOI mask, the first etching window and the second etching window have two intersecting areas, and the first etching window and the second etching window are perpendicular to each other;

[0074] S21: Reference Figure 3 (a), fixing the SOI mask on the substrate;

[0075] S31: Reference Figure 3 (b) depositing 30-50 nm of aluminum by oblique evaporation in an electron beam evaporation chamber to form a first superconducting layer on the substrate exposed in the first etched window, wherein the aluminum deposition method may also be magnetron sputtering, thermal evaporation, or the like;

[0076] S41: Reference Figure 3 (c) transferring the substrate and SOI mask obtained in step S31 to an oxidation chamber, heating the oxidation chamber to 280-500° C. and introducing oxygen to oxidize the surface of the first superconducting layer, thereby forming a 1-3 nm single crystal aluminum oxide barrier layer on the first superconducting layer;

[0077] S51: Reference Figure 3(d) transferring the substrate and SOI mask obtained in S41 back to the electron beam evaporation chamber, and depositing 60-100 nm of aluminum by oblique evaporation, wherein the direction of the oblique evaporation deposition is perpendicular to that in S31, so that a second superconducting layer is formed on the substrate exposed in the second etching window, and a Josephson junction is obtained in the intersection area, wherein the above-mentioned aluminum deposition method can also be selected from magnetron sputtering, thermal evaporation, etc.;

[0078] S61: Reference Figure 3 (e) Take out the substrate and SOI mask obtained in S51 from the electron beam evaporation chamber, and separate the SOI mask and substrate.

[0079] Example 2

[0080] refer to Figure 4 Embodiment 2 of the present application provides a method for preparing a Josephson junction, the structure of which is rhenium / single crystal alumina / aluminum, and the preparation method comprises the following steps:

[0081] S12: providing an SOI mask and a substrate, wherein the SOI mask has a first etching window and a second etching window penetrating the SOI mask, the first etching window and the second etching window have two intersecting areas, and the first etching window and the second etching window are perpendicular to each other;

[0082] S22: Reference Figure 4 (a), fixing the SOI mask on the substrate;

[0083] S32: Reference Figure 4 (b) obliquely evaporating and depositing 30 to 50 nm of rhenium in an electron beam evaporation chamber to form a first superconducting layer on the substrate exposed in the first etched window, wherein the above-mentioned rhenium deposition method can also be selected from magnetron sputtering, thermal evaporation and other methods;

[0084] S42: Reference Figure 4 (c) 0.2 nm of aluminum is deposited on the first superconducting layer by oblique evaporation and transferred to the oxidation chamber. Figure 4 (d) introducing oxygen into the oxidation chamber at room temperature to oxidize the deposited aluminum to form amorphous aluminum oxide. The oxidation chamber is heated up and annealed at a temperature of 800 to 2000° C. to transform the amorphous aluminum oxide into a single crystal aluminum oxide barrier layer, wherein the above-mentioned aluminum deposition method can also be selected from atomic layer vapor deposition, magnetron sputtering and other methods;

[0085] S52: Reference Figure 4 (e) The substrate and SOI mask obtained in S42 are transferred back to the electron beam evaporation chamber, and 60 to 100 nm of aluminum are deposited by oblique evaporation. The direction of the oblique evaporation deposition is perpendicular to that in S32, so that a second superconducting layer is formed on the substrate exposed in the second etching window, and a Josephson junction is obtained in the intersection area. The above-mentioned aluminum deposition method can also be selected from magnetron sputtering, thermal evaporation and other methods;

[0086] S62: Reference Figure 4 (f) Take out the substrate and SOI mask obtained in S52 from the electron beam evaporation chamber, and separate the SOI mask and substrate.

[0087] Example 3

[0088] refer to Figure 5 Embodiment 3 of the present application provides a method for preparing a Josephson junction, the structure of which is niobium / single crystal aluminum oxide / aluminum, and the preparation method comprises the following steps:

[0089] S13: providing an SOI mask and a substrate, wherein the SOI mask has a first etching window and a second etching window penetrating the SOI mask, the first etching window and the second etching window have two intersecting areas, and the first etching window and the second etching window are perpendicular to each other;

[0090] S23: Reference Figure 5 (a), fixing the SOI mask on the substrate;

[0091] S33: Reference Figure 5 (b) depositing 30-50 nm of niobium by oblique evaporation in an electron beam evaporation chamber to form a first superconducting layer on the substrate exposed in the first etched window, wherein the above-mentioned method of depositing niobium may also be selected from magnetron sputtering, thermal evaporation, etc.;

[0092] S43: Reference Figure 5 (c) The substrate temperature was heated to 750 °C and the intrinsic vacuum was set to 5 × 10 -6 torr, 0.1-1 nm aluminum is deposited on the first superconducting layer at a speed of 1000 nm, and oxygen is introduced at the same time to form a single crystal aluminum oxide barrier layer. The introduction of oxygen is stopped after the temperature drops.

[0093] S53: Reference Figure 5 (d) oblique evaporation deposition of 60-100 nm aluminum, the direction of the oblique evaporation deposition being perpendicular to that in S33, so that a second superconducting layer is formed on the substrate exposed in the second etched window, and a Josephson junction is obtained in the intersection area, wherein the above-mentioned aluminum deposition method can also be selected from magnetron sputtering, thermal evaporation and the like;

[0094] S63: Reference Figure 5 (e) Take out the substrate and SOI mask obtained in S53 from the electron beam evaporation chamber, and separate the SOI mask and substrate.

[0095] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a Josephson junction, characterized in that: include: Providing an SOI mask and a substrate, wherein the SOI mask has a first etching window and a second etching window penetrating the SOI mask, and the first etching window and the second etching window have at least one intersection area; Fixing the SOI mask on the substrate; forming a first superconducting layer on the substrate exposed by the first etching window; forming an aluminum oxide barrier layer on the first superconducting layer; A second superconducting layer is formed on the substrate exposed by the second etching window to obtain a Josephson junction in the intersection area.

2. The preparation method according to claim 1, characterized in that: Providing the SOI mask comprises: Providing an SOI wafer, the SOI wafer comprising a first silicon layer, a silicon dioxide layer, and a second silicon layer stacked in sequence; Patterning and etching the first silicon layer to form the first etching window and the second etching window; The second silicon layer and the silicon dioxide layer are pattern-etched to form a cavity exposing the first etching window and the second etching window, thereby obtaining the SOI mask.

3. The preparation method according to claim 1, characterized in that: The aluminum oxide barrier layer is a single crystal aluminum oxide barrier layer.

4. The preparation method according to claim 3, characterized in that: The material of the first superconducting layer is selected from aluminum, and forming an aluminum oxide barrier layer on the first superconducting layer includes: placing the substrate in a closed environment, heating the closed environment to a high temperature, and introducing oxygen at a high temperature to oxidize the surface of the first superconducting layer to form a single crystal aluminum oxide barrier layer.

5. The preparation method according to claim 3, characterized in that: The material of the first superconducting layer is selected from any one of superconducting metals except aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: after depositing an aluminum layer on the first superconducting layer, placing the substrate in a closed environment, heating the closed environment to a high temperature, and introducing oxygen at a high temperature to oxidize the aluminum layer to form a single crystal aluminum oxide barrier layer.

6. The preparation method according to claim 4 or 5, characterized in that: The temperature of the sealed environment is raised to 280°C to 500°C.

7. The preparation method according to claim 3, characterized in that: The material of the first superconducting layer is selected from any one of superconducting metals except aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: after depositing an aluminum layer on the first superconducting layer, placing the substrate in a closed environment, oxidizing the deposited aluminum layer at room temperature in the closed environment to form an amorphous aluminum oxide barrier layer, and converting the amorphous aluminum oxide barrier layer into a single crystal aluminum oxide barrier layer through high temperature annealing.

8. The preparation method according to claim 7, characterized in that: The high temperature annealing treatment is performed at a temperature of 800°C to 2000°C.

9. The preparation method according to claim 3, characterized in that: The material of the first superconducting layer is selected from any one of superconducting metals except aluminum, and the forming of an aluminum oxide barrier layer on the first superconducting layer comprises: heating the substrate to a high temperature, depositing aluminum on the first superconducting layer under a high temperature state and simultaneously introducing oxygen to form a single crystal aluminum oxide barrier layer.

10. The preparation method according to claim 9, characterized in that: The substrate is heated to 700°C to 800°C, and the rate of depositing aluminum is to 11. The preparation method according to claim 1, characterized in that: The first etching window and the second etching window are perpendicular to each other, and the first superconducting layer and the second superconducting layer are formed by an oblique evaporation deposition process, and the evaporation directions are perpendicular to each other.

12. The preparation method according to claim 1, characterized in that: The preparation method further includes: separating the SOI mask and the substrate.

13. A Josephson junction obtained according to the preparation method according to any one of claims 1 to 12.

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